Nylon 66 raw material properties of the performance in many ways, some only with its operational aspects, while others affect the molding method and process characteristics of the choice.
In the nylon 66 raw material melting state, its plastic melting, after molding cooling, the phenomenon of volume contraction occurred, and people call this phenomenon of contraction. How do you know the size of the shrinkage? This is mainly to see its shrinkage.
Nylon 66 raw material shrinkage principle: usually due to nylon 66 raw material thermal expansion and contraction, plastic deformation and demoulding caused by elastic recovery and other reasons. But not only in this form, it may also be due to plastic parts shape, flow direction and molding process parameters caused by the different shrinkage. Product contraction will affect the quality and accuracy of the final product, therefore, to minimize shrinkage, solve the problem before the first is to understand the causes of contraction:
1) nylon 66 raw materials plastic varieties: different plastics, its characteristics are different, shrinkage is also different. Increase the filler and other substances, will also cause the same kind of material shrinkage is different
2) nylon 66 raw material structure: the shape of the product itself, wall thickness, size, etc. will also have an impact on plastic shrinkage. Shape complex, thin wall, there are many pieces of the product shrinkage of the small.
3) nylon 66 raw material molding process conditions. Nylon 66 raw material mold temperature is high, melt cooling slow, then the density, shrink large. For the crystal material, high crystallinity, volume change, so the greater the shrinkage. While the nylon 66 raw material is a crystalline-semi-crystalline material, its shrinkage is actually no crystal shrinkage: nylon 66 raw material of the original shrinkage of 1.5-2.2, but adding 30% glass fiber, shrinkage into 1.2- 2.0, why add a glass, the shrinkage becomes smaller? This is what I mentioned earlier, the same material, but joined some of the accessories, its shrinkage will change.
Mold temperature impact shrinkage: that is, mold temperature and plastic parts inside and outside the cooling and density uniformity directly affect the size of each part of the amount of shrinkage and direction.
Molding pressure and holding time also have an impact on the shrinkage: high pressure, long time, shrinkage is small, but the direction of large; high temperature, the shrinkage, but the direction of small. Therefore, in the molding to adjust the mold temperature, pressure, injection speed and cooling time and other factors, may affect the plastic parts shrinkage.
