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Hierarchical layered structures, whether in a compact form like nacre or a porous manner like bone, are well known for their combined features of high stiffness, strength, and lightweight, inspiring many man-made materials and structures for high performance applications. The use of nacre/bone like hierarchical structures in polymer nanocomposites can achieve excellent mechanical and functional properties with high filler volume fractions after carefully aligning functional nanofillers, although the fabrication and processing remain a great challenge. In this work, a bio-inspired lightweight nano-cellular epoxy/graphene-Fe3O4 nanocomposite with high nanofiller loading of 75 wt.% was successfully fabricated by combining features from both nacre and bone structures, via a simple compression molding process together with an eco-friendly supercritical CO2 foaming process to achieve robust mechanical strength and excellent electromagnetic interference (EMI) shielding effectiveness (SE) simultaneously. Highly aligned graphene-Fe3O4 nanoplatelets with well controlled nanoscale porous structures (52.6 nm) enabled both low density (1.26 g/cm3) and high specific EMI SE >5200 dB/cm2/g, as well as preserved tensile strength of 67 MPa. This study provides a sustainable route to fabricate nature mimicked structures with high performance and high flexibility for a wide range of applications, from portable electronics to healthcare devices.

In the last two decades, the naturally occurring polysaccharides have gained great attention because of their potential applications in different sectors, for example, from food to biomedical sectors. Chitosan is a cationic polysaccharide with good transparency, and currently, it has been considered also as suitable material for the formulation film and coating in cultural heritage protection. In this work, the chitosan films (Ch), with and without natural antioxidant such as citric acid (CA), are formulated considering two different processing techniques: (i) conventional solvent casting and (ii) compression molding, that is an unconventional method for this polysaccharide, giving the possibility to formulate films with extended surface and constant thickness. The effects of processing conditions and antioxidant presence on the properties and performance are evaluated by thermo-gravimetric analysis, FTIR and UV-visible spectroscopy, water contact angle measurements and tensile test. Besides, the durability of all investigated Ch and Ch/CA has been evaluated subjecting thin film to UVB exposure and monitoring their structural changes by FTIR analysis in time. All obtained results suggest that the chitosan films can be processed successfully by both solvent casting and compression molding techniques. Further, the CA presence in Ch films has a beneficial effect on the thermal resistance and durability and no negative effect on the transparency and optical properties.

In recent years, one of the main challenges is to improve the mechanical performance of bio-composites to be used as structural parts for the construction, automotive, and aviation sector. This paper may contribute to developing durable structural bio-composite parts with starch addition. The mechanical properties of bio-composites reinforced by eucalyptus or pine fibers (48 wt %) compound with Cationic Starch (48 wt %) and Carboxymethyl cellulose (CMC) (4 wt %) were determined. The production method was a combination of molded pulp, extrusion, and compression molding production techniques. To see the effect of adding starch to bio-composites and different production methods, the mechanical performance of these natural fibers produced by the conventional molded pulp production method (without any additives) was also found and compared with the composite samples. Composite samples indicate significantly better tensile, flexural, and compressive values, at least four times, compared with the molded pulp samples. On the other hand, the molded pulp samples had more than 2 times better impact characteristics against composites. Using molded pulp technic in composite production (investigated in the study) is a new idea and may give some opportunities with its serial production compatibility and geometry freeness, to the industry.

Recently, natural filler reinforced polymer composites are important materials for various engineering applications. Hence, this present work focuses on utilization of Cocos nucifera shell powder (CNSP) as a filler in vinyl ester (VE) resin to produce particulate composite specimens. The particulate composite plates with various weights or filler contents from 5 to 30 wt% were fabricated, using compression molding technique. The fabricated composites were subjected to tensile, flexural, impact, hardness, heat deflection and swelling behavior tests to obtain their corresponding material properties. Energy dispersive X-ray analysis was carried out on the C. nucifera shell powder/vinyl ester (CNSP/VE) composite specimens to investigate into the presence of their elements, in addition to the aforementioned tests. From the experimental results obtained, it was observed that the optimum mechanical properties of CNSP/VE composites were obtained at 15 wt% of filler content, having tensile, flexural and impact strengths of 38.70, 105.13 MPa and 33.04 kJ/m2, respectively. Also, the heat deflection temperature results varied from 158 (0 wt%, neat VE resin) to 171 °C along various percentages of filler contents. Lastly, the morphological study/analysis of the fractured CNSP/VE composite specimens was conducted by using a scanning electron microscope (SEM) to confirm the experimental data/results obtained. It was evident that CNSP/VE composite structures could be potential substitutes for some synthetic composites. Also, they are suitable for various engineering applications in aerospace, electrical/electronics and automobile industries, based on their properties.

Polyetherketoneketone (PEKK) is a new evolving polymeric material, and is considered as another important member of the polyaryletherketone (PAEK) family in addition to polyetheretherketone (PEEK). Hot compression molding can be used to compact and consolidate the PEKK products, where the temperature and pressure play key roles to affect the molecular mobility, entanglement and crystallization, and thus the mechanical properties of PEKKs. In this study, a preheating treatment was introduced in the compression molding, and it is found that such preheating is very essential to avoid the formation of crystal Form II, based on the increased chain entanglement. Molecular dynamics simulations revealed that the molecular mobility is always suppressed when a compression is applied. Therefore, by increasing the entanglement via the preheating and maintaining such entanglement in the consequent compression molding, strong and tough PEKK materials were obtained, with a negligible fraction of crystal Form II.

