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This study investigates the impact of aging in methyl diethanolamine (MDEA) solution on cured rubber compounds comprising ethylene‐propylene‐diene monomer rubber (EPDM), butyl rubber (IIR), and blends, utilizing nano (nZnO) and conventional (ZnO) zinc oxides as curing activators. The analysis reveals that MDEA solution induces degradation in the rubber matrix by grafting amine and amide groups onto the rubber backbone, particularly affecting unsaturated units in diene monomers in EPDM and isoprene units in IIR. The Fourier‐transform infrared (FTIR) analysis validated the addition of these functional groups. Aging contributed to the formation of a thin rubber layer covering carbon black particles, likely due to un‐crosslinking and rubber chain scission, resulting in changes in bound rubber as observed in scanning electron microscopy (SEM) images. Tensile strength and elongation at break typically decreased with aging, with EPDM compounds exhibiting the highest initial tensile strength and IIR compounds demonstrating superior initial elongation. Hardness remains largely unaffected by aging. This study showed the detrimental effects of MDEA exposure on rubber compounds, emphasizing the critical importance of material selection and property tailoring for specific applications in MDEA‐rich environments, such as gas refineries. [ABSTRACT FROM AUTHOR]

Bioabsorbable poly(4‐hydroxybutyrate) (P4HB) electrospun membrane has been widely used in various biomedical applications due to its biocompatibility and unique mechanical properties. When commercialization is envisaged, a sterilization procedure aiming to prevent bacterial contamination of biomedical devices is indispensable. Herein, P4HB membranes were sterilized by using different sterilization techniques. It's observed that ethylene oxide (EO), ultraviolet radiation (UV), and electron beam (E‐beam) irradiation do not influence the morphology of fiber membranes. Analysis of the data revealed that E‐beam irradiation sterilization can induce chain scission of P4HB. The EO sterilization process can increase the melting point of P4HB electrospun membranes. None of the sterilization methods showed a significant effect on the hemocompatibility of the P4HB membranes. Furthermore, the cytocompatibility experiment indicated that none of the P4HB membranes had any toxic effects on L929 cells. Taken together, selecting a suitable sterilization method that effectively sterilizes and does less damage during the sterilization process is critical to P4HB membranes for biomedical application. [ABSTRACT FROM AUTHOR]

This study provides key insights into the extrusion of a post‐industrial feedstock primarily composed of polypropylene (PP) and reveals its influence on the property profile of the recyclate. The objective of this study was to gain a fundamental understanding of complex process‐property relationships. Therefore, a two‐part experimental design was established. The first part aimed to analyze the feedstock variability by investigating key material properties of recyclates produced under constant processing conditions. The second part aimed to systematically evaluate the effect of the screw speed, filtration setup, and degassing setup on the properties of the recyclates. An industrial‐scale recycling extrusion line was used. The material evaluation included melt mass‐flow rate (MFR), ash content, oxidation induction temperature, tensile and impact properties, degassing performance, and residual volatile organic compounds (VOCs). Higher melt temperatures led to chain scission of the PP fraction, resulting in increased MFR and higher material stiffness. Additionally, a finer filtration positively contributed to the enhanced material stiffness. Furthermore, the mechanical properties were also influenced by the levels of inorganic fillers in the material composition of the feedstock. Finally, the filtration setup had a greater impact on degassing performance and residual VOC levels than the degassing setup and screw speed. [ABSTRACT FROM AUTHOR]

High‐performance fibers are known for their exceptional specific strength and resistance to various hazardous conditions, including fire. However, the long‐term performance of these fibers when exposed to convective heat has rarely been reported. This study investigated the accelerated thermal aging behavior of three high‐performance fabrics of different blends of inherently flame‐resistant high‐performance fibers: copolymer of aramids (Technora®)/polybenzoxazole (PBO); para‐aramid/meta‐aramid; and para‐aramid/polybenzimidazole (PBI). Fabric specimens were thermally aged for up to 1200 h at temperatures ranging from 90 to 320°C. While all three fabrics experienced losses in the breaking force, the Technora®/PBO fabric displayed the best strength retention, despite the complete disappearance of the Technora® fiber crystallinity after aging at 320°C for 1200 h. The para‐aramid/PBI blended fabric showed signs of competing aging processes at high temperatures. An increase in the fabrics' crystallinity and evidence of chain scission were observed after thermal aging. Additionally, degradation in the fabric's water‐repellent finish was observed. The findings of this study will contribute to the development of more durable and safer protective gear, particularly for high‐risk activities like firefighting. [ABSTRACT FROM AUTHOR]

The evolution of plane-strain fracture toughness in highly cross-linked epoxies was assessed for different hygrothermal aging temperatures (25, 50, and 75°C) and durations (0–75 days). The absorption of water increased with hygrothermal aging, but at a diminishing rate and without saturating. A fraction of the absorbed water persisted despite prolonged drying. Thermogravimetric analysis revealed that the epoxy-decomposition temperature decreased with hygrothermal aging. 13C solid-state nuclear magnetic resonance spectroscopy indicated an increase in the de-shielding of carbon atoms in the vicinity of electronegative elements like oxygen with hygrothermal aging severity, indicating the development of intermolecular hydrogen bonding. X-ray photoelectron spectroscopy tracked the chemical bonding state of carbon by using a narrow scan on the C1s binding energy region. Upon hygrothermal aging, there was a decrease in C-C/C= C groups, indicating main chain scission through hydrolysis. A simultaneous increase in the C-O species indicates the formation of alcohols as hydrolysis reaction products. In this manner, retained water was involved in hydrogen bonding and chemical reactions with the epoxy. With increasing severity of hygrothermal aging, the fracture toughness decreased. This was consistent with fracture surface micrographs that showed a greater distance amongst crack stretch marks in specimens with less toughness. [ABSTRACT FROM AUTHOR]

