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Anionic polyamide 6 (aPA6), synthesized via the ring-opening polymerization of ε-caprolactam, has emerged as a promising matrix for high-performance thermoplastic composites, offering advantages over conventional thermoplastics and thermosets. However, optimizing the microstructure and mechanical properties of aPA6 requires a comprehensive understanding of how processing conditions influence polymerization kinetics and resulting material characteristics. This work systematically investigates the interplay between two critical processing parameters, i.e., the mold temperature and catalysts concentration, on the microstructural and thermomechanical properties of aPA6, via a combined experimental and statistical approach. Increasing the mold temperature from 145 °C to 175 °C and the catalysts concentration led to a reduction in crystallinity, due to the promotion of polymerization over crystallization. Higher temperatures and concentrations also slightly anticipated thermal degradation onset from 388 °C to 327 °C. The elastic modulus decreased from 3.4 GPa to 2.7 GPa as temperature increased, primarily governed by the diminishing crystallinity. Similarly, the ultimate tensile strength declined from 80 MPa to 68 MPa with rising temperature. Interestingly, the strain at break exhibited a complex dependence, peaking at 48 % for an intermediate temperature of 165 °C and lower catalysts concentration, suggesting an optimal balance of crystallinity, branching, and high molecular weight. Statistical empirical models captured these relationships, enabling prediction and tailoring of aPA6 properties by tuning processing conditions. These insights pave the way for optimized manufacturing of high-performance aPA6 composites via techniques like thermoplastic resin transfer molding and expand potential applications to thermally sensitive reinforcements like natural fibers. [Display omitted] • Crystallinity reduced by increasing mold temperature and catalysts. • Elastic modulus peaked at 3.4 GPa with low mold temperatures. • Ultimate tensile strength rised from 68 MPa to 80 MPa with decreasing mold temperature. • Strain at break peaked at 48 % for 165 °C mold temperature and low catalysts concentration. • Statistical models captured property-processing relationships, enabling property tailoring. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS) exhibits exceptional thermal stability and processability, however, limited adhesion and carbonization performance hinders its applications as flexible thermal protection materials. Herein, a phenolic epoxy modified silicone rubber (KFAP@PDMS) was synthesized, and the microscopic morphology, macroscopic mechanical properties, adhesive properties, thermal properties and ablative properties were systematically investigated. Compared to pure PDMS, the modified material exhibits a maximum tensile strength increase of 170 %, maximum elongation at break increases of 141 %, maximum adhesion strength increases of 209 %, and linear ablation rate decrease 84.9 %, respectively. Thermal degradation analysis indicates that the introducing of KFAP increases crosslink density while the degradation products mainly consist of D 3 , D 4 , and toluene compounds. Ablation analysis reveals that the inclusion of KFAP promotes an in-situ carbon-silicon multiphase ceramization reaction, resulting in densification of the carbon layer and significant improvement of the ablation performance. [Display omitted] • A carbon silicon composite hybrid network of phenolic epoxy silicone rubber was constructed. • The adhesion, mechanical and ablation properties of silicone rubber have been simultaneously improved. • Thermal degradation mechanism of hybrid material was discussed in detail. [ABSTRACT FROM AUTHOR]

General approaches for preparing epoxy vitrimers required lots of catalysts to accelerate transesterification to form the cross-linked network and the residual catalyst not only resulted in toxicity but also poor compatibility with other components. Herein, a green and facile strategy for preparing gallic acid epoxy resin (GA-EP) was developed under catalyst-free condition using renewable gallic acid, xylitol and hexahydro 4-methylphthalic anhydride (MHHPA) as feedstocks. The results indicated that the bio-based epoxy vitrimer had higher glass transition temperature (122 °C), satisfactory mechanical, thermal and degradation properties compared to neat Bisphenol A-based epoxy vitrimer. Furthermore, recycled GA-EP was ground into powder and added to the fresh resin to investigate its reusability. Compared to the original, the recycled epoxy vitrimer system demonstrated comparable performance, except for minor reductions in glass transition temperature (T g) and modulus, likely stemming from the inherent inhomogeneity of the reprocessed material. This work provides a new approach to the production of high T g bio-based epoxy vitrimers without adding any catalyst. [Display omitted] • Vitrimers based on gallic acid are utilitarian materials and prime contenders for industrial applications. • The glass transition temperature of the vitrimers was controlled by the addition of polyol (xylitol). • Gallic acid-derived catalyst-free epoxy vitrimers exhibit high T g (122.3–182.8 °C) and recyclability. [ABSTRACT FROM AUTHOR]

Due to the rapid development of high frequency and high rate communication technology, polyimide (PI) films with ultra-low dielectric loss (D f) at high frequency, excellent thermal and mechanical properties are urgently needed. A series of PI films with ultra-low D f were prepared by introducing different mesogen units. Among them, one novel PI film with biphenyl liquid-crystal-like units (BAHQ-TFMB) achieve a recorded low D f of 0.00169 (10 GHz) which surpasses previous studies on pure PI bulk films. Importantly, the high degree of collinearity of the friction work (W f) and D f of PI films (Pearson's r = 0.992) was confirmed, which indicate that W f among PI macromolecules plays an important role in determining D f of PI films. To reveal underlying reason for reducing the W f and D f of PI films, the contribution of the degree of orientation and crystallinity of PI films with or without liquid-crystal-like structures were comparative studied. Through a two-dimensional orientation determinant, it is found that increasing the crystallinity of liquid-crystal-like PI films is the main contribution to reducing W f and corresponding D f of PI films while the orientation of PI films seems to have weak effect. Moreover, BAHQ-TFMB PI film exhibits excellent mechanical properties. The tensile strengths is 145.5 ± 12.0 MPa and Young's moduli is 4.76 ± 0.28 GPa. [Display omitted] • The PI film with biphenyl liquid-crystal-like units achieve a recorded low dielectric loss of 0.00169 (10 GHz). • The friction work (W f) among PI macromolecules plays an important role in determining D f of PI films. • Increasing the crystallinity of liquid-crystal-like PI films is the main contribution to reducing W f and D f of PI films. [ABSTRACT FROM AUTHOR]

