Anti block additives are majorly used to reduce the process of blocking at a particular surface of films made of polymer and other plastic materials to ensure that the process of handling and processing these plastics are easier. An anti-block additive can be stated as a particle that is present in resin that protrudes microscopically from the surface of the film of polymer or plastic. This method also helps in creating little bumps also known as asperities that help in minimising the film-to-film contact of the surface(Marx &Wiesbrock, 2021). This also helps in increasing the gap between the two layers of polymer which results in reducing blocking. Adding an anti-block additive helps in reducing the coefficient of friction or the COF that is present in between the film-to-film layers of polymer or plastic.
The major utilisation of an anti-block additive is usually found in different industries that involve the process of packing and using polymer and plastic. Anti block additives are usually used in bags and films to avoid the sheets from sticking from each other. These are usually used to avoid the blocking of polyolefin films to avoid the effect of Van der Waals interaction. Anti block additives can be made up of both organic and inorganic substances. The organic substances include fatty acids, amides, fatty acid amides, silicones, salts of fatty acids and several others. The inorganic substances of an anti-block additive include talc, magnesium carbonate, anhydride or calcium sulphate, calcium carbonate, precipitated silica, feldspar, mica, calcined kaolin and several other inorganic products(Wu et al., 2020). In many situations, inorganic and organic substances are used to produce an anti-block additive. It has also been observed that inorganic additives have a better ability of anti-blocking when compared to organic additives.
How do anti-blocking additives work?
Blocking is considered a major problem by multiple manufacturers of polymers. Blocking can be stated as the adhesion of two layers that are adjacent in the nature of a film. Blocking is a natural phenomenon in polymers and is usually caused by the Van der Waals effect of polythene. These are forces that act between amorphous regions of the polymer leading to the chances of an increase of blocking. As the distance is between two layers, the forces increase leading to stronger effects of blocking(He et al., 2020).
Blocking can also be caused in polymers as a result of the presence of oligomers which are low molecular weight species that have the tendency to migrate to the surface of the polymer or the film. To combat the issues that are created by the process of blocking, anti-blocking additives are used in the manufacturing of polymers. An anti-blocking additive is usually used to increase the distance between both the surfaces of a polymer film which is done by creating asperities that are also known as little bumps that help in maximizing the distance between both the surfaces of a film. This process helps in minimising the impact of surface to surface contact with the increase in distance between one surface to another.
Different types of Anti-blocking additives
Anti-blocking additives have two major varieties: Organic and Inorganic
Organic anti-block additive: The organic anti-blocking additives are usually migratory in nature and have the tendency to crystallize on the surface of the film. This helps in forming interfering layers between the film layers that are adjacent to each other.
The organic anti-block additives are known to have an interest in films that have high clarity. The application of organic substances is usually costly and hence they are also used for films that need high clarity. For example fatty acids, amides, fatty acid amides, silicones, salts of fatty acids and several others.
Inorganic anti-block additive: These are substances that are non-migratory to the film surface and are usually used for applications that involve high temperature. This is so because these substances have the tendency to melt at much higher temperatures than the regular extrusion temperature of the polymer(Wypych, 2021).
For inorganic substances, the size of particles, the shape of the additive along the quality of dispersion has a major impact in determining the efficiency factors of anti-blocking of these substances.
The selection of inorganic additives completely depends on the thickness of the film. Inorganic additives are usually inexpensive when compared to organic additives and are best used for commercial purposes that involve their applications into commodities and high volume objects.
Some major examples of inorganic additives include mica, calcium carbonate, synthetic silica, talc, natural silica, clay or kaolin, ceramic spheres and many more.
The main applications of anti-block additives are usually in the plastic industry. The plastic industry has faced constant growth over the years and using antiblock additives as packaging fillers is the recent trend in the packaging market. The packaging and plastic industry has used antiblock additives in the manufacturing of plastic sheets to avoid the sticking of surfaces.
The application of anti-block additives is based on the thickness of the films and the kind of polymer that has been used and diverse use in paints and well as extrusion industry. (Zemtsova et al., 2020).
There is a constant increase in the demand for using antiblock additives in the various industries as it provides the opportunity to produce better quality films that are sustainable for the environment.
Q1. What are anti-blocking additives?
Ans: Anti-blocking additives are substances that help in reducing the blocking of polymer surfaces by increasing the distance between one surface to another of a polymer film.
Q2. How do anti-blocking additives work?
Ans: Anti-blocking additives are present in resin that microscopically protrudes from the surface of the film and creates little bumps also known as asperities that increase the distance between one surface of the film to another and reduces the coefficient of friction in the polymer.
Q3. What are types of anti-blocking additives?
Ans: The anti blocking additives exist in two major forms. Organic additives and Inorganic additives along with some other categories such asengineered silica, zeolites as well as common silica.Theymajorly differ in terms of anti-blocking capacity. The anti-blocking capacity is higher for inorganicadditives but the organic anti-blocking additives have better slip effect.
Q4. What is the major difference between inorganic and organic additives?
Ans: The major difference between inorganic and organic additives is that organic additives are migratory and are used for polymers that require high clarity whereas inorganic additives are non-migratory and are used for commercial purposes.