The influence of different overlay layers (ABS, PC, and PLA) is investigated on the photodegradation behavior of poly(lactic acid) (PLA)-containing samples in double injection molding, and PLA/PLA samples serve as the control group. In terms of microstructure, an analysis is conducted on the chemical structure, thermal performance, crystallinity, and molecular weight of the base layer of samples. The carbonyl index and molecular weight of the base layer of PLA/PLA samples decrease rapidly, and the trend of crystallinity change is also fast. Among them, the number of molecular chain scissions decreases to 0.61, and the crystallinity increases to a maximum of 17.93%, which indicates that the photodegradation degree of the base layer of PLA/PLA samples is greater than that of the other two samples. The microscopic surface morphology change of the base layer of three PLA-containing samples is analyzed. The base layer of PLA/PLA samples becomes rougher after 600 h of UV degradation. Meanwhile, compared with other PLA-containing samples, the percentage of tensile strength loss of PLA/PLA samples is higher, decreasing by 16.64%. In summary, using acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) materials as overlay layers for double injection molding can mitigate the photodegradation of the base layer of PLA-containing samples in double injection molding. [ABSTRACT FROM AUTHOR]

Photolithography is a core part in microelectronic processes. This technological step implies the use of numerous hazardous carcinogenic compounds in the formulations, the use of solvents for processing synthetic polymers to obtain micro and nanostructures. We proposed the use of chitosan‐based biosourced water‐soluble resins to significantly reduce the environmental impact of the photolithography step, for 193 nm photolithography. We show in this report that chitosan‐based photoresist is suitable for microelectronic application, and in particular, we could significantly improve photosensitivity by adding a water‐soluble photoacid generator (PAG). UV–visible and Fourier transform infrared‐attenuated total reflectance characterizations reveal an increase of the macromolecular chain scission kinetics in the presence of PAG. Moreover, the local decrease of the pH favors the solubility of chitosan in irradiated areas. Finally, the photolithography tests demonstrate that the dose to clear and the optimal dose for photopatterning are divided by a factor of two. Moreover, the physical etching transfer tests show that the presence of PAG does not decrease the transfer performance, making these aqueous‐based formulated resins still more adapted for the fabrication of microelectronic devices. [ABSTRACT FROM AUTHOR]

Poly(2,6‐dimethyl‐1, 4‐phenylene oxide) (PPO) is a well‐known high heat‐resistant polymer and miscible with polystyrene. However, it is not miscible with many polymers containing polar groups. In the present study, PPO was nitrated to prepare a nitrated PPO (NPPO) containing polar nitro groups and blended with a copolymer of styrene/acrylonitrile (SAN). Dynamic mechanical analysis (DMA) data showed that NPPO in SAN‐rich phase was miscible with SAN, while NPPO in NPPO‐rich phase was partially phase‐separated from SAN, both over the entire blend composition range from NPPO wt. fractions of 0.1–0.5 investigated for this work. Analyses of Fourier‐transform infrared (FTIR) and ultra‐violet (UV–VIS) spectra indicated that the miscibility of NPPO with SAN was caused by intermolecular hydrogen bonding of CN group of SAN with OH end‐group of NPPO in the NPPO/SAN blends. NPPO's OH end‐group, meta‐nitro 2,6‐dimethyl phenol, was produced during nitration of PPO due to chain scission of aryl ether bond. Besides the intermolecular hydrogen bonding, dipole‐diplo interaction of the CN and nitro groups resulted in dissociation of the CN dimers and trimers to the CN monomers in the NPPO/SAN blends. [ABSTRACT FROM AUTHOR]

For biodegradable medical implants, it is critical to match the degradation rate of the material with the lesion healing rate of the tissue defect. Here, we report the synthesis of poly(L‐lactic acid) (PLLA)‐trimethylene carbonate (TMC)‐glycolide (GA) terpolymers with various monomer feeding ratios of L‐lactide, TMC, and GA. The terpolymers were prepared through ring‐opening polymerization with the purpose to improve degradation and mechanical properties of the terpolymers for biomedical applications. The influence of various GA contents in PLLA‐TMC‐GA terpolymers on the chain structure and their in vitro degradation performances were evaluated by using gel permeation chromatography, differential scanning calorimetry, X‐ray diffraction, 1H nuclear magnetic resonance, and tensile tests. Compared with pure PLLA, the degradation rate of terpolymers increased with the increase of GA content, because GA segments, which have a faster hydrolysis rate, not only effectively disrupt the regularity of LLA segment, but also increase the probability of chains scission during the degradation process. In a 28‐week long degradation study, the mass loss of PLLA‐TMC‐GA terpolymers was about 36%, which is a faster rate than reported for pure PLLA. Therefore, it is possible to tailor the copolymer chain structures by varying the ratio of GA in the terpolymer to balance its degradation rate with body's lesion healing rate. [ABSTRACT FROM AUTHOR]

Poly(butylene adipate‐co‐terephthalate) (PBAT) was functionalised with itaconic anhydride (IA) via melt grafting in a batch mixer, initiated by dicumyl peroxide (DCP). It was found that the ratio of IA to DCP is critical to avoid undesired side reactions, such as crosslinking and chain scission. PBAT and other polyesters with low aliphatic hydrocarbon content are relatively unreactive toward radical graft modification, providing relatively low degree of grafting. Using 2 wt% IA and 1.2 wt% DCP gave the highest degree of grafting (1%), with little indication of crosslinking or chain scission. The complex reaction mechanism of grafting presents a clear competition between grafting, homopolymerization, crosslinking, and chain scission. Using non‐isothermal kinetic modeling, it was shown that the reaction is not first order, and that models making this assumption leads to incorrect results. Using the Vyazovkin model‐free method, the effective rate constant was predicted over a typical melt processing temperature range. Low reagent concentration resulted in the lowest effective rate constant, and it was shown that the activation energy changes with conversion and is also affected by reagent concentration. [ABSTRACT FROM AUTHOR]

