Blocking is an undesirable attraction between adjacent layers of film or sheet, often making it difficult to the separate individual layers. Certain polymers including, polyolefins and polyesters have an inherent tendency to block.
Blocking can occur during extrusion, conversion processes or during storage. Blocking can reduce packing efficiencies on automated and manual packing lines as it causes for example bags to be more difficult to open and stacks of thermoformed trays harder to separate.
The introduction of an antiblocking agent into a polymer will reduce the blocking tendency allowing films or sheets to be easily separated. The antiblocking agent will create a microscopic roughening of the film or sheet surface which reduces the available contact area between adjacent layers.
Many different materials can be used to give an antiblocking effect. The choice of antiblock depends upon the polymer being used and the quality requirements of the end product. For example, if a product requires high clarity, it is important to choose an antiblocking agent with a refractive index as close as possible to that of the polymer.
Wells Plastics has developed a range of antiblocking masterbatches using finely selected raw materials which have been successfully used to:
- Improve winding / unwinding quality in reeled materials.
- Produce easy opening packaging.
- Improve the denesting of thermoformed articles.
Antiblocks are non-migratory additives and therefore, in coextruded structures, need to be present in the outer layers.
Wells Plastics antiblocking masterbatches can be custom formulated to suit specific applications or polymer types. Combination masterbatches with slip are also available. Please contact your Wells Plastics representative for further details.
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