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• We provide correlations among structural, thermal, and mechanical properties of medical device polymers following gamma, X-ray, and electron beam irradiation. • For most of the polymers investigated, little to no variation in properties was observed among the various radiation sources at a given dose. • This study supports medical product polymer selection for sterilization radiation resistance in view of product design and function. Stemming from security threats and shortages in supply, a recent push has emerged to expand alternatives to radioisotope Cobalt-60 gamma radiation for sterilization of polymeric medical products, including electron beam (E-beam) and X-ray machine-based sources. However, before large-scale implementation, the effects of these non-isotope-based methods must be thoroughly investigated from several perspectives, involving their potential detrimental effects on the structural, thermal, and mechanical properties of polymers in medical devices. This paper investigates such effects in commonly used medical device polymers, including polypropylene homopolymer (PPH), polyolefin elastomer (POE), low-density polyethylene (LDPE), acrylonitrile butadiene styrene (ABS), and chlorobutyl rubber (CIIR). To connect radiation-driven changes in polymer structural and thermal properties and corresponding changes in mechanical properties, several characterization techniques were utilized, including gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). We found that the tensile strength of X-ray irradiated PPH, as well as X-ray, E-beam, and gamma irradiated CIIR decreases due to chain scission, which is corroborated by GPC and DMA. The GPC results of LDPE suggest chain scission, but interestingly without a corresponding decline in tensile strength. By comparison, POE and ABS appear to undergo further crosslinking with increasing irradiation dose, which generally strengthens them. Importantly, in the vast majority of the cases, there were small to no changes in properties upon changing radiation technologies (at a given dose), i.e., no radiation source dependence. However, in a few specific cases, radiation method dependencies did arise, for instance, in terms of the molecular weight of PPH being significantly increased upon X-ray irradiation, while the melting temperature, glass transition temperature, and elongation at break reduced compared to gamma. Overall, this study provides valuable insight into radiation-driven chemical and structural changes in polymers that produce changes in physical and functional properties. [ABSTRACT FROM AUTHOR]

• A novel macromolecular phosphorus and nitrogen containing flame retardant named PDPSB was synthesized and characterized. • The flame retardancy of PC was significantly improved by incorporation with PDPSB. • PDPSB had a slight influence for PC matrix on the mechanical properties due to the good compatibility and dispersion. • PDPSB could exert excellent flame retardancy both in the gaseous phase and the condensed phase. In this paper, an innovative macromolecular phosphorus-nitrogen containing flame retardant (PDPSB) was successfully designed and synthesized to investigate its impact on the flame retardancy, burning behavior, thermal stability, mechanical properties of polycarbonate (PC) composites. Furthermore, an in-depth exploration of the potential flame-retardant mechanism was conducted. The combustion results indicated that PC-3 with 3 wt% PDPSB reached V-0 rating in UL-94 test and showed a high limiting oxygen index (LOI) of 33.0 %. Compared to pure PC, the values for peak of heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) of PC-3 were decreased by 37.9 %, 11.1 % and 4.9 %, respectively. It was noteworthy that the amount of char residue for PC-3 was raised from 7.4 % for pure PC to 15.8 % with increasing 113.5 %. The thermogravimetric analysis (TGA) results under N 2 atmosphere revealed that PDPSB possessed preferable thermal stability with initial decomposition temperature (T initial) of 342.6 °C and higher char residue yield of 48.4 %. With increasing the amount of PDPSB, the maximum mass loss rate (R peak) was reduced and the char residue yield was increased for PC/PDPSB composites. In addition, the mechanical properties of PC/PDPSB composites were well maintained due to the good compatibility and dispersion between PDPSB and PC matrix. The tensile, flexural and izod impact strength of PC-3 were weakened by 4.3 %, 1.7 % and 16.8 % in comparison of pure PC, respectively. Based on the investigation into the flame-retardant mechanism of PDPSB, the excellent flame retardance of PC/PDPSB composites has been validated. In gaseous, the release of pyrolysis gases was suppressed and active radicals were captured by generated phosphorus free radicals. In condensed phase, the stable char residue with phosphorus and nitrogen elements acted as a barrier to hinder heat, flame and oxygen. This high-efficient single-component multifunctional additive presented a novel approach to the development of fire-resistant polymers with enhanced performance characteristics. [Display omitted] [ABSTRACT FROM AUTHOR]

Paramylon, which is a β -(1,3)-D-glucan photosynthesized by Euglena , was chemically modified by esterification. Various paramylon triesters with different alkyl chain lengths (carbon numbers 2–12) were successfully prepared. All of the paramylon triesters have higher thermal degradation temperatures than that of neat paramylon. Moreover, it was found that the paramylon triesters with C2–C6 alkyl chains are crystalline polymers with melting temperatures from 281 °C to 114 °C, and those with C8–C12 alkyl chains are amorphous polymers, confirmed by both DSC and X-ray diffraction analysis. Paramylon triesters with C3–C12 alkyl chains could shape self-sustaining films by both solvent-casting and melt-quench methods with high optical transmittance and sufficient tensile strength or elongation at break. Thermal and mechanical properties of paramylon triesters can be controlled freely from hard to soft by substituted acyl length. In the cases of the crystalline paramylon triesters, highly oriented and crystallized films could be fabricated by the thermally stretched method, and their tensile strengths have been obviously improved. Well-oriented X-ray fiber diagrams of the stretched and crystallized films suggest that all of the paramylon triesters have rare 5-fold helix conformation of molecular chains in crystal. [ABSTRACT FROM AUTHOR]