This investigation employed free radical melt grafting technology for the synthesis of (POE/R-LLDPE)-g-(GMA-co-St) graft copolymers. Subsequently, this graft copolymer was applied as a modifier for poly (butylene terephthalate) (PBT) resin. The effects of varying recycled linear low-density polyethylene (R-LLDPE) contents in the graft on the rheological behavior, thermal properties, mechanical properties, and toughening mechanism of PBT/(POE/R-LLDPE)-g-(GMA-co-St) blends were exhaustively explored. The findings revealed that glycidyl methacrylate (GMA) and styrene (St) were effectively grafted onto the poly (ethylene-octene) (POE) and R-LLDPE molecular chains. This process enabled the epoxy groups in the GMA of the graft to react with the terminal groups of the PBT resin, thereby enhancing its compatibility with PBT. The use of R-LLDPE-g-(GMA-co-St) or POE-g-(GMA-co-St) as singular modifiers did not produce optimal modification results. Conversely, the most effective modification of the PBT resin was observed when both were combined, indicating a pronounced synergistic modification effect. The optimal overall performance of the blend was noted when the R-LLDPE content in the graft copolymer was 50 wt%. This method significantly enhanced the toughness of the blend while preserving excellent thermal stability and mechanical strength, concurrently reducing the product cost. At this point, a high concentration of voids was observed in the stress-whitening area of the impact specimens. The PBT matrix displayed conspicuous shear yielding with a notably rough impact fracture surface, manifesting highly significant tough fracture characteristics. [Display omitted] • The (POE/R-LLDPE)-g-(GMA-co-St) graft copolymer is prepared, which serves as an efficient toughening agent. • The toughening of PBT with POE and R-LLDPE achieves an excellent balance between rigidity and toughness. • R-LLDPE exemplifies resource reutilization, embodying green chemistry and sustainable development principles. [ABSTRACT FROM AUTHOR]

Vitrimers behave like traditional thermosets with good thermal and mechanical properties at service temperature, combined with thermoplastic behaviors above a specific temperature due to their dynamic cross-linked networks. However, there is a lack of effort in studying the mechanical properties of existing vitrimers, which are important for applying them in practical applications. The objective of this work is to experimentally investigate the tensile, compressive, flexural, torsional, and impact properties of a widely studied epoxy-based vitrimer through the various tests: tensile test, compressive test, three-point bending test, torsional test, and pendulum impact test. Since the vitrimer has the same chemical composition as conventional epoxy, all the mechanical tests mentioned above are also conducted on the epoxy for comparison. The results show that the vitrimer is comparable to the epoxy in tensile, compressive, flexural, and torsional properties, while its impact strength is substantially improved. Finally, the thermoplastic behaviors (i.e., reprocessing, recycling, reshaping) of the vitrimer are also studied. [Display omitted] • Epoxy-based vitrimer has the same chemical composition as conventional epoxy. • The vitrimer is comparable to the epoxy in tensile, compressive, flexural, and torsional properties. • The vitrimer possesses 2.7 times higher impact strength than conventional epoxy. [ABSTRACT FROM AUTHOR]

Polybenzoxazine-imine hybrid resins with good thermal and mechanical properties, as well as excellent shape memory and recycling properties, were prepared from bio-based benzoxazine synthesized from vanillin and a biobased diamine derived from furylamine and benzaldehyde (V-bfa), terephthalaldehyde (TA), and Jeffamine T403. The films have good thermal, mechanical, and recycling properties, influenced by the ratio of V-bfa and TA. The higher the percentage of V-bfa, the better the thermal properties, thermal stability, and shape memory properties of the films, unfortunately, the film with 100 % V-bfa content (Btt-10) exhibited brittleness and could not be fully recovered. Surprisingly, the film with half the amount of v-bfa (Btt-11) has excellent shape memory properties, unfolding over 90° in just 12 s after folding and returning to its original shape in 20 s, moreover, the rate of shape fixation (R f) and the rate of shape recovery (R r) is 90.56 % and 95.56 %, respectively. Meanwhile, the thermal, mechanical, and shape memory properties of the film were also not damaged in any way even after three recycling cycles. Therefore, Btts film are very low carbon and environmentally friendly, complying with the requirement to reduce carbon emissions. [Display omitted] • Bio-benzoxazine-imine hybrid resins with good thermal and mechanical properties are prepared. • The films exhibit excellent shape memory properties. • The film shows stable thermal, thermal stability and mechanical properties even after 3 cycles of recycling. [ABSTRACT FROM AUTHOR]

