Heat Resistance Of Poly Research Articles

Enhanced strength, toughness and heat resistance of poly (lactic acid) with good transparency and biodegradability by uniaxial pre-stretching

Sustainable poly (lactic acid) (PLA) with excellent strength, toughness, heat resistance, transparency, and biodegradability was achieved by uniaxial pre-stretching at 70 °C. The effect of pre-stretched ratio (PSR) on the microstructure and properties of the PLA was investigated. The undrawn PLA was brittle. However, after pre-stretching, the elongation at break was increased significantly. The maximum value of 161.2 % was obtained at pre-stretching ratio (PSR) of 1.0. With the increase of PSR, the modulus and strength were improved obviously (from 1601 MPa and 60.2 MPa for undrawn PLA to 2932 MPa and 106.3 MPa for the ps-PLA at PSR =3.0). Meanwhile, the heat resistance of PLA was improved obviously with the increase of PSR. For the ps-PLA3.0, there were almost no deformation and shrink at 140 °C. Interestingly, after pre-stretching, the PLA still maintained the good transparency and biodegradability. The brittleness for undrawn PLA was attributed to the network structure of cohesional entanglements. After pre-stretching, the destruction of the network structure and formation of the orientation, mesophase and oriented nanosized crystalline phase lead to the increased the toughness, strength and heat resistance without sacrificing the transparency and biodegradability. This work provides a significant guidance for the fabrication of PLA material with excellent comprehensive performance including strength, toughness, heat resistance, transparency, and biodegradability.

Polybenzoxazines containing borosiloxane structures as high-temperature resistance (T g > 300 °C) and environment-friendly flame-retardant materials

A series of borosiloxane structures-containing polybenzoxazines (PBZs) with intrinsic environment-friendly flame-retardant properties and high-temperature resistance are investigated in this study. Initially, borosiloxane structures-containing benzoxazine macromonomers (BZ-BSiO-X) were synthesized through a condensation reaction between silicon ethoxy groups-containing benzoxazine monomers (P-mdes), boric acid (BA) and diphenyldimethoxysilane (DPDMS) with varying feed ratios. Subsequently, the benzoxazine groups in BZ-BSiO-X underwent ring-opening polymerization at elevated temperatures to produce poly(BZ-BSiO-X). The properties of poly(BZ-BSiO-X) were evaluated using Dynamic Mechanical Analysis, Thermogravimetric Analysis and an Oxygen Index instrument. The results show that the heat resistance of poly(BZ-BSiO-X) is enhanced by the cross-linking structures formed by the P-mdes segment and B-N coordination interaction, leading to their glass transition temperatures (T g, tan δ) exceeding 300 °C. The thermal stability and flame-retardant properties of poly(BZ-BSiO-X) are reinforced via the borosiloxane structures formed through DPDMS and BA, resulting in a 5% weight loss temperatures (T d5) around 400 °C and limiting oxygen index (LOI) values above 30. These polymers, containing environment-friendly flame-retardant boron (B) and silicon (Si) elements, exhibit potential as alternatives to halogen- or phosphorus-containing flame-retardant materials and are expected to be used in various fields as environment-friendly flame-retardant materials.

Enhancement of the compatibility, mechanical properties, and heat resistance of poly(butylene succinate-co-terephthalate)/poly(butylene succinate) blends by the addition of chain extender and nucleating agent

Enhancement of the compatibility, mechanical properties, and heat resistance of poly(butylene succinate-co-terephthalate)/poly(butylene succinate) blends by the addition of chain extender and nucleating agent

Enhancing the crystallinity and heat resistance of poly(ethylene terephthalate) using ZnCl2‐ionized polyamide‐66 as a heterogeneous nucleator

