Low foaming hollow blow molding process and equipment
DATE：2022/1/17 8:34:03 / READ： / SOURCE：This station
Low foaming hollow blow molding process and equipment
At present, only a small amount of special equipment for low-foaming hollow blow molding is available on the market. Most low-foaming blow-molded parts still use ordinary plastic blow-molded equipment. The technological process is only improved on the original basis. Therefore, most of the knowledge of hollow plastic molding can refer to professional books on ordinary plastic hollow blow molding. Only some elements related to low-foaming hollow blow molding are introduced here, for the reference of readers when they further develop low-foaming hollow blow molding parts.1. Raw materials for low-foaming hollow blow molding
The raw materials for low-foaming hollow blow molding are relatively wide. Generally speaking, the raw materials used in the existing plastic hollow blow molding can be suitable for low foaming hollow blow molding. Specifically, such as PVC, LDPE, HDPE, ABS, PP, PS, etc. Depending on the application, different plastics can also be used to form composite products, or the same plastic can be used, but the skin layer is a smooth pure plastic, and the middle layer is a foam.
The blowing agent for low-foaming hollow blow molding is usually an endothermic blowing agent with nucleation. Because this foaming agent absorbs heat when it decomposes, it can reduce the mold space by about 10%. Citric acid (bakingsoda), lg155cm3 two-body. However, this foaming agent is accompanied by a small amount of moisture generated during the reaction. Some moisture-sensitive plastics are not suitable for this blowing agent. In addition, such moisture-generating blowing agents can have a detrimental effect on unprotected hollow blow molding molds. Therefore, some companies use (, N2) (Polycarbonic acid) carbonate to generate 188cm2 of gas per 1g of carbon dioxide organic carbon, and no additional moisture is generated. In order to improve the cell structure and maintain the size of the microcells, a foaming inhibitor can be added to slow down the foaming speed or increase the foaming time (the foaming time is defined as the time required for the decomposition of the foaming agent to generate 60% of the gas). The blowing agent can often be premixed in the plastic for hollow blow molding, which eliminates the need for complex blowing agent metering, control and injection equipment.
Canadian ABC Company uses inert gas (nitrogen) as blowing agent for hollow blow molding. Their experiments show that chemical blowing agent results are unstable, and the quality of final low-foaming hollow blow molding parts is not easy to sacrifice. ABC Company uses a specially designed screw to quantitatively control the nitrogen injection. The position where nitrogen gas is injected into the plastic melt is located at the screw head, that is, near the machine head.
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