The pressure barrier is one of the layers that compose flexible pipes used for oil and gas exploitation. It is made from a thermoplastic that must endure harsh operation conditions keeping its properties during the projected lifetime. Polyamide 11 is used when operating temperatures are below 80°C. Although polyamides' aging chemical mechanisms are well established in the literature, their mechanical behavior is defined by deformation processes that, in turn, depend on the polymer molecular structure. The dominant aging mechanism, hydrolysis, has been used by industry as a parameter for lifetime evaluation. Different morphological arrangements may occur following chain scission depending on the operating environment, leading to line failure or unnecessary substitution. The complex combination of parameters affects the aging processes, chain scission, morphological changes, and, consequently, mechanical behavior. Understanding the role of environmental parameters such as pH, acidic content, among others, is crucial to improving the model used. In this context, this work evaluates the aging of PA11 in two fluids with different acid concentrations but the same pH. The goal is to assess the impact of the amount of acid molecules on the polymer structure at 120°C and quantify the aging of PA11 using acceptance criteria methods. [ABSTRACT FROM AUTHOR]

Fire‐protective clothing are manufactured using heat and flame resistant fibers that are made of high‐performance polymers. These polymers exhibit a gradual reduction in their performance after long‐term exposure under various aging conditions. This study investigates the thermal aging behavior of a high‐temperature resistance polymer, polyetherimide (PEI), at elevated temperatures in air. Changes in the ultimate tensile strength (UTS), glass transition temperature, and surface properties are observed. In addition, infrared spectroscopy identifies chemical bonds in PEI being consumed because of chain scission. Applying the time–temperature superposition principle to the UTS data gives an activation energy of 112 kJ mol−1 for the effect of thermal aging on the mechanical strength of PEI. This value is similar to what has been reported for fire‐protective clothing fabrics, which opens the possibility to use PEI as a sensing material for the development of end‐of‐life sensors for fire‐protective fabrics. [ABSTRACT FROM AUTHOR]

Polyphenylene sulfide (PPS) is a type of thermoplastic that has high thermal and mechanical performances and extensive applications. Before processing, pre‐curing is required to improve its processability and mechanical properties. Here, effects of curing temperature (245 and 260°C) and time (10, 30, 60, and 120 min) on structure and thermal‐mechanical behavior of PPS were studied through melt flow index (MFI), rheology, Fourier‐transform infrared spectroscopy, and thermal‐mechanical characterizations. The MFI was decreased from ~700 g/10 min to less than 100 g/10 min (315°C/5.0 kg) after 60 min of curing at two different temperatures, greatly improving the processability of PPS in melt extrusion and injection molding processes. The functional groups remained unchanged after curing, due to the main reactions of chain extension and scission that occurred. For the PPS cured both at 245 and 260°C, the samples cured for 10 min displayed the highest degree of crystallinity and heat deflection temperature but had the lowest glass transition temperatures. The coefficient of linear expansion of PPS cured at 260°C showed anisotropy on flow and normal directions, which greatly differed from the PPS cured at 245°C. This study promotes an improved understanding of the curing process for solid PPS. [ABSTRACT FROM AUTHOR]

The effects of electron beam (EB) radiation in thermoplastic elastomers based on SEBS/TPU and SEBS‐g‐MA/TPU are evaluated. 60/40 blend of both the systems were subjected to EB using an ILU type industrial accelerator. Radiation dose was varied from 0 to 100 kGy, and the sol–gel content evaluation along with detailed analysis of mechanical, thermal, rheological, and morphological implications was conducted. The interplay between crosslinking and chain scission was quantified using the Charlesby‐Pinner equation. Both the blends showed the presence of a three‐dimensional cross‐linked network in them after the irradiation. The tensile strength of SEBS/TPU was found to deteriorate with an increase in radiation dose, but an opposite trend was observed in SEBS‐g‐MA/TPU. Improvement in interfacial adhesion between SEBS‐g‐MA and TPU was confirmed. The morphological analysis through atomic force microscopy and scanning electron microscopy clearly showed the appearance of rough ridges and pits due to irradiation along with the cross‐linked networks. From differential scanning calorimetry analysis, the changes in glass transitions and melting endotherm were assessed. Thermogravimetric analysis results indicated an improvement in the thermal stability of the blends. The storage modulus and complex viscosity of the samples enhanced as perceived from the rheological measurements. X‐ray diffraction patterns of the blends also showed considerable variation after irradiation. [ABSTRACT FROM AUTHOR]

The effect of accelerated weathering degradation on the properties of poly(lactic acid) (PLA)/poly(ε‐caprolactone) (PCL) blends and PLA/PCL/titanium (IV) dioxide (TiO2) nanocomposites are presented in this paper. The results show that both polymers are susceptible to weathering degradation, but their degradation rates are different and are also influenced by the presence of TiO2 in the samples. Visual, microscopic and atomic force microsocpy observations of the surface after accelerated weathering tests confirmed that degradation occurred faster in the PLA/PCL blends than in the PLA/PCL/TiO2 nanocomposites. The X‐ray diffraction results showed the degradation of PCL in the disappearance of its characteristic peaks over weathering time, and also confirmed that PLA lost its amorphous character and developed crystals from the shorter chains formed as a result of degradative chain scission. It was further observed that the presence of TiO2 retarded the degradation of both PLA and PCL. These results were supported by the differential scanning calorimetry results. The thermogravimetric analysis results confirmed that that PLA and PCL respectively influenced each other's thermal degradation, and that TiO2 played a role in the thermal degradation of both PLA and PCL. The tensile properties of both PLA/PCL and PLA/PCL/TiO2 were significantly reduced through weathering exposure and the incorporation of TiO2. [ABSTRACT FROM AUTHOR]

