Natural plastic cellulose based

The photooxidation of polymers on the other hand continues to decline in attention although there is special interest in natural cellulosic-based materials. Bio- and photodegradable plastics are important for agricultural usage although interest here is again in decline. The same applies to polymer stabilisation where commercial applications dominate very much with much emphasis on the practical use of stabilisers. For dyes and pigments stability continues to be a major issue. 

The first plastics were actually developed during the last half of the 19th century. Paper is composed to a significant extent of the natural polymer cellulose and closely related substances. Treatment of paper with nitric acid produced the first (semi-) artificial polymer, nitrocellulose. Dissolution of nitrocellulose in alcohol/ether gave a viscous solution (collodion) which forms a hard film upon solvent evaporation. The polymer thus formed was quite flammable. An improved product based on nitrocellulose, termed celluloid, was molded into... 

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. 

Biodegradable plastics can be based on natural or synthetic resins. Natural biodegradable plastics are based primarily on renewable resources (such as starch) and can be either naturally produced or synthesized from renewable resources. They are coming under polysaccharides (starch, cellulose, lignin, etc.), proteins (gelatine, wool, silk, etc.), lipid (fats and oil), polyesters produced by plant or microorganisms (PHA), polyesters derived... 

Plastics and elastomers are the names given to synthetic organic polymers manufactured from organic compounds of low molecular weight, called monomers, (e.g. ethylene, styrene, vinyl ehloride). The manufacture of plastics and elastomers can even be based on natural macromoleeular substances (e.g., natural rubber, cellulose, proteins). 

Although water is known as a natural plasticizer for many polar polymers such as nylon, polyester resins, and cellulosic polymers, similar behavior for polyacrylamide and poly(acrylamide-co-acrylic acid) has not been investigated. In this study, the effect of water content (and/or thermal history) on the Tg s of acrylamide-based pol3 TOers was studied by Differential Scanning Calorimetry (DSC), Thermogravimetry (TG), Thermomechanical Analysis (TMA), and Simultaneous Thermogravimetry - Mass Spectrometry (TG/MS). 

The formation of fibers from natural or synthetic materials depends on some specific factors. A material must have the correct plastic characteristics that allow it to be formed into fibers. Without exception, all natural plant fibers are cellulose-based, and... 

Natural fillers used in this study are not water soluble (two of them contain significant amounts of cellulose in their chemical composition) and randomly disperse within the starch plasticized matrix, and appears as a discontinuous phase after composite films drying (as evidenced by the scanning electron microscopy SEM investigation presented below). Therefore, these natural fillers provide more interfacial area within the composite films stmcture. As a result, light diffusion is enhanced, thus generating a reduced transparency property for the composite films. Overall, plasticized starch-based composite films exhibit some relative transparency mainly at low amount values for natural fillers in composite formulations. 

Acetylation treatment of natural fibers is originally applied to wood cellulose to stabilize cell walls against moisture, improving dimensional stability and envirormiental degradation [73]. Therefore, acetylation may contribute toward decreasing the moisture absorption of natural fibers [37]. Plasticization of cellulose-based natural fiber can be introduced by this treatment, which is related to an esterification method. During the treatment of natural fibers with acetic anhydride, the hydroxyl groups... 

Plastics are made up of polymers and other materials that are added to them to give the desired characteristics. Natural polymeric materials such as mbber, shellac and gutta percha have a long history as raw materials for man. The first thermoplastic, celluloid, was also manufactured from a natural product, from cellulose. Even today, there are still some cellulose based plastics, i.e., the cellulose acetates (CA). Cellulose is already composed of the large molecules that are characteristic of plastics (macromolecules). However, to manufacture CA plastics, they still have to be prepared with acetic acid. The first injection moulding machine was built and patented in 1872 in order to mould cellulose materials. 

An aqueous base is the least expensive vehicle and poses no toxicity problems. A solution of the drug in water or water and cosolvent is made. Glycerin, glycols, natural and synthetic gums, and/or polymers are used to increase viscosity, cohesiveness, and plasticity. To overcome syneresis, or water separation in the gel, a common problem with aqueous bases, one can use absorbing materials such as microcrystalline cellulose, kaolin, colloidal silicon dioxide, starch, etc. 

Plastics based on natural polymers Regenerated cellulose... 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly (vinyl acetate)—polytyinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system Poly(vinyl alcohol) is typically formed by hydrolysis of the poly (vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as well as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a colloid protection system. The protective colloids are similar to those used paint (qv) to stabilize latex. For poly (vinyl acetate), the protective colloids are isolated from natural gums and cellulosic resins (carboxymethylcellulose or hydroxyethylcellulose). The hydrolized polymer may also be used. The physical properties of the poly (vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended application. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly (vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. Applications are found mostly in the area of adhesion to paper and wood (see VlNYL POLYMERS). 

In this chapter, packaging materials based on cellulose or natural fibres will be discussed. They provide a major contribution to the packaging of pharmaceuticals, the size and nature of which can readily be overlooked since the number of applications is far more diverse and more paper and board is used than glass, metal or plastics. 

Another industrial application of gas-separation membranes is the removal of carbon dioxide from natural gas. The CO2/CH4, selectivity is about 20 to 30 for polycarbonate, polysulfone, and cellulose acetate membranes at 35°C and 40 atm. A selectivity of over 60 can be obtained with Kapton , but this polymer is much less permeable than the others. Increasing the temperature raises the permeability of most polymers but generally causes a. slight decrease in selectivity. The operating temperature is chosen to be somewhat above the dew point of the residue gas. There is considerable COj absorbed in the membranes at high CO2 partial pressures, and the plasticization effect of CO2 increases the effective diffusion coefficients for all gases and makes the selectivity less than that based on pure-gas data. Methods of allowing for such nonlinear effects have been presented. ... 

Because of their particle shape and nature, cellulose and other plant based or organic drugs and pharmaceutical excipients often exhibit elastic properties. For that reason, as mentioned several times in this book (see, for example. Chapter 5 and Section 10.2), after fast compaction densified products may experience spring-back and loose structural integrity, strength, and/or quality as defined by a multitude of descriptions. To overcome possible problems, the rate of densification must be lowered to potentially unacceptable (technically and/or monetary) levels to allow conversion of temporary elastic alteration in shape and volume into permanent plastic deformation. 

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