Thứ Sáu, 12 tháng 4, 2013

Các chất xúc tiến dùng trong hệ kết mạng lưu huỳnh


Trong quá trình kết mạng cao su bằng lưu huỳnh, việc sử dụng chất xúc tiến đóng một vai trò quan trọng. Phần tài liệu dưới đây mô tả khái quát về lịch sử hình thành và ưu khuyết điểm của các chất xúc tiến khác nhau.
Organic chemical accelerators were not used until 1906, 65 years after the Goodyear-Hancock development of unaccelerated vulcanisation, when the effect of aniline on sulfur vulcanisation was discovered by Oenslayer.
Aniline, however, is too toxic for use in rubber products. Its less toxic reaction product with carbon disulfide, thiocarbanilide, was introduced as an accelerator in 1907. Further developments led to guanidine accelerators. Reaction products formed between carbon disulfide and aliphatic amines (dithiocarbamates) were first used as accelerators in 1919. These were and still are the most active accelerators in respect to both crosslinking rates and extent of crosslink formation. However, most dithiocarbamate accelerators give little or no scorch resistance and therefore cannot be used in all applications.
The first delayed action accelerators were introduced in 1925 with the development of 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzothiazole disulfide (or 2,2´- dithiobisbenzothiazole) (MBTS). Even more delayed action and yet faster-curing vulcanisation became possible in 1937 with the introduction of the first commercial benzothiazolesulfenamide accelerator. Further progress was made in 1968 with the introduction of pre-vulcanisation inhibitor (PVI), N-cyclohexylthiophthalimide (CTP), which can be used in small concentrations together with benzothiazole sulfenamide accelerators.
Trích đăng từ sách Rubber Curing Systems, R. N. Datta, Smithers Rapra Press, trang 5 – 6, 2002
Nguồn: www.books.google.com.vn
(vtp-vlab-caosuviet)