The development of lightweight shape memory materials with exceptional thermal insulation properties is highly important in aerospace applications. Herein, shape memory polyimide (PI) aerogels was fabricated by molecularly designed PI molecular chains through freeze gelation and subsequent thermal imidization. The freezing conditions were controlled to regulate the porous microstructures of the aerogels. The interactions between PI chains formed physically crosslinked netpoints, which could overcome the expansive force and capillary force, thereby creating a stable porous structure. Because shape memory was thermally activated, the shape memory mechanisms associated with the thermal conductivity of the aerogels were comprehensively explored. Upon decreasing the pore size, dense frameworks were formed, contributing to the improved thermo-mechanical and compressive properties. Moreover, the heat transfer efficiency in the aerogel skeleton was enhanced, resulting in a rapid shape recovery response. Benefiting from the physically crosslinked structures, including entangled chains and π-π interactions, the fabricated PI aerogels demonstrated exceptional shape fixation and recovery capabilities. These findings may provide guidelines for designing smart aerogels for aerospace applications. [Display omitted] • Shape memory polyimide aerogels with tunable porous microstructures were fabricated. • The size of the micropores was regulated by controlling the freezing conditions. • The reduction of pore size accelerated the shape recovery process. • The comprehensive exploration of the shape memory mechanisms was conducted. [ABSTRACT FROM AUTHOR]

A series of phthalonitrile resins were synthesized through innovative reactions between compounds derived from benzyl alcohol and nitro functionalities. The synthesis commenced with the reaction of specific alcohols (4-hydroxybenzyl alcohol, vanillyl alcohol, and 1,4-benzenedimethanol) with 4-nitrophthalonitrile, resulting in the formation of three phthalonitrile monomers. These monomers were then cured using 4,4′-diaminodiphenyl ether as a curing agent, resulting in the phthalonitrile resins, namely BCDPN, XCDPN, and DBDPN. The investigation revealed that these resins possessed remarkable properties, particularly in terms of thermal stability and dynamic mechanical behavior. Notably, BCDPN exhibited superior thermal stability, achieving a T d10 % of 534 °C. XCDPN and DBDPN demonstrated outstanding dynamic mechanical properties, characterized by a storage modulus exceeding 3400 MPa. The synthesis approach, leveraging compounds derived from benzyl alcohol and nitro reactions, not only broadens the scope of raw materials but also offers novel and alternative preparation strategies for phthalonitrile resins. This study enhances the understanding of the curing behavior and thermal properties of these resins, providing valuable insights into their potential applications in high-performance polymer materials. [Display omitted] • Synthesis of phthalonitrile resin uses compounds from benzyl alcohol & nitro reaction, expanding raw material sources. • Great thermal stability & dynamic mechanical props in BCDPN, XCDPN, DBDPN resins. • Curing behavior & thermal props insights for potential in high-performance polymer materials. [ABSTRACT FROM AUTHOR]

With bio-renewable and environmentally friendly nature, biobased polyamides have emerged as attractive alternatives to traditional petroleum-derived polymers. However, poor thermal and mechanical performance, high costs, and limited scalability significantly hinder their practical applications. Herein, a series of biobased copolyamides PA6/PA56 (CoPAs) were successfully synthesized from caprolactam, adipic acid, and the lysine-derived biobased monomers 1,5-pentanediamine. The copolyamides were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (1H NMR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), rheological analysis, mechanical testing, and scanning electron microscopy (SEM). The result shows the α to γ transition in the crystalline form of the copolyamides with comonomer loading. The melting temperature, crystallization temperature, and crystallinity gradually decrease due to the introduction of the odd-even structure, causing deviation in amide positions and reducing hydrogen bond formation between molecular chains. Furthermore, variable-temperature infrared (VTIR) analysis and density functional theory (DFT) calculations further confirm a decrease in intermolecular forces. Importantly, the mobility of the molecular chains in the amorphous region is significantly improved, endowing the copolyamides with sufficient degrees of freedom to cope with externally applied strains. Moreover, significant entanglement facilitates effective stress transfer during stretching. As a result, the synthesized copolyamides achieve a high strength of 51 MPa and a remarkable toughness of 199 MJ/m3, without sacrificing thermal stability and processing properties. These biobased CoPAs show great potential and prospects in the field of high-performance thermoplastic materials, films, and textiles. [Display omitted] • Hydrogen bonding decreased with the introduction of the odd-even structure. • The massive entanglements formed within the copolyamides effectively transferred the stress. • The mechanical properties of biobased copolyamides were remarkably enhanced. [ABSTRACT FROM AUTHOR]

A series of supramolecular polyurethanes (SPUs) were designed and synthesised with synergetic multifunctional hydrogen bonding aliphatic amide end-caps. Hydrogen bonding between the urethane, urea, and amide motifs in the polymers afford strong dynamic association between polymer chains in the solid state. Phase separation of the apolar and polar components of the polyurethanes also serves to reinforce their thermal and mechanical properties. The supramolecular polyurethane with bisamide-morpholine end caps associates via multiple hydrogen bonds and exhibits enhanced tensile and thermal properties when compared to the other materials. Variable-temperature infrared spectroscopy (VT-IR) and atomic force microscopy (AFM), were carried out to study the phase morphology of the polymers and revealed a correlation between increased phase separation and the introduction of amide motifs in the end-caps. These SPUs also exhibit excellent healing abilities, requiring temperatures >200 °C to recover their physical properties. [Display omitted] • Self-assembly of polyurethanes via hydrogen bonding and phase separation • Recovery of physical properties post damage at elevated temperatures • Re-adhesion demonstrated on both glass and aluminium over three cycles [ABSTRACT FROM AUTHOR]