Hindered amine light stabilizers (HALS) are widely used chemical stabilizers for preventing polymer degradation. In this study, the effects of type of HALS and its content in high‐density polyethylene (HDPE) over the stabilization process are investigated employing density functional theory (DFT) and experimental approach. The electrophilicity index of four types of commercial HALS are compared by DFT to select the most effective one. Besides, the HDPE sample containing a phenolic antioxidant and different contents of the selected HALS are experimentally exposed to UV irradiation. The effect of HALS content on the changes in chain microstructure and molecular weight of HDPE are evaluated using gel permeation chromatography and frequency sweep rheometry. In the absence of HALS, HDPE suffers degradation and the phenolic antioxidant causes chain scission. However, by adding HALS, the chain branching and crosslinking mechanisms are predominant. The results of FTIR, DSC, and tensile analyses follow similar trends, revealing that the best stabilization performance corresponds to adding 600 ppm HALS to HDPE. [ABSTRACT FROM AUTHOR]

The effects of the shapes and addition amount of crosslinking reagents on the expression mechanisms of polymer properties of poly(3‐hydroxybutyrate) (PHB) and poly(caprolactone) (PCL) blends are investigated. A static tensile test is carried out on 60%PHB/40%PCL blends by adding liquid and solid crosslinking reagents, showing that the Young's modulus of the blends decrease with increasing effective peroxide value of the crosslinking reagent. In addition, the elasticity of the blends increases only when the liquid crosslinker is added, even though T1H analysis and scanning electron microscopy observation reveal that both crosslinking reagents improve the miscibility of the blend. Furthermore, the 1H and 13C PST‐MAS NMR spectra related to the molecular motions of polymer main chains in the blends increase with increasing effective peroxide value of the crosslinking reagents. However, the local molecular motions of substituents in the blends matched with the T1C values reveal an opposite trend between the rigid PHB and flexible PCL with the addition of the solid crosslinker. The solid‐state NMR spectral and relaxation time analyses suggest the possibility of the polymer chain scission as a side reaction, as well as the occurrence of intra‐domain crosslinking, both of which reduce the toughness of the blends containing the solid crosslinker. [ABSTRACT FROM AUTHOR]

The performance of a series of thermooxidation stabilizers was investigated in poly(3‐hydroxybutyrate) (PHB) during processing by multiple extrusion at 190°C. The issue was to find out if PHB may be processing stabilized or not. Phenols of different steric hindrance, phosphites, amine oxide, hydroxylamine, lactone, hindered amine and carbodiimide were tested as potential stabilizers and their efficiencies compared with non‐stabilized polymer as a reference. Multiple extrusion data was evaluated using the processing degradation index (PDI) formerly designed for polypropylene. Changes in molecular weight were monitored as well. The results have shown that none of the stabilizing structures, currently successfully used in other polymers, have the ability to protect PHB. This indirectly implies that no radical chain scission takes place during PHB processing, i.e. no thermooxidation takes place. Moreover, nearly all of the tested structures act as prodegradants in PHB, some of them very strong. The strongest ones contain P or N atoms with asymmetrical free electron pairs in their molecules that evidently accelerate the main degradation mechanism of PHB—thermally induced cis‐elimination. [ABSTRACT FROM AUTHOR]

In this paper, the high value‐added (ultra‐low degree of polymerization [ULDP]) polyvinyl alcohol (PVA) product was successfully prepared by oxidative chain scission method with sodium hypochlorite as an oxidant. When the molar ratio of PVA to NaClO is not less than 1:1.8, the reaction is stirred for several hours (≥2 h) at a temperature not exceeding 50°C. After precipitation and washing in methanol, PVA with polymerization degree of 38–150 can be obtained after drying. The infrared spectrum (IR) and nuclear magnetic hydrogen spectrum (1H‐NMR) test proved that the product obtained by this method is indeed PVA. The results of 1H‐NMR also showed that the chain broken has no selectivity and the stereoregularity of hydroxyl group did not change significantly. Through radical quenching experiment and electron paramagnetic resonance (EPR) analysis, it is proved that OCl− is the main active oxide, ·Cl makes the oxidative chain scission process can be realized quickly, and ·OH is an indispensable factor for obtaining ULDP PVA. Under the combined action of these three, high value‐added PVA with ULDP was successfully prepared. Additionally, the sodium hypochlorite oxidized the ·OH captured by 5,5‐dimethyl‐1‐pyrroline‐n‐oxide (DMPO‐OH) to 2‐hydroxy‐5,s‐dimethyl‐1‐pyrroline‐N‐oxide (HDMPO‐OH) in an alkaline environment. [ABSTRACT FROM AUTHOR]

Polymer sintering is not only a well‐established procedure for producing functional polymeric parts, but it is also the basis for the relatively new additive manufacturing technique, selective laser sintering. Although studying the impact of thermo‐oxidative degradation during sintering has significant practical importance, few studies have focused on this aspect of the sintering process. In the present work, we have investigated the active thermo‐oxidative degradation mechanisms during sintering of high‐density polyethylene (HDPE) particles, the conditions that promote them, and their respective impact on the morphological evolution of the polyethylene particles. To perform a comprehensive study, we have complemented the rheological, thermal, chemical, and morphological analysis of the sintered HDPE particles with the study of their ensemble pore structure. We observed two distinct degradation regimes. At the beginning, the relatively low concentration of oxygen in the particles led to the dominance of branching and resulted in a pore structure evolution limited to surface relaxation. In the second regime and with the diffusion of more oxygen, chain scission became the dominant route. In this regime, the emergence of highly mobile short chains markedly accelerated the pore evolution. [ABSTRACT FROM AUTHOR]

