Antiblocking additives organic antiblocks

A reason for the use of multilayer films is to minimize the use of additives. Surface-active additives like slip, antiblock or antifog agents are used only in the outer layers of a multilayer film. The migration of the organic additives and their solubility in the polymers has to be considered. 

The detailed mechanism of how organic antiblock additives work is not yet understood. It is thought that a barrier layer is formed on the plastic film surface, thus inhibiting the two adjacent plastic film layers adhesion. Their usage is limited. Organic antiblock additives were partially discussed above and will not be further mentioned here. 

Antiblock additives can be divided into two classes inorganic and organic. Chemically inert, inorganic antiblock additives migrate to the film surface and partially stick out of the surface to create a microroughness of the film surface. Figure 1.21 illustrates this principle. 

Several inorganic fillers/organic additives, such as silica, talc, kaolin, CaC03, titania, zeolites, cross-linked acrylic copolymers, spherical silicon beads, and so on, are employed in the plastics/coatings industry to attain the desired blocking performance. Some of these fillers are discussed elsewhere in this book in terms of their primary function only amorphous silica forms (natural and synthetic), used for antiblocking, will therefore be discussed in this chapter. 

Additives used in final products Fillers aluminum hydroxide, calcium carbonate, clay, carbon nanotubes, magnesium hydroxide, montmorillonite, red phosphorus, quartz, silica, wood fiber, zinc oxide, zinc powder Plasticizers EVAC is used as plasticizer in PVC and PLA therefore it seldom requires plasticization Antistatics 2-methyl-3-propyl benzothiazolium iodide, alkylether triethyl ammonium sulfate, organic amide Antiblocking tty amide, laponite, silica Release methylstyryl silicone oil Slip eru-camide, oleamide, stearamide Thermal stabilizer BHT ... 

Properties and performance of inorganic antiblocking additives are not affected by solubility but this is the only exception. Organic antiblocking, release, and slip additives perform in accordance with their solubility in systems into... 

According to the principles of action and application, the organic antiblocking, release, and slip additives are ... 

Figure 10.9 shows some data on blocking performance of organic antiblock-ing/slip additives.Stearamide is a very efficient antiblocking agent. 

Some of the above influences, such as pore volume and interaction between additives, are related to inorganic antiblocks and others, such as time after processing, material thickness, and transfer of surface components to other materials, are characteristics of organic additives. The parameters from the above list are discussed in the same order below. 

Figures 9.1 and 9.2 illustrate the effect of pore voliune on blocking force and the coefficient of friction. Figures 8.4 and 8.5 show data illustrating interaction between inorganic and organic additives. The associated text explains the influence of antiblocking agents on the performance of migrating antiblocking/slip additives. Optimization of performance of these two t3 es of additives is one of the main goals of research papers. " An experimental equation was proposed to accoimt for these influences ...

Most organic chemical materials used in antiblocking, release, and slip additives have low toxicity and volatihty (solvents were almost completely eliminated from release agents). The most important danger comes from particulate materials and among those fi om silica. The following recommendations are given by NIOSH/OSHA for the selection of respirator for amorphous silica ... 

The dispersion and incorporation processes of fillers and antiblocking additives are discussed in other sources. Organic antiblocking and slip additives, solids of low melting temperature, can be mixed with other components of formulation without any special difficulties, but they are usually incompatible with polymers and as such may easily separate or form concentration gradients if left without mixing. For this reason the process of their addition must include homogenization just before material formation into its final shape. 

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