PVC products if the water immersion, or outdoor exposure, or bending, stretching and so on will produce whitening phenomenon, and loss of transparency. Below, we come from in PVC stabilizer analysis of water immersion bleaching, insolation bleaching and stress bleaching of these 3 big bleaching problems.

1. Water bleaching

Many types of transparent PVC products have a whitish, cloudy appearance when exposed to water or steam for long periods of time. Soft products are more powerful than hard products. This phenomenon is thought to be caused by the presence in the formulation of an additive or decomposition of an additive that is prone to hydration.

If only from the PVC stabilizer analysis, it is because of water immersion, so that the stabilizer from the precipitation of PVC, and hydration, forming hydrate precipitation on the surface (affect transparency) . In this case, even if the saturated water is gone, the stabilizer can not return to the original, only the increase in temperature, so that the compatibility of the stabilizer has been restored, can become transparent.

2. Bleaching in the Sun

PVC products in outdoor exposure, albinism will also appear. This is related to the compatibility of PVC stabilizer. In metal soap PVC stabilizer, benzoate with good compatibility with PVC has less bleaching phenomenon than stearate. Organotin stabilizer is not easy to produce albinism, sulfur-containing organotin is the best, followed by laurate, maleate. Addition of light stabilizer, phosphite ester and liquid composite stabilizer can prevent or alleviate the bleaching of PVC due to exposure to sunlight.

3. Stress bleaching

Stress bleaching refers to the PVC hard products in the role of mechanical forces, such as bending, stretching, PVC products such as bending crease, stretching part of the whitening phenomenon. It may be due to the change of molecular structure, the orientation of polymer molecular chain, the change of density of PVC, and the light scattering between some molecules, which make the PVC products appear white.

Some experts believe that the addition of high surface energy PVC stabilizer, to compensate for the orientation of the molecular chain caused by the gap method is effective. The use of organotin stabilizers can reduce the albinism, especially when combined with organotin maleate.

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