D. V. Parikh

Natural fibers for automotive nonwoven composites

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.

Processing and Characterization of Flame Retardant Cotton Blend Nonwovens for Soft Furnishings to Meet Federal Flammability Standards

Effective from July 1, 2007 it is mandatory that all mattress sets meet the federal flammability standard CFR 1633. It is necessary to impart flame resistance that would provide at least 30 min for occupants to escape fire. Changes in the flammability laws are expected on other soft furnishings of sleep products like comforters and pillows. Generally these products are often the first to be engulfed by the fire. Currently many inherently flame retardant (FR) fibers and chemicals are available in the market. We have developed barrier fabrics with FR properties by incorporating these fibers in blends with cotton that either meet or exceed the standard. Results from this ongoing research are discussed in this article.

Characterization of tri-o-methylcellulose by one- and two-dimensional NMR methods†

Tri-O-methylcellulose was prepared from partially O-methylated cellulose and its chemical shifts ( 1 H and 13 C), and proton coupling constants were assigned using the following NMR methods: (1) One-dimensional 1 H and 13 C spectra of the title compound were used to assign functional groups and to compare with literature data; (2) double quantum filtered proton-proton correlation spectroscopy ( 1 H, 1 H DQF-COSY) was used to assign the chemical shifts of the network of 7 protons in the anhydroglucose portion of the repeat unit; (3) the heteronuclear single-quantum coherence (HSQC) spectrum was used to establish connectivities between the bonded protons and carbons; (4) the heteronuclear multiple-bond correlation (HMBC) spectrum was used to connect the hydrogens of the methyl ethers to their respective sugar carbons; (5) the combination of HSQC and HMBC spectra was used to assign the 13 C shifts of the methyl ethers; (6) all spectra were used in combination to verify the assigned chemical shifts; (7) first-order proton coupling constants data (J H,H in Hz) were obtained from the resolution-enhanced proton spectra. The NMR spectra of tri-O-methylcellulose and other cellulose ethers do not resemble the spectra of similarly substituted cellobioses. Although the 1 H and 13 C shifts and coupling constants of 2,3,6-tri-O-methylcellulose closely resemble those of methyl tetra-O-methyl-β-D-glucoside, there are differences with regard to the chemical shifts and the order of appearances of the resonating nuclei of the methyl ether appendages and the proton at position 4 in the pyranose ring. H4 in tri-O-methylcellulose is deshielded by the acetal system comprising the β-1→4 linkage, and it resonates downfield. H4 in the permethylated glucoside is not as deshielded by the equitorial O-methyl group at C4, and it resonates upfield. The order of appearance of the 1 H and 13 C resonances in the spectra of the tri-O-methylcellulose repeat unit (from upfield to downfield) are H2 < H3 < H5 < H6a < H3a < H2a < pro R H6B < H4 < pro S H6A « H1 and C6a < C3a < C2a < C6 < C5 < C4 < C2 < C3 « C1, respectively. Close examination of the pyranose ring coupling constants of the repeat unit in tri-O-methylcellulose supports the 4 C 1 arrangement of the glucopyranose ring. Examination of the proton coupling constants about the C5-C6 bond (J 5,6A and J 5,6B ) in the nuclear Overhauser effect difference spectra revealed that the C6 O-methyl group is predominantly in the gauche gauche conformation about the C5-C6 bond for the polymer in solution.

Evaluation of three flame retardant (FR) grey cotton blend nonwoven fabrics using micro-scale combustion calorimeter

Unbleached (grey or greige) cotton nonwoven fabrics (with 12.5% polypropylene scrim) were treated with three phosphate–nitrogen–based flame retardant formulations and evaluated with micro-scale combustion calorimeter. Heat release rate, peak heat release rate, temperature at peak heat release rate, heat release capacity, total heat release and char yield were determined. The peak heat release rate and total heat release results demonstrated that nonwoven fabrics treated with a formulation having higher diammonium phosphate and no dimethylol dihydroxyethyleneurea were superior to those treated with a formulation containing dimethylol dihydroxyethyleneurea. Nonwoven fabrics treated with these formulations were both superior to the nonwoven fabrics treated with a commercially available flame retardant formulation. These results were supported by the percentages of phosphorus and nitrogen on these fabrics, confirming that P–N synergism imparts high flame retardancy to the nonwoven fabrics. Grey cotton (untreated) consistently showed better flame resistance than (untreated) bleached cotton. As a result, its flame retardant products had lower heat release rate/peak heat release rate and other flammability characteristics than those of the bleached cotton. Additionally, grey cotton is softer than bleached cotton and saves the cost of bleaching and waste disposal. These three flame retardant formulations were used primarily to treat the cotton component of the nonwoven blend to make it flame retardant without flame retardant improvement for the polymer component.

Biodegradable materials for nonwovens

Abstract: Demand for nonwovens is increasing globally, particularly in the disposable products area. As the consumption of nonwoven products with short life increases, the burden on waste disposal also rises. In this context, biodegradable nonwovens become more important today and for the future. As a result, there is increasing effort to design and develop biodegradable nonwovens, with research and development efforts from both academia and industry. Several new biodegradable polymers such as polylactic acid (PLA) and Biomax have helped the industry to produce larger amounts of biodegradable nonwovens. In addition, the use of natural fibres in nonwoven products is also increasing. There is continuing effort to develop new ways to produce biodegradable nonwoven materials by combination of natural fibres and other biodegradable resins or fibres; these research and development activities are helping these environmentally friendly fabrics to become affordable materials for many consumer products.

Flame-retardant cotton barrier nonwovens for mattresses

According to regulation CPSC 16 CFR 1633, every new residential mattress sold in the United States since July 2007 must resist ignition by open flame. An environmentally benign “green,” inexpensive way to meet this regulation is to use a low-cost flame-retardant barrier fabric. In this study, a nonwoven fabric of grey unbleached cotton was treated with a low-cost phosphate-based formulation. The energy-dispersive X-ray microanalysis showed uniform nitrogen and phosphorus distribution. With 17% add-on, the flame-retardant unbleached cotton barrier showed a limiting oxygen index of 33% oxygen and 83 mm of char length with no after-flame and no afterglow in the vertical flame test. Under air and nitrogen at 500°C, 24% and 35% char remained after thermogravimetric analyses, respectively. This flame resistance is comparable to that of current commercial barrier fabrics made from bleached cotton and Flovan cyanoguanidine or from T-bond grey cotton fiber highlofts (Jones Fiber). Mattresses constructed with a flame-retardant cotton nonwoven barrier fabric are predicted to meet the requirements of 16CFR1633. As a follow-up to this study, a full-scale mattress burn test is recommended.