Films cellulose-based

Asahi Chemical Industry carried out an exploratory investigation to determine the requirements for cellulose based separators for lithium-ion batteries. In an attempt to obtain an acceptable balance of lithium-ion conductivity, mechanical strength, and resistance to pinhole formation, they fabricated a composite separator (39—85 /cellulosic fibers (diameter 0.5—5.0 /pore diameter 10—200 nm) film. The fibers can reduce the possibility of separator meltdown under exposure to heat generated by overcharging or internal short-circuiting. The resistance of these films was equal to or lower than the conventional polyolefin-based microporous separators. The long-term cycling performance was also very comparable. 

The membranes produced from polyelectrolyte complexes on the basis of weak polyelectrolytes, e.g. poly(carboxylic adds) (PAA and PMAA) and polyamines [poly(2-N,N-dimethylaminoethyl methacrylate), polyethylenepiperidine, polyethyl-enepyperasine, polyethylenimine] have been prepared140,141 and used in dialysis and ultrafiltration. Permeability coeffirients of membranes made from poly electrolyte complexes are much higher (4 and 20 times, resp.) in comparison with the cellulose-based membranes (Cuprophane, Film 1(M)). 

Ozturk AG, Ozturk SS, Palsson BO, et al. Mechanism of release from pellets coated with an ethyl cellulose-based film. J Control Release 1990 14(3) 203-213. 

This class of cellulose derivatives includes hydroxypropylmethylcellulose or HPMC, hydroxyethylcellulose (58), methylcellulose, HPC, and ethylcellulose. As mentioned earlier, most cellulose-based polymers except for PVP, have lower surface tension values in the range of 40-50 mN/m, thus similar adhesive and film-forming qualities will be seen. 

Films are continuous, thin, clear, coloured or opaque materials derived from organic polymers. Most polymers are synthesised whereas the cellulose -based films mentioned previously are mainly of natural origin. 

USE To impart pearly surface to cellulose-base, polystyrene, and phenol-formaldehyde resins, Deutsch er of.. U.S. pat. 2,816,044 (1957 to Brit. Resin Prods.). In heat -sensitive coating for copying paper, Van Dam, (J.S. pat. 2,897,090 (1959 to Anken Chem. Film). To stabilize tolylenedi-amme mixtures against deterioration and discoloration. Powers, US. pat. 3,138,641 (1964 to Mobay). 

Melt-sprayed coatings have ethyl cellulose, acetyl cellulose or cellulose ace-tobut3Tate as a film-forming base. Mineral oil, which dissolves a number of Cl of ferrous and nonferrous metals and is perfectly compatible with the majority of cellulose plasticizers, is often introduced into the molten composition to lower adhesion of the coating to the goods being protected. 

Lacquers are clear, synthetic coatings, most often cellulose-based (such as nitrocellulose often modified with a resin, cellulose acetate, methyl cellulose, ethyl cellulose, and benzyl cellulose) that dry through evaporation of a solvent. Lacquers can be made from a liquid lacquer base, a starting point for speciality lacquers (e.g., automotive) which most often contain the film-forming material in concentrated solution with or without other components. The base may be up to 25% nitrocellulose. 

Cellulose-based plastics, particularly cellulose nitrate and acetates, were the most commercially important semi-synthetics up to the 1940s and were used as the base for photographic film, textile fibres, moulded goods and in lacquers. Naturally occurring polymer cellulose in the form of cotton linters or wood pulp is chemically treated to increase its solubility. Cellulose has a high molecular weight of between 100000 and 500000 and an empirical formula C0H1OO5. Casein-formaldehyde is the only protein-based moulded plastic that achieved commercial success. It is based on cow s milk and is still produced in very small quantities for specialist items such as hand-coloured buttons. 

Gindl and keckes [124] prepared cellulose based nanocomposite films with different ratio of cellulose I and II, The process consist of a partial dissolution of microcrystalline cellulose powder in lithium chloride/N,N-dimethylacetamide and subsequent film casting. The results showed that, by varying the cellulose I and II... 

Cranston, E.D., Gray, D.G. Formation of cellulose-based electrostatic layer-by-layer films in a magnetic field. Sci. Technol. Adv. Mater. 7, 319-321 (2006)... 

Chem. Descrip. Triphenyl phosphate CAS 115-86-6 EINECS/ELINCS 204-112-2 Uses Rame retardant platinizing agent, plastidzer tor collodion cotton plastidzer w/o gelatinizing properties for acetyl cellulose reduces tiamm. ot NC and acetyl cellulose-based plastic compds. and lacquer films flame retardant plasticizer tor photographic film materials, surf, coatings, phenolic laminates, cellulose acetate film/compds., rubber articles made from acrylonitrile-butadiene, polychloroprene rubber Features Not compat. with PVC... 

With support from the OSW, Reid at the University of Florida pursued an alternative design in the mid 1950 s based on filtration equipment available at the time. His design used pressurized air to drive water across polymeric films. Of the commercially available films, cellulose acetate was the most attractive due to its high salt rejections. Unfortunately, product water permeation rates were low. Since permeation rate was inversely proportional to film thickness, solution casting techniques were developed to form films as thin as possible [10]. Around the time of Hassler s and Reid s work, the term reverse osmosis was adopted to describe membrane desalination [8]. 

Table 3.4 Typical tensile properties of cellulose-based films in machine (MD) and transverse (TD) directions.

The all-cellulosic based composites were prepared in the form of dense films (thickness 20-60 pm). Clear composite films were obtained either from isotropic or liquid crystalline solutions of HPC (chiral nematic) by a casting method. 

In the cross-linked films, the difference between the roughness parameters of the two surfaces is smaller than that observed in the case of the uncross-linked ones, as shown also in Fig. 15.5. This means that the effect of fiber settling at the bottom surfaces is less pronounced for the cross-linked films, suggesting a better distribution of the fibers over the cross section. This influences the mechanical properties of isotropic all-cellulosic based composites, as discussed later. Also, the asymmetry between top and bottom surfaces will have an impact in gas barrier properties of these composites. 

Table 15.4 clearly shows that anisotropic composite films present better mechanical properties. It is worth noting that anisotropic composites also have higher Young s modulus, yield stress and ultimate tensile strength than cross-linked isotropic homo-logues [13]. This, along with results presented in Table 15.4, seems to indicate that the mechanical properties of these all-cellulosic based composites depend on matrix anisotropy and fiber orientation rather than on cross-linking. 

Table 15.3 Mechanical properties of anisotropic all-cellulosic based composite films, measured in the shear direction (0°) and perpendicular to it (90°)...

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