The hydrolytic degradation of aliphatic polyurethane (PU) films made from polycarbonate-based macrodiol (MD), diisocyanate-1,6-hexane, butane-1,4-diol (BD) and d , l -lactide-based oligomeric diol (DLL) was studied. The influence of the length of DLL was tested in phosphate-buffered saline (PBS) for periods of up to 12 months. One macrodiol (molecular weight ∼2000 Da), three DLL oligomers (∼400, 660 and 850 Da) and three MD-to-BD-to-DLL molar ratios were chosen for the PU synthesis. The isocyanate-to-total hydroxyl-group ratio was kept constant at 1.05. The functional properties of raw polyurethane films and samples immersed for 1, 3, 6, 9 and 12 months in a model physiological environment (37 °C, pH = 7.4) were studied from the segmental to the macroscopic level. Tensile testing and water uptake experiments, as well as differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR) and wide-angle X-ray diffraction (XRD) analyses, were used for the characterization of the raw and PBS-treated films. The study shows that the length of the DLL chain is much more important for functional PU properties than the mass content of DLL in the PU film. The incorporation of the shortest DLL into the PU backbone leads to a degradable PU material with outstanding tensile properties when not subjected to the hydrolytic treatment. However, the incorporation of oligomers with longer DLL chains results in PU materials with substantially deteriorated tensile characteristics due to more pronounced phase separation compared to systems without DLL or with the shortest DLL. The degradability of the PU films can be controlled to a relatively broad extent by altering DLL content and length. The investigation of functional properties of new PU materials during the hydrolytic process under physiology-mimicking conditions is important for potential medical/package coating/film applications. [ABSTRACT FROM AUTHOR]

• A bio-based, phosphorus-phosphorus, hyperbranched oligomer (DIT) was synthesized. • DIT enabled EP to achieve durable fire safety. • DIT significantly improved mechanical robustness and toughness of EP. • DIT well maintained high transparency and thermal resistance of EP. The manufacture of transparent, durable fire-safe, strong yet tough epoxy resins (EPs) remains a great challenge. Herein, a novel hyperbranched, P-P synergetic, bio-based flame retardant (DIT) was synthesized, which was composed by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), bio-derived itaconic anhydride (ITA) and trihydroxymethylphosphine oxide (THPO) moieties. Adding 2 wt% DIT enabled the EP/2DIT sample to achieve a UL-94 V-0 rating and a limiting oxygen index (LOI) of 36.6%. The peak heat release rate and total smoke production of EP/4DIT sample with 4 wt% DIT were 23.8% and 19.9% lower than those of virgin EP sample. Notably, the EP/DIT sample featured durable flame retardancy because of the oligomeric structure of DIT. The high flame-retardant efficiency of DIT was mainly due to the synergism between DOPO and THPO. DIT simultaneously strengthened and toughened EP thermoset at a low addition (≤2 wt%), and 2 wt% of DIT increased the elongation at break, tensile strength, flexural strength and impact strength of EP/2DIT sample by 35.8%, 40.5%, 24.2% and 21.2%. Moreover, the glass transition temperature (T g) of EP/2DIT sample was equal to that of EP sample, and the high transparent was maintained. Hence, this work offers an all-rounded design for the creation of durable flame-retardant EPs with superior mechanical properties, thermal resistance and transparency by introducing hyperbranched, P-P, bio-based flame retardants, which shows huge potential and broad prospect. [Display omitted] [ABSTRACT FROM AUTHOR]

This study investigate the influence of gamma-irradiation (GI) doses from 0 up to 50 kGy on the polypropylene (PP) foams, mainly the impact on their structural and physical properties. It was found that structural properties were not significantly changed and the cellular structure of the PP foams sustain the same, while the thermal properties were significantly enhanced with increasing GI doses, due to the present cross-linking created within the irradiation. The cross-linking was confirmed also by the swelling measurements. The dielectric properties shows the three time increase of capacitance with increasing GI doses, due to the additional charges created in the foam voids by GI. Investigated mechanical properties in case of tensile tests as well as dynamical mechanical analysis proved, that enhanced behaviour was observed only in case of samples with irradiated by low doses, 1 kGy and 5 kGy, respectively, while the higher doses significantly decrease these ones, due to the present scission confirmed by FTIR and other investigations. Finally, it was found the competition between the cross-linking of the PP foam and present scission due to the applied GI and therefore the physical properties can be easily tailored. [ABSTRACT FROM AUTHOR]

The purpose of this study is to examine the effect of electron-beam (EB) radiation on biodegradable polylactic acid (PLA), and to understand radiation-induced degradation mechanisms. PLA films were irradiated between 0 and 120 kGy and physical properties were characterized by means of GPC, DSC, DMA and tensile drawing. It was shown that degradation of PLA under EB leads to a random chain scission responsible for a reduction of the molar mass. These molar mass changes affect glass transition temperature T g , degree of crystallinity, and mechanical properties. It was found that T g , stress and strain at break decrease with increasing irradiation dose, whereas the degree of crystallinity increases up to 45 kGy then decreases. Cross-linking G x and chain scission G s values of PLA revealed that chain scission reactions at lower dose predominate over cross-linking. DMA results exhibit an exothermal re-crystallization for neat and irradiated samples, which disappears with increasing heating rate. These results were confirmed by DSC measurements. Ductile-brittle transition was determined as function of EB-dose and crosshead speed. A change of physico-chemical and mechanical properties was evidenced during application of a dose of 45 kGy. [ABSTRACT FROM AUTHOR]

