聚苯醚/聚苯乙烯/纳米二氧化硅复合材料的制备及其结构与性能

通过熔融共混法制备了聚苯醚(PPE)/聚苯乙烯(PS)/纳米二氧化硅(SiO2)复合材料,并采用透射电子显微镜、扫描电子显微镜、力学性能测试及Hakke流变仪等研究了复合材料的结构与性能。结果表明,纳米SiO2均匀分散在PPE/PS基体中,粒径随着SiO2含量的增加而增大;随着纳米SiO2含量的增加,复合材料的拉伸强度、断裂伸长率和缺口冲击强度呈现先增大后降低的趋势,弯曲强度和玻璃化转变温度逐渐增大,蠕变量则逐渐降低。     

Microstructural Development of Uniaxial Stretched Anneal-Oriented Syndiotactic Polystyrene and its Blend with Poly (2,6-dimethyl-1,4-phenylene oxide): DSC,WAXD, SAXS and FTIR Studies

Studies have been done on strain-induced microstructure development in syndiotactic polystyrene (s-PS) and its blends with poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) in 70/30 and 50/50 compositions of stretched annealed samples. Wide-angle X-ray showed that crystal orientation is less in annealed blend samples compared to annealed pure s-PS for a higher draw ratio. It increases with annealing, and relaxation occurs after a certain annealing temperature at above 180° for both s-PS and s-PS/PPO 70/30 blends. No crystal orientation was observed in the blend of s-PS/PPO 50/50 stretched samples. Small angle X-ray scattering (SAXS) shows the inclusion of amorphous PPO chains in between s-PS crystals lamella. Fourier transform infrared (FTIR) spectroscopy shows that the s-PS molecular chain packing band at 905 cm^?1 is enhanced due to annealing in oriented samples and saturates to around 0.63. The crystal chain relaxation is lower than amorphous chains of s-PS. The molecular chains of amorphous PPO are less oriented into the blend matrix, whereas its relaxation is enhanced during heat treatment and reaches an optimum value after full relaxation. The different behaviors of orientation and relaxation of s-PS and PPO chains into the blend matrix produce superstructures.     

Thermal,mechanical, and morphological characterization studies of poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends with polystyrene and brominated polystyrene

The miscibility of the binary and ternary blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide), brominated polystyrene, and polystyrene was investigated using a differential scanning calorimeter. The morphology of these blends was characterized by scanning electron microscopy. These studies revealed a close relation between the blend structure and its mechanical properties. The compatibilizing effect of poly(2,6‐dimethyl‐1,4‐phenylene oxide) on the miscibility of the polystyrene/brominated polystyrene blends was examined. It was found that poly(2,6‐dimethyl‐1,4‐phenylene oxide), which was miscible with polystyrene and partially miscible with brominated polystyrene, compatibilizes these two immiscible polymers if its contention exceeds 33 wt %. Upon the addition of poly(2,6‐dimethyl‐1,4‐phenylene oxide) to the immiscible blends of polystyrene/brominated polystyrene, we observed a change in the morphology of the mixtures. An improvement in the mechanical properties was noticed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 225–231, 2000     

Effect of crystallization conditions on spherulitic texture and tensile properties of sPS/PPO blends

In the second study on melt‐miscible syndiotactic polystyrene (sPS) and poly(phenylene oxide) (PPO) blends, the effect of processing conditions on morphology, ultimate tensile properties, and the mode of fracture is reported. Bulk samples of the blends were molded and then crystallized from melt as well as from the quenched state at different temperatures. The spherulitic morphology of the melt‐crystallized blends, observed by scanning electron microscopy, revealed formation of complete, well‐developed spherulites whose texture increased in coarseness with increasing crystallization temperatures. In all the cold‐crystallized blends lamellar bundles formed a meshlike structure whose texture did not vary significantly with crystallization temperature. Depending on the crystallization temperature, 50/50 melt‐crystallized blends showed varying tensile properties and different modes of failure. In the samples with the largest amorphous domain size of 0.6 μm, the amorphous ellipsoids were cold drawn into fibrils during tensile loading and very high tensile strengths were recorded. The tensile properties for the other melt‐crystallized and all cold‐crystallized blends did not vary substantially with the changing crystallization temperature. The micrographs of the fractured surfaces of the melt‐crystallized blends suggested that, although intraspherulitic fracture occurred at low crystallization temperatures, interspherulitic fracture took place at high crystallization temperatures. The correlation of the morphology and mechanical properties suggests that melt‐miscible blends have good interfacial adhesion between phases and that, by varying composition and processing conditions, it might be possible to control amorphous domain sizes, which is critical in achieving better mechanical properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1984–1994, 2003     

