Additives in plastics

The separation of plasticizers and antioxidants in polymers poses similar problems to those discussed under the preceding section on oligomers. Some references therefore cover both types of component under the same separation conditions. 

Shepherd and Gilbert [41] examined a range of plastic additives on PL-Gel columns (500 + 2 x 100 + 50A) in tetrahydrofuran (1 mLmin ), using both refractometer and UV detection. The degradation of tris(nonylphenyl) phosphate stabilizer in heat-treated polyvinyl chloride was quantitatively measured, as well as its degradation product nonylphenol. The influence of polymer concentration in the analysis was investigated. 

The determination of dibutyl and diethyl phthalates in ethylcellulose rocket motor tubes is an interesting example of the elimination of interference by 

The determination of residual monomer is frequently required in the quality control of polymers, and may easily be achieved by SEC. Toluene diisocyanate (TDI) in a polyurethane was determined by Spagnolo [43] by derivatization of the sample with ethanol, followed by SEC. 

Taymaz [44] developed a direct method for TDI and diphenylmethane diisocyanate in polyurethanes by direct injection of the sample solution on to three-column system (500 +100 +100A) using methylene chloride (lmLmin ) with refractive index detection. A sample of crude MDI was shown to contain about 43% of unreacted MDI when examined by this method. 

Fillers, stabilisers and colorants can be inorganic or organic, and are added as part of identification, stability and durability, they must be non-leaching and meet health requirements. Some plastics products are required to keep moisture and air out of sensitive products and these are usually high-density plastics with low permeation properties. Some products require plastics with high permeability to allow air (oxygen) as part of product stability, e.g. anaerobic adhesives. Healthcare products require that some containers do not allow air or moisture to permeate the surfaces (bacteria or other micro-organisms) and in some extreme cases may require that the inside be coated with an inner layer of approved lacquer or other very low permeable material. 

Vinyl stabilisers can either be liquids or solids and formulated as single or mixtures into PVC products. They can be combinations of metal salts and organic additives added to improve shelf life, prevent degradation and control colour of finished products. Depending on the application, the stabiliser compositions are based on organometal salts of Sn, Ba, Cd, Pb, P, Ti, etc. Analysis of these salts is often required to provide certification that the metallic composition of the product agrees with established specifications of the products. 

polyolefin thermoplastics. Metal salts are added to plastics for one or more of the following reasons  

Major and trace levels of metal initiators or catalysts can be present, such as Al, Ti, Fe, V, Cr, Fe, Cu, Ca, Zr, B, K, Na, Li and others which originate from organometallic salts. Catalysts may also include oxides and acetals that coordinate with such metals as Co, Zn, P, Pb, Co, Mn, Ge and Sb. Some of these metal salts can be used in the trans-etherification or polymerisation reactions to manufacture a range of polymers, e.g. metal acetals. Catalysts also play an important role in the selective PET polymerisation reactions. 

Function of metal added to plastics Type Metal(s) detected 

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The ECPI approach has been adopted by the European Commission in their "Technical Guidance Document on the Risk Assessment of Notified New Substances" as the model for assessment of environmental exposure from additives in plastics. It is important to note, however, that due to the effect of ultraviolet degradation and microbial attack, a significant proportion of the emissions from flexible PVC consists of plasticizer degradation products. In these instances, therefore, the level of plasticizers appearing in the environment will be significantly less than indicated by the plasticizer loss data. 

Liquids. Liquids (33) are common forming additives in plastic, paste, and slurry processing. In plastic forming operations, the Hquid aids forming and serves as the binder/plasticizer for the system. In pastes and slurries, other additives are also dissolved or dispersed in the Hquid/solvent. Water is a good, inexpensive solvent that can be recycled. Organic Hquids such as alcohols are used to process water-sensitive materials and to dissolve water-insoluble forming additives, however, at considerably more expense. 

MASCiA, L., The Role of Additives in Plastics, Amold, London (1974)... 

Rosato, D. V., Role of Additives in Plastics Function of Processing Aids, SPE-IMD Newsletter, Nov. 1987. 

The liquefied plastic fraction is heated to over 400 °C. This leads to cracking of the plastic into components of different chain lengths. Gases count for 20%-30% and oils for 60%-70% they are separated by distillation. Any naphtha produced is treated in a steam cracker, resulting in monomers like ethylene and propylene that are recovered. Such monomers can be used to produce plastics again. The heavy fractions can be processed into synthesis gas or conversion coke and then be transferred for further use. At most 5% of the input is converted into a mineral fraction. It is likely that this consists mainly of the inorganic additives in plastics. 

T.R. Crompton, Chemical Analysis of Additives in Plastics, Pergamon Press, Elmsford, NY (1971). 

Most methods for the determination of additives in plastics come essentially under two headings, namely with or without sample preparation. The following eight analytical categories are thus distinguished ... 

Extraction of plasticisers and additives in plastic parts used in car production. 

Soxtherm can be used for a variety of substrates, such as plasticisers, and additives in plastics and rubber, fibre and textile coatings, colorants on textiles, fat in food, oils and lubricants, fertiliser coatings, etc. Specific reports are scarce. EPA method 3541 has adopted automated Soxhlet extraction [151]. 

The role of additives in plastics in the creation of low-permeability fluorinated layers is totally underestimated/ignored in the open literature. 

Antioxidants are used as additives in plastics, rubber, gasoline, lubricating oils, and food products. See autoxidation. 

Urea derivatives are an important class of carbonyl compounds and useful chemical intermediates in the synthesis of pharmaceuticals, agricultural chemicals, and dyes and they are also used as antioxidants in gasoline and additives in plastics [51-54]. 

Starch is an abundant, inexpensive polysaccharide that is readily available from staple crops such as com or maize and is thus is mostly important as food. Industrially, starch is also widely used in papermaking, the production of adhesives or as additives in plastics. For a number of these applications, it is desirable to chemically modify the starch to increase its hydrophobicity. Starch modification can thus prevent retrodegradation improve gel texture, clarity and sheen improve film formation and stabilize emulsions [108], This may, for example, be achieved by partial acetylation, alkyl siliconation or esterification however, these methods typically require environmentally unfriendly stoichiometric reagents and produce waste. Catalytic modification, such as the palladium-catalyzed telomerization (Scheme 18), of starch may provide a green atom-efficient way for creating chemically modified starches. The physicochemical properties of thus modified starches are discussed by Bouquillon et al. [22]. 

Expandable graphite GrafGuard GrafTech (the United States) FR additive in plastics (processing up to 200°C), foams, putties, and coatings... 

Riedel T (1990) Lubricants and related additives, In Plastics additives handbook, Gachter R and Muller H (Eds), Hanser Publishers Munich, pp 423-480. 

Mascia L, "The Role of Additives in Plastics", Edward Arnold Publishers Ltd, London, 1974. 

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