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Cellulose acetate (CA) with a degree of substitution of 1.7 was modified with caprolactone (CL) under various reaction conditions in an internal mixer. Processing temperature changed from 120 to 220 °C, while reaction time varied between 5 and 45 min. The composition and structure of the polymer was analyzed by various methods including FTIR, MALDI-TOF and NMR spectroscopy and its mechanical characteristics were determined by dynamic mechanical analysis and tensile testing. The results indicate that homopolymerization occurs under relatively mild conditions, while grafting requires higher temperatures and longer times. Grafted polycaprolactone (gPCL) chains are attached mainly to positions 2 and 6 of the glucose ring and their length increases with increasing reaction time and temperature, but the chains are always much shorter than those obtained in solution polymerization. Changes in the degree of substitution during grafting are small indicating that homopolymerization proceeds easier than grafting. Grafting seems to be easier in cellulose acetate with a larger degree of substitution in spite of the smaller number of active –OH groups present. Internal plasticization is more efficient than the external plasticizing effect of monomeric caprolactone. Plasticization results in a decrease of stiffness and strength, but deformability increases only slightly.

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, 1 H 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. 2005 Elsevier Ltd. All rights reserved.