Polymers and Additives

In a commercial plastics material there are also normally a number of other ingredients present and these may also be affected by the above agencies. Furthermore they may interact with each other and with the polymer so that the effects of the above agencies may be more, or may be less, drastic. Since different polymers and additives respond in different ways to the influence of chemicals and radiant energy, weathering behaviour can be very specific. 

Synthetic resins form the heart of the paint industry. The tw o main types of synthetic resins are condensation polymers and addition polymers. Condensation polymers, formed by condensation of like or unlike molecules into a new, more complex compound, include polyesters, phenolics.. iniino resins, polyurethane, and epoxies. Addition polymers include polyvinyl acetate, polyvinyl chloride, and the acrylates,... 

Recent work on thermoplastic vulcanizates (TPVs) will not be included in this chapter since it is being reviewed elsewhere in the book. Abbreviations for some mbbers and accelerators will be used throughout in place of their full names as shown in Table 11.1. Acronyms for other polymers and additives wUl be provided in the text as required. A short discussion of polymer miscibility and compatibUization of polymer blends will be provided for better appreciation of the subject. 

More recently, the same author [41] has described polymer analysis (polymer microstructure, copolymer composition, molecular weight distribution, functional groups, fractionation) together with polymer/additive analysis (separation of polymer and additives, identification of additives, volatiles and catalyst residues) the monograph provides a single source of information on polymer/additive analysis techniques up to 1980. Crompton described practical analytical methods for the determination of classes of additives (by functionality antioxidants, stabilisers, antiozonants, plasticisers, pigments, flame retardants, accelerators, etc.). Mitchell... 

Polymer/additive analysis then usually proceeds by separation of polymer and additives (cf. Scheme 2.12) using one out of many solvent extraction techniques (cf. Chapter 3). After extraction the residue is pressed into a thin film to verify that all extractables have been removed. UV spectroscopy is used for verification of the presence of components with a chromophoric moiety (phenolic antioxidants and/or UV absorbers) and IR spectroscopy to verify the absence of IR bands extraneous to the polymer. The XRF results before and after extraction are compared, especially when the elemental analysis does not comply with the preliminary indications of the nature of the additive package. This may occur for example in PA6/PA6.6 blends where... 

Unfortunately, extraction procedures are often elaborate and labour intensive since many of the polymer matrices are poorly soluble or insoluble. For this reason, substantial efforts have been directed towards additive analysis without prior separation from the polymer. Chapter 9 deals with direct methods in which such separation of polymer and additive can be omitted. Yet, this direct protocol still requires sample pretreatment (dissolution) of the polymer/additive system as before. 

Alternative approaches consist in heat extraction by means of thermal analysis, thermal volatilisation and (laser) desorption techniques, or pyrolysis. In most cases mass spectrometric detection modes are used. Early MS work has focused on thermal desorption of the additives from the bulk polymer, followed by electron impact ionisation (El) [98,100], Cl [100,107] and field ionisation (FI) [100]. These methods are limited in that the polymer additives must be both stable and volatile at the higher temperatures, which is not always the case since many additives are thermally labile. More recently, soft ionisation methods have been applied to the analysis of additives from bulk polymeric material. These ionisation methods include FAB [100] and LD [97,108], which may provide qualitative information with minimal sample pretreatment. A comparison with FAB [97] has shown that LD Fourier transform ion cyclotron resonance (LD-FTTCR) is superior for polymer additive identification by giving less molecular ion fragmentation. While PyGC-MS is a much-used tool for the analysis of rubber compounds (both for the characterisation of the polymer and additives), as shown in Section 2.2, its usefulness for the in situ in-polymer additive analysis is equally acknowledged. 

Direct and indirect analysis of polymers and additives using mass spectrometry has been reviewed [4,270], Kreiner [271] has described accelerator analysis. 

Analysis after separation of polymer and additive (in solution). 

Restricted selection of solvents (suitable for host polymer and additives and deformulation technique)... 

Staal et al. [15] have described the dissolution of polycarbonate and polysulfone in THF and precipitation on to a Cig guard column. Separation of polymer and additives was achieved using gradient elution from water-THF (50 50 vol. %) as nonsolvent to 100 % THF. The additives elute first, followed by the oligomers and polymer. 

Occasionally there is the need for simultaneous determination of MW, MWD of polymers and identifica-tion/quantilication of additives [38]. This was the case for polymer and additive analysis of SBR/(softeners, flavour agents, stabilisers) (chewing gum) [41]. The many constituents of the SBR portion of the sample were not resolved, since adjacent components were similar in size. It should be stressed, however, that the need for simultaneous determination of the molecular weight of polymers and the identification/quantification of additives is exceptional rather than the rule. The determination of molecular weight distributions by SEC has indicated that oligomer fractions analysed by dissolution and (Soxhlet) extraction methods may differ essentially [42],... 

Quite obviously, a disadvantage of the classical sample preparation technique, consisting of dissolving a sample in a solvent, which may eventually lead to volatilisation and degradation of the additives, is not totally eliminated (see Section 3.7). Actually, the solvent choice is more restrictive (Table 9.5). In fact, NMR for polymer/additive dissolutions is feasible only in cases of a common solvent for polymer and additives, compatible... 

For diffusion NMR, which is another approach to the separation of polymer and additive signals by application of field gradients, see Section 5.4.1.1. 

Progress in polymer/additive analysis has closely mirrored the changes in technology in both the polymer and additive industries during the past decades. Whilst the pharmaceutical and biochemical industries... 

In this respect, current state-of-the-art ends up in a draw. This book makes a substantial contribution to the current literature on the analytics of polymer additives, follows up an earlier industrial tradition and lays a foundation for the future. It will be of great value to a broad readership comprising industrial and academic (analytical) chemists, polymer scientists and physicists, technologists and engineers, and other professionals involved in R D, production, use and reuse of polymers and additives in all areas of application, including manufacturers, formulators, compounders, end users, government legislators and their staff, forensic scientists, etc. 

Before the polymer and additive can be mixed together, the compounder must first introduce the components into the mixing equipment. Since additives come in many different forms, either solid or liquid, and different shapes and sizes, the means of their introduction must be matched to the material being added. 

This is used to identify the polymer and additive types in rubber analysis. 

The majority of investigations reported in the literature report on the efficacy of a material as a flame retardant but do not address the chemistry that gives rise to this retardant effect. The objective of this work is to come to an understanding of the course of the reaction between polymer and additive and to use that understanding of chemistry to choose new additives. Since the purpose of this work is to identify the chemistry that occurs between the additive and the polymer, unusually large amounts of the additive relative to the polymer are used. This permits one to more easily determine the course of the reaction. 

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