Fibres with thermal insulation

Oji Shunsako, Fujimoto, Masanori Furata, Thermally insulating synthetic fibres with selective solar absorpting , JK1-132816. 

Acoustic insulation on the valve body and at least the first five pipe diameters downstream is an effective method of noise treatment to half the loss given in point 1. Note here, however, that the quality of insulation is very important. Although having no particular preference, the author has had reasonably satisfactory results with Refrasil insulation, a high temperature thermal and acoustic insulation made from basalt, glass fibre and silica which reduced... 

The PFM films may also be backed with a glass fibre reinforced polyurethane foam. This technology is already being used in thermoplastic roof modules and gives rise to parts having low weight, high stiffness and excellent thermal insulation. 

The main purpose of middle layers is to provide additional (thermal) insulation. Nowadays, these layers are often made of fleece materials with good air entrapment properties. Their thermal conductivity (typically 0.03-0.04 W/mK) is near from air (0.026 W/mK). The thermal resistance of such layers is directly correlated with their thickness, provided that no air movement occurs within the fabric. Thermal conductivity and air permeability also are generally dependent on the fabric density (Yip and Ng, 2008). Conduction has been shown to be the main heat transfer mechanism through textile layers as long as the fibre volume fraction is higher than 9% (Woo et al., 1994). However, materials with very low density (like spacer materials) allow radiant and convective heat transfer. This was demonstrated by Das et al. (2012) who compared a spacer fabric middle layer with two non-woven middle layers and showed that the contribution of this spacer fabric to the overall insulation was higher than the two other samples in a non-convective mode, while it was the lowest in a forced convective mode. The positive effect of metallised interlayers with low emissivity on the reduction of... 

Natural fibres, such as wool or cotton, have a curled or irr ular shape. Yams and fabrics made from these fibres are bulky and have a high thermal insulation and a pleasant grip and appearance. Many methods have been developed to give synthetic yams and fibres simUar properties. This is called texturisation. In texturisation processes unannealed yams or fibres are usually deformed by twisting, stuffing or knitting. They are then heat-set in the deformed state, which makes the deformation more or less permanent Most of those processes can be applied to split fibres but we shall only deal with techniques in which orientation effects play an important role. 

New materials and designs have been developed for heat protective clothing. For example, improved thermal insulation can be provided by non-wovens made with thin hollowed fibres, and can be made thermo-adaptive with two-way shape memory alloys such as nickel-titanium. Better thermoregulation inside the garment is sought with PCM, either encapsulated ° or incorporated in a matrix. Other solutions use external power, e.g., for liquid coolant circulation or with Peltier cells embedded in the textile. ... 

Since wind barriers are located at the cold side of the thermal insulation (in cold climates) they should combine a sufficient air and water tightness with a high vapour permeance. Materials which combine these properties and are often recommended as wind barriers are the spunbonded plastic films (also called house-wraps). These films are composed of rolled synthetic filaments (typically polypropylene or polyethylene fibres) that are welded together to form a continuous porous fabric. Measuring procedures and results of vapour transfer properties of spunbonded plastic films are reported in detail by Janssens and Hens [36]. The diffusion thicknesses of the films are a few centimetres and of the same order of magnitude as an air boundary layer. 

Wood fibres are produced in the form of chips, which is usually a waste material in the wood industry. Wood chips mixed with cement paste have been used since the 1920s for the production of sheets applied for thermal insulation in housing. The chips are subjected to chemical pre-treatment to avoid any disturbance of cement hydration by organic acids. The application of wood-origin fibres as a reinforcement for minor structural elements has been developing at a local level. 

Pause compared the thermal insulation effects of a batting (thickness 24 mm) of polyester fibre, outer fabric (0.2 mm) and liner fabric (0.1 mm) with... 

In another patent, production of thermally insulative fabrics from fibres comprising 98 parts nylon 6 and two parts Na stearate-treated a-type AI2O3 (AKP-30) particles with average particle diameter 0.4 pm has been disclosed. The mixture was melt spun at 250 °C, drawn, heat-treated at 165 °C, and made into a woven fabric with heat conductivity 2.4 x 10 " W/cm°C. 

Lightweight holiow fibre thermally insulating fabrics for winter clothing have been produced by Unitika. A composition containing 98 parts nylon 6 and two parts sodium stearate treated-a-AljOj particles (AKP-30) was melt-spun to form fibres with degree of hollowness 30%, drawn and made into woven fabric exhibiting heat transmission 1.6 x 10 " W/cm°C. 

Kuraray Co. Japan, Heat-storing, heat-insulating fibres with lasting thermal properties , JP 08,246,227, 24 Sep 1996, Chem. Abstr., 1996, 125, 331455m. 

Wood or plant fibres are of interest in polymer reinforcement for a number of reasons, espeeially their low cost, low weight and non-abrasiveness to proeessing equipment. In addition, natural fibres are C02-neutral when burned, have attractive aeoustic and thermal insulation properties and have good specific mechanical properties. The research literature contains many examples of studies in whieh the reinforcement of non-degradable thermoplastics like polypropylene (PP), polyethylene (PE), polyvinyl ehloride (PVC) and polyesters with wood or plant fibres has been investigated (Bledzki and Gassan, 1999 Kandaehar, 2002). Reinforcement of thermosets such as epoxies and polyurethanes with natural fibres has also been explored. A summary of the mechanieal properties of selected plant fibres derived from various literature sourees is shown in Table 8.1 (Lilholt and Lawther, 2000 Kandaehar, 2002 Bledzki and Gassan, 1999 Wambua et al, 2003). 

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