Polypropylene/epoxy/synthetic graphite (PP/EP/SG) and high-density polyethylene (HDPE/EP/SG) composites were prepared by melt mixing followed by compression molding. The immiscibility of the polyolefins with epoxy was confirmed by thermogravimetric analysis. Scanning electron microscopy (SEM) studies showed that HDPE/EP blend exhibits inferior interfacial adhesion between the component polymers compared to PP/EP blend. Also, the effect of SG content on flexural properties, density, moldability, water absorption, and porosity of the PP/EP/SG and HDPE/EP/SG composites was investigated. For both PP/EP/SG and HDPE/EP/SG composites, flexural modulus, density, and porosity increased with increase in SG content. For PP/EP/SG composites, the water absorption decreased from 0.154% at 30 wt% SG to 0.072% at 70 wt% SG. Further increase in SG content to 80 wt% caused an increase in water absorption. On the other hand, water absorption for HDPE/EP/SG increased with SG content all through. At the same filler loadings, PP/EP/SG composites showed lower density and porosity and performed better in terms of flexural modulus and water absorption compared to HDPE/EP/SG composites.

In this study, the nonisothermal differential scanning calorimetry (DSC) was carried out to evaluate the curing reaction of fiber/epoxy laminates. The optimal curing process of the prepreg was obtained by T-β extrapolation method and nth-order reaction curing kinetic equation. The bending strength, impact strength and thermodynamic properties of the composite laminates with different ply orientations were investigated, respectively. The results show that the apparent activation energy and the reaction order of the prepregs are 82.89 kJ/mol and 0.92, respectively. The curing process of carbon fiber/epoxy resin prepreg is 130 ℃ /60min + 160 ℃/30 min. The bending strength of [0]10 laminate is 1948.3 MPa, which is 11.8 times higher than that of [+ 45/-45]5s laminate, and 96.4% higher than that of [0/90]5s laminate. The impact strength of [0]10 laminate is higher than that of [+ 45/-45]5s and [0/90]5s laminates. The glass transition temperature (Tg) of the laminates is 142 ~ 146 ℃, and the loss factor of [0]10 laminate is significantly higher than that of [+ 45/-45]5s and [0/90]5s laminates. This research provides a theoretical basis for the further application of prepregs to fiber composite materials.

Injection compression molding (ICM) is a hybrid injection molding process for manufacturing polymer products with high precision and surface accuracy. In this study, a 3D flow simulation was employed for ICM and injection molding (IM) processes. Initially, the process parameters of IM and ICM were discussed based on the numerical simulations. The IM and ICM processes were compared via numerical simulation by using CAE tools of Moldflow software. The effect of process parameters of mold surface temperature, melting temperature, compression force and injection time on clamping force and pressure at the injection location of molded 3D BJ998MO Polypropylene (MFI 100) part was investigated by Taguchi analysis. In conclusion, it was found that the ICM has a relatively lower filling pressure than ICM, which results in reduced clamping force for producing a 3D thin-walled polymeric part.

This work aimed to study the mechanism of toughness improvement of polylactic acid (PLA) by using a biobased plasticizer. Ozonized soybean oil (OSBO), acting as a biobased plasticizer, was prepared by the ozonolysis reaction. The functional groups and chemical structure of OSBO were characterized by FTIR and NMR techniques, respectively. Plasticized PLA specimens were prepared by compounding using a corotating twin-screw extruder and sheet forming using a compression molding machine. The influences of OSBO contents, varying from 0 to 15 wt%, on PLA were evaluated via mechanical and thermal testing and morphological analysis. After the ozonolysis reaction, there was an increase in ester groups and the formation of hydroxyl groups in OSBO. With increasing OSBO content, it was found that elongation at break and impact strength tended to increase, whereas tensile strength decreased. The glass transition, crystallization and melting temperatures of PLA continuously decreased as a function of OSBO content. The presence of OSBO enhanced crystallization of PLA. OSBO at low content acted as a plasticizer for PLA, whereas OSBO at 15 wt% formed fine oil droplets acting as an impact absorber by energy dissipation.

This study investigates the addition of ground tire rubber (GTR) into virgin polyamide 6 (PA6) to produce thermoplastic elastomer (TPE) blends. In particular, a wide range of GTR concentration (0–100% wt.) was possible by using a simple dry blending technique of the materials in a powder form followed by compression molding. The molded samples were characterized in terms of morphological (scanning electron microscopy), physical (density and hardness) and mechanical (tension, flexion and impact) properties. The results showed a decrease in tensile and flexural moduli and strengths with GTR due to its elastomeric nature. However, significant increases were observed on the tensile elongation at break (up to 167%) and impact strength (up to 131%) compared to the neat PA6 matrix. Based on the results obtained, an optimum GTR content around 75% wt. was observed which represents a balance between high recycled rubber content and a sufficient amount of matrix to recover all the particles. These results represent a first step showing that a simple processing method can be used to produce low cost PA6/GTR compounds with a wide range of physical and mechanical properties.

Bond exchange via neighboring group-assisted reactions in dynamic covalent networks results in efficient mechanical relaxation. In Nature, the high reactivity of RNA toward nucleophilic substitution is largely attributed to the formation of a cyclic phosphate ester intermediate via neighboring group participation. We took inspiration from RNA to develop a dynamic covalent network based on β-hydroxyl-mediated transesterifications of hydroxyethyl phosphate triesters. A simple one-step synthetic strategy provided a network containing phosphate triesters with a pendant hydroxyethyl group. 31P solid-state NMR demonstrated that a cyclic phosphate triester is an intermediate in transesterification, leading to dissociative network rearrangement. Significant viscous flow at 60-100 °C makes the material suitable for fast processing via extrusion and compression molding.