The effect of exposure of polylactide (PLA) and poly(trimethylene carbonate) (PTMC) statistical copolymers to ionizing radiation was studied by means of EPR spectroscopy. In addition, the influence of radiation‐induced processes on thermal properties, miscibility of the components, weight average molecular weight (Mw) and number average molecular weight (Mn) were investigated for doses in the range of 0–200 kGy. In copolymers containing PLA and PTMC components in a ratio of 30:70 and 70:30 PLA radicals identified in the homopolymer under cryogenic conditions were dominant. This showed that PTMC radical centers either recombine or are transferred to PLA along the macromolecules. The results obtained for the non‐irradiated and irradiated samples showed that the glass transition values measured by differential scanning calorimetry and calculated using the Fox equation were similar and indicated compatibility between the constituents of the tested copolymers and their miscibility. Mw and Mn changes measured by gel permeation chromatography were used to determine the radiation yield of scission G(S) and cross‐linking G(X). In the case of PLA and PLA‐rich copolymers, the difference between G(S) and G(X) with increasing dose increased, thus the chain scission predominated over cross‐linking. For PTMC rich copolymer, the effect was opposite. [ABSTRACT FROM AUTHOR]

Perfluorosulfonic acid ionomer membranes have been widely used as proton conducting membranes in various electrochemical processes such as polymer electrolyte fuel cells and water electrolysis. While their thermal stability has been studied by thermogravimetry and analysis of low molecular weight products, their decomposition mechanism is little understood. In this study a newly developed methodology of thermal desorption and pyrolysis in combination with direct analysis in real time mass spectrometry is applied for Nafion membrane. An ambient ionization source and a high‐resolution time‐of‐flight mass spectrometer enabled unambiguous assignment of gaseous products. Thermal decomposition is initiated by side chain detachment above 350°C, which leaves carbonyls on the main chain at the locations of the side chains. Perfluoroalkanes are released above 400°C by main chain scission and their further decomposition products dominate above 500 °C. DFT calculation of reaction energies and barrier heights of model compounds support proposed decomposition reactions. [ABSTRACT FROM AUTHOR]

In this study, density functional theory (DFT) and experimental study were conducted to investigate the photodegradation of PVC composites. The results indicate that chain crosslinking, chain scission, dehydrochlorination, and photooxidation are suppressed, while the tensile strength retention of PVC composite reaches a maximum with the incorporation of polybenzimidazole (PBI) and polyacrylic acid modified carbon black. The allyl group can obviously reduce Gibb's free energy (∆G) of PVC in attack by triplet state oxygen (3O2), and photooxidation of PVC is accelerated in the presence of PBI due to the photogeneration of singlet state oxygen (1O2). Photodegradation of PBI was also studied by UV–vis spectroscopy and matrix‐assisted laser desorption ionization time‐of‐flight mass spectroscopy, while the possible photodegradation pathways of PBI were proposed. The disappearance of UV‐absorption of PBI in PVC matrix after 600 h UV‐weathering is probably related to the byproducts and molecular properties. [ABSTRACT FROM AUTHOR]

Blends of EPDM and chlorobutyl (CIIR) rubbers are used in nuclear plants where they have to withstand the combined effect of radiation and hydrocarbon aging. To improve their mechanical properties as well as hydrocarbon and gamma radiation resistance, the blends are reinforced with 0.5, 1, 1.5, and 2 phr of MWCNT. The increase in mechanical properties was highest for 1.5 phr MWCNT with 69% increase in tensile strength. The improvement in properties was correlated to MWCNT dispersion and filler–polymer interactions, which were confirmed by TEM and FTIR analysis. Hydrocarbon transport coefficients decreased on addition of MWCNT. The nanocomposites were exposed to 0.5, 1, and 2 MGy cumulative doses of gamma radiation. Depending on the radiation dose, crosslinking and/or chain scission occurred causes changes in physical properties. MWCNT reinforcement reduced the magnitude of changes in mechanical and transport properties after γ‐irradiation. ESR and FTIR spectra provided qualitative information on free radical formation and chemical changes due to γ‐rays exposure. To further enhance the properties, hybrid nanocomposites with 1.5 phr MWCNT and varying nanoclay contents (0.5, 1, 1.5, 2, and 5 phr) were prepared. Due to synergism between MWCNT and nanoclay, the hybrid composites had superior properties with hybrid containing 5 phr nanoclay giving 98% increase in tensile strength. [ABSTRACT FROM AUTHOR]

Hydrogels based on gamma (γ) irradiated chitosan (pre‐irradiated), guar gum, and polyvinyl pyrrolidone were crosslinked with various concentrations of (3‐mercapto propyl)trimethoxysilane and fabricated by solution casting technique for the drug delivery applications. High molecular weight chitosan (Ch) possesses lower solubility and higher viscosity, these problems overcame by γ irradiation, which also generated hydrophilicity and effect of irradiated Ch on controlled drug release was assessed. FTIR analysis showed the development of chemical and physical interactions and confirmed the incorporation of characteristic peaks. SEM micrographs revealed porous structure of the prepared hydrogels. Swelling analysis of the hydrogels was performed in distilled water, buffer, and electrolyte mediums. All the hydrogel samples showed higher swelling at acidic pH and lower swelling at neutral and basic pH. These pH‐responsive characteristics made these RCGP hydrogels an important contender for injectable controlled drug release. The ampicillin sodium drug was loaded and in vitro controlled release mechanism was evaluated in the PBS, SIF, and SGF which shown out of all prepared hydrogels (RCGP‐1, RCGP‐2, and RCGP‐3), RCGP‐1 has exhibited 87.4% release in PBS and 81.3% in SIF in 180 min. [ABSTRACT FROM AUTHOR]

Polytriazole polyethylene oxide‐tetrahydrofuran (PTPET) elastomer was prepared based on the click‐chemistry reaction between the CCH and N3 groups. The PTPET exhibits improved thermal stability with an activation energy of 204 kJ/mol compared with hydroxyl‐terminated polyethylene oxide‐tetrahydrofuran (PET) elastomer. TG‐FTIR and pyrolysis‐gas chromatography–mass spectrometry (Py‐GC–MS) were used to analyze the pyrolysis mechanism and products of the PTPET elastomer. The pyrolytic mechanism of PTPET mainly involves breakage of the polyether chains. The main pyrolytic products were identified. The PTPET underwent for 180 days at 50°C and 60°C. The tensile properties, dynamic mechanical analysis (DMA) and TGA of the aged PTPET were investigated. The tensile stress and strain of the aged PTPET increased until 120 days (at 60°C) or 150 days (at 50°C), which could be attributed to the postcuring of the elastomer. The scission of the PTPET chains due to aging could dominate after aging for 120 days (at 60°C) or for 150 days (at 50°C), resulting in the reduction of mechanical properties. [ABSTRACT FROM AUTHOR]

