Plastics phenolic foams

Papa, J. and W.R. Proops, Phenolic foams. Plastic Foams Part II, p. 639-673, Marcel Dekker, New York (1973). 

THERMAL INSULATION FROM PHENOLIC FOAM PLASTICS FOR PIPELINES. 

Gas-filled plastics are polymer materials — disperse systems of the solid-gas type. They are usually divided into foam plastics (which contain mostly closed pores and cells) and porous plastics (which contain mostly open communicating pores). Depending on elasticity, gas-filled plastics are conventionally classified into rigid, semi-rigid, and elastic, categories. In principle, they can be synthesized on the basis of any polymer the most widely used materials are polystyrene, polyvinyl chloride, polyurethanes, polyethylene, polyepoxides, phenol- and carbamideformaldehyde resins, and, of course, certain organosilicon polymers. 

A variety of cellular plastics exists for use as thermal insulation as basic materials and products, or as thermal insulation systems in combination with other materials (see Foamed PLASTICS). Polystyrenes, polyisocyanurates (which include polyurethanes), and phenolics are most commonly available for general use, however, there is increasing use of other types including p olye thylene s, polyimides, melamines, and poly (vinyl chlorides) for specific applications. 

Foamed plastics (qv) were developed in Europe and the United States in the mid-to-late 1930s. In the mid-1940s, extruded foamed polystyrene (XEPS) was produced commercially, followed by polyurethanes and expanded (molded) polystyrene (EPS) which were manufactured from beads (1,2). In response to the requirement for more fire-resistant cellular plastics, polyisocyanurate foams and modified urethanes containing additives were developed in the late 1960s urea—formaldehyde, phenolic, and other foams were also used in Europe at this time. 

As of 1992, the first specialty platable plastic, acrylonitrile—butadiene—styrene (ABS) terpolymer (see Acrylonitrile polymers, abs resins), is used in over 90% of POP applications. Other platable plastics include poly(phenylene ether) (see Polyethers), nylon (see Polyamides), polysulfone (see Polymers containing sulfur), polypropylene, polycarbonate, phenolics (see Pphenolic resins), polycarbonate—ABS alloys, polyesters (qv), foamed polystyrene (see Styrene plastics), and other foamed plastics (qv). 

Syntactic foamed plastics (from the Greek ovvxa C, to put together) or spheroplastics are a special kind of gas filled polymeric material. They consist of a polymer matrix, called the binder, and a filler of hollow spherical particles, called microspheres, microcapsules, or microballoons, distributed within the binder. Expoxy and phenolic resins, polyesters, silicones, polyurethanes, and several other polymers and oligomers are used as binders, while the fillers have been made of glass, carbon, metal, ceramics, polymers, and resins. The foamed plastic is formed by the microcapsular method, i.e. the gas-filled particles are inserted into the polymer binder1,2). 

Fig. 8. Effect of molding pressure P on the stress in compression (crc) for a carbonized foamed plastic made from a compound binder (wood resin, furfuryl alcohol, maleic anhydride) and phenolic microspheres 381...

Cellular plastics, mainly polystyrene, are used for display and novelty pieces because of ease of fabrication, light weight, attractive appearance, and low cost. Phenolic foam is used in floral displays, where it can hold large amounts of water for long periods. Polyurethane and polystyrene foams are also used in other floral applications. Cellular poly(vinyl chloride) is used in toys and athletic goods. 

The distribution of some important technical characteristics of plastic foams, e.g. stretch, is closer to the Weibull than to the Gaussian distribution due to nonuniformity . Kozlov obtained the analytical expression for the coefficient of uniformity K2 for the Weibull distribution and used it to estimate the uniformity of phenolic foams. 

Mackowski, R., Majewski, S., Ostowski, K. Phenol-polystyrene plastic foams. Polim.-Tworz. Wielkoraasteczkowe 3, 107 (1978) (in Polish)... 

Shutov, F. A. On the use of electrical insulation from phenolic foams in high humidity media. All-Union Seminar on Plastic Foams, Leningrad 1975 (in Russian)... 

According to Thomas elastic polymers often produce open-cell foamed plastics, whereas rigid polymers generally form closed-cell materials. However, there are many exceptions to this rule, owing to the variety of blowing techniques. Closed-cell structures are more likely to be produced from polyurethanes, epoxy resins, silicones, poly(vinyl chloride), polystyrene, etc., whereas open-cell materials mainly result from phenolic and carbamide foamed plastics. 

The relation between the cell size and the strength of phenol-formaldehyde plastic foams shows that, for a mean cell diameter of less than 0.2-0.3 mm, their compressive strengths and Youngs moduli increase considerably as compared to foams with large cells, It has been found that for many flexible foam types the tensile strength and ultimate elongation are the higher the smaller the cells ss.ioo)... 

Colloid chemistry classifies materials having Sgp of tens or hundreds of square meters per gram as disperse systems. More important is that plastic foams exhibit properties of disperse systems. For example, the thermooxidative stability of phenolic foams was lowered by several dozen degrees as S,p was increased... 

Shutov, F. A. A Previously Unknown Morphological Type of Phenolic Foam Structure, in New Plastic Foam Technology, Vladimir VNllSS 1974, pp. 90 (Russ.)... 

Iwasaki, K., Chemistry and technology trends in phenolic foams, Japan Plastics 38 (2) 50-59 (1987). 

Iwasaki, K., Phenolic foams. Technical Handbook of Foamed Plastics, p. 169-196, Edited by K. Iwasaki, Joho-Kaihatsu Ltd., Japan (1989). 

Syntactic sphere core Syntactic cellular core plastics are also called RP syntactic foam or syntactic foam. An RP compound made by mixing hollow microspheres of glass, epoxy, phenolic, etc. into a fluid plastic with its additives and curing agents. It forms a moldable, curable, lightweight mass, as opposed to foamed plastics in which its cells are formed by gas bubbles, etc. 

Phenolic resin foam is an interesting material for the cellular insulation industry because of its high temperature resistance, fire resistance, and very low smoke generation [16]. The aqueous resole is crosslinked in the presence of a surfactant and a low boiling liquid, that volatizes during the increase ofviscosity or plasticity of the mixture. The surfectant is necessary to develop a uniform fine cellular foam stracture [1,6], Carbonization of phenolic foams yields carbon foams with an excellent thermal resistance, that are applied as high temperature insulation materials for the production of filters for corrosive agents and catalyst supports [1]. 

The largest markets for foamed plastics are in home insulation (polystyrene, polyurethane, phenol formaldehyde) and in packaging, including various disposable food and drink containers. Also refers to the occurrence of frothy mixture of air and a slurry that can reduce the effectiveness of the product, and cause sluggish hydraulic operation, air binding of oil pumps, and overflow of tanks or sumps. 

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