A chemical foaming process of polylactic acid (PLA) was developed via the solid-state processing methods of solid-state shear pulverization (SSSP) and cryogenic milling. Based on the ability of solid-state processing to enhance the crystallization kinetics of PLA, chemical foaming agents (CFA) are first compounded before foaming via compression molding. Specifically, the effects of the pre-foaming solid-state processing method and CFA concentration were investigated. Density reduction, mechanical properties, thermal behavior, and cell density of PLA foams are characterized. Solid-state processing of PLA before foaming greatly increases the extent of PLA foaming by achieving void fractions approximately twice that of the control foams. PLA’s improved ability to crystallize is displayed through both dynamic mechanical analysis and differential scanning calorimetry. The solid-state-processed foams display superior mechanical robustness and undergo low stress relaxation. The cell density of the PLA foams also increases with solid-state processing, especially through SSSP. Additionally, crosslinking of PLA during the pre-foaming processing step is found to result in the greatest enhancement of crystallization but decreased void fraction and foam effectiveness. Overall, SSSP and cryogenic milling show significant promise in improving chemical foaming in alternative biopolymers.

Para-aramid fiber reinforced composite are the premier choice for protective applications due to their superior mechanical properties. Use of thermoplastic matrices in such composites is gaining the interest of researchers due to their better energy absorption. Polyvinyl butyral (PVB), a thermoplastic matrix, has very good mechanical and impact properties. Many studies have reported in the literature on the characterization of mechanical performance of thermoset composites for impact applications, however, there is a need to study para-aramid (PA) thermoplastic composite produced with PVB as well as further improvement of their properties using particulate reinforcements. In the present work, prepreg were developed by impregnating PA woven fabrics with a slurry of PVB, with and without silica micro particles (SMP) and glass microspheres (GMS) ranging from 1–4 %. Composites were fabricated using compression molding. 3-point bending (flexural), Pendulum (Charpy) impact and drop weight impact testing of the composites were performed. The results showed that by the addition of SMP and GMS the impact properties were increases and GMS gives better results as compared to SMP. One-way ANOVA (Tukey) statistical analysis supports the experimental findings.

A detailed investigation on the effects of hydrothermal aging on the mechanical and thermal performance of woven carbon-fiber-reinforced polyamide 6 (CF/PA6) laminates processed using hot compression molding is presented. A surface treatment with a polyurethane dispersion (PUD) agent is applied on CFs to enhance the interfacial bonding capability between the CF and PA6 matrix. The moisture uptake results indicate that untreated CF/PA6 laminates exhibit higher equilibrium moisture absorption (M∞), corrected diffusion coefficient (DC), and rate of diffusion (k) than treated CF/PA6 laminates, implying that the interface damage of untreated CF/PA6 laminates is more pronounced than that of treated CF/PA6 laminates. The mechanical performance of the CF/PA6 laminates reduces significantly after water absorption and hydrothermal aging. Nevertheless, PUD-treated composites exhibit higher remaining flexural property than the virgin composites, due to the improved durability of CF/PA6 interface, as verified by the scanning electron microscopy results. Dynamic mechanical properties (i.e., Tg, storage modulus, and tan δ) of the treated CF/PA6 laminates degrade more slowly than those of the untreated CF/PA6 laminates. Finally, the relationships between flexural property retention and moisture absorption ratio (i.e., Mt/M∞), and between flexural property retention and tan δ for both types of CF/PA6 laminates are established.

The global production of edible oil from plant species is growing rapidly and canola is a major abundant source of edible oil in the world. Canola meal (60 % of canola oil seed), the residue remaining after extraction of oil from the seed, is an important stock feed but also has the potential to be used for additional applications such as the production of composite materials. In the present study, canola seed meal is ground into fine particles using a Wiley mill and blended with a poly(vinyl butyral) resin and compression molding at 180 °C. The micro-structural morphology, and mechanical properties such as tensile, flexural and viscoelastic properties of the composites are measured and corresponding results are described. A canola meal composite with poly(vinyl butyral, at a 50:50 mass ratio possesses an average tensile strength of 9.8 MPa and flexural strength of 23.9 MPa. It shows a glass transition temperature at around 60 °C as observed by dynamic mechanical analysis. Scanning electron microscopic study reveals a two-phase microstructural morphology in the blended composites. All composites were hydrophobic, showing water contact angles greater than 90 °. These properties indicate that canola seed meal and poly(vinyl butyral) composites have the potential to be used in various applications as a replacement of traditional plastic materials..

Hot-press compression molding was used to resinify a renewable source-derived linear 1,4-linked β-D-glucan copolymer, i.e., konjac glucomannan (KGM), via the generation of reactive aldehyde groups ...

The influence of different wt. % of halloysite nanotubes (HNTs) on the mechanical properties of glass laminate aluminum reinforced epoxy (GLARE) was explored. GLARE (3/2) with quasi-isotropic lay-up, [Al/[(0°/90°)/(45°/−45°)]s/Al/[(0°/90°)/(45°/−45°)]s/Al] filled with 0, 0.25, 0.5, 1, 2 and 3 wt. % of HNTs was fabricated using hand lay-up followed by compression molding. Tensile, flexural, in-plane shear, interlaminar shear, bearing and impact tests were conducted. Results revealed that the maximum effect on the studied mechanical properties was obtained at 1 wt. % of HNTs. Further increase in HNTs wt. % reduces the trend. The tensile, flexural, in-plane shear and interlaminar shear properties of GLARE filled with 3 wt. % of HNTs were lower compared with original GLARE. But the bearing strength and impact strength are still higher. To examine the fracture mechanism, scanning electron microscope (SEM) images were taken. Field emission scanning electron microscope (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to show the chemical composition of the studied samples.

