Cellulose films

Holmberg M ef al 1997 Surface force studies of Langmuir-Blodgett cellulose films J. Colloid Interface Sci. 186 369-81... 

This includes wire enamels on a base of polyvinyl formal, polyurethane or epoxy resins as well as moulding powder plastics on phenol-formaldehyde and similar binders, with cellulose fillers, laminated plastics on paper and cotton cloth base, triacetate cellulose films, films and fibres of polyethylene terephthalate. 

Whereas cellulose films are biodegradable, that is they are readily attacked by bacteria, films and packaging from synthetic polymers are normally attacked at a very low rate. This has led to methods of degrading polymers to a sufficiently low molecular mass (typically about 10000) which are then accessible to biodegradation. 

Carbon disulfide is made by reacting carbon from natural gas, and sulfur from hydrogen iiMidc, tir sulfur dioxide. Carbon disulfide is used to make rayon and regenerated cellulose film... 

The membrane is critically important in osomometry. Selection of a membrane involves reconciliation of high permeability toward the solvent with virtual impermeability to the smallest polymer molecules present in the sample. Membranes of cellulose are most widely used. Commercially Regenerated cellulose film is a common source. The undried gel cellophane film is often preferred, but the dry film may be swollen in water (or in aqueous solutions of caustic or zinc chloride ) to satisfactory porosity. Useful cellulose membranes may also be prepared by denitration of nitrocellulose films/ and special advantages have been claimed for bacterial cellulose films. The water in the swollen membrane in any case may be replaced by a succession of miscible organic solvents ending with the one in which osmotic measurements are to be made. Membranes of varying porosity may be... 

Concern over the migration of plasticisers from packaging materials has led to various studies, amongst which monitoring levels of various phthalates from coatings of regenerated cellulose film [433] and of acetyl-tributyl citrate (ATBC) from vinylidene chloride/vinyl... 

Regenerated cellulose film (RCF) is basically a form of cellulose. Wood chips are immersed in a caustic solution and, after a maturation period, dissolved in carbon disulfide. This solution is subsequently extruded through a die into an acid solution, where regeneration occurs. The resulting film is then washed and plasticized with various glycols and humectants. 

The original trade name Cellophane is frequently misused generically, as other brand names for regenerated cellulose film also exist (Rayophane, Dio-phane, etc.). 

The fluorescence of MBC in a solid matrix (ethyl-cellulose films) is an order of magnitude higher than in fluid solution (ethanol or tetrahydrofuran) (8 ). 

A new Ni(II) optical chemical sensor based on immobilizing of 2-amino-lcyclopentene-ldithiocarboxylic acid (ACDA) (Figure 21), to transparent acetyl cellulose films was developed52. 

Materials and articles intended to come into contact with foodstuff are generally regulated in the EU in the Framework Directive 89/109/EEC. Under this Directive Single Directives are released, such as for Plastic Material (90/128/EEC), Cellulose Films (83/229/EEC), Elastomers and Rubber (93/11/EEC) and others. 

Horns and hooves were the raw materials for the early polymer preparations. These materials were ground up and treated in various ways so that they could be fabricated into such items as combs to use for ladies hair, and other specialty things of that sort. The next development was the use of cellulose from cotton or from wood as the raw material which was studied for making films and fibers. Work on the cellulose structure had provided information that it was a hydroxylated product, and by converting the hydroxyls to esters, the natural cellulose could be turned into a soluble material, which was spun into fibers and cast into films to make the first cellulose rayon-type material and cellulose films. 

The objective of this work is to determine the surface concentration of the hydroxyl groups of cellulose and PVA films utilizing their chemical modification. We chose these polymers mainly because the hydroxyl group is their sole functional group. Recently we have reported that a cellulose film is more excellent in wettability towards water than PVA, though cellulose is insoluble in water, in contrast to PVA(4). Since only the chemical composition of the surface must be responsible for water... 

Figure 7. Surface concentration (Cs) of the hydroxyl groups phenylurethanated with and without tin octoate for cellulose films (O) Visking without catalyst (0) cellophane with tin octoate...

It should be also pointed out that both of the cellulose films have the same urethane surface concentration of 2.0 x 10 mol cm 2 at saturation, irrespective of the presence of catalyst, whereas the PVA film has half the surface concentration of cellulose. 