Four new diamines (3TFDABA, 2TFDABA, 22TFDABA and TFAPTA) were successfully synthesized to investigate the effect of different trifluoromethyl (CF 3) substitution position on poly(amide-imide)s (PAIs) properties. High-performance PAIs were prepared from high-temperature polycondensation of these diamines with 6FDA dianhydride. All the PAI films exhibited good heat resistance with glass-transition temperatures (T g s) of 311–392 °C, good 5% weight loss temperatures (T d5% s) of 480–510 °C in nitrogen, and excellent optical transparency with T 450 ranging from 52% to 84%. According to the monomer structural design, a high heat resistant and colorless poly(amide-imide) film (PAI-2-6FDA), with excellent optical properties (T 450 of 82%), outstanding thermal properties (T d5% of 499 °C and T g of 392 °C), and good mechanical properties (tensile strength of 123 MPa, tensile modulus of 4.4 GPa) was achieved. A comprehensive structure-to-property relationship study revealed that the CF 3 in ortho -position of the amino group effectively inhibited the rotation between imide ring and benzene, thus improved the heat resistance of the film. Moreover, it could also weaken the generation of charge transfer complexes through strong electron-withdrawing ability, which is beneficial for the synthesis of colorless polyimides. [Display omitted] • Synthesis of four new diamines with different CF 3 substitution position along amide and amine moieties. • Structure property relationship of CF 3 substitution to influence the thermal and optical properties of polyamide-imides. • The CF 3 in ortho -position of the amino group exhibit the best properties. [ABSTRACT FROM AUTHOR]

In order to prepare thermoplastic polyimide (PI) resins with good comprehensive performances, the modification of thermoplastic polyetherimides (PEIs) by 1,4-bis(2,3-dicarboxyphenoxy)-2- tert -butylbenzene dianhydride (3,3′-TBHQDA) was systematically investigated. The PEI-a-x and PEI-b-x series of polyetherimides were synthesized by chemical imidization of the diamine monomer m -phenylenediamine (m -PDA) with different contents of 1,4-bis(3,4-dicarboxyphenoxy)-2- tert -butylbenzene dianhydride (4,4′-TBHQDA) and 3,3′-TBHQDA or 4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride) (4,4′-BPADA) and 3,3′-TBHQDA. These PEIs had glass transition temperatures (T g s) in the range of 217–264 °C, low melt viscosities of 79–2367 Pa s, good transmittances of 87–88 % at 450 nm, and displayed good mechanical properties with tensile modulus of 2.8–3.2 GPa, tensile strengths of 89.6–118.4 MPa, and elongations at break of 3.9–6.4 %. The introduction of 3,3′-TBHQDA successfully improved thermal properties and melt processability of the PEIs. Among them, PEI-a-50 and PEI-b-50 displayed better comprehensive performances in PEI-a-x and PEI-b-x series, respectively, with moderate T g s (256 and 249 °C, respectively), extremely low melt viscosities (161 and 297 Pa s at 400 °C, respectively), high transmittances at 450 nm (87 %), and good mechanical properties (tensile modulus of 3.1 and 2.8 GPa, tensile strengths of 105.6 and 106.3 MPa, respectively). [Display omitted] • The modification of PEIs based on 4,4′-TBHQDA and 4,4′-BPADA by 3,3′-TBHQDA. • The heat resistance and melt processability of PEIs were modified by 3,3′-TBHQDA. • The PEI-a-50 and PEI-b-50 showed T g s of 256 and 249 °C, respectively. • The PEI-a-50 and PEI-b-50 had melt viscosities of 161 and 297 Pa s, respectively. [ABSTRACT FROM AUTHOR]

The high performance of polyester industrial yarns mainly depends on the crystalline and orientation structure of poly(ethylene terephthalate) (PET) formed during spinning, but the influence of pre-orientation degree of the as-spun yarns on the microstructure evolution is still unclear. In this paper, the multi-scale structural evolution of pre-oriented PET fibers during crystallization was investigated to reveal the influence of pre-orientation degree on the competition mechanism of orientation and disorientation of PET chains. Due to the ordered regions with extended chains formed in the pre-orientation, crystals grow around the ordered regions during crystallization and ultimately form lamellar crystal along fiber axis. High degree of pre-orientation promotes the crystallization of fibers avoiding the disorientation effect. Finally, a highly oriented crystal region is formed and the arranging direction of the crystal axis is consistent with the fiber axis. However, high degree of pre-orientation led to a decrease in the amorphous trans content as well as the number of interlamellar links, so the interplanar spacing was larger than that of low pre-oriented fibers and the crystals were looser. Reflected in the mechanical and thermal properties of the fibers, the increase of pre-orientation degree greatly decreased the stress relaxation rate and improved the strength and elongation at break, but decreased melting point. The results provide theoretical basis support for optimizing the hot drawing and heat setting of polyester industrial yarns. [Display omitted] • High pre-orientation degree avoid the disorientation of PET fibers during crystallization. • The interplanar spacing of PET increases with the increase of pre-orientation degree. • High pre-orientation degree improves the mechanical properties of PET fibers but lowers the T m. [ABSTRACT FROM AUTHOR]

