Xinxiang Bolite Rubber Products Co., Ltd. Address: Daqu Town Industrial Park, Fengquan District, Xinxiang City Phone: 0373-5788884 Contact: Manager Han Mobile phone number: 13007663261 Mobile phone number: 13569839119 QQ: 1171150508 Fax: 0373-5788884 Email: email@example.com
What is the reason why the newly produced plastic products are very brittle?
Release: admin Browse: 341 times
In fact, there are many reasons for the brittleness of plastic products . Some are related to materials, some are related to molds, and some are related to equipment debugging. There are various reasons, but what are the specific factors we analyze.
The existence of internal stress in the product will seriously affect the mechanical properties and performance of the product. Due to the existence and uneven distribution of the internal stress in the product, the product will crack during use.
In injection molded products, the local stress state is different everywhere, and the degree of deformation of the product will depend on the stress distribution.
There is a temperature gradient when the product is cooled, and the uneven shrinkage generates stress.
When the melt enters a mold with a lower temperature, the melt close to the cavity wall is rapidly cooled and solidified, so the molecular chain segment is “frozen”. Due to the solidified polymer layer, the thermal conductivity is poor, resulting in a large temperature gradient in the thickness direction of the product.
The core of the product solidifies so slowly that when the gate is closed, the melt unit in the center of the product has not yet solidified. At this time, the injection molding machine cannot replenish the cooling shrinkage.
In this way, the internal shrinkage of the product is opposite to that of the hard skin layer; the heart is in static stretching and the surface layer is in static compression.
If the cavity pressure is maintained before the gate is closed, it is beneficial to increase the product density and eliminate cooling temperature stress, but a large stress concentration will occur near the gate.
From this point of view, when the thermoplastic polymer is molded, the larger the pressure in the mold, the longer the holding time, which contributes to the reduction of the shrinkage stress caused by the temperature, which in turn will increase the compressive stress.
Increase mold temperature, reduce injection, dwell pressure, and dwell time. The "hot water bath" can be performed after the product is ejected from the product to eliminate residual stress.