Effect of the crystallization conditions on the phase behavior of syndiotactic polystyrene/poly(phenylene oxide) blends

Syndiotactic polystyrene (sPS) and poly(phenylene oxide) (PPO) blends, miscible in the melt state, were crystallized from the melt and the quenched state at different temperatures. The effect of the crystallization temperature on the phase behavior of the blends and the polymorphic changes in sPS was investigated by dynamic mechanical analysis (DMA), wide‐angle X‐ray diffraction (WAXD), and density measurements. In most blends, the crystallization of sPS induced segregation into two homogeneous amorphous phases of different compositions. The temperatures of the DMA relaxations of the neat homopolymers and crystallized blends were fit by the Gordon–Taylor relation to calculate the compositions of these phases. In melt‐crystallized blends, with slower crystallization, the major amorphous phase became sPS‐rich, whereas the minor phase became PPO‐rich. These major and minor amorphous phases could be tentatively assigned to interfibrillar and interlamellar regions, respectively. In cold‐crystallized blends, slower crystallization decreased the sPS concentration in both phases, and the scale of segregation was much smaller. WAXD studies and density measurements indicated a complex polymorphic behavior of sPS after it was blended with PPO. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1975–1983, 2003     

Phase diagrams of blends of poly(phenylene ether), polystyrene,and diglycidyl ether of bisphenol A: Influence of the molar mass of poly(phenylene ether)

Phase diagrams of ternary blends of poly(phenylene ether) (PPE, M_n = 1.2 and 12 kg mol^?1), polystyrene (PS, M_n = 22.5 kg mol^?1), and diglycidyl ether of bisphenol A (DGEBA) were experimentally obtained in an extended range of temperatures and fitted with the Flory–Huggins model using three binary interaction parameters. A significant increase in miscibility together with the appearance of an immiscibility loop was found for PPEs with M_n values comprised in the range between 1 and 10 kg mol^?1. This enables us to obtain initial homogeneous solutions in regions of high DGEBA concentrations, a possibility that was not previously reported for this ternary blend. This opens new possibilities for the toughening of epoxies replacing a single thermoplastic with a thermoplastic blend where both components (PS and PPE) are completely miscible. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1742–1747, 2006     

Influence of composition and molecular mass on the morphology,crystallization and melting behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends

Results are reported on the influence of composition and molecular mass of components on the isothermal growth rate of spherulites, on the overall kinetic rate constant, on the primary nucleation and on the thermal behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends. The growth rate of PEO spherulites as well as the observed equilibrium melting temperatures decrease, for a given T_c or ΔT, with the increase of PMMA content.Such observations are interpreted by assuming that the polymers are compatible in the undercooled melt, at least in the range of crystallization temperatures investigated. Thermodynamic quantities such as the surface free energy of folding σ_e and the Flory-Huggins parameter χ₁₂ have been obtained by studying the dependence of the radial growth rate G and of the overall kinetic rate constant K from temperature and composition and the dependence of the equilibrium melting temperature depression ΔT_m upon composition, respectively.     

