The additive systems for PVC are either classified on the basis of their chemical constitution or
according to the function they perform. The later is more significant from the product
formulator point of view and therefore forms a part of this discussion . According to functional
behaviour , the additive systems for PVC are classified as follows :
CLASSIFICATION OF PVC ACCORDING TO THEIR FUNCTIONAL BEHAVIOUR
S.No
CATEGORY/CLASS OF ADDITIVES
FUNCTIONAL BEHAVIOUR
A
ADDITIVES WHICH ENHANCE PROCESSING CHARACTERISITCS
1
HEAT STABILISERS
Protect the polymer against heat deterioration during compounding, processing and during subsequent service life of the polymer.
2
PLASTICIZERS
Enhance workability and impart flexibility to the polymer.
3
LUBRICANTS
Reduce friction ,heat build-up and wear between the polymer melt and processing machine(external function). Also reduce melt-viscosity and increase melt flow of the polymer(internal function).
B
ADDITIVES WHICH ENHANCE PERFORMANCE, ADD FUNCTIONALITY AND ENHANCE AESTHETICS
1
PROCESSING AIDS
Enhance processing charactristics of the un-plasticized and plasticized PVC
2
IMPACT MODIFIERS
Reduce brittleness , enhance impact strength.
3
FIRE -RETARDANTS
Interfere with the chemistry and/or physics of combustion to induce non-flammable characteristics under a specified set of conditions.
4
SMOKE -SUPRESSANTS
Interfere with the chemistry and/or physics of combustion to reduce the generation of smoke/fumes during burning as well as during smouldering process.
5
BLOWING AGENTS
Decompose to generate cells (gas pockets) in the polymer matrix thereby reducing density, providing cushioning effect and insulating properties in addition to reducing cost.
6
FILLERS
Improve one or more properties of the polymer and also reduce cost.
7
COLORANTS
Impart color to the polymer and thus enhance aesthetics of the end product.
8
ANTI-OXIDANTS
Arrest oxidation by molecular oxygen thereby preventing deterioration due to oxidative degradation perform synergistically with heat stabilisers.
9
U.V STABILISERS
Absorb in the ultra-voilet region of light spectrum thus protect the polymer from the deteriorating effects of UV rays.
10
MATTING AGENTS
Reduce gloss and provide an appealing smooth matt finish to the end product generally used in cable formulations.
11
VISCOSITY REDUCERS
Reduce viscosity of the PVC plastisols enhancing workability and shelf life . Also aids in deaeration of the paste.
12
ANTI-OXIDANTS
Arrest oxidation by molecular oxygen thereby preventing deterioration due to oxidative degradation.
13
ANTI-BLOCKING AGENTS
Eliminate or minimize blocking of films, sheets or coatings i.e their tendency to self adhere.
14
ANTISTATIC AGENTS
Prevent development of static charge on the product.
