交联电缆-电缆情缘网.PPT

无卤阻燃塑料 一个新的发展是在无卤阻燃聚烯烃电缆料中采用纳米层状硅酸盐，以改善材料的阻燃性和降低无机阻燃剂的用量。 如在以氢氧化铝阻燃的乙烯-乙酸乙烯酯电缆料中加入5%以下的纳米层状硅酸盐，电缆料中氢氧化铝的含量(质量分数)可由原来的65%降至45%，而材料释热速率峰值仍保持不变，且加工性、成炭性、耐光性和生烟性均有改善。 XPE PEX Pipes Heat Shrinkable tubes Wire and Cable main processes A one step process, called MonosilA two step process called Sioplas Monosil process (One step process) Sioplas process (Two steps process) Effect of silane structure VTMOS (Vinyl trimethoxysilane) reacts much faster than VTEOS (Vinyltriethoxysilanes). Effect of silane concentration The maximum concentration of VTMOS recommended is 2wt% concentrations can be used but these can result in lower gel contents which might very well prove to be suitable for some applications. Concentrations higher than 2wt% do not lead to significant higher gel contents. Effect of silane concentration Influence of the Organic Peroxide on PE Crosslinking The peroxide to be used needs to have decomposition kinetics which are suitable for the temperatures and residence times involved in the procesing of polyethylene. Generally DCP, Dicumyl peroxide or BPDIB; t-Butyl di-iso propyl benzene are recommended. The peroxide level required will vary with individual characterics such as : Melt flow index the initial polyethylene, density, polymerization process...) Desired melt flow index of the grafted PE Processing temperature during grafting Presence of some additives or fillers Influence of the Catalyst on PE Crosslinking DBTDL, dibutyltindilaurate is the preferred catalyst for crosslinking. Since the concentration of DBTDL affects significantly processability of the mixture of graft copolymers, it is sometime recommended to use it as low as 0.25wt% This reduction in concentration reduces the rate of crosslinking but does not affect the gel content of fully crosslinked graft copolymer Influence of the Process Conditions on PE Crosslinking Process conditions also have a strong impact on moisture crosslinking and final performance. Two key parameters a