Mechanical properties are essential for polyester materials due to their widespread applications as fibers, films, and engineering accessories. The copolymerization strategy has been developed to enhance polyester properties, but facile-synthesized new materials are still under discovery. In this work, we designed a series of terminal functioned polyesters, for introducing plasticization effects and π-π stacking interactions. The fabrication process can be one-pot achieved via melting polycondensation method. The prepared modified polyesters exhibit significantly improved elongation of break (560%), which is 104% improved compared with pristine poly(ethylene terephthalate). Meanwhile, the maximum toughness reaches 206.1 MJ/m3. The thermal properties, viscoelastic properties, crystallinity properties, and fracture morphologies of the as-prepared polyesters are investigated as well. Results show that great elongation of break, higher crystallinity, and good processability are achieved simultaneously. This work provides a one-pot fabricated terminal functioned polyester with advanced tensile properties, expanding its potential application as engineering materials. [Display omitted] • Polyester has been reinforced after furoic acid modification, resulting in advanced comprehensive tensile properties. • The preparation is one-pot achieved by the green method of bulk polymerization. • The reinforcement principles of plasticization effects and π-π stacking interactions are studied in detail. [ABSTRACT FROM AUTHOR]

The incorporation of diverse macromolecular blocks into CO 2 -based polycarbonates offers a promising approach for tailoring the properties of polycarbonates for special needs. In this work, we report for the first time the synthesis and characterization of an ABA triblock copolymer polycarbonate- b -polyalkenamer- b -polycarbonate in combination of ROCOP and ROMP via a one-pot route from CO 2 , epoxides and cycloalkenes. Cis -2-butene-1,4-diol as the bifunctional chain transfer agent was used as a "bridge" for the combination of different blocks as well as an effective regulator for the molecular weight of the polymers. In the one-pot reaction, the conversion of cycloalkenes reached 99.9% within 0.5 h, while the conversion of CHO was initially marginal at 0.5% but gradually increased to 99.7% after 24 h. The significant discrepancy in reaction rates between the two processes enables efficient synergistic reactions within the one-pot system. Specifically, hydroxyl-telechelic polyalkenamer is initially formed via ROMP and subsequently acts as an active species for ROCOP when coordinated with the porphyrin Al catalyst. This one-pot strategy provides a unique and simple method for controllably constructing functional polycarbonates with single-modal molecular weight distributions. By integrating the advantages of polyalkenamers and polycarbonates, this approach proves to be a viable solution for addressing the unsatisfactory thermal properties of aliphatic polycarbonates. [Display omitted] • CO 2 -based functional polycarbonate prepared via one pot reaction in combination of ROCOP and ROMP. • Bifunctional chain transfer agent as a bridge for polycarbonate and polyalkenamer to achieve block copolymer. • ABA block structure confirmed by 1H NMR, DOSY and MALDI-TOF analysis. [ABSTRACT FROM AUTHOR]

At present, silicone rubber has been widely used in the fields of aerospace and electronic materials, yet its long-term thermal performance still remains a challenge. In this investigation, polyhedral oligomeric silsesquioxane and ladder-like polysilsesquioxanes with multiple silicon-methoxy groups (MSPOSS, MSLPSQ) were synthesized successfully and used as cross-linkers to cure room temperature vulcanized silicone rubber (POSS-SR, LPSQ-SR). The results demonstrate that both MSPOSS and MSLPSQ can effectively improve thermostability, mechanical properties, and long-term thermal properties of RTV silicone rubber. The silicone rubber exhibits a remarkable preservation of strength and flexibility after long-time heat treatment at 400 °C. The silicone rubber demonstrates an impressive retention rate of 84.52% for tensile strength and 69.16% for elongation at break. An analysis of the pyrolysis process of the silicone rubber reveals that the 'back-biting' of polysiloxane chains were inhibited effectively by both MSPOSS and MSLPSQ. As a result of this inhibition, the silicone rubber's terminal chains are delayed from decomposing, resulting in retardation of initial thermal decomposition and significant improvement long-term thermal properties. This work may provide a new prospect for room temperature vulcanized silicone rubber for aerospace applications in extreme environments. In this study, polyhedral oligomeric silsesquioxane (POSS) and ladder-like polysilsesquioxanes (LPSQ) with multiple silicon-methoxy groups were synthesized successfully and used as cross-linkers to cure room temperature vulcanized silicone rubber (POSS-SR, LPSQ-SR). The results indicate that both POSS and LPSQ can effectively improve thermostability, mechanical properties, and long-term thermal properties of RTV silicone rubber. The decomposition temperature of 10% weight loss (T d10%) of LPSQ-SR reaches a temperature of 534.6 °C under nitrogen atmosphere, exceeding that of TEOS-cured silicone rubber (TEOS-SR) by nearly 157.1 °C. T d10% of LPSQ-SR is 456.2 °C under air atmosphere, which is 70 °C higher than that of TEOS-SR. The silicone rubber exhibits a notable retention of strength and flexibility after long-time heat treatment at 400 °C. The silicone rubber demonstrates an impressive retention rate of 84.52% for tensile strength and 69.16% for elongation at break. [Display omitted] • POSS and LPSQ modified silicone rubber with excellent thermal stability. • T d10% of LPSQ modified silicone rubber reaches 534.6 °C under nitrogen atmosphere. • The silicone rubber demonstrates impressive property retention after long-time heat treatment at 400 °C. [ABSTRACT FROM AUTHOR]

