Rotary Molding Industry Development Overview

Rotary molding originated in Britain in 1934. Since the 1940s, European polyvinyl chloride pastes have been used to produce toys such as plastic balls by rotomolding molding. In the 1950s, a polyethylene rotomolding process using low-density polyethylene powdered resins was developed to produce industrial products such as polyethylene storage tanks and large-sized pipes, which greatly promoted the development of rotomoulding processes. Since then, nylon, polycarbonate, ABS and other plastics have also been molded by rotomolding.

In the 1960s, due to the continuous improvement of resin properties and rotomoulding equipment, the rotational molding process has been rapidly developed. A number of rotomolding special plastics have been developed abroad, such as PEP-320 and RaychemsFlamolin 771, etc., developed by Union Carbide. PEP-320 is a low density polyethylene that combines the good flow molding properties of low density polyethylene resins with the low temperature impact toughness, chemical resistance, and stress crack resistance of high density polyethylene resins;

RaychemsF1amo1in711 is a cross-linked polyethylene resin for rotomolding that is self-extinguishing in addition to being crosslinkable. Philip's famous rotomolded grade crosslinked polyethylene resin MarlexCl-100 was also developed during this time.

In order to meet the needs of preparing large-scale rotomoulded products, many machines that can effectively use the floor space and heat energy and perform rotomolding molding of large-scale plastic parts have also been developed in the late 1960s. By 1970, more than half of the rotomoulding machines in commercial rotomoulding machines had a rotary diameter in excess of 1.75m. In addition, the machine's control level has also been improved to varying degrees. For example, the three-arm rotomolding machine McNeil Auronismodel 3000-200 can control the heating and cooling cycles of each arm separately, so that simultaneously rotomoulding the products of different sizes and different materials can be achieved. With a diameter of 5m, each arm can bear a total weight of about 13500N for the mold and the resin; a jacketed rotomolding machine with a good heat transfer effect and a small footprint is also designed and manufactured during this time.

In the early 1970s, more than 50 companies in the UK had been involved in the production of rotomolded products, with more than 70 rotomoulded thermoplastics manufacturers; more than 20 companies in the European continent were involved in rotational molding, including Germany and France. Companies in Italy, Switzerland, Norway, Austria, Denmark, etc. The United Kingdom has been able to provide rotomoulding machines capable of producing containers with a capacity of 18,000L. The Netherlands has produced large cylindrical storage tanks with a diameter of 2.1m and a length of 4.8m. The storage tank is 540kg and its wall thickness is 25mm. At that time, the total amount of rotomolding products in Europe had reached more than 15,000 tons, of which only 7,000 tons were in the United Kingdom alone.

In the early 1970s, there were more than 500 companies in the United States that were involved in the production of rotomolded products. With more than 500 rotomoulding machines, the capacity of rotomoulding containers has exceeded 10,000 liters (2,400 gallons); the largest rotomoulding machine can produce Plastic parts up to 4.6×4.6×2.1m. Rotational molding has undergone three major developments in the 1950s, the 1970s, the 1980s and the early 1990s. It has been quite developed in Western Europe and North America, forming a rotomolding raw material professional company to produce and formulate, rotomolding machinery and equipment. The professional company manufactures and sells an independent industrial system consisting of rotomolding technology, scientific research and education, and a large number of rotomolding factories. All thermoplastic resins and some thermosetting resins can be used to produce products as small as table tennis, up to 85 meters in volume, in various shapes, as a whole, seamless, once formed. Rotational molding industry has become a large-scale plastic molding industry. By 1992, the resin used for rotational molding in the world accounted for 8-9% of the total resin consumption in the world. There were more than 5,000 kinds of rotomoulded products registered in the United States Rotational Molding Association. There are currently about 1,000 rotomoulding enterprises in the world. The International Rotational Molding Association (ARM) based in the United States, as the main international organization in the rotomolding industry, has members in 58 countries, including rotomolding product manufacturers, raw material suppliers, and mold design manufacturers.

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