Plasticizers are used in the polymer industry to improve flexibility, workability, and general handling properties. Dibutyl sebacate and phthalates, such as dibutyl phthalate, diethyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate, and diphenyl-2-ethylhexyl phosphate, serve widely as plasticizers in vinylidene chloride copolymers, nitrocellulose-coated regenerated cellulose film, and cellulose acetate (Castle et ah, 1988a). In PVC, di(2-ethylhexyl)... 

For battery separators, regenerated cellulose is placed on the surface of nonwoven so that the nonwoven is available to promote the wicking of the electrolyte. The nonwovens should not allow the penetration of viscose into itself. Suitable nonwovens are made from polypropylene, poly(vinyl alcohol), and hardwood hemps. Regenerated cellulose films are commonly used in alkaline manganese cells, both primary and secondary, in NiCd industrial batteries, as well as in silver—zinc batteries. 

The most common material used is cellophane, which is a cellulose film, which acts as a membrane and is capable of resisting zinc penetration. The cycle life of cells utilizing this material is severely limited due to the hydrolysis of the cellophane in alkaline solution. Various methods have been tried to stabilize cellulose materials, such as chemical treatment and radiation grafting to other polymers, but none have, as of now proved economically feasible. The most successful zinc migration barrier material yet developed for the nickel—zinc battery is Celgard microporous polypropylene film. It is inherently hydrophobic so it is typically treated with a wetting agent for aqueous applications. 

Subramaniam, 1988]. Hydrochlorination, usually carried out at about 10°C, proceeds by electrophilic addition to give the Markownikoff product with chlorine on the tertiary carbon (Eq. 9-33) [Golub and Heller, 1964 Tran and Prud homme, 1977]. Some cyclization of the intermediate carbocation (XXVI) also takes place (Sec. 9-7). The product, referred to as rubber hydrochloride, has low permeability to water vapor and is resistant to many aqueous solutions (hut not bases or oxidizing acids). Applications include packaging film laminates with metal foils, paper, and cellulose films, although it has been largely replaced by cheaper packaging materials such as polyethylene. 

According to the 1981-83 National Occupational Exposure Survey, as many as 15 600 workers in the United States were potentially exposed to di(2-ethylhexyl) adipate (NOES, 1999). Occupational exposure may occur through inhalation, mainly as an aerosol, during its manufacture and its use, particularly as a plasticizer of PVC films and in other materials used in food packaging such as adhesives, cellophane and hydroxy ethyl cellulose films. Exposure may also occur during the manufacture of rubber products, nonferrous wire, cosmetics, lubricants and hydraulic fluids (Opresko, 1984). No measurements of di(2-ethylhexyl) adipate exposure in manufacturing and processing industries are available. 

Figure 2 compares ATR spectra of the irradiated and unirradiated sides of a cellulose triacetate film after 24-hour radiation at 253.7 min vacuum. The ATR spectrum of a control cellulose triacetate film, which is identical with that of the unirradiated side in Figure 2, is given in Figure 3. Figure 4 shows the change of infrared absorptions of a cellulose film cast on a NaCl plate upon irradiation at 253.7 min vaccum. The spectra were recorded at 90°C. An increase in OH (3 microns) and a decrease in carbonyl (5.7 microns) absorption were noted. 

Eclair. A French detonating cord ("cordeau detonant ), consisting of a 5mm diam core of PETN (9.9g per meter) and two white threads serving as pilots. The core is covered with a thin cellulosic film and fabric. Its external diam is 5.5mm and detonation rate 6355 to 6745m/sec. Earlier French cords are listed in Encycl, Vol 3, p C530-L Refs 1) A. LeRoux, MP 32, 203-04(1950)... 

A simple picture of the structure of skin is to consider it as an interwoven mass of protein polymer chains containing channels and voids filled with aqueous matter. These channels in skin dermis are about 10 A in diameter (20). Many substances have been used to simulate skin in drug penetration studies, but they all have the disadvantage that little is known about their inherent structures. General examples illustrative of this fault are the common use of agar gels and cellulose films. 

Finally, various attempts have been reported to interpret the kinetics of radiation grafting. The study by Mock, and Vanderkooi (123) concerned the mutual radiation grafting of styrene from the vapor phase to ethyl cellulose film at 50° C. The radical flux was determined separately using electron spin resonance. The kinetic scheme rigorously took account of the diffusion controlled nature of the reaction and the appropriate diffusion constants were separately determined (124). The value for the ratio of for the graft polymerization was determined as... 

Fig. 4. UV grafting of acrylonitrile to cellulose film in dimethyl formamide solution with 10% water and 0.01 M 2,7 anthraquinone sodium disulfonate (112). — in air, C —in vacuo...

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