粘土的表面改性及其在硅橡胶中的应用

SURFACE MODIFICATION OF CLAY AND ITS APPLICATION TO SILICONE RUBBER

以福建产高岭土、伊利石类矿物中分离出来的粘土矿粉(粒度小于2μm)为原料,经硫酸处理后,再经硅烷偶联剂(与矿粉的质量比为1∶100)处理作为室温硫化硅橡胶的补强填料,其胶料密封存放6个月仍保持柔软,不固化。当改性粘土和气相白炭黑用量分别为50质量份时,改性粘土对高温硫化硅橡胶的补强效果好,硅橡胶的抗老化性能提高。

In accordance with distinct demands on the surface structure of its filler , the clay minerals (kaolin , illite) of Fujian origin are activated and modified by coupling agent and other physical and chemical methods . It results in the improvement of composite effect between filler and rubber substrate as well as in the increase of tonic effect and storage stability of rubber at room temperature .In acidation of clay , the strippings of Al3+ and Si4+ occur . Generally ,Al3+ combines by coordinate bond and Si4+ by covalent bond to the structure of day . Al3+ stripping is easier than that of Si4+ .By adding 100g of clay powder in a grain size of less than 2 μm to400mL of sulfuric acid in different concentrations and then heating backflow for 6h , washing , filter pressing and drying , a series of acid treated clays are prepared . Samples are taken for measuring chemical composition and weight loss at 600°C . The results shows that the rise of acid concentration leads to the relative increase of Al3+ stripping , the rise of Si4+ and Al3+ mass ratio lead to the decreas of hydroxyl content . The Al3+ stripping leads to the increase of charge in structural mesosphere . For electric equilibrium , the surface of clay will certainly adsorb H+ to form a Lewis acid active site capable of drawing electron or reacting with Lewis base . The lowering of clay hydroxyl concentration helps to apply silane for surface modi-fication . It was pointed out by literatures that much more significant effect of silane coupling agent would have obtained when the clay surface was in a low hydroxyl concentration .The acid treated day and silane coupling agent are mixed in a ratio of 100/1 .After fully dispersing by liquid dispersion , filter pressing and drying , they are treated at 80 - 110°C . Samples are taken for measuring IR absorption spectra . The day shows changes in IR absorption spectra after treating with coupling agent , the absorption peak at 395 cm-1 disappears and a new appears at 755 cm-1 .This accounts for the bonding of kaolin with the molecule of coupling agent .The day with a low surface hydroxyl concentration is modified by coupling agent .When this modified day is applied to the silicone rubber vulcanized at room temperature , it shows a physical performance met with practical use . To store the rubber material in air tight for six months , it remains soft .without any sign of hardening . When this modified clay is applied to the silicone rubber vulcanized at high temperature , its tonic effect and antiageing effect can be effectively promoted .