Effect of incorporation of graphene oxide and graphene nanoplatelets on mechanical and gas permeability properties of poly(lactic acid) films

Nanocomposite thin films of poly(lactic acid) (PLA) were produced incorporating small amounts (0.2 to 1 wt%) of graphene oxide (GO) and graphene nanoplatelets (GNP). The films were prepared by solvent‐casting. Mechanical properties were evaluated for plasticized (by residual solvent) and unplasticized films. Plasticized nanocomposite films presented yield strength and Young's modulus about 100% higher than those of pristine PLA. For unplasticized films improvements in tensile strength and Young's modulus were about 15 and 85%, respectively. For both film types, a maximum in mechanical performance was identified for about 0.4 wt% loadings of the two filler materials tested. Permeabilities towards oxygen and nitrogen decreased, respectively, three‐ and fourfold in films loaded with both GO or GNP. The glass transition temperature showed maximum increases, in relation to unloaded PLA films, of 5 °C for 0.4 wt% GO and 7 °C for 0.4 wt% GNP, coinciding with the observed maxima in mechanical properties. Copyright © 2012 Society of Chemical Industry     

Poly (vinyl alcohol)/polylactic acid blend film with enhanced processability,compatibility, and mechanical property fabricated via melt processing

Poly (vinyl alcohol)/polylactic acid (PVA/PLA) blend film, which is environment friendly and has potential applications in food and electronic packaging fields, was fabricated by melt extrusion casting. Fourier transform infrared spectroscopy analysis confirmed the formation of the hydrogen bonding between PLA and PVA, which improved the compatibility of PLA with PVA, making PLA uniformly dispersed in PVA matrix as small spheres, even when PLA content increase to 15 wt%. In this way, the original hydrogen bond network among PVA was disturbed and the chain mobility of PVA was activated, endowing PVA/PLA blends with lower melt viscosity than bot modified PVA and PLA, and the blend films with the increased crystallinity, mechanical property, and water resistance. Compared with PVA film, the crystallinity, tensile strength and Young's modulus of the blend film with 15 wt% PLA, respectively, increased by 15.1%, 9 and 51 MPa, and the water contact angle enlarged from 23° to 60°.     

Preparation of polybenzimidazole/functionalized carbon nanotube nanocomposite films for use as protective coatings

Functionalized multi‐walled carbon nanotubes (MWCNTs) via microwave‐induced polymerization modification route, and polybenzimidazole (PBI) nanocomposite films containing 0.1‐5 wt% functionalized MWCNTs were successfully synthesized. The functionalized MWCNTs were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X‐ray photoelectron spectroscopy (XPS). The results verify that the polymer was successfully grafted to the MWCNTs with a polymer layer that was several nanometers thick. The TGA results showed that the quantity of the attached polymer reached approximately 9.4 wt%. The mechanical properties of the nanocomposite films were measured by tensile test and dynamic mechanical analysis (DMA). The tensile test results indicated that the Young's modulus increased by about 43.9% at 2 wt% CNT loading, and further modulus growth was observed at higher filler loading. The DMA studies indicated that the nanocomposite films had a higher storage modulus than pure PBI film in the temperature range of 30‐300°C, and the storage modulus was maintained above 0.82 GPa. Simulation results confirmed that the PBI nanocomposite films had desirable mechanical properties for use as a protective coating. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.     

A study on high-performance poly(azo-pyridine-benzophenone-imide) nanocomposites via self-reinforcement of electrospun nanofibers

