Thermal properties heat-resistant plastics

Figure 5-6 and Tables 5-3 to 5-5 provide an introductory guide to the different thermal properties of plastics. Heat resistance properties of plastics retaining 50% of properties obtainable at room temperature with plastic exposure and testing at elevated temperatures are shown in Fig. 5-6 for the general family or group type. 

Fig. 6-14 specific modulus = modulus/density. Plastics include use of the heat-resistant TPs such as the polimides, polyamide-imide, and others. Table 6-21 provides data on the thermal properties of RPs. To date at least 80 wt % are glass fiber and about 60 wt% of those are polyester (TS) type RPs. 

Polysulfone Plastics. These plastics which were commercialized by Union Carbide are actually aromatic polyethers containing periodic sulfone groups which provide additional resonance stabilization. They have good mechanical properties, creep resistance, and dimensional stability but their outstanding quality is their high heat distortion temperature (345°F.) and resistance to thermal oxidative degradation. Limitations are difficult thermoplastic processability, amber color, and sensitivity to organic solvents. 

Alternatively, by preventing thermal degradation, heat stabilizers also have the effect of keeping die surfaces clean, increasing throughput, and maximizing film properties, such as tear and puncture resistance Cel-Span 306P is a 6% stabilizer concentrate offered for this purpose from Phoenix Plastics, for use... 

The glass transition temperature corresponds to the upper temperature limit of heat resistance of plastics. The lower hmit of thermal performance is a brittleness temperature (a temperature at which polymers can be fractured even at small deformations). This lower limit of performance temperature is about 10-170°C below the glass transition temperature. It depends on the type of polymer, its strength properties, and plasticizer type and content. 

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. 

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