Semi-finished products Plastic granules Special compounds

Chemical resistanceIntroductionThe term “chemical resistance” is normally used,although an absolute resistance is never given. Thechemical resistance describes how the resistance propertiesof polymers interact with the chemical agents(e.g. air, gas, water, grease). This means that thesubstances influence the polymers, but at the sametime also the polymers influence the chemical agents.For example, some polymers affect on the greaseconsistency, and thus the grease influence negativelythe polymers.Influence on plasticsEvery chemical agent has got a different behaviourfor each polymers category. Its behaviour could cause,either chemical interactions or physical interactionswith the polymers.Chemical interaction agents react with the primaryvalence bonds and modify the polymers´ propertiesirreversibly. In this case the chain breaks, thus itshortens and induces an embrittlement of the polymers.The polymers response with softening, swellingtill its dissolution in the agent. Even a small chemicalattack could lead to strong properties changes.Physical interaction agents do not react with thepolymers, but they reduce their physical bondsforces. The agent penetrates in the empty areas ofthe chains, spreads them and increases the spacebetween the chains, thus it causes a reduction of thesecondary valence bonds forces. This reaction takesplace till the polymers reach a state of equilibrium.The polymers response with softening and swelling.If the agent is extracted from the polymers, they willnearly restore the initial properties.Physical interaction agents influence depend on thepolyamides conditioning. The polyamides, with anabsorption of water (agent), pass from a hard andbrittle condition to an elastic and tough condition.The influence intensity of the chemical agents dependson the following parameters:TemperatureA temperature increment leads to a speed incrementof the Brownian motion. The processes go every10°C temperature increment, from 3 up to 4 timesfaster. If the temperature rises above the glasstransition temperature, a sharp reduction of theresistance occurs.ZEDEX ® basic types ZEDEX ® families Post heattreatmentMachiningShippingoverviewSterilizationChemicalresistance81