In this study, initially high molecular weight poly(azo-pyridine-benzophenone-imide) (PAPBI) has been fabricated using facile approach. Uniformly aligned electrospun PAPBI and PAPBI/multi-walled carbon nanotube (MWCNT) nanofibers were then produced via electrospinning of desired solutions. Self-reinforcement technique was used to fabricate PAPBI-based nanofiber reinforced films. Uniform dispersion, orientation and adhesion between carbon nanotubes and polymer improved the physical properties of resulting nanocomposites. Fourier transform infrared spectroscopy was used to identify the structures of polymer and self-reinforced nanocomposite films. Scanning and transmission electron microscopy showed that the electrospun PAPBI/MWCNT nanofibers were uniformly aligned and free of defects. Moreover, polyimide matrix was evenly coated on the surface of electrospun nanofibers, thus, preventing the fibers from bundling together. Samples of 1–3 wt% of as-prepared electrospun nanofibers were self-reinforced to enhance the tensile strength of the films. Films of 3 wt% PAPBI/MWCNT nanofiber-based nanocomposite showed higher value in tensile strength (417 MPa) relative to 3 wt% PAPBI nanofibers (361 MPa) reinforced film. Tensile modulus of the PAPBI/MWCNT system was also significantly improved (19.9–22.1 GPa) compared with PAPBI system (13.9–16.2 GPa). Thermal stability of PAPBI/MWCNT nanofibers reinforced polyimide was also superior having 10 % gravimetric loss at 600–634 °C and glass transition temperature 272–292 °C relative to the neat polymer (T ₁₀ 545 °C, T _g 262 °C) and PAPBI nanofiber-based system (T ₁₀ 559–578 °C, T _g 264–269 °C). New high-performance self-reinforced polyimide nanocomposites may act as potential contenders for light-weight aerospace materials.     

Physico-chemical,thermal, and mechanical properties of PLA-nHA nanocomposites: Effect of glass fiber reinforcement

In this study, tri-layered composites were prepared by reinforcing poly-lactic acid (PLA) nano-hydroxyapatite (n-HA) (1 and 5 wt%) and 20 mol% continuous phosphate glass fibers (PGF). Initially, the effect of addition of 1 and 5% n-HA on the structural, thermal, mechanical, and thermo-mechanical properties of 100% PLA was investigated. With 5 wt% n-HA addition the tensile modulus (TM), flexural modulus (FM), tensile strength (TS), and flexural strength (FS) of 100% PLA was improve by 14.9, 47.4, 6, and 32.9%, respectively. Whereas, the un-notched impact strength of the nanocomposites suffer 2% deterioration. However, T _g decreased by 0.3°C and T _c increased by 10°C as 5 wt% n-HA was added to 100% PLA. Afterwards, the 5% n-HA/PLA composite were reinforced with 20 mol% continuous PGF and the TM, FM, TS, and FS of the tri-layered composites were 162.6, 412.5, 28.4, and 157.4% higher as compared to 100%PLA. Furthermore, the storage modulus of the 1% n-HA-filled composites was 500 MPa lower than 100%PLA, while 5 wt% n-HA-filled composites showed similar storage modulus as 100% PLA. 5 wt% n-HA-filled composite showed the highest peak of loss modulus which may be attribute to the chain segment of PLA matrix after the incorporation of HA. Thus, n-HA and PGF reinforcement resulted in improved mechanical properties of the composites and have great potential as biodegradable bone fixation device with enhanced load-bearing ability.     

A gelatin/PLA-b-PEG film of excellent gas barrier and mechanical properties

A polylactic acid-polyethylene glycol block copolymer (PLA-b-PEG) was used as an additive to prepare gelatin/PLA-b-PEG blend films for the first time. The PEG molecule block enhanced the compatibility of the PLA molecule block with gelatin, which greatly improved the excellent mechanical and gas barrier properties of the gelatin film. The film contained 5 wt% PLA-b-PEG possessed the highest tensile strength and the highest elastic modulus. When the PLA-b-PEG content further increased to 20 wt%, the tensile strength, elastic modulus and elongation at the break of the blend film were all higher than pure gelatin film, suggesting that the gelatin/PLA-b-PEG blend film was pliable and tough. The blend film possessed not only excellent oxygen barrier property, but also a much-improved water barrier property. The degradation rate of the blend film was elongated controllably by regulating the content of the PLA-b-PEG copolymer. The blend film showed great potential in the application of food packaging.     

