Thermoset plastics industry

Redwitz, W. B., State and Direction of Molding Process-Analysis of Thermoset Plastics, Industrial and Production Engineering, pp. 117-121, Feb. 1984. 

Reprinted from Haraguchi and Li [43], Copyright 2004, with permission of Japan Thermosetting Plastics Industry Association... 

Even though glass fibers today are not used very much in the rubber industry, they are still used extensively in the thermoset plastics industry, which includes the making of unsaturated polyester resin composites for boat hulls, car bodies, and so on. They are used extensively in what is called sheet molding compound (SMC) by the automotive industry. Approximately 80% of all glass fibers are used in this way. 

Other reactive phenolic resins are used in the adhesives industry and in the thermoset plastics industry. 

HMT is used as a methylene donor by the thermoset plastics industry as well as the adhesives industry. HMT is used as a feedstock to manufacture expiosives as well as fungicides. 

Also, about 8% is used in making unsaturated polyester used by the thermoset plastics industry. 

It is manufactured by heating dicyandiamide, H2N C(NH) NH CN, either alone or in the presence of ammonia or other alkalis, in various organic solvents. Melamine is an important material in the plastics industry. Condensed with melhanal and other substances it gives thermosetting resins that are remarkably stable to heat and light. U.S. production 1980 80 000 tonnes. 

Production and Sales and Captive Use of Thermosetting and Thermoplastic Resins, Society of the Plastics Industry, Committee on Resiu Statistics, Ernst and... 

The term amino resin is usually appHed to the broad class of materials regardless of appHcation, whereas the term aminoplast or sometimes amino plastic is more commonly appHed to thermosetting molding compounds based on amino resins. Amino plastics and resins have been in use since the 1920s. Compared to other segments of the plastics industry, they are mature products, and their growth rate is only about half of that of the plastics industry as a whole. They account for about 3% of the United States plastics and resins production. 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

Thermosetting unsaturated polyester resins constitute the most common fiber-reinforced composite matrix today. According to the Committee on Resin Statistics of the Society of Plastics Industry (SPl), 454,000 t of unsaturated polyester were used in fiber-reinforced plastics in 1990. These materials are popular because of thek low price, ease of use, and excellent mechanical and chemical resistance properties. Over 227 t of phenoHc resins were used in fiber-reinforced plastics in 1990 (1 3). PhenoHc resins (qv) are used when thek inherent flame retardance, high temperature resistance, or low cost overcome the problems of processing difficulties and lower mechanical properties. 

Thermosetting and Thermoplastic Resins, year-end monthly or annual statistical reports, the Committee on Resin Statistics of the Society of the Plastics Industry, Inc., Washington, D.C., through 1991. 

The largest user of phenol in the form of thermosetting resins is the plastics industry. Phenol is also used as a solvent and in the manufacture of intermediates for pesticides, pharmaceuticals, and dyestuffs. Styrene is used in the manufacture of synthetic rubber and polystyrene resins. Phthalic anhydride is used in the manufacture of DMT, alkyd resins, and plasticizers such as phthalates. Maleic anhydride is used in the manufacture of polyesters and, to some extent, for alkyd resins. Minor uses include the manufacture of malathion and soil conditioners. Nitrobenzene is used in the manufacture of aniline, benzidine, and dyestuffs and as a solvent in polishes. Aniline is used in the manufacture of dyes, including azo dyes, and rubber chemicals such as vulcanization accelerators and antioxidants. 

In recent years there has been some concern in the thermosetting material industry that usage of these materials is on the decline. Certainly the total market for thermoset compounds has decreased in Western Europe. This has happened for a number of reasons. One is the image that thermosets tend to have as old-fashioned materials with outdated, slow production methods. Other reasons include the arrival of high temperature engineering plastics... 

Worldwide the term preferred is plastics. The fact is that (1) this industry identifies itself as a plastics industry, (2) practically all people worldwide use the term plastics, (3) practically all materials, products, exhibition shows, technical meetings, advertising, etc. use the term plastics, and (4) as it is repeatedly said, this is a World of Plastics. As shown in this book there are terms that overlap and also interfere with each other. A major example is stating that thermoplastics (TPs) are cured during processing cure occurs only with thermoset plas-... 

For over a century plastics have successfully competed with other materials in old and new applications providing cost-performance advantages, etc. In fact within the plastic industry there is extensive competition where one plastic competes with another plastic. Examples include many such as thermoplastic elastomers vs. thermoset... 

Large quantities are used as a raw material in the chemical process industry, especially for urea across C02 reaction with NH3 and later dehydration of the formed carbamate. Urea is the product most used as agricultural fertiliser. It is used in feed for ruminants, as carbon cellulose explosives stabiliser in the manufacture of resins and also for thermosetting plastic products, among others. 

The solidified material, which he called Bakelite, was impervious to harsh acids or bases, wide temperature extremes, and just about any solvent. Bakelite quickly replaced celluloid as a molding medium, finding a wide variety of uses for several decades. It wasn t until the 1930s that alternative thermoset polymers (Section 12.4) began to challenge Bakelite s dominance in the evolving plastics industry. 

RPs that combine two different materials (plastic matrix and reinforcement) are a separate major and important segment in the plastic industry. They are also called plastic composites and composites. There are also self-reinforcing plastics such as liquid crystal polymers (Chapter 1) and others.301 It is a fact that RPs have not come near to realizing their great potential in a multitude of applications usually due to cost limitations that particularly involves the use of expensive fiber reinforcements (carbon, graphite, silica, etc.).1 Information on thermoplastic and thermoset plastic RPs are reviewed in Chapter 15. 

Thermoset plastics have also been pyrolysed with a view to obtain chemicals for recycling into the petrochemical industry. Pyrolysis of a polyester/styrene copolymer resin composite produced a wax which consisted of 96 wt% of phthalic anhydride and an oil composed of 26 wt% styrene. The phthalic anhydride is used as a modifying agent in polyester resin manufacture and can also be used as a cross-linking agent for epoxy resins. Phthalic anhydride is a characteristic early degradation product of unsaturated thermoset polyesters derived from orf/io-phthalic acid [56, 57]. Kaminsky et al. [9] investigated the pyrolysis of polyester at 768°C in a fiuidized-bed reactor and reported 18.1 wt% conversion to benzene. 

Air and water pollution are sufficiently managed according to the law and ordinance, as in other liquefaction processes. In addition, this process can be applied to treat waste plastics from households, from industry and from agriculture, since the composition of plastic containers and packaging is well known (i.e. they contain PVC, PVDC, and ABS, and sometimes thermosetting plastics). 

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