As with UV light, heat tends to oxidize polymers. The symptoms are embrittlement, melt flow instability, loss of tensile properties and discolouration. The mechanism of stabilization is therefore to prevent oxidation or to mitigate its effects. Plastics, particularly thermoplastics, may also require stabilization protection against degradation from heat during processing or in use. This article reviews the systems currently available, recent developments in technology and the present market trends in heat stabilizers.
How they work
Because of its structure, PVC is particularly sensitive to heat and is by far the largest user of heat stabilizers. Other vulnerable polymers are chlorinated polyethylene and PVC/ABS blends. The increasing use of engineering plastics in applications involving prolonged exposure to heat also calls for special stabilizer systems.
Another important growth area for heat stabilizers is recycled materials, where they will be used increasingly in inhibiting degradation and secondly in re-stabilizing post-use plastics waste.