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The lifespan and the performance of flexible electronic devices and components are affected by the large accumulation of heat, and this problem must be addressed by thermally conductive polymer composite films. Therefore, the need for the development of high thermal conductivity nanocomposites has a strong role in various applications. In this article, the effect of different particle reinforcements such as single and hybrid form, coated and uncoated particles, and chemically treated particles on the thermal conductivity of various polymers are reviewed and the mechanism behind the improvement of the required properties are discussed. Furthermore, the role of manufacturing processes such as injection molding, compression molding, and 3D printing techniques in the production of high thermal conductivity polymer composites is detailed. Finally, the potential for future research is discussed, which can help researchers to work on the thermal properties enhancement for polymeric materials. [ABSTRACT FROM AUTHOR]

In the present paper, we report polymer composites based on phenolic resin filled with hexagonal boron nitride; hot compression molding coupled with solution-based mixing were used to manufacture the composites. The paper presents experimental results on the physical and physicochemical properties of the obtained composites: thermal stability in air and argon, dielectric constant and dielectric loss tangent, active electrical resistance, thermal conductivity (mean and anisotropy), and mechanical strength. It is shown that the proposed technique of composite manufacturing, including the application of high-process pressures, makes it possible to obtain materials with high anisotropy of thermal conductivity, extremely high-filler content, and excellent dielectric properties, all of which are very important for prospective highly efficient lightweight heatsink elements for electronic devices. Experimental values of thermal conductivity and dielectric constant were analyzed using known mathematical models. Experimental values for thermal conductivities (up to 18.5 W·m−1·K−1) of composites at filler loadings of 65–85 vol.% are significantly higher than published data for bulk boron nitride/polymer composites. [ABSTRACT FROM AUTHOR]

This study developed an in‐mold induction heating system for the injection compression molding process to overcome the problem of incomplete filling of microstructures caused by the formation of skin layers and residual stress caused by flow. Moldex3D software was used with the Taguchi method to optimize the molding parameters for both injection molding and injection compression molding, with the aim of reducing warpage and improving optical quality. The in‐mold induction heating system has extremely high heating efficiency. Experiments revealed that a time of only 8 s was required to inducted‐heat up the core to the glass transition temperature which keeps the melt under a good state of flow and allows a replication rate of 97%. In addition, the ICM process can effectively reduce the flow‐induced residual stress and improve the optical properties of the obtained samples. Finally, the illuminance of the product fabricated through ICM with induction heating for 10 s was 2.3 times higher than that of the product obtained through ICM without induction heating. Accordingly, the proposed induction heating system is feasible for use in ICM the rapid manufacturing of high‐quality optical products with microstructures. [ABSTRACT FROM AUTHOR]

The risk of spread of antibiotic-resistant bacteria leads to the growth of implant-associated infection, necessitating the large-scale fabrication of antibacterial materials. The successfully synthetic superhydrophobic and bactericidal materials without durable surfaces are easy to destroy and so difficult to use in a large-scale production in terms of manufacturing costs in performing experiments and processes. In this work, two kinds of microfeatured sieves dipped with high length-diameter ratio silicon carbide whiskers (SiCw) are used as templates for the fabrication of micropillared polypropylene (PP) surfaces embedded with nanospiked SiCw exposed in different postures of standing via a simple low-cost micro-compression molding method. The standing SiCw nanospikes endow the micropillared PP surfaces with a high contact angle (CA) of 153.9° decreased by less than 8° after a wear distance of 1500 mm, exhibiting robust antiwetting and antifriction properties. Further, the nanospiked micropillared PP surfaces exhibit extremely low adhesion and moderate antibacterial efficacy. The micro-/nanoconstructed PP surfaces is expected to approach towards large-scale industrial production for biomedical applications.

This study focuses on the development and characterization of pigeon pea stalk fiber (PSF) reinforced (10, 20, 30, and 40 wt.%) polylactic acid (PLA) sustainable composites. In particular, the tensile, compression, flexural, impact, shear strength, and hardness characteristics were studied as mechanical properties, while other characterizations included dynamic mechanical analysis, density, water absorption, crystallinity index, and morphology studies were also examined to get a more comprehensive understanding of these green composites. From the results of mechanical properties, the optimal particle loading was up to 30 wt.%, and these properties compare well with other green composites. They could be used as an alternative to natural fiber-based composites for secondary load-bearing applications in various sectors like indoor, packaging, furniture, automobile interiors, etc. The addition of PSFs (30 wt.%) into the PLA matrix increased the storage modulus by 28%. A significant improvement in crystallinity was also found in these green composites. In addition, all composites up to 30 wt.% PSFs exhibited good resistance to water absorption and had a maximum water intake of 5.25%. Morphological studies revealed good adhesion and distribution of PSFs in the PLA matrix.

The present work explores the tensile, flexural, impact strengths and sound absorption behavior of sisal and palm fiber-reinforced hybrid composites. The sisal and palm fibers were reinforced with epoxy resin through a compression molding technique to fabricate three hybrid composites with different weight ratios. The tensile, flexural, and impact tests were conducted as per ASTM standard for the three hybrid composites. The hybrid composite with 65% epoxy resin, 20% sisal fiber, and 15% palm fiber showed 0.63% high tensile strength, 22.62% high flexural strength, and 36.59% high impact strength compared to the other two hybrid composites. The SEM images of fractography revealed fiber to fracture, surface and fiber pull out, and also its dislocation of tightly packed fiber and matrix stickiness. The sound absorption behavior was accessed as per ASTM standard through an impedance test for the hybrid composites. The composite with 65% epoxy resin,20% sisal fiber, and 15% palm showed a high sound absorption coefficient at the frequency levels of 1600 Hz, 2000 Hz, 2500 Hz, 3150 Hz, and 4000 Hz due to the increased weight ratio of palm fiber. At a frequency level of 4000 Hz, the above hybrid composite showed a maximum sound absorption coefficient difference of 76.61% compared to the other two hybrid composites.

Natural fiber is a resource that is found abundantly and cost effective. It is decomposed easily and biodegradable. Natural fibers have a vital place in the industry and have the capability of replacing carbon fibers and conventional glass because of their biodegradability and eco-friendly characteristics. They have significant chemical, mechanical, and physical properties, which vary according to cellulose content in the fiber. Usually, with the increase in the cellulose content, the tensile strength of the fiber increases and with the increase in the non-cellulose content, the tensile strength of the fiber decreases. However, these chemical constituents are not the only factors that determine the tensile strength of the fiber. Certain other factors such as fiber age, maturity, location, and processing methods along with the source of the fiber also influence the tensile strength of the fiber. These properties of the natural fibers make it a vital component in engineering applications. Natural fibers meet the needs of humans and the manufacturing industry with their positive environmental effect and economic outlook. This review provides basic information and a segregated study on the mechanical properties of natural fibers, thus creating opportunities for future research and studies related to natural fiber–reinforced composites.

