Ultra Violet Curing Of Rubberwood Fibres - Unsaturated Polyester composites

Loading...
Thumbnail Image
Date
2005-01
Authors
POO PALAM, KOSHEELA DEVI
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
This research project was carried out to study the physical and mechanicai properties of value added bic-fibre composites made by employing environmentally benevolent ultra violet (UV) curing technique. Standard mercury UV lamp was used for the investigation. Unsaturated polyester resin along with bisacylphosphine oxide was used as polymer matrix. Rubberwood fibre (TMP fibres) residues, a waste and un utilized fibre from one of the medium density fibre board (MDF) plants, were used as reinforcement fibres. Un-delignified TMP fibre mats could not be impregnated due to its high bulk factor. Improper cure of the composites was also expected due to the presences of lignin in the fibres. To overcome this problem and to enhance the interfaci21 adhesion between the matrix and fibre, anthraquinone-kraft (AQ-kraft) pulping known for its efficiency in the removal of lignin and for producing high strength fibre was adopted. Since the operating variables of pulping process control the ultimate strength of the fibre reinforcement, Response Surface Methodology (RSM) was employed to investigate the effect of the following pulping parameters (i) active alkali (ii) sulfidity (iii) temperature and (iv) time of cooking on the responses such as mechanical properties of composites, degree of cure, water absorption and thermal stability. Mathematical functional relations obtained for the analysis of the above data were used both to represent graphically as 3D surface response plots and perturbation plots. Optimum pulping conditions for maximizing the strength of composites were established by employing optimization with constraints. The optimum conditions are 17.0 % active alkali, 27.0 % sulfidity, 162°C pulping temperature and 95 minutes· of pulping time. Effect of percentage of photoinitiators (1.0- 4.0 %), fibre content (10-20 %) and the exposure time to UV (8-16 passes) on properties of these composites were studied under the above optimum condition. The mechanical properties of AQ-kraft pulped fibre composites showed properties superior to TMP fibre composites. Gel content and resistance towards water were better in AQ- kraft pulped fibre composites. Scanning electror. microscopy (SEM) studies were carried Gut on both the type of fibre compositEs to confirm above findings. Dynamic mechanical ~hermal analysis (DMT,l\) showed the peak of tan (5 (0.36 MPa) and Tg (115.09 °C) for AQ-kraft pulped fibre composites was lower than TMP fibre composites 0.50 MPa and 124.39 °C respectively. This was due to better mechanical interlocking between the fibres and the grafted unsaturated polyester in AQ-kraft pulped fibre composites. Increase in weight percentage of fibres ('10-20 %) in the composites decreased the tensile strength, flexural strength, impact strength and resistance towards water. The mechanical properties increased with increase of' photoinitiator percentage up to 3 % and then decreased. Besides normal UV lamp, UV lamp doped with gallium and indium was also employed. Composites cured with doped lamp required lesser exposure time (12 passes) and lower percentage of photoinitiators (2 %) to affect same degree of cure (98.44-99.46 %). However, the mechanical properties of the composites were found to be lower than those produced from standard UV lamp. AQ-kraft pulped fibre composites can thus be made by using standard UV lamp instead doped lamp and photobleaching photoinitiator, IRGACURE® 1800.
Description
Keywords
Ultra Violet Curing Of Rubberwood Fibres , Unsaturated Polyester composites
Citation