Brittle-tough transition in elastomer toughening thermoplastics: effects of the elastomer stiffness

The effect of the elastomer stiffness on brittle-tough transition in elastomer toughening thermoplastics was quantitatively studied. A correlation between brittle-tough transition temperature and the elastomer stiffness was obtained. The calculation from this correlation showed that the brittle-tough transition temperature (T-bt) Of elastomer toughening thermoplastics slowly increased up to one tenth of the modulus of matrix, thereafter it increased rapidly with increasing the modulus of elastomer. The results indicated that the modulus of the elastomer must be one-tenth or less of that of the matrix in order to be effective at low temperature. (C) 2001 Elsevier Science Ltd. All rights reserved.

Effects of rubber content and temperature on unstable fracture behavior in ABS materials with different particle sizes

The fracture behavior of ABS materials with a particle diameter of 110 nm and of 330 nm was studied using instrumented Charpy impact tests. The effects of rubber content and temperature on fracture behavior, deformation mode, stable crack extension, plastic zone size, J-integral value, and crack opening displacement were investigated. In the case of a particle size of 110 nm, the material was found to break in a brittle manner, and the dominant crack mechanism was unstable crack propagation. Fracture toughness increases with increasing rubber content. In the case of a particle size of 330 nm, brittle-to-tough transition was observed. The J-integral value first increases with rubber content, then levels off after the rubber content is greater than 16 wt %. The J-integral value of a particle diameter of 330 nm was found to be much greater than that of 110 nm. The J-integral value of both series first increased with increasing temperature until reaching the maximum value, after which it decreased with further increasing temperature. The conclusion is that a particle diameter of 330 nm is more efficient than that of 110 nm in toughening, but for both series the effectiveness of rubber modification decreases with increasing temperatures higher than 40 degreesC because of intrinsic craze formation in the SAN matrix at temperatures near the glass transition of SAN. (C) 2000 John Wiley & Sons, Inc.

Efforts to decrease crosslinking extent of polyethylene in a reactive extrusion grafting process

Grafting of acrylic acid and glycidyl methacrylate onto low density polyethylene (LDPE) was performed by using a corotating twin-screw extruder. The effects of residence time and concentration of initiator and monomers on degree of grafting and gel content of grafting LDPE were studied systematically. Paraffin, styrene, p-benzoquinone, triphenyl phosphite, tetrachloromethane, and oleic acid were added to try to decrease the extent of crosslinking of LDPE. 4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy (4-hydroxyl-TEMPO) and dipentamethylenethiuram tetrasulfide were also tried to inhibit crosslinking reaction of LDPE during its extruding grafting process. It was found that p-benzoquinone, triphenyl phosphite and tetrachloromethane were good inhibitors for crosslinking of LDPE. (C) 2000 John Wiley & Sons, Inc.

Advanced research work on radiation cross-linking of polymers in CIAC

Recent research carried out at the Chinese Institute of Applied Chemistry has contributed significantly to the understanding of the radiation chemistry of polymers. High energy radiation has been successfully used to cross-link fluoropolymers and polyimides. Here chain flexibility has been shown to play an important role, and T-type structures were found to exist in the cross-linked fluoropolymers. A modified Charlesby-Pinner equation, based upon the importance of chain flexibility, was developed to account for the sol-radiation dose relationship in systems of this type. An XPS method has been developed to measure the cross-linking yields in aromatic polymers and fluoropolymers, based upon the dose dependence of the aromatic shake-up peaks and the F/C ratios, respectively. Methods for radiation cross-linking degrading polymers in polymer blends have also been developed, as have methods for improving the radiation resistance of polymers through radiation cross-linking.

Ring-banded spherulite surface structure of poly(epsilon-caprolactone) in its miscible mixtures with poly(styrene-co-acrylonitrile)

The surface structure of the ring-banded spherulites in polymer blends PCL/SAN (90/10) was studied by optical microscopy, SEM, and TEM, respectively. It is interesting to find that the surface structure of the ring-banded spherulites in polymer blends PCL/SAN (90/10) is made up of the convex bands. The landscape of the convex bands on the surface has been little emphasized before. Radial fibrils are arranged on the bands. Details of the radial fibrils on the bands can be observed by TEM. The landscape of the convex bands on the surface and twisting of lamellae in the convex bands for PCL/SAN blends may be useful to explain the formation mechanism of the ring banded spherulites in polymer blends or even in homopolymers. (C) 1999 John Wiley & Sons, Inc.

Luminescence enhancement by blending PVK with blue PPV copolymer

The PL and EL properties of the polymer blends of PVK and blue PPV copolymer were studied. Considerable enhancement of both the photoluminescent and the electroluminescent intensity were observed by using the polymer blends as emission layer in the LED devices. The energy transfer process and the formation of exciplex in the polymer blends were also discussed.

