Cellulose deterioration

Feller RL, Lee SB, Bogaard J (1986) The kinetics of cellulose deterioration. In Needles HL, Zeronian SH (eds) Historic Textile and Paper Materials Conservation and Characterization. Advances in Chemistry Series 212. ACS, Washington DC, p 329... 

Weathering. This generally occurs as a result of the combined effect of water absorption and exposure to ultra-violet radiation (u-v). Absorption of water can have a plasticizing action on plastics which increases flexibility but ultimately (on elimination of the water) results in embrittlement, while u-v causes breakdown of the bonds in the polymer chain. The result is general deterioration of physical properties. A loss of colour or clarity (or both) may also occur. Absorption of water reduces dimensional stability of moulded articles. Most thermoplastics, in particular cellulose derivatives, are affected, and also polyethylene, PVC, and nylons. 

Oridation. This is caused by contact with oxidising acids, exposure to u-v, prolonged application of excessive heat, or exposure to weathering. It results in a deterioration of mechanical properties (embrittlement and possibly stress cracking), increase in power factor, and loss of clarity. It affects most thermoplastics to varying degrees, in particular polyolefins, PVC, nylons, and cellulose derivatives. 

Oil-base (including oil-modified alkyd resin) paint films should not be used in alkaline environments as the paint will deteriorate owing to saponification alkali-resistant coatings are provided by some cellulose ethers, e.g. ethyl cellulose, certain polyurethane, chlorinated rubber, epoxy, p.v.c./ p.v.a. copolymer, or acrylic-resin-based paints. In particular, aluminium and its alloys should be protected by alkali-resistant coatings owing to the detrimental effects of alkali on these metals. 

The results of mechanical properties (presented later in this section) showed that up to 20 phr, the biofillers showed superior strength and elongation behavior than CB, cellulose being the best. After 30 phr the mechanical properties of biocomposites deteriorated because of the poor compatibility of hydrophilic biopolymers with hydrophobic natural rubber(results not shown). While increasing quantity of CB in composites leads to constant increase in the mechanical properties. Scanning electron micrographs revealed presence of polymer-filler adhesion in case of biocomposites at 20 phr. 

Fluorination improved the complement activation and reduced the loss of platelets (see Figures 17.10 and 17.12), but there was a deterioration in the coagulation properties (Figure 17.11). It is interesting to note that these trends were independent of the fiber raw material (cellulosic or synthetic) used to make the membrane. 

Cellulose nitrate is very easily ignited and bums very rapidly or explosively, depending on the degree of confinement, degree of nitration and state of subdivision. Unless very pure and stabilised, it deteriorates in storage and may ignite... 

This presentation will discuss the membrane performance and its physical and chemical changes under unfavourable conditions. This kind of studies will give us information on trouble-shooting counter-measures for unexpected membrane deteriorations, and on the durability of a cellulose acetate membrane under adverse conditions. 

The major chemical processes of membrane deteriorations are hydrolysis and oxidation. Cellulose acetate is most stable at the level of around pH 4.7, and at the pHs lower or higher than that value, membrane hydrolysis is accelerated. In practical applications of cellulose acetate membranes, feed water pH is usually controlled between 5 to 6. But it is Impossible to control the pH of demineralized pure water for electronic and pharmaceutical uses, i.e. for ultrapure water polishing. In such cases feed water pH 7 should be supplied to cellulose acetate material. Studies of membrane behaviour under such conditions will give good information for estimating the membrane life. 

Any biological deterioration of cellulose acetate membranes is always by "accidental". To prevent this kind of deteriorations, chlorine injection to feed water is common practice. Inadequate control of chlorine injection may result in the enzymic deterioration of cellulose acetate membrane. 

Figure 2. Rejection—flux pattern of deteriorated cellulose acetate membrane f p, permeate flux of new membrane Fp, permeate flux of deteriorated membrane.

Deterioration of Asymmetric Cellulose Acetate Membranes with NaOCl -------Structural and Chemical Change... 

Model of Deterioration Mechanisum, As acetyl content decreases due to hydrolysis or oxidation of ester bonding, solute permeability increases. Then concentration of solute( in this case sodium hypochlorite) in the membrane increases and the hydrolysis or oxidation rate increases and so on. It will be more reasonable to assume that hydrolysis or oxidation rate of cellulose acetate in the active surface layer may be accelerated by the action of the nascent oxygen generated from sodium hypochlorite. 

Prop Meet), but this method proved to be not very satisfactory on account of the appreciable migration of NG into the inhibitor, which resulted in its deterioration at elevated temp. Migration occurs also when using cellulose acetate inhibitors... 

Measurement of pH is a potentiometric technique frequently used for measuring the degree of the deterioration of materials that are subjected to natural aging. The determination of pH levels is commonly carried out on ethnographic objects manufactured with parchment or leather, and it is especially relevant in altered paper due to the formation of acidic compounds from the decomposition of the woodpulps and other raw materials, which can induce the hydrolysis of the cellulose and then decrease the resistance and mechanical properties of the document [29]. 

The chemical sensitivity or life expectancy of reverse osmosis membranes is very important for manufacturing application. Thus chlorine is the most well known reagent for water disinfection. Glaster et al. 61 inspected the influence of halogens on the performance and durability of reverse osmosis membranes. Cellulose acetate was unresponsive to halogen agents but polyamide-type membranes deteriorated rapidly when exposed to halogens. 

Military Grades of NC The product produced by the above nitration purification process is of max stability. It is generally v si alk and contains less than 0.01% cellulose sulfate, which is unstable to heat moisture. The great care taken in the purification of NC is necessary since propellants made from NC contg even small amts of unstable impurities deteriorate rapidly. The US military grades of NC ate as... 

A few animals (especially ruminants and termites) are able to metabolize cellulose, but even these animals depend on appropriate microorganisms in their intestinal tracts to hydrolyze the -1,4 links other animals, including man, cannot utilize cellulose as food because they lack the necessary hydrolytic enzymes. However, such enzymes are distributed widely in nature. In fact, deterioration of cellulose materials —textiles, paper, and wood —by enzymatic degradation (such as by dry rot) is an economic problem that is not yet adequately solved. Efforts to turn this to advantage through enzymatic hydrolysis of cellulose to glucose for practical food production have not been very successful (see Section 25-12). 

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