This paper investigates the mechanical behavior of an interlocking structure made of flax/poly(lactic acid) (PLA) composites manufactured using hot press compression molding. The flax/PLA composite manufactured at a temperature of 190°C and pressed for 10 minutes obtained the highest values of strength and modulus. A range of core cell sizes between 10 and 40 mm with a height from 20 to 40 mm was fabricated using a simple slotting technique. The larger core size offers a better relative density value when comparing to the smaller size (with a similar number of layers). The results also showed that the 10 mm core size exhibits better compression strength than the 20 and 40 mm core sizes. In contrast, the specific energy absorption (SEA) values of the structures increase as the core size decreases.

Flax fiber braided yarn plain woven fabric reinforced Poly Lactic Acid (PLA) bio-composites are fabricated using film stacking and hot-press compression molding method. Effect of fiber weight fract...

Numerous adverse effects are reported from excessive usage of synthetic polyolefins including major environmental concerns. Since then, the development of natural-based polymer composites is escalating, to replace the versatile conventional plastics that possess excellent mechanical and thermal properties. Rubber seed shell (RSS) is a novel and abundant natural-based substituent that is highly composed of hemicellulose and cellulose. In this work, we reported on the performance of RSS-filled polypropylene composites added with two different types of compatibilizers: epoxidized vegetable oil (EVO) and phthalic anhydride (PA). The composites were produced using a Haake internal mixer and a compression molding. The tensile, flexural, and impact properties of the composites were analyzed. Later, we investigated the thermal stability and water absorptivity of the composites. The mechanical, thermal, and water absorption properties of the RSS-filled composites deteriorated with increasing RSS loadings. For both EVO and PA-compatibilized systems, the mechanical properties were enhanced except for the elongation-at-break of the composites. PA-compatibilized composites recorded better thermal stability and water absorption resistance under ambient conditions compared to RSS composites with EVO. The qualitative structural evidence of the composites enhanced properties and deterioration were observed using a Zeiss Supra scanning electron microscope. As a novel natural filler, RSS has adequately proven its practicability in manufacturing environmentally friendly natural composites with acceptable mechanical and thermal properties.

The effect of annealing on the electrical and rheological properties of polymer (poly (methyl methacrylate) (PMMA) and polystyrene (PS)) composites filled with carbon black (CB) was investigated. For a composite with CB content near the electrical percolation threshold, the formation of conductive pathways during annealing has a significant impact on electrical conductivity, complex viscosity, storage modulus and loss modulus. For the annealed samples, a reduction in the electrical and rheological percolation threshold was observed. Moreover, a simple model is proposed to explain these behaviors. This finding emphasizes the differences in network formation with respect to electrical or rheological properties as both properties belong to different physical origins.

Resinification of milled waterfowl feathers was attempted via a conventional hot-compression molding and its resinification behavior and the physical properties of the resultant resin were investig...

Polyetheretherketone (PEEK) sheets with the thickness of 0.5 mm were prepared by compression molding process using Victrex PEEK-450PF, and then PEEK sheets with different crystallinities were obtained by controlling the cooling rate. The optical characteristics of the samples were respectively measured by laser power meter, UV-VIS-IR spectrophotometer. And with the process parameters of laser power density of 245 W/cm2 and moving speed of 5 mm/s, the effect of crystallinity on the laser energy absorption of PEEK and the influence of laser irradiation on the crystallization properties of PEEK sheets were systematically studied. Finally, numerical model of laser energy absorption by PEEK was constructed with COMSOL software. The results show that the reflectivity of PEEK will increase with the increase of crystallinity, while the transmittance decreases. The pure PEEK sheets do not strongly absorb the laser at the wavelength of 1070 nm and the amorphous PEEK is more likely to be ablated. Carbonized samples during the laser irradiation was taken for XRD test and found to be amorphous. After laser irradiation, the crystallinity of the semi-crystalline PEEK material will decrease, but the originally amorphous peek crystallinity will increase slightly. Besides, the numerical simulation results are in good agreement with the experimental results.

Chopped kenaf fibers, poly(lactic acid) (PLA), and ammonium polyphosphate (APP) were uniformly compounded by twin-screw extrusion process, and then kenaf/PLA biocomposites with various APP loadings were fabricated by compression molding. The effects of APP on the flame retardant, tensile, dynamic mechanical, and thermo-dimensional properties were investigated. The biocomposites exhibit highly increased flame resistance, showing the limiting oxygen index increased with increasing the APP loading and the UL-94 V-0 level with 20 wt.% and higher APP loadings. The thermal stability of the biocomposites was increased, whereas the thermal expansion behavior was decreased with increasing the APP loading. The incorporation of APP into the PLA matrix contributed to simultaneously enhancing not only the flame retardancy, thermal stability, and thermo-dimensional stability, but also to enhancing the tensile and storage moduli of kenaf fiber/PLA biocomposites.

