tailieunhanh - Advances in Modern Woven Fabrics Technology Part 3

Tham khảo tài liệu 'advances in modern woven fabrics technology part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Smart Woven Fabrics in Renewable Energy Generation 29 Fibre extrusion and poling High purity PVDF polymer granules are fed a melt extruder. The extrusion temperature is kept at 195 C which is 20 C higher than the melting point of PVDF inside the feeding screw. The temperature is slightly higher at the die 205 C where the fibre is extruded. The extruded fibre is then air cooled with a blower and water cooled on the initial stage rollers which help in further cooling of the extruded fibre. Poling is a critical step for piezoelectric fibre generation. Temperature drawing ratio and applied electric field play a crucial role in the amount of polarisation. Highest polarisation charge coefficient was given in the literature Sessler 1981 Wegener et al. 2002 . The drawing of fibres takes place at the rollers which have heating coil inside to vary the temperature during stretching of fibres. The temperature of these rollers is maintained constant on PVDF fibre when it leaves the roller and an appropriate electric field applied on PVDF fibre while being drawn. Fig. 4. Piezoelectric polyvinylidene fluoride PVDF filament production via a continuous process using a melt extruder Figure 4 shows the continuous process of producing piezoelectric polymer in a customised melt extruder. This is a less expensive and less time consuming method for preparing piezoelectric polymer fibres in that all process variables are applied simultaneously. Detailed information on polymer based piezoelectric fibre production via a continuous process has been reported Siores et al 2010 . Testing of generated piezoelectric fibres Generated polymer fibres shown in Figure 5 are embedded in between two thin sheets of aluminium or copper which act as electrodes. The fibres are placed close to each other such that the top electrode would not contact the bottom one. The top and bottom electrodes act as positive and negative terminals for the energy generating polymer piezoelectric device. 30 .