Synthetic fiber-reinforced composites are difficult to be disposed of after their intended use due to their non-biodegradable nature. Natural plant fibers, which are renewable and fully biodegradable, are, therefore, ideal alternatives that can replace synthetic fibers. In this research paper, the application of biodegradable Coccinia grandis fiber-reinforced epoxy bio composite is investigated. The randomly oriented Coccinia grandis fiber-reinforced bio composites were prepared by compression molding with 10%, 20%, 30%, 40%, and 50% fiber weight. Tensile, flexural, and impact tests were used to determine the composite’s mechanical properties, and Field Emission Scanning Electron Microscopy (FESEM) was used to understand the interfacial bonding. The obtained results revealed that 40% fiber weight could produce Coccinia grandis fiber-reinforced bio composite with the highest tensile strength, impact strength, and interfacial adhesion among all the prepared composites, whereas 50% fiber weight could make the bio composite with the highest flexural strength. The results show that the Coccinia grandis fiber-reinforced bio composites seem to have potential applications in automobile, construction, interiors, etc.

Purpose: In this research, nanocomposite of Ultra-High Molecular Weight Polyethylene (UHMWPE) reinforced with Silicon Carbide (SiC) nanoparticles was prepared and characterized in terms of chemical interaction, molecular structure, tensile strength, and dispersion state of nanoparticles in the UHMWPE matrix. Method: Nanocomposite of UHMWPE/SiC was prepared in gradient loadings (1.5, 3, 4.5 and 6 wt % of the SiC nanoparticles) by means of ultra-sonication mixing technique followed by compression molding. Results: Physicochemical interaction of the UHMWPE matrix and the SiC nanoparticles at filler/polymer interface was suggested by Fourier-transfer Infrared spectroscopy (FTIR) results. X-ray diffraction (XRD) approved that the incorporation of SiC in the UHMWPE matrix did not change the orthorhombic crystalline structure of neat UHMWPE. However, an increase in crystallinity of 14% was achieved with the 3 wt % of SiC. No significant change was observed in the average grain size comparing the pure UHMWPE to its nanocomposites. Conclusion: Enhancement in mechanical properties were achieved by 3 wt % SiC reinforced UHMWPE where young's modulus, tensile strength and strain at break increased by an average of 13%, 20% and 46% respectively. Scanning electron microscopy (SEM) approved good dispersion of SiC nanoparticles in UHMWPE matrix up to 3 wt%. [ABSTRACT FROM AUTHOR]

Shear and thermal processing can greatly influence nanoparticles' orientation and dispersion, affecting the nanocomposites' conductivity and mechanical properties. The synergistic effects of shear flow and Carbon nanotubes (CNTs) nucleating ability on the crystallization mechanisms have been proven. In this study, Polylactic acid/Carbon nanotubes (PLA/CNTs) nanocomposites were produced by three different molding methods: compression molding (CM), conventional injection molding (IM), and interval injection molding (IntM). Solid annealing at 80 °C for 4 h and pre-melt annealing at 120 °C for 3 h was applied to research the CNTs' nucleation effect and the crystallized volume exclusion effect on the electrical conductivity and mechanical properties. The volume exclusion effect only significantly impacts the oriented CNTs, causing the conductivity along the transverse direction to rise by about seven orders of magnitude. In addition, the tensile modulus of the nanocomposites decreases with the increased crystallinity, while the tensile strength and modulus decrease. [ABSTRACT FROM AUTHOR]

Fiber‐reinforced polymers are widely used in many applications where high specific strength and high specific stiffness are required. Biocomposites have replaced synthetic‐based fiber‐reinforced polymers as a preferred option due to their environmental friendliness, ease of supply, and affordability. Comparable strength synthetic‐fiber‐reinforced polymers and biocomposites both have lower specific weights. This study aims to characterize hybrid biocomposites produced from unidirectional prepregs made of flax/polypropylene fibers and nonwoven mats made of hemp/polypropylene fibers. Research has also been conducted on how the number of layers and the stacking sequence affect the mechanical performance of hybrid biocomposites. Three different designs of biocomposite plates have been produced using compression molding. They were then subjected to tensile, compressive, shear, bending, Charpy impact, and drop‐weight impact tests. According to the test results, it is found that each design has its own characteristics, and the characterized static and dynamic behaviors are very different from each other. Therefore, each biocomposite mentioned here may be a good candidate for engineering design based on the given engineering design criteria. [ABSTRACT FROM AUTHOR]

High‐performance thermoplastic composites based on semipregs of poly(phenylene sulfide) (PPS) reinforced with carbon fiber (CF) have been widely used in the aerospace industry due to their excellent mechanical properties and thermal stability. In this work, CF/PPS laminates were processed by hot compression molding. The processing parameters (pressure and temperature of processing) were investigated as well as the effect of the number of semipreg layers. The neat PPS matrix and CF/PPS semipreg were evaluated by rheological and thermal properties, respectively, to verify the best processing temperature for the CF/PPS composite laminates. The CF/PPS laminates obtained were inspected by ultrasound and differential scanning calorimetry analyses, and then the standardized specimens were prepared. The mechanical properties were evaluated by tensile test and interlaminar shear strength (ILSS) tests. Morphological characteristics of fracture surfaces also were analyzed by scanning electron microscopy. The ultrasound inspections showed differences among the processed laminates with the presence of defects mainly around the edges of samples. Based on ultrasound maps, the worst regions of laminates were discharged and not used to cut the specimens utilized in the mechanical characterization. Thermal, mechanical, and morphological analyses of the six laminates processed with different consolidation cycles did not show significant differences, showing good CF‐PPS matrix interface and similar results of crystallization (~23%), tensile strength (776–858 MPa), and ILSS (59–68 MPa). [ABSTRACT FROM AUTHOR]

Nanoscale recombination between carbon nanomaterials (CNs) and polymers has been proposed for a variety of industrial and scientific applications. Composite energetic materials consisting of CNs with novel laser ignition property and tunable combustion performance have attracted people's attention. Here, reported is the novel manufacturing process of uniform nitrocellulose (NC)/graphene oxide (GO) nanocomposite propellant and the micro‐structure, laser ignition and isovolumetric burning features of the propellants introduced by GO. The results of microstructure tests indicated that GO (0.25–2 wt%) was stripped and dispersed homogeneously and dense nanocomposite propellants were prepared successfully through water ultrasonic dispersion, twin‐screw mixture, as well as compression molding. The crystallization of NC was forbidden by doping GO, meanwhile, the thermal stability and thermal conductivity of the composite propellants increased slightly with the addition of GO. The results of laser ignition combustion experiments showed that GO was an efficient additive to shorten the ignition delay time from more than 2000–14 ms when 2 wt% of GO was doped, however, the combustion flame intensity was also weakened due to the addition of GO. The combustion tests in a closed bomb vessel were conducted, and the results showed that GO would not affect the stable combustion of NC at high combustion pressure, moreover, the burning rate and dynamic vivacity of the composite propellants decreased with the increase of GO content. [ABSTRACT FROM AUTHOR]

