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Degradation studies of polyurethanes based on vegetable oils. Part 2. Thermal degradation and materials properties

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Mohd-Rus, Anika Z., Kemp, T. J. and Clark, A. J.. (2009) Degradation studies of polyurethanes based on vegetable oils. Part 2. Thermal degradation and materials properties. Progress in Reaction Kinetics and Mechanism, Vol.34 (No.1). pp. 1-41. ISSN 1468-6783

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Official URL: http://dx.doi.org/10.3184/146867809X425749

Abstract

Polyurethanes (PUs), produced by cross-linking with a di-isocyanate hydroxylated vegetable oils (rapeseed and sunflower), have been examined from the viewpoints of their thermal degradation and their materials properties, and how both of these aspects are influenced both by the addition of TiO2 filler and by UV irradiation.

The thermal decomposition of the PUs was investigated using thermal gravimetric analysis (TGA) and IR spectroscopy: the decomposition of a foam of the PU based on rapeseed oil showed complex kinetics, being apparently single-stage and of the first order at 973 K but with at least two separate stages at other temperatures. Thermolysis of PUs as films resulted in the production of carbonyl groups (nu 1793cm(-1)) suggesting formation of an acid anhydride. Pyrolysis in vacuo produced volatiles which could be separated and examined by IR and NMR spectroscopy. Reaction mechanisms for the thermal decomposition of the PUs are proposed.

The materials properties of the PUS, with and without TiO2 filler, have been examined by differential scanning calorimetry (DSC), dynamical mechanical thermal analysis (DMTA), tensile testing and measurement of scratch resistance and Shore D hardness. Addition of TiO2 improves systematically the scratch resistance and hardness of the PUs, but the glass transition temperature T-g showed a more complicated dependence oil the TiO2 loading, initially falling and then increasing. Prolonged UV irradiation of TiO2-loaded samples increased the value of T-g at all loadings, suggesting increased levels of cross-linking on irradiation. The most dramatic effect of adding TiO2 was on the shape of the stress-strain curves: at 10% loading clear 'soft-but-tough' behaviour is evident. The values of tan delta and the storage modulus are also strongly affected by addition of TiO2, with and without UV-irradiation.

From the viewpoint of utilisation of these PUs, their thermal stability Lip to 350 degrees C and the beneficial effects of adding TiO2 make them promising materials.

Item Type:

Journal Article

Subjects:

Q Science > QD Chemistry
T Technology > TP Chemical technology

Divisions:

Faculty of Science > Chemistry

Library of Congress Subject Headings (LCSH):

Polyurethanes, Vegetable oils, Polymers -- Deterioration, Calorimetry, Thermogravimetry

Journal or Publication Title:

Progress in Reaction Kinetics and Mechanism

Publisher:

Science Reviews 2000 Ltd