As mentioned above, polyether modified polysiloxane has some shortcomings; alkyl modified polysiloxane has just these advantages. This series of polysiloxane products also belong to comb structure. The molecular weight of this kind of products is relatively small, about 10000, N + m is about 30-50. The purpose of modification with alkyl is mainly to improve the thermal stability, compatibility and instability of foam, and even has the function of defoaming. However, with the increase of the modified alkyl chain, its ability to reduce the surface tension also decreased. The relationship between the length of alkyl chain and surface tension is shown in Table 1-1. The modified alkyl chain - CH3 - CH2 - CH3 - (CH2) 9 CH3 surface tension / (Mn / M) 20.6 26.231.4 generally, the carbon chain is controlled between c1-c14, so the molecular weight is not too large. Three modification methods of polydimethylsiloxane are introduced above. Different modification methods, different amount and structure of modifier, and different product performance. The heat resistance of leveling agent produced by three different modification methods are also different. Moneng-1060 silicone modified polysiloxane has good heat resistance, and it can be used in the temperature range of 200-220 ℃. In order to give the film a good smoothness, molenergy chemical has introduced some terminal modified organosilicon. Reactive leveling agent in the coating and ink system of radiation fixed telephone has the defects of poor wetting, not smooth enough, easy to scratch and poor leveling. In view of these problems, Moneng chemical company has provided a series of reactive organic modified polysiloxane acrylic leveling agents, including moneng-1073 and 1074. The former has good compatibility and poor smoothness. The latter has poor compatibility and good smoothness. It can be seen from the structural formula that the modified organic compound is acrylate, which is used to adjust its fluidity and compatibility. Its smoothness is determined by siloxane. The double bond of acrylic group can participate in the polymerization reaction of free radicals, forming a film firmly anchored on the surface of the film together with the resin.