The molecular structure of PTFE is similar to PE, all H atoms in PE are replaced by F atoms to become PTFE, because the bond energy of C-F bond is higher than C-H bond, the electron cloud of fluorine atoms shield the C-C bond more than hydrogen atoms; at the same time, the nucleus of fluorine atoms has a stronger binding effect on its out-of-nuclear electrons and bonding electron cloud, and the fluorine atoms have a low rate of symmetric distribution, which Make the molecularity smaller.
Therefore, compared with PE, PTFE has significantly improved performance, atomic distribution symmetry, making the molecularity smaller, so PTFE is a polymer species with lower surface energy, better chemical resistance, melting temperature and relative density is one times greater than PE, good weather resistance, high insulation, dielectric constant and loss factor is smaller.
The mechanical properties of PTFE are influenced by many factors such as preforming pressure, sintering temperature and time, cooling rate, porosity and degree of crystallization. Some properties like low coefficient of friction, flexibility at low temperatures, and stability at high temperatures are less related to processing conditions. Molding and sintering conditions mainly affect bending fatigue life, permeability, stiffness, elasticity, and impact strength.
When PTFE is stretched, yielding occurs at higher deformations, and yield deformation decreases with increasing temperature. The modulus of elasticity, which is the slope of the linear portion of the stress-strain curve, increases significantly with decreasing temperature. the tensile and compressive strengths of PTFE increase with decreasing temperature. As the temperature increases, the stress at the same deformation decreases. Hardness is an important indicator of the degree of hardness and softness of the material, with different hardness test methods, hardness values vary, such as the Rockwell hardness of PTFE is 58; Shore hardness is 98, while the D standard value of 50-65. PTFE can be filled with fillers to improve the hardness of 10%-15%, related to the filler content. Therefore, it is used in a large number of oil-free lubrication occasions, especially in the sliding speed is low, the pressure is not high (35kPa) under the working conditions is suitable.
Aqueous ptfe dispersion have outstanding heat, cold and friction resistance. It has excellent electrical insulation, non-stick, non-absorbent and non-combustible properties. It is mainly used for the coating of kitchenware and industrial applications such as spinning, glass cloth impregnation and other processed products. It is also widely used as an insulating layer for electrical appliances, electronics, instruments, medical devices, batteries, power and signal lines.
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