Quantitative thermal analysis of polyblends

A new quantitative thermal analysis technique was attempted on ABS and Noryl-type polyblends. A particular component within a polyblend was identified by its glass transition temperature and the amount of the component was determined from the increase in specific heat at the glass transition temperature. Two commercial Noryl resins were determined to be blends of high impact polystyrene and polyphenylene oxide in 47-47 and 69-17 proportions by weight, respectively. Polystyrene appears to be cosoluble with polyphenylene oxide without the formation of any complex. The PS-PPO polyblends yield single sharp glass transitions which are a function of concentration.     

Vibration welding of thermoplastics. Part IV: Strengths of poly(butylene terephthalate), polyetherimide,and modified polyphenylene oxide butt welds

In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time or weld penetration.; The effects of these parameters on weld quality were systematically studied by first butt welding thermoplastic specimens under controlled conditions, over a wide range of process parameters, and by then determining the strengths and ductilities of these welds by tensile tests. The three thermoplastics investigated are poly (butylene terephthalate), polyetherimide, and modified polyphenylene oxide. Changes in the weld pressure are shown to have opposite effects on the strengths of polyetherimide and modified polyphenylene oxide welds; Also, the weld frequency is shown to have a significant effect on the weldability of polyetherimide. The weldability data for these three thermoplastics are compared with data for polycarbonate. Under the right conditions, the strengths of butt welds in these materials are shown to equal the strength of the virgin polymer.     

核壳结构微纳橡胶粒子的可控合成及对PPO/PS共混体系的增韧

采用乳液聚合方法在粒径为100 nm的聚丁二烯(PB)胶乳上接枝聚合苯乙烯(St),合成了核壳比为70/30(PB/PS)的PB-g-PS接枝共聚物,将其与聚苯醚(PPO)、聚苯乙烯(PS)树脂熔融共混,制备出一系列橡胶含量、基体组成不同的PPO/PS/PB-g-PS共混物,并考察了共混物的相容性、力学性能及形态结构。结果发现:PPO与PS为完全相容体系,且PB-g-PS在PPO/PS基体中的均匀分散程度随体系中PPO引入量的增大而明显改善,共混物的冲击强度及屈服强度也随之逐渐增大,进而促使共混物发生脆-韧转变所需的橡胶含量逐渐降低;随着共混体系中橡胶含量的增加,共混物的冲击强度逐渐提高,而屈服强度却逐渐降低,共混物的韧性断裂特征越发显著。     

改性塑料在汽车行业中的发展状况

结合改性塑料的应用前景及汽车工业“以塑代钢”、“以轻代重”的发展趋势,综述了聚丙烯(PP)、尼龙(PA)、聚碳酸酯(PC)、聚苯醚(PPO)、聚甲醛(POM)五类材料改性的最新研究成果及其在汽车零部件上的最新应用情况,探讨了改性塑料行业的技术发展趋势和行业应用趋势.     

复配增容剂增容PPO/PP/GF研究

研究复配增容剂(SEPS/PP-g-MAH)对玻璃纤维(GF)增强聚苯醚(PPO)/聚丙烯(PP)力学性能、熔体流动性以及耐热性能的影响,并用扫描电子显微镜观察了不同共混体系的形态结构.结果表明,复配增容剂改善了PPO/PP/GF共混体系的相容性,提高了共混体系的拉伸强度、弯曲强度、冲击强度和熔体流动速率,但同时降低了...     

Mechanical,Thermal, and Flame-Retardant Behaviors of Thermoplastic Polyether–Ester Elastomer Composites with Polyphenylene Oxide and Aluminum Hypophosphite

The thermoplastic polyether–ester elastomer and polyphenylene oxide composite was prepared by the reactive extrusion method using 4,4′-methylene diphenyl diisocyanate as a chain extender, and then aluminum hypophosphite was added to further flame-retardant thermoplastic polyether–ester elastomer/polyphenylene oxide composite. The results show that 4,4′-methylene diphenyl diisocyanate can improve the compatibility of thermoplastic polyether–ester elastomer and polyphenylene oxide and strengthen the mechanical properties of thermoplastic polyether–ester elastomer/polyphenylene oxide composite. The addition of aluminum hypophosphite increases the storage modulus of the thermoplastic polyether–ester elastomer composites at the low-temperature region and significantly decreases the heat release rate of thermoplastic polyether–ester elastomer and thus improves its flame retardancy.     

