Additives and Compounding

Pure resins are rarely processed into final products without the addition of selected compounds, called additives, which are incorporated during the process of extrusion and molding of a plastic resin or applied externally on the formed material. Compounding refers to the process of uniformly mixing the additives into the resin. A blend, by definition, is formed from two or more polymer resins which have been mixed together. 

There are a variety of reasons for the use of additives in a resin, including (1) to improve the processing conditions, (2) to increase the resin s stability to oxidation, (3) to obtain better impact resistance, (4) to increase or decrease hardness, (5) to control surface tension, (6) to facilitate extrusion and molding, (7) to control blocking, (8) to reduce cost, and (9) to increase flame resistance. 

The number and amount of additives incorporated in a resin vary with resin type and application. A polyethylene resin, for instance, may have only an antioxidant incorporated, or a colorant may also be added. A PVC resin may require several plasticizers, a filler, a heat stabilizer, and a colorant. There are many variations, and in most cases, the final resin formulation is considered by the manufacturer to be proprietary information. A confidentiality agreement may be necessary to make certain that the material meets regulatory compliance, unless the supplier can give the end-user sufficient information to make the determination. 

Additives are incorporated by the resin manufacturer and/or by the packaging processor. The presence of additives in packaging applications raises the question of additive migration. Most additives diffuse within the polymer and often tend to migrate to the surface of the material. When a packaged product is in direct contact with a compounded polymer, there may be a transfer of the additive to the product. (Of course, it is also possible for components of the product to be transferred to the polymer.) The extent of transfer depends on a series of conditions, and is discussed in Chapter 13. We will briefly examine compounding, and then discuss some common additives used in packaging. 

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The increasing diversity of operations, new materials and processes and the constant demand for improved production efficiency can only be met by various additives and compounding agents being blended into the oil to enhance its performance. Additives tend to be expensive and the selection of enhanced cutting fluid is only justified by overall production economies. 

Information about the market introduction of new additives is easily accessible by means of various annual reports in Plastics Engineering (e.g. refs [75,76]), Modern Plastics International [77], Plastics Additives and Compounding (e.g. ref. [78]) or otherwise (Additives for Polymers, etc.), as well as regular conferences such as AddCon, AddPlast and SPE meetings. For business opportunities for 2002-2006, see ref. [79]. 

Plastics Additives and Compounding 6, No.2, March-April 2004, p.26-9 FLAME RETARDANTS EUROPEAN UNION RISK ASSESSMENTS UPDATE... 

Plastics Additives and Compounding 5, No.3, May-June 2003, p.46-9 ENVIRONMENTAL AND RECYCLING ISSUES FOR PLASTICS ADDITIVES... 

Plastics Additives and Compounding 3, No.12, Dec. 2001, p.12-5 ANTIMICROBIALS IN PLASTICS A GLOBAL REVIEW... 

Plastics Additives and Compounding 2, No.6, June 2000, p.16-21 COMPOUNDING FOR MEDICAL APPLICATIONS... 

Impact modifiers How to make your compound tougher, Plastics, Additives and Compounding, 6(3) 46-49, June 2004. 

New impact modifier offers cost and performance efficiencies, Plastics, Additives and Compounding, 11(2) 6, March-April 2009. 

Discuss the historical aspects of organometallic compound toxicity, including organoarsenicals used as pharmaceutical agents, gasoline antiknock additives, and compounds used in applications such as catalysis and chemical synthesis. 

D.T. Colbert, Plastics Additives and Compounding, January/ February 2003. 

Plastics Additives and Compounding 5, No.4, July-Aug.2003, p.30 NEW KNEADING CONCEPT FOR PVC COMPOUNDING... 

Plastics Additives and Compounding 5, No.2, March-April 2003, p.48-9 PVC PLASTICIZER ADDS VALUE TO WATERBEDS... 

Many coating polymers contain additives and compounding ingredients to improve the physical durability, flexibility and performance. Rubber coatings in particular usually include carbon black and inorganic fillers to improve physical properties or reduce costs. 

Plastics Additives and Compounding 4,No.l2,Dec.2002, p. 18-21 ANTIMICROBIAL PLASTICS ADDITIVES TRENDS AND LATEST DEVELOPMENTS IN NORTH AMERICA Maikarian J... 

Plastics Additives and Compounding 4, No.4, April 2002, p. 16-21 ADDITIVES IN FOOD PACKAGING... 

Reactions of Compounds and Sulfur-Additive Mixtures. When additives and compounds are used to retain sulfur in the positive electrode there are other possible reactions, in addition to the usual electrochemical reactions, that can take place at the positive electrode. These include electrochemical oxidation and reduction of the additive (or compound ) and interaction of the additive with the electrolyte. In addition, there is the possibility of ternary compound formation from a reaction between the discharge product, Li2S, and sulfur compounds. Because the arsenic—sulfur system has undergone the most intensive investigation for use in lithium—sulfur cells, examples of the aforementioned reactions using arsenic are shown below ... 

Materials free from leachable impurities, additives, and compounds remaining after polymerization and cross-linking... 

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