A compacted body was fabricated by pulverulent polyimide (PI) block copolymers using solid-like state compression molding (SCM) technique. Polymer heated to solid-like state, i.e. the high-elastic non-melting state above the glass transition temperature (T g) and well below melting temperature, could achieve plasticity due to dramatic decreases in elastic modulus. Tensile properties were taken as response values, and the results of single-factor experiments indicated that molding temperature was the dominant parameter on mechanical performances, followed by molding pressure and holding time. Within this context, the SCM process possesses a longer processing time window whereas the processing temperature is narrow. The manufacturing defects induced by inappropriate processing conditions also hurt the tribological performance of PIs. Particles in a solid-like state could coalesce tightly only by exerting both high temperature and pressure in the SCM process. Thermoforming mechanism examined by atomic-scale molecular dynamics simulation indicated that non-bonding interaction forces, especially van der Waals forces play a key role in fusing among polymeric particles. This study is devoted to establishing the interdependence of structure-formability-property for high-temperature polymers that are not melt processible. [ABSTRACT FROM AUTHOR]

Aiming at the shield muck in the mudstone stratum of Chengdu area, using cement as the solidification agent, fly ash as the active reinforcement material, and fine sand as the grading material, the mudstone muck unburned brick was prepared by pressing and molding, and was cured for 14 days in a concrete standard curing room. Using the compressive strength as an indicator, the effect of different mixing ratios on the compressive strength of the unburned brick was studied. The results show that the ratio of cement to fine sand has a positive linear relationship with the compressive strength of unburned bricks; Fly ash cannot be replaced with cement in an equal amount to improve compressive strength; When the mix design is 58% slag soil, 22% cement, 15% fine sand, and 5% fly ash, the compressive strength and softening coefficient of unburned bricks meet the MU15 grade requirements of JC/T422--2007 "Non fired Rubbish Gangue Bricks", and the appearance quality basically meets the specification re¬quirements. [ABSTRACT FROM AUTHOR]

Development in engineering material for total hip joint replacement obtained long life with minimum adverse effects produced in the human body. Due to their exceptional compatibility with tissue and bone, hydroxyapatite nanoparticles (n-HAp) have been employed as a filler material in polymer bio-composite for biomedical applications. This study used hydroxyapatite nanoparticles (n-HAp) as a filler material in ultra-high molecular weight polyethylene (UHMWPE) at four different wt.-%ages (0 wt.%, 5 wt.%, 1 wt.% 0 wt.% and 15 wt.%). This research aims to make UHMWPE/n-HAp bio-composites using heat-assisted compression molding and explore its mechanical characteristics such as flexural strength, compression strength, and impact strength. Microstructural analyses of n-HAp aggregation in UHMWPE using scanning electron microscopic (SEM) are done. The experimental results done by the authors suggest that bio-composite (with UHMWPE+10 wt.% n-HAp) show superior mechanical properties compared to other hip joint compositions. Here, 10 wt.% hydroxyapatite nanoparticles- reinforced in UHMWPE improve flexural strength and compression strength by 18.75% and 37.14%, respectively, at the expense of impact strength. Further, the GRA-PCA-based multi-objective optimization hybrid analysis also finds that bio-composite (UHMWPE+10 wt.% n-HAp) shows the highest mechanical strength with minimal surface roughness value. [ABSTRACT FROM AUTHOR]

This review focuses on the fabrication and mechanical characterization of fibrous composites for engineering applications. Fibrous composites are materials composed of two or more distinct phases, with fibers embedded in a matrix. The properties of these materials depend on the properties of both the fibers and the matrix, as well as the way they are combined and fabricated. The various fabrication methods, along with the process parameters, used to manufacture synthetic and natural fibrous composites for engineering applications, including hand lay-up, compression molding, resin transfer molding, additive manufacturing, etc., are discussed. The mechanical characterization of fibrous composites, including their strength, stiffness, and toughness of both synthetic and natural fibrous composites are discussed. The advantages and disadvantages of fiber reinforcement are discussed, along with their influence on the resulting mechanical characteristics of the composites. It can be observed that the mechanical properties of fibrous composites can be tailored by controlling various factors, such as the fiber orientation, fiber volume fraction, and matrix type. Although fibrous composites offer significant advantages, several challenges hinder their widespread use in engineering applications. These challenges include high manufacturing costs, limited design guidelines, and difficulties in predicting their mechanical behavior under various loading conditions. Therefore, despite their unique properties, these challenges must be overcome for fibrous composites to realize their full potential as high-performance materials. [ABSTRACT FROM AUTHOR]

Copyright of Basic Sciences Journal of Textile Universities / Fangzhi Gaoxiao Jichu Kexue Xuebao is the property of Basic Sciences Journal of Textile Universities and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study aimed to determine the influence of shear stress during real-life industrial processes such as compression molding and injection molding to different cavities on the crystallization of the isotactic polypropylene nucleated with a novel silsesquioxane-based β-nucleating agent. Octakis(N2,N6-dicyclohexyl-4-(3-(dimethylsiloxy)propyl)naphthalene-2,6-dicarboxamido)octasilsesquioxane (SF-B01) is a highly effective nucleating agent (NA) based on the hybrid organic-inorganic silsesquioxane cage. The samples containing various amounts of the silsesquioxane-based and commercial iPP β-nucleants (0.01–0.5 wt%) were prepared by compression molding and injection molding, including forming in the cavities with different thicknesses. The study of the thermal properties, morphology, and mechanical properties of iPP samples allows for obtaining comprehensive information about the efficiency of silsesquioxane-based NA in shearing conditions during the forming. As a reference sample, iPP nucleated by commercial β-NA (namely N2,N6-dicyclohexylnaphthalene-2,6-dicarboxamide, NU-100) was used. The static tensile test assessed the mechanical properties of pure and nucleated iPP samples formed in different shearing conditions. Variations of the β-nucleation efficiency of the silsesquioxane-based and commercial nucleating agents caused by shear forces accompanying the crystallization process during forming were evaluated by differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS). The investigations of changes in the mechanism of interactions between silsesquioxane and commercial nucleating agents were supplemented by rheological analysis of crystallization. It was found that despite the differences in the chemical structure and solubility of the two nucleating agents, they influence the formation of the hexagonal iPP phase in a similar way, taking into consideration the shearing and cooling conditions. [ABSTRACT FROM AUTHOR]