It has been a technical challenge of recycling tire rubbers due to the covalently crosslinked polymer network structure. Unlike conventional recombination of crosslinked SBR under thermal oxidation, SBR vulcanizate was efficiently degraded by thermal oxidation at 150 °C in presence of soybean oil, resulting in 47.3% sol fraction by weight. The structural evolution of SBR vulcanizates during thermal oxidation was characterized by sol–gel ratio, chemical structure, molecular weight, and oxidative erosion on the rubber surface. It was found that the continuous oxidation process facilitated main chain scission of SBR vulcanizates, resulting in a decrease of molecular weight of the sol fraction. The concentration of carbonyl groups, sol fraction, and surface erosion continually increased with reaction time. The large amounts of soybean oil significantly affect the thermal stability of SBR vulcanizates. Moreover, soybean oil is more efficient in decomposition of the SBR vulcanizates and results in more homogeneous and efficient oxidation reactions than paraffin oil. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48935. [ABSTRACT FROM AUTHOR]

The weathering stability of polymeric backsheets is very important for the reliability of photovoltaic (PV) modules. In addition to reliability, cost reduction and sustainability are upcoming challenges the PV backsheet industry is facing with. The most commonly used material for PV backsheets is poly(ethylene‐terephthalate)‐PET. However, PET is in general very sensitive to hydrolysis, which leads to chain scission and causes embrittlement, cracking, delamination, and dimensional instability of the backsheet. Compared to that newly developed modified polyolefin backsheets have favorable selective permeation properties and high mechanical flexibility, which could be key properties for backsheets in terms of higher PV module reliability. In this work, the weathering stability of PET/fluoropolymer backsheet and an alternative coextruded polyolefin‐backsheet was investigated in terms of thermal and mechanical stability. Both materials were artificially aged and the changes caused by aging were investigated. The polyester‐based backsheet showed embrittlement and reduced elongation at break for 70%. The polyolefin‐based backsheet retained its mechanical flexibility even after 2000 h of aging under damp‐heat conditions, with no significant physical or chemical aging processes occurring. The comparison of the results of both backsheets suggests that the polyolefin backsheet is a promising candidate for the reduction of cracks and delamination in the field. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48899. [ABSTRACT FROM AUTHOR]

The effect of hydrostatic pressure of up to 40 MPa on the seawater permeation, crystalline structure, and mechanical strength of carbon fiber and glass fiber‐reinforced polyoxymethylene (POM) composites was investigated. The experimental results reveal that hydrostatic pressure slightly promotes seawater permeation throughout the POM composites and degrades the bonding strength of the matrix–fiber interface. In the POM matrix, the seawater hydrostatic pressure does not influence the chemical stability but induces a physical chain scission process, which is characterized by linearly decreased molecular weight. The chain scissions initially entangled in the amorphous region are supposed to have sufficient mobility to join the crystalline phase. The increased crystallinity, albeit slight, together with the compress effect of hydrostatic pressure may possibly account for the stable mechanical strengths of the POM composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48686. [ABSTRACT FROM AUTHOR]

ABSTRACT The influence of the difference in wettability between glass fiber (GF) and polycarbonate (PC) on the microfractures of GF reinforced PC was investigated by using an acoustic emission (AE) method. In the case of well-coupled GF-reinforced PC, it is suggested that in the AE amplitude region higher than about 16 mV, microfracture related to scission of polymer chains occurs at the interfacial layer between GF and PC. On the other hand, in the case of poorly-coupled GF-reinforced PC under stress, debonding and interfacial slippage between GF and PC occurred below the yield stress of PC, whereas interfacial fracture and GF breakage occurred above the yield stress. Debonding and interfacial slippage between GF and the PC matrix were closely related to an AE amplitude smaller than about 16 mV. The relationship between stress and AE events is expressed in this case by the Eyring model. The activation energy of interfacial slippage between GF and PC was about 74 kJ/mol, which corresponds to the energy of chain-backbone motion of PC in the glassy state. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45664. [ABSTRACT FROM AUTHOR]

ABSTRACT To evaluate the effects of two-dimensional (2D) programming on thermal properties of shape memory polymer (SMP)-based composites when exposed to high temperature, the specimens of composites were prepared and programmed. Then the morphology, thermal properties, dynamic evolution, and constituents of released gaseous products were characterized. Results indicate that the programmed composite is more compacted, but the proportion of interconnected voids is larger than that in the nonprogrammed sample. 2D programming causes molecular or segmental orientations in SMP, and leads to the decrease in the char yield from 16.1 to 8.1%. The programmed sample shows a lower thermal stability. Further, the melting enthalpy of nonprogrammed composite is 1012 J/g which is lower than 1100 J/g of the programmed sample. The prestored stress in oriented molecules or segments of SMP is more prone to cause the chain scissions. The dynamic evolution and constituents of released volatiles from nonprogrammed and programmed samples are similar, but the release amount of volatiles from the latter is larger. Finally, the more compacted charring layer of nonprogrammed composite is more efficient to prevent volatiles from releasing out. The 2D programming has a slight influence on the elemental contents of O, Si, and C in the charring layer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45480. [ABSTRACT FROM AUTHOR]

ABSTRACT The influence of rubber devulcanization by microwaves in the reversion behavior is still modestly explored in the literature. The reversion occurs due to thermal degradation of unstable crosslinkings formed during the vulcanization process. This phenomenon results in poor final mechanical properties of the artifacts. In this work, some formulations based on natural rubber (NR) with the incorporation of NR devulcanized by microwaves at different exposure times to the microwaves were vulcanized by compression molding at the same temperature and time used for the study of their vulcanization characteristics, in order to correlate the properties obtained and understand the influence of the reversion on the mechanical properties. The results showed that levels of devulcanization/degradation of the recycled phase, as well as the additional heating time influenced on the behavior of reversion and, consequently, on the mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45325. [ABSTRACT FROM AUTHOR]

