MOISTURE BARRIER CLADDING
Moisture Barrier is a very important and most discussed topic by the insulation systems experts. Moisture barrier is a coating applied on the back of a metal jacketing to prevent corrosion of the jacketing and also the underlying pipe. It is a very important component of a good insulation system and used in all applications including hot and cold (cryogenic) applications. The barrier has a very important role to isolate the jacketing from other insulation layers and shield the underside of the metal jacketing from moisture contact and thus preventing corrosion.
The industry have seen many different materials over the years which have been used as Moisture barriers on metal jacketing in mechanical insulation systems. Two most common moisture barriers used are Polykraft and Polysurlyn barriers.
Polykraft:
Polykraft is a layer of kraft paper laminated to a thin layer of polyethylene film which is factory applied on the metal in a lamination process. It is an improvement from the paint system as Polykraft is 1.5 mil (37.5 μm) thick and uses polyethylene layer which is good for moisture resistance. However, kraft paper exhibits a poor water resistance and can be easily damaged on mechanical abuse. The properties of polykraft deteriorate significantly over a short time. Polykraft promotes the growth of fire, hence is not used in areas where there is a high risk of fire.
Polysurlyn:
Polysurlyn moisture barrier is a 76 μm thick three-layer film which is factory laminated on the metal without the use of any addition adhesive layer. The layers are a combination of polyethylene and Dupont™ Surlyn®. Surlyn® is known for its strength and moisture resistance properties and combining it with 2 additional layers of polyethylene prevents the alignment of pinholes in each layers, hence, this moisture barrier exhibits zero pinholes. Polysurlyn moisture barrier is the most popular moisture barrier used today.
The industry have seen many different materials over the years which have been used as Moisture barriers on metal jacketing in mechanical insulation systems. Two most common moisture barriers used are Polykraft and Polysurlyn barriers.
Polykraft:
Polykraft is a layer of kraft paper laminated to a thin layer of polyethylene film which is factory applied on the metal in a lamination process. It is an improvement from the paint system as Polykraft is 1.5 mil (37.5 μm) thick and uses polyethylene layer which is good for moisture resistance. However, kraft paper exhibits a poor water resistance and can be easily damaged on mechanical abuse. The properties of polykraft deteriorate significantly over a short time. Polykraft promotes the growth of fire, hence is not used in areas where there is a high risk of fire.
Polysurlyn:
Polysurlyn moisture barrier is a 76 μm thick three-layer film which is factory laminated on the metal without the use of any addition adhesive layer. The layers are a combination of polyethylene and Dupont™ Surlyn®. Surlyn® is known for its strength and moisture resistance properties and combining it with 2 additional layers of polyethylene prevents the alignment of pinholes in each layers, hence, this moisture barrier exhibits zero pinholes. Polysurlyn moisture barrier is the most popular moisture barrier used today.
