Which compound used as a stabilizer in PVC?
Barium-zinc additives are very effective heat stabilizers for PVC but are restricted for medical applications in some countries. Alternatives like calcium-zinc formulations are often used to stabilize medical-grade PVC against heat.
What is stabilizer in PVC?
Antioxidants are PVC Stabilisers that prevent oxidation of PVC from taking place due to atmospheric oxygen. Hindered amine light stabilizers are PVC Stabilizers that scavenge radicals produced by weathering. The next type of PVC Stabilisers are UV absorbers. They dissipate energy absorbed by UV rays.
How do heat stabilizers work?
Heat stabilizers protect polymers from the chemical degrading effects of heat or uv irradiation. These additives include a wide variety of chemical substances, ranging from purely organic chemicals to metallic soaps to complex organometallic compounds.
Why is PVC thermally unstable?
The mechanism is based on the reaction of oxygen with radicals generated in PVC to form unstable peroxy radicals. In addition, it is proposed that oxygen reacts directly with conjugated polyenes to form peroxy linkage.
How many types of PVC stabilizers are there?
There are several types of PVC stabilizers such as lead, tin, organic, and mixed metal stabilizers. These stabilizers are used to maximize the performance of PVC to which they are added for fulfillment of the end product requirement.
What are natural stabilizers?
The formulation of natural food products includes the use of plant sourced gums and starches as natural stabilizers. In formulating natural food products, gums and starches isolated from plant sources are widely used as stabilizers. …
How do you make PVC heat resistant?
Epoxy plasticizers (epoxidized soybean, linseed oils and tallate esters) are often used in PVC compounds as an auxillary co-stabilizer with mixed metal stabilizer systems. Functioning as HCl acceptors primarily, epoxy Plasticizers enhance the heat and light stability of most mixed metal/phosphite stabilized compounds.
What is not used as an UV stabilizer?
While HALS are also very effective in polyolefins, polyethylene and polyurethane they are not useful as stabilizers for UV radiation in PVC.
At what temperature does PVC degrade?
Thermal decomposition of PVC accompanied by hydrogen chloride secretion becomes apparent at 135 °C.In addition, hydrogen chloride which is generated in the presence of airborne oxygen, speeds up the polymer decomposition process to the point that at a temperature of 200 °C, a nearly total breakdown of PVC takes place.
What causes PVC to degrade?
Dehydrochlorination of poly(vinyl chloride) During processing, storage and utilization, PVC degrades as it is exposed to high temperatures, high mechanical stresses or UV light. Degradation of the polymer occurs by successive elimination of hydrogen chloride (HCl), which is called dehydrochlorination [73], see Fig. 20.
What is PVC resin?
Poly Vinyl Chloride Resin or PVC Resin as it is popularly called, is a thermoplastic Resin which can be softened on reheating. A common term for this commodity polymer is Vinyl. Often available in the form of a powder, PVC granules are highly resistant to oxidisation and degradation caused by atmospheric reaction.
Which is the best heat stabilizer for PVC?
Organotin mercaptides also offer outstanding color retention in plasticized and rigid PVC processing. Heat Stabilizers based on lead salts and soaps offer exceptional long-term heat stability. These heat stabilizers are considered as one of the most cost-effective form of stabilizers for PVC.
Why are lead stabilizers used in PVC windows?
Lead stabilizers when used in PVC windows lead to their discoloration. Leads offer the best electrical properties mainly due to the insolubility of lead chlorides formed during stabilization.
How is the homopolymer of PVC resin made?
PVC homopolymer is made by suspension, bulk (or mass), and emulsion polymerization methods. The amount and type of residual components on the resin shipped to users (catalyst residues, suspension agents, emulsifying agents, etc.) can differ a lot.