AbstractTo achieve the maximal improvement in the crystallization rate and heat resistance of poly(ethylene terephthalate) (PET), 2.6 mol% of ZnCl2 ionized polyamide (PA)‐66 (PA‐66–Zn), with a strong coordination ability, is prepared and used as PET nucleator. This study found that the PA‐66–Zn heterogeneously nucleates PET more effectively than the CaCl2‐ionized PA‐66 and non‐ionized PA‐66 by differential scanning calorimetry, crystallization kinetics, X‐ray diffraction, and polarized optical microscopy. This is probably a result of the introduction of stronger ion–dipole interactions (IDIs) between the PET esters and the ionized‐PA‐66 ZnCl2‐coordinating amides, which obviously heightens the PET/PA‐66–Zn interfacial compatibility. As shown by scanning electron microscopy, the compatibilization through an appropriate concentration of IDIs promotes the formation of smaller and denser PA‐66 crystals with immensely increased nucleator efficiency. Furthermore, the PET/PA‐66–Zn with significantly improved crystallinity displays a remarkable increase in heat‐resistant temperature, at 21.6 and 55.1°C higher than that of PET/PA‐66 and PET, respectively. The results demonstrate that the PA‐66–Zn can act as a superior nucleator and as an outstanding heat‐resistant agent for PET.

Extraordinary toughness and heat resistance enhancement of biodegradable PLA/PBS blends through the formation of a small amount of interface-localized stereocomplex crystallites during melt blending

Simultaneously improving the toughness and heat resistance of poly(l-lactide) (PLLA) is significant for expanding biodegradable materials' application range. In this work, reactive compatibilizers containing PBS and PLLA (PBS-St-GMA-PLLA (SGL)) or poly(d-lactide) (PBS-St-GMA-PDLA (SGD)) were synthesized and incorporated in blends of commercial PLLA and PBS as compatibilizers. The in situ formation of stereocomplex (SC) crystallites of PLA at the interface of PLLA and PBS was successfully achieved through simple melt blending. The effects of SC crystallites, amount of compatibilizers on morphology, crystallization behavior, mechanical properties, heat resistance and degradability properties of PLLA/PBS blends were studied. Morphological evolution showed that SGL and SGD significantly improved the compatibility of PLLA/PBS blends. After incorporating 5% SGD, the elongation at break and notched impact strength of PLLA/PBS blends with SC crystallites reached 273% and 34 kJ/m2, respectively, 12 and 5 times than that of pristine PLLA/PBS blends. As compared with PLLA/PBS/SGL blends that cannot form SC crystallites, the tensile strength of the blends was effectively improved by the presence of SC crystallites, ascribing to improved interfacial compatibility and remarkable acceleration in matrix crystallization kinetics of PLLA. Consequently, the blends containing 5% SGD exhibited excellent heat resistance (E′80°C > 680 MPa) after brief annealing, which far exceeded the PLLA or PLLA/PBS blends. This work may provide a feasible way to prepare PLLA-based materials with excellent comprehensive properties by the formation of SC crystallites.

Simultaneously Enhancing the Fire Retardancy and Heat Resistance of Stereo-Complex-Type Polylactic Acid.

Polylactic acid (PLA) is considered to be the material with great application potential in the 21st century which has aroused wide research interest. However, PLA is a highly flammable material and exhibits low heat distortion temperature, which greatly limits its application in many fields. In this work, aluminum diethyl phosphinate (ADP) and poly (d-lactic acid) (PDLA) are used to improve fire retardancy and heat resistance of poly (l-lactic acid) (PLLA). PLLA/PDLA with the presence of 15 wt % ADP exhibited the limiting oxygen index (LOI) value at 26%, and the peak heat release rate (pHRR) and total heat release decreased, respectively, by 14.03 and 24.42% from 500 to 429 kW/m2 and 86 to 65 MJ/m2. The melt dripping phenomenon was suppressed obviously. The addition of ADP realized the flame-retardant effect from both the condensed phase and gas phase. Moreover, the results showed that the addition of ADP promoted the formation of stereo crystals and increased the crystallization temperature to 175 °C. The heat distortion temperature (HDT) of the PLLA/PDLA sample with 15 wt % ADP can be as high as 170.4 °C, which marks significant improvement in the heat resistance of PLA. The mechanical property test results showed that ADP has little effect on the mechanical properties of the composites. This work opens a window to realize the heat-resistant and anti-dripping fire-retardant PLA.

