久久激情5月丁香伊人_αv中文字幕女人乱码在线_成年人看的毛片在线观看_国产上床视频_精品亚洲国产黄片_三级日本黄页网站大全_国产美女精品网站_在线观看中文综合亚洲_男操女视频免费_亚洲中文字幕无码永久

POM is a kind of engineering plastics. Its Chinese name is polyoxymethylene, or saigang. Its chemical name is polyoxymethylene, while its English name is acid resin, polyoxymethylene, polyacetal, or POM for short. POM is divided into Homo POM and co POM.

Polyoxymethylene (acetal resin) is a crystalline thermoplastic resin.

POM consists of homopolymer composed of polyoxymethylene molecular chain composed of formaldehyde, and copolymer composed of trimer of aldehyde - trioxyheterocyclohexane and ethylene oxide. Steel is the representative of this kind of copolymer.

It mainly plays its role in the category of mechanical components such as gears and bearings. Polyoxymethylene is milky white and opaque, a high-density, high crystalline linear combination without side chains. It has outstanding comprehensive functions, excellent fatigue resistance and creep resistance, excellent electrical functions, etc.

　　1. Mechanical function: high elastic modulus, high hardness and stiffness. It can be used at -40~100 degrees for a long time. And it can withstand repeated impact for many times with little change in strength. The strength is little affected by temperature and temperature change. Polyoxymethylene (POM) is the kind of thermoplastic material with the most excellent fatigue resistance and small creep.

　　2. Thermal function: polyoxymethylene has a high thermal deformation temperature, 136 degrees for homopolymerization and 110 degrees for copolymerization. Copolyformaldehyde has higher continuous operating temperature. Copolyformaldehyde can be used continuously at 114 ℃ for 2000h, or at 138 ℃ for 1000h. The temperature that can be used in a short time can reach 160 ℃. According to American UL specification, the long-term heat-resistant temperature of polyoxymethylene is 85~105 ℃.

　　3. Chemical resistance: polyoxymethylene has no room temperature compatibilizer and has appropriate good corrosion resistance under high temperature conditions. And the size and mechanical strength change little. It has good compatibility and is easy to color.

　　4. Electrical function: its dielectric constant is not affected by temperature and humidity.

　　5. The disadvantages of the function of POM: relatively high density, opaque and acid resistant; Large forming shortening rate; Melting electricity is not very high; The heat drop point is appropriate and agile at higher temperatures. Thermal oxygen degradation also occurs in the presence of oxygen.

Forming process of POM

Polyoxymethylene can be processed by general thermoplastic forming methods, such as injection molding, extrusion, blow molding, spraying, etc.

Injection molding is the primary processing method.

Polyoxymethylene is usually injected by screw injection molding machine, and the injection amount of products should not exceed 75% of the maximum injection amount of the molding machine.

Generally, the injection molding process of polyoxymethylene can be referred to as follows: the barrel temperature is 175~195 ℃, the mold temperature is 45~75 ℃, the injection pressure should be set within the range of 69~118mpa, and the forming cycle can be taken as 20~30s.

The article comes from PVC Engineering Plastics:http://xrtsm.com.cn/