Additives anti-blocking agents

In addition, polyester bottles may contain colorants in the form of pigments, dyes or lakes. The colorants may be dispersed or dissolved in the polymer or may be covalently bound to the polymer backbone. Polyester packaging, which may be collected for depolymerization, may include nucleators for enhanced crystallization, anti-slip agents, branching agents, anti-blocking agents and anti-stats. 

Processing aids - additives such as viscosity depressants, mold-release agents, emulsifiers, lubricants, and anti-blocking agents (3). 

However, it is critically important to plasma clean a polymer for a sufficiently long time to remove all of the contamination from the surface. Almost all polymer films, and most molded parts, contain additives or contaminants such as oligomers, anti-oxidants, mold release agents, solvents, anti-block agents, etc. which are oils or waxes. Most of these are deliberately incorporated into the polymer formulation to improve its properties or manufacturability and are designed to bloom to the surface of the polymer and coat that surface. 

The problem is that almost all polymers have some contamination on the surface. This comes accidently fi-om handling or storage contamination, or, most importantly, fi om the diffusion of oily or waxy additives from the bulk polymer to the surface of the polymer. These additives can be antioxidents, anti-blocking agents, mold release, plasticizers, lubricants, etc. The diffusion of the additives usually cannot be stopped because they are designed to diffuse to the surface to perform their desired role. Unfortunately, when they reach the surface they cover-up the surface moieties left by the plasma treatment and the effects of that treatment may disappear. 

Multifunctional concentrate n. A plastic compound that contains high percentages of at least two of such additives as colorants, stabilizers, flame retardants, lubricants, antistatic agents, anti-blocking agents, blowing agents, fillers, etc, that will be diluted in base resin to provide a tailored compound with the desired final concentrations of the additives in the extruded or molded product. 

Anti-blocking agents reduce the tendency of layers of film to stick together in tightly wound reels or stacked sheets. The use of an anti-blocking agent may affect the performance of other additives (such as slip or anti-static). It is therefore important that a full evaluation is carried out to determine the suitability of combinations of additives. 

As many film formulations contain both anti-blocking agents and slip aids, combination products are sold by some silica manufacturers. The combination products consist of synthetic silica and a slip aid such as erucamide or oleamide. The combination products show additional benefits through more rapid development of slip and greater anti-blocking efficiency due to better dispersion of both additives. 

Anti-blocking agents may be incorporated into the polymer resin either by direct addition at the final concentration, or via a concentrate or master-batch that is added to barefoot resin to achieve the final concentration. 

Certain polymer substrates may also contain sliding (slip) agents, antistatic additives, anti-block additives or other components that may migrate to the surface if stored for long periods of time prior to the screen printing process. These additives and work-in-process delays can impair the adhesion of the screen ink to the substrate or cause poor printability. 

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