Plasticisation, carbon dioxide

Poly(vinyl halides) - The photocatalysed oxidation of PVC has been undertaken in the presence of titanium dioxide and zinc oxide pigments and the extent of dehydrochlorination measured. Acetic and formic acids were major products along with carbon dioxide. Copper(II) dialkyldithiocarbamate complexes are also sensitisers. Photodegradable PVC has also been developed by grafting with benzophenone chromophores. Plasticised PVC also degrades and discolours on irradiation but this is due mainly to the plasticiser. ... 

For poljmrethane (PU) systems, water (or traces of hmnidity) can be used as the foaming agent. Directly injected liquid carbon dioxide is also used as a foamer, as well as a plasticiser. After release of the pressure constrainer of the system, the carbon dioxide boils, causing the polymer to foam [13]. 

Sodium bicarbonate, with or without citric acid, is a blowing agent that decomposes endothermically at 150-230 °C. It is suitable for polystyrene, ABS, polyamides, the polyolefins and rigid PVC, but not plasticised PVC. The gases evolved include carbon dioxide and water, so there can be a rust problem with metal moulds. The type of foam obtained with sodium bicarbonate usually has a coarse structure, although tests with different manufacturers products, all using bicarbonate/citric acid as the active ingredient, show considerable differences in cell and foam density. 

Nerin and co-workers [26] examined the applicability of SEE for the extraction of several paper and board samples of different composition, including virgin and recycled fibre. They optimised the SEE using carbon dioxide for the extraction of contaminants in 15 samples of recycled paper and board. An experimental design was used for simultaneous optimisation of the variables involved in both the extraction step and the collection of the extract. Methanol was used as modifier. Several plasticisers such as diethyl phthalate, diisobutyl phthalate, di-w-butyl phthalate, dioctyl adipate, and DEHP (from 2 to 100 pg/g of paper) were found in the recycled samples. A discriminate analysis applied to all results obtained, allowed them to classify the samples in three different groups according to the content of recycled pnlp (0, 10-30, and >80% of recycled pulp), the sample thickness (from <300 to >600 pmj, and the snrface treatment of the paper. 

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