• BCN was surface modified with two silane coupling agents. • Composites exhibited excellent properties before and after gamma irradiation. • The performance of composites can be improved by improving the interfacial compatibility. • Modified BCN could weaken oxidative degradation of EP under γ irradiation. Polymer matrix composites reinforced with boron nitride (BN) have attracted much attention in the nuclear industry due to their attractive properties. Nevertheless, the performance of such composites largely depends on matrix–filler interactions. Herein, carbon-doped boron nitride (BCN), modified by two silane coupling agents, was used to fabricate epoxy composites, and the effect of gamma irradiation on the properties of epoxy resin composites was investigated. The research showed that the modified BCN/epoxy composites prepared herein exhibited excellent mechanical and thermal properties before and after gamma irradiation. The tensile strength of the composites increased up to 63.1 MPa at 0.5 wt % loadings compared to neat epoxy (54.7 MPa). After irradiation at 900 kGy, the tensile strength of the composites was 32.5% higher than that of neat EP. This improvement was ascribed to the excellent compatibility of the modified BCN and epoxy. Moreover, the char yield and the glass transition temperature significantly increased with incorporation of modified BCN before and after irradiation. The mechanism for the enhanced performance was that the barrier consisting of BN protected the matrix from further oxidative degradation. This study suggested that functionalized BN more effectively enhanced epoxy properties before and after irradiation. [ABSTRACT FROM AUTHOR]

• Successful synthesis of aliphatic aromatic co-polyesters with C6-C16 even carbon long chain dicarboxylic acid as monomer. • Effects of aliphatic segment length and content on different properties. • The unique crystallization behavior is caused by sufficient chain length and aliphatic content. • Biodegradation mechanism of aliphatic aromatic co-polyesters with long chain dicarboxylic acid as monomer. • The introduction of long enough aliphatic segments has a positive effect on biodegradation. In this work, dimethyl terephthalate (DMT), 1,4-butanediol (BDO) and different diacids were introduced to investigate the effects of variations in aliphatic chain length and component content in aliphatic aromatic terpolymers on the basic thermal properties, crystalline morphology, mechanical properties and biodegradability of the polyesters. The experimental results from nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR) and Gel permeation chromatography (GPC) indicate the successful synthesis of the anticipated aliphatic aromatic co-polyesters. The variation of melting and crystallization temperatures with aliphatic chain segment length and content were analyzed by differential scanning calorimetry (DSC). The Wide-angle X-ray diffraction (WAXD) results suggest that the coexistence of both crystals formed by rigid and flexible chain segments can be achieved by varying the length and component content of the aliphatic chain segments in the co-polyesters. The scanning electron microscopy (SEM) and composting experiment results indicate that the type of crystals formed with the more flexible chain segments and the lower degree of crystallinity have a positive effect on the biodegradability. [ABSTRACT FROM AUTHOR]

The extent of the hydrolytic degradation of aliphatic polyurethane (PU) films made from polycarbonate-based aliphatic macrodiol (MD), diisocyanate-1,6-hexane, butane-1,4-diol (BD) and d , l -lactide-based oligomeric diol (DLL) was tested in phosphate-buffered saline (PBS) for a period of up to 12 months. Two macrodiols of equal molecular weight (∼2000 Da), differing in chain composition and regularity, and equal MD-to-BD-to-DLL molar ratios were chosen for the PU synthesis. The isocyanate-to-total hydroxyl group ratio was kept constant at 1.05. The functional properties of raw four-component polyurethane films and samples immersed for 1, 3, 6, 9 and 12 months in a model physiological environment (37 °C, pH = 7.4) were studied from the segmental up to the macroscopic level. Tensile testing and water uptake experiments, as well as DSC, SEM, AFM, FTIR and WAXD analyses, were used for the comprehensive characterization of the raw and PBS-treated films. The study shows that the untreated four-component PU films are highly elastomeric materials with very high tensile strength and suitable thermal properties for potential medical coating/film applications. The DLL oligomeric diol turned out to be a very efficiently degradable unit, leading to substantial mechanical property deterioration. The products of more regular macrodiol have higher tendency to the degradation process; 89% or 94% of the original toughness value is lost in just 12 months of immersion. The studied type of PU can be practically used either as fairly stable high-performance elastomers for short-term applications (up to 3 months) or as degradable materials, when the time of exposure to the physiology-mimicking conditions is sufficient. [ABSTRACT FROM AUTHOR]

Developing halogen-free and phosphorus-free flame retardants with good processing characteristic for heat-resistant polymers is still a great challenge. A unique multi-maleimide terminated branched polysiloxane (PMI-HSi) was synthesized, which is liquid, reactive and does not volatilize, overcoming the disadvantages of available liquid flame retardants. PMI-HSi was added into bismaleimide/diallyl bisphenol A (BD) resins to prepare a series of modified resins (PMI-HSi/BD), which were found to have desirable flame retardancy and remarkably increased mechanical properties while maintaining outstanding thermal resistance. For the PMI-HSi/BD resin with 15 wt% PMI-HSi, its impact and flexural strengths are more than 1.8 and 1.3 times of those of BD resin, respectively, while the initial decomposition and glass transition temperatures are severally as high as 399 °C and 316 °C. Attractively, a small addition of PMI-HSi effectively increases limited oxygen index, greatly reduces the risk of catching fire and combustion intensity, and remarkably decreases the smoke production, demonstrating that PMI-HSi is a multi-functional flame retardant. The origin behind these attractive properties was revealed. [ABSTRACT FROM AUTHOR]

The hydrolytic stability of all-aliphatic polyurethane (PU) films made from polycarbonate-based aliphatic macrodiols (MD), diisocyanate-1,6-hexane and butane-1,4-diol (BD) were tested at 37 °C in phosphate buffer for a period up to 12 months. Two macrodiols, differing in composition and chain regularity and two MD-to-BD ratios were chosen for PU synthesis. The isocyanate-to-total hydroxyl ratio was kept constant and equal to 1.05. The functional properties of the original polyurethane films and films being immersed for 1, 3, 6 and 12 months in model physiological environment (37 °C at pH = 7.4) were studied on segmental up to macroscopic levels. The combination of SEM, AFM, FTIR, DSC, tensile and swelling analyses were used. It was found that prepared PU films are very good elastomeric materials with outstanding mechanical and suitable thermal properties keeping these properties practically unchanged for a period of up to 12 months. They can be practically used for example as strong and durable topcoats. [ABSTRACT FROM AUTHOR]