Polyphenylene ethers and their alloys

Poly(phenylene ether)s (PPE) are a class of polymers which contain phenolic monomers attached via an ether linkage. Depending upon the monomer types used in the polymerization, a variety of homopolymers and copolymers can be produced. When compounded with polystyrene, these poly(phenylene ether)s combine to form single phase alloys in contrast to the separate phases obtained with most other polymer blends. Since polyphenylene ether and polystyrene are completely miscible, the alloy also has only one glass transition temperature (T_g) and behaves in a manner that is typical of single polymeric materials. By blending poly(phenylene ether)s with impact modified polystyrene at different ratios, opaque thermoplastic resins having a wide range of chemical, thermal, and mechanical properties can be manufactured. Commercially available material grades have thus been developed to meet special product requirements for flame retardancy, high impact, increased flexural and tensile strength, low creep, and good resistance to certain chemical environments. In comparison to other types of unfilled thermoplastics, poly(phenylene ether)s have a balance of properties which can overlap those of acrylonitrile-butadiene-styrene (ABS), polycarbonate, nylon, and other high performance polymers.     

Cure behavior,morphology, and mechanical properties of the melt blends of epoxy with polyphenylene oxide

Cure behavior, miscibility, and phase separation have been studied in blends of polyphenylene oxide (PPO) with diglycidyl ether of bisphenol A (DGEBA) resin and cyanate ester hardener. An autocatalytic mechanism was observed for the epoxy/PPO blends and the neat epoxy. It was also found that the epoxy/PPO blends react faster than the neat epoxy. During cure, the epoxy resin is polymerized, and the reaction‐induced phase separation is accompanied by phase inversion upon the concentration of PPO greater than 50 phr. The dynamic mechanical measurements indicate that the two‐phase character and partial mixing existed in all the mixtures. However, the two‐phase particulate morphology was not uniform especially at a low PPO content. In order to improve the uniformity and miscibility, triallylisocyanurate (TAIC) was evaluated as an in situ compatibilizer for epoxy/PPO blends. TAIC is miscible in epoxy, and the PPO chains are bound to TAIC network. SEM observations show that adding TAIC improves the miscibility and solvent resistance of the epoxy/PPO blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 26–34, 2000     

Preparation of high performance adhesives matrix based on epoxy resin modified by bis-hydroxy terminated polyphenylene oxide

A bis-hydroxy terminated polyphenylene oxide (MPPO) modification was tried for the purpose of simultaneously enhancing the processability and heat resistance of epoxy resin. The thermal stability, chemorheology, morphology and mechanical properties of epoxy-polyphenylene oxide blends were investigated, respectively. The structure of MPPO was characterized by nuclear magnetic resonance and fourier transform infrared spectroscopy which indicated that MPPO was successfully synthesized. Epoxy-polyphenylene oxide blends exhibited a wide range of processing temperature mainly owing to the existence of bis-hydroxy in MPPO. Mechanical properties results revealed that the impact strength, tensile strength and elongation at break of MPPO/EP systems were performed satisfactorily. Scanning electron microscopy studies revealed the two-phase morphology and modification mechanism of the epoxy-polyphenylene oxide. Dynamic mechanical analysis and thermal gravimetric analyzer results showed that the introduction of MPPO leading to an enhancement to the thermal stability of epoxy matrix. Therefore, epoxy-polyphenylene oxide blends meet the requirements for the prepreg and high performance adhesives matrix.     

