The compound of PVC, PET and other plastic material

The PVC resin is generally processed in calendaring plant, and it needs blending, mixing and compounding by addition of suitable chemicals called as additives and fillers to make compound before processing in the calendering plant. Other then PVC resin ABS, PE, PP and Styrene are also used for calendering process.

PVC resin for rigid compounds made either by the suspension or bulk polymerization process is best in the 1.7 to2.0 relative viscosity range. Homopolymer grades are used alone and in combination with 2 to 10 percent acetate copolymer.

Different additives and stabilizers have different function in calendaring

Heat stabilizers are needed to PVC Film, when heated PVC naturally tends to degrade, first by yellowing then by turning dark brown and losing its physical properties. Many types of stabilizers are used, Metallic salts, mixed metal salts, organotins and tin mercaptides are the major categories. Stabilizers added to a formula between 0.1 and 5.0 percent to retard degradation by tying up hydrochloric acid (HCL) generated by the heat of processing.

Plasticizers are used to make PVC soft and flexible but thereby lower melt viscosity, modulus and transition temperature. Two common plasticizer groups are in use such as Dioctyl phthalate(DOP) and Epoxidized soyabean oil. There is no plasticizer in our PVC Sheet or PVC film.

Impact modifiers are used to absorb shock to improve impact resistance of PVC compound. The selection of ABS, MBS, Chlorinated polyethylene( CPE) or acrylic polymer chosen on the basis of their impact efficiency, clarity, weather ability and stress, whitening, as well as their processing characteristics. Process aids assist stabilization and increase the melt strength of the sheet during calendering and post processes such as thermoforming.

Lubricants are added to reduce the tendency of PVC to stick to the hot metal rolls of Calender. Lubricants are either external or internal depending on where they are most effective. Stearic acid or zinc and inorganic stearates and soaps are classified as internal lubricant. Paraffin and polyethylene waxes are external.

The resin is premixed and blended with stabilizers and other additives by using Ribbon blender or High speed mixture. The premixing is done up to 80°C for better absorption and soaking of the resin. After blending of the two compounds, it is fed to a fluxing machine. Fluxing is done under temperature at about 150°C.