Enhanced mechanical and thermal properties of graphene nanoplatelets-reinforced polyamide11/poly(lactic acid) nanocomposites

The present paper aims to obtain a sustainable nanocomposite by using bio-based polyamide 11 and biodegradable poly (lactic acid) blend as matrix and graphene nanoplatelets (GNP) as nanofiller. GNP was incorporated in the PA11/PLA blend matrix in the ratio of 0.5-1-3-5-10 wt% through the twin-screw extruder. The crystallinity of PA11 in the blend, which was 12.9%, increased with the inclusion of GNP, and the highest crystallinity value was observed at 20% for the 1GNP sample. The crystallinity of PLA in the blend, which was 2.3%, increased to 4.6% with 5 wt% GNP addition. The inclusion of GNP to PA11/PLA improved the thermal degradation temperatures and increase the char residue. Also, increments were observed for storage modulus, loss modulus, and glass transition temperature of the matrix with the inclusion of GNP. The addition of GNP caused the tensile strength of the matrix to increase first and then decrease at higher amounts due to the agglomerations. 0.5–1 wt% GNP increased tensile strength by 10% and 5%, respectively. Increasing the amount of GNP to 10 wt% led to a sharp decrease in tensile strength by 24%. Overall, GNP is a suitable nanofiller to enhance the thermal and mechanical features of the PA11/PLA blend.     

Enhanced mechanical and anisotropic thermal conductive properties of polyimide nanocomposite films reinforced with hexagonal boron nitride nanosheets

To attain thermally conductive but electrically insulating polymer films, in this study, polyimide (PI) nanocomposite films with 1–30 wt% functionalized hexagonal boron nitride nanosheets (BNNSs) were fabricated via solution casting and following imidization. The microstructures, mechanical and thermal conductive properties of PI/BNNS nanocomposite films were examined by taking account of the relative content, anisotropic orientation, and interfacial interaction of BNNS and PI matrix. The scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffractometry data revealed that BNNSs with hydroxy and amino functional groups have specific molecular interactions with PI matrix and they form stacked aggregates in the nanocomposite films with high BNNS loadings of 10–30 wt%. The tensile mechanical strength/modulus, thermal degradation temperatures, and thermal conductivity of the nanocomposite films were found to be significantly enhanced with increasing the BNNS loadings. For the nanocomposite films with 1–30 wt% BNNS loadings, the in-plane thermal conductivity was measured to be 1.82–2.38 W/mK, which were much higher than the out-of-plane values of 0.35–1.14 W/mK. The significant anisotropic thermal conductivity of the nanocomposite films was found to be owing to the synergistic anisotropic orientation effects of both BNNS and PI matrix. It is noticeable that the in-plane and out-of-plane thermal conductivity values of the nanocomposite film with 30 wt% BNNS were ~1.31 and ~3.35 times higher than those of neat PI film, respectively.     

Morphology and Properties of Waterborne Polyurethane/CNT Nanocomposite Adhesives with Various Carboxyl Acid Salt Groups

Three series of waterborne polyurethane (WBPU)/carbon nanotube (CNT) nanocomposites were prepared, and their morphology and properties with various 2,2-dimethylol propionic acid (DMPA) and CNT contents were investigated. The CNTs were homogeneously dispersed up to the optimum content in WBPU/CNT nanocomposite films. The degree of homogeneous CNT dispersion increased with increasing DMPA content in WBPU/CNT nanocomposite films. The optimum CNT content showed maximum tensile strength, Young's modulus and adhesive strength of WBPU/CNT nanocomposite film. The optimum CNT contents for WBPU/CNT nanocomposite samples containing 3.61, 5.16 and 5.86 wt% DMPA were about 0.50, 1.00 and 1.50 wt%, respectively. The WBPU/CNT nanocomposite adhesive showed higher adhesive strength at moderately high temperatures (40/60/80/100°C) compared to conventional WBPU. The highest adhesive strength at moderately high temperatures was found with 5.86 wt% DMPA and 1.5 wt% CNT content.     

Mechanical properties and thermostability of polyimide/mesoporous silica nanocomposite via effectively using the pores

Series of polyimide (PI)/mesoporous silica nanospheres (MSNs) nanocomposite films with different contents of MSNs were successfully prepared via a simple wet impregnation method. The morphologies, microstructures, mechanical properties, transmittance, and thermal properties of the prepared PI and the PI/MSNs nanocomposite films were investigated in detail. As a result, the thermal stability and mechanical performances of PI were obviously improved by incorporating MSNs into PI. The tensile stress and Young's modulus of the nanocomposite film with 5 wt % MSNs were raised up to 97.65 MPa and 2220.06 MPa, which are greatly higher than the values of 82.51 MPa and 1440.86 MPa for the pure PI film. Experimental results confirmed that the designed polymerization tactic, which occurred in the pores of the MSNs, facilitated to enhance the mechanical and physical performances of the PI/MSNs nanocomposite films, and definitely induced better integration between organic matrix and inorganic nanofillers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41173.     

