The coefficient of thermal expansion (αT) expresses the dimensional change of the polymer (volume, length, etc.)

 The coefficient of thermal expansion (αT) expresses the dimensional change of the polymer (volume, length, etc.) in response to change in temperature. Thermo- plastic polymers undergo a linear thermal expansion where the values of the linear coefficient of thermal expansion is shown in Table 1 shower sponge hanger. The expansion of polymers under heating depends on mostly intermolecular forces, because the bond length between atoms is virtually independent of temperature. Semi-crystalline polymers have higher coefficient of thermal expansion than amorphous polymers, varying from 4.1 to 13.0 (10−5/°C). Mould shrinkage of polymers can be calculated using BS EN ISO 294-4:1998, which indicates the volume contraction of polymers during the cooling step while processing (BS EN ISO 1998). This shrinkage is partly due to the difference of density of polymers from the melt state and the cooled, rigid state. Most of the moulded poly- mers experience shrinkage through the cooling phase at various rates depending on the polymer compositions, thermal properties, processing conditions and the geom- etry of the mould. 

Semi-crystalline polymers show higher mould shrinkage than amorphous polymers. This is because semi-crystalline polymers ecotools bath pouf, when cooled down, have part of their macromolecular chains re-arranged to form crystallite that is a well- organized structure, leading to less space needed for the same number of atoms. As demonstrated in Table 1, the mould shrinkage for semi-crystalline thermoplastic polymers varies from 0 filter net shower head.3 to 6.0%. Meanwhile, the mould shrinkage for amorphous thermoplastic polymers varies from 0.1 to 0.9%. The thermal conductivity, is determined by ASTM C177 and BS EN ISO 22007- 1:2017 and expressed in W/m/°C as given in Table 1 (BS EN ISO 2012), is a significant characteristic, when considering the use of a polymer for thermal insulation applications. 

However, most of the polymers demonstrated in Table 1 have the same thermal conductivity, varying from 0.15 to 0.75 W/m/°C, other than PET and PP where there is a significant difference. Mechanical properties Polymers tend to exhibit a wide variation of behavior in their mechanical properties ranging from hard to brittle to ductile which are defined under tensile, flexural and impact strength properties. Tensile properties include both tensile strength and tensile modulus, which are determined according to BS EN 527-1:2019 (Table 2) (British Standards Institutions 2019). It is crucial to understand the tensile properties of polymers to predict their performance under stress, especially when used in structural applications. Flexural properties include both flexural strength and flexural modulus which are determined according to BS EN 178:2019 (Table 2) (ISO 178 2010). Flexural properties of polymers demonstrate the polymers rigidity, stiffness, which denotes the ability of a polymer to bend. Moroever, Impact properties are determined according to BS EN ISO 180:2019 (2019). The impact strength can be related to the ultimate tensile strain of the different polymers. More flexible polymers tend to better withstand an impact than the more brittle, less flexible polymers.