Polybutadiene (PB)–SiO 2 nanoparticles were successfully synthesized via differential microemulsion polymerization. The core-shell structured PB-SiO 2 nanoparticles were designed to achieve a monodispersion with reduced nanosilica aggregation. A high monomer conversion (81.5%), grafting efficiency (78.5%) and small particle size (27 nm) with narrow size distribution was obtained under optimum reaction conditions when using an extremely low surfactant concentration, 5 wt% based on monomer. The PB-SiO 2 latex could be hydrogenated by diimide reduction in the presence of hydrazine and hydrogen peroxide to provide hydrogenated polybutadiene (HPB)–SiO 2 . A high hydrogenation degree of 98.6% was achieved at a ratio of hydrazine to hydrogen peroxide of 0.75:1, and showed a maximum degradation temperature of 469.6 °C resulting in excellent thermal stability. A new nanocomposite of PB-SiO 2 and HPB-SiO 2 could be used as a novel nanofiller in natural rubber. Especially, NR/HPB-SiO 2 composites had improved mechanical and thermal properties, and exhibited good resistance toward ozone exposure. [ABSTRACT FROM AUTHOR]

A series of novel polydimethylsiloxane (PDMS) composites were prepared using polyvinylsilsesquioxanes (PVS) as reinforcing agent by hydrolytic condensation in the presence of organotin catalyst for the first time. The cross-linked network, morphology, thermal behavior and mechanical properties of these novel PDMS composites were examined by attenuated total reflection infrared spectroscopy (ATR-IR), scanning electron microscope (SEM), thermogravimetric analysis (TGA) and universal tensile testing machine, respectively. Experimental results showed that both thermal and mechanical properties of the PDMS composites were improved greatly by adding PVS. The prominent improvements in thermal and mechanical properties were likely attributed to the reinforcing interaction of PDMS chains and formed particles resulted from PVS self-crosslink. Meanwhile, we also found that with the increment in loading PVS, the resistance to thermal degradation of the PDMS composites in nitrogen atmosphere was enhanced obviously, but their resistance to thermal oxidation in air was not improved apparently. The unobvious improvement in resistance to thermal oxidation of the novel composites was likely due to the catalysis of oxygen. [ABSTRACT FROM AUTHOR]

Elastomeric ablative composites for ultrahigh temperature applications were processed and characterized to elucidate the potential of short carbon fibers (SCF) to tailor the thermo-mechanical and ablation characteristics of acrylonitrile butadiene rubber (NBR) composites. SCF was dispersed within NBR using dispersion kneader and two roller mixing mill. Ablation and thermal properties versus back-face temperature elevation during oxy-acetylene flame test, linear/radial ablation rates, percent char yields, insulation index, and thermal conductivity of the fabricated ablatives were measured. Experimental results revealed that the thermo-mechanical and ablation characteristics were significantly improved with increasing SCF concentration in the presence of coupling agent. Improvement in tensile strength, hardness and reduction in elongation at break were obtained with increasing SCF to matrix ratio. The microscopic analysis of the tensile fracture and ablation specimen showed the porosity generation during ablation and uniform dispersion of the impregnated SCF in NBR. [ABSTRACT FROM AUTHOR]

Abstract: In this article, two types of poly (d-lactide)-b-poly (ethylene glycol)-b-poly (d-lactide) (PDLA-b-PEG-b-PDLA) were added into PLLA matrix by solution casting method. The obtained films were characterized by wide-angle X-ray diffractomery (WAXD), differential scanning calorimetry (DSC), tensile testing and thermal gravimetric analyzer (TGA). Results indicated that the heat resistance of these blends could be improved when the amount of copolymer exceeded 30 wt%, because the high melting point stereocomplex was preferentially formed at that addition amount, whenever from solutions or from melt. Both the tensile strength and elongation at break of the blends were enhanced when 30 wt% copolymer was added, which were partly caused by the synergistic effects of stereocomplexation between enantiomeric PLAs and plasticization of PEG blocks. The blends showed higher thermal stability than neat PLLA at temperature above 370 °C. These results showed that the toughness and heat resistance of PLLA were improved, which made the application of PLA probable. [Copyright &y& Elsevier]

Abstract: We have investigated the influence of talc on the rheological, chemical, thermal and mechanical properties of polypropylene (PP)/talc composites (talc content was 0 wt.%, 10 wt.% and 20 wt.%) during multiple re-extrusions. In particular, the materials were extruded and re-extruded after a mechanical grinding of the extrudates for up to six times and then injected to make tensile sample. The main results show the reprocessing of the blends induced thermo-mechanical degradation by chain scission without significant oxidation. Re-extrusion induced a significant decrease of talc particles size and an increase of their aspect ratio. This mechanism caused an increase of rigidity whose intensity increased with the content of talc, and overcame the loss of rigidity due to the thermo-mechanical degradation of PP. The yield stress was stable for PP/talc 80/20 (20 wt.% talc) but increased for PP/talc 90/10 (10 wt.% talc) with the re-extrusion number, while that of neat PP increased for the first re-extrusion and then decreased for higher number of re-extrusions. Therefore, talc has a positive effect on the mechanical properties of PP/talc composites during re-extrusion. [Copyright &y& Elsevier]

Abstract: Poly(lactic acid) (PLA) based high performance nanocomposites, were prepared using an innovative combination of nanocrystalline cellulose and silver nanoparticles. Binary and ternary systems were prepared by solvent casting process and their morphological, mechanical and thermal responses were investigated. Pristine (CNC) and surfactant modified cellulose nanocrystals (s-CNC) and silver (Ag) nanoparticles were used, and the effect of cellulose crystal nano-dimension, cellulose modification, and the combination of cellulose nanostructures with silver nanoparticles, was investigated. The important industrial problem of slow crystallization of PLA was addressed by the use of cellulose nanocrystals as biobased nucleating agents and the nonisothermal cold crystallization behaviour of reinforced binary and ternary systems was studied. The presence of surfactant on the nanocrystal surface favoured the dispersion of CNC in the PLA matrix while the thermal investigations and the nonisothermal crystallization studies underlined the ability of s-CNC to act as nucleation agent in both binary and ternary nanocomposites. [Copyright &y& Elsevier]