The orientation and dispersion of nanoparticles can greatly influence the conductivity and mechanical properties of nanocomposites. In this study, the Polypropylene/ Carbon Nanotubes (PP/CNTs) nanocomposites were produced using three different molding methods, i.e., compression molding (CM), conventional injection molding (IM), and interval injection molding (IntM). Various CNTs content and shear conditions give CNTs different dispersion and orientation states. Then, three electrical percolation thresholds (4 wt.% CM, 6 wt.% IM, and 9 wt.% IntM) were obtained by various CNTs dispersion and orientations. Agglomerate dispersion (Adis), agglomerate orientation (Aori), and molecular orientation (Mori) are used to quantify the CNTs dispersion and orientation degree. IntM uses high shear to break the agglomerates and promote the Aori, Mori, and Adis. Large Aori and Mori can create a path along the flow direction, which lead to an electrical anisotropy of nearly six orders of magnitude in the flow and transverse direction. On the other hand, when CM and IM samples already build the conductive network, IntM can triple the Adis and destroy the network. Moreover, mechanical properties are also been discussed, such as the increase in tensile strength with Aori and Mori but showing independence with Adis. This paper proves that the high dispersion of CNTs agglomerate goes against forming a conductivity network. At the same time, the increased orientation of CNTs causes the electric current to flow only in the orientation direction. It helps to prepare PP/CNTs nanocomposites on demand by understanding the influence of CNTs dispersion and orientation on mechanical and electrical properties. [ABSTRACT FROM AUTHOR]

The industry of composite materials has grown in the last decade due to the requirements of light and high strength materials. The increasing demands of materials have to comply with low greenhouse gases emissions (GHG) as stated by international agreements, and reusing and recycling is a path to minimize the environmental impacts. This research aims to analyze the variables that influence the tensile strength of discontinuous laminate composites of short fibers from cutting operation process which is in the context of reusing. These variables were part of the equation of force equilibrium that involves shear strength failure criterium approach. In addition, the failure analysis and the results were compared with the literature data. Composites of glass fiber fabric wastes with varied fiber length (defined as short fiber) was designed and tested using polyethylene terephthalate (PET) as a matrix. A total of three different laminates with different fabric lengths were evaluated, totaling of seven interruptions/discontinuities along the thickness of each laminate. An image analysis of the failure sequence aided to assess the laminate behavior by comparing the stress–strain curve shape and they were in agreement with the results provided by the developed equation. The results show that this equation enables to identify the variables that influence the laminate strength: yielding stress; interface strength; stress concentration; and peel stress. In this particular research, the weak interface contributed to the low tensile strength of the laminates, and showed less influence of the "critical length," limiting the micromechanical approach that considered a fiber filament. [ABSTRACT FROM AUTHOR]

The intention of this research is to recapitulate the two different fillers like E glass fiber and nanocarbon fiber, which were utilized to fabricate the polymer matrix composites by the assistance of epoxy resin. The mechanical compression molding was influenced to produce the polymer-based nanocomposites under consideration of optimal process parameters. There are three different weight fractions E glass fiber (40%, 45%, and 50%), nanocarbon fiber (10%, 15%, and 20%), and epoxy concentrations (30%, 40%, and 50%), respectively, that were used to produce the polymer matrix composites. Those processing parameters were designed by the L9 Taguchi with DOE technique to conduct the mechanical tests like tensile strength and hardness properties. The signal-to-noise ratios were successfully accomplished to identify optimal process parameters for improving the individual responses. The ANOVA and interaction was additional supports to enhance the mechanical properties. The scanning electron microscope was used to examine the fracture surfaces at the tensile fracture specimens with optimal conditions. Moreover, the maximum mechanical characteristics were attained by the increasing of nanocarbon fiber in the processed polymer matrix composites. [ABSTRACT FROM AUTHOR]

Compression molding is a manufacturing technique that is frequently and widely utilized in fabricating composites. However, bast fiber reinforced composites (BFRC) with good quality and high performance by compression molding are quite challenging because it is complicated to find suitable process parameters. Previous works on improving the mechanical performance of compression molded BFRCs normally considered the influence of a single process parameter and ignored the mutual effects of process parameters. To enhance the mechanical qualities of BFRCs and enlarge their applications, this paper studied the synergistic effects of two molding process parameters on the mechanical characteristics of jute reinforced polypropylene composites (jute/PP) from contour and surface plots through response surface methodology (RSM). The significance of each molding process factor on the mechanical behaviors of jute/PP was investigated by conducting the analysis of variance (ANOVA). Multi-parameter co-optimization achieved the optimal mechanical performance of molded jute/PP at 186.8°C, 5.6 MPa, and 10.1 min, which was consistent with experimental findings. This suggests that response surface equations obtained from RSM can accurately characterize the relationships between mechanical characteristics and molding parameters of jute/PP. The RSM provides a useful and reliable way to find the optimal process parameters for better mechanical behaviors. [ABSTRACT FROM AUTHOR]

The present work explored alkali–treated coconut petiole fibers (ACPFs) characterization and the effect of fiber loadings on the mechanical properties of poly (lactic acid) (PLA)/ACPF composites for the first time. The physical, mechanical, and interfacial properties, as well as the morphology of the ACPFs were reported. It was found that ACPFs with a density of 0.92 g/cm3 have average tensile strength and tensile modulus equal to 355.77 MPa and 5212.36 MPa. The interfacial strength between ACPFs and PLA was high (14.06 MPa), attributed to the micro–sized holes on the fibers, as established from SEM micrographs. Then composites with varying fiber loadings were fabricated by melt–blending and compression molding. The mechanical (tensile, flexural, and impact) performance of composites was reported. Based on the high interfacial strength between fibers and PLA and the unique "spiral" structure of fibers, the composites reached a high impact strength of 8.2 kJ/m2 and flexural modulus of 6959.70 MPa at 50 wt.%, representing 150% and 50% improvement relative to pure PLA. [ABSTRACT FROM AUTHOR]

Composites based on an L-rich poly(lactic acid) (PLLA) and MCM-41, either neat or modified with a silver (MCM-41@Ag), are achieved by solvent casting, being next processed by compression molding. Ag is mainly embedded as nanowires within the hybrid MCM-41@Ag particles, enabling its antimicrobial character. In these composites, the PLLA thermal stability, nucleation efficiency, and mechanical response are dependent on the MCM-41 nature and, to a lesser extent, on its content. Thus, differences in transitions of the PLLA matrix are noticed during cooling at 10 °C/min and in the subsequent heating when composites with neat or modified MCM-41 are compared. A very remarkable nucleation effect is played by pristine MCM-41, being inferior when MCM-41@Ag is incorporated into the PLLA. Wide angle X-ray scattering (WAXS) measurements using synchrotron radiation and performed under variable-temperature conditions in the composites containing MCM-41@Ag indicate that during cold crystallization, the disordered α′ polymorph is initially formed, but it rapidly transforms into ordered α crystals. A long spacing peak, clearly seen in pure PLLA, appears as a small shoulder in PLLAMCM@Ag4 and is undetectable in PLLAMCM@Ag9 and PLLAMCM@Ag20. Furthermore, an increase in MH with the silica content is found in the two sets of composites, the higher MH values being observed in the family of PLLA and MCM-41@Ag. Finally, remarkable antimicrobial features are noticeable in the composites with MCM-41@Ag since this modified silica transfers its biocidal characteristics into the PLLA composites. [ABSTRACT FROM AUTHOR]

