Polyamides characteristic ratio

Both poly(l,4-benzamide) and poly(l,4-phenylene terephthalamide) are macromolecules that are characterized by a remarkable rigidity, unlike the flexible nature of the more common polymers, such as the polyamides nylon 6, 6.6, etc. The characteristic ratio, C , (6) of these aramids was estimated to be as high as 124 (7). This quantity is defined as... 

The characteristic ratio of PE at room temperature is - according to Abe et al. [4] — 8.0 as compared to a value of 2 calculated under neglect of hindrances to bond rotation. The force between PE chain ends, therefore, is by a factor of 2 smaller if the effect of the potential energy on chain conformation is taken into consideration. For polyamide chains the detailed calculations of Flory and Williams [5] led to characteristic ratios of 6.08 (PA 6) and 6.10 (PA 66) in excellent agreement with the experimental value of 5.95 for PA 66 found by Saunders [6]. The calculated force between PA chain ends, then, will be smaller by a factor of about 1.7. 

Figure 6.8 plots the reinforcement ratios for short glass fibre reinforced polyamide (PA-GF) versus neat polyamide for six important characteristics calculated versus density and material cost. These characteristics are tensile strength, tensile and flexural modulus, impact strength, HDT A and B. 

The main uses for both nylon 6,6 and nylon-6 are in apparel, carpets, and industrial applications. In the area of general apparel, polyester has gained considerably in significant market segments at the expense of polyamides because of its easy-care characteristics. Polyamide textile fibers, however, will expectedly continue to be the principal materials for women s hosiery, intimate apparel, and certain stretch fabrics. It seems safe to conclude that the price to performance ratio will continue to secure a firm market position for polyamide fibers, even at increased feedstock prices. Primarily tire yarns in the developing countries will drive polyamide industrial fibers. 

Table 6 lists the AC percentage for both polyamide/polysulfone membranes the N/0 ratio indicates an excess of oxygen atoms for the commercial membrane and a defeet of oxygen for the experimental one with respect to theoretical polyamide value ((N/0) = 1). Sinee the presence of polyamide non-characteristic elements was very low, impurities or rare chemicals must contain the same type of atoms than polyamide, which can be estimated by curve fitting of the core-level speetra. 

Table 6. Relative atomic concentrations (%) on the surface of polyamide membranes and characteristic atomic ratios...

A majority of polyamides go into manufacture of textile fibers. Ghosh and Rodgers used a filter analyzer to determine heat set temperature of nylon yarn [23]. Their work was based on the ratio of crystalline to amorphous nylon. Combination bands were vital in resolving the spectral characteristics of crystalline to amorphous nylon ratios. Percent moisture in caprolactam was studied for eventual placement online. The laboratory study measured moisture in the range of 0.05 to 9% with a standard error of prediction (SEP) of 0.4 and an r of 0.995. Samples were scanned from 800 to 2500 nm at room temperature with satisfactory results. Improved accuracy and precision are attainable by use of a temperature correction algorithm. 

ILs have been recently evaluated as non-volatile plasticizers and as external or internal lubricants in several polymers including PVC [3], PMMA [4] and polyamides [5]. In this article, an amorphous PL A (polylactide) polymer is blended with two phosphonium-based ILs at various ratios by melt-blending, solution casting and a microencapsulation technique in order to investigate polymer/IL miscibility and its role in the development of a modified polymer with novel rheological, mechanical and thermal characteristics. Results of thermogravimetric analysis, differential scanning calorimetry, capillary rheometry, batch mixer torque measurements and optical microscopy are discussed. 

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