Interactions between the components in isotactic polypropylene blended with EPDM

The interaction of isotactic polypropylene with ethylene propylene diene terpolymer in their blends has been investigated by use of differential scanning calorimetry, dynamic mechanical analysis, wide- and small-angle x-ray scattering, and by investigating the nucleation and kinetics of crystallization of the iPP component under the polarization microscope. It is found, that the dispersion of the EPDM component in the iPP matrix is dependent on blend composition and is maximal at 10% EPDM content. An interface layer between the two components is formed by migration of iPP molecules into the EPDM phase. A model for this interface is proposed.     

Instrumental neutron activation analysis of mass fractions of toxic metals in plastic

It is very challenging to decompose a plastic product for the purpose of analysis of hazardous elements contained. To circumvent such technical problem, it is imperative that an analyst employ a nondestructive analytical method free of any pretreatments. The analytical results of the concentrations of toxic metals such as Cd and Cr in polypropylene for seven samples at two different levels were obtained using the instrumental neutron activation analysis. This work was intended ultimately to establish certified reference materials (CRMs) of these metals in the polypropylene, traceable to the SI. The uncertainties associated with the analytical procedures were estimated in accordance with the ISO guideline. The results were subsequently validated by a comparison with those for CRM-680 and −681 of the Bureau Communautaire de Reference (BCR), which demonstrated acceptable agreement within their uncertainty ranges.     

INTROMISSION OF WATER-REPELLENT AND HYDROSCOPIC PROPERTIES SIMULTANEOUSLY TO PP BY PLASMA DISCHARGE METHOD

Plasma-induced surface graft copolymerization of acrylic acid on polypropylene non-woven fabric (PP-g-AA) and polypropylene membrane were reported. The extents of grafting were controlled by the plasma and polymerization condition. Hexadecyltrimethyl ammonium bromide was then coupled with the carboxyl group of PP-g-AA to obtain a polyion complex (PIC). At last, CF4 plasma was used to give PICs hydrophobic property. The moisture regain and water-repellency of the processed PICs was investigated. The surfaces were characterized using ATR FT-IR and XPS. The result indicates that the products have very high ability to adsorb moisture, even better than cotton fiber. At the same time, the products show excellent hydrophobic property, which can‘t be wetted by those reagents whose surface tensions were higher than 327mN/m.     

Growth transition and morphology change in polypropylene

The growth rate of isotactic polypropylene is deduced from microscopic observations during isothermal crystallizations. A change in the growth regime is observed at 138 C and interpreted as a Regime III Regime II transition, according to Hoffman's kinetic theory of polymer crystallization. A Regime II Regime I transition is also theoretically predicted at 155 C, i. e. at a temperature outside the investigated temperature range. The Regime III Regime II transition is related to the positive to negative change in the spherulite birefringence, which is generally attributed to a change in the organization of crystalline lamellae: quadritic arrays of intercrossing lamellae atT _c < 138 C (Regime III) and preferentially radiating lamellae atT _c > 138 C (Regime II). It is suggested that such a morphological change could be interpreted using the concept of non-adjacent re-entry introduced in Hoffman's kinetic theory. This interpretation could also explain the interspherulitic ruptures observed in negative spherulites.     

Effect of nucleating agent on the structure and properties of polypropylene/poly(ethylene-octene) blends

The effect of the sorbital nucleating agent on properties of the ethylene-octene copolymer (POE) toughened polypropylene (PP) was studied. The results show that the addition of POE increases notched Izod and Charpy impact strength significantly but impair the tensile strength and flexural modulus. As a nucleating agent (1,3,2,4-di(p-methylbenzylidene) sorbitol, DM) was added, the toughness and stiffness of toughed PP increased simultaneously at the same content of POE. This result shows that the toughness and stiffness of toughed PP are in balance. Polarized light microscopy analysis shows that with the addition of POE and nucleating agent, only a low level of PP spherulites were observed.     