The objective of this study was to produce and characterize gelatin films produced by thermo-compression, a technique that requires less processing time and space, making it appropriate for the development of commercial biodegradable protein-based films. A control film of gelatin with glycerol and water (M1) was compared with three films reinforced with Agave angustifolia Haw microfibers (MF) (M2–M4), three films reinforced with bentonite nanoclay (BN) (M5–M7), and three films reinforced with both MF and BN (M8–M10). The surface and cross-section morphology of the films showed some roughness with pores and inhomogeneities as the MF and BN concentration increased. The X-ray diffraction analysis confirmed the nanoclay intercalation. The films thickness was a function of the glycerol content, and all films had an apparent density slightly higher than unity. The films appearance was measured via the CIELab scale where the parameter a* was found to increase toward a reddish color, while b* showed an increasingly yellowish color. The presence of both MF and BN led to increased tortuosity inside the films, thus affecting the permeability of water molecules. Particles addition increased the tensile strength and elasticity, while the elongation at break decreased. The thermal stability improved with particles addition, especially for BN due to its inorganic nature. All the results could be related to a high level of interaction between the components and the protein matrix as observed via Fourier transform infrared spectroscopy, showing proper compatibility and a synergy among the materials. Due to the properties obtained, biomaterials can have good mechanical and high barrier properties combined with short life, disposable and environmentally friendly for food packaging and biomedical applications.

This study focused on improving the toughness properties of poly(lactic acid) (PLA) by blending with either epoxidized natural rubber (ENR) or ENR plus nanosized silica (nSiO2). ENR with 30 mol% epoxidation (ENR-30) was synthesized via in situ performic acid epoxidation of NR latex under a controlled amount of hydrogen peroxide and formic acid. PLA was melt-mixed with three weight percentages (10–30 wt %) of ENR-30 using an internal mixer, followed by compression molding. The 80/20 PLA/ENR-30 blend showed the highest impact strength and elongation at break, indicating the optimally possible improvement in the toughness of PLA. This composition was further chosen for fabricating nanocomposites with nSiO2 at 1–3 phr. Nanocomposite at 2 phr nSiO2 revealed the highest impact strength with 1.8-fold over the neat blend, but the tensile properties of all nanocomposites decreased with the increasing nSiO2 contents. The scanning electron microscopy analysis showed a preferential distribution of nSiO2 in the ENR-30 phase rather than in the PLA phase. Based on thermal analysis results, the thermal stability of the entire nanocomposites was significantly higher than that of the neat blend, while the thermal behavior (Tg and Tm) of PLA in the nanocomposites showed no significant change.

Polypropylene (PP) is adopted as a matrix. This polymer is usually processed in the form of pellets with natural fillers to fabricate biocomposites. The micronized powder form of PP is rarely used by polymer manufacturers. This paper investigates the effect of polymer powder form on the overall properties of date palm filler-based composites. In particular, the mechanical, physical, and thermal properties of newly developed date palm powder (DPP)-filled composites were experimentally characterized, evaluated, and compared with two forms of PP: powder (PW) and pellet (PL). Specimens were fabricated using a laboratory-scale single-screw extruder followed by compression molding. The experimental characterization of materials supported by scanning electron microscopy (SEM) showed that the PW form of PP when used as a matrix in the biocomposites was very important to achieve a higher degree of homogeneity in filler distribution, stronger interfacial strength and thus enhancing the performance. Therefore, biocomposites fabricated using the PW form exhibited more advanced properties than those used with the PL form. Depending on the fiber content, tensile strength and flexural strength for PW-based biocomposites were 53% and 27% higher than similar values for PL-based biocomposites, respectively. Water absorption was lower in the case of PW form which indicated good durability of the developed material. The findings of the present study may help manufacturers to effectively process date palm powder-filled biocomposites to achieve better properties and enhanced performance.

The composition–processing–property relationship of imine containing reversible covalent bond containing polymers (RCBPs) was studied using an innovative (regarding this type of polymer) combination of characterization methods. This combination led, for the first time, to a classification of the various chemical reactions occurring during the processing of imine based RCBP, affecting their final chemical structure and properties. RCBPs, based on PIs (polyimines), were synthesized from polyethyleneimine (PEI) and terephthalaldehyde (TPA) in the presence of ethanol. The chemical composition and derived thermal and mechanical properties were investigated. Material characterization using ATR-IR, 13C-solid state NMR, swell tests, and a novel illustrative model based on the Flory–Rehner equation led to the conclusion that at least 80% of the secondary amine groups reacted to form a cross-linking network, along with 100% of the primary amines, and that during 20 min compression molding at 220 °C under 2.7 MPa, a post-curing reaction occurs. 13C-SSNMR and ATR-IR indicated that the chemical structure is determined not only by the reactants but also by the elevated temperature processing conditions. During heating, three mechanisms affect the final composition–transimination, reduction (back into amine groups) and oxidation (to oxaziridine and amide groups which are almost negligible). The reduction/oxidation processes were found to dominate the mechanical properties. The vitrification temperature (Tv), which is characteristic of RCBPs, is dependent on the thermal history, with a higher Tv resulting from longer compression molding times. The mechanical properties are affected by the processing temperatures, changing from high-performance to very low strength. Under specific processing conditions, the imine cross-linking bonds are reduced/oxidized, which causes the formation of more polar but lower energy bond cross-linking, resulting in lower tensile strength and a change in the hydrophobicity of the polymer, which may be used in future applications.

Exploring the simple fabrication process to prepare CNC@HAp for biological tissues is still a challenging subject considering the wide applications of the composites for bio tissues. In this work, aiming for the fabrication of CNC@HAp composites via a simple and environment-friendly process and materials, we propose the neutralization titration in the presence of CNCs in the suspension. Core–shell structured composite of cellulose nanocrystal (CNC) and hydroxyapatite (HAp) (CNC@HAp) was successfully synthesized via simple aqueous neutralization titration. The method studied successfully hybridizes CNCs with a certain amount of HAps and easily controls the coating amounts of HAps from 9 wt% to 17 wt%. In particular, CNC@HAp pellets were easily prepared by simple compression molding from the powder of hybridized CNCs and HAps and the pellets showed high mechanical strength of over 500 N with a low strain of less than 5%. Both the process and the product of the study were environmental-friendly, no toxicity, simple and pure therefore the CNC@HAp can be easily applied to tissue engineering and medical purposes.