Dielectric,mechanical and thermal properties of some chlorinated poly (p-phenylene oxide)s in the solid state

The dielectric, mechanical and thermal properties were investigated for poly(2,6-dichloro-1,4-phenylene oxide) (PDCPO), poly(2-chloro-6-methyl-1,4-phenylene oxide) (PCMPO) and poly(2,6-dimethyl-1,4-phenylene oxide) (PDMPO). PDCPO exhibited two dielectric secondary relaxations designated as β and γ processes around 160 and 100K, respectively. The γ process was assigned to the motion of a trace of chloroform included in the PDCPO film. A blend film PDMPO/PCMPO ($\text{9}\text{1}$ mixing ratio) exhibited dielectric relaxation around 330K and the process was assigned to the rotation of phenyl group with respect to oxygen-phenyl-oxygen axis. No dielectric relaxation was observed for the PDMPO film dried carefully, while the PDMPO film kept under an atmosphere of water vapour exhibited dielectric relaxation due to the motion of the water molecules at about 180K. Tensile stress at break measured on PDCPO prepared by Stamatoff's method was 38 MPa and was much higher than that for PDCPO prepared by the method reported by Blanchard et al. Temperature dependence of the dynamic Young's modulus for PDCPO measured at 110 Hz exhibited no appreciable loss peak in the range below 480K. Glass transition temperatures for PDCPO, PCMPO and PDMPO were determined to be 490, 445 and 500K, respectively, by differential scanning calorimetry.     

Studies on the phase structure,mechanical, rheological properties,and nonisothermal crystallization kinetics of the PEN/SCF composites

Short carbon fiber reinforced poly(ethylene 2,6‐naphthalate) composites (PEN/SCF) were prepared by twin‐screw extruder. The structure, mechanical, rheological properties, and nonisothermal crystallization kinetics of the composites were investigated by scanning electron microscope, universal tester, and differential scanning calorimetry. The results suggest that there is better interaction between SCF and PEN matrix, which leads to an increase in the tensile strength, Young's modulus, and impact strength of the composites with proper contents of SCF. Rheological behavior of the PEN/SCF composites melt is complicated, combining a dilate fluid at lower shear rate and a pseudoplastic fluid at higher shear rate. Moreover, the flow activation energy of the composites suggests that the melt with more SCF has higher sensitivity to the processing temperature. In conclusion, the composite with 5–10 wt % content of SCF has better properties. The Avrami equation modified by Jeziorny and Ozawa theory was used, respectively, to fit the primary stage of nonisothermal crystallization of various composites. The Avrami exponents n are evaluated to be 2.6–3.1 for the neat PEN and 3.4–4.8 for PEN/SCF composites, and the SCF served as nucleation agent accelerates the crystallization rate of the composites, and more the content of SCF faster the crystallization rate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Self‐condensing atom transfer radical polymerization of inimers of different reactivity ratios with styrene and the thermal properties of poly(2,6‐dimethyl‐1, 4‐phenylene oxide)/branched polystyrene blends

Although the self‐condensing atom transfer radical polymerization (SCATRP) of inimers with typical comonomers has been extensively performed, there have been few reports to correlate the reactivity ratio with the growth of the molecular weights (MWs) and the development of branched structures. Thus, the SCATRP of inimers of different reactivity ratios, namely, 4‐chloromethylstyrene (CMS) and maleimide (MI) inimers, with a large excess of styrene (St) were carried out, respectively, to examine the effect. The conversion and MW were monitored by gas chromatography, gel permeation chromatography, and multiangle laser light scattering. The results suggested that CMS merely functioned as an initiator for St at the early stage; this led to linear macroinimers, which underwent SCATRP and gave rise to randomly branched polystyrene (PS) only at high conversion. The MI inimers formed charge‐transfer complexes with St and underwent the SCATRP to result in hyperbranched copolymers at first; this initiated the atom transfer radical polymerization of St and led to star‐shaped PS. With the objective of improving the processability and melt fluidity, the physical properties of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) blends with linear, randomly branched, and star‐shaped PS were compared. In comparison with those with linear PS, the PPO/branched PS blends exhibited a higher glass‐transition temperature, a higher melt flow index, and a comparable thermal stability because of the spherical architecture of the branched PS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Studies on the transesterification of polycarbonate/poly(ethylene terephthalate) blends. II: Effect of transesterification on the compatibility and crystallization behaviour of the blends

The effect of transesterification on the compatibility of polycarbonate poly(ethylene terephthalate) (PC/PET) blends and the crystallization and melting behaviour of PET was studied. The results show that with increase of the reaction extent, the compatibility of the blends was enhanced during melt-processing, from completely incompatible to partially compatible, then to complete compatibility. In addition, with the increase of reaction extent, the crystallization ability and crystallinity of PET decreased. A new endotherm peak was discerned in DSC thermograms and its position and peak area were closely related to the reaction conditions, which was explained by the changes in the crystalline regions in the PC/PET blends. The effect of transesterification on the multiple melting behaviour of PET in PC/PET blends is also discussed.     

