有機過酸化物は構造内にO-O結合を持ち,熱によりO-O 結合が開裂し,種々のラジカルを発生する.発生したラジ カルは,その構造により異なった機能を発現する.そのラ ジカル種の特徴を利用し,重合,架橋,分子量調整,グラ フト反応等の用途に使用されている.重合用途では,レジ 袋,各種フィルム等に使用されている低密度ポリエチレ ン,配管,雨樋等に使用されている塩ビ,また,各種塗料 に使用されているアクリル樹脂等の汎用樹脂の製造に欠く 事の出来ない重合開始剤として広く用いられている.一方, 樹脂に添加,加工処理することにより,架橋反応(Crosslinking),β開裂による低分子量化(Degradation),ある いはモノマーをポリマー鎖に直接導入したグラフト反応 等,種々の樹脂改質剤として使用されている. 本稿では,架橋反応およびグラフト反応に有効な有機過 酸化物種について述べるとともに,技術的ニーズについて も記述する.
The changes in the thermophysical and fire- and heat-shielding properties of compounds based on ethylene propylene rubber when hollow aluminosilicate microspheres (MSPs) are introduced were studied. The MSPs were treated with a heteroorganic modifier – phosphorus–boron–nitrogen-containing oligomer (PEDA), which is a combustion inhibitor. The physicomechanical characteristics of the vulcanisates and the magnitude of the Payne effect were determined. The vulcanisates contained 30 parts filler BS 120 and a sulphur vulcanising group, and also 1 part MSPs. The optimum MSP/PEDA ratio was 1:3. The ultra-high-frequency treatment of the mixture of MSPs and PEDA was especially effective. Using a Versa 3D electron microscope, the increase in the diameter of MSPs as a result of modification and the change in the atomic composition of the surface of MSPs were recorded. The modification of MSPs leads to a reduction in the Payne effect, to an increase in the interaction between rubber and filler, to a reduction in density, and to an increase in the cohesive strength. By comparison with a specimen without MSPs, the rate of linear combustion according to GOST 28157-89 decreases by 10%. The modification of MSPs leads to a decrease in this parameter by 5% by comparison with a specimen containing unmodified MSPs. The time of heating to 100°C of the unheated surface of a specimen heated on the other side to 2000°C increases by 50–60% and 11–19% respectively. The resistance to separation under conditions of erosion entrainment increases by 4–7%. The use of PEDA makes it possible to improve the adhesion of coating to substrate. A scheme of the interaction of MSPs and PEDA is put forward.
An algorithm for selecting the polymer matrix materials for a composite with a non-standard set of plastoelastic properties is considered.
The effect of hydrophilic additives – MC-2000 methyl cellulose and sodium polyacrylate – on the properties of a vulcanisate based on Neoprene W was studied. The rubber mixes were prepared in two stages: at the first stage, hydrophilic additives were introduced into the rubber; at the second stage, the remaining ingredients were introduced. Vulcanisation was carried out at a temperature of 150°C for 30 min. The viscosity of the rubber mixes, M, was measured at 120°C on an MVR 3000 Basic viscometer (MonTech), and the vulcanisation characteristics and vulcanisation rate, v, were measured on an MDR 3000 Basic rheometer (MonTech) at 170°C in accordance with ASTM D2084-79. From the results of these measurements it follows that, with the combined use of methyl cellulose and sodium polyacrylate, there is a synergistic reduction in M and in the vulcanisation rate of the rubber mixes. A vulcanisate containing both hydrophilic additives possesses the best hydrosorption properties and has satisfactory physicomechanical properties (nominal tensile strength, elongation at break, hardness, and tear strength). The values of these properties and their changes on exposure of the vulcanisate to distilled water (70°C, 24 h) meet the requirements laid down for water-swelling rubber sealing elements.
