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Plastic Additives
Lou Kattas
Project Manager
Fred Gastrock
Senior Research Analyst
Inessa Levin
Research Analyst
Allison Cacciatore
Research Analyst TownsendTarnell, Inc. Mount Olive, New Jersey
4.1 Introduction
Plastic additives represent a broad range of chemicals used by resin manufacturers, compounders, and fabricators to improve the properties, processing, andperformance of polymers. From the earliest days of the plastics industry, additives have been used initially to aid these materials in processing and then to improve their properties. Plastics additives have grown with the overall industry and currently represent over $16 billion in global sales.
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4.2Chapter Four
4.2 Scope
This chapter includes all of the major chemical additives for plastics that are consumed worldwide. Materials excluded from the scope of this chapter include fillers, reinforcements, colorants, and alloys.
4.2.1 Definitions
To ensure understanding we will define the terms additives and plastics.
Additives. Plastic additives are comprised of an extremely diverse groupof materials. Some are complex organic molecules (antioxidants and light stabilizers for example) designed to achieve dramatic results at very low loadings. At the opposite extreme are a few commodity materials (talc and glyceryl monostearate) which also can impart significant property improvements.
Adding to this complexity is the fact that many varied chemical materials can, and frequently do,compete in the same function. Also, the same material type may perform more than one function in a host plastic. An example would include the many surfactant type materials based on fatty acid chemistry which could impart lubricant, antistatic, mold release, and/or slip properties to a plastic matrix, depending upon the materials involved, loading level, processing conditions, and application.Given the range of materials used, plastic additives are generally classified by their function rather than chemistry.
Plastics. Plastics denotes the matrix thermoplastic or thermoset materials in which additives are used to improve the performance of the total system. There are many different types of plastics that use large volumes of chemical additives including (in order of total additiveconsumption): polyvinyl chloride (PVC), the polyolefins [polyethylene (PE) and polypropylene (PP)], the styrenics —[polystyrene (PS) and acrylonitrile butadiene styrene (ABS)], and engineering resins such as polycarbonate and nylon.
4.3 Antiblock and Slip Agents
4.3.1 Description
Antiblocking agents. Antiblocking agents function by roughening the surface of film to give a spacing effect. Theinherent tack of linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE) is a detriment when used in film where self-adhesion is undesirable. An antiblock additive is incorporated by the compounder to cause a slight
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surface roughness which prevents the film from sticking to itself.Years ago, efforts were made to prevent this by dusting the surface with corn starch or pyrogenic silica. This process was abandoned because of potential health concerns. Antiblocking agents are now melt-incorporated into the thermoplastic either via direct addition or by use of a master batch.
Antiblocking agents are used in polyolefin films in conjunction with slip agents in such consumeritems as trash bags, shipping bags, and a variety of packaging applications. The most common polymers extruded into film include LLDPE and LDPE. Lesser amounts of high-density polyethylene (HDPE) are used for these as well as other film applications. PE resins are used in film for their toughness, low cost and weight, optical properties, and shear sealability. Four criteria are used in the selection...