Ultra Violet Curing Of Rubberwood Fibres - Unsaturated Polyester composites
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Date
2005-01
Authors
POO PALAM, KOSHEELA DEVI
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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