Additives are usually required
To impart stability against the degradative effects of
various kinds of aging processes
Enhance product quality and performance

Ther mal and light stabilizers, antioxidants, and flame retardants

(influence essentially the chemical interaction of polymers with the environment)

Plasticizers, lubricants, impact modifiers, antistatic agents, pigments, and dyes
usually employed to reduce costs, improve aesthetic qualities, or modify the processing
mechanical, and physical behavior of a polymer

These additives are normally used in relatively small quantities

Nonreinforcing fillers are employed in large quantities to reduce overall formulation costs
provided this does not result in significant or undesirable reduction in product quality or
performance

Alloying and blending

Plasticizers

The principal function of a plasticizer is to reduce the Tg of a polymer so as to enhance its flexibility over expected temperatures of application

Plasticizers are usually high boiling organic liquids or low melting solids
They are also sometimes moderate-molecular-weight polymers

Like ordinary solvents, plasticizers act through a varying degree of solvatin
action on the polyme

Plasticization is difficult to achieve in nonpolar polymers like polyolefins and
highly crystalline polymers

Polymer plasticization can be achieved either through internal or external incorporation o
the plasticizer into the polymer

Internal plasticization involves copolymerization of the monomers of the desired polymer
and that of the plasticizer so that the plasticizer is an integral part of the polymer chain. Tg. The
most widely used internal plasticizer monomers are vinyl acetate and vinylidene chloride

External plasticizers are those incorporated into the resin as an external additive. Typical
low-molecular-weight external plasticizers for PVC are esters formed from the reaction of acids
or acid anhydrides with alcohols

Monomeric plasticizers ( phthalate, terephthalate, adipate, phosphate esters)
Polymeric and permanent plasticizers
(Linear polyesters obtained from the reaction of dibasic acids such as adipic, sebacic, and
azelaic acids with a polyol

Polymeric stabilizers have higher molecular weights than the monomeric

plasticizers, and less volatile when exposed to high temperatures either during processing or in
the end-use situations, less susceptible to migration and less extractible

Epoxy Plasticizers derived from vegetable oil, epoxidized soybean is an example

confer heat stability and light stability on PVC products
have relatively low-temperature properties

The ideal plasticizer must satisfy three requirements

Compatibility

Permanence

requires low volatility, extractability, nonmigration, and heat and light stability. Lack of permanence involves long-term diffusion into the
environment

Efficiency

Also it should be odorless, tasteless, nontoxic, nonflammable and heat stable

Fillers and Reinforcements

Different types of fillers are employed in resin formulations Added to improve tensile strength & abrasion resistance
toughness & decrease cost

Antioxidants and Thermal Stabilizers

Antioxidants

Free radical scavengers (Primary antioxidants, radical or chain terminators)-inhibit
oxidation through reaction with chain-propagating radicals

Peroxide decomposers (secondary antioxidants or synergists)- break down
peroxides into nonradical and stable products

Thermal Stabilizers

Thermal stabilizers may be based on one or a combination of the following classes of
compounds

Barium/cadmium (Ba-Cd), calcium/zinc (Ca-Zn), organotin, organo-antimony
phosphite chelates, and epoxy plasticizers

Ba/Cd stabilizer systems, which represent the largest share of the PVC stabilizer
market, are available as liquids or powders

UV stabilizers

UV radiation in the range 290 to 400 nm has potentially degradative effects on
polymers since most polymers contain chemical groups that absorb this radiation and
undergo chain scission, forming free radicals that initiate the degradative reactions

UV stabilizers are employed to impede or eliminate the process of degradation and, as
such, ensure the long-term stability of polymers, particularly during outdoor exposure

Light stabilizers are typically UV absorbers or quenchers

The former preferentially absorbs UV radiation more readily than the polymer
convert ing the energy into a harmless form

Quenchers exchange energy with the excited polymer molecules by means of an energy
transfer mechanism

Other UV stabilizers deactivate the harmful free radicals and hy drop eroxides as soon as
they are formed