calciumzinc

Calcium-zinc stabilizers, often abbreviated as CaZn, are a class of heat stabilizers used in the processing of polyvinyl chloride (PVC). They are formulated as mixed metal stabilizers composed mainly of calcium and zinc soaps derived from fatty acids, typically stearates, with other additives as needed. They are designed as a non-toxic alternative to lead-based stabilizers.

During PVC processing at elevated temperatures, hydrochloric acid is released from the polymer chain, which can catalyze dehydrochlorination and accelerate degradation. Calcium-zinc stabilizers neutralize HCl and form stable metal halide residues, thereby reducing dehydrochlorination, enabling processing at higher temperatures and protecting color and physical properties. In addition to stabilization, the metal soaps can act as lubricants and processing aids, improving melt flow and mold release.

CaZn stabilizers are widely used in rigid and flexible PVC applications, including profiles, pipes, fittings, cable insulation, and consumer goods. They offer low toxicity, low odor, and excellent color stability and weather resistance, making them popular in formulations where lead or cadmium stabilizers are undesirable.

Limitations include cost relative to some basic stabilizers and sometimes less high-temperature stability compared to some modern alternatives. Formulators may combine CaZn with other stabilizers or processing aids to tailor performance for specific PVC grades and processing conditions.

See also: PVC stabilizers; calcium stearate; zinc stearate; lead stabilizers.