Synthesis and mechanical properties of polybenzimidazole nanocomposites reinforced by vapor grown carbon nanofibers

Polybenzimidazole (PBI) nanocomposites containing 0.5–5 wt% vapor grown carbon nanofibers (VGNFs) were successfully synthesized by solvent evaporation method. Fracture morphology examination confirmed the uniform dispersion of VGNFs in the matrix. The mechanical properties of neat PBI and the nanocomposites were systematically measured by tensile test, dynamic mechanical analysis (DMA), hardness measurement, and friction test. Tensile tests revealed that Young's modulus increased by about 43.7% at 2 wt% VGNFs loading, and further modulus growth was observed at higher filler loadings. DMA studies showed that the nanocomposites have higher storage modulus than neat PBI in the temperature range of 30–350°C, holding storage modulus larger than 1.54 GPa below 300°C. Outstanding improvement of hardness was achieved for PBI upon incorporating 2 wt% of VGNFs. The results of friction test showed that coefficient of friction of PBI nanocomposites decreased with VGNFs content compared with neat PBI. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Morphology,thermal, mechanical,and barrier properties of graphene oxide/poly(lactic acid) nanocomposite films

To improve the physical and gas barrier properties of biodegradable poly(lactic acid) (PLA) film, two graphene nanosheets of highly functionalized graphene oxide (0.3 wt% to 0.7 wt%) and low-functionalized graphene oxide (0.5 wt%) were incorporated into PLA resin via solution blending method. Subsequently, we investigated the effects of material parameters such as loading level and degree of functionalization for the graphene nanosheets on the morphology and properties of the resultant nanocomposites. The highly functionalized graphene oxide (GO) caused more exfoliation and homogeneous dispersion in PLA matrix as well as more sustainable suspensions in THF, compared to low-functionalized graphene oxide (LFGO). When loaded with GO from 0.3 wt% to 0.7 wt%, the glass transition temperature, degree of crystallinity, tensile strength and modulus increased steadily. The GO gave rise to more pronounced effect in the thermal and mechanical reinforcement, relative to LFGO. In addition, the preparation of fairly transparent PLA-based nanocomposite film with noticeably improved barrier performance achieved only when incorporated with GO up to 0.7wt%. As a result, GO may be more compatible with hydrophilic PLA resin, compared to LFGO, resulting in more prominent enhancement of nanocomposites properties.     

Development of plasticized PLA/NH2‐CNTs nanocomposite: potential of NH2‐CNTs to improve electroactive shape memory properties

A polymer nanocomposite system comprising epoxidized soya oil plasticized‐polylactic acid (PLA) and amine functionalized carbon nanotubes (NH₂ functionalized‐CNTs) has been prepared with the aim of producing electrically conductive PLA products suitable for shape memory (SM) applications. An influence of the addition of NH₂ functionalized‐CNTs on thermal, mechanical properties, and morphology development of plasticized PLA/NH₂ functionalized‐CNTs nanocomposite was investigated by differential scanning calorimetry, tensile tests, scanning electron microscope, and atomic force microscopy, respectively. In addition, electroactive SM behavior in resulting nanocomposite was evaluated by a bending test, and the recovery process was recorded with video camera. The results showed that SM behavior in nanocomposite was influenced by NH₂ functionalized‐CNTs weight percent in matrix. Nanocomposite with 5 wt% NH₂ functionalized‐CNTs showed optimum values of shape recovery due to its relatively high electrical conductivity, and an adequate degree of crosslinking between NH₂ functionalized‐CNTs and plasticized PLA matrix. However, more than 5 wt% loading of NH₂ functionalized‐CNTs dropped down an elongation at break, while tensile at break increased with the increasing of CNTs weight percent in matrix. Interesting point in this study is that all improvements in the properties of resulting PLA/NH₂ functionalized‐CNTs nanocomposite sheet were observed at very low filler content, while other literature reports where large quantities of CNTs were used. POLYM. COMPOS., 35:2129–2136, 2014. © 2014 Society of Plastics Engineers     

