PVC of the - shaped material is usually used for the 62 - to - 65 (K) of the PVC resin. Because with the increase of the molecular weight of PVC and intermolecular van der Waals force or winding of a corresponding increase, increase the product's physical and mechanical strength, resistance to low temperature and heat resistance, light resistance and anti-aging properties is correspondingly enhanced. But the higher the degree of polymerization, the higher the processing temperature, the worse the processing flow, the more difficult the forming process.

In general, the special material is used to select the molecular weight distribution is narrow, so that the processing performance and product performance are more uniform, which is conducive to control the processing conditions and the quality of the products. Reduce product thermal stability, aging properties, mechanical properties such as low molecular weight; but high molecular weight will enable processing is not easy to be uniform plasticizing, resulting in the decline in product internal and external quality, there will be serious particles or "fish eye." The plastic time of PVC resin is also an important choice. In general for a certain degree of polymerization of PVC, the shorter the time of its plastic. Long time, the amount of heat stabilizer need to increase, the difficulty of matching lubricant matching, processing conditions are harsh, product quality is difficult to control, production costs increase.

PVC aging performance is also a very important indicator in the production of PVC profiled bar white doors and windows. The whiteness as an index, the minimum requirements for more than 74%, however, does not mean that the higher degree of plainly, processed appearance quality is good, which requires manufacturers to select raw materials special attention. At the same time, different batches of PVC raw materials can not be used together, so as to avoid the profile deviation, affecting the quality of.

1.2 heat stabilizer

At present, the lead salt heat stabilizer is the most widely used in the domestic PVC profile. Three salt (TLS) thermal stability of the best, two salt (DL) thermal stability is less than three salt, but the weather is better than three salt, salt and salt of the two three when the amount of salt is about 50%. Thermal stability of dibasic lead stearate (DLS) and lead stearate PbSt2 slightly worse but lubricity, both salt and salt and salt and use, the amount of 0.5 to 1.5 portions. The biggest disadvantage of lead is toxic and easy to change color.

The effect of metal soap heat stabilizer is less than that of lead salt, but it has a lubricating property. General metal soap heat stabilizer is not used alone, often for different metal soap and with or with lead salt and organic tin and used. According to the function and mechanism, it is divided into two main categories. The main metal soaps are Cd, Zn, and Ba, Ca are the main metal soaps. The use of the main, auxiliary, there is a synergistic effect. Metallic soap features are as follows:

(1) ZnSt2: is non-toxic and transparent, easy to cause "zinc burn", often with Ba, Ca soap and use.

(2) CdSt2: is an important type of transparent stabilizer, which is very toxic, and is not resistant to sulfide pollution, and is often used with Ba soap.

(3) PbSt2: has good thermal stability, doubles as a lubricant, easy separation of transparent poor, toxic, curing pollution serious, often with BA, CD soap.

(4) CaSt2: has good workability, no pollution, no toxicity, and is often used with Zn soap.

(5) BaSt2: anti sulfide pollution, transparent, often with Ca, Pb soap and use. Organotin thermal stability superior, good transparency, mostly non-toxic. But the price is too high, and most of the no lubrication, the current domestic PVC profile production in the very few.