Natural fibers have been extensively used for many decades. This work investigates the suitability of Borassus flabellifer sprout fiber, a new class of fibers, as reinforcement in polymer matrix composites. Borassus flabellifer sprouts are also called palm sprouts. The fibers were extracted by the water retting method and treated with 5% sodium hydroxide (NaOH) to remove the impurities present in the fiber to achieve better bonding with the matrix. Scanning electron microscopic images of raw and alkali treated Borassus sprout fibers were studied. Composite specimens were made with 20, 25, 30 and 35 volume % of treated and untreated palm sprout fibers, respectively, in a polyester matrix by the hand layup technique and by the compression molding technique. Tensile strength, flexural strength, compression strength, impact strength, hardness and water absorption of sample specimens were determined. Experimental results showed that the composite specimens with 35 volume % of treated palm sprout fibers as reinforcement performed better in all aspects. They have 30.34% higher tensile strength, 34.47% higher flexural strength, 3.14% increased compression strength and 15.56% better impact strength and 7.6% less water absorption than the composite plates reinforced with 35% untreated palm sprout fibers. Thus, the composites showed adequate mechanical properties to be considered for specific applications. [ABSTRACT FROM AUTHOR]

Copyright of Plastics Science & Technology / Suliao Ke-Ji is the property of Plastics Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As the surface acoustic wave (SAW) filters incline to ultrafine, the failures resulting from the wafer molding process have become increasingly prominent. A methodology for coupling the mechanisms of die fly and die shift for the SAW filter miniatured with 737 μ m × 517 μ m × 200 μ m is developed for the trade-off between reliability and yields. In terms of die fly and die shift, the former occurs before the epoxy molding compound (EMC) is cured in the temperature rise period, while the latter occurs in the cooling stage after being cured. The die fly is induced by the fluid flow force in the high-temperature stage of heat compression, which is fatal for the scrap. Followed by the cooling stage, the CTE (coefficient of thermal expansion) misalignment between the die and epoxy molding compound (EMC) seriously affects the die shift and the following lithography process yields. The debonding critical energy in the mixed mode is employed to avert the die fly. Then, the die fly can be shunned by fine-tuning the die thickness, die layout, and EMC layout. A methodology to measure die shift was conducted, by which a total of 47,568 dies were embedded using compression molding. The mechanical error of the mounter and the die shift law are comprehensively leveraged, indicating that the die shift can be controlled within 50 μ m for 8-inch wafer-level packaging. [ABSTRACT FROM AUTHOR]

Most lenses on the market can be made by injection molding. However, defects such as weld lines and residual stress are often generated during the production of concave products. Compression molding eliminates these problems, and the cost of the required molding machinery is relatively low compared to other processes. The process can also be highly automated, which is essential for plastic manufacturing. This study proposes an innovative mold for compression molding for a double-concave lens. There is no requirement for angular alignment because the lens is axisymmetric. A compact compression mold without leader pins is created. Parameter optimization for the powder and granular PMMA is optimized using the Taguchi method. The significant compression molding parameters are the pre-pressing period, the pressing temperature, the pressing force, and the pressing period. The surface profiles of finished products are measured, and a factor response analysis is used to determine the effect of various parameters on the finished product. The pressing force was shown to be the most significant factor for powder. However, granules need a long enough pre-pressing time because the gap widens. A confirmation experiment was conducted with the optimized parameters. The profile of the compressed double-concave lens is measured and compared with the mold insert. Powder PMMA is more suitable for compression molding than granular PMMA. However, regardless of the material type, the compression-molded double-concave lens is 96% replicable or more. [ABSTRACT FROM AUTHOR]

The heat accumulation caused by the high power consumption of continuously upgrading electronic devices puts forward more requirements for the adaptability and durability of the flame retardant materials. Herein, inspired by the soil reinforcement effect of the shelter forest roots nearby the river and shoal, a superhydrophobic flame‐retardant ethylene‐vinyl acetate (EVA)/aluminum trihydroxide (ATH) composite with root‐soil interlocked micro/nanostructure (MEA/PGCC) is prepared by combining the micro‐extrusion compression molding and spray coating. The homogeneously dispersed ATH and the EVA with sufficient mechanical strength provide durability for the long‐term work of the MEA/PGCC composite. The root‐soil interlocked micro/nanostructure provides robust superhydrophobicity with a water contact angle of 156 ± 1.0° and a rolling angle of 4 ± 1.0° for the MEA/PGCC composite which is beneficial to improve acid and alkali tolerance, thermic resistance, and de‐icing performance. The synergism of interface and surface function prominently improves the flame retardancy of the MEA/PGCC composite, which presents a limit oxygen index of 42%, and remarkable reduction in peak heat release rate of 64%, total heat release of 23%, and peak smoke production rate of 47%. The proposed method is a promising candidate for the mass production and practical application of the superhydrophobic flame retardant composite. [ABSTRACT FROM AUTHOR]

With the growing demand for insulation parts in extreme service environments, such as nuclear power, aviation, and other related fields, fiberglass-reinforced silicone resin (FRSR) has become a popular choice due to its exceptional physical and chemical properties in high-temperature and electromagnetic working environments. To enhance the performance of FRSR molded parts that can adapt to more demanding extreme environments, the oven postcuring process parameters on thermal stability and mechanical properties of the bobbin were investigated. The curing behavior of FRSR was analyzed by using thermogravimetric analysis (TGA) and the differential scanning calorimetry (DSC) method, and the bobbins were manufactured based on the testing results. Subsequently, the bobbins were oven postcured at different conditions, and the heat resistance and mechanical properties were analyzed by TGA and tensile tests. The results revealed that the tensile strength of the bobbin increased by 122%, and the weight loss decreased by 0.79% at 350 °C after baking at 175 °C for 24 h. The optimal process parameters for producing bobbins to meet the criteria of nuclear installations were determined to be a molding temperature of 120 °C, molding pressure of 50 MPa, pressure holding time of 3 min, oven postcuring temperature of 175 °C, and postcuring time of 24 h. The molded products have passed the thermal aging performance test of nuclear power units. [ABSTRACT FROM AUTHOR]

