Antimicrobial Ag/Na carboxymethyl cotton burn dressings are developed by partial cation exchange of sodium by silver from sodium carboxymethyl cotton gauze/nonwovens through treatment with silver nitrate in an 85/15 ethanol/water medium. The ethanol/water medium is necessary to preserve the fibrous form of carboxymethyl gauze/nonwovens with a degree of substitution of 0.3 to 0.4. From the behavior of antimicrobial release and the suppression of bacterial and fungal proliferation, it is apparent that the dressings containing the silver antimicrobial agent will protect wound surfaces from microbial invasion and effectively suppress bacterial proliferation. Antimicrobial evaluations of Ag/Na carboxymethyl cotton at North American Science Associates and the Southern Regional Research Center are positive. Additionally, the results show that an enhanced burn treatment is possible using a highly moisture retentive sodium carboxymethyl gauze instead of conventional gauze now used with silver nitrate. The carboxymethyl gauze’s capacity to hold a large amount of antimicrobial solution creates the possibility for better antimicrobial treatment. The retention of a greater amount of silver nitrate solution on the dressing will require less replenishment of solution on dressings on patients, which will reduce nursing time.

Two types of nonwoven composites, uniform and sandwich structures, are produced using bagasse, kenaf, ramie, and polypropylene (PP) fibers. The experimental uniform composites include kenaf/PP (70/30), bagasse/PP (50/50), and ramie/PP (70/30). The experimental sandwich composites include kenaf/bagasse/kenaf and ramie/kenaf/ramie. A comparative study of these experimental composites is conducted in terms of mechanical properties, thermal properties, and wet properties. Composite tensile and flexural properties are measured using a desktop tensile tester. Composite thermal properties are characterized using dynamic mechanical analysis (DMA). Water absorption and thickness swelling of the composites are evaluated in accordance with an ASTM method. Scanning electron microscopy is used to examine the composite bonding structures. Statistical method of ANOVA is used for the comparative analysis. The study finds that the uniform structures have higher tensile strength and modulus, as well as higher flexural yielding stress and modulus than the sandwich structures. In terms of the wet properties, the uniform composites have less water absorption but higher swelling rate than the sandwich composites. The DMA results show that the uniform composites feature a higher softening temperature (140 C) and melting temperature (160 C), in contrast to the sandwich composites with the softening point 120 C and melting point 140 C. Within the uniform structure group or sandwich structure group, the composite thermal mechanical properties did not differentiate very much among the different natural fibers, indicating that the composite thermal mechanical strength was largely dependent upon the thermal property of the polypropylene bonding fiber.

Cotton cellulose in fiber, yarn, or fabric form was converted from cellulose I to the cellulose III polymorph. Excellent conversion to III was obtained by immersing cotton (cellulose I) in liquid ammonia at room temperature, subjecting it to pressures from 689.5 to 11,721.5 kPa (100 to 1700 psi) while saturated with ammonia, and de-gassing the ammonia at either room temperature or elevated (about 140°C) temperatures. De-gassing at either temperature was equally effective. Complete conversion to III was obtained when cotton fibers from a never-dried cotton boll were dried with dimethoxypropane, treated with liquid ammonia at 140°C and at 11,721.5 kPa, and dried at or above the critical temperature (132.5°C). Crystalline cellulose III obtained under high pressures was stable to boiling water. After several hours in boiling water, there was only a slight indication of its conversion to IV. Complete conversion of III to IV was obtained by first subjecting III to anhydrous ethylenediamine and then to the aprotic polar solvent, dimethylformamide.Formation of complexes between liquid ammonia and cellulose was reported as early as 1936, as were .changes in the crystal structures of cellulose resulting from decomposition of these complexes [2]. Changes in interplanar distances caused by interaction of cellulose I with liquid ammonia at atmospheric pressure and by interactions of cellulose with primary amines, as determined by x-ray diffraction, were reported [4,6,8]. Davis et al. [6] also noted that the interplanar distance, djol, of the product formed when cellulose was treated with ammonia in sealed tubes at 10 atmospheres of pressure differed from that obtained at atmospheric pressure. These findings were of academic interest until the advent of two British patents [9, 17] that described the use of liquid ammonia instead of aqueous NaOH to improve the smoothness of oellulosic fabrics and the strength and luster of cotton sewing threads. The report by Gogek [7] that pretreatment of cotton twill with liquid ammonia improved the washwear ratings and abrasion resistance of subsequently crosslinked fabric aroused the interest of the textile in-' dustry. Immediately, there was increased interest in the treatment of textiles with liquid ammonia [3,5].The degree of conversion of the crystalline lattice of native cotton (I) to cellulose III depends on the manner in which the liquid ammonia is removed [3,9, 17].Partial conversion to III occurs when ammonia is removed by evaporation or by extraction with solvents such as anhydrous acetone or tetrahydrofuran. Quenching of the ammonia-cellulose complex with either water or alcohols causes reversion to I. The literature reports that, at best, liquid ammonia pretreatments result in mixed I and III lattices, while conventional meroerizations result in mixed 1 and II lattices. Lewin and Roldan gave evidence that III is obtained by drying the cellulose-ammonia complex in the absence of water [ 12], but these investigators obtained decrystallization and poor conversion of ...

In addition to its usual native crystalline form (cellulose I), cellulose can exist in a variety of alternative crystalline forms (allomorphs) which differ in their unit cell dimensions, chain packing schemes, and hydrogen bonding relationships. We prepared, by various chemical treatments, four different alternative allomorphs, along with an amorphous (noncrystalline) cellulose which retained its original molecular weight. We then examined the kinetics of degradation of these materials by two species of ruminal bacteria and by inocula from two bovine rumens. Ruminococcus flavefaciens FD-1 and Fibrobacter succinogenes S85 were similar to one another in their relative rates of digestion of the different celluloses, which proceeded in the following order: amorphous > 1111 > IV, > 11111 > I> II. Unlike F. succinogenes, R. flavefaciens did not degrade cellulose II,