What is PVC

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Category: Literatur
Published on Tuesday, 22 January 2013 14:47
Written by Administrator
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PVC, These initials stand for poly Vinyl Chloride, one of the main plastics materials. It also is one of the oldest, since the first industrial sysnthesis date back to 1913 and its commercial development to 9131 (Vinyl records
 
Polyvinyl Chloride (PVC) or more commonly known as vinyl. PVC is a synthetic material composed of giant molecules-polymers. These polymers consist of a chain of vinyl chloride molecules composed carbon (C), Hydrogen (H), and Chlorine (Cl) atoms.
 
Carbon and Hydrogen are today essentially derived from oil. Chlorine is extracted from sodium chlorine (NaCl), which is common salt.  The electrolysis of sodium chloride produces, in almost equal parts, chlorine (which a part from PVC production, is the basic component of key product use in chemestry and agriculture and of course bleach) and caustic soda (which is widely used for the making of glass, paper, alumunium, etc.
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.
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