Introduction to PVC Raw Materials

(I) Properties:

Polyvinyl chloride (PVC) is a non-toxic, odorless white powder with a density of 1.40 g/cm³; the density of PVC plastics containing plasticizers and fillers ranges from 1.15 to 2.00 g/cm³.

The mechanical properties of PVC depend on the polymer's molecular weight and the content of plasticizers and fillers. Higher molecular weight results in superior mechanical properties, cold resistance, and thermal stability, though molding and processing become more difficult; the opposite is true for lower molecular weights. The addition of plasticizers not only improves PVC's fluidity and lowers the plasticization temperature but also softens the material. Generally, if the plasticizer content exceeds 25 parts per 100 parts of PVC resin, the material becomes a soft plastic; elongation increases, while mechanical properties such as tensile strength, rigidity, and hardness decrease. Conversely, if the plasticizer content is less than 25 parts, the material is classified as a rigid or semi-rigid plastic with high mechanical strength. PVC is an amorphous polymer with a glass transition temperature of approximately 80°C; it begins to soften at this temperature, and its mechanical properties gradually deteriorate as the temperature rises. Clearly, the glass transition temperature represents the theoretical upper limit for PVC's service temperature. In practical applications, however, the long-term service temperature should not exceed 65°C. PVC has poor cold resistance; although its glass transition temperature is below -50°C, even soft PVC products become hard and brittle at low temperatures. Due to its high chlorine content (65%), PVC exhibits flame-retardant and self-extinguishing properties.

PVC has poor thermal stability; exposure to heat or sunlight causes discoloration—shifting from yellow, orange, and brown to black—accompanied by a decline in mechanical and chemical properties. PVC possesses excellent electrical properties, with electrical insulation capabilities comparable to those of hard rubber.

(II) Applications:

PVC has a wide range of applications. In terms of packaging materials, it can be used to produce packaging films, shrink films, composite films, and transparent sheets, as well as shipping containers, turnover boxes, and packaging coatings.