Cellulosic material strength

It is probable that varying degrees of ordering of chains exist in a cellulosic material and that a sharp differentiation of crystalline and non-crystalline celluloses may not be feasible or even possible. Theoretically, the lateral surfaces of crystallites are amorphous but may have far less importance in determining such properties as strength, flexibility and extensibility than the non-crystalline cellulose which supplies continuity of structure in the direction of crystallite orientation. Yet properties like moisture absorption and swelling may be more dependent upon the amount of cellulose which exceeds a certain degree of disorder (permeability) than upon location. The definition of crystallinity may, therefore, be made ultimately in terms of practical objectives. 

Lynch, L. W. High-strength cellulosic materials through internal polymerization. Tappi 46, 480 (1963). 

New International Dictionary, Merriam Co, Springfield, Mass(1951), 73 Alperox C. Trade name for tech lauroyl peroxide manufd by the Lucidol Division of Wallace Tieman, Inc, Buffalo, NY Alpha-Cellulose is that portion of cellulosic material(pulp, paper, etc) which,after treatment with 17.5% NaOH(mercerized strength) at 20° and diln to 7.3% NaOH,can be separated by filtration. The residue of alpha-cellulose is a good index of the undegraded cellulose content of the material. The alkali treatment removes degraded(oxidized or hydrolyzed) cellulose and short chain material. Some pentosans and hexosans may... 

Lignocellulosic materials have a common basic structure, but vary greatly in chemical composition and physical structure.4 Typically, these materials contain 30 percent to 60 percent cellulose, 10 percent to 30 percent hemicellulose (polyoses), and 10 percent to 20 percent ligmn. Cellulose provides strength and flexibility, while lignin supports and protects the cellulose from biological and chemical attack. Hemicellulose bonds lignin to cellulose. 

Adhesives. Poly(vinyl alcohol) is used as a component in a wide variety of general-purpose adhesives to bond cellulosic materials, such as paper and paperboard, wood textiles, some metal foils, and porous ceramic surfaces, to each other. It is also an effective binder for pigments and other finely divided powders. Both fully and partially hydrolyzed grades are used. Sensitivity to water increases with decreasing degree of hydrolysis and the addition of plasticizer. Poly(vinyl alcohol) in many applications is employed as an additive to other polymer systems to improve the cohesive strength, film flexibility, moisture resistance, and other properties. It is incorporated into a wide variety of adhesives through its use as a protective colloid in emulsion p olymerization. 

Wood is an anisotropic material. That is, wood and other cellulosic materials have different properties when measured along different axes. Tensile and shear strengths of wood are greater along the longitudinal direction, parallel with the wood fibers. 

The paper and textile industries have been concerned about the aging, deterioration, and degradation of cellulosic materials at elevated temperatures for practical reasons, such as the performance of tire yarn and electrical insulation paper, and the problems involved in drying or processing the cellulosic materials in general. However, due to the practical nature of these problems, the reactions involved have often been measured in terms of loss of strength and other physical properties. 

The section on degradation of organics deals with paints, plastics, nylon, wood, and architectural organics. The effects of acid deposition on wood and other cellulosic materials are described. Strength losses in wood may be caused by hydrolytic degradation of the hemicelluloses and a sulfonation reaction of the lignin. Thus, the fibrils and matrix structure is affected. Cotton materials can be affected similarly, and soiling will result. The effect of acid deposition of nylon is indicative of a potentially shorter serviceable lifetime for outdoor fabrics. 

Blending of HDPE with rice hnlls certainly improves the material strength and stiffness, however, less compared with Biodac , blend of cellulose fiber with minerals (Tables 3.13 through 3.16). These tables show flexural properties of commercial... 

A simple, low-cost fibrous binder component that is available everywhere can be obtained by grinding waste paper. Fig. 8.25 is the flow diagram of a plant for the production of paper fluff from, for example, old newsprint as a binder for use in a roller press briquetting plant. This cellulosic material mixes quickly and uniformly with dry powders in any kind of blender. Even small percentages (2 %) result in a marked increase in (crushing) strength if compared with two other common binders (Fig. 8.26) [8.2.1]. 

The controlled heating of polyacrylonitrile fibers under tension also causes an elimination of nitrogenous products to leave a carbon fiber of high tensile strength that can be considered as the end product of the line of chemical elimination reactions. Carbon fibers from cellulosic materials, lignin, and various interpolymers and blends have been developed. The structures of these products consist largely of three-dimensional carbon networks, partially crystalline and partially graphitic or amorphous. 

Table 18.3 Tensile strength and modulus, unnotched Oiarpy impact strength, and heat distortion temperature (HDT-A) for PP-man-made cellulose fiber ctnnposites showing ways to increase HDT Material Strength [MPa] Modulus [GPa] Charpy [kJ/m ] HDT-A [°C]...

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