Hybrid nanocomposites utilize the benefits of properties of different fillers to enhance its desired properties. Polyetheretherketone (PEEK) based hybrid nanocomposites have immense potential applications in aerospace, automobile, high-temperature electrical applications, and medical and health care. The present work is an attempt to improve the elastic modulus, hardness, fracture resistance, and storage modulus simultaneously by reinforcing the PEEK matrix with multiwall carbon nanotubes (MWCNTs) filler and 30 wt.% nano hydroxyapatite (nHA)-MWCNT hybrid filler. The nanocomposites having 0,1,3,5 and 7 wt.% of MWCNTs were fabricated by the Ball Mixing and Compression Molding Method. Customized Die Heater setup was used to ensure uniform heating and cooling during compression molding. The morphology was examined by Field Emission Scanning Electron Microscopy (FESEM) and Energy-Dispersive X-ray Spectroscopy (EDS) and uniform distribution of nano-fillers was observed. The nanoindentation method was adopted to investigate the Static Mechanical Analysis (SMA) and Dynamic Mechanical Analysis (DMA) at varying frequencies of loading, of nanocomposites. At 5 wt.% of MWCNTs, the enhancements in elastic modulus, hardness, fracture resistance, and storage modulus were observed to be 80%, 36%, 32%, and 58% respectively in case of PEEK/(0–7%)MWCNT nanocomposite and 104%, 76%, 16%, and 80% respectively in case of PEEK/30%nHA-(0–7%)MWCNT hybrid nanocomposite. The decrements in loss factor indicated the improvement in elastic behavior of nanocomposites with increasing wt.% of MWCNTs. The elastic modulus of PEEK/30%nHA-5%MWCNT hybrid nanocomposite was observed to be 7.67 GPa, which falls within the range of elastic modulus of the human cortical bone. The results revealed that 5 wt.% of MWCNTs is optimum filler composition for improving the mechanical properties.

This work has been developed for a comparative purpose concerning the processing and respective mechanical performance of CFRP composites processed by resin transfer molding (RTM) and compression molding (CM) techniques. Thermal and viscosimetric tests before processing certified the optimal parameter procedure. Both composites were submitted to short-beam shear tests and through microscopy to determine failure mechanisms. CM specimens presented a decrease of 27% in shear strength caused by the presence of macro porosity that induced crack initiation and connection of different delamination plies, causing the speeding up of crack propagation and jump of the interlaminar layer. The low capillary effect and higher viscous force were responsible for macro porosity, inducing heterogeneous impregnation in CM and to the direction reduce in mechanical behavior. On the other hand, more homogeneous impregnation in RTM specimens was responsible for the absence of macro porosity, ensuring higher values of shear strength and lower void volume fraction.

Green composites possessing biodegradable or recyclable characteristics have gained interest in recent years due to their ecofriendly, sustainable and lightweight characteristics over the conventional plastic-based materials. In this study, flax and jute natural fibers have been used individually and as hybrid reinforcement into Poly Lactic Acid (PLA) matrix. The composites developed are suitable to be used in biodegradable products in packaging and automobile industries. Hot press compression molding was used to fabricate samples of PLA/flax, PLA/jute and PLA/flax/jute (hybrid composites). The concentration of natural fibers in individual fiber-based composites was varied (between 0–50 %) by weight to investigate its effect on tensile and impact properties. Maximum tensile properties were obtained for 40 wt% single-fiber reinforced into PLA. This reinforcement content (40 wt%) was used as reference for hybrid composites. Hybrid composites were fabricated with different combinations of jute and flax fibers by keeping the total concentration of reinforcement equal to 40 % by weight. Tensile and Charpy impact tests were performed to evaluate the mechanical properties of the composites. Scanning Electron Microscopy of the tensile fractured surfaces was performed to observe the failure mechanism and adhesion at fibermatrix interfaces in the composites. Further characterizations included Fourier Transform Infra-Red spectroscopy and Biodegradability tests, which were performed according to ASTM standards. Fourier Transform Infrared analysis revealed interaction between the natural fibers (jute and flax) and PLA matrix in hybrid composites. The enhanced interaction in hybrid composites resulted in their improved impact resistance. Based on the results obtained in this study, the improved mechanical and biodegradable properties of these composites make it suitable for use in applications like food-packaging and indoor plastic products in automobiles, to reduce synthetic plastic pollution.

Untreated and treated jute fiber and nano-clay in various ratios were used to fabricate jute/nano-clay/epoxy hybrid composites through compression molding method. The dynamic mechanical and free vibration behaviours were evaluated by varying the concentration of NaOH (2.5%, 5% and 7.5%) and wt.% of nano-clay (1, 3, 5 and 7 wt.%). Experimental outcomes disclosed that the storage and loss modulus, damping factor and natural frequency are influenced by concentration of NaOH solution and nano-clay content. A positive shift (towards higher temperature) in glass transition temperature and enhanced natural frequency of the composites after NaOH treatment and nano-clay addition confirmed that superior interfacial bonding exists between the jute fibers and epoxy matrix. Finally, the composites incorporated with 5% treated fiber and 5 wt.% of nano-clay is suggested for low strength structural applications in construction and automobile industries.

