Functional materials for thermo-regulating textiles

Abstract

To provide thermo-physiological comfort to the wearer textile materials should have some functional properties such as highly water vapor transmittable, water resistant, air permeable, IR transmittable and temperature sensitive gating textile to allow body heat to escape. Recently, the high consumption of energy directly leading to excessive emissions of greenhouse gas becomes an extremely wide attention due to extreme weather and global warming. To reduce the energy consumptions in space cooling and heating, thermo-regulating textiles would play a vital role by reducing air conditioning. In this study, functional materials have been developed to make thermo-regulating textiles to fulfill such requirements. This PhD project is mainly focused on four main parts. Firstly, a series of shape memory polyurethanes (SMPUs) was synthesized to coat on to the textile surface to make highly water vapor transmittable and water droplet resistant textile. The synthesized polymeric material can evaporate sweat (water vapor transmission approximate- 6500 g m-2 d-1 at 40°C) and transmit it from the body surface to the environment even in extreme weather conditions that require wind and rain proof (contact angle approximate- 115°)-. The coated fabrics could provide thermal insulation with lower permeability at low temperature or low relative humidity (RH), and high permeability at room temperature or above, or high relative humidity with its water-resistance property. Furthermore, polyurethane/silica aerogel composite membrane was prepared, which showed super evaporative and Radiative effects (can transmit approximate 98% of human body radiation) and which can facilitate the convection process of the human body. I also fabricated the sensitive membrane-based textile which can cool down the human body by releasing body heat. The developed material possessed robust mechanical properties (breaking strength approximate 26MPa) for the longevity of the material, high water evaporative (water vapor transmission approximate 1800 g m-2 d-1 at 40°C) ability and air permeability to provide comfort to the wearer. The developed textile can release most of our body heat. In addition, segmented polyurethanes (PUs) were synthesized using a two-step polymerization method and additional highly porous PU membranes were produced by the leaching technique, using highly water-soluble silica particles. A crucial discovery during this work was reducing the particle leaching time. To make a porous structure the particles were leached out from the PU matrix over five minutes through sonication. An investigation was conducted into the surface morphology of the porous PU (PPU) membrane using a scanning electron microscopy (SEM). The effects of different silica particle percentage ratios were investigated. Porous polyurethanes membranes have particular significance for various uses, e.g. laminated textiles, cell seeding, bio-materials, tissue engineering, etc. The fourth study was to synthesize liquid crystal elastomers (LCEs) and fabricated a plain weave structure by using a different composition of low-temperature LCEs filaments and radial shaped three dimensional printed films (diameter 2cm). The plain weave structure showed very interesting results like closing its pores at 32°C (RM82/RM257 (80:20)) and 39°C (RM82/RM257 (80:20)) and returning back to its original position at room temperature (23°C). The radial shaped films were incorporated into textile to see the flip open/close mechanism when temperature applied. This pore closing fabric and flip opening/closing textile would be used to thermal comfort to the wearer when surrounding temperature increased. Finally, the synthesized polyurethanes/polyurethane composite was unique to be applied for thermo-regulating textile applications due to its high water vapor transmitting ability including others body heat escaping ability. The time saving way of making porous polymer membrane by particulate leaching technique also very crucial, which is high water vapor transmittable and rain drop resistant membrane. Furthermore, LCEs filaments and film was prepared to make temperature responsive gating textile.