Controlling Crystallization, Mechanical Properties and Heat Resistance of Poly(L-lactide)-b-polyethylene glycol)-b-poly(L-lactide) Bioplastic by Melt Blending with Low Molecular Weight Poly(D-lactide)/Poly(L-lactide) Mixtures

The crystallization behaviour, mechanical properties and heat resistance were determined for mixtures of poly(L-lactide)-b-polyethylene glycol-b-poly(L-lactide) (PLLA-PEG-PLLA) blended with poly(D-lactide)/poly(L-lactide) with m.w. of 6,000 g/mol (PDLA6k/PLLA6k). These blends were prepared by melt blending. PLLA-PEG-PLLA/PDLA6k/PLLA6k ratios of 90/10/0, 90/7.5/2.5, 90/5/5, 90/2.5/7.5 and 90/0/10 %wt. were investigated. PLLA-PEG-PLLA/PDLA6k and PLLA-PEG-PLLA/PLLA6k blends were also prepared for comparison. The presence of PDLA6k/PLLA6k mixture improved crystallization and heat resistance of PLLA-PEG-PLLA and this improvement was related to increased PDLA6k content. However, the 90/10/0 blend film was brittle but 90/7.5/2.5, 90/5/5, 90/2.5/7.5 and 90/0/10 blend films were not. The PLLA6k blending enhanced film flexibility. The results suggested that the PLLA-PEG-PLLA blends with controllable mechanical properties and heat resistance can be prepared by varying the PDLA6k/PLLA6k ratio for use as flexible and heat-resistant biodegradable bioplastics.

Enhanced Nonisothermal Crystallization and Heat Resistance of Poly(l-lactic acid) by d-Sorbitol as a Homogeneous Nucleating Agent

We report on enhancing crystallization and heat resistance of poly(l-lactic acid) (PLLA) by d-sorbitol as a small molecule nucleating agent via melt blending. During the reheating process, the cold crystallization disappeared and the crystallinity of nucleated PLLA exceeded 50%. The heat deflection temperature of PLLA was elevated from 56 to 132 °C by simply increasing the mold temperature (90 °C) without an additional annealing treatment. We also observed the polymorphic crystals of PLLA during melt crystallization, i.e., the coexistence of hexagonal and lenticular crystals, along with their various geometrical aggregates in addition to plenty of conventional spherulites. On the basis of the fact that the nonisothermal crystallization temperature of PLLA (110 °C at a cooling rate of 10 °C/min) was higher than the melting point of d-sorbitol (about 93 °C), we speculated that d-sorbitol promoted the crystallization of PLLA through a homogeneous nucleation mechanism.

Enhanced rheological properties and heat resistance of poly (propylene carbonate) composites with carbon fiber

Sustainable composites of poly (propylene carbonate) (PPC) and carbon fiber (CF) were prepared by melt mixing. Scanning electron microscopy observation revealed that when the CF content was less than 20 wt%, CF was uniformly dispersed in the PPC matrix. Incorporation of CF greatly improved the rheological properties of PPC/CF composites. Once the CF content was increased to 20 wt%, a percolation network structure composed of CF was formed, causing the composite to exhibit a solid-like behavior. Furthermore, CF could serve as an excellent reinforcing agent for PPC, characterizing that the storage modulus of the composite with 20 wt% CF was increased by 333% and 2367% at 20 °C and 50 °C, respectively. Finally, the addition of CF could increase the glass transition temperature and vicat softening temperature of PPC/CF composites, thereby improving their heat resistance.

Highly toughened and heat resistant poly(l-lactide)/poly(ε-caprolactone) blends via engineering balance between kinetics and thermodynamics of phasic morphology with stereocomplex crystallite

Enhancing matrix crystallization via forming stereocomplex (SC) crystallite has been considered as an effect way to improve the impact toughness and heat resistance of poly(l-lactide) (PLLA) when blending with other polymers. However, the roles of some of the key parameters, such as the kinetics of morphology evolution in blends, remain, yet, unclear, causing the troubles of the reproducibility of toughening PLLA by enhancing matrix crystallization and the stability in end-use applications (particularly in relative high temperature ranges). Herein, we provide a facile way to improve the toughness and heat resistance of PLLA via engineering the balance between the kinetics and thermodynamics of the dispersed phasic morphology in PLLA blends using PLLA/poly(ε-caprolactone) (PCL) (PLLA/PCL, 80/20 w/w) as an example, by adding a small amount of poly(d-lactide) (PDLA, ≤ 1% w/w). The few PDLA chains naturally interact with PLLA matrix chains, and co-crystallize to form SC crystallites, yielding high crystalline PPLA matrix but in controllable crystallization kinetics and increase of melting viscosity. As such, the coalescence or arrest of dispersed PCL phase is tailored via the tempo- and thermo-dimensional balance manipulation of thermal annealing (thermodynamics) and injecting moulding (quenching, dynamics), that relies on the PDLA content. The ease, with which highly impact toughened and heat-resistant PLLA materials were obtained by optimizing and matching the PDLA content and processing parameters including temperature and time, points to new directions in designing toughened PLLA with an economic manner.

