Heat Stabilizers

Abstract

Halogenated polymers, particularly poly(vinyl chloride) (PVC) and poly(vinylidene chloride) (PVDE), require the use of heat stabilizers for effective processing. A variety of chemical classes are effective commercial heat stabilizers since they prevent the catastrophic degradation of these polymers at normal processing temperatures. The most effective class of heat stabilizers are the organotin mercaptides which can provide effective stabilization at dosages of the order of 1% or less of the PVC. Mixed metal products, consisting of combinations of calcium and zinc or barium, calcium and zinc soaps are used extensively in many flexible PVC applications. Heat stabilizers based on lead soaps and salts have been used commercially in PVC since the 1930s. During the past decade, completely new heat stabilizer technologies, based on organic compounds, have been introduced to the market for rigid PVC processing. All heat stabilizers must provide several functions to stabilize PVC. They must neutralize hydrogen chloride, react with “defect sites” on the polymer to replace weakened carbon–chlorine bonds, prevent autoxidation effects, and disrupt conjugated polyenes on polymer. Reactive mechanisms for the major classes of technologies are reviewed. The heat stabilizers must be very cost‐effective in a highly competitive marketplace. Several suppliers and their major products are highlighted. Health and safety concerns for the major classes of heat stabilizers are also presented.

Improvement of the Thermal and Optical Performances of Protective Polydimethylsiloxane Space Coatings with Cellulose Nanocrystal Additives

“…The higher thermal stability was assigned to the presence of chlorine and fluorine within the material, which might act as radical scavengers during cellulose degradation when radical scissions are involved. The better results obtained with chlorine are consistent with the better thermal stabilization expected with such compounds. , …”