Polylactide (PLA) polymer, polypropylene (PP) polymer, and a PLA/PP (70:30 wt%) blend, with liquid natural rubber−graft−methy methacrylate (LNR−g−MMA) of 0.0, 2.5, 5.0, and 10.0 phr as compatibilizers, were prepared by internal mixing and compression molding. The effect of LNR-g-MMA content on the morphology, mechanical properties, water absorption, thermal degradation, and a lifetime of blends based on PLA and PP was investigated. Scanning electron microscopy (SEM) revealed that the PLA/PP blend underwent phase separation, and the presence of LNR−g−MMA in the PLA/PP blend showed a more homogenized and refined blend morphology. Hence, the addition of LNR−g−MMA was used as a compatibilizer to induce miscibility in the PLA/PP blend. The values of tensile strength, elongation at break, and impact strength of the polymer blends increased, whereas water absorption values decreased with increased LNR−g−MMA content. Thermal degradation kinetics was studied over a temperature range of 50–800 °C with multiple heating rates. The results demonstrated that the thermal stability of blends without LNR-g-MMA was greater than that of blends with LNR−g−MMA and that the thermal stability decreased with increasing LNR−g−MMA content. The activation energy (Ea) was calculated by using the Kissinger–Akahira–Sunose method. The Ea value of PLA was much lower than that of PP, and incorporating PP in the PLA matrix increased the Ea. The addition of LNR−g−MMA to the PLA/PP blend decreased the Ea. The lifetime of PLA/PP blends was reduced with the addition of LNR−g−MMA. [ABSTRACT FROM AUTHOR]

Nowadays, companies and researchers are concerned about the negative consequences of using synthetic polymers and direct their efforts to create new alternatives such as biocomposites. This study investigated the effect of biobased SiO 2 on the properties of poly(L-lactic acid)/SiO 2 (PLLA/SiO 2 ) and poly(L-lactic acid)/SiO 2 /poly(ethylene glycol) (PLLA/SiO 2 /PEG) composites. The SiO 2 was obtained from rice husk incineration and mixed with PLLA at various concentrations (5, 10, and 15 wt.%) via melt extrusion before compression molding. Furthermore, PLLA/SiO 2 /PEG composites with various PEG concentrations (0, 3, 5, and 10 wt.%) with 10 wt.% SiO 2 were produced. The sample morphology was studied by scanning electron microscopy (SEM) to analyze the dispersion/adhesion of SiO 2 in the polymer matrix and differential scanning calorimetry (DSC) was used under isothermal and non-isothermal conditions to study the thermal properties of the samples, which was complemented by thermal stability study using thermogravimetric analysis (TGA). Rheological analysis was performed to investigate the viscoelastic behavior of the composites in the melt state. At the same time, tensile mechanical properties were obtained at room temperature to determine their properties in the solid state. DSC and X-ray diffraction analysis (XRD) were combined to determine the crystalline state of the samples. Finally, gas permeation measurements were performed using a variable pressure (constant volume) method to analyze the permeability of different gases (CO 2 , CH 4 , O 2 , and H 2 ). The results showed that SiO 2 decreased the PLLA chain mobility, slowing the crystallization process and lowering the gas permeability while increasing Young's modulus, thermal stability, and viscosity. However, PEG addition increased the crystallization rate compared to the neat PLLA (+40%), and its elongation at break (+26%), leading to more flexible/ductile samples. Due to improved silica dispersion and PLLA chain mobility, the material's viscosity and gas permeability (+50%) were also improved with PEG addition. This research uses material considered as waste to improve the properties of PLA, obtaining a material with the potential to be used for packaging. [ABSTRACT FROM AUTHOR]

Purpose: This study compared the dimensional changes between computer‐aided design and computer‐aided manufacturing (CAD‐CAM) milled complete denture bases (CDBs) and three‐dimensional (3D) printed CDBs. Materials and methods: One maxillary completely edentulous stone model was fabricated with three reference points at the incisive papilla, right molar, and left molar areas marked as X, Y, and Z, respectively. It was scanned to produce a standard tessellation language (STL) file, which was imported to a metal milling machine software to produce the metal model. This metal model was used to fabricate 30 CDBs for analysis. The CDBs were divided into three groups (n = 10 each) according to the fabrication method used as follows: Group 1, CAD‐CAM milled CDBs; Group 2, 3D printed CDBs; and Group 3, conventional compression molded CDBs. The CDBs of all groups were scanned after fabrication, and the dimensional changes in each were evaluated by two methods. The first was the two‐dimensional evaluation method that involved linear measurement of the distances between the reference points (X‐Y, X‐Z, and Y‐Z) of the scanned reference cast and dentures. The second method was the 3D evaluation method that involved the superimposition of the STL files of the dentures on the STL file of the reference cast. Data were calculated and were statistically analyzed using one‐way analysis of variance and Tukey's pairwise post hoc tests. Results: There was a significant difference in the dimensional accuracy between the CAD‐CAM milled, 3D printed, and conventional compression molded CDBs (p < 0.05). Conclusion: The dimensional accuracy of the CAD‐CAM milling system in complete denture fabrication is superior to that of the compression molding and 3D printing systems. [ABSTRACT FROM AUTHOR]

There is a rising demand for packaged food in the twenty-first century. Fresh food products are prone to spoilage, moisture loss, physical damage, microbial decay, and biochemical changes. These are the principal reasons for the quality loss and decreased shelf-life, necessitating the usage of packing films. The packaging films are currently made from different synthetic polymers including polypropylene, polyethylene, and other types of artificial polymers. However, it would be better to use soy protein as a justifiable antibacterial film in packaging. Soy Protein Isolate (SPI) is cheap and widely available for different uses in the food industry. Soy-based films made from renewable resources are a better option than synthetic-based films. They have strong mechanical characteristics and they are transparent in the presence of other additions like acids, nanoparticles, and natural substances. Furthermore, the production technique (compression molding and solution casting) for SPI film in the absence or presence of additives is simple and economically beneficial. Chemicals derived from plants such as essential oils and plant extracts are also useful to add antioxidant and antibacterial properties to films and coatings resulting in SPI. This paper was focused on the application of soy protein-based coatings and films, as well as coatings incorporated with nano-materials (nano-bioactive chemicals or essential oils), in food models to extend shelf life, as reported in recent years. [ABSTRACT FROM AUTHOR]

Double‐sided microlens arrays (MLAs) are the key optical components of the optical component. To enhance microlens fabrication productivity, a wafer‐level, double‐sided MLA was designed and fabricated using injection compression molding (ICM). First, the Moldex3D simulation analysis results show that the design of the disc mold saves material and representation time than the multi‐cavity mold. The 4‐inch disc mold with a 4 × 4 double‐sided MLA of two inserts was used to do the study. The L9 orthogonal Taguchi method was employed to find the best combination of molding parameters. For molding experiments, 2 mold inserts with 4 × 4 convex and concave lens arrays were machined by the ultraprecision diamond turning. They were mounted into molds in one of two locations, either close to the gate or far from the gate. The molding experiment results confirmed that the ICM‐molded MLA was better than the injection molding (IM)‐molded one, with higher precision and lower residual stress. The results were similar to the simulations. The ICM molded MLA has a focal length of 2.549 mm and a spot size of 50 μm and the total deviation percentage is less than 1%. This study proves the feasibility of fabricating a wafer‐level, double‐sided MLA disc using ICM. [ABSTRACT FROM AUTHOR]

