Introduction to shrink to the influence of plastic processing
As is known to all, in the process ofplastic processing, if you can't very good control the various parameters, then the plastic shrinkage is easily happened after finalize the design, which affect the precision plastic processing. So, systolic will bring plastic processing what bad influence? Below we together to get to know.
1, the contraction after processing:
Plastic shrinkage and can be divided into two categories, forming shrinkage and shrinkage after treatment. Contraction after processing products for a period of time after demoulding contraction, compared with the molding shrinkage, shrinkage is generally small. After the first reason for products due to shrinkage internal stress relaxation effect. For polymer molecular chain is rigid, products have a larger shrinkage; Mainly because the molecular chain rigidity movement speed, its molecular chain from one state to another state, need a longer time to rearrange the process, so after the contraction time longer, and the shrinkage rate is larger. Rigid molecular chain, on the other hand, easy to produce stress, forming will be slowly after in-situ stress relaxation. The second cause of shrinkage to crystallization. For crystalline polymer, plastic processing molding, did not achieve full crystallization, at room temperature can still crystallization, that cause the product's trace contraction.
2, the average shrinkage:
Due to shrinkage of plastic processing size affected by processing conditions is larger, therefore the shrinkage rate is not a fixed value, but a range, in the process of specific processing, various processing conditions can make the molding shrinkage rate increases, can choose 4% for concrete shrinkage; If the specific processing conditions conducive to the decrease of the molding shrinkage rate, can be selected for concrete shrinkage rate 2.5%. Of course, after a method of selecting difficulty is larger.