Brief Introduction to the Thermal Stability of Plastic Steel Packing Strap Material PVC Plastic

Brief Introduction to the Thermal Stability of Plastic Steel Packing Belt Material PVC Plastic
　　Heat Stabilizer Heat stabilizer is an auxiliary agent that is formulated into polyvinyl chloride resin to improve the thermal stability of polyvinyl chloride at high temperatures. It is generally believed that heat stabilizers have a common feature, that is, the receiver of hydrogen chloride, which can capture the hydrogen chloride generated by the decomposition of polyvinyl chloride, and prevent the free hydrogen chloride in the system from causing damage to the polyvinyl chloride. Thermal decomposition produces an accelerating effect. Some heat stabilizers such as cadmium salts can also coordinate with the allyl chloride in polyvinyl chloride or react with it to stabilize it. Compounds that can be used as stabilizers for polyvinyl chloride are mainly metal sulphates (such as zinc stearate, calcium stearate, lead stearate, cadmium stearate, barium stearate, etc.) and organotin compounds (such as lauric acid) Dibutyl tin, dibutyl tin maleate, etc.), epoxy compounds (such as epoxy soybean oil), etc.
The main performance indicators of 　　 heat stabilizer are heat resistance, blooming and sweating, resistance to vulcanization pollution, etc.
　　1) Heat resistance. The heat resistance is divided into static heat resistance (heat resistance measured by the test tube method, heat drying method or hot pressing method, reflecting the heat resistance of a simple chemical reaction under static state) and dynamic heat resistance (by a two-roller Or the heat resistance measured by the plasticizer is related to the effect of mechanical force), the latter can better reflect the thermal stabilization effect during the molding process. Some stabilizers, such as maleic acid ester organotin, have good static thermal stability, but the lubricity is not good enough, so the dynamic heat resistance is not good, and the application often needs to be equipped with an appropriate lubricant. Another thing that needs attention is the issue of initial heat resistance and long-term heat resistance. For example, a polyvinyl chloride system stabilized by barium soap will turn pink during the heat aging process, but the color will not change much after long-term heat aging; while a polyvinyl chloride system stabilized by cadmium soap will become pink during heat aging. The thermal stability is good at the beginning of the process, but it turns black after long-term thermal aging. There is also the problem of the synergistic effect of thermal stabilizers, that is, the stabilizing effect of a reasonably matched composite stabilizer is much higher than that of a single stabilizer in the composite stabilizer.
　　2) Frosting and sweating. When the compatibility between the stabilizer and the polyvinyl chloride resin is not good, it will move from the inside of the product to the surface of the product after being mixed into the polyvinyl chloride plastic. If the heat stabilizer is solid and moves to the surface of the product, it is called 'blooming'; if the heat stabilizer is liquid and moves to the surface of the product, it is called 'sweating'. Blooming and sweating can be avoided as far as possible by the following methods: control the amount of heat stabilizers that are easy to bloom and sweat, or use a small amount of blooming inhibitors, such as barium laurate, liquid barium/cadmium stabilizers, etc.
　　3) Resistance to vulcanization pollution. When some stabilizers encounter sulfur, hydrogen sulfide or other sulfides, they will generate ferrous metal sulfides and cause discoloration and pollution of products. The ability of stabilizers to resist sulfur and sulfide discoloration is called resistance to sulfide pollution.