Vacuum Forming materials are divided into PVC, PP, PS, PET, etc., which are industrial products. Different varieties have different softening and melting temperatures and densities.

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Simple identification method for plastic series -

Therefore, it is best to mark the material type on plastic products. China has formulated GB/T16288-1996 "Plastic Packaging Product Recycling Mark" with reference to the material type marking proposed and implemented by the American Plastics Association (SPE). Although the above marking method can be used to facilitate sorting, there are still many unmarked plastic products in China, which brings difficulties to sorting. In order to separate different types of plastics for classified recycling, we must first master the knowledge of identifying different plastics. The following introduces a simple identification method for plastics:

Appearance identification of plastics

By observing the appearance of plastics, we can preliminarily identify the major categories of plastic products: thermoplastics, thermosetting plastics or elastomers. Generally, thermoplastics are divided into two categories: crystalline and amorphous. Crystalline plastics are translucent, milky or opaque in appearance, and are transparent only in the film state, with hardness ranging from soft to horny. Amorphous plastics are generally colorless, completely transparent without additives, and have a hardness ranging from harder than horny rubber (plasticizers and other additives are often added at this time). Thermosetting plastics usually contain fillers and are not transparent. If they do not contain fillers, they are transparent. Elastomers have a rubbery feel and a certain elongation.

The heating characteristics of the above three types of plastics are also different, and can be identified by the heating method. Thermoplastic plastics soften when heated, are easy to melt, and become transparent when melted. Wires can often be drawn from the melt, and are usually easy to heat seal. Thermosetting plastics are heated to the point where the material chemically decomposes, maintaining their original hardness without softening, and their dimensions are relatively stable, and carbonizing at the decomposition temperature. When an elastomer is heated, it does not flow until the chemical decomposition temperature, and the material decomposes and carbonizes at the decomposition temperature.

The softening or melting temperature range of commonly used thermoplastics is shown in the table

Softening or melting range of plastic varieties/буC Softening or melting range of plastic varieties/бц

Polyvinyl acetate 35бл 85 Polyoxymethylene 165бл185

Polystyrene 70бл115 Polypropylene 160бл170

Polyvinyl chloride 75бл90 Nylon 12 170бл180

Polyethylene

Density 0.92/cm3 110 Nylon 11 180бл190

Density 0.94/cm3 About 120 Polychlorotrifluoroethylene 200бл220

Density 0.96/cm3 About 130 Nylon 610 210бл 220

Poly-1-butene 125бл 135 Nylon 6 215бл225

Polyvinylidene chloride 115бл 140 (softened) Polycarbonate 220бл 230

Organic glass 126бл 160 Poly-4-methylpentene-1 240

Cellulose acetate 125бл175 Nylon 66 250бл260

Polyacrylonitrile 130бл 150 (softened) Polyethylene terephthalate 250бл260

Density identification method

Plastics of different varieties have different densities. The density determination method can be used to identify plastics, but the foamed products should be separated at this time, because the density of foamed plastics is not the real density of the material. In actual industry, plastics are also sorted by different densities. The density of commonly used plastics is shown in the following table: Density/(g/cm3) Material Density/(g/cm3) Material 0.8 Silicone rubber cavity (can be filled with silica to 1.25) 1.19~1.35 Plasticized polyvinyl chloride (contains about 40% plasticizer) 0.83 Polymethylpentene 1.20~1.22 Polycarbonate (bisphenol A type) 0.85~0.91 Polypropylene 1.20~1.26 Cross-linked polyurethane 0.89~0.93 High pressure (low density) polyethylene 1.26~1.28 Phenol formaldehyde resin (unfilled) 0.91~0.92 1-polybutene 1.26~1.31 Polyvinyl alcohol 0.9~0.93 Polyisobutylene 1.25~1.35 Cellulose acetate

0.92бл1.00 Natural rubber 1.30бл1.41 Phenol formaldehyde resin (filled with organic materials: paper, fabric)

0.92бл0.98 Low-pressure (high-density) polyethylene 1.30бл1.40 Polyvinyl fluoride

1.01бл1.04 Nylon 12 1.34бл1.40 Celluloid

1.03бл1.05 Nylon 11 1.38бл1.41 Polyethylene terephthalate

1.04бл1.06 Acrylonitrile-butadiene-styrene copolymer (ABS) 1.38бл1.50 Rigid PVC

1.04бл1.08 Polystyrene 1.41бл1.43 Polyoxymethylene (polyoxymethylene)

1.05бл1.07 Polyphenylene ether 1.47бл1.52 Urea-melamine resin (with organic filler) 1.06бл1.10 Styrene-acrylonitrile copolymer 1.47бл1.55 Chlorinated polyvinyl chloride 1.07бл1.09 Nylon 610 1.50бл2.00 Phenolic plastics and amino plastics (with inorganic filler) 1.12бл1.15 Nylon 6 1.70бл1.80 Polyvinylidene fluoride 1.13бл1.16 Nylon 66 1.80бл2.30 Polyester and epoxy resin (with glass fiber) 1.10бл1.40 Epoxy resin, unsaturated polyester resin 1.86бл1.88 Polyvinylidene chloride 1.14бл1.17 Polyacrylonitrile 2.10бл2.20 Polytrifluoroethylene

1.15бл1.25 Cellulose acetobutyrate 2.10бл2.30 Polytetrafluoroethylene

1.161.20 Polymethyl methacrylate

1.17бл1.20 Polyvinyl acetate

1.18бл1.24 Cellulose propionate

Solutions commonly used to identify the density of plastics

Type of solution Density (25бц)/(g/cm3) Preparation method Type of plastic (product)

Float in solution Sink in solution

Water 1 Polyethylene, polypropylene Polyvinyl chloride, polystyrene

Saturated salt solution 1.19 74ml water and 26g salt Polystyrene, ABS Polyvinyl chloride

58-4% alcohol solution 0.91 100ml water and 140ml 95% alcohol Polypropylene Polyethylene 55-4 alcohol solution 0.925 100ml water and 124ml 95% alcohol High pressure polyethylene Low pressure polyethylene

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