SynopsisThe effect of fiber structure and morphology on the resultant mechanical and low load deformation properties of thermally bonded nonwoven polypropylene fabrics has been studied. Commercially available staple polypropylene fibers varying in linear density and draw ratio (Herculon and Marvess staple fibers) were used in this study. The orientation of these fibers was characterized by birefrigence measurements. Differential scanning calorimetry measurements were made to determine the heat of fusion and melting point of fibers. Experiments confirm that tensile strength and stiffness of the fabrics correlate with this fiber structure. Under the same bonding conditions fabrics made from fibers with low draw ratios show higher tensile strength and stiffness than do fibers with high draw ratios. The mechanical properties of fabrics were found to be greatly affected by the thermal bonding temperature. The tenacity and flexural rigidity of fabrics made from poorly oriented fibers show higher values than those made from highly oriented fibers. The shrinkage of the fabrics was observed to increase with increasing bonding temperature in both machine and cross machine directions. The changes in fabric thickness due to the thermal bonding are considerably lower for poorly oriented fibers.

Treatment of polyester, nylon 66, cotton, and wool fabrics with aqueous solutions of polyethylene glycol phase change materials and of plastic crystal compounds by a conventional pad-dry procedure produced modified fabrics with thermal storage and release properties 2-2.5 times greater than those of untreated fabrics at the same temperature intervals. These modified or temperature-adaptable fabrics are chemically impregnated with phase change or plastic crystal substances that impart balanced thermal storage and release properties at various temperature ranges. Application of another plastic crystal compound in aqueous solution to the fabrics under these conditions was not suitable, since it sublimed during the fabric drying process. Fiber type and heating rate appeared to have little effect on the overall heat content or thermal performance of the treated fabrics. As in earlier studies, thermal storage and release properties of the modified fabrics were reproducible after 5 cycles and remained essentially constant for at least 50 heating and cooling cycles. An extensive survey of latent heat materials for heat

Developments and research in the present decade on the antibacterial finishing and disinfection of textiles are reviewed. Definitions and concepts of terms such as antimicrobial agent, antibacterial agent, disinfectant, and sanitizers are discussed from both a regulatory and scientific perspective. Quantitative tests for determining antibacterial activity of textiles usually involve sterilization of fabric, inoculation with a microorganism, and determination of bacteria remaining by wash-recovery or colony-count under a low-power microscope. Most qualitative tests for antibacterial activity are based on the ability of the agent to diffuse off the fiber into an agar medium. Most antifungal tests consist of inoculation of fabric, then inspection for visual growth of fungi after varying periods of time. Microbial ecology of the skin-clothing interface differs in everyday environments and situations from environments conducive to growth of microorganisms and cross- infection ; predominant bacteria and fungi and microbial population on different parts of the body are discussed in this context. Microorganism persistence on textiles is influenced to some extent by fiber type. Recent studies show that synthetics retain more odor-causing bacteria, and that dermatophytic fungi are more persistent on synthetics than on natural fibers; persistence time of pathogenic bacteria,on natural and synthetic fibers is dependent on relative humidity and method of fabric contami nation. Newer and commercialized processes for producing antibacterial fabrics durable to laundering are evaluated, and frequently-used disinfectants and sanitizers for textiles are stressed. Various techniques for affixing such agents to fibers are listed, and requirements for producing effective antibacterial and antifungal fibers for particular end-uses are enumerated. Some novel and recent uses for antibacterial fibers, such as water disinfection and air purification, are also mentioned.

Hollow rayon and polypropylene fibers have been modified to change their heat capacity dramatically in an ambient temperature range (270-310 K) by filling them with aqueous solutions of calcium chloride hexahydrate/strontium chloride hexahydrate capable of producing latent heat gains and losses in the modified fibers during repeated heating and cooling. Both fibers produced large endotherms in the heating cycle (303 K) that were dependent on the relative humidity at which the fibers were previously conditioned; however, only the modified rayon fibers exhibited a significant exotherm in the cooling cycle (282 K). Endotherms and exotherms for modified rayon fibers (previously conditioned at 45% RH) persisted even after 10 heating and cooling cycles. Apparently, hydrophilic differences in the two fiber types require different amounts of water in the salt system of the dried and conditioned fiber to produce reversible latent heat gains and losses caused by heats of fusion and crystallization of the salt system. Neither the unmodified fibers nor another aqueous salt system incorporated into the fibers (sodium sulfate/borax) exhibited any significant endothermic or exothermic changes on heating or cooling..

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