ABSTRACT Cure rheometry is routinely used in the rubber industry for processability assessment and cure-time determination. This article examines these rheological outputs in Cole-Cole format to explore what new insights can be gained from this alternative data plot. It differs from the conventional Cole-Cole treatment in its application to a reacting system. The plots described here are therefore of G″( t) vs. G′( t). Initially some attention is directed to the basics of the Cole-Cole treatment and the likely features to be expected when applied to systems undergoing both cure and reversion. This article goes on to consider examples of both by studying a natural rubber vulcanization at temperatures of 160 °C and above. Through the Cole-Cole approach, it is thought possible to identify the competition between intermolecular and intramolecular sulfurization, and between crosslink and main-chain scission. The approach offers considerable potential to expand the capabilities of cure rheometry. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44085. [ABSTRACT FROM AUTHOR]

ABSTRACT To clarify an effect of polymer chain scission on a polystyrene (PS)/multi-wall carbon nanotube (MWNT) composite photodegradation, a relationship between the change of molecular weight and photodegradation behavior was studied. The MWNT loading brought about severe PS chain scission and led to the increase of the low molecular weight (less than 105) fraction. The increase of the fraction was not proportional to the loading amount and showed the minimum at the 2% loading. The strange behavior was due to a rheological effect bringing about a decrease of shear stress in the composite preparation. An unsaturated end group was produced by the chain scission and became the photodegradation initiator leading to auto-oxidation and crosslink reactions. The MWNT scavenged radical species and worked as an antioxidant. The coexistence of the unsaturated end group and MWNT made the photodegradation behavior complicated. However, the MWNT radical scavenging ability was considerably poor, and the MWNT had little ability to inhibit the photodegradation initiation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40362. [ABSTRACT FROM AUTHOR]

ABSTRACT The main objective of this work has been to study the effects of copolymer microstructure, both chemical and physical, on the microporosity, in vitro hydrolytic degradability and biocompatibility of electrospun poly( l-lactide- co-ε-caprolactone), PLC, copolymer tubes for potential use as absorbable nerve guides. PLC copolymers with L : C compositions of 50 : 50 and 67 : 33 mol % were synthesized via the ring-opening copolymerization of l-lactide (L) and ε-caprolactone (C) at 120°C for 72 h using stannous octoate (tin(II) 2-ethylhexanoate) and n-hexanol as the initiating system. Electrospinning was carried out from solution in a dichloromethane/dimethylformamide (7 : 3 v/v) mixed solvent at room temperature. The in vitro hydrolytic degradation of the electrospun PLC tubes was studied in phosphate buffer saline over a period of 36 weeks. The microporous tubes were found to be gradually degradable by a simple hydrolysis mechanism leading to random chain scission. At the end of the degradation period, the % weight retentions of the PLC 50 : 50 and 67 : 33 tubes were 15.6% and 70.2%, respectively. Pore stability during storage as well as cell attachment and proliferation of mouse fibroblast cells (L929) showed the greater potential of the PLC 67 : 33 tubes for use as temporary scaffolds in reconstructive nerve surgery. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4357-4366, 2013 [ABSTRACT FROM AUTHOR]

ABSTRACT Bentonite-filled ethylene propylene diene monomer (EPDM/Bt) composites were prepared using two roll mill compounding method and the effect of Bt loading on the thermal aging, swelling resistance and crosslink density of EPDM/Bt composites were studied. The effect of in situ addition of different silane coupling agents (SCAs) on the above properties at optimum Bt loading of EPDM/Bt composite was also investigated. Thermal aging test results show that the tensile strength and tensile modulus at 100% elongation (M100) increase initially for 2 days aged composites and decrease slightly after 4 days of aging, meanwhile the elongation at break ( Eb) decrease gradually with aging period as compared to the unaged composites. Upon aging, swelling resistance increase initially indicating increased crosslink density of EPDM/Bt composite due to post-curing and reduced after 4 days of aging due to crosslink destruction and EPDM chain scissioning. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4419-4427, 2013 [ABSTRACT FROM AUTHOR]

The modifications in microstructural, optical, and photoluminescence properties of the Lexan polycarbonate (bisphenol-A-polycarbonate) films exposed to different electron doses have been studied using UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), positron annihilation lifetime spectroscopy, photoluminescence spectroscopy, and scanning electron microscopy (SEM). The obtained UV-vis spectroscopy results showed decrease in optical energy gap, optical activation energy, and increase in number of carbon atoms per cluster with increase in electron dose. The chemical changes in electron irradiated polymers due to chain scission and reconstruction have been observed from FTIR spectroscopy. The correlation of positron lifetime study with optical measurement is obtained, and electron irradiation-induced microstructural modifications within the polymer is understood. SEM result shows the degradation of Lexan polymer after electron irradiation. The mechanical properties and average molecular weight of Lexan decrease after irradiation, whereas average number of chain scissions per original polymer molecule increases. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Ethylene-octene copolymer (EOC) was crosslinked by dicumyl peroxide (DCP) at various temperatures (150-200°C). Six concentrations of DCP in range 0.2-0.7 wt % were investigated. cross-linking was studied by rubber process analyzer (RPA) and by differential scanning calorimetry (DSC). From RPA data analysis real part modulus s', tan δ, and reaction rate were investigated as a function of peroxide content and temperature. The highest s' and the lowest tan δ were found for 0.7% of DCP at 150°C. Chain scission was analyzed by slope analysis of conversion ratio, X in times after reaching the maximum. Less susceptible to chain scission are temperatures in range 150-170°C and peroxide levels 0.2-0.5%. Heat of reaction was analyzed by DSC at various heating rates (5-40°C min). It was found to be exothermic. By projection to zero heating rate, the reaction was found to start at 128°C with the maximum at 168°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