Polyamide,polyester und polyoxymethylen. Die klassischen technischen kunststoffe und ihre perspektiven

Polyamide, polyester and polyoxymethylene having presently a worldwide sales volume of 2,4 million tons a year are important engineering thermoplastics. Based on their special property profiles they are mainly used in the automotive and electronic industry for high performance functional parts. This contribution presents polymerisation processes, properties, and selected new developments for these polymer classes. Semiaromatic polyamides due to their dimensional stability and thermal resistance lend themselves to applications which were so far reserved for thermosets or metals. Glass fiber reinforce polyamides designed to have the highest possible heat ageing resistance can take important functions under the hood. A polyamide blend used as a material for exterior body parts is key to light weight cars with strongly reduced fuel consumption. Halogene free flame retardant polyamide increases fire safety and environmental safety in flame sensitive applications. Polybutyleneterephthalate as the technically most important polyester offers new perspectives in blends with amorphous polymers leading to lower distortion and better surface quality in glass fiber reinforced parts. Polybutylenenaphthalate is widening the range of application of polyesters towards higher temperatures. Copolyesters derived from polybutyleneterephthalate are biologically degradable and are therefore promising materials for fermentable foils. Polyoxymethylene copolymers show an outstanding combination of stiffness, dimensional stability, friction and wear as well as resistance against hot water and fuel. As a result of their excellent properties and the existing potential for further improvements polyamide, polyester and polyoxymethylene will continue to grow above average in the future.     

顺丁橡胶对硅橡胶/丙烯酸酯橡胶并用胶的增容作用

采用偏光显微镜、差示扫描量热仪以及力学性能、热老化性能测试手段,研究了顺丁橡胶(BR)增容的甲基乙烯基硅橡胶(MVQ)/丙烯酸酯橡胶(ACM)共混体系的并用比(质量比)、硫化工艺参数以及BR的加入对并用胶力学性能、耐热老化性能和相容性的影响。结果表明,BR的加入改善了MVQ/ACM并用胶的力学性能和耐热老化性能,当白炭黑用量为30份、BR/MVQ/ACM的并用比为25/45/55时,并用胶的力学性能和耐热老化性能最好;最佳硫化工艺参数为70℃×10 MPa×30 min;加入BR可以改善MVQ/ACM并用胶的相容性,且使其玻璃化转变温度降低,耐低温性能提高。     

Flame retardant performance of a modified aluminum trihydroxide with increased thermal stability

A modified form of aluminum trihydroxide has been synthesized that is thermally stable to approximately 350°C. Flame retardant and smoke generation performance in low melting temperature thermoplastics, such as polyvinyl chloride, polypropylene, and ethylene vinylacetate, are comparable to unmodified ATH. The increased thermal stability also allows this material to be used in thermoplastics with higher melting temperatures, such as polycarbonate, polybutylene terephthalate, and polyphenylene oxide, where ATH cannot be used.     

Cure reaction and phase separation behavior of cyanate ester‐cured epoxy/polyphenylene oxide blends

The cure reaction and phase separation mechanism of a cyanate ester‐cured epoxy and its blends with polyphenylene oxide (PPO) were studied. An autocatalytic mechanism was observed for the epoxy and its blends. The reaction rate of the blends was higher than that of the neat epoxy at initial stage; however, the reached conversion decreased with PPO content. FTIR analysis revealed that the cyanate functional group reactions were accelerated by adding PPO and indicated that several coreactions have occurred. This was caused by the reaction of cyanate ester with the PPO reactive chain ends. But at a later stage of cure, the reaction could not progress further due to diffusional limitation of PPO. To understand the relationship between the cure kinetics and phase separation of the blends, the morphology of the blends during cure was examined. When the homogeneous epoxy/PPO blends with low PPO content (10 phr) were cured isothermally, the blends were separated by nucleation and growth (NG) mechanism to form the PPO particle structure. But at high PPO content (30 phr), the phase separation took place via spinodal decomposition (SD). SD is favored near critical concentration and high cure rate system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1139–1145, 2006     

碳纤维增强热塑性复合材料工艺与性能的研究

短切碳纤维的ＢＵＳＳ捏合机和连续碳纤维的双螺杆挤出增强工艺开发了碳纤维增强聚酰胺,碳纤维增强聚甲醛,等碳纤维增强热塑性工程塑料,并以碳纤维增强聚酰胺为例进行成型工艺的研究,探讨了加 工工艺参数与材料性能的关系。     

Photo-oxidation mechanisms of poly(2,6-dimethyl-1,4-phenylene oxide).

