Polyacetals Polyacetal is an opaque, very hard, and highly crystalline polymer that offers excellent strength and stiffness in many applications like automotive or sporting goods.

Stabilization

Polyacetals are prone to degradation at high processing temperatures. Due to this behavior the polymer needs a very effective processing stability package. Antioxidants such as Ciba® IRGANOX® 245 and Ciba® IRGANOX® 1098 provide excellent processing stability to polyacetal resins. Moreover, Ciba® IRGANOX® 245 and Ciba® IRGANOX® 1098 offer excellent long-term thermal stability combined with good resistance to extraction. Ciba® IRGANOX® 245 is highly recommended for color critical applications. Polyacetals are prone to chalking when exposed to UV-light. To protect the polymer from surface degradation and discoloration the use of Ciba® TINUVIN® 622 or Ciba® TINUVIN® 770 in combination with Ciba® TINUVIN® 234 is recommended

Coloration

It can be very difficult to select colrants for polyacetal polymers. This is because they rapidly depolymerize at elevated temperatures, and /or are shear sensitive, releasing formaldehyde. De-polymerization (unzipping of the polymer back bone) is accelerated by acidic substances, moisture, and by some metal containing colorants. Therefore, adequate pre-testing can be crucial. A large number of organic pigments are available and these are the preferred route for coloration rather than polymer soluble colorants or inorganic color pigments. Due to the highly crystalline nature of this group of polymers, very often high levels of pigment are required to achieve deep shades. Moreover, the physical and chemical properties of the polymer may be compromised.

Thus, high strength organic pigments dominate the coloration of Polyacetals. Care must be taken when selecting colorants for POM, due to the aforementioned reasons and the fact that these polymers are non-acid resistant. Recommended colorants can be found in our Ciba® ORACET range for Engineering Plastics and in the Ciba® CROMOPHTAL® and Ciba® CINQUASIA® ranges for High Performance Pigments. Also classical pigments from Ciba® IRGALITE® range can be recommended.

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