Abstract: Biodegradable PLA composites were prepared using microcrystalline cellulose (MCC) and silver (Ag) nanoparticles. The main objective of the present study is to develop new biopolymer composites with good mechanical properties, thermal stability, maintaining the optical transparency and also providing antimicrobial properties through silver nanoparticle introduction. Composites were prepared with 1%wt of Ag nanoparticles and 5%wt of MCC using a twin-screw microextruder; film parameters were optimized in order to obtain a thickness range between 20 and 60μm. PLA composites maintained optical transparency properties of the matrix, while MCC was able to reduce polymer permeability. Thermal analysis revealed that MCC increased PLA crystallinity and the mechanical properties of the composites demonstrated that tensile modulus was improved by microcrystalline cellulose. [ABSTRACT FROM AUTHOR]

Abstract: Talc-loaded isotactic polypropylene (iPP) composites with various contents of talc were fabricated by compression molding, following slow- and fast-cooling processes, to obtain slow-cooled samples (SCS) and fast-cooled samples (FCS), respectively. Lamellar thickness of the α-crystal of iPP in the SCS is observed to be larger than that in the FCS by X-ray diffraction study. Rolled fast-cooled samples (RFCS) were also prepared at 25 °C in order to examine the crystal growth of iPP. An epitaxial growth mechanism of the α-crystal of iPP from the talc crystal is proposed. Surface of talc-loaded FCS appears with a smaller particle size than that of talc-loaded SCS and RFCS as observed by a scanning electron microscope. Young’s modulus and tangent modulus of FCS are found lower than those of SCS with the addition of talc up to 20 wt% and higher above this concentration, except microhardness which is higher in SCS at all contents of talc. From thermal studies, talc-loaded SCS and FCS are found to show higher melting temperature than the neat samples. Effect of cooling and rolling on the structures and properties of the fabricated composites are elaborately discussed. [ABSTRACT FROM AUTHOR]

Abstract: Composites have been produced by melt-blending biodegradable polylactide (PLA) with commercially available expanded graphite (EG). Using different techniques of addition, the manifold effects of EG on PLA molecular, thermo-mechanical and fire-retardant properties were evaluated. The EG nanofiller provides PLA composites with competitive functional properties. They have a high rigidity, with Young''s modulus and storage modulus increasing with EG content. They also have excellent thermal stability while preserving the glass transition and melting temperature of the original PLA matrix. Purification and pre-dispersion of EG nanofiller proved beneficial for preserving PLA molecular weights and led to improved mechanical performance. The presence of dispersed graphene nanolayers in PLA significantly accelerated the polyester crystallization process. The flame retardant properties also displayed improvements with a large decrease in the maximum rate of heat release as recorded by cone calorimetry, whereas the horizontal burning test (UL94 HB) was successfully passed revealing non-dripping and char formation. [Copyright &y& Elsevier]

Abstract: The mechanical, thermal and biodegradable properties of poly(d,l-lactide) (PDLLA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(ethylene glycol) (PEG) blends were studied. The influence of PEG on the tensile and impact strengths of the blends was investigated. The results showed that the toughness and elongation at break of the PDLLA/PHBV (70/30) blends were greatly improved by the addition of PEG, and the notched Izod impact strength increased about 400% and the elongation at break increased from 2.1% to 237.0%. The thermal and degradation properties of the blends were investigated by differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA), it was found that the thermal stability of PHBV in the presence of PDLLA was improved. The degradation test showed that the addition of PEG could notably accelerate the biodegradation of the blends in the soil at room temperature, and the mass loss is about 20% after 30 days of the storage. [Copyright &y& Elsevier]

Abstract: An experimental study was carried out in order to check the influence of various parameters on the ageing of PLA filaments performed in a climatic room. Initially, two grades of PLA with different d-isomer contents were analysed. Even after several weeks of ageing, properties of PLA filaments with less than 0.5% d-isomer content did not vary extensively. On the other hand, the mechanical and thermal properties of PLA filaments with 4% d-isomer content underwent strong modifications. Subsequently, a selected organomodified bentonite (Bentone®104 – noted as B104) was blended with PLA and then melt-spun to study the influence of a nanofiller on the ageing of PLA filaments. Faster degradation of PLA nanocomposite filaments was then observed. [Copyright &y& Elsevier]

Abstract: The influence of nano-silica, synthesized and mixed with low-density polyethylene (LDPE) through a sol–gel process, on the thermal and mechanical properties of LDPE and LDPE/wood flour (WF) composites, prepared in the absence and presence of dicumyl peroxide, was investigated. Scanning electron microscopic (SEM) analyses show a uniform dispersion of silica nano-particles of size 10–50nm in the matrix, and Fourier-transform infrared (FTIR) spectroscopic results indicated interaction between the nano-silica and the LDPE matrix, which seems to improve for samples prepared in the presence of dicumyl peroxide (DCP). WF and nano-silica, as well as the presence of DCP during sample preparation, substantially improve the thermal stability of the LDPE matrix. The tensile strength of the samples decreased with increasing wood flour content, while the tensile modulus substantially increased. The presence of nano-silica gave rise to lower values for both tensile strength and tensile modulus, while higher tensile strength (and an increase in tensile strength with WF content) is observed for samples prepared in the presence of DCP. The tensile modulus increases with increasing WF content, but is not substantially influenced by the presence of nano-silica or by sample preparation in the presence of DCP. The DMA results were in line with the tensile results. [Copyright &y& Elsevier]

