Các vật liệu đàn hồi không tương thích cao, như NR và NBR, rất khó tạo thành hỗn hợp có cơ tính tốt. Nhiều yếu tố ảnh hưởng như kỹ thuật cán luyện, hệ kết mạng đã được khảo sát. Trong đó, biện pháp thêm vào các polymer, copolymer tăng sự tương thích giữa hai pha cao su mạng lại hiệu quả cao. Phần tài liệu bên dưới sẽ cung cấp thêm thông tin về vấn đề này.
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Blends of highly incompatible elastomers may sometimes be improved by the addition of small amounts of another polymer. Setua and White [1] applied this technique to improve the homogeneity of binary and ternary blends of CR, NBR and EPM. When a small amount of chlorinated polyethylene is added to NBR/EPM or CR/EPDM blends, they mix more rapidly. The chlorinated polyethylene acts as a compatibilizing agent which appears to form a skin on the EPM particles that helps the larger NBR chunks adhere to them. This increased adhesion and polarity at the EPDM surface increases the compatibility. The presence of block or graft copolymers can also alleviate blending of incompatible elastomers as they can alter interfacial properties [2-6]. Ideally the block or graft component should contain a segment which is chemically identical to one of those in the respective phases, but the desired effect may still be achieved if one polymer of the graft is miscible with, or adhered to, one of the phases.
It is possible to obtain considerable improvement in the phase morphology and tensile properties of NR/NBR gum blend vulcanizates by incorporating typically 5-20% of methyl methacrylate grafted natural rubber (e.g. Heveaplus MG30), or chloroprene rubber (CR) (Chapter 7). MG30 is a mixture of graft copolymer with ungrafted NR and poly(methyl methacrylate), PMMA, present as a homopolymer. It was considered that there would be sufficient interaction between the PMMA graft chains and the acrylonitrile repeat units of the NBR for the graft copolymer to locate at the NR/NBR interface and thus reduce interfacial tension and hence phase size.
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Trích đăng từ sách Blends of Natural Rubber: Novel Techniques for Blending with Specialty Polymers, Andrew J. Tinker và Kevin P. Jones, Springer, 1998, trang 68 – 69
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