Because of the light weight, good toughness and easy to form. The cost is low. In modern industry and daily products, more and more plastics are used instead of glass, especially in optical instruments and packaging industries, and it has developed rapidly. But because of the requirements of its transparency, wear-resistant parts to be high, impact toughness is better, back to the plastic composition, injection molding process, equipment. A lot of work should be done to ensure that the […]
The versatility of ABS comes from its three monomers, propylene, butadiene and styrene; B stands for butadiene, providing toughness and impact properties; S stands for styrene, providing rigidity and processability. ABS has excellent flowability and comprehensive properties.
Yellowish granular or bead resin. Non toxic, tasteless. Melting temperature 210 ~ 240 ℃, thermal decomposition temperature more than 250 ℃, density 1.03 ~ 1.07 / ^ 3. Soluble in aldehydes, ketones, esters and some chlorinated hydrocarbons. Insoluble in most alcohols and hydrocarbons. […]
Generally speaking, the yellowing of plastic products is caused by the aging or degradation of materials. Generally, PP is caused by aging (degradation). Due to the existence of the upper side group of polypropylene, its stability is not good, especially in the case of light. Generally, light stabilizers are added. As for PE, because there is no side base, there is not a lot of yellowing at the initial stage of processing or use. PVC will turn yellow, which […]
Under the sunlight, there are striped pigment bands in the products. This problem should be considered from two aspects: the physical and mechanical properties of plastics and the molding process of plastics
1. The temperature of the injection molding equipment is not well controlled, and the color masterbatch cannot be fully mixed with the resin after entering the mixing chamber.
2. Injection molding machine did not add a certain back pressure, screw mixing effect is not good.
3. Poor dispersion of Color […]
PC has excellent performance, high transparency, good impact toughness, creep resistance, wide range of temperature. The process characteristics of PC are: the sensitivity of melt viscosity to shear rate is small, but it has great sensitivity to temperature, no obvious melting point, high viscosity of melt, easy hydrolysis of resin at high temperature and easy cracking of products. In view of these characteristics, we should pay special attention to the different treatment: to increase the fluidity of the melt, […]
Under normal circumstances, the surface gloss of injection molded parts is mainly determined by the type of plastic, colorant and surface finish of the mold. But often because of some other reasons, the surface color and luster defects of products, surface dark and other defects. The causes and solutions are as follows:
(1) Poor finish of the mold, rust on the surface of the cavity, poor exhaust of the mold.
(2) The pouring system of the mould is defective, so it […]
The fusion joint melt plastic in the cavity is confluent in multiple strands due to the penetration hole, the flow rate is not consistent, and the area where the filling material flow is interrupted. This kind of fusion of low temperature molten material can not fully fuse and produce linear fusion joint. In addition, the injection filling of the gate will also produce the fusion joint. This kind of weld mark only occurs at the fusion part of […]
Adjust and compare the injection molding process temperature, pressure, speed and position parameters
Temperature measurement and control is very important in injection molding. Although these measurements are relatively simple, most injection molding machines do not have enough temperature sampling points or lines.
On most injection molding machines, the temperature is sensed by thermocouples. A thermocouple is basically made up of two different wire tails. If one end is hotter than the other, a tiny telecommunication will be generated; The more heat, the stronger the signal.
Thermocouples are also widely used as sensors in […]
In the process of plastic production, various reasons lead to different defects of various products. The following are common product defects and solutions:
There are some non design reasons, such as mold temperature, material temperature, high temperature, insufficient holding time and residual stress, etc. when the deformed products are out of the mold. The product wall thickness and uneven shrinkage, improper gate position and ejector position, and mold sticking must be considered in the design.
The vacuum state caused by too […]
What is unstable gauge?
Dimensional instability (unstable gauge) refers to the change in the size of plastic parts between each batch of molded products or between each cavity molded products produced by each mold under the same injection molding machine and molding process conditions. As shown in the figure:
The change of product size is caused by abnormal equipment control, unreasonable injection molding conditions, poor product design and material performance change.
Analysis and elimination of injection defects of unstable gauge
1) Inconsistent conditions […]