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plasticizer By Amar Arakh
Plasticizer • Chemicals that are added to other polymeric substances, to improve the flexibility of the polymer or to aid in processing the polymer. • Additive designed to space out the polymer molecules, facilitating their movements and leading to enhanced flexibility (lower modulus)and ductility. Widely used to convert PVC from the rigid to the flexible variety. Can sometimes be polymeric. • The main role of the plasticizer is to improve mechanical properties of the polymers by increasing flexibility, decreasing tensile strength and lowering the second order transition temperature
Cont... • Mostly used in PVC (second largest material selling in Western Europe). • 80-90% plasticizers are used in PVC. • The Successful addition of a plasticizer will result in the formation of a product with a degree of flexibility, such as a cable insulation or sheathing, a floor covering or flexible profile. • Plasticizers acts to reduce the Tg of PVC .
Plasticizer market • 6 million ton plasticizer produced every year. • 80-90% of the worldwide consumption is in PVC
Mechanism....... • As plasticizers usually possess relatively long alkyl chains, they have the effect of screening the polymer chains from each other, thereby preventing them from re-forming the chain-chain interactions which give the unplasticized polymer its rigidity.
Plasticization theories • Lubricity Theory: Plasticizer acts as a lubricant, reducing intermolecular friction between polymer molecules responsible for rigidity of the polymer. • Gel Theory: Polymers are formed by an internal three-dimensional network • Free Volume Theory: Plasticizer lowers the glass transition temperature (Tg) of the polymer. • Mechanistic Theory: Plasticizer molecules are not bound permanently to the polymer molecules form.
Classification • Majority of plasticizers are Organic Esters. According to technique of Plasticization External Internal Not physically bound to polymer & can evaporate, migrate or exude from polymer. Group constituting a part of a basic polymer chain, which may incorporate bet. chain
Classification • Other Conventionally classified as Primary Secondary Sufficient level of compatibility to be used give desirable effect. directly interact with chain. Limited compatibility & can exude if used alone. Incorporate with primary plasticizer.
Phthalates • Most widely use as plasticizer. • Phthalates accounts 92% of all plasticizers. • A Phthalate ester derived from phthalic acid by an esterification reaction. • Properties: Colorless Oily liquid ( like vegetable oil) Ester odor, High boiling point, Inert and very stable over long periods
DOP/DEHP • Primary use as plasticizer. • Insoluble in water, Boiling point: 386.9oc,Density: 0.9732 g/L, Molecular weight: 390.5618 g/mol. • Production: Phthalic anhydride with 2-ehaxenol: C6H4(CO)2O + 2 C8H17OH → C6H4(CO2 C8H17)2 + H2O • Used in medical devices ,Toys, Pacifiers, Vinyl Upholstery, Food containers, Table cloths, Shower curtains.
DINP • Mixture of chemical compounds consisting of various isononyl esters & phthalic acid. • Properties :Insoluble in H2O,Soluble in most organic solvents, Boiling point: 250Density: 0.98g/cc, Molecular weight: 418.6 g/mol. • Use in Replacing DEHP in toys when initially determined to be carcinogenic.
DIDP • Mixture of compounds derived from the esterification of phthalic acid & isomeric decyl alcohol. • Properties: density:0.96g/cc, melting point: -50, boiling point: 250-257c at 0.5KPa. • Uses in plastisol application, provides good initial viscosities & excellent viscosity stability.
Sebacates & adipates • Dibutyl Sebacate is an organic chemical , a dibutyl ester of sebacic acid. • Properties: density: 0.94g/cc, boiling point:344.5c , melting point:-10c, flash point: 178c. • Used in food packaging industry, in plastics used for medical devices, and for pharmaceutical applications,
Trimellitate Plasticizers - • Synthesized using one mole of trimellitic anhydride and 3 moles of an alcohol. The third alkyl group, compared to phthalates, contributes higher molecular weight (low diffusivity);the third ester group contributes sufficient polarity to enhance compatibility with PVC. Tri (2-ethylhexyl) Trimellitate
Fatty acid esters • Esters of fatty acids & monocarboxylic acids can be used as viscosities depressant for PVC pastes & also as secondary plasticizers for plasticized PVC. • Present in liquid form. • Stearic acid esters are used as plasticizers & processing agent for various plastics & also as lubricants for PS.
Oligomeric/polymeric plasticizer • These extend the life of PVC products considerably • They reduce migration, extraction & volatility. • In these adipates are generally used in mixture with other plasticizer to increase plasticization & improve low temp. Properties. • Epoxied plasticizer (soybean oil & linseed oil) are used as stabilizing plasticizer offering properties of migration resistance in PVC compounds.
Selection criteria • Choice of plasticizer depends upon the properties required in final product, the application technology used to make it !! • Prize boundaries present for product process. • Stability in processing & service condition. • Compatibility & ease of mixing. • Toxicity.
Plasticizer efficiency.. • The measure of concentration of plasticizer require to improve a specifies softness to PVC. • Plasticizer efficiency increases as carbon number of alcohol chain decreases. • For phthalates, BBP>DIHP>DOP>DINP>DIDP • Linear plasticizer is more efficient.