Abstract: Novel hydrogel membranes (coded as GA) based on cationic guar gum (CGG) and poly(acrylic acid) (PAA) were synthesized with various feed compositions. Their structure and properties were studied by Fourier transform infrared spectra, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analyses and tensile tests. The structure analyses indicated that there existed strong electrostatic interaction between CGG and PAA, which resulted in uniform structure and complete miscibility between the two components. On the basis of thermogravimetric analyses, the activation energies (E a) of the first degradation of the membranes increased from 34.5 to 77.1kJ/mol with an increase of CGG content, while the residual ratios of the membranes increased from 7.6 to 36.1wt% at 600°C. This indicated an elevated thermal stability of PAA-based materials through an introduction of CGG. The tensile tests exhibited the mechanical properties of the membranes were improved with an increase of CGG content, and the maximum value of 41.1MPa was reached. [Copyright &y& Elsevier]

Abstract: A reactive phosphorus-containing compound, bis-phenoxy (3-hydroxy) phenyl phosphine oxide (BPHPPO) was first successfully synthesized to produce the phosphorus-containing flame retardant epoxy resin (BPHPPO-EP). The chemical structures were characterized from FTIR, MS, NMR spectra and elemental analyses. Thermal degradation behaviors and flame retardant properties of the cured epoxy resins were investigated from the thermogravimetric analysis (TGA) and the limiting oxygen index (LOI) test using 4,4′-diaminodiphenylsulfone (DDS) as curing agent. The high char yields and the high limiting oxygen index values were found to certify the great flame retardancy of this phosphorus-containing epoxy resin. [Copyright &y& Elsevier]

Abstract: Agar films were subjected to natural weathering exposure in a humid tropical climate for 90 days to determine their biodegradation behavior and functionality. Exposed samples were taken at 15, 30, 45, 60 and 90 days. Mechanical, thermal, structural and morphological properties were determined using tensile test, differential scanning calorimetry (DSC), attenuated reflectance infrared spectroscopy (ATR-FTIR), X-ray diffraction and environmental scanning electron microscopy (ESEM). The photodegradation process and temperature–relative humidity fluctuations promoted a decrease in agar mechanical properties in early exposure stages (30–45 days) caused by a reduction in agar molecular size and a decrease in the number of sulfate groups. These changes alter agar crystallinity, causing contraction that leads to formation of micro-fractures and embrittlement, and promote microbial attack. Accelerated weathering exposure of agar films showed that outdoor climate parameters play an important role in their degradation. These results will aid in further research to determine the potential use of agar as an environmentally friendly solution to the problem of biodegradable composites disposal. [Copyright &y& Elsevier]

Abstract: The thermal and mechanical properties of collagen/chitosan blends before and after UV irradiation have been investigated using thermal analysis and mechanical (Instron) techniques. Comparisons were made with the thermal and mechanical properties of both collagen and chitosan films. Air-dried collagen, chitosan and collagen/chitosan films were exposed to UV irradiation (wavelength 254nm) for different time intervals. Thermal properties of collagen/chitosan blends depend on the composition of the blend and are not significantly altered by UV irradiation. Mechanical properties such as ultimate tensile strength and ultimate percentage of elongation were much better for collagen films than for collagen/chitosan films. The results have shown that the mechanical properties of the blends were greatly affected by the duration of UV irradiation. Ultimate tensile strength and ultimate percentage elongation decreased after UV irradiation of the blend. Increasing UV irradiation leads to an increase in Young''s modulus of the collagen/chitosan blend. [Copyright &y& Elsevier]

Abstract: The photochemical reaction of poly(ether ether ketone) (PEEK) sheets under tensile loads has been investigated. Two types of UV irradiation tests were carried out in a vacuum environment: with and without a cooling apparatus. Chemical structures, thermal properties, and mechanical properties were measured to clarify photo-deterioration. Chemical analysis based on Fourier Transform Infrared Spectrometry (FT-IR) and X-ray Photoelectron Spectroscopy (XPS) showed photochemical scission caused by UV exposure. Thermal properties, measured by Differential Scanning Calorimetry (DSC), indicated that a crosslinking reaction occurred during the radiation tests. Tensile properties of PEEK sheets after UV radiation clearly showed a tendency to embrittlement affected not only by crosslinking but also by the orientation of molecular chains resulting from the temperature rise of the specimens. Furthermore, applied tensile stress during exposure accelerated molecular scission and disturbed the crosslinking effects of the tensile properties. [Copyright &y& Elsevier]

Abstract: A series of aliphatic homopolyesters and copolyesters was prepared from 1,4 butanediol and dimethylesters of succinic and adipic acids through a two-step process of transesterification and polycondensation. The synthesized polyesters were characterized by means of nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), viscosity measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and mechanical property measurements. The homopolymer poly(butylene succinate) exhibited the highest tensile strength, which decreased with increasing adipate unit content, passed through a minimum at copolyester composition close to equimolarity and then increased towards the value of poly(butylene adipate). It is interesting to note that in contrast to tensile strength, the elongation at break increased for adipate unit content of 20–40mol%. The biodegradation of the polymers was investigated by soil burial and enzymatic hydrolysis using three enzymes, Candida cylindracea lipase, Rhizopus delemar lipase, and Pseudomonas fluorescens cholesterol esterase. It appears that the key factor affecting material degradation was its crystallinity. [Copyright &y& Elsevier]

