cast Stretch film – A highly stretchable plastic film, usually made of linear low density polyethylene (LLDPE), wrapped around an item. The elastic recovery allows the items to be tightly bound.
Stretch film is commonly used to wrap products on pallets and secure them to each other. This often helps reduce product loss, stops load tampering, and reduces worker injuries. Below is a breakdown of the two most common stretch film extrusion processes.
Cast stretch wrap – also known as cast stretch wrap – is manufactured using the cast extrusion process. The cast extrusion process is a continuous process in which thermoplastic material is melted and extruded through a flat die onto a cold roll, where it is quenched and re-solidified.
This process gives cast stretch film excellent clarity, requires less force to stretch, is more resistant to tearing, relaxes quietly from the machine, and provides better adhesion. Both machine-grade and hand-grade cast stretch films are available.
manufacturing costs Higher clarity allows the user to see the packaged product. Cast stretch wrap can be unfolded quietly compared to blown stronger stretch wrap. cast stretch film provides a double-sided lamination that allows the wrapped product to remain firmly wrapped.
does not provide the load/holding power that blown stretch film provides. Cast stretch film has lower memory and tear resistance than blown stretch film.
Blown Stretch Wrap – Also known as blow stretch wrap, manufactured using a blow molding extrusion process. This plastic melt is extruded through an annular slit die (usually vertical) to form a thin-walled tube. Air is introduced through a hole in the center of the die,
causing the tube to expand like a balloon. At the top of the tube, stronger a ring of air is blown onto the film to cool it. This process makes blown film tougher and more flexible than cast film. The higher mechanical properties of blown film typically allow for greater load retention.
provides higher load and stretch capacity Blown stretch film is a higher quality film.
Blown stretch film has a stronger higher memory when stretched, which allows loads to remain better secured. Higher tear resistance is an advantage when securing loads with sharp edges.
Higher cost due to manufacturing stronger process Poor transparency of blown stretch wraps due to crystallization during the manufacturing process. Blown film can also make noise when removed from the roll.