Degradation is an unavoidable part of a material's life making it important to both monitor and control the aging behavior of plastics. This study compares thermooxidative degraded composites of a novel bio‐based and sustainable filler, Biocarbon (MBc), against that of traditional and commercially available fillers (glass fiber and talc) used in the automotive industry. The influence of thermooxidative degradation on the composites was studied under accelerated heat aging for 1000 h at 140°C. The mechanical properties of the composites were evaluated using notched Izod impact as well as both tensile and flexural tests. Morphological structure of the composites was investigated using a scanning electron microscopy. Dynamic mechanical analysis and differential scanning calorimetry were used to evaluate the physical transitions both before and after aging. The glass‐filled composites displayed the best performance; while, both the talc and biocarbon composites possessed similar strength and ductility performances. Advantageously, the biocarbon composites experienced an 11% reduction in density as compared to talc‐filled composites with similar weight content. After aging, all composites exhibited reduced tensile and flexural strengths ranging from 5 to 67% partly due to chain scission. Whereas, the modulus of all composites increased with a range of 1–24% due to an annealing effect. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48618. [ABSTRACT FROM AUTHOR]

Poly(ethylene terephthalate)/poly(lactic acid) (PET/PLA) blends with composition of 90/10 and 75/25 (wt %/wt %) along with two types of graphenic materials, namely graphene oxide (GO) and exfoliated graphite (xGnP), were prepared through one‐step melt mixing process. The Thermal, thermo‐oxidative, and hydrolytic degradation characteristics of the developed degradable PET‐based nanocomposites were investigated. Thermal degradation studies by thermogravimetry analysis and melt rheological analysis in N2 atmosphere, revealed that unlike xGnP, the addition of GO to the blends reduced their thermal stability leading to reduction of viscosity and elasticity of the blends. The behavior was attributed to the role of GO in enhancing the chain scission reactions. In the air atmosphere, the barrier properties of the graphenic materials prevailed. Compared to xGnP, the relatively well‐dispersed GO showed better barrier against oxygen and increased the thermo‐oxidative stability of the blends. Investigation of the hydrocatalytic degradation of developed systems, at different pH of 2 and 4, over a period of 40 days at 37 °C, showed that the amount of weight loss of the GO‐containing nanocomposite systems was higher than that of xGnP. The overall results of thermal, thermo‐oxidative, and hydrocatalytic degradation studies confirmed the prominent role of GO in the development of degradable PET‐based products. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48466. [ABSTRACT FROM AUTHOR]

To improve the suitability of poly(lactic acid) (PLA) for implantable devices, it ideally needs greater ductility without losses in strength. Here biodegradable poly(2‐ethyl‐2‐oxazoline) (PEtOx) was selected as an additive to improve hydrophilicity of PLA as well as mechanical properties, while UV irradiation was considered as a bulk modification method to increase the long‐term stability. The PLA blend showed improved tensile strength and elongation‐at‐break with small amounts of PEtOx added (1.5 wt %). Crosslinking by UV irradiation showed significant improvements with a dibutyltin dilaurate catalyst even though it produced a high degree of chain scission during melt processing. After UV irradiation for 150 h, the crosslinked material recovered mechanical properties and melt rheological properties comparable to the initial PLA‐1.5%PEtOx blend (without catalyst added). Crosslinking was only possible with the added PEtOx present. A mechanism for the crosslinking reactions examined has been proposed since it has not been previously reported in the literature. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48023. [ABSTRACT FROM AUTHOR]

The photodegradation of copolyesters based on 1,4‐cyclohexanedimethanol (CHDM), tetramethyl‐1,3‐cyclobutanediol, and terephthalic acid units was investigated using various analytical methods. Photodegradation products were characterized using Fourier transform infrared (FTIR), liquid chromatography–mass spectrometry (LC–MS), and X‐ray Photoelectron spectroscopy (XPS) analysis. The homolytic scission of C‐O bonds of ester groups through a Norrish Type I reaction was supported by time of flight secondary ion mass spectrometry and LC–MS results, while nuclear magnetic resonance analysis confirmed hydrogen abstraction from the tertiary carbon of CHDM units in the trans (equatorial‐equatorial) conformation. Chain scission through Norrish Type II reaction is also responsible for the formation of carboxylic acid end group. Fluorescence emission from irradiated glycol modified poly(ethylene terephthalate) films demonstrated the formation of mono‐ and dihydroxyterephthalate species. Furthermore, FTIR and XPS valence band analysis confirmed configurational changes, in the polymer chain due to photodegradation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47148. Photodegradation of Copolyesters. [ABSTRACT FROM AUTHOR]

The long‐term thermal oxidative aging behavior of uncompressed and compressed hydrogenated nitrile rubber seals was studied in terms of the weight loss, chemical structure, crosslinking density, compression set, fracture morphology, and mechanical properties. It was found that weight loss of the uncompressed seals was more than that of the compressed seals due to restricted mobility of additives and molecular chains under compression. The ATR–FTIR results showed that hydroxyl groups and carbonyl groups both were formed under the uncompressed and compressed states, whereas only the generation of amide groups was observed under the uncompressed state. Additionally, crosslinking reactions dominated throughout the aging process, but stress‐induced and oxidation‐induced chain scissions occurred and competed with crosslinking during subsequent middle and later stages of aging at 110 °C. Compression set of the compressed seals implied the formation of a denser network structure. The surface damage of the uncompressed seals gradually turned more serious and inhomogeneous than that of the compressed seals. Mechanical properties of the uncompressed and compressed seals showed a similar variation tendency with exposure time and degraded more seriously at higher temperatures. The TGA results indicated that the aging conditions (elevated temperature and compressive stress) did not significantly affect the thermal stability of the rubber seals. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47014. [ABSTRACT FROM AUTHOR]