Rubber Chemicals

VULKANOX® antidegradants
Aging processes, which are caused by oxygen or heat, change the properties of the vulcanizates. Rubbers generally are subject to such changes that occur in the course of time and can lead to partial or complete destruction. Possible consequences are depolymerization, fatigue, brittleness, cracks and even disintegration. The resistance of a rubber article to oxygen, ozone and other reactive substances is determined mainly by the elastomer on which the compound is based and by the chemicals that are added to retard the destructive processes.

Unsaturated groups in the rubber molecule are the reason for the rubber's sensitivity to oxygen, which increases with temperature. If catalysts of oxidation (known as rubber poisons) are present, aging is rapid. The results are hardening and embrittlement, crazing effects and fatigue. Ozone or dynamic stress (fatigue) lead to cracking on the surface of the rubber article.

Antidegradants such as Vulkanox® are chemicals which protect the vulcanizates against damaging external influences. Depending on the chemical structure, they act against one or more of the aging processes mentioned. None of the antidegradants is universally effective, each has a definite spectrum of activity and characteristic effectiveness, and a definite propensity to discolor the goods if they are exposed to light. Staining antidegradants are generally more effective than non-staining ones.

Key Properties

• protection against oxidation, ozone, heat and rubber poisons

• protection against dynamic stress

VULKACIT® accelerators
Vulcanization is the conversion of a high-molecular material from the plastic to the elastic state. One of the key chemical reactions in this process is that of rubber with sulfur. Sulfur vulcanization, widely used in the rubber industry, requires the use of vulcanization accelerators such as Vulkacit®.

Vulcanization accelerators are not catalysts because they are part of the chemical reaction. The great variety of accelerators available is a result of their different influences on the vulcanization kinetics (scorch and cure time) and on physical properties such as tensile strength, elasticity or resistance to aging. In many cases, accelerators are combined to supply optimal processing and physical properties.

Key Properties

• Mercapto accelerators: very fast accelerators giving a very broad plateau and good aging resistance

• Sulfenamide accelerators: fast but very safe accelerators providing a steep slope on the rheometer curve

• Thiuram accelerators: fast accelerators, especially for efficient or sulfurless cure

• Dithiocarbamate accelerators: very fast accelerators used alone or as a booster for thiazole and sulfenamide cure systems

• Amine accelerators: special accelerators for extraordinary applications.

RENACIT® peptizing agents
Natural rubber is masticated to improve processing. By breaking down the molecular chain the polymer viscosity is reduced. This is usually achieved by mechanical forces in a mixer, which consumes energy. The higher the temperature, the faster the mastication. Renacit® mastication agents decrease the mastication time, and therefore the dump temperature, by a special chemical process. Hence, less power is consumed, mixer capacity is increased and costs are reduced. Renacit® is very efficient: only a very small amount is required.

Key Properties

• reduction of mastication times and dump temperature

• very efficient

• cost savings