Cold ring fraction

Figure 9. GC-MS chromatogram of the collected cold-ring fraction from the virgin unfilled elastomer showing a series of cyclic siloxanes from Dg to D21.

The total products may be conveniently separated into four fractions for separate analysis, namely, permanent gases, products volatile at 20°C, products volatile at degradation temperatures but involatile at 20°C (chain fragment or "cold ring" fraction) and residual polymer. 

Isothermal studies were also undertaken at various temperatures. At 365, 385 and 405 °C, acetaldehyde was observed to be the main component of the degradation. CO2, CO, and methane were formed, along with the other volatile components the amounts, though small, increasing with run temperature. For the cold ring fractions, only cyclic trimer was noted at 305 °C, but in the higher-temperature runs a range of products was obtained, similar to those observed for... 

Two cold ring fractions were obtained. The upper fraction contained benzoic acid, terephthaldehydic acid, terephthalic acid, mono-3-butenyl terephthalate, butylene terephthalate cyclic dimer, and H0(C=0)Ph(C=0)0(CH2)40(C=0)Ph(C=0)0H. The lower cold ring fraction consisted of short-chain fragments containing anhydride groups. 

Solid materials captured as a cold ring fraction, i.e., products which condense in the upper part of the apparatus and do not reach the traps included to catch more volatile materials, were ... 

An advantage of tva over many other methods is that the volatile products are not destroyed by the pressure analysis but are trapped in their respective cold traps from which they can be recovered for analysis by conventional spectroscopic methods. At the same time, both residue and cold-ring fractions can be collected for analysis. 

TVA has been used mainly for the study of the basic degradation patterns of depolymerisation [910,942]. McNeill et al. [949] have studied thermal degradation of PS and PS/IDBPby means of TVA, SATVA and GC-MS. In the presence of 4,4 -isopropylidene-bis-(2,6-dibromophenol) (IDBP), the main products were similar, except for propiophe-none and phenylpropanoyl bromide in the presence of IDBP. Similarly, TG and TVA have been used to study the thermal stabilities of PET, PBT and PDMT [950]. In this case, the amounts of the main product fractions (residue, cold ring fraction, volatile products) have been determined quantitatively and the various materials present in the volatile and cold ring fractions have been separated and identified. McNeill et al. [939] also fractionated PVC/DOP by... 

Ammonium polymethacrylate shows unique degradation behaviour in this group of materials. It undergoes a two-stage decomposition, in the first stage of which NH3 and H2O are eliminated in a cyclization. At higher temperatures cold ring fraction products, isocyanic acid, HCN, CO2, CO and CH4 are formed. 

In styrene rich styrene/MMA (S/MMA) copolymers, the stability is intermediate between that of the two homopolymers, but the product distribution is strongly influenced by the presence of the MMA units. For example, in a 4/1 S/MMA copolymer, the yield of cold ring fraction products is about a third of that expected on the basis of the styrene content and the behaviour of PS, so that transfer reactions are considerably reduced. ... 

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