Additive Used in plastics

The words polymers and plastics are often taken as synonymous but in fact there is a distinction. The polymer is the pure material which results from the process of polymerisation and is usually taken as the family name for materials which have long chain-like molecules (and this includes rubbers). Pure polymers are seldom used on their own and it is when additives are present that the term plastic is applied. Polymers contain additives for a number of reasons. The following list outlines the purpose of the main additives used in plastics. 

Additives used in plastics materials are normally classified according to their intended performance, rather than on a chemical basis (cf. Appendix II). For ease of survey it is convenient to classify them into... 

Applications Major application areas of LC-MS technology are pharmaceuticals (up to (LC-PDA-ESP)4-MS configurations), environmental protection (metal spe-ciation), food industry, biotechnology, petrochemicals and consumer products. Many of the additives used in plastics production are insufficiently volatile to be analysed by GC-MS, and are more readily analysed by LC-MS. Similarly, some oligomers are not readily... 

Table 3-1 Additives used in plastics for contact with food and related applications...

In a second step, the harmonisation of additives used in plastic food contact materials was started. However, this step is not yet finished Therefore, additives listed both in the Community legislation and in national legislation can be used in food contact plastics (for national lists see section 3.7). It is foreseen that harmonisation on additives will be finalised by 2007. Until 31 December 2006 all parties interested in additives authorised at national level have to supply EFSA with a valid application for evaluation of this additive. Only additives for which a valid application has been supplied may continue to be used according to national audorisation until evaluation is finalised by EFSA and a decision on authorisation is taken by the European Commission. The Community list on additives contains those additives that are used solely in plastics and those used both in plastics and coatings. However, it does not contain additives used only in plastic coatings, adhesives and epoxy resins. 

It is possible to use techniques in which the additives can be determined by direct analysis of the sample, such as nuclear magnetic resonance (NMR) spectrometry, ultraviolet (UV) spectrometry, and UV desorption-mass spectrometry. These techniques are very useful when the concentrations of additives in the polymer are high. However, when additives are present in trace levels, it is necessary to carry out a preliminary extraction/concentration step before analysis. Some of the most common additives used in plastics materials are presented in Table 1. 

Table 1 Common Additives Used in Plastic Products...

The discussion in this chapter does not cover all types of additives used in plastic foams. The following terms not discussed in any detail are defined as follows ... 

The topics to be covered in some detaU in this chapter are antistats, blowing agents, catalysts, fire retardants, mold-release agents, nucleating agents, reinforcements, stabilizers, and surfactants. These topics are presently in alphabetical order as a matter of convenience. The reader should be aware that there are a number of additives used in plastic foams that serve dual functions. These will be noted in the following text. 

The effects may be subtle and cumulative and may be noticeable only after a long time. Even the synthetic fibers or plastic goods used in clothing and sleepwear, as well as mattresses, may have minute effects on body and brain functions. Additives used in plastic containers or bottles are suspected to leach into the contents. For example, Disphenyl A, used in clear polycarbonate plastics such as in the lining of beverage cans, may mimic hormones. Not to mention the many electromagnetic... 

For this reason, heavy metals and metal ions that are used as additives in plastics and rubber (as colorants, stabilisers, plasticisers and so on) should be monitored carefully, and their use as well as the amounts used should be well known and regulated. In addition to their existence in some of the additives used in plastics and rubbers, toxic heavy metals most of which are considered chronic poisons, such as arsenic, lead, mercury, cadmium, nickel, zinc and chromium, are frequently encountered in industrial processing and other manufacturing operations (their main industrial sources include paint, ink, plastic, rubber and plastic film production, leather tanning, wood preserving, battery manufacturing, and so on). 

Some plastics additives, such as phthalates, bisphenol-A (BPA), and nonylphenols, present as plasticisers, can evaporate indoors and can be inhaled i.e., oestrogenic butyl benzyl phthalate is found in most vinyl floor tiles, adhesives, and synthetic leathers, and bisphenol-A is a breakdown product and plasticiser of polycarbonate (PC) mainly used as glazing material. In addition to plasticisers, there are also other additives used in plastics and rubbers i.e., stabilisers used in PVC window profiles and pipes are mostly lead-based, or they can be either barium/cadmium/zinc compounds. All of these can pose serious health hazards if they are above certain concentrations in the air, through evaporation from the system. Increase of temperature indoors speeds up this evaporation process. 

Most of the additives used in plastics and rubbers are toxic and during their production these are also considered as non-environmentally friendly. To have sustainable development with sustainable compounds, these additives should be replaced by their more sustainable counterparts. 

There are other additives used in plastics, but the ones discussed above are the most common. 

FIGURE 4.12 Major classes of additives used in plastics industry. 

Table 1 Common additives used in plastic products.

Some additives used in plastics are surfactants but are not used primarily for their surface or interfacial activity. Rather they contain functional groups that, because of their chemical nature, are polar but they also contain non-polar groups, such as hydrocarbon chains, in order to provide compatibihty with the polymer. Good examples are the heat stabilizers used in plastics such as PVC to prevent thermal degradation. Typical additives used for this purpose are soaps (metal salts of alkyl carboxylates) or metal salts of other organic acids such as phenols. The metal cations used most commonly are tin, calcium, barium, zinc and cadmium. Lead salts are also used in electrical cables, pipes and window frames. Tin salts are especially useful for stabilizing clear, rigid PVC bottles. 

Additives used in plastics packaging have to be judged by toxicologists who consider both human health and environmental protection. The legislation regarding the use of additives in food packaging in various countries varies under the specific conditions of each country [61]. 

Plastics are compounds made up of resins (polymers) and additives. Additives, which are used to obtain specific effects in the plastic material during fabrication or use, expedite processing, heighten certain properties, provide color, and furnish the needed protection during fabrication and use. Some of the key additives used in thermoplastic piping are heat stabilizers, antioxidants, ultraviolet saeens, lubricants, pigments, property modifiers, and fillers. Table 2.1 lists some of the main additives used in plastic piping materials and their purpose. 

Tliis new book on additives used in plastics for food contaa, can be seen as a con anion to the 1993 publication Spectra for the Identification of Monomers in Food Padazging [1, 2]. That earlier book presented information on monomeric substances listed in Directive 90/128/EEC [3], which restricts the range of monomers and other starting substances that can be used for the production of plastics materials and articles intended for food contact applications. 

EC Directive 90/128/EEC controls the safety of plastics food packaging materials by limiting through a positive list the substances permitted to be used as monomers and other starting substances for the production of plastics. After monomers the European Commission will regulate plastics additives. The additives used in plastics intended for food contact are listed in Commission working documents ( Synoptic Documents ). This project was started on the basis of Synoptic Document N. 5 and for the final selection of additives the Synoptic Document N, 7 [4] was used. 

Besides plasticizers and stabilizers, other additives used in plastics include other resins, minerals, dyes, fibers, biocides, processing... 

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