Four different types of HDPE and LDPE were prepared, and samples (H4, L2, and L3) that exhibited similar molecular weight, melt flow index, and rheological properties as BOPE (BO) were screened. The samples were each blended, and the better compatibility of HDPE/LDPE blend system (HL1) was confirmed through the Cole-Cole plot. Thermal and thermo-mechanical properties of HL1 blend compositions were analyzed to optimize the compositions for biaxial stretching application. Especially, G′ and Tan δ were confirmed as tools to evaluate the feasibility of optimized compositions for biaxial stretching application, and the proper range of stretching temperature at which the ΔTan δ value maintained minimal energy change for biaxial stretching was determined. The modulus of the biaxially stretched samples x3 was improved by more than 10% compared to the existing sheet, and the elongation at break of all blend samples was approximately twice as good as that of BO. The better optical transparency was achieved as of biaxial stretching of blend samples, and crystal change in the stretched film compared to the sheet was clearly confirmed. From this work, it was confirmed that the G′ and Tan δ have been proved to be used as a parameter to assess the processability for biaxial stretching, and this process gave the advantage of the optimized HDPE/LDPE blend ratio with higher mechanical and optical clarity, suggesting that the blend could be applied to various packaging materials. [Display omitted] • The optimal composition of HDPE/LDPE blend was designed, and the biaxial stretching process was successfully applied. • It was suggested that the Tan δ and storage modulus, G′ from the dynamic mechanical analysis could be a newly developed analysis tool for optimizing the conditions for the biaxial stretching. • The biaxial stretching was found to be a good processing step to improve the mechanical and physical properties in HDPE/LDPE blends. [ABSTRACT FROM AUTHOR]

Enhancing the mechanical properties and thermal stability of phthalonitrile polymers by hybrid modification holds significant importance in broadening their thermal-structural applications within high-temperature environments. Herein, fumed silica nanoparticles were considered as modifiers for a class of phenolic-type phthalonitrile resin, i.e., PN75, and their effects on mechanical properties and thermal stability were explored. First, contact angle tests (CA) were employed to show that the PN75 melt had good wettability on hydrophilic fumed silica (FS) and poor wettability on hydrophobic fumed silica (RFS). FS had a relatively satisfactory dispersion within PN75, which was indicated by scanning electron microscope (SEM), followed by FS/PN75 nanocomposites were prepared by melt blending under vacuum, with maximum FS addition 3 wt% of PN75. Second, the flexural strength and modulus of nanocomposites were increased by 23.5% and 11.9%. Finally, thermal stability of the FS/PN75 was promoted from 21.6% to 25.6% in char residue at 800 °C in the air atmosphere by the thermogravimetric analysis (TGA), which was contributed by the high heat-resistance and the shielding effect of FS. This work would inspire in-depth studies on modification and design of phthalonitrile-based hybrid composites for extreme thermal environment. [Display omitted] • Hydrophilic fumed silica exhibited well wettability with phenolic-type phthalonitrile resin. • Vacuum melt blending was proven as an efficient process achieving well dispersion of fumed silica nanoparticles. • Addition of fumed silica into phthalonitrile polymers improved the flexural strength and the char residue. [ABSTRACT FROM AUTHOR]

A study of the thermal and mechanical properties, as well as the molecular chain orientation of sulfur-vulcanized hydrogenated nitrile-butadiene rubber (HNBR) with acrylonitrile (ACN) content of 34 and 36 wt% and different crosslink density is presented. The objective is to establish the relationships between structural changes during stretching and the tensile and elastic behavior of HNBR having different chain microstructure. The (vulcanized) HNBR samples are amorphous at room temperature with glass transition temperatures that increase with increasing ACN content and crosslink density. The samples do not exhibit strain-induced crystallization. Stretching at room temperature only induces orientation of the amorphous segments along the stretching direction, which contributes to improved tensile strength, strain-hardening, and toughness, while preserving excellent elastic recovery of the rubbers. Precise correlations are established between the degree of orientation of the amorphous chain and the deformation in the framework of the affine deformation model of rubber elasticity. [Display omitted] • The structure and physical properties of hydrogenated nitrile-butadiene rubbers are investigated. • The relationships between strain-induced orientation and tensile and elastomeric behavior are established. • The ultimate tensile strength of vulcanized samples is associated to the degree of orientation of the amorphous phase achieved at high deformations before breaking. • The amorphous phase orientation contributes to improved toughness, strain-hardening and excellent elastic recovery. [ABSTRACT FROM AUTHOR]

It is still a considerable challenge for polyurethane elastomers (PUE) to possess outstanding mechanical and thermal performance simultaneously against harsh dynamic impact environment due to their heat accumulation, thermal stress softening and mechanical failure. Thus, this article innovatively prepared binary nanofibers composed of carbon nanofiber (CNFs) and aramid nanofibers (ANFs) to reinforce PUE, where catechol (CC) and polyethyleneimine (PEI) were served as interfacial modifier between nanofibers and polymer matrix. PUE with 1.5 wt% binary nanofibers achieve 31.62 % increase in crosslinking density, 146.8 °C improvement in thermal decomposition temperature compared to Neat PUE. Besides, the absorption energy and dynamic compression strength of composites were increased by 40.36 % and 38.26 %, respectively. Because reinforced nanofibers with crosslinking network structures improve the interface interaction between fillers and matrix, facilitate stress transfer and increase the energy threshold of thermal decomposition. The paper supplements the impact resistance analysis of PUE-based protective materials under impact loads, providing a systematic and scientific reference for the design and manufacture of impact resistant materials. [Display omitted] • Binary nanofibers based on phenol-amine chemistry were innovatively prepared by CNFs and ANFs. • Binary nanofibers remarkably increase the crosslinking density, facilitate stress transfer and dissipate accumulated heat. • PUE composites exhibit excellent energy absorption and thermomechanical properties. [ABSTRACT FROM AUTHOR]

