Grafting of caprolacton to cellulose acetate by reactive processing

Cellulose acetate was successfully modified with caprolacton in an internal mixer at temperatures between 120 and 220 °C, and reaction times between 5 and 45 min in the presence of tin-octoate catalyst. The efficiency of modification and the structure of the product were analyzed by SEC, 1H NMR, and FTIR spectroscopy. Significant modification of cellulose acetate did not occur at low temperatures, below 180 °C. Grafting efficiency increased with increasing temperature and time. The extent of grafting could be estimated from the amount of material extracted from the samples by toluene and by FTIR analysis, from the relative intensity of -CH2- and -CH3 vibrations. The amount of polycaprolacton homopolymer is relatively low at the end of the reaction; the efficiency of grafting is good. Although high temperature and long reaction time favor grafting, considerable degradation of the product occurs under these conditions. Quantitative analysis showed that the average length of grafted oligomeric caprolacton chains is around 3 monomer units. The chains attached to the CA backbone internally plasticize the polymer leading to a considerable decrease of its glass transition temperature.