What are fillers?• Mostly needed by thermosets, sometimes also needed by thermoplastics.• Added to reduce cost.
Classification of fillers • Mineral fillers : e.g. CaCO3 , kaolin, feldspar, talc etc. • Metallic, conductive & magnetic fillers : iron, copper, zinc & lead • Fire retarding fillers : Sb2O3 • Organic and special purpose fillers : carbon black, wood flour, walnut flour • Flake reinforcement : mica • Continuous filament reinforcement : fibre glass, carbon graphite filaments etc. • Short fibre reinforcement : asbestos
Heat stabilizers• To prevent degradation that occur during high temp processing/fabrication.• PVC largest consumer.• e.g.- family of lead salts, complex barium cadmium solids, non toxic Ca & Zn salts
• Type: Ba / Cd - Clear calendered products, Injection moulded flexible products, blown film• Type: Ba / Cd / Zn – Clear calendered products, blown film, flexible products, plastisol processing• Type: Ba / Zn – Flexible calendered products, unsupported films for garments, artificial leather for automotive• Type: Ca / Zn (Non-Toxic) – Children’s toys, packaging films, base coat for artificial leather, top coat for floor coverings, conveyor belts, sealing compounds• Type: Ba / Cd / Pb – Calendered, injection moulded products, extreme high temp, and application.• Type: Lead Complex – Rigid PVC pipes, casing capping, electric wires.
UV STABILIZERS• UV light 280-400nm polymers unstable• To overcome this UV stabilizers are used.Classification-:1)UV absorbers: Hydroxy benzophenones2)UV quenchers: Piperidines3)Pigment: carbon blackApplications -:1) carpenting outdoor/seatings2) Acrylic coating used on outdoor sign boards3) Light diffusers4) Used in outer liners of HMHDPE
Antioxidants-:• Polymers when subjected to oxygen attack & if 1)there exists high concentration of unsaturated c-c bonds 2)residual polymerisation catalyst 3)it is subjected to highly oxidising conditions,then it undergo oxidation.-to overcome this problems long service life, antioxidants are used.Classification -:1)primary: hindered phenolics acryl amines2)secondary: phosphurous &sulphur containing compounds
Colorants Colorants Pigments (forms dispersion) Dyes (completely soluble)properties :1) hiding power2) particle distribution3) fastness to light,heat,chem. e.g. Benzidine yellow, red 2B pigments, Alumina hydrate, iron oxide .Applications:Packaging, domestic articles, space research , m/c switches, transportation
Antistatic agent• Due to low surface conductivity have poor conductivity accumulation of static charge. Which is undesirable because 1) attracts dust particles wear & abrasion & unsightly look. 2) charged metals results into powdering. 3) it can generate spark, which can become hazardous.e.g. butyl stearate, tri -ethanol-amine
Fire retardants• Polymers being organic compounds burn or decompose on exposure to fire, generates toxic fumes, smoke.• Two techniques: 1)use fire retardant raw material. 2)use fire retardant additives.e.g. inorganic :zinc borate halogenated :chlorinate paraffinsapplicable to polymers to be used in mines, automobiles, air vehicles, railways, etc. consumed by - polyesters, polycarbon polyurethanes.
Cross-linking agents• Thermosets cure either on application of heat or cross linking/curing/ hardening agents.• In some cases agent triggers off the reaction & therefore linking the resin molecules or• It enters into the parts between molecules and completes the chain.Classification :1)free radical intiator : Isobutyl nitrile, Alkyl peroxide .2)non free radical agents : Isocynate with polyol Used : Manufacture of Thermosets like polyurethane, Urea Formaldehyde, etc
Blowing agent• Polymeric foams preparation(2 ways) 1) mechanical 2) chemically• substances called blowing agents, which on heating decompose giving N & CO2• Rigid PVC,ABS,Polystyrene, polyolefins being chief consumers.Applications: mattresses, pillows, insulation, foam pipes for non-p conditions.e.g.para toluene sulphonyl hydrazide.
Lubricants• Hot processing of polymers need lubricants either internally or externally.• Internal lubricants decreasing normal cohesive forces between polymer moleculesgood flow conditions by lowering viscosity.• External lubricant don’t let melt to stick to hot surface of processing. By forming a thin layer at melt-solid interface. e.g. butyl stearate, octyl stearate, stearic acid
Impact modifiers• To upgrade physical properties of polymer to the extent prescribed by consumer, the additives added to polymers are called as strength (impact) modifiers.• They impart breakage resistance, rigidity, ease of post fabrication, strength to sheets• The strength imparted depends on time & temp conditions of processing .• Rigid PVC for prolonged outdoor exposure needs I.m., similarly epoxy & polyester thermosets require impact modifiers.