The compression molding performance of a substrate block has a significant effect on the quality and stability of mechanical transplanting. The physical experiment and DEM simulation were combined to evaluate the compression molding behavior of substrate block in this study. A calibration procedure of DEM parameters of peat particles was proposed at first. Then, the above parameters were brought into the contact model of the compression system–particles, and the effect of the loading speed on the compression behavior of the peat substrate block was investigated. The compressive force–displacement curves of the simulated and measured tests were all contained in the initial linear stage and non-linear stiffing stage. The particle number of central sections was higher than side section, and the variable coefficient was greater at higher loading speed. The substrate blocks all expanded after demolding. The higher the loading speed, the greater the expansion in the height's direction, and the easier it was for cracks to be generated near the bottom. This study will provide a reference for the design of substrate block forming machines. [ABSTRACT FROM AUTHOR]

This study investigates the effects of microcylindrical pillar geometry on surface wettability and ice nucleation time. The cylindrical micropillars were designed and then fabricated on silicone rubber surfaces by micromachining to create a template, followed by direct replication using a compression molding method. This approach offers an efficient, nontoxic, and low-cost means of producing micro-nanoscale roughness on surfaces. We tested the wetting (i.e., contact angle and contact angle hysteresis) and anti-icing (i.e., ice nucleation time) properties of the patterned silicone rubber surfaces having different combinations of pillar diameter and interpillar spacing. According to our experimental results for a limited range of pillar diameters (80 and 110 μm) and center to center spacing (pitch; 125–300 μm), decreasing the diameter and increasing the space of micro-cylindrical pillars may result in the Cassie wetting until a threshold value. Beyond this pillar diameter/pitch threshold, Wenzel wetting occurred. Surfaces characterized by pillars of different diameter and pitch also increased the freezing delay by reducing the area of ice–substrate contact and the heat transfer between the water droplet and the surface. We demonstrate that the properties of superhydrophobic and anti-icing surfaces can be controlled by altering the geometry of micropillars across the surface.

In this study, isotropic coke and coal tar pitch were subjected to compression molding while varying the compression pressure and holding time. As a result, carbon blocks were fabricated, and their mechanical properties and microstructure were analyzed, with respect to applied pressure and holding time. The compression pressure was set to 70, 100 and 130 MPa, while the holding time was set to 1, 2 and 3 min. Overall, with an increase in compression pressure, bulk density increased while porosity decreased. Increased compression pressure also led to enhanced mechanical and electrical properties. Microstructural analysis confirmed that, after compression molding granules that were larger than existing kneaded particles appeared. The formation of granules is attributed to the tendency of kneaded particles to connect and coalesce with each other under applied pressure during the compression molding process. As the compression pressure increased, the proportion of granules in the microstructure increased while the size of pores decreased. This phenomenon can be attributed to kneaded particles coming closer to each other under applied pressure. At a compression pressure of 130 MPa, both bulk density and porosity increased with a longer holding time. Some pores existed within granules, while others protruded out of granules, thereby forming long channels of connected pores around them. This microstructural change was considered to result in degraded mechanical and electrical properties.

Abstract Polystyrene (PS)‐based and carbon fabric‐reinforced polymers (CFRPs) containing elastomer were prepared using the compression molding technique. PS was also reinforced with two types of carbon nanotubes (CNTs), as received and modified with a silane‐coupling agent. Nanocomposites were fabricated with two different methods, masterbatch dilution, and direct melt mixing. The effect of the nanocomposite preparation technique on the mechanical properties, electrical resistivity, and shape memory behavior of the multilayer composites was investigated. The tensile strength and tensile modulus of the multilayer composite containing CNTs modified with silane coupling agent, and prepared with masterbatch dilution method, increased by 33% and 34%, respectively, compared with the composites prepared with melt mixing. With the masterbatch dilution technique, the electrical resistivity was lower, and slightly increased with surface modification of CNTs. In both preparation techniques, the possible combined effect of CNTs and CF on the thermal and electrical conductivity of the composites led to 100% shape recovery lower than 30 s with electrically actuated bending test.

Different amounts of carbon nanotubes (CNT) have been incorporated in materials based on poly(vinylidene fluoride) (PVDF) by solvent blending followed by their further precipitation. Final processing was performed by compression molding. The morphological aspects and crystalline characteristics have been examined, additionally exploring in these nanocomposites the common routes described in the pristine PVDF to induce the β polymorph. This polar β phase has been found to be promoted by the simple inclusion of CNT. Therefore, coexistence of the α and β lattices occurs for the analyzed materials. The real-time variable-temperature X-ray diffraction measurements with synchrotron radiation at a wide angle have undoubtedly allowed us to observe the presence of the two polymorphs and determine the melting temperature of both crystalline modifications. Furthermore, the CNT plays a nucleating role in the PVDF crystallization, and also acts as reinforcement, increasing the stiffness of the nanocomposites. Moreover, the mobility within the amorphous and crystalline PVDF regions is found to change with the CNT content. Finally, the presence of CNT leads to a very remarkable increase in the conductivity parameter, in such a way that the transition from insulator to electrical conductor is reached in these nanocomposites at a percolation threshold ranging from 1 to 2 wt.%, leading to the excellent value of conductivity of 0.05 S/cm in the material with the highest content in CNT (8 wt.%). [ABSTRACT FROM AUTHOR]

Dielectric elastomer (DE) as an important electro‐active polymer (EAP), is capable of providing a large elastic deformation under an external electric field. However, the excellent electro‐actuated performance is usually obtained under high electric fields, which greatly limits the practical application range of DE, especially in the field of in vivo organisms. Thus, it is essential to make a reasonable structural regulation to achieve an effectively improved electro‐actuation of DE materials under low driving electric fields. Herein, a typical BaTiO3@TiO2 entirely‐inorganic core‐shell construction was prepared through the micro‐emulsion method. Meanwhile, a series of polydimethylsiloxane (PDMS)‐based DE composites incorporated with different fractions of BaTiO3@TiO2 were synthesized by solution blending and compression molding. The BaTiO3@TiO2 core‐shell construction endows DE composites with an enlarged heterogeneous interface and enhanced interfacial polarization synchronously, which is also benefit to maintain the flexibility of DE materials. The buffer effect offered by TiO2 shell is helpful to alleviate the local electric field concentration at the fillers‐matrix interface in DE when being withstood an exponentially‐growing electric field. Specifically, the maximum electro‐actuated strain of 21% under a low electric field (40 V·μm−1) is obtained from the DE composite filled with 4 wt% BaTiO3@TiO2, which is 290% higher than that of pristine PDMS (5.38% at 40 V·μm−1). It is shown that the well‐designed inorganic core‐shell construction can effectively improve the electromechanical conversion capability of DE composites. This study provides a promising approach to obtain an optimized electro‐actuation under low electric fields. [ABSTRACT FROM AUTHOR]

