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What is PVC
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- Category: Literatur
- Published on Tuesday, 22 January 2013 14:47
- Written by Administrator
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57% of the PVC molecules is of mineral origin (NaCl)
VINYL COMPOUNDING
Vinyl resin, which is inherently hard and brittle, must be mixed with other additives to make a compound before can be processed into useful products. Pure poly-chloroethene is unstable when exposed to visible light or UV. In order to modify this disadvantage and make it suitable for different applications antioxidants are added. Some other additives comprise:
Additives Properties achieved
Anti-oxidants & other stabilizers Slow down the rate at which the polymer will be degraded by oxygen, heat, visible light or UV radiation
Compatibilizers: enable PVC to be mixed with other plastics and helps plastic recycling
Flame retardants: reduce flammability of plastic
Pigments: to colour the plastic
Plasticisers: to produce flexible and manageable plastic
Impact modifiers: to absorb shock without damage(impact resistant)
Fillers: inexpensive, inert materials that simply add bulk to the plastic
The initial step in producing vinyl compounds is called dry blending. Dry blending takes place in closed vessel, where dry and liquid additives are mixed together by blades or paddles. Because the resin particles are porous, the liquid additives are absorbed relatively easily, yielding a dry powder compound similar in appearance to the original resin. For some applications such as pipe and siding, these powder compounds can subsequently be processed directly into the final product.
For other applications – such as wire & cable, rigid profiles for vertical blinds, or injection molded parts for computers or appliances – additional processing may be necessary. In this case, powder compounds are mixed, melted, and then formed into small pellets or cubes [approximately 0.25 in.2 (6.4 mm2)]. This important step can improve the compounds’ performance at the customer and ensures the final product meets stringent end-use requirements.