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Key Points For Molding And Molding Of Heat-resistant ABS Resin Nov 03, 2017

Reducing the internal stress of the product is the key to the injection molding of heat-resistant ABS. In this paper, the key points for the forming of heat-resistant ABS resin are Shared with five aspects such as mold design, material drying, forming temperature, pressure pressure and time, mold temperature and so on.

Ordinary ABS heat resistant performance is not good enough, now, by adding ɑ - and N - phenyl methyl styrene copolymer heat resistant agent such as maleic imide copolymer developed a series of heat-resistant ABS resin, thermal deformation temperature (HDT) 90-120 ℃. Such as Shanghai kumho Japan Korea double yi (Economic&Easy) series of heat-resistant ABS resin can meet the demand of 95-109 ℃ heat resistance of different level, can be widely used in small home appliance such as microwave oven, electric cooker, electric heaters and hair dryers; And higher heat resistance of series of products, can heat 109-109 ℃.

Due to the molecular structure of the heat resistant ABS containing high rigidity of benzene and N - phenyl groups, improve the heat resistance at the same time, also increased the space steric effect of the molecular chain, reduce the relaxation of molecular chain speed, easy to make the internal stress of products there is a big, lead to products stress cracking, stress white, defects such as brittle. Therefore, reducing the internal stress of the product is the key to the injection molding of heat-resistant ABS.

1.Product mould design

The thickness of the product wall is equal to one, and the thickness difference of ABS products should be controlled at 25%, so that the thickness of the wall is not too large and the local stress concentration can be caused. The base of the weak pillar needs to increase the R Angle or add reinforcement to prevent the column from breaking. Card buckle design, card buckle the root of the need to pour R Angle, the size of the R Angle depends on the thickness of the product, R Angle and wall thickness ratio should be above 0.3, with the increase of the ratio, the internal stress reduced gradually, but also want to consider product surface shrinkage problem. The design of die cooling watercourse should ensure the uniformity of cooling, avoiding the internal stress caused by uneven cooling and different shrinkage.

2.The material is dry

Usually, heat-resistant ABS resin can absorb the moisture in the air in the process of storage transportation, bibulous rate is changed along with the air humidity, generally between 0.2 ~ 0.4%, so the material must be fully dry, make the material moisture content is below 0.05%, the best under 0.02%, otherwise possible adverse phenomenon, silver and other surface spray. Heat-resistant ABS resin drying temperature is higher than ordinary ABS, usually is 80-95 ℃, the drying time 3 to 4 hours.

3.Mold temperature

Mold temperature is heat-resistant ABS process needs to pay special attention to one parameter, the setting is to ensure that the heat-resistant ABS plastic into a benchmark in full, should try to use the intermediate value of molding temperature is recommended supplier the temperature on the partial area, molding temperature increase will significantly lower the viscosity of the heat-resistant ABS, increase liquidity in the resin, the flow distance is longer, to ensure that the material has enough ability to fill. The heat-resistant ABS HU600 kumho, for example, Japan Korea suggested molding temperature is 240-260 ℃. In principle, when using the recommended forming temperature limit, the glue should be kept as short as possible to avoid high temperature degradation.

4.Pressure pressure and time

In the case of heat resistant ABS, the setting of pressure pressure and time is reasonable, directly affecting the size of the internal stress. The increase of the holding pressure will make molecular gap narrowed segment range decreases, and the volume of the melt and density change, forces between molecules increase, can improve the shrinkage and internal quality, but can lead to internal stress, therefore, on the premise of guarantee the quality of product appearance as far as possible choose low pressure maintaining pressure.

The setting of the pressure control time is based on the solidification of the gate with the cooling, and the screw is no longer the time to apply pressure to the molding products. The overpressure time is too long, it is easy to fill the material excessively, the molecular gap becomes smaller and the internal stress becomes larger. The pressure time is too short, the product is easy to produce shrinkage, the size is not stable. The timing of the protection time shall be the best guaranteed time when the weight of the product is no longer changed.

5.Mold temperature

The author suggest when molding heat-resistant ABS use to control mold temperature, mold temperature machine suggested that mold temperature is 60-80 ℃. High mold temperature, often produce good flow, high melting connection strength, small product internal stress

Finally, the elements of each molding process should be considered and coordinated.