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How natural fibre composites can degrade
April I997
Additives for Polymers
alkylamine analogues, with aromatic and aliphatic phosphites, was examined in polyprotheir photostabilizing pylene, comparing performance with that of the individual stabilizers. Combinations of a hindered aryl phosphite with either a secondary or tertiary HALS or the corresponding nitroxyl radical analogue generally showed antagonism when used to protect PP against UV irradiation, and the level of antagonism decreased as the molar proportion of phosphite was increased. The aliphatic phosphite TLP showed a synergistic effect in combination with a hindered amine (but this was examined at only one molar ratio). A better photostabilizing performance was shown by the bifimctional HALS-Phosphite and HALS-Phosphonite antioxidants, in comparison with the corresponding hindered aryl phosphite and HALS combinations, at the same molar concentration as the total antioxidant combinations. Polymer Degradation (1997) l-7
and Stability No. 55
How natural fibre composites can degrade As interest grows in the use of natural fibres for reinforcement of composites, on grounds of their biodegradability, much work is being done on (a) measuring the technical performance of the fibres and (b) seeking to imSome properties. composite prove interesting work on jute composites, carried out by the Institute of Nuclear Science and Technology, Bangladesh, is now reported in a paper published in Polymer Degradation
and Stability. But, while the fibre reinforcement might be degradable, there is not much to be gained if the polymer matrix is not degradable. Matrix formulations based on a urethane backbone oligomer have been developed, with monomers of different mnctionalities plus fillers, additives and co-additives. The paper describes preparation of a degradable jute/ 10
plastic composite with a matrix of a urethane acrylate prepolymer in the presence of some plasticizers and monomers of different glass transition temperatures. The jute was in the form of hessian cloth (purchased in a local market), which was then coated with formulated solutions and irradiated by ultra-violet. Tensile properties and elongation at break were measured, showing that tensile strength was increased with each successive pass of the coated cloth under the UV source (up to 80% x four passes) and elongation at break increased to a maximum of 200% at three passes. Under a simulated weathering test, the tensile strength fell by up to 55% and elongation by lo%, against uncoated specimens which recorded 60% tensile loss and 55% loss of elongation. To study degradation, the coated composite specimens were kept in soil, water, mud (33% water) and semi-mud (22% water), for up to 150 days. Loss of tensile strength ranged from 5-l 5% in soil and 5-l 8% in water, but was greatly increased in muds, depending on the water content. Loss of elongation followed a similar pattern. The study indicated that the jute/plastic composite is quite durable in water, soil and normal environmental conditions but can be easily decomposed by burying it in full mud. Polymer Degradation (1997) l-7
and Stability No. 55
MEETINGS The changing world of high-performance pigments The changing world of high-performance pigments is the title of an international business development conference, third in the series, to be held in Chicago, USA, on October 20-22 1997. Organised by Intertech Conferences, Portland, it will cover how the processing and application properties of 0 1997 Elsevier Science
Additives for Polymers
alkylamine analogues, with aromatic and aliphatic phosphites, was examined in polyprotheir photostabilizing pylene, comparing performance with that of the individual stabilizers. Combinations of a hindered aryl phosphite with either a secondary or tertiary HALS or the corresponding nitroxyl radical analogue generally showed antagonism when used to protect PP against UV irradiation, and the level of antagonism decreased as the molar proportion of phosphite was increased. The aliphatic phosphite TLP showed a synergistic effect in combination with a hindered amine (but this was examined at only one molar ratio). A better photostabilizing performance was shown by the bifimctional HALS-Phosphite and HALS-Phosphonite antioxidants, in comparison with the corresponding hindered aryl phosphite and HALS combinations, at the same molar concentration as the total antioxidant combinations. Polymer Degradation (1997) l-7
and Stability No. 55
How natural fibre composites can degrade As interest grows in the use of natural fibres for reinforcement of composites, on grounds of their biodegradability, much work is being done on (a) measuring the technical performance of the fibres and (b) seeking to imSome properties. composite prove interesting work on jute composites, carried out by the Institute of Nuclear Science and Technology, Bangladesh, is now reported in a paper published in Polymer Degradation
and Stability. But, while the fibre reinforcement might be degradable, there is not much to be gained if the polymer matrix is not degradable. Matrix formulations based on a urethane backbone oligomer have been developed, with monomers of different mnctionalities plus fillers, additives and co-additives. The paper describes preparation of a degradable jute/ 10
plastic composite with a matrix of a urethane acrylate prepolymer in the presence of some plasticizers and monomers of different glass transition temperatures. The jute was in the form of hessian cloth (purchased in a local market), which was then coated with formulated solutions and irradiated by ultra-violet. Tensile properties and elongation at break were measured, showing that tensile strength was increased with each successive pass of the coated cloth under the UV source (up to 80% x four passes) and elongation at break increased to a maximum of 200% at three passes. Under a simulated weathering test, the tensile strength fell by up to 55% and elongation by lo%, against uncoated specimens which recorded 60% tensile loss and 55% loss of elongation. To study degradation, the coated composite specimens were kept in soil, water, mud (33% water) and semi-mud (22% water), for up to 150 days. Loss of tensile strength ranged from 5-l 5% in soil and 5-l 8% in water, but was greatly increased in muds, depending on the water content. Loss of elongation followed a similar pattern. The study indicated that the jute/plastic composite is quite durable in water, soil and normal environmental conditions but can be easily decomposed by burying it in full mud. Polymer Degradation (1997) l-7
and Stability No. 55
MEETINGS The changing world of high-performance pigments The changing world of high-performance pigments is the title of an international business development conference, third in the series, to be held in Chicago, USA, on October 20-22 1997. Organised by Intertech Conferences, Portland, it will cover how the processing and application properties of 0 1997 Elsevier Science