Mechanical,Thermal, and Electrical Properties of Epoxy Matrix Composites Reinforced With Polyamide-Grafted-MWCNT/poly(azo-pyridine-benzophenone-imide)/Polyaniline Nanofibers

Friedel-Crafts acylation and in situ polymerization were adopted to graft polyamide on multi-walled carbon nanotube (MWCNT) surface to form MWCNT-PA using γ-Phenyl-?-caprolactone. Via electrospinning, MWCNT-PA/PAPBI and MWCNT-PA/PAPBI/PANI nanofibers were prepared using MWCNT-PA, poly(azo-pyridine-benzophenone-imide) (PAPBI) and polyaniline (PANI) and DGEBA as matrix. Compared with 3 wt% MWCNT-PA/PAPBI nanofibers (20.2 GPa), tensile modulus for film reinforced with 3 wt% MWCNT-PA/PAPBI/PANI nanofibers (27.6 GPa) was considerably increased. Thermal stability of MWCNT-PA/PAPBI/PANI nanofibers reinforced epoxy was higher with T₁₀ 633–654°C and T_g 283–291°C relative to DGEBAMWCNT-PA/PAPBI system. The filler loading also increased the electrical conductivity of DGEBA/MWCNT-PA/PAPBI/PANI from 3.44 to 6.01 S cm^?1.     

Effect of peanut shell content on mechanical,thermal, and biodegradable properties of peanut shell/polylactic acid biocomposites

Peanut shell (PNS) was combined with polylactic acid (PLA) to form biocomposites. The biocomposites, with up to 40 wt% PNS, were prepared using a twin–screw extruder. The effect of PNS content on the thermal, mechanical, thermomechanical, morphological, and biodegradable properties was studied. The results showed that the addition of PNS caused a reduction of the melting temperature and the decomposition temperature. Furthermore, the crystallinity of the biocomposites slightly increased with increasing PNS up to 30 wt%. The morphological study showed poor interfacial adhesion between the PNS and PLA matrix. Nevertheless, the mechanical properties revealed that the maximum tensile strength and Young's modulus were at a 30 wt% PNS loading and decreased as more PNS was incorporated into the PLA matrix. The impact strength decreased with an increase in PNS content. The addition of PNS showed significantly improvement of the storage modulus of PLA at high temperature (>80°C). Moreover, the presence of PNS enhanced the biodegradability of the biocomposites. POLYM. COMPOS., 38:682–690, 2017. © 2015 Society of Plastics Engineers     

Improved properties of highly oriented graphene/polymer nanocomposites

A kind of molecular‐level dispersed and highly oriented graphene monolayer nanocomposite film was successfully obtained by in situ reduction of phenyl isocyanate functionalized graphite oxide (RPIGO) in N,N‐dimethylformamide in the presence of polystyrene (PS). Atomic force microscopy and transmission electron microscopy results show that the RPIGO monolayers were not only homogeneously intercalated into the PS matrix but also arranged parallel to the surface of the nanocomposite films. Because of the efficient interaction between the graphene monolayers and PS matrix, the mechanical properties of the graphene‐based nanocomposite films improved significantly. Compared with the pure PS film, a 28.4% increase in the Young's modulus and a 27.8% improvement in the tensile strength of the RPIGO–PS nanocomposites films were obtained with the addition of only 0.5 wt % graphite oxide. The glass‐transition temperature and onset degradation temperature of PS also increased from 96.6 and 427°C to 103.2 and 439°C, respectively. The improvement of the properties was mainly due to the large lateral thickness ratio and the high orientation of graphene monolayers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

