Nylon mechanical studies with

Another study by Hong et al. also reports the preparation of conducting PANI/nylon-6 composites with high electrical conductivity and superior mechanical properties, such as flexibility and lightness [24]. PANI was chemically polymerized on the surface of the nylon-6 electrospun nanofiber webs. The electrical conductivity measurements showed that the conductivity of the PANI/nylon-6 composite electrospun fiber webs was superior to that of PANI/nylon-6 plain-weave fabrics because of the high surface area/volume ratios. The volume conductivities of the PANI/nylon-6 composite electrospun fiber webs increased from 0.5 to 1.5 S cm as the di sion time increased from 10 min to 4h because of the even distribution of PANI in the electrospun fiber webs. However, the surface conductivities of the PANI/nylon-6 composite electrospun fiber webs somewhat decreased from 0.22 to 0.14 S cm as the di sion time increased, probably because PANI was contaminated with aniline monomers, aniline oligomers, and some alkyl chains, which served as electrical resistants. 

Applications.—Nylon 6 properties have been reviewed > and design and moulding discussed with basic matmal handling precautions. The properties of nylon 6 modified with Izocyn T-IOO has been evaluated and thermal properties were found to deteriorate but improvements were observed in mechanical and electrical properties. Studies on nylon 6 as seals have been reported, as have polyamide resins for paint products. ... 

The dependence of the relaxation temperatures on the level of absorbed water in Nylon 6-6 is known from dynamic mechanical studies (Starkweather 1980,1973a Prevorsek et al. 1971) as well as dielectric studies (Starkweather and Barkley 1981). The temperature variations with sorbed moisture of the loss modulus peaks for the three relaxations are shown in Fig. 5.29 (Starkweather 1980). The test frequency for the three relaxations varies slightly but is around 1 Hz. The data indicate that the temperature of the a relaxation at a given frequency decreases by about 100 °C (to below ambient) between dryness and saturation. The P relaxation is also shifted to lower temperatures and higher frequencies by absorbed water, while the temperature of the y relaxation is only slightly affected, shifting to somewhat lower temperatures and higher frequencies. 

Another valued result in determining performance is obtained by studying impact behavior as a function of temperature. Materials that behave in a ductile fashion at room temperature become brittle at a low temperature. This transition in mechanical behavior is known as the Brittle to Ductile Temperature. Figure 5 gives an example of the temperature dependence of the toughness of nylon 6 modified with core/shell particles. 

This is a highly polar polymer and crystalline due to the presence of amide linkages. To achieve effective intercalation and exfoliation, the nanoclay has to be modified with some functional polar group. Most commonly, amino acid treatment is done for the nanoclays. Nanocomposites have been prepared using in situ polymerization [85] and melt-intercalation methods [113-117]. Crystallization behavior [118-122], mechanical [123,124], thermal, and barrier properties, and kinetic study [125,126] have been carried out. Nylon-based nanocomposites are now being produced commercially. 

PP is probably the most thoroughly investigated system in the nanocomposite field next to nylon [127-132]. In most of the cases isotactic/syndiotactic-PP-based nanocomposites have been prepared with various clays using maleic anhydride as the compatibilizer. Sometimes maleic anhydride-grafted PP has also been used [127]. Nanocomposites have shown dramatic improvement over the pristine polymer in mechanical, rheological, thermal, and barrier properties [132-138]. Crystallization [139,140], thermodynamic behavior, and kinetic study [141] have also been done. 

Because membrane filtration is the only currently acceptable method of sterilizing protein pharmaceuticals, the adsorption and inactivation of proteins on membranes is of particular concern during formulation development. Pitt [56] examined nonspecific protein binding of polymeric microporous membranes typically used in sterilization by membrane filtration. Nitrocellulose and nylon membranes had extremely high protein adsorption, followed by polysulfone, cellulose diacetate, and hydrophilic polyvinylidene fluoride membranes. In a subsequent study by Truskey et al. [46], protein conformational changes after filtration were observed by CD spectroscopy, particularly with nylon and polysulfone membrane filters. The conformational changes were related to the tendency of the membrane to adsorb the protein, although the precise mechanism was unclear. 

Researchers have examined the creep and creep recovery of textile fibers extensively (13-21). For example, Hunt and Darlington (16, 17) studied the effects of temperature, humidity, and previous thermal history on the creep properties of Nylon 6,6. They were able to explain the shift in creep curves with changes in temperature and humidity. Lead-erman (19) studied the time dependence of creep at different temperatures and humidities. Shifts in creep curves due to changes in temperature and humidity were explained with simple equations and convenient shift factors. Morton and Hearle (21) also examined the dependence of fiber creep on temperature and humidity. Meredith (20) studied many mechanical properties, including creep of several generic fiber types. Phenomenological theory of linear viscoelasticity of semicrystalline polymers has been tested with creep measurements performed on textile fibers (18). From these works one can readily appreciate that creep behavior is affected by many factors on both practical and theoretical levels. 

Wallace Carothers will be the subject of one of our Polymer Milestones when we discuss nylon in Chapter 3. Among his many accomplishments in the late 1920s and early 1930s, Carothers and his coworkers made a major contribution to the discovery and eventual production of the synthetic rubber, polychloroprene. It was synthesized from the diene monomer, chloroprene, CH2=CCI-CH=CHr Chloroprene, which is a very reactive monomer—it spontaneously polymerizes in the absence of inhibitors— was a product of some classic studies on acetylene chemistry performed by Carothers and coworkers at that time. In common with butadiene and iso-prene, in free radical polymerization chloroprene is incorporated into the growing chain as a number of different structural isomers. Elastomeric materials having very different physical and mechanical properties can be made by simply varying the polym-... 

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