Heat Stabilizers

Abstract

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. By far the most common polymer requiring the use of heat stabilizers is poly(vinyl chloride) (PVC). However, copolymers of PVC, chlorinated poly(vinyl chloride) (CPVC), poly(vinylidene chloride) (PVDC), and chlorinated polyethylene (CPE), also benefit from this technology. PVC is the most important class of halogenated polymers requiring these chemical additives. In normal operations, PVC resin is intimately mixed with the desired ingredients under high intensity shear mixing conditions to result in a homogeneous dry powder compound. The heat stabilizers can be either liquids or powders and are added early in the blending cycle to afford stabilizing action during this operation. Preheating the resin to about the glass‐transition temperature facilitates the adsorption of the liquid additives giving the final compound better powder flow properties and decreasing the bulk density. Post‐compounding operations, eg, extrusion pelletizing, can increase the overall heat history of the polymer, thus necessitating slightly higher levels of heat stabilizers to compensate for this. Organotin‐based heat stabilizers are the most efficient and universally used PVC stabilizers. These are all derivatives of tetravalent tin. The second most widely used class of stabilizers are the mixed metal combinations. These products predominate in the flexible PVC applications in the United States. The commercially important alkali and alkaline‐earth metals used in these stabilizer systems are based on the salts and soaps of calcium, zinc, magnesium, barium, and cadmium. Other organic compounds, such as phosphites, epoxides, polyols, and β ‐diketones, can also be added to enhance the performance further. Antimony mercaptan stabilizers are also used.

Investigation of carboxymethyl chitosan in the development of biodegradable soft bait fishing lures

“…Typically, heat stabilizers are composed of harmful materials such as organic compounds, metallic soaps, or complex organometallic compounds which could have a negative effect on the environment and aquatic species (Othmer, 1994). Another trend is observed for the 5 and 10% chitosan samples where the viscosity begins to increase suddenly from 50 to 75°C before plateauing from 80 to 100°C.…”