Polyvinyl chloride (PVC) is a polymer compound polymerized from vinyl chloride monomer. Due to the presence of chlorine atoms on the polymer backbone, its polymer structure is different from PE and it has a series of unique properties. Its main physicochemical data are as follows: 1. It appears as a white powder with a relative molecular weight of 36870~93760, a relative density of 1.35~1.45g/em (varying with different components), an apparent density of 0.40~0.65g/em ‘, a heat capacity of 1.045~1.463J/g ℃ (0~1000), a particle diameter of 60~150pm, and a refractive index of n=1544. 2. Thermal performance: The softening point of PVC is 75-85 ℃, and the flow temperature is around 175 ℃; When the temperature exceeds 100 ℃, PVC begins to degrade and release hydrogen chloride. The higher the temperature, the more severe the degradation, accompanied by a series of color changes (yellow → black). 3 Combustion performance: It can burn and degrade on the flame, releasing hydrogen chloride, carbon monoxide, benzene, etc., but it will extinguish itself when it leaves the flame. 4 Mechanical properties: UPVC is a hard and strong material, while SPVC belongs to a soft and tough material. The tensile strength range of PVC is 35-63MPa, and the tensile modulus range of UPVC is 2500-4200MPa. The magnitude of tensile modulus is related to the relative molecular weight of PVC resin, as well as the type and amount of admixture used. The bending performance of PVC is related to the relative molecular weight of the resin. For example, a material with a K value of 69 has a bending strength of 86.87 MPa and a bending modulus of 3134.36 MPa; The material with a K value of 72 has a bending strength of 79.30MPa and a bending modulus of 2995.77MPa. Adding reinforcing agents (such as short cut glass fibers) to PVC can achieve a bending strength of 107-138MP. Untoughened UPVC has poor impact toughness and high notch sensitivity. 5 Electrical properties: PVC has high density, electrical breakdown resistance, and aging resistance, and can be used as low-voltage cables and cable sheaths below 10000V. 6 Water absorption: PVC has a low water absorption rate, and when hard PVC is immersed in water for a long time, its water absorption rate is less than 0.5%; Immerse in water for 24 hours, with a water absorption rate of 0.05%. Select appropriate plasticizers for soft PVC, with a water absorption rate not exceeding 0.5%. PVC also has low fog permeability, breathability, and water vapor permeability. 7 Aging: Under the action of light and oxygen, PVC resin gradually decomposes (i.e. aging), and the surface of PVC material interacts with oxygen in the air, accelerating the degradation of high polymers by heat and ultraviolet light, decomposing into hydrogen chloride and forming carbonyl groups.