In this study, biodegradable polylactic acid (PLA)/chitosan (Cs) composites were produced via melt compounding and compression molding techniques. Various chitosan loadings of 2.5, 5, 7.5 and 10 parts per hundred parts of polymer (php) were incorporated into PLA and its effects on thermal, water absorption kinetics, tensile and morphological characteristics were investigated systematically. Thermal analysis indicated that an increase in chitosan loading of up to 10 php enhanced the crystallinity percentage (χc) of neat PLA to an extent of 51%, yet reduced the thermal stability of the resulting biocomposites. The kinetic study results revealed that water absorption of PLA/Cs biocomposites approached the Fickian diffusion behavior. The maximum water uptake (Msat) increased with chitosan addition, which can be attributed to stronger water–filler interaction. This was correlated to higher diffusion (D), solubility (S) and permeability (P) coefficients, which suggested the acceleration in diffusion rate and better water permeation through the biocomposites. In addition, the tensile results of dry samples showed enhancement in tensile strength and tensile modulus by 2% and 14%, respectively, relative to neat PLA through the incorporation of 2.5 php of chitosan loading. However, the water-immersed biocomposites demonstrated deterioration in all tensile properties (tensile strength, tensile modulus, and elongation-at-break values) which signified hydrolytic polymer degradation. This was confirmed by the FESEM micrographs of the fractured surfaces which exhibited filler pulled-out phenomenon and cavity formation after 50 days of water immersion.

High water absorption capacity and low biodegradation of fiber reinforced composites are the major drawbacks, which limit their applications in different sectors. Development of composites with complete biodegradability is challenging as biodegradability may be incomplete by lowering of its water adsorption capacity. In this work, a series of thermoplastic starch (TPS) reinforced jute (10–40 wt%) composites were developed by compression molding and measured by their mechanical properties. The composite with 30% jute showed the maximum tensile strength (27.3 MPa). Contact angle, and water absorption measurements exposed that composites are moderately hydrophobic in nature. Both soil burial and fungal degradation testing showed biodegradability of composites. Characterizations of optimized composite before and after biodegradation test, were carried out by FTIR, SEM and optical microscope. The present study showed promise on feasible applications of jute-starch composites in packaging, automobile sector, cutlery, indoor furnishing, etc. as a substitute of plastic-based composites.

In this study, the accelerated weathering of PLA and its biocomposites produced with agro-industrial waste agave fibers was evaluated to better understand the lifetime of these materials. The effects of the fiber content, the fiber treatment with glycidyl methacrylate grafted PLA, and the fiber/matrix adhesion on the degradation of the materials were also analyzed. The biocomposites were prepared by dry blending, followed by compression molding using untreated and chemically modified agave fibers. The chemical treatment promoted a better fiber–matrix adhesion and lower fiber pull-outs resulting in high tensile and flexural strength values (similar to the neat PLA even with 40 wt% of fiber). Once the modification of the fiber–matrix was observed to be effective, the effect of accelerated weathering over compatibilized and uncompatibilized biocomposites was evaluated. The results showed that after accelerated weathering, the crystallinity of the biocomposites increased significantly, causing that the impact strength remains constant and, in some cases, even improved. At the same time, tensile and flexural properties were noticeably decreased. Nevertheless, the treated fibers which have better adhesion to the matrix led a better resistance to weathering degradation, which is confirmed by higher dimensional stability and lower decreases in tensile and flexural properties than biocomposites with untreated fibers.

Kevlar®-reinforced composites are used in high energy absorption applications. In the present work, Kevlar®-reinforced ultra-high molecular weight polyethylene composites were fabricated through microwave-assisted compression molding. The microwave-assisted compression molding parameters were optimized through trial and error method. Analysis of mechanical behavior of composites was accessed through uniaxial tensile testing, flexural testing, impact testing, and nano-indentation. The fractured specimens were observed using scanning electron microscopy. An increment of 92.2% was observed in the ultimate tensile strength of the ultra-high molecular weight polyethylene/Kevlar® composite compared to neat ultra-high molecular weight polyethylene. Flexural properties, impact energy absorption rate, and hardness property of the composite were increased by 27.1%, 91.6%, and 4.77%, respectively, compared to pure ultra-high molecular weight polyethylene. Enhanced mechanical properties may be attributed to unique microwave heating phenomena during microwave-assisted compression molding.

The hybridization of composites has recently seen an exponential growth in acceptance due to its ability to improve the property such as toughness of composites. Hybridization of fibers is known to give a better balance of properties and increases the opportunity to use natural fibers, thereby reducing the impact on the environment without compromising utility. This study deals with hybridization of ultrahigh-molecular-weight polyethylene (UHMWPE) with natural fibers such as flax and jute using phenol formaldehyde as the resin. Composite panels of 4 mm thickness, comprising of eight layers were fabricated in six different fiber stack sequences using hand lay-up and compression molding techniques. The effect of stack sequence on the composites' flexural, interlaminar shear, and impact properties were investigated using scanning electron microscopy and cone beam computed tomography techniques. Composites with outer UHMWPE fibers and having flax fibers as inner core were found to have superior flexural and interlaminar shear properties of 44.45 and 5.52 MPa, respectively. Also composites with surface layers of flax fibers displayed maximum impact strength of 91.08 kJ/m2 . The results indicate that the stack sequence has a significant influence on the properties of the composite under flexural and impact loading

The focus of this work was to analyze the influence of leaf treatments on mechanical, physical and chemical properties and thermal stability of the gelatin/lotus leaf composites. Lotus leaves were treated with drinking water at 95 °C for 5 min. The gelatin/untreated lotus leaf (referred to as GUL) and the gelatin/hot water treated lotus leaf (referred to as GHL) composites have been prepared by the compression molding technique. The composites have been investigated by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TAG), Scanning electron microscopy (SEM). Effect of the lotus leaf hand lay-up fiber orientation was studied for longitudinal, transverse and random orientation of the fibers. The tensile strength of gelatin/lotus leaf composites were influenced by the orientation of the fibers. It was found that longitudinal orientation delivered higher mechanical properties than that of the transverse and random orientation whether untreated or treated. The hot water modification of the lotus leaf was employed to improve the interfacial adhesion of the composites in order to improve the tensile properties. By using TGA analysis data and Ozawa-Flynn-Wall (OFW) method, the thermal stability and degradation temperature of the lotus leaves treated with hot water were higher than those of untreated leaves. In addition, the properties of the novel bio-composites were potential in further development of biodegradable packaging materials.

