STUDYING THE DRYING CHARACTERISTICS OF FLAX FIBRE USING MICROWAVE-VACUUM HEATING

摘要

The natural fibres have proven to be an important alternative for reinforcing various thermoplastic and thermoset materials. But the hydrophilic nature of the fibre leads to poor adhesion between the fibre and the polymer matrices. To enhance the adhesion between polymer matrix and fibre, chemical treatment of the fibre is done. After these treatments, the fibre needed to be uniformly dried to minimum moisture content. Drying by conventional dryers at higher temperature usually results in overall quality loss due to surface drying and is also time consuming and energy intensive. In recent years, microwave has been effectively used for better bulk drying of biomaterials. In addition, use of vacuum to microwave heating offers all advantages of dielectric heating. A volumetric heat transfer mechanism coupled with drying in vacuum provides an ideal low-temperature drying technique resulting in better organoleptic quality. In this study, the drying characteristics of flax fibre were studied under microwave- vacuum condition. The drying experiments were conducted using four different process variables viz., microwave power (P), vacuum level (V) and time of drying (t). In order to select the appropriate drying curve equation, the drying data was fitted in three different models viz., Page model, single exponential model and approximation of diffusion model. The effects of the process variables on the drying and quality of flax fibre are presented and discussed.