A re-examination of the photo-oxidation mechanism of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) at both long and short irradiation wavelengths under accelerated conditions is reported. The formation rate of poly-2,6-dimethylphenoxy (PDMP) radicals, have been observed by esr spectroscopy, while benzylic-type radicals have been detected by spin trapping experiments using nitrosodurene under UV irradiation conditions. The changes of FTIR spectra obtained under accelerated photo-oxidative conditions show the formation of primary oxidation products such as aromatic aldehydes and quinones. The direct formation of radical cations and superoxide anions by a photo-induced electron-transfer reaction is suggested under our conditions. In addition, some results on the of photo-oxidation PPO/PS blends as a function of polystyrene tacticity are also reported. In the case of syndiotactic polystyrene the blend photostability shows some differences in comparison with the blend containing atactic polystyrene. This effect has been ascribed to the absence of excimers in syndiotactic polystyrene which are not revealed by fluorescence measurements. Finally, the chemical modification of PPO with bromine gave a bromomethylated PPO with different amounts of CH₂ Br groups, which has been used for further substitution reactions with alkoxy sodium salts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and 4-hydroxy-1,2,2,6,6-pentamethylpiperidine (PMPP). The accelerated photo-oxidation of a modified copolymer PPO-PMPP containing a 60% PMPP moieties as side groups and its blends with pure PPO has been followed by FTIR and esr spectroscopies. Some comparisons with a commercially available hindered amine light stabilizers (HALS) and a modified copolymer PPO-PMPP are also reported under the same photo-oxidative conditions.     

苯乙烯类塑料耐老化性能研究

对纯聚苯乙烯(PS)、高抗冲聚苯乙烯(HIPS)、PS/(苯乙烯/丁二烯/苯乙烯)共聚物(SBS)共混物、添加助剂的PS和HIPS等5组试样进行紫外光加速老化。表征了5组试样老化前后的力学性能、特性粘度、分子链结构的变化。研究表明,紫外光加速老化使材料的力学性能降低,表层发生龟裂;表层的溶液粘度下降较明显,距厚度大于0.4mm时其粘度下降缓慢;傅立叶变换红外光谱谱图中在1720cm-1处出现明显的吸收峰,表明有CO生成;纯HIPS、添加助剂的HIPS和PS/SBS共混物在910、966cm-1处的吸收峰强度明显减弱,表明发生了烯烃碳碳双键的断裂,添加助剂的HIPS老化后的透过率保持率最高。     

Evaluation of the birefringence of uniaxially oriented poly(2,6-dimethyl 1,4-phenylene oxide)-atactic polystyrene blends

The intrinsic birefringence of atactic polystyrene and poly(2,6-dimethyl 1,4-phenylene oxide) in their compatible blends are obtained from coupled birefringence and infra-red dichroism measurements. The experimental value obtained for poly(2-6-dimethyl 1,4-phenylene oxide) is in reasonable agreement with the value calculated from bond polarizabilities. These results allow evaluation of the angle between the normal to the benzene ring of polystyrene and the chain axis. This angle appears to be constant as a function of draw ratio and poly(2,6-dimethyl 1,4-phenylene oxide) percentage in the 0–35% studied range.     

Tensile strength of thermoplastic blends and composites

Failure of purely thermoplastic blends has so far, in contrast to that of thermoplastic-elastomeric blends, not been studied extensively. In this investigation, the tensile strength of the brittle thermoplastics polymethylmethacrylate and polystyrene, of their random copolymers, their blends, and also of blends of polymethylmethacrylate with the copolymers was measured. The polymers behave all mechanically similarly, but the blends assume all degrees of miscibility and coarseness of phase morphology. For comparison with the blends, also macroscopic composites were tested.     

热塑性聚氨酯共混改性研究进展

综述了热塑性聚氨酯与聚烯烃、聚苯乙烯、工程塑料(聚碳酸酯、ABS、聚甲醛、苯乙烯一丙烯腈共聚物、聚酰亚胺、聚酰胺等)、环氧树脂、橡胶、短纤维、聚氯乙烯树脂等共混研究进展,共混改性后的材料在某些性能上得到提高或改善,共混的研究为开发新材料提供了新途径,扩大了热塑性聚氨酯的应用。