Improve mechanical properties, processing, durability.

• Fillers:
  Added to Improve tensile strength & abrasion resistance, toughness & decrease cost.
  Examples: Carbon black, Silica gel, Wood flour, Glass, Limestone, Talc.
• Plasticizers:
  Added to reduce glass transition temperature T_g below room temperature. Presence of plasticizer transforms brittle polymer to a ductile one. Commonly added to PVC.
• Stabilizers:
  Antioxidants, UV protection
• Lubricants:
  Added to allow easier processing polymer “slides” through dies easier (sodium stearate).
• Colorants:
  Dyes and pigments
• Flame Retardants:
  Substances Containing Chlorine, Fluorine and Boron.