Common plastic materials and performance of helmets
There are many materials for the production of helmets. At present, common materials for producing helmet caps at home and abroad are: ABS, HDPE, PC, FRP, etc.; internal structure of caps, mainly produced by LDPE, PA and other materials; top lining is made of HDPE or sponge composite nylon. Sweat absorbing tape is made of PVC film, acrylic fiber or terry cloth sponge composite, acrylic fiber and polyester tape are used as corresponding cap connectors. Several major helmet products currently produced in countries around the world are briefly described as follows (According to international practice, classified by hard hat material):
1. ABS helmet
Full name of ABS is acrylonitrile-butadiene-styrene resin, which is abbreviation of Acrylonitrile Butadiene Styrene. This engineering plastic has heat resistance, high surface hardness, dimensional stability and chemical resistance. At the same time, electrical insulation performance is good, rarely affected by temperature and humidity, and remains constant over a wide range of frequency variations. In addition, its chemical properties are also very good, with little effect on water, inorganic salts, alkalis and acids.
ABS materials have good impact strength and do not drop rapidly at low temperatures. Of course, materials suitable for production of helmets generally use ultra-high impact type ABS materials, otherwise impact test is unqualified. This material, except for a small number of countries such as North America, does not be used to produce helmets, which are widely used in other countries.
2. HDPE helmet
HDPE is High Density Polyethylene. This material has high surface hardness and good heat resistance, electrical insulation and dimensional stability. It is widely used in helmet production. However, compressive strength of this material is poor. If internal structure of cap and design of product wall thickness are not improved, lateral pressure test is often unqualified, so helmet cap of this material must be strengthened with anti-side pressure design, otherwise it will be difficult to pass in European, Australia, Japanese and Chinese standards. Because North American standards do not have side pressure, HDPE helmets are widely used in Americas, while in Japan, South Korea and other countries, HDPE is basically not used to produce helmets.
3. PC helmet
PC is polycarbonate (Polycarbonate), which is hard and tough, has high impact resistance, high dimensional stability, good electrical insulation and high temperature resistance. Due to high price of materials, this material is rarely used in other countries except Japan. Of course, because of high temperature resistance of some special materials in PCs, many metal smelting industries require such high temperature PC helmets.
4. FRP helmet
FRP is glass fiber reinforced plastic, referred to as Fiberglass Reinforced Plastics. This material has high fiber strength, excellent heat resistance and electrical insulation properties, and has excellent acid and water resistance, flame retardancy and small deformation. All countries in the world have helmets of this material. However, since composite material is a thermosetting resin, a large amount of waste, scraps is created in production process and garbage recycling after use of helmet is difficult to handle, which cause environmental pollution and fail to meet low carbon economy. Therefore, developed countries in Europe and United States are gradually reducing production of such materials.
Mold steel for making plastic helmet molds
Helmet mold materials used to produce helmets are mainly steel, and some are also made of non-ferrous or non-metallic materials. Thirty years ago, due to lack of scientific and technological development, hard hats and accessory molds were generally produced using carbon tools steel materials such as 45# steel and 40Cr at home and abroad. However, products produced using these steels have shortcomings such as poor brightness, low dimensional accuracy, and mold life. With the development of science and technology, some new steel products with high hardness performance, good sliding wear performance, and strong corrosion resistance have emerged, which has greatly improved the precision and smoothness of helmet products, improved the entire industrial level. At present, Japan Green Safety, American JACKSON, and other safety products companies generally use high-hardness, high-toughness alloy tool steels such as 718, 2738, 2316 to produce helmet mold, which make products more smooth and precise, extend the service life of mold to reach more than 2 million times. In recent years, domestic helmet mold manufacturers, whether they are self-produced or commissioned mold manufacturers in China to make helmet mold, also gradually use P20, 718 steel from original medium carbon steel. Most helmet mold manufacturers requiring high quality use standard mold bases to manufacture molds, which effectively ensure precision, high efficiency, and long life of the mold.