Strength cotton fabric

Wood flour, a fine sawdust preferably from soft woods, is the most commonly used filler. Good adhesion occurs between the resin and the wood flour, and some chemical bonding may also occur. Wood flour reduces exotherm and shrinkage, improves the impact strength of the moldings, and is cheap. For better impact strength cotton fabric or chopped fabric may be incorporated. Asbestos may be used for improved heat and chemical resistance, and iron-free mica powder maybe used for superior electrical insulation resistance characteristics. 

Fabric-Based Grades. Grade C is made from cotton fabric weighing over 140 g/m (4 oz/yd ). The maximum thread count in any ply is 28/cm (72/in.) in the fiU direction, and the maximum total thread count in the warp and fiU directions is 56/cm (140/in.). Heavier fabrics provide higher impact strength but rougher machined edges. Its use for electrical apphcations is not recommended. 

An important chemical finishing process for cotton fabrics is that of mercerization, which improves strength, luster, and dye receptivity. Mercerization iavolves brief exposure of the fabric under tension to concentrated (20—25 wt %) NaOH solution (14). In this treatment, the cotton fibers become more circular ia cross-section and smoother ia surface appearance, which iacreases their luster. At the molecular level, mercerization causes a decrease ia the degree of crystallinity and a transformation of the cellulose crystal form. These fine stmctural changes iacrease the moisture and dye absorption properties of the fiber. Biopolishing is a relatively new treatment of cotton fabrics, involving ceUulase enzymes, to produce special surface effects (15). 

Empirical attempts have been made to relate strip and grab test results, particularly for cotton fabrics, so that if one strength is known, the other can be calculated. The relationship is complex, depending on fiber strength and modulus, yam size and crimp, yam-to-yam friction, fabric cover factor, weave, weight, and other factors (19). 

The introduction of rayon, nylon and other manmade fibers with their greater strengths per unit cross sectional area compared with cotton fabric has led to the use of rubber coated fabrics in the manufacture of various engineering products such as tyres, beltings and hoses and also several specialty products for the chemical process industries. The arduous service conditions prevailing... 

Emulsifiable concentrate formulation of diazinon, diluted to field strength (0.5% a.i.) was used to contaminate 100% cotton fabric.7 A single hot-water wash (60°C) results in 1% diazinon remaining on the cotton fabric. When cotton is contaminated with the concentrated (full-strength) diazinon (47.5%), and washed in hot water, 4% pesticide residue remains. 

When wettable powder formulation of iprodione was diluted to field strength (0.05% a.i.) and used to contaminate 100% cotton and 65/35 polyester/cotton fabric, it was found that a single warm water wash (50°C) left approximately 1% iprodione residues on the fabric.5... 

Figure 4. Strength of cotton print clothes thermally degraded by heating at 168°C for various times. The strength of fabrics degraded by hydrolyzing 16 hr in 40% sulfuric acid at room temperature and by high-voltage electron irradiation at doses of 50 and 100 Mrad are also indicated.

Dimethyldichlorosilane. Because dimethyldichlorosilane has been polymerized to a silicone polymer on cotton fabrics to impart stain and water resistance and can be applied as a vapor, this agent was examined as a possible consolidant. This treatment also improves fabric hand, resistance to chemicals and weathering, resistance to abrasion (by reducing friction), and reduces the tensile strength loss when resin finishes are applied all factors that should make the material a desirable and effective consolidant. The reactions involved are as follows ... 

The swelling of cotton with an aqueous solution of sodium hydroxide is an important com mercial treatment. It is called mercerization after its discoverer, John Mercer, who took a patent on the process in 1850 [308]. Other alkali metal hydroxides, notably lithium hydroxide and potassium hydroxide, will also mercerize cotton, but normally sodium hydroxide is used. Mercerization is utilized to improve such properties as dye affinity, chemical reactivity, dimensional stability, tensile strength, luster, and smoothness of the cotton fabrics [309]. The treatment is normally applied either to yarn or to the fabric itself either in the slack state to obtain, for example, stretch products, or under tension to improve such properties as strength and luster. The interaction of alkali metal hydroxides and cellulose has been extensively reviewed. Earlier reviews can be traced from relatively recent ones [99,310,311]. 

The effects of cellulase enzymes on cotton substrates that were dyed with various classes of dyes have been reported. It was found that vat dyes do not inhibit cellulase activity on cotton, and hydrolysis of the substrate with subsequent color removal transpires. In contrast, cellulase activity on cotton was inhibited by the presence of some direct and reactive dyes. There is the probability that a dye-enzyme complex is formed with less activity than that of the free enzyme. The increased weight loss from enzymatic treatment on untreated cellulose is associated with a slight reduction in dye sorption, and this may be because of a reduction of amorphous regions in cellulose where dye molecules are usually sorbed. Cellulase activity is more prominent on mercerized cotton than on unmercerized cotton. This is because mercerization is associated with a decrease in the crystallinity of the cellulosic structure [540]. One major negative aspect of cellulase treatment of cotton fabric is the strength loss associated with the approximately 3-5% weight reduction under normal treating conditions. Of course, this is to be expected after cellulose is hydrolyzed. Future research efforts may lead to processes in which enzymes... 

In this chapter, we report the results of a study on the use of tetra-hydridoborate reduction in improving both the color and strength retention of cotton fabric artificially aged at temperatures ranging from 100 to 150 °C. 

---