ADDITIVES IN PLASTICS

By - Kirtan .V Roll – MO7049

What are What are additives ? additives ?

What are What are additives ? additives ?

Materials Materials dispersed dispersed polymer polymer matrix without affecting matrix without affecting

significantly the molecular significantly the molecular structure of the polymer to attend structure of the polymer to attend certain desirable properties certain desirable properties

Why to use additives in plastics ?

• Improve processing conditions• Increase resin’s stability to oxidation• Obtain better impact resistance• Increase or decrease hardness• Control surface tension• Facilitate extrusion moulding• Control blocking • Reduce cost• Increase flame resistance.

Types of additives• Fillers• Antioxidants• Heat stabilizers• UV stabilizers• Colorants• Antistatics• Flame/fire retardants• Cross-linking agents• Blowing agents• Lubricants• Impact modifiers• Processing aids

What are fillers?• Mostly needed by thermosets,

sometimes also needed by thermoplastics.

• Added to reduce cost.

Classification of fillers

• Mineral fillers : e.g. Mineral fillers : e.g. CaCO3CaCO3 , kaolin, feldspar, talc , kaolin, feldspar, talc etc.etc.

• Metallic, conductive & magnetic fillers : iron, Metallic, conductive & magnetic fillers : iron, copper, zinc & leadcopper, zinc & lead

• Fire retarding fillers : Fire retarding fillers : Sb2O3 Sb2O3

• Organic and special purpose fillers : carbon black, Organic and special purpose fillers : carbon black, wood flour, walnut flourwood flour, walnut flour

• Flake reinforcement : micaFlake reinforcement : mica

• Continuous filament reinforcement : fibre glass, Continuous filament reinforcement : fibre glass, carbon graphite filaments etc.carbon graphite filaments etc.

• Short fibre reinforcement : asbestos 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 black

Applications -: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

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

Colorants

Dyes (completely soluble)Pigments (forms dispersion)

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 paraffins

applicable 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.

Additives : Packaging appications

• Enhances barrier properties• Better transparency/Gloss• Better printing/sealing properties• Anti microbials

Thank you ;)