A novel ultra low-k nanocomposites of benzoxazinyl modified polyhedral oligomeric silsesquioxane and cyanate ester

Benzoxazinyl modified polyhedral oligomeric silsesquioxane (BZPOSS) is successfully synthesized and used to prepare nanocomposites with bisphenol A cyanate ester (BADCy). The DSC results showed that the curing peak temperature of BZPOSS/BADCy blend decrease significantly from 317.1 °C to 160.3 °C, suggesting the high catalytic activity of BZPOSS to the polymerization of cyanate ester. The SEM micrographs of poly(BZPOSS/BADCy) and Silicon element distribution maps given by EDS both indicated that BZPOSS disperses evenly in BADCy. Dielectric properties tests showed that the dielectric constant can be reduced by the introduction of BZPOSS, which is attributed to the nano-pores from the cage structure of POSS. When 15 wt% BZPOSS was added, the dielectric constant decreased to 2.01 and the dielectric loss was also only 0.0070 at 1 MHz. Meanwhile, DMA and TGA result showed that the thermal stability and heat resistance of poly(BZPOSS/BADCy) at high temperature decreased with increasing BZPOSS, which is due to the change of crosslinking structure of the copolymers. The influences of the crosslinking structure and the nano-porous organic-inorganic hybrid particles on the dielectric and thermal property of poly(BZPOSS/BADCy) were also discussed.

Heat resistance of biobased materials, evaluation and effect of processing techniques and additives

The paper describes the effect of different manipulations (addition of fiber, nanoclay, nucleating agents and chain extender, blending, annealing, use of a higher mold temperature and stereocomplexation) on the heat resistance of poly(lactic acid) (PLA) and poly(hydroxybutyrate) (PHB). Therefore, the differential scanning calorimetry profiles, the vicat softening temperatures and the degradation temperatures were measured and compared to standard PLA, PHB, and polypropylene (PP) as reference materials. Furthermore, a comparison between VST and HDT as parameters for heat resistance was made by examining the deformation during contact with hot water. Stereocomplexation and the use of a higher mold temperature seemed the best techniques to obtain PLA‐based materials with good heat resistance, while other manipulations had little to no effect on the processed biopolymer. The addition of chain extender to PLA and PHB had no effect on processed polymers, but it did improve the thermal degradation of PLA during processing. Furthermore, hot fill tests showed that higher VST values were more reliable as a heat resistant parameter than HDT values for these kinds of application. The VST values of PHB were similar to PP, suggesting that PHB also provides opportunities as a packaging material for food products that undergo a heat treatment. POLYM. ENG. SCI., 58:513–520, 2018. © 2017 Society of Plastics Engineers

Surface Energy and Thermal Stability Studies of Poly(dimethyl siloxane)–Poly(alkyl(meth)acrylate) Copolymers

ABSTRACTThe correlation between the surface energy and thermal stability of polymers plays an important role in engineering of plastic materials. In this work, microstructural characteristics of copolymers of poly(dimethyl siloxane) with benzyl methacrylate, ethyl methacrylate, and methyl acrylate are correlated with their surface energy and thermal stability. The poly(dimethyl siloxane) segments in the copolymer chains affected the hydrophobic behavior. The surface energy of the synthesized copolymers decreased by increasing segments of alkyl methacrylates. The thermal stability of copolymers suggesting that heat resistance of poly(dimethyl siloxane) copolymers used in this correlation can be improved by adjusting the units of alkyl methacrylates in copolymers.