Poly(lactic acid) (PLA) is the most promising candidate for biobased and biodegradable plastic which combines biocompatibility, renewability as well as excellent processability. However, toughening is still needed for PLA as to obtain materials suitable for broader applications. In this work, long-chain branched random copolymers poly(lactic acid-r-malic acid) (PMLA) were synthesized based on bio-resourced lactic acid (LA) and malic acid (MA) through polycondensation as toughening agent for PLA. The chemical structures of PMLA were characterized by 1H NMR and 1H–13C HSQC analysis. In the PLA and PMLA blends, PMLA has apparent effect on the crystallinity of PLA and the blends show a great increase of elongation at break to over 300 % even at low PMLA content of 2%wt. Furthermore, the thermal properties of the blend are characterized through DSC and the micro-structure investigated through Positron annihilation lifetime spectroscopic (PALS) technique. PMLA with long-chain branched topology shows an excellent capability in the toughening of PLA and maintains the total biodegradability of the resultant blend at the same time, that is critical for environment-friendly materials. [Display omitted] • The long-chain branched random copolymers PMLA were synthesized for the first time from nature-based resources. • PMLA is an ideal toughening agent for PLA, which combines mechanical property, biodegradability and economic advantages. • The improved mechanical properties are comprehensively verified through DSC and PALS analysis. • PMLA has the potential for post modification, which further expands the application fields of PLA materials. [ABSTRACT FROM AUTHOR]

Actuators have shown great potential application in many fields. Till now, it remains a challenge to design and exploit diverse modes actuators which can endure in hard environment by reconfiguration. Here, a series of shape memory polyarylene sulfide sulfone (SMP-PASS) shows excellent thermal properties, good mechanical properties and good shape memory behaviors were synthesized. The shape recovery temperature of can further increased by oxidizing thioether bonds to sulfone groups by facile oxidation treatment. According to the different temperature stimulus response of the samples before and after oxidation, herein, we propose a simple strategy to fabricate reconfigurable actuators that can be used in extreme environments by patterns in both plane and depth directions of SMP-PASS films by post-oxidation modification. SMP-PASS films after programming anisotropic can transform planar films into various 3D structure actuators under heating stimulation, unambiguous confirming that the facile oxidation method supplies an efficient route to yield multiple and thermal-resistant actuators. That not only supplies a novel, re-processable and fast-responsive shape memory polymer candidate, but also provides a facile and effective strategy to fabricate smart 3D actuators. [Display omitted] • The SMP-PASS shows excellent thermal properties, good shape memory behaviors and facile reconfigurable performance. • It provides a facile and effective strategy to fabricate smart 3D actuators. • The resultant polymers can be processed with both solution and facile melt method. [ABSTRACT FROM AUTHOR]

Polyurethane (PU) materials are widely used due to their excellent comprehensive properties including high strength, good wear resistance and weather resistance. To further improve the service life and safety of polyurethane materials, self-healing polyurethane materials have been developed. However, self-healing polyurethane generally suffers from low mechanical strength and poor thermal mechanical properties. Here, we have constructed a strong dual network by introducing benzene-1,4-diboronic acid (PDBA) into poly(urethane-urea) (PUU). On one hand, PDBA can form coordination bonds with nitrogen atoms in PUU, leading to the formation of a dual network consisting of boron-nitrogen coordination and hydrogen bonding. This dual network imparts PUU with a maximum tensile strength of 84.2 MPa. On the other hand, boron-nitrogen coordination is more stable than hydrogen bonding at high temperature, thereby significantly enhancing the thermal mechanical properties of PUU (the mechanical strength of PUU-PDBA-50 % and PUU-PDBA-100 % increased by 1.8 times and 2.4 times, respectively, compared to PUU at 100 °C). Meanwhile, the dynamic nature of the dual network endows the material with self-healing ability. [Display omitted] • H bonds and B/N coordination bonds endow PU with ultra-high mechanical properties. • The dynamic nature of the dual network endows the material with self-healing. • The dual network structure can significantly improve thermal mechanical properties. • High performance of the material can be achieved by simple blending. [ABSTRACT FROM AUTHOR]

The electrical conductivity of thermoplastic composites made of poly(3,4-ethylenedioxythiophene) (PEDOT) particles and poly(ethylene oxide) (PEO) matrices is here investigated, in particular using a manufacturing process based on twin-screw extrusion. PEDOT particles without PSS were first synthesized by oxidative polymerization in an aqueous medium and characterized using various techniques (conductivity measurements, SEM, TGA, laser granulometry, XRD and XPS). The polymerization temperature of PEDOT particles was found to be a crucial factor. A maximal conductivity of 50 S.cm−1 was obtained when synthesized at ambient temperature. Relationships between the polymerization temperature and the structure of PEDOT particles were revealed and discussed. PEDOT particles were then incorporated up to 60 wt% into PEO matrix by twin-screw extrusion to manufacture electrically-conductive PEO/PEDOT thermoplastic composites. Their electrical conductivity increased with the PEDOT content and outstanding electrical conductivities up to 12 S.cm−1 were reached. The electrical percolation of this system was determined and discussed based on morphological studies by SEM and X-Ray tomography. The effect of PEDOT concentration on thermal properties of PEO matrices was also revealed by DSC. This work provides a novel approach for the manufacture of thermoplastic composites with high electrical conductivities using industrial technologies with multiple applicative perspectives, in particular into polymer-based electronics. [Display omitted] • Electrically-conductive PEDOT particles up to 50 S cm−1 were successfully obtained by an oxidative polymerization process. • Polymerization temperature has been identified as the key parameter to obtain highly conductive PEDOT particles and relationships with structural features were explored. • Incorporation of PEDOT particles into a PEO thermoplastic matrix was successfully performed up to 60 wt% by twin screw extrusion. • PEO/PEDOT thermoplastic composites with high electrical conductivities up to 12 S. cm−1 were successfully obtained. [ABSTRACT FROM AUTHOR]