海泡石增强壳聚糖/玉米醇溶蛋白复合膜的制备及性能

采用流延成膜法制备了不同海泡石(SP)质量分数的壳聚糖(CS)/玉米蛋白(ZN)复合膜。研究了SP质量分数对CS/ZN复合膜机械性能和断面形貌的影响,分析了SP对CS/ZN复合膜的增强机理。扫描电子显微镜结果表明,SP粒子在复合膜中分散较好,CS与ZN之间有较好的相容性。随着SP质量分数增加,SP/CS/ZN膜拉伸强度先增加后减小,当SP质量分数为2%时,其拉伸强度达到最大值21.1 MPa,比纯CS/ZN提高了8.1%;而断裂伸长率随着SP质量分数先增加后降低,从15.3%下降为7.5%;同时复合膜的耐水性能上升,复合膜的吸水率随着SP质量分数增加先减小后增加,在8%时达到最小值。SP的引入导致复合膜的透光性能下降,SP质量分数为6%时在波长800 nm处光透过率下降约20%。     

Effect of nitrile functionalized graphene on the properties of poly(arylene ether nitrile) nanocomposites

In this study, novel nitrile functionalized graphene (GN‐nitrile)/poly(arylene ether nitrile) (PEN) nanocomposites were prepared by an easy solution‐casting method and investigated for the effect of surface modification on the dielectric, mechanical and thermal properties. Graphene (GN) was first functionalized by introduction of nitrile groups onto the GN plane, which was confirmed by scanning electron microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, thermogravimetric analysis and dispersibility research. Compared with pure GN, the grafted nitrile groups on the GN‐nitrile can interact with nitrile groups in PEN and lead to flat but better dispersion and stronger adhesion in/to the PEN matrix. Consequently, GN‐nitrile had a more significant enhancement effect on the properties of PEN. The dielectric constant of the PEN/GN‐nitrile nanocomposite with 5 wt% GN‐nitrile reaches 11.5 at 100 Hz, which is much larger than that of the pure PEN matrix (3.1). Meanwhile, dielectric loss is quite small and stable and the dielectric properties showed little frequency dependence. For 5 wt% GN‐nitrile reinforced PEN composites, increases of 17.6% in tensile strength, 26.4% in tensile modulus and 21 °C in T_d5% were obtained. All PEN/GN‐nitrile nanocomposite films can stand high temperature, up to 480 °C. Hence, novel dielectric PEN/GN‐nitrile nanocomposite films with excellent mechanical and thermal properties can be used as dielectric materials under some critical circumstances such as high wear and temperature. Copyright © 2012 Society of Chemical Industry     

Preparation of Poly(Vinyl Alcohol) Nanocomposite Films Reinforced with Poly(Amide–Imide)/CuO Having N-trimellitylimido-L-valine Linkages for the Improvement of Mechanical and Thermal Properties

In this investigation, nanocomposite films were fabricated by dispersion of poly(amide–imide)/CuO nanocomposites as nanofiller in the poly(vinyl alcohol) matrix via an ultrasonic process. The nanofiller was prepared and mixed with PVA matrix. After dispersion of nanofiller into the poly(vinyl alcohol), the mechanical properties of the nanocomposites were improved. For example, the addition of 6 wt% nanofiller into the poly(vinyl alcohol) matrix enhanced the tensile modulus by 39%. The residual weight at 800°C was 7% for pure poly(vinyl alcohol) while the nanocomposites illustrated 12–19% residue at this temperature.     

Relationship between structure and dynamic mechanical properties of a carbon nanofiber reinforced elastomeric nanocomposite

The tensile and dynamic mechanical properties of a nanocomposite, containing modified carbon nanofibers (MCNFs) homogenously dispersed in an elastomeric ethylene/propylene (EP) copolymer semicrystalline matrix (84.3 wt% P), have been correlated with the structure development. These properties were characterized by in situ synchrotron X-ray diffraction during stretching, dynamic mechanical analysis and X-ray analysis techniques over a wide temperature range. Upon sequential drawing, the tensile strength of the nanocomposite film was notably higher than that of the unfilled polymer even though both samples exhibited a similar amount of crystal fraction and the same degree of crystal orientation, revealing the effect of nanofiller reinforcement in the semicrystalline matrix. The mechanical spectra of the 10 wt% MCNF filled samples in both stretched and non-stretched states showed broadening of the elastic modulus at high temperatures, where the corresponding crystallinity index also decreased. It is conceivable that a significant fraction of chain orientation is induced in the vicinity of the nanofillers during stretching, and these stretched chains with reduced mobility significantly enhance the thermal mechanical properties.