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Antiblocking

Antiblocking Imerys minerals - your ideal antiblocking solution for PE films

Plastic film blocking is a common occurrence during film production, converting and end use. It results in the adhesion of adjacent plastic film layers to each other rendering separation difficult. Imerys minerals provide an optimum balance of haze, antiblocking and mechanical properties.

Polyethylene (PE) is one of the most widely used polymers and PE films are the most common in packaging applications. PE is relatively easy to process but thin films have a tendency to stick to each other when pressed tightly together or wound onto a core.

This tendency to block increases with the presence of low molecular weight molecules on the surface of the film. Temperature, film winding pressure, and smoothness of the film surface also play a part.

Bright, fine-grind minerals with an irregular particle shape are commonly used as antiblocking additives to reduce blocking force, a measure of film-to-film adhesion.  Antiblocking minerals work by generating a micro-roughness that limits the contact between adjacent plastic film surfaces, reducing blocking force.

Antiblocking minerals must provide a good overall balance of optical and mechanical film properties. Other important properties are plastic additive adsorption on the mineral surface, low hardness and low yellow index. For high transparency films, the mineral’s refractive index must also closely match that of the polymer, and particle size distribution is also crucial to minimizing light scattering.

Diatomaceous Earth

Flux calcined diatomaceous earth (DE) provides the best antiblocking performance in plastic films. Calcination is heat treatment to above 1,000°C which changes the mineralogy and morphology of the mineral and imparts excellent anti-block properties.

Flux calcined DE has very irregular shaped particles which provide fewer film surface contact points hence very low blocking force.

Imerys Celite® flux calcined diatomaceous earth grades provide:

  • outstanding film anti-block performance
  • increased film clarity
  • reduced haze

Diatomaceous earth provides outstanding antiblock performance, good clarity and low haze

Calcined Kaolin

Kaolin minerals are naturally occurring hydrated aluminum silicates with a platy structure. They are mainly used in their blocky calcined form for antiblocking. Calcination modifies the natural hydrous kaolin surface chemistry, making it less reactive and more compatible with the PE matrix.

Imerys InFilm® and PoleStar® grades are highly refined, medium particle size calcined kaolins which offer a good, cost-effective balance of antiblocking, haze and clarity performance.

Calcined kaolin provides a good, cost-effective balance of antiblocking, haze and clarity

Talc

Talc is an excellent solution for providing enhanced mechanical properties and antiblocking.

Imerys’ Mistroblock® talc for antiblocking is based on unique microlamellar talc ore. Unlike conventional talc morphology, microlamellar talc is composed of conglomerates of block-like shaped particles with a high specific surface area.

Mistroblock®:

  • Improves the mechanical properties of the film compared to other anti-block minerals
  • Provides better optical properties than conventional, lamellar talc ore.

SEM Mistroblock
Microlamellar talc provides an optimum balance of mechanical properties, antiblocking and haze

We offer a full range of bespoke formulation and technical and process support services to help you match the right mineral grade to your application requirement.

Please contact us, we will be only too happy to help

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Plastics