Remarkably Enhanced Impact Toughness and Heat Resistance of poly(l-Lactide)/Thermoplastic Polyurethane Blends by Constructing Stereocomplex Crystallites in the Matrix

As an eco-friendly polymer with tremendous potential to replace traditional petroleum-based and nonbiodegradable polymers, the current use of poly(l-lactide) (PLLA) in large-scale commercial applications still faces some barriers mostly associated with its inherent brittleness and poor heat resistance. In this work, we propose a novel and facile strategy to simultaneously address these obstacles by introducing small amounts of poly(d-lactide) (PDLA) into thermoplastic polyurethane (TPU) toughened PLLA blends through melt-blending. The results manifest that the introduced PDLA chains can readily interact with PLLA matrix chains and rapidly cocrystallize into stereocomplex (sc) crystallites capable of acting as an efficient rheology modifier to dramatically improve melt viscoelasticity of the PLLA matrix and subsequently induce the morphological change of the dispersed TPU phase from a typical sea–island structure to a unique networklike structure, thus endowing PLLA/TPU/PDLA blends with remarkably improved...

Effect of nucleating agents on the crystallization behavior and heat resistance of poly(l‐lactide)

ABSTRACTPoly (l‐lactide) (PLLA) blends with various nucleators were prepared by melt processing. The effect of different nucleators on the crystallization behavior and heat resistance as well as thermomechanical properties of PLLA was studied systematically by differential scanning calorimetry, X‐ray diffraction, heat deflection temperature tester, and dynamic mechanical analysis. It was found that poly(d‐lactide), talcum powder (Talc), a multiamide compound (TMC‐328, abbreviated as TMC) can significantly improve the crystallization rate and crystallinity of PLLA, thus improving thermal–resistant property. The heat deflection temperature of nucleated PLLA can be as high as 150°C. The storage modulus of nucleated PLLA is higher than that of PLLA at the temperature above Tg of PLLA. Compared with other nucleating agents, TMC was much more efficient at enhancing the crystallization of PLLA and the PLLA containing TMC showed the best heat resistance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42999.

Toughening of poly(l-lactide) with poly(ε-caprolactone): Combined effects of matrix crystallization and impact modifier particle size

Enhancing matrix crystallization has been demonstrated to be an effective method to simultaneously improve the impact toughness and heat resistance of poly(l-lactide) (PLLA) modified with flexible polymers, such as poly(ε-caprolactone) (PCL). Unfortunately, increasing PLLA matrix crystallinity alone cannot guarantee the enhancement of impact toughness in most cases, so other structural parameters should be considered. In this work, taking PLLA/PCL (80/20) blend as an example, the combined roles of matrix crystallization and impact modifier particle size in the toughening have been investigated. PLLA matrix crystallinity was controlled by adding a highly effective nucleating agent and PCL particle size was tailored by varying processing conditions while maintaining constant interfacial adhesion. It is interesting to find that toughening is efficient only if matrix crystallinity and particle size are well matched. With the significant increase of matrix crystallinity, an evident decrease of optimum particle size for toughening PLLA has been identified for the first time. Therefore, suitable particle size is the precondition for highly crystalline matrix to work effectively in the toughening because only small particles (0.3–0.5 μm) are effective in trigger shear yielding mechanism of the matrix needed for good toughness, whereas relatively large particles (0.7–1.1 μm) are only capable of toughening amorphous matrix effectively by initiating multiple crazing of the matrix. Importantly, our findings can be used to well explain the reason for the different roles of matrix crystallization in the toughening of different PLLA blends reported in the literature. Furthermore, the heat resistance of the blend with a highly crystalline matrix is much better than that of the blend with an amorphous one as expected. This work could not only provide a new insight into the synergistic roles of matrix crystallization and modifier particle size in the toughening of PLLA but also set up a universal framework for designing high-performance PLLA products with both good impact toughness and high heat resistance.

Improvement in toughness and heat resistance of poly(lactic acid)/polycarbonate blend through twin‐screw blending: Influence of compatibilizer type

AbstractThe thermal mechanical properties and morphological changes of modified poly(lactic acid) (PLA) and polycarbonate (PC) polymer blends based on the equal weight fraction of each component were investigated. Several blend samples were prepared by melt processing with a twin screw extruder using both poly(butylene succinate‐co‐lactate) (PBSL) and epoxy (EP) as compatibilizers for the PLA/PC binary system. Differential scanning calorimetry (DSC) of PLA/PBSL and PC/PBSL binary blends showed that individual components were immiscible. Scanning electron microscopy (SEM) analysis of these blends revealed the domain size of PBSL was ∼ 0.5–1 μm in PLA/PBSL blend, and reduced to around 0.1 μm in PC/PBSL blend. The notched Izod impact strength (IS) of PLA/PC/PBSL ternary blends increased with PBSL content up to 10 phr PBSL due to enhanced interfacial interaction and proper domain size of the dispersed phase on the basis of DMA, DSC, and SEM analysis. The heat deflection temperature (HDT) showed a maximum at 5 phr PBSL, and it dropped with increasing PBSL content which is a ductile polymer. However, the HDT of PLA/PC/EP ternary blends increased considerably with 10 phr EP due to rigid interphase formation, and it increased further with 1 phr quaternary amine catalyst, however, the IS dropped nearly the same as that of unmodified PLA/PC blend. To take advantage of the two compatibilizers, PBSL and EP were added to the PLA/PC blend at 10 phr each plus 1 phr catalyst and both IS and HDT were improved significantly over unmodified PLA/PC pair. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Crosslinkable poly(vinyl acetate) emulsions for wood adhesive

