PVC Additives (2)

3. FILLERS

Essentially fillers are added to formulations to reduce costs, although they may offer other advantages – such as opacity, resistance to blocking, reduced plate-out, improved dry blending. On the other side, fillers can reduce tensile and tear strength, reduce elongation, cause stress whitening, reduce low temperature perforance.

The most common fillers used with PVC are calcined clays, and water-ground and precipitated calcium carbonates of particle size around 3 micrometers. Other fillers are silicas and talcs.

4. LUBRICANTS

     These materials are of prime importance in PVC processing. They are decribed below.

      ⑴ Improve the internal flow characteristics of the compound.

      ⑵ Reduce the tendency for the compound to stick to the process machinery

      ⑶ Improve the surface smoothness of the finished product

      ⑷ Improve heat stability by lowering internal and/or external friction

          Examples of lubricants, with which you may be familiar, are stearic acid, calcium stearate, Wax E, polythylene AC 617.

5. PROCESSING AIDS

These may be regarded as low-melt viscosity, compatable solid plasticizers. They are added to lower processing temperatue, improve roll release on calenders, reduce plate-out, promote fusion.

They are usually added at concentration of 5.0%. The most widely used processing aids are acylic resins of which acrylic K 120N is an example.

6. OTHER ADDITIVES

     There are  several other addtives which we will list and comment on briefly.

⑴ Impact Modifiers: These are usd in rigid vinyls to improve impact resistance. These are usually acrylic or ABS polymers used at 10-15 phr levels. Examples are Kureha BTA 111, Blendex 301.

⑵ Light Stabilizers: for resistance to ultraviolet radiation. They are used in low concentrations 0.5-1.5 phr.

⑶ Flame Retardants: PVC is inherently self-extinguishing However, the plasticizers and additives are not. Therefore, flame retardants are added. The most widely known one is antimon tri-oxide.

⑷ Anti-Static Agents

⑸ Fungicides: Vinyzene BP-5

⑹ Foaming Agents: Chemicals that decompose at predetermined temperature to produce a certain volume of gas within the molten vinyl and thereby create foam.

⑺ Colorants: Both pigments and dyes can be used. However, dyes, which are soluble organic substances,are used sparingly de to their tendency toward migration and extract ability. Heat resistance of colorants must be carefully evaluated.

    In summary, we have seen that a vinyl compound consists of following components: PVC resin, plasticizer, heat stabilizer, lubricant, special additive, colorants.