Thermal Coefficient of Linear Expansion

The coefficients of linear thermal expansion of polymers are higher than those of most rigid materials at ambient temperatures because of the supercooled-liquid nature of the polymeric state. This large coefficient is carried over directly to the cellular state. A variation of this property with density and temperature has been reported for polystyrene foams [54] and foams in general [8]. 

When cellular polymers are used in large structures, the coefficient of thermal expansion must be considered carefully because of its magnitude compared with that of most nonpolymeric structural materials. Many designs have been successful [55] when this fact has been taken into account. 

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The electronic configuration for an element s ground state (Table 4.1) is a shorthand representation giving the number of electrons (superscript) found in each of the allowed sublevels (s, p, d, f) above a noble gas core (indicated by brackets). In addition, values for the thermal conductivity, the electrical resistance, and the coefficient of linear thermal expansion are included. 

Tensile yield strength, 103 lb in-2 Thermal Burning rate, mm min Coefficient of linear thermal expansion, 10 °C 50-90 0.5-2.2 50-90 50-80 50-60 10-13 Self- extinguishing 40-55 46... 

Coefficient of linear thermal expansion, 10 °C Deflection temperature under 110-170 110-170 100-200 80-120 6.6 11-50 20-60... 

Thermal Expansion. Coefficients of linear thermal expansion and linear expansion during transformation are listed in Table 7. The expansion coefficient of a-plutonium is exceptionally high for a metal, whereas those of 5- and 5 -plutonium are negative. The net linear increase in heating a polycrystalline rod of plutonium from room temperature to just below the melting point is 5.5%. 

Thermal Expansion. The averaged value of the coefficient of linear thermal expansion of diamond over the range 20 to 100°C is 1.34 X 10 cm/cm/ C and 3.14 x 10 from 20 to 800°C. At room temperature the values for sihca glass and diamond ate 0.5 X 10 and 0.8 X 10 , respectively. The relatively low expansion combined with the low reactivity of diamonds, except for carbide formation, leads to some challenges in making strong bonds between diamond and other materials. 

Thermal expansion Glasses having coefficients of linear thermal expansion... 

Plastic products are often constrained from freely expanding or contracting by rigidly attaching them to another structure made of a material (plastic, metal, etc.) with a lower coefficient of linear thermal expansion. When such composite structures are heated, the plastic component is placed in a state of compression and may buckle, etc. When such composite structures are cooled, the plastic component is placed in a state of tension, which may cause the material to yield or crack. The precise level of stress in the plastic depends on the relative compliance of the component to which it is attached, and on assembly stress. 

To minimize the stresses induced by differential thermal expansion/contraction one must (1) employ fastening techniques that allow relative movement between the component parts of the composite structure, (2) minimize the difference in coefficient of linear thermal expansion between the materials... 

An influence on dimensions and tolerances involves the coefficient of linear thermal expansion or contraction. This CLTE value has to be determined at the product s operating temperature (Chapter 2, THERMAL EXPANSION AND CONTRACTION) Plas tics can provide all extremes in CLTEs. As an... 

When materials with different coefficients of linear thermal expansion (CLTE) are bolted, riveted, bonded, crimped, pressed, welded, or fastened together by any method that prevents relative movement between the products, there is the potential for thermal stress. Most plastics, such as the unfilled commodity TPs, may have ten times the expansion rates of many nonplastic materials. However there are plastics with practically no expansion. Details are reviewed in Chapter 2, THERMAL EXPANSION AND CONTRACTION. 

Like metals, plastics generally expand when heated and contract when cooled. Usually, for a given temperature change many TPs have a greater change than metals. The coefficient of linear thermal expansion (CLTE) is the ratio between the change of a... 

The coefficient of linear thermal expansion is almost constant, for most types of glass, for temperatures up to 400-600°C. The actual value depends on the chemical constitution of the glass. It then increases rapidly above a certain temperature, often called the... 

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