离聚物Surlyn对PBT/PP共混体系的力学性能及形态结构的影响

用力学性能测试、ＤＭＡ、ＳＥＭ等方法研究了离聚物Ｓｕｒｌｙｎ对ＰＢＴ／ＰＰ共混体系的力学性能及形态结构的影响。结果表明，在ＰＢＴ／ＰＰ共混体系中引入少量Ｓｕｒｌｙｎ可以改善界面的粘接性，从而改善其力学性能。当共混体系中ＰＢＴ／ＰＰ的组份比不变（９０／１０）且Ｓｕｒｌｙｎ的含量为６ｐｈｒ左右时，共混物的冲击强度出现极大值；而弯曲强度在Ｓｕｒｌｙｎ含量为１－２ｐｈｒ左右时有最大值。当共混体系中Ｓｕｒｌｙｎ的含量不变（６ｐｈｒ）时，其力学性能随ＰＰ含量的增加而下降。用玻璃纤维增强共混体系，可显著提高力学性能。     

Determination of low levels of polymer additives migrating from polypropylene to food simulated liquids by capillary SFC and solvent venting injection

Summary Methods for the determination of specific migration of polymer additives from polypropylene to aqueous acetic acid and isooctane have been studied. The migrants were extracted from aqueous acetic acid and characterized by supercritical fluid chromatography (SFC) with flame ionization detection (FID) and mass spectrometry (MS). The isooctane simulant was concentrated and injected directly into the SFC. Injection of extracts after incubation, using the solvent venting injection technique in the SFC, enabled additive concentrations as low as 10 ppb in 150 ml simulant to be determined, corresponding to a specific migration level of approximately 1 g additive/dm² polymer.     

聚丙烯中硫酯类抗氧剂的质谱分析

采用齐格勒-钠塔催化剂使丙烯催化聚合得到聚丙烯。聚丙烯树脂本身具有优良的性能,如机械强度好,易加工成型,质量轻,成本低等,但也存在一些缺陷,如由于聚丙烯结构中存在叔碳原子,在造粒加工、贮存和使用过程中,易受热、光、氧等的作用而降解,导致材料的性能降低。为了抑制和延缓聚丙烯的氧化降解,需要在造粒阶段加入抗氧剂。本文以一种聚丙烯树脂样品为研究对象,采用溶剂抽提法提取有机添加剂,并用柱层析法对添加剂进行了分离;利用EI-MS分析了添加剂的组成,其中通过谱图解析,鉴定出添加剂中含有硫酯类抗氧剂-硫代二丙酸二(十四)酯(DMTP),并用此类常用化合物进行了验证,分析结果对树脂牌号的开发具有指导意义。     

Effects of processing parameters on the mechanical properties of polypropylene random copolymer

The mechanical properties of polypropylene random copolymer (PP-R) with different processing parameters were studied. Special attention is devoted to the investigation of the influence of masterbatch addition on the variation in the mechanical properties of injection moulded PP-R. Tensile, instrumented Charpy impact, Shore D hardness, differential scanning calorimeter (DSC) and Vicat softening temperature (VST) tests were conducted on the test samples containing different colour masterbatches varying from 0.5 to 10 wt%. The observed changes in the mechanical behaviour are explained by the type and level of masterbatch content. The natural UV weathering performance of the PP-R material was studied from the masterbatch type point of view. The effect of processing parameters on material performance was studied on samples which were directly obtained from extruded pipes and on injection moulded samples.

Finally, the effects of storage time on the polymer properties were investigated.     

Development of a novel potentiometric titration method for determination of polypropylene degradation

In this study, a novel potentiometric titration of hydroperoxide in degraded polypropylene (PP) is proposed. This titration is quite sensitive compared with the conventional ones such as UV and manual titrations, and its detection limit was about 2 meq/kg. The sensitivity was equal to that of molecular weight measurement by GPC for the degraded PP and, in addition, the volatilization behavior of the hydroperoxide could be detected. This titration was found to be very effective for the determination of PP degradation.