The present study investigates the physical, thermo-mechanical and tribological properties of coir–coconut husk particulate-reinforced polymer composites subjected to a corrosive environment. The composites were prepared by the conventional facile hot compression molding method. The composite was immersed in a strongly acidic environment of pH 2.2 for a period of 3, 6, and 9 days. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis were used to elucidate the structure and morphology of the composites. The thermal analysis using differential scanning calorimetry, water absorption, hardness, coefficient of friction and wear rate was performed as per the ASTM standards to characterize the as-prepared and aged composites. The experimental test results revealed that with an increase in acid aging time, the acid aged samples lost surface matrix such that the fiber was seen on the surface. The effects of corrosion seemingly reduced the crystallinity of the acid aged samples allowing amorphous regions to be trapped within the crystals. Water absorption of the samples increased with aging time due to inherent voids in the specimens as weight gain values were 5.27, 16.80, 19.33 and 19.91%, respectively for control and acid aged samples. Hardness values initially decreased with immersion time and increased which was attributed to the crystallinity of the specimens and to some extent the elemental carbon present in the specimens before and after aging. The measured hardness values of the control and acid aged composites were 2.98, 7.27, 14.40 and 9.07 HV, respectively. From the thermal analysis, it was noticed that the glass transition temperature (Tg) of the polymer shifts to higher temperatures as the aging time in the acidic medium increased, which can be attributed to cross-linking of the polymer chains. The control specimen shows higher coefficient of friction (CoF) because they are more rigid than the acid aged samples, and hence under dry sliding can cause more friction leading to increased heat and CoF.

This research investigates factors contributing mechanical stability of epoxy based composites using Taguchi optimization based grey relational approach. Natural fibers of sisal, banana reinforcement along with epoxy was used as the matrix material for this compression molding technique. The grey relational results observed 7th and 14th trials were having first and second position in mechanical properties: 10% sisal, 15% banana, 8% NaOH, 10 MPa pressure, and 100°C temperature composites; 20% sisal, 10% banana, 5% NaOH, 10 MPa pressure, and 120°C temperature were the combinations. The signal to noise ratio showed the optimized data as 20% sisal, 15% banana, 5% NaOH, 10 MPa pressure, and 100°C temperature. The relation between experimental and predicted grey relational grade using artificial neural network showed good correlation stating the network topology of 5-5-1 with good predictability for analyzing factors influencing mechanical properties. SEM analysis observed pullouts of fiber, breakage in the matrix, and these two causing voids in the single reinforcement substitution using sisal and banana. Hybridization using both the fiber reduces the surface abnormalities and adds to the properties.

Hot-press compression molding was attempted to resinify two renewable source-derived linear (1→3)-β-D-glucan polymers, i.e., paramylon or curdlan via the generation of reactive aldehyde groups that...

Nowadays most of the researchers are focusing their research on pollution free environment, bio-degradable nature and balanced ecological aspect while fabricating the composite materials rather than mechanical strengths, costs, processing methodologies, etc. The objective of this experimental study is to analyze the influence of the bio-based eggshell nanoparticles on the thermal and morphological properties of alkali-treated hemp fibre reinforced epoxy composites. The composites were fabricated by hand lay-up process followed by compression molding technique and the properties of composites are analyzed by using thermo-gravimetric analysis, Fourier transform Infra-red spectroscopy, differential scanning calorimetry and X-ray diffraction techniques. The mechanical properties such as tensile, shear, flexural and impact strengths as well as water absorption characteristics of these composites are also investigated. The morphological characteristics were analyzed by scanning electron microscopy analysis. The results clearly showed that the incorporation of eggshell nanoparticles has significant influence on the thermal and morphological properties of alkali-treated hemp fibre composites.

This research utilized three animal proteins which are whey protein isolate (Wh) and two types of gelatin, including bovine gelatin (BG) and chicken gelatin (CG) from bovine shin bones and chicken feet respectively, to improve the mechanical properties of whole potato flour bioplastics. The goal is the development and characterization of eco-friendly bioplastic sheets by employing the compression molding method. The tensile, DMTA, FTIR and TGA characteristics of the blending bioplastics were compared with bioplastic made from whole potato flour as control. Results showed that protein treatments greatly enhanced the tensile strength (at least 2 times), tan δ (up to twice) and elongation at break (3 to 11 times). Furthermore, the thermal stability of studied bioplastics does not differ up to 200 °C. Among the blending bioplastics, the BG bioplastic had the highest tensile strength (5.67 MPa) and CG bioplastic had the highest elongation at break (20.50%). Meanwhile, the investigation of functional groups using Fourier-transform infrared spectroscopy (FTIR) confirmed better molecular interactions in the blending bioplastics. This research shows the feasibility of producing animal protein‐potato flour biodegradable edible bioplastic materials with different properties and, consequently, different applications, which contribute to adding a high value to different byproducts from the livestock/poultry industries.