The Materials And Performance Of Helmets
1 commonly used materials and performance of helmets
The commonly used materials for the production of helmets are: ABS material, HDPE material, PC material, FRP material, etc.; the internal structure of the cap is mainly produced by LDPE, PA and other materials; the top lining is produced by HDPE or sponge composite material, sweat absorption The belt is made of PVC film, acrylic or terry sponge composite material, and the acrylic and polyester tapes are used as corresponding cap connectors. Several major hard hat products currently produced in various countries around the world are briefly described as follows: (According to international practice, classified by hard hat material)
The full name of ABS plastic is acrylonitrile-butadiene-styrene resin, which is the abbreviation of English Acrylonitrile Butadiene Styrene. This engineering plastic has heat resistance, high surface hardness, dimensional stability and chemical resistance. At the same time, the 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 the production of helmets generally use ultra-high impact type ABS materials, otherwise the impact test is unqualified. This material, except for a small number of countries such as North America, does not use this material to produce helmets, which are widely used in other countries.
HDPE plastic 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, the compressive strength of this material is poor. If the internal structure of the cap and the design of the product wall thickness are not improved, the lateral pressure test is often unqualified. Therefore, the hard hat cap of this material must be strengthened against the lateral pressure design, otherwise it will be in Europe, Australia. It is difficult to pass the Japanese and Chinese standards. Because North American standards do not have side pressure, HDPE helmets are widely used in the Americas, while in Europe, Japan and South Korea, HDPE is basically not used to produce helmets.
3. PC helmet
PC plastic is polycarbonate (Polycarbonate), which is hard and tough, has high impact resistance, high dimensional stability, good electrical insulation and high temperature resistance. Due to the high price of materials, this material is rarely used in other countries except Japan. Of course, because some of the special materials in the PC have good temperature resistance, many metal smelting industries require such high temperature PC helmets.
The FRP material 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. It has helmets of this kind in all countries of the world.
5. Other helmets
In addition to the above four kinds of materials for the production of helmets, there are also the following types of helmets, mainly produced in China, which are hardly seen in foreign helmet manufacturers and exhibitions.
(1) Tape helmet: Use rubber and canvas to heat the tape into a hard hat.
(2) Cold-proof helmet: It is made of plastic inner shell and the outer shell is made of sheep shearing and plush. It is suitable for winter protection.
(3) Bamboo hard hat: A hard hat made of bamboo stalks.
(4) Rattan Wicker Hard Hat: This type of hard hat is a hard hat woven with rattan or wicker material, but the flame retardant effect is extremely poor.
(5) Aluminum helmets: Very few manufacturers use aluminum die-casting to produce aluminum helmets.