Abstract: Poly(butylene succinate-co-butylene adipate) was obtained from 1,4-butanediol and dimethyl esters of succinic and adipic acids through a two step process of transesterification and polycondensation. High molecular weight polyesters were synthesized using hexamethylene diisocyanate as chain extender. The effect of chain extension reaction time and chain extender content on polyester molecular weight, thermal and mechanical properties, was investigated. Polyesters were characterized by means of nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), viscosity measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD) and mechanical property measurements. Chain extension reaction had as a result the significant increase of polyester molecular weight leading to increased tensile strength. Polyester crystallinity, as calculated from XRD and DSC analysis, and melting temperature decreased upon chain extension, while glass transition temperature increased. Polyester biodegradation was investigated by soil burial and enzymatic hydrolysis using the enzyme Pseudomonas fluorescens cholesterol esterase. It appears that biodegradation was affected by polyester crystallinity, rather than by its molecular weight. [Copyright &y& Elsevier]

Abstract: Poly(methyl acrylate)/ZnAl layered double hydroxide intercalated nanocomposite (PMA/OZnAl-LDH NANO) was synthesized by in situ bulk polymerisation of methyl acrylate (MA) with an organo-modified ZnAl-LDH (OZnAl-LDH). After the in situ bulk polymerisation of MA, the basal spacing of OZnAl-LDH in PMA/OZnAl-LDH NANO increases to 2.85nm from 2.63nm of pristine OZnAl-LDH, which confirms the intercalation of PMA into OZnAl-LDH to form the intercalated nanocomposite. The transmission electron microscopy image shows that most of the OZnAl-LDH layers are stacked with about 3nm spacing while some of them are exfoliated and dispersed randomly in the PMA matrix. The tensile strength of the obtained nanocomposite dramatically increases due to the physical interaction between the layers of OZnAl-LDH and PMA chains. If measured at 10% weight loss, the decomposition temperature of PMA/OZnAl-LDH NANO with 5wt% OZnAl-LDH is about 17°C higher than that of pure PMA or PMA/OZnAl-LDH microcomposite with 5wt% OZnAl-LDH due to the strong interactions between the nanolayers of OZnAl-LDH and PMA chains. In the high temperature range, PMA/ZnAl-LDH has 39wt% residues at 400°C, which is 26wt% higher than pure PMA. This is because the char with inorganic compounds is much stronger in retaining the polymer than that without inorganic compounds. [Copyright &y& Elsevier]

BAK poly(ester amide)s with different adipic acid/terephthalic acid ratios have been synthesized and characterized considering spectroscopic data and both thermal and mechanical properties. Degradability under different media (water at 70 °C, acid or enzymatic catalysis) has also been studied by evaluating the changes in intrinsic viscosity, in the NMR spectra and in the surface texture of samples. The results indicate a decrease in the degradation ratio and an increase in chain stiffness as the content on the terephthalic units increases. Thermoenzymes such as Bacillus stearothermophilus are highly effective for the degradation of aromatic derivatives. [Copyright &y& Elsevier]

The influence of the wax content and different concentrations of the crosslinking agent on the thermal and mechanical properties of linear low-density polyethylene–wax blends has been investigated. It was found that an increase in wax content induces an increase in elastic modulus and yield stress of the blends. This is a consequence of the higher crystallinity of the blends in the presence of a higher amount of wax. The average tie chain concentration in the blends is estimated in order to explain detrimental effects of the wax on the ultimate properties. A significant correlation was found between stress and strain at break and the concentration of tie chains. Cross-linking improves the ultimate properties of the blends and pure polyethylene. On the other hand, because of its low molecular weight, thermal stability decreases with an increase in wax content and this trend remains unchanged after crosslinking. [Copyright &y& Elsevier]

Biodegradable aliphatic poly(butylene succinate-co-ethylene succinate) PBES and poly(butylene succinate-co-diethylene succinate) (PBDEGS) were synthesized from succinic acid and 1,4-butanediol/diethylene glycol through a direct polycondensation with titanium tetraisoproxide (TTP) and diphenylphosphinic acid (DPPA) as the co-catalysts. GPC and NMR results indicated molecular weight Mn higher than 5.0×104 and 6.5×104 for the PBES and PBDEGS copolymers respectively, with ES/DEGS populations spanning the whole comonomer composition, and the BS and ES sequence distributions were found to be in close agreement with the random model. DSC analyses revealed that thermal and crystallization behaviour strongly depended on the corresponding comonomer composition for the PBES and PBDEGS copolymers, and that PDEGS was an amorphous poly(ester-ether). For thermal stability, TGA results indicated that thermal stabilities of the prepared PBDEGS significantly decreased with increasing the DEGS unit composition, while there was no remarked decrease detected for those of the PBES copolyesters. In addition, measurements of mechanical properties showed that incorporation of a small amount of ether groups into the DEGS unit could more remarkably improve the elongation behaviour of the semi-crystalline copolymer than that of the ES unit, and much larger elongation rates were exhibited for the copolymer samples bearing 47, 78 mol% ES and 8, 28 mol% DEGS. [Copyright &y& Elsevier]

• A ground atomic oxygen exposure test was taken on cyanate-based shape memory polymer, a promising space deployment structure material. • The atomic oxygen dose is probably equivalent to the cumulative dose of 5 years LEO flight. • The damage resulting from atomic oxygen erosion was only on the surface and had little effect on the mechanical performance or shape memory behavior of the as-prepared cyanate-based shape memory polymer. As a new kind of smart material with shape changing and fixing abilities, the shape memory polymer (SMP), has become a research hotspot for space deployment structures in recent years. In fact, studying the space environmental adaptability of SMPs is an urgent research task, promoting their application in the aerospace field. In this study, a chemical crosslinked cyanate-based SMP (T g ~ 206°C) was exposed to atomic oxygen in a ground simulation system. The irradiation effects of atomic oxygen were investigated in terms of microscopic morphology, chemical structure, thermal stability, mechanical properties, loss factor and the storage modulus. After exposure to atomic oxygen, the cyanate-based SMP showed obvious surface erosion. When the irradiation dose reached 1022 atoms/cm2, the surface was entirely peeled off, and a new uneven surface emerged. However, the damage resulting from erosion was only on the surface and had little effect on the mechanical performance or shape memory behavior. The tensile strength and elastic modulus remained nearly constant at 66 MPa and 2000 MPa, respectively. Further, the effect of sample thickness and depth of delamination should be comprehensively considered in practical applications. The shape memory properties remain excellent after atomic oxygen irradiation, and the average shape fixity and shape recovery rates were 98.2% and 99.3%, respectively. [ABSTRACT FROM AUTHOR]

