Adhesive layers are essential
PEX EVOH pipes use adhesive layers to bond the EVOH to PEX. PEX and EVOH do not bond directly. Adhesives are required between them. Example: the adhesive acts like glue between layers.
Adhesive material composition
The adhesive is a modified polyolefin. It is compatible with both PEX and EVOH. The adhesive melts and bonds during extrusion. PEX EVOH pipes use a special adhesive.
Co-extrusion process
All layers are extruded together in a co-extrusion die. The layers are still molten when joined. This allows the adhesive to bond with the PEX and EVOH. PEX EVOH pipes are formed in one continuous process.
Melt bonding
The adhesive and pipe materials are all molten. They fuse together as they cool. This creates a strong molecular bond. PEX EVOH pipes have a permanent chemical bond.
Adhesive functional groups
The adhesive has chemical groups that attract PEX. It also has groups that attract EVOH. This creates a strong bond between layers. PEX EVOH pipes have a stable layer structure.
Temperature and pressure
Heat and pressure are applied during co-extrusion. This ensures proper bonding. The temperature is precisely controlled. PEX EVOH pipes require precise conditions for bonding.
Bond strength testing
Manufacturers test the bond strength of the layers. The layers should not separate. Bond strength is a key quality measure. PEX EVOH pipes have strong layer bonds.
Example: adhesive application
In a co-extrusion die, the adhesive is applied. It is placed between the PEX and EVOH layers. The layers bond as they cool. PEX EVOH pipes have a secure layer structure.
Example: layer separation testing
A sample is tested for layer separation. The test tries to peel the layers apart. The bond is strong and resists separation. PEX EVOH pipes layers are securely bonded.
Adhesive curing
The adhesive cures as the pipe cools. This creates the final bond strength. The bond is permanent and stable. PEX EVOH pipes have a cured adhesive bond.
Layer stability over time
The bond remains stable for decades. Temperature changes do not affect the bond. The layers stay securely attached. PEX EVOH pipes have long-term layer stability.
Final bonding summary
PEX EVOH pipes use adhesive layers to bond the EVOH to PEX. The adhesive is a modified polyolefin. It is applied during the co-extrusion process. The layers are molten and fuse together. Heat and pressure ensure proper bonding. Bond strength is tested for quality. The bond remains stable over time. PEX EVOH pipes have a strong, permanent layer bond. Example: a reliable layer structure.