Moisture absorption temperature influence

Comfort. In the past, the evaluation of fabric or garment comfort has been a subjective process influenced by such variables as temperature, insulating efficiency, moisture absorption, drying speed, softness, bulk, fabric constmction, and air permeability. Human factors must also be considered. 

Key properties required of the polymer system before application are acceptable pot life compatibility with other components and viscosity, cure time, and temperature suitable for particular applications. After application and curing, the coatings should have low moisture absorption, low moisture permeability, and good resistance to other outside influences that may tend to deteriorate the performance of the device. 

The dielectric properties of these foams are not only influenced by the foam density but also by moisture absorption and temperature effects. A single scouting experiment showed, that the increase of the dielectric constant due to heating to 100°C is small in comparison with the density dependency (a 45.7 kg/m3 foam sample was heated from 22°C to 100°C, the dielectric constant at 1 kHz. increased from 1.065 up to 1.071). ... 

Nearly all properties mentioned under group A are influenced by the temperature locations of the Tg/Tm values and the crystallinity level (Hf-value). The Tm-value and the thermal stability determine together the polymer s processing window. The moisture sensitivity, finally, is important in connection with the barrier properties of a polymeric system. Furthermore moisture absorption influences several physical properties considerably (see chapter 5.2). 

It will be clear that the mechanical properties of polyketones at ambient temperatures are sensitive for these ageing and these moisture absorption effects especially due to the presence of the glass-rubber transition in that temperature region. The influence of both effects is in general opposite to each other the stiffness increases due to ageing and decreases due to moisture absorption. Moisture absorption effects are time and object dimensions dependent whereas ageing effects are only time dependent. 

The dielectric losses at temperatures below Tg are shifted to a higher level due to the moisture absorption. Remarkable, however, is that the intensity of the dielectrically measured y-relaxation as such is practically not influenced by the samples moisture content. Dynamic mechanically, a strong influence of the moisture content on the intensity of the y-relaxation was measured, see Figure 9.9. 

Temperature and Moisture Properties. Thermal treatment and moisture affinity significantly influence the physical properties of nylon fibers and fabrics. The absorption of water causes the fiber to swell, which alters its dimensions and in turn changes the size, shape, stiffness, and permeability of yams and fabrics. It also alters the frictional and static behavior of yarns in mill processing as well as the performance of fabrics during use. Water, a powerful plasticizer for... 

This property is related to decomposition temperature and adhesion between material components. Thermal expansion and moisture absorption can also influence results. In multilayer PWBs, the treatment of the internal copper surfaces is also critical, among other factors. 

Glass-reinforced polyamides (nylons) are available with various glass concentrations in types 6. 6/6,6/10, 6A2,11, and 12. The glass reinforcement (1) increases strength, dimensional stability, deflection temperature, and stiffness and (2) lowers water absorption while retaining abrasion and solvent resistance. With the exception of nylons 11 and 12, nylons are hydroscopic with moisture absorption influencing their properties and characteristics. 

During application, plastics are exposed to ambient conditions where temperature and humidity vary. This combined effect, known as the hygrothermal effect, may influence the mechanical properties of plastics. The properties of glass fiber-reinforced plastics are more affected by this combined influence than by one of the two factors alone. Moisture absorption in reinforced materials is mainly characterized by diffusion. The capillary effect and transport along microcracks is another way to absorb moisture. Moisture absorption by the latter two mechanisms is often a direct consequence of moisture absorption caused by hot and humid ambient conditions. 

The temperature, voltage, frequency, and duration of exposure to moisture have an influence on the electrical properties. For example, the a-c characteristics of water (2) are illustrated in Figures 43 and 44. At low frequencies, the loss (Fig. 43) appears to be ionic. A dipole absorption peak appears at very high frequencies. The ionic loss is increased by a dissolved ionizable salt, but the dipole peak seems to be unaffected. The dielectric constant of water (Fig. 44) is very high until a sudden decrease takes place around the absorption peak just above IQio Hz. 

The influence of irreversibly adsorbed layers on plasticization due to moisture adsorption was investigated in PVAc ultrathin films with different contents of moisture. In order to obtain an equilibrium value of absorbed moisture, PVAc films were kept at fixed conditions of ambient humidity and temperature for at least 4 h before each measurement This time was considered sufficient to reach the equilibrium of the moisture absorption process. In fact we have verified that the time needed to reach the equihbrium state in bulk PVAc upon humidity exposure is about 4 h for grains with average diameter of about 1 mm. It is expected that this time should be much shorter for ultrathin PVAc films due to a larger fraction of surface area to volume in an ultrathin film compared to the bulk sample, and to its smaller thickness. 

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