City Research Online

Abstract

An investigation has been made of the effectiveness of red phosphorus, used in conjunction with decabromobiphenyl and various nitrogen compounds, in conferring flame retardance and smoke suppression on some thermoplastic polymers (poly(vinyl chloride), polystyrene, poly(methyl methacrylate) and high-density polyethylene). Studies have also been made of the effects of other phosphorus-based additives, such as triethyl phosphate and tritolyl phosphate.

The Introduction opens with an account of the historical development and usage of synthetic organic polymers in some major countries . The hazards associated with polymer combustion and some common standard tests for measuring the flammability and smoke-forming tendency of polymers are described. General mechanisms of polymer combustion and techniques available for the study of polymer decomposition are then reviewed. Finally, an outline is given of some general principles and of different classes of compounds used to decrease flammability and smoke formation.

In the Experimental Section, the sources of the polymers and additives and the procedure used in the preparation of polymer-additive samples are described, followed by details of the apparatus and procedure used in the measurement of flammability and smoke production. An account is also given of the computer method used to fit polynomial functions to the flammability and smoke production data and to present the data in the form of triangular contour plots. The experimental set-up and procedure for making thermoanalytical and infrared spectroscopic measurements are then described, as is the procedure used in the preparation of polymer samples for microanalytical measurements.

The Results Section gives an account of measurements made of the flammability and smoke-forming tendency of polymers containing combinations of the various additives and the results are presented mainly in the form of triangular diagrams. With all the polymers studied, a greater-than-additive effect on flammability is observed with red phosphorus and melamine, red phosphorus and urea, and red phosphorus and guanidine carbonate. Two other nitrogen compounds, barbituric acid and benzotriazole were also used to help to elucidate the mechanisms involved. Finally, results of thermoanalytical, microanalytical and infrared spectroscopic measurements show the extent to which phosphorus is oxidised and the way in which the other additives break down.

In the Discussion Section, possible mechanisms are suggested to account for the effects of the additives on the flammability and smoke-forming tendency of the polymers. As regards flame retardance, decabromobiphenyl is found to act mainly in the gas phase, whereas red phosphorus functions principally in the condensed phase, by enhancing melting and dripping or char formation, or by stabilising the polymer. Melamine, urea and guanidine carbonate act mainly in the gas phase, by releasing ammonia which serves as a diluent. Mechanisms are also discussed for the phosphorus-bromine, phosphorus-nitrogen, bromine-nitrogen, and phosphorus-bromine-nitrogen interactions observed with some of the polymers.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science Q Science > Q Science (General) Q Science > QD Chemistry
Departments:	School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

Export

Downloads