Poly (ethylene oxide) (PEO) influence on mechanical,thermal, and degradation properties of PLA/PBSeT blends

Poly (lactic acid) (PLA) is an important biodegradable plastic with unique properties. However, its widespread application is hindered by its low miscibility and suboptimal degradation properties. To overcome these limitations, we investigated the mechanical, thermal, and degradation properties of PLA and poly (butylene sebacate-co-terephthalate) (PBSeT) blends in the presence of poly (ethylene oxide) (PEO). Specifically, this study aimed to identify the effects of PEO as a compatibilizer and hydrolysis accelerator in PLA/PBSeT blends. PLA (80%) and PBSeT (20%) were melt blended with various PEO contents (2–10 phr), and their mechanical, thermal, and hydrolytic properties were analyzed. All PEO-treated blends exhibited a higher elongation at break than that of the control sample, and the tensile strength was slightly reduced. In the PEO 10% sample, the elongation at break increased to 800% of that of the control sample. Differential scanning chromatography (DSC) analysis confirmed that when PEO was added to the PLA/PBSeT blends, the two glass transition temperatures (T_g) narrowed, resulting in improved miscibility of PLA and PBSeT. In addition, the hydrolytic degradation of the PLA/PBSeT/PEO blend accelerated as the PEO content increased. It was confirmed that PEO can act as a compatibilizer and hydrolysis-accelerating agent for PLA/PBSeT blends.     

Crystal structure and morphology influenced by shear effect of poly(l-lactide) and its melting behavior revealed by WAXD, DSC and in-situ POM

Shear effect on crystal structure, morphology and melting behavior of poly(l-lactide) (PLLA) were investigated by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and in-situ polarized optical microscope (POM). Influences of steady shear on PLLA melt was investigated during annealing. The impacts of crystallization temperature (T_c) and shear rate (SR) on crystal structure, crystal growth rate, nucleation, and melting behavior were studied. It could be clarified into the low (<20 s⁻¹) and high shear rate ranges in terms of the crystal structure, growth rate, nucleation and melting behavior. It was found that phase transition and recrystallization during heating completely changed the stack structure. A new stable structure was established after a temperature jump in the melting range. Cylindric morphology arranged with spherulite was also observed in the polymer films at high T_c influenced by shear effect.     

The effect of lanthanum oxide (La2O3) on the structure and crystallization of poly(vinylidene fluoride)

Rare earth polymers, due to their excellent luminescence, fluorescence, laser protective, optical and magnetic properties, have attracted much research attention in recent years. However, little attention has been paid to the effect of rare earths on the structure and crystallization of polymers, which is of important significance in the development of functional polymers. X‐ray diffraction and differential scanning calorimetry were used to investigate the structure and crystallization behavior of a poly(vinylidene fluoride) (PVDF)/lanthanum oxide (La₂O₃) composite. The results showed that the degree of perfection, crystal size, crystallization rate and isothermal crystallization activation energy of PVDF in the composite decreased, compared with pure PVDF. The spherulite nucleation and growth for PVDF and PVDF composite were analyzed in detail using the Lauritzen‐Hoffman equation. The modified Avrami equation and the Mo equation were used to study the non‐isothermal crystallization kinetics. The addition of La₂O₃ did not change the crystal structure and nucleation process for PVDF, but it decreased markedly the crystal growth rate and led to the formation of unstable crystals. This was attributed to the fact that too much La₂O₃ prevented PVDF molecular chains from moving and arranging in an orderly manner into crystals. Copyright © 2010 Society of Chemical Industry     