• Dehydroabietic acid-modified glycidyloxypropyltriethoxysilane (DAG) was used as cross-linking agent. • Nanofiller SiO 2 was incorporated into the RTVSR to enhance the properties. • The synergistic effect of DAG and SiO 2 can effectively improve the mechanical properties. • The SiO 2 -DAG/RTVSR exhibits better performances than pure RTVSR. Room temperature vulcanized (RTV) silicone rubber shows many excellent properties, but its applications are limited due to the poor mechanical properties. To improve the mechanical properties of RTV silicone rubber, dehydroabietic acid-modified glycidyloxypropyltriethoxysilane (DAG) was firstly used as the cross-linking agent to select a best DAG modified RTV silicone rubber with higher tensile strength of 0.65 MPa (DAG/RTVSR). Then different amount SiO 2 was added to prepare the SiO 2 reinforced DAG/RTVSR and further enhance the properties. The micro- morphology of RTVSR, DAG/RTVSR, and SiO 2 -DAG/RTVSR confirmed the uniform dispersion of DAG and SiO 2 , which results a well chain entanglement and increasing intermolecular interaction. Then, SiO 2 -DAG/RTVSR exhibit an obvious improvement of mechanical properties and thermal stability compared with unmodified RTVSR and DAG/RTVSR. This work indicates that the mechanical properties and thermal stability of RTV silicone rubber can be effectively enhanced by the synergistic effect of rosin derivative DAG and SiO 2. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Hygrothermal conditioning on the chemical, thermal and mechanical properties of aliphatic polyketone terpolymer, ethylene-propylene-carbon monoxide (EPCO), were investigated under high temperature fluid transport conditions. The DSC results suggest the effect of hygrothermal treatment and exposure time on the advancement of chain scission leading to an increase in crystallinity induced by chemi-crystallization, which was confirmed by FTIR results. TGA results of EPCO correspond to reductions of thermal stability with decreases in T 5% and T max characteristic temperatures by 19% and 10%, respectively. The yield stress, stiffness and dynamic storage modulus increased with degradation time. However, decreases in the elongation at break were observed after prolonged periods of degradation due to the embrittlement resulting from polymer chain scission. • Prolonged hygrothermal degradation of Polyketone results to chain scission phenomenon. • Thermal stability declines with increased in hygrothermal degradation conditioning. • Mechanical property and performance declined arising from changes in crystallinity. • Prolonged degradation retained better mechanical properties at elevated temperatures from dynamic mechanical tests. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of short jute fibers on the hydrolysis of poly (lactic acid) (PLA) in deionized water at 50 and 60 °C. The water absorption, thermal and mechanical properties (tensile and flexural), morphological structure, as well as molecular weight of jute/PLA composites and PLA were evaluated before and after aging. The results showed that the jute/PLA composites had higher water absorption but approximately equal mechanical properties compared with PLA. This indicates that it is a feasible way to reinforce PLA by adding short jute fibers. Both PLA and jute/PLA composites undergo hydrolysis after aging. Further analysis revealed that as the vibration and mobility of PLA molecular chains were hindered by addition of jute fibers, jute/PLA composites had a slower decline in mechanical properties than PLA, and thus showed a slower hydrolysis. Moreover, the addition of jute fibers resulted in mechanical interlocking, which in turn increased the load carrying capability of jute/PLA composites. • The aging mechanisms of short jute fiber/PLA composites were systematically studied. • A novel method of extracting jute fibers from composite was proposed to analysis the crystallization of jute fiber. • Jute fiber hindered vibration and mobility of PLA molecular under hygrothermal condition. • The addition of jute fibers drastically delayed the hydrolysis of PLA. [ABSTRACT FROM AUTHOR]

α-1,3-Glucan is a linear homopolymer enzymatically polymerized from sucrose using recombinant glucosyl transferase J (GtfJ) enzyme. α-1,3-Glucan branched ester derivatives were synthesized from branched carboxylic acids and trifluoroacetic anhydride in a heterogeneous reaction. These derivatives showed unconventional thermal properties compared with other polysaccharide ester derivatives and oil-based plastics. The melting temperature (T m) of the α-1,3-Glucan branched ester derivatives increased in proportion to the side chain length, which has not been observed for other polysaccharide ester derivatives. In addition, isobutyrate ester derivatives (iso -branched ester derivatives) and pivalate ester derivatives (tert -branched ester derivatives) showed extremely high glass transition temperatures (T g) of 206 and 202 °C, respectively, which were much higher than those of commercial plastics, such as polyethylene terephthalate (PET: 69 °C) and polycarbonate (140 °C), and super engineering plastics, such as polyether ether ketone (PEEK: 142 °C). Furthermore, these two types of branched ester derivatives showed excellent thermoplasticity at temperatures below the thermal decomposition temperature. Therefore, α-1,3-Glucan branched ester derivatives demonstrate the possibility of realizing both high thermal stability and thermoplasticity. Image 1 • Fully substituted α-1,3-Glucan branched ester derivatives were synthesized. • α-1,3-Glucan branched ester derivatives showed extremely high glass transition temperatures of over 200 °C. • α-1,3-Glucan branched ester derivatives showed thermoformability at temperatures below the thermal decomposition temperature. • The melting temperatures of α-1,3-Glucan branched ester derivatives increased in proportion to the side chain length. [ABSTRACT FROM AUTHOR]