Polypropylene (PP) was modified by solid‐phase graft copolymerization with maleic anhydride (MAH) and styrene (St), using benzoyl peroxide as the initiator and xylene as the interfacial agent. Effects of various factors such as monomer concentration, monomer ratio, initiator concentration on grafting percentage, and acid value were investigated. The graft copolymer was characterized by Fourier transform infrared, pyrolysis gas chromatography—mass spectroscopy, and dynamic mechanical analysis, and the intrinsic viscosity of the extractive from the reaction product was investigated. The results showed that the grafting percentage and acid value of the graft copolymer of PP with two monomers (MAH and St) were considerably higher than those of the graft copolymer of PP with MAH alone. The graft segments were shown to be the copolymer of St and MAH with a substantial molecular weight. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2482–2487, 2000

Learning by interacting defines the endogenous path of economic development in modern innovation studies. In this paper, we aim to investigate the way that firms undertake interactive learning in the Chinese context by introducing the role of informal Guanxi network. In this way, this paper tries to bridge the gap between studies on firm innovation activities and those on the role of informal network for business performance. Based on an electronics firm survey in the Pearl River Delta, China, this article demonstrates that firms undertaking the highest intensity of interactive learning with the widest scope of business partners, such as foreign customers, domestic customers, parent companies, universities and sales agents, tend to achieve better innovation outcomes. It also verifies a more important role of interactive learning in incremental product innovation than in discontinuous innovation as electronics firms operate in highly modularized value chains. Furthermore, the intensive interactive learning firms have a much higher tendency to apply informal Guanxi networks with long-term business partners as a complement to deficient formal institutions in interactive learning than other firms. Overall, this paper contributes to the understanding of the form and effect of interactive learning in the Chinese context. Finally, the paper addresses the possible lock-in issue and points out further research questions on the changing pattern of interactive learning within a maturing institutional framework.

Vulcanization property and structure-properties relationship of natural rubber (NR)/silica (SiO 2 ) composites modified by a novel multi-functional rubber agent, N-phenyl-N!-("-triethoxysilane)-propyl thiourea (STU), are investigated in detail. Results from the infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) show that STU can graft to the surface of SiO 2 under heating, resulting in a fine-dispersed structure in the rubber matrix without the connectivity of SiO 2 particles as revealed by transmission electron microscopy (TEM). This modification effect reduces the block vulcanization effect of SiO 2 for NR/SiO 2 /STU compounds under vulcanization process evidently. The 400% modulus and tensile strength of NR/SiO 2 /STU composites are much higher than that of NR/SiO2/TU composites, although the crystal index at the stretching ratio of 4 and crosslinking densities of NR/SiO 2 composites are almost the same at the same dosage of SiO 2 . Consequently, a structure-property relationship of NR/SiO 2 /STU composites is proposed that the silane chain of STU can entangle with NR molecular chains to form an interfacial region, which is in accordance with the experimental observations quite well.

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