The controllability of the microstructure of a compressed hierarchical building block is essential for optimizing a variety of performance parameters, such as thermal management. However, owing to the strong orientation effect during compression molding, optimizing the alignment of materials perpendicular to the direction of pressure is challenging. Herein, to illustrate the effect of the ordered microstructure on heat dissipation, thermally conductive carbon-based materials are fabricated by tailoring dense, orientation-tunable, and interleaved structures. Vertically aligned carbon nanotube arrays (VACNTs) interconnected with graphene films (GF) are prepared as a 3D core-ordered material to fabricate compressed building blocks of O-VA-GF and S-VA-GF. Leveraging the densified interleaved structure offered by VACNTs, the hierarchical O-VA-GF achieves excellent through-plane (41.7 W m-1 K-1) and in-plane (397.9 W m-1 K-1) thermal conductivities, outperforming similar composites of S-VA-GF (through-plane: 10.3 W m-1K-1 and in-plane: 240.9 W m-1 K-1) with horizontally collapsed carbon nanotubes. As heat dissipation plates, these orderly assembled composites yield a 144% and 44% enhancement in the cooling coefficient compared with conventional Si3N4 for cooling high-power light-emitting diode chips. [ABSTRACT FROM AUTHOR]

The fused filament fabrication (FFF) process is one of the most widely used additive manufacturing (AM) methods in producing parts with relatively complex geometry due to its low cost and high capability. Using this blend along with the 3D printing method to make complex shapes can have a high potential in medical applications such as stents, so the goal of the following study is to investigate the shape memory properties of Polylactic Acid/Thermoplastic polyurethane (PLA/TPU) blend. The printed samples with 100/0, 80/20, and 60/40 PLA/TPU composition ratios were comprehensively evaluated based on their structural, thermal, and shape memory properties. A differential scanning calorimetry (DSC) test was conducted to determine the glass transition temperatures and crystallization temperature zone of the blends. A full factorial design of experiments was employed to investigate the effect of three variables called composition ratio, printing angle, and filling percentage on shape memory behavior. Using the three-point flexural test, the shape memory behavior of printed samples with composition ratios 100/0,80/20, 60/40, and filling percentages of 50, 75, and 100%, along with printing angles of zero, ±45, and 90°, was evaluated and measured. The annealing process increased the force required to change the shape and crystallization percentage, such that not being processed, no crystals were observed in the X-ray diffraction (XRD) analysis of the samples, while after being annealed, up to 38% of the crystals were formed. Increasing the percentage of TPU and temperature led to the softening of the samples, reducing the strength and elastic modulus, as well. Enhancing the percentage of TPU also decreases the hydrophilic properties of the samples. The results showed that the best shape memory performance is related to the 20 weight percentage of TPU composition, and the maximum recovery force ratio belongs to the sample with such a composition, zero printing angles, and 75% filling percentage, which equals 81.56%, while it equals 74% using compression molding (CM) in all three production blends. [ABSTRACT FROM AUTHOR]

In this work, the long-term creep response of high-performance carbon fiber PEKK (CF/PEKK) composites was evaluated by performing extrapolated short-term flexural creep tests at various temperatures. The time-temperature superposition principle (TTSP) with vertical as well as horizontal shifting was used to generate master curves at reference temperatures of 120°C. Satin weave-based CF/PEKK prepregs were used to manufacture eight-layer composites via compression molding, with three different stacking sequences: (a) zero-direction [0]8 (b) cross-ply [0, 90]4 and (c) quasi-isotropic [90, −45, 45, 0]2 s. The flexural properties under three-point bending arrangement in a universal testing machine were also evaluated. A dynamic mechanical thermal analyzer (DMTA) in three-point bending mode was used to evaluate the temperature-dependent viscoelastic properties of the three types of composites. The creep and creep-recovery behavior was evaluated at 40°C, 80°C, 120°C, 160°C and 200°C. To construct a master curve, extrapolated short-term isothermal creep tests were performed from 120°C to 180°C at the intervals of 10°C. The predicted master curve represents the creep behavior of composites over more than 10 years. It was shown that the quasi-isotropic CF/PEKK composites exhibited 27% and 12% higher creep resistance at 120°C as compared to zero-direction and cross-ply laminates, respectively. Higher flexural modulus (23%) and flexural strengths (33%) were also exhibited by the quasi-isotropic CF/PEKK composites. The final thickness of quasi-isotropic laminates was 8% lower than the 0o laminates. After analyzing the cross-sections of the composites, it was proposed that the superior mechanical properties of the quasi-isotropic laminates could be due to enhanced nesting between neighboring prepreg layers during the compression molding process, which resulted in closer packing of the fibers. It has been shown that the prepreg stacking sequence could affect the creep behavior and flexural properties of the compression-molded CF/PEKK composites. [ABSTRACT FROM AUTHOR]

Hot-melt extrusion (HME) is used for the production of solid protein formulations mainly for two reasons: increased protein stability in solid state and/or long-term release systems (e.g., protein-loaded implants). However, HME requires considerable amounts of material even at small-scale (>2 g batch size). In this study, we introduced vacuum compression molding (VCM) as a predictive screening tool of protein stability for potential HME processing. The focus was to identify appropriate polymeric matrices prior to extrusion and evaluation of protein stability after thermal stress using only a few milligrams of protein. The protein stability of lysozyme, BSA, and human insulin embedded in PEG 20,000, PLGA, or EVA by VCM was investigated by DSC, FT-IR, and SEC. The results from the protein-loaded discs provided important insights into the solid-state stabilizing mechanisms of protein candidates. We demonstrated the successful application of VCM for a set of proteins and polymers, showing, in particular, a high potential for EVA as a polymeric matrix for solid-state stabilization of proteins and the production of extended-release dosage forms. Stable protein-polymer mixtures with sufficient protein stability after VCM could be then introduced to a combination of thermal and shear stress by HME and further investigated with regard to their process-related protein stability. [ABSTRACT FROM AUTHOR]

This study proposes a novel process that integrates the molding and patterning of solid-state polymers with the force generated from the volume expansion of the microcellular-foaming process (MCP) and the softening of solid-state polymers due to gas adsorption. The batch-foaming process, which is one of the MCPs, is a useful process that can cause thermal, acoustic, and electrical characteristic changes in polymer materials. However, its development is limited due to low productivity. A pattern was imprinted on the surface using a polymer gas mixture with a 3D-printed polymer mold. The process was controlled with changing weight gain by controlling saturation time. A scanning electron microscope (SEM) and confocal laser scanning microscopy were used to obtain the results. The maximum depth could be formed in the same manner as the mold geometry (sample depth: 208.7 μm; mold depth: 200 μm). Furthermore, the same pattern could be imprinted as a layer thickness of 3D printing (sample pattern gap and mold layer gap: 0.4 mm), and surface roughness was increased according to increase in the foaming ratio. This process can be used as a novel method to expand the limited applications of the batch-foaming process considering that MCPs can impart various high-value-added characteristics to polymers. [ABSTRACT FROM AUTHOR]