Studies on the interfacial adhesion between functionalized polypropylene and polyamide 1010

The interface behavior of polyamide 1010 (PA1010) and polypropylene (PP) was studied. In order to improve their interfacial adhesion, functional PP was prepared by means of grafting glycidyl methacrylate (GMA) on PP main chains and used instead of plain PP. Several technological characterizations were performed here on their interfaces. ESCA was used to confirm that some kind of reaction occurred between end groups of PA1010 and epoxy species of PP-g-GMA. The peel test was adopted to measure interfacial adhesion. It was found that the fracture energy of interfaces between PA1010 and PP-g-GMA was dramatically increased with the content of GMA. Their interfaces were observed as being blurred by using SEM and TEM and a crack that could be seen in the case of the interfaces of the PA1010 and the plain PP disappeared.

Monte Carlo simulation of phase separation of A/B/A-B ternary mixtures

Monte Carlo simulations were used to model A/B/A-B ternary mixtures with different AB diblock copolymer volume fractions for which both the dispersed and continuous phase volume fractions were kept constant. For concentrations of the diblock copolymer below a critical value, the domain size increment of the dispersed phase decreases linearly with the copolymer concentration. This is in agreement with the predictions of Noolandi and Hong. The dependence of the domain size as a function of the copolymer volume fraction can also be fitted by the equation of Tang and Huang. Our simulations indicate, for the first time, that the micelles form before saturation of the interface occurs. This means that the formation of the micelles is not a result of the saturation of the interface.

Phase-separation behavior of the system PES/phenoxy: An application of the Sanchez-Lacombe lattice fluid theory

Cloud-point curves reported for the system polyethersulfone (PES)/phenoxy were calculated by means of the Sanchez-Lacombe (SL) lattice fluid theory. The one adjustable parameter epsilon(12)*/k (quantifying the interaction energy between mers of the different components) can be evaluated by comparison of the theoretical and experimental phase diagrams. The Flory-Huggins (FH) interaction parameters are computed based on the evaluated epsilon(12)*/k and are approximately a linear function of volume fraction and of inverse temperature. The calculated enthalpies of mixing of PES/phenoxy blends for different compositions are consistent with the experimental values obtained previously by Singh and Walsh [1].

辐照对不相容聚合物共混物相界面粘接的影响

介绍了改善不相容聚合物共混物界面粘接状况的一种崭新方法，应用SEM、TEM技术研究了辐射敏化界面反应对iPP/LDPＥ不相容共混物体系相界面粘接的影响，并结合溶解度参数的方法评估了多官能团单体—三烯丙基异氰酸酯(TAIC)在iPP/LDPE共混物中的分布状况。结果表明，辐射增强界面反应的方法是改善不相容聚合物共混物界面粘结的有效途径。

兰光转换膜的研制及其水稻育秧效果试验

本文介绍了以LDPE与LLDPE为基料的农用兰光转换水稻育秧膜的研制与性能，以及该膜用于水稻育秧的应用效果试验。最终增产效果为5．5％。

Crystallization of micelles and matrix in dilute diblock copolymer/homopolymer solutions

The crystallization, morphology, and crystalline structure of dilute solid solutions of tetrahydrofuran-methyl methacrylate diblock copolymer (PTHF-b-PMMA) in poly(ethylene oxide) (PEO) and PTHF have been studied with differential scanning calorimetry (DSC), X-ray, and optical microscopy. This study provides a new insight into the crystallization behavior of block copolymers. For the dilute PTHF-b-PMMA/PEO system containing only 2 to 7 wt % of PTHF content, crystallization of the PTHF micellar core was detected both on cooling and on heating. Compared the crystallization of the PTHF in the dilute solutions with that in the pure copolymer, it was found that the crystallizability of the PTHF micellar core in the solution is much greater than that of the dispersed PTHF microdomain in the pure copolymer. The stronger crystallizability in the solution was presumably due to a softened PMMA corona formed in the solution of the copolymer with PEG. However, the "soft" micelles formed in the solution (meaning that the glass transition temperatures (T-g) of the micelle is lower than the T-m of the matrix phase) showed almost no effects on the spherulitic morphology of the PEO component, compared with that of the pure PEO sample. In contrast, significant effects of the micelles with a "hard" PMMA core (meaning that the T-g of the core is higher than the T-m of the PTHF homopolymer) on the nucleation, crystalline structure, and spherulitic morphology were observed for the dilute PTHF-b-PMMA/PTHF system. (C) 1998 John Wiley & Sons, Inc.

Preparation and characterization of phenoxy resin/poly(4-vinylpyridine) interpolymer complexes

The compositions and structures of interpolymer complexes formed by mixing phenoxy resin (PHEB) and poly (4-vinylpyridine) (P4VPy) in chloroform have been studied by means of elemental analysis, DSC, FTIR, UV and XPS, In the meantime, the corresponding blends prepared have been characterized and compared. The results show that compositions of the complexes were identical with the ratio of equimolar interactive units. All blends were miscible and their compositions were related to the feed ratios. Based on the experimental results, process of formation of the complex is depicted.