Gaskets and seals need to be regularly replaced due to the harsh operating conditions and high temperatures they are exposed too, which hastens the onset of degradation. Scott Phillips, Technical Market Development Manager (PU Elastomers) at Perstorp AB explains exactly how Capa™ polyols can improve resistance and durability.
What are gaskets and seals typically made of?
It is widely accepted that polyurethane elastomers are ideal materials for seals and gaskets due to their excellent mechanical properties including abrasion resistance and elasticity. The soft segment of these elastomers – which gives it its elastic properties – typically comprises of either a long polyester or polyether polyol chain. If a typical polyester polyol is used, mechanical properties are often very good but durability in wet conditions is hugely diminished leading to a short service lifetime. Polyether polyols are more durable, but have poor mechanical properties.
How can Capa™ make a difference?
Capa™ polyols, although still a polyester polyol, offers the best of both worlds – excellent mechanical properties, good low and high temperature performance and most importantly, excellent durability. This is because Capa™ polyols, while chemically similar to conventional polyester polyols, are manufactured by a completely different chemical process – ring-opening polymerisation. This allows for the production of a particularly ‘clean’ material with no by-products, the acid and water content can be kept exceptionally low. The principal chemical reaction for the degradation of the elastomer – the hydrolysis of the ester bond – is severely retarded.
What does this mean for performance?
Since the degradation process is dramatically slowed, the initial outstanding mechanical properties of the elastomers are retained for longer and thus the service lifetime is significantly extended. Compared to conventional polyester polyols, Capa™ has demonstrated higher resistance to both moisture and high temperatures. This is particularly important for seals and gaskets which are often employed in harsh environments.
Another reason that Capa™ is so durable is its inherent resistance to heat build-up. It has been shown that Capa™ ™-based elastomers absorb less energy when subjected to successive stress-strain cycles compared to conventional polyester polyols, which makes Capa™ particularly suited to dynamic applications.
This combination of outstanding initial mechanical properties, excellent durability – particularly in dynamic applications - makes Capa™ ideal for seal and gasket applications. Its excellent durability and prolonged service lifetime, will ultimately mean less maintenance and down time for the end user.