Thermally stable plastic

In 1954 Gow Chemical Company purchased the Macallum patents because they made p-dichlorobenzene and had an interest in thermally stable plastics. (2) The Dow workers made a detailed stu< of the Macallum polymerization system, (l) and the structure of the polymers. (8) They found that the process would be... 

The thermally stable plastics are correspondingly classified in two classes heat stable and high-temperature-stable plastics. The emphasis in heat stable plastics is on the resistance to mechanical deformation at higher temperatures. Such plastics can be applied at temperatures up to 250-300°C, whereas conventional plastics can only be used up to about 100°C. Many engineering plastics belong to the heat stable plastics (see also Section 36.4). Thermal dimensional stabilities of at least 180°C, tensile strengths of at least 45 MPa and flexural moduli of at least 2 200 MPa at this temperature with retention of at least 50% of the mechanical property values at 115° C in air for at least 11.5 years (100 000 h) are required of these polymers. In addition, the polymers should be resistant to as many chemicals as possible at temperatures of 80°C and higher. 

See also electronic plastic thermal conductivity thermally stable plastic. 

Nonflammable polymers, by definition, possess significant fire-resistant properties because of their chemical structure or due to some additives. All thermally stable plastics belong to the broad nonflammable plastic group, but a number of them within this group possess performance characteristics that are different. Halogenated polymers such as PVC, fluorinated polymers or those, which contain flame retardant, are classed as fire resistant. In fact, every plastic can be improved by the addition of fireproofing agents [114-118]. 

Heat-sensitive plastics include PVC, POM, PBT, PET, CA, CAB, CP, polyfluoroolefins, PPA, polyether ether ketone (PEEK) (at processing temperature) and all plastics with flame retardants while thermally stable plastics include PE, PP, PMMA, PC, PS and others. 

The time spent by heat-sensitive plastics in the cylinder and HR is 5-10 minutes, but may be as much as 30-60 minutes for thermally stable plastics. The graph shown in Figure 3.12 shows that this time depends to a large extent on the temperature. 

When thermally sensitive plastics are being processed, e.g., PBT, PET, POM, and nozzles with an insulation chamber are being used, the HR system may first be filled with a thermally stable plastic, e.g., PA 66. This prevents a distribution of melt which hangs in the chamber or creates what is known as an insulating layer. 

When molding thermally sensitive material, it is necessary to replace the volume of the annular gap as far as possible with a cap made of thermally stable plastic material (e.g. PEI or PEEK, Figure 1.42). The volume of the ante-chamber itself should be kept as small as possible. 

Thermally stable plastics were more recently developed which enable adhesive bonds that withstand temperatures up to 350 °C. Concurrent development of new bonding technologies (e.g. sandwich construction) now makes it possible to adhere a multitude of various materials to one another. As such, classical connection meth-... 

Plasticizer esters are relatively iaert, thermally stable Hquids with high flash points and low volatihty. Consequently they can be stored safely ia mild steel storage tanks or dmms for extended periods of time. Exposure to high temperatures for extended periods, as encountered ia dmms ia hot climates, is not recommended since it may lead to a deterioration in product quaUty with respect to color, odor, and electrical resistance. 

Operating conditions are important determinants of the choice of filter media and sealant used in the cartridges. Some filter media, such as cellulose paper filters, are useful only at relatively low temperatures of 95 to 150"C (200 to 300°F). For high-temperature flue gas streams, more thermally stable filter media, such as nonwoven polyester, polypropylene, or Nomex, must be used. A variety of commercially available sealants such as polyurethane plastic and epoxy will allow fabric operating temperatures up tol50°C (300°F). Selected sealants such as heat cured Plasitcol will withstand operating temperatures up to 200°C (400°F). 

Silicone materials play an active role in enabling some of the analytical techniques. Thus, surface-modified silicone was described as a substrate in plastic microarray devices for DNA analysis.638 Thermally stable aryl-substituted siloxanes are often used as stationary phases in capillary-gas chromatography.639 The use of silicone membranes in various separation techniques was already mentioned. 

P.Y.116 is also used in plastics. In plasticized PVC, it shows little tendency to bleed and is thermally stable up to 180°C. The lightfastness of transparent PVC colorations (0.1% pigment) equals step 7-8 in 1/3 SD (with 5% TiOz), it corresponds to step 6 on the Blue Scale. Insufficient heat resistance limits the application of P.Y.116 in polyolefins, polystyrene, and other polymers which are processed at high temperature. 

Moreover, y-P.V.19 is also found in a variety of other media, such as powder coatings and cast resins. This includes systems based on unsaturated polyester resins whose hardening is not affected by the pigment. The list of application media includes plastics which are processed at very high temperature (such as polycarbonates), in which the pigment is thermally stable up to 320°C. PUR foams and... 

P.R.168 is found to a lesser extent in printing inks and plastics. The printing ink industry utilizes P.R.168 to produce special-purpose printing inks, which may be applied to substrates such as posters or metal deco prints. The pigment demonstrates equally excellent fastness in these materials. 1/1 SD systems equal step 8 on the Blue Scale for lightfastness, while 1/3 to 1/25 SD formulations match step 7. The prints are resistant to common organic solvents and chemicals. The pigment is thermally stable up to 220°C for 10 minutes, and its prints may safely be sterilized. 

SD HDPE systems (1% TiOz) are thermally stable up to 250°C, while 1/25 SD specimens withstand 280°C. P.Y.182 does not affect the shrinkage of the plastic. 0.37% pigment is needed to formulate a 1/3 SD HDPE sample. Combining P.Y.182 with nickel stabilizers in polypropylene is to be avoided. The pigment dissolves in polystyrene as the temperature reaches 200°C, a process which is accompanied by considerable color change. P.Y.182 is also an unsuitable candidate for ABS. 

Pentaerythritol tetranitrate (PETN) is a colorless crystalline solid that is very sensitive to initiation by a primary explosive. It is a powerful secondary explosive that has a great shattering effect. It is used in commercial blasting caps, detonation cords, and boosters. PETN is not used in its pure form because it is too sensitive to friction and impact. It is usually mixed with plasticized nitrocellulose or with synthetic rubbers to form PBXs. The most common form of explosive composition containing PETN is Pentolite, a mixture of 20 to 50% PETN and TNT. PETN can be incorporated into gelatinous industrial explosives. The military has in most cases replaced PETN with RDX because RDX is more thermally stable and has a longer shelf life. PETN is insoluble in water, sparingly soluble in alcohol, ether, and benzene, and soluble in acetone and methyl acetate. 

Mixed xylenes are used as an octane improver in gasoline and for commercial solvents, particularly in industrial cleaning operations. By far, most of the commercial activity is with the individual isomers. Para-xylene, the most important, is principally used in the manufacture of terephthalic acid and dimethyl terephthalate en route to polyester plastics and fibers (Dacron, films such as Mylar, and fabricated products such as PET plastic bottles). Ortho-xylene is used to make phthalic anhydride, which in turn is used to make polyester, alkyd resins, and PVC plasticizers. Meta-xylene is used to a limited extent to make isophthahc acid, a monomer used in making thermally stable polyimide, polyester, and alkyd resins. 

These polymers, which are commercially available, are not thermally stable and decompose to produce the monomer when heated. Copolymers of alpha methylstyrene with methyl methacrylate or styrene are transparent plastics with heat deflection temperatures greater than that of PS. 

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