Developing new chemically recyclable polymers provides an opportunity for establishing a circular plastic economy. However, it is still challenging to reconcile both polymer recyclability and material properties. Herein, we aimed to exploit copolymerization of 3-methyl-dithian-2-one (Me-DTO) and thiovalerolactone (TVL) to access chemically recyclable polythioesters with high-performance material properties. Adjusting the copolymer compositions allowed to modulate the thermal and mechanical properties of the resulting copolymers extensively. Ultimately, polyolefin-like mechanical properties was achieved for P[(Me-DTO) 100 - co -(TVL) 900 ] (σ B = 33.87 ± 4.79MPa and ε B = 638 % ± 112 %). These copolymers were capable of depolymerizing into their monomers in solution or bulk efficiently with high yields of >95 %, thus establishing their circular life cycle. [Display omitted] • Copolymerization strategy. • Chemically recyclable polythioesters. • Polyolefin-like high mechanical strength and ductility. [ABSTRACT FROM AUTHOR]

Cellulose triacetate (CTA) is a bio-based chiral polymer with the rare property of forming homogenous solid blends with several compounds. The controlled modification of the conformational freedom of the polymer chains by plasticizers could enable the tuning of its selectivity towards optical isomers. We survey the blends of CTA with four individual ionic liquids (ILs), with a focus on the action of the individual counter ions. Blends of CTA with four ILs being, the combinations of two cations (BMIM and BMPy) and two anions (Tf 2 N and TfO), were studied using thermal analysis methods (TGA, DMA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and sorption tests. Blends containing the ILs with Tf 2 N, which undergoes cis-trans stabilization, were less effective plasticizers of CTA than the TfO-based ILs when sensed as decreases in the temperatures of glass transition (T g) and degradation (T d). The exchange of the cations caused discernible but far smaller changes of T g and T d. All studied ILs caused the disappearance of the Raman band of CTA at 702 cm−1, which we assign to the skeletal vibrations of the pyranose ring using the ab-initio calculation, and pronounced wavenumber shifts of the bands of the methoxy group (at 1163 cm−1) and pyranose ring (at 1075 and 1085 cm−1) in CTA. This indicates the increased intra-chain mobility and physical interactions between CTA and IL. TEM analysis confirmed the existence of interactions between the ILs and CTA chain, and the amplification of plasmon resonance. Sorption uptakes of some enantiomers (carvone, 1-phenylethanol and 1-amino-2-propanol) confirmed the chiral behavior of the CTA-based polymers. For instance, the sorption uptake of (S)-(−)-1-phenylethanol in pure CTA was by 30 % higher than that of (R)-(+)-1-phenylethanol. Moreover, the sorption uptakes of (R)-(+)- and (S)-(−)- carvone enantiomers increased by 47 % and 260 %, respectively, due to blending CTA with 20 wt % of [BMPy][TfO]. [Display omitted] • CTA membranes modified by ionic liquids show good mechanical and thermal stability. • Existence of weak non-binding force interactions between IL and CTA are indicated. • No phase separation of CTA and ionic liquid is observed using SEM and TEM. • Addition of ionic liquid can reverse ratio of sorption of pure enantiomers in CTA. [ABSTRACT FROM AUTHOR]

Electric fields are effective in inducing the orientation of highly thermally conductive fillers in polymers to improve the thermal conductivity of composites. However, the study of the effect of pulsed square wave electric field on thermal conductivity of composites is relatively rare. In this paper, the effect of electric field strength, frequency, and application time of pulsed square-wave electric field on the thermal conductivity of composites is investigated by utilizing the pulsed square-wave electric field to induce the orientation arrangement of h-BN in epoxy resin (EP). The results show that the thermal conductivity of the composites increases with the increase of the electric field strength and the decrease of the frequency, and does not change significantly with the application time. The highest thermal conductivity of 0.453 W/(m·K), which is 3.24 times higher than that of the epoxy resin, was obtained for the composites by applying a pulsed square-wave electric field of 200 V/mm at 0.001 Hz for 1 h with 10 wt% load. It is 1.94 times higher than that of the sample without electric field induction at the same load. This paper also establishes a mathematical relationship between the degree of orientation of h-BN and the thermal conductivity of the composite material, which expands the scope of application of the thermal conductivity model and increases the accuracy of the model calculation. The method is simple in process and suitable for a wide range of high thermal conductivity composite applications with great potential for development. [Display omitted] • The structure of composites was adjusted by pulsed-square wave electric field. • The high in-plane thermal conductivity of h-BN is fully exploited. • New thermal conductivity model on boron nitride orientation was established. [ABSTRACT FROM AUTHOR]