hi. What kind of polymer and additive is used in heat shrinkable closure?
Also, what type of fiber is usually used in these polymers?
Typical heat-shrink tubes for industrial applications are made of PVDF (or more rarely PE) loaded with carbon black. The type on photo is "zip tube" used mostly for repair rather than for manufacture. It may contain additional EVA layer inside to work as sealant.
Typical heat-shrink tubes for industrial applications are made of PVDF (or more rarely PE) loaded with carbon black. The type on photo is "zip tube" used mostly for repair rather than for manufacture. It may contain additional EVA layer inside to work as sealant.
Heat shrinkable materials are usually crosslinked materials with a crystalline melting point above RT and Tg below RT. The sleeve is deformed above the melting, cooled down with frozen in stress, then the stress is released when it is in position by heating above Tm again. Tg should be below RT otherwise it becomes rigid. Polyethylene and its copolymers together with flame retardants, ATH etc. are frequently used in the electrical industry. There are so-called "cold shrink" devices too from silicone rubber which are expanded mechanically and removable themoplastic insert is put inside, which is removed after positioning. In this case the "chemically induced stress relaxation" (scisssion of chains and gradual reduction of shrink force with time) should be taken into account.
shrinkable materials can be from PE or PVDF. We can also use mechanical method with heat source for producing shrinkable material.
With my best regards!
Adel OUESLATI
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