热定型对嵌段聚醚酯弹性纤维结构与性能的影响

研究了热定型时间、温度和方式对嵌段聚醚酯弹性纤维的结构和性能的影响 ,采用 DSC、X-射线衍射测定了纤维热定型前后结晶结构及结晶度的变化 ,同时测定了纤维的断裂强度、断裂伸长、回弹率和热水收缩率的变化 ,结果表明 ,热定型处理使嵌段聚醚酯纤维的结晶结构发生了变化并使结晶度提高 ,从而提高了纤维的回弹性能和力学性能 ,纤维的热水收缩率与氨纶相当     

Studies on the transesterification of polycarbonate/poly(ethylene terephthalate) blends. I: Mechanisms and extent of reaction

Transesterification of polycarbonate/poly(ethylene-terephthalate) (PC/PET) blends and the reaction extent were investigated by DSC, FTIR, ¹H NMR and Soxhlet extraction. A new characteristic peak appeared in the FTIR spectrum of PC/PET blends after heat treatment, which indicates that new copolymers were formed in the transesterification of the PC/PET blends. The reaction extent was characterized by the absorbance ratios of the FTIR characteristic bands. The reaction extent was associated not only with the reaction conditions but also with the composition of the blends. These results were confirmed by chemical analysis of the extracted products in CH₂Cl₂ solvent and FTIR analysis. For all the blends studied, the blend with 50/50 wt% had the highest reaction extent. The reaction mechanisms and extent were also confirmed by ¹H NMR analysis.     

Part 7. Effects of poly(L‐lactide‐co‐ϵ‐caprolactone) on morphology,structure, crystallization,and physical properties of blends of poly(L‐lactide) and poly(ϵ‐caprolactone)

Blended films of poly(L ‐lactide) [ie poly(L ‐lactic acid)] (PLLA) and poly(?‐caprolactone) (PCL) without or mixed with 10 wt% poly(L ‐lactide‐co‐?‐caprolactone) (PLLA‐CL) were prepared by solution‐casting. The effects of PLLA‐CL on the morphology, phase structure, crystallization, and mechanical properties of films have been investigated using polarization optical microscopy, scanning electron microscopy, differential scanning calorimetry and tensile testing. Addition of PLLA‐CL decreased number densities of spherulites in PLLA and PCL films, and improved the observability of spherulites and the smoothness of cross‐section of the PLLA/PCL blend film. The melting temperatures (T_m) of PLLA and PCL in the films remained unchanged upon addition of PLLA‐CL, while the crystallinities of PLLA and PCL increased at PLLA contents [X_PLLA = weight of PLLA/(weight of PLLA and PCL)] of 0.4–0.7 and at most of the X_PLLA values, respectively. The addition of PLLA‐CL improved the tensile strength and the Young modulus of the films at X_PLLA of 0.5–0.8 and of 0–0.1 and 0.5–0.8, respectively, and the elongation at break of the films at all the X_PLLA values. These findings strongly suggest that PLLA‐CL was miscible with PLLA and PCL, and that the dissolved PLLA‐CL in PLLA‐rich and PCL‐rich phases increased the compatibility between these two phases. © 2003 Society of Chemical Industry     

A review on the mechanical and electrical properties of graphite and modified graphite reinforced polymer composites

Carbon materials particularly in the form of sparkling diamonds have held mankind spellbound for centuries, and in its other forms, like coal and coke continue to serve mankind as a fuel material, like carbon black, carbon fibers, carbon nanofibers and carbon nanotubes meet requirements of reinforcing filler in several applications. All these various forms of carbon are possible because of the element's unique hybridization ability. Graphene (a single two-dimensional layer of carbon atoms bonded together in the hexagonal graphite lattice), the basic building block of graphite, is at the epicenter of present-day materials research because of its high values of Young's modulus, fracture strength, thermal conductivity, specific surface area and fascinating transport phenomena leading to its use in multifarious applications like energy storage materials, liquid crystal devices, mechanical resonators and polymer composites. In this review, we focus on graphite and describe its various modifications for use as modified fillers in polymer matrices for creating polymer-carbon nanocomposites.