PurposeThe purpose of this paper is to enhance the water resistance and the heat resistance of poly(vinyl acetate) (PVAc) emulsion adhesive, by providing the emulsion with controllable thermosetting capability.Design/methodology/approachEmulsion polymerisation was used to synthesise PVAc/VeoVa 10 copolymers with varying proportions of acetoacetoxyethyl methacrylate (AAEM) incorporated in the copolymer chains. The AAEM component provided sites for crosslinking the chains via reaction of diamines with AAEM. The emulsion copolymers formed crosslinked films on addition of a range of diamines, during drying at ambient temperature. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterise the copolymerisation and crosslinking reaction. Glass transition temperatures of the polymer films were measured using dynamic mechanical thermal analysis to quantify the effects of copolymer composition variation and crosslinker. The performance of the crosslinked emulsions as wood adhesives was evaluated in accordance with the ISO 6238 standard by measuring the maximum shear stress of wood joints.FindingsThe crosslinking reaction between acetoacetoxy groups in the copolymer chains and the added diamines gives enamine structures, and occurs rapidly at ambient temperature. Major changes in the 13C NMR spectrum include the appearance of an enamine signal at 82 ppm, and disappearance of the acetoacetoxy carbonyl signal at 202 ppm. The new vibrational band at 1,597‐1,606 cm−1 in the FTIR spectrum is assigned to the vibrations of the enamine double bond. The experimental results showed substantial increases in Tg and viscosity as the AAEM proportion in the copolymer emulsion increased. The crosslinked adhesives showed superior wood adhesive performance to unmodified PVAc emulsion.Research limitations/implicationsIt was necessary to adjust the pH of the emulsion for extended shelf life.Practical implicationsThe method developed provides a simple and practical route to emulsions with improved water and heat resistance and bonding strength.Originality/valueThe method for enhanced water and heat resistance of PVAc wood adhesive was novel, straightforward and environmental friendly.

Upper critical solution temperature type phase behavior of poly(styrene-co-acrylonitrile) blends with poly(styrene-co-n-phenyl maleimide) and their interaction energies

To enhance the heat resistance of poly(styrene-co-acrylonitrile-co-butadiene), ABS, miscibility of poly(styrene-co-acrylonitrile), SAN, with poly(styrene-co-n-phenyl maleimide), SNPMI, having a higher glass transition temperature than SAN was explored. SAN/SNPMI blends casted from solvent were immiscible regardless of copolymer compositions. However, SNPMI copolymer forms homogeneous mixtures with SAN copolymer within specific ranges of copolymer composition upon heating caused by upper critical solution temperature, UCST, type phase behavior. Since immiscibility of solvent casting samples can be driven by solvent effects even though SAN/SNPMI blends are miscible, UCST-type phase behavior was confirmed by exploring phase reversibility. When copolymer composition of SNPMI was fixed, the phase homogenization temperature of SAN/SNPMI blends was increased as AN content in SAN copolymer increased. To understand the observed phase behavior of SAN/ SNPMI blend, interaction energies of blends were calculated from the UCST-type phase boundaries by using the lattice-fluid theory combined with a binary interaction model.

Mechanical serviceability and heat resistance of polymers

The research of the authors and coworkers on the serviceability and heat resistance of polymersis reviewed. The effect of the chemical and supermolecular structures on the heat resistance of poly (hetero-arylenes) is demonstrated with reference to numerous examples; methods of estimating the glass-transition and melting points, density, and volume expansion coefficients of polymers on the basis of the structural formula of the repeating unit are described.