Polymer additives transformation products

For samples that meet the solubility requirements of the SEC approach, analyses were also reported for additives in polymers such as PVC and PS [28,29]. Direct SEC analysis of PVC additives such as plasticisers and thermal stabilisers in dissolution mode has been described [28,30,31 ]. In the analysis of a dissolved PS sample using a SEC column of narrow pore size, the group of additives was separated on a normal-phase column after elution of the polymer peak [21]. Column-loading capacity of HPSEC for the analysis of additives, their degradation products and any other low-MW compounds present in plastics has been evaluated for PS/HMBT, PVC/TNPP and PVC/TETO (glyceryl tri[l-14C] epoxyoleate) [31]. It was shown that HPSEC can be used to separate low-MW compounds from relatively large amounts of polymers without serious loss of resolution of the additives the technique has also been used for the group analysis of chlorohydrin transformation products of the TETO model compound [32]. 

Sucrochemistry is already more than 50 years old, and has become a field of carbohydrate chemistry on its own. Indeed, considerable progress has been achieved in the monitoring of the chemical reactivity of sucrose, with the efforts of many research teams who have built on the steps of a few pioneers. Many sucrose derivatives can now be prepared, and sophisticated synthons as well as simple substituted compounds have been reported. However, only a few examples have yet reached the level of the industrial development, and these are mainly in the field of food and cosmetic additives and surfactants. Various polymers, additives for materials, and some chemical intermediates have also been produced. Bioconversions are certainly a major avenue for using sucrose as a starting material, and ethanol production will increase as a consequence of high oil prices. Current awareness of the shortage of fossil resources emphasizes the potential for chemical transformations of sucrose in providing new uses of this abundant natural resource. 

Polymer stabilizers are very reactive systems. This is expressed not only in scavenging chain-carrying radicals or deactivation of ROOH but also in interactions between various stabilizers or their transformation products [250], This chemical cooperation may have a positive effect accounting for additivity or even synergism. Unfortunatelly, some interactions are negative, i.e. antagonistic, and should be avoided. 

The functional transformation is an integral part of the stabilization capacity of antioxidants and has to be considered in the discussion of relationships between structure and efficiency. The analyses indicate that it is impossible to elucidate the complex mechanism of action of antioxidants without the knowledge of chemical and photochemical properties of products. The transformation products are cum-mulated in a polymer und play a specific role in various stages of its ageing. In this complex process, compounds with initiation, retardation, or antioxidant properties may be formed from original antioxidants. These compounds participate in the integral stabilization capacity of the additive used under real degradation conditions. This fact explains the differences in overall properties found under different conditions. 

It is said to be highly efficient in small concentrations (100-300 ppm), especially with polyolefins. The effectiveness is due to the ability of the stabilizer and its major transformation products to deactivate alt damaging free radicals. Problems of polymer discolouration can be minimized by the use of co-additives, such as phosphite anti-oxidants. 

Thermoanalytical techniques are a quick way for assessing the relative performance of AOs in polymers, rubbers, lubricants, etc. and have been widely used. DSC-OIT is used to study base polymer stability, optimum additive level, the degree of material deterioration during processing and the effect of multiple shear histories while reprocessing. DSC is also useful to determine the effective AO concentrations among all the transformation products present in a polyolefin formulation. 

Purge-and-trap screening followed by off-line TD-GC-MS analysis of the collected adsorbent tubes was used to determine emissions from flame retarded polymers (in TV sets) [1011]. Volatile transformation products from additives in y-irradiated HDPE packaging were analysed by means of TD-GC-MS [1012]. Off-gassed C5-C30 polymer fractions can readily be GC analysed using a Carbo-trap 370 thermal desorption tube and a TD unit. 

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