Other Biodegradable Polymers

Biodegradable polymers such as PVA, PVAc, and PGA have been used in bio-nanocomposites, but to a less extent compared to polymers such as PCL, PLA, and PHB. Nonetheless, these polymers, among other factors, can be used as model to prepare bionanocomposites with hydrophilic material such as clays and CNWs. Moreover, nanobiocomposites based on these polymers can be potentially used as bioscaffolds for cell growth among other applications. 

This study was prepared by the Swiss Research Institute for Agriculture (Eidgenossische Forschungsanstalt fiir Agrarwirtschaft und Landtechnik, FAT) and the environmental consultancy CARBOTECH for the Swiss Federal Office of Agriculture. It contains LCA results for three products (in the FAT/CARBOTECH Study (1997), these three products are referred to as No.3, No.lO and No.l2). 

For kenaf mulch films (i), the LCA shows large advantages compared to the PE alternatives for all indicators except for eutrophication. Disadvantages have, however, been determined for biodiversity, soil fertility and economics (these parameters were not studied as part of the LCA). The two products made of miscanthus (ii, iii) clearly score better than or at least as good as their counterparts based on fossil fuels. In these cases, unresolved technical issues and the forthcoming commercialisation represent the main challenges for the future. 

A comparison of the life cycle inventory results for pellets, loose fills and films/bags is given in Table 13.9. Only those impact categories are listed for which at least one dataset was available by type of product. 

For starch polymer pellets energy requirements are mostly 35%-70% below those for PE and GHG emissions are 30%-80% lower (disregarding differences that result from differences in waste management). Starch polymers also score better than PE for all the other indicators listed in the table with eutrophication being the sole exception. The lower the share of petrochemical copolymers, the smaller the environmental impact of starch polymers generally is. However, the application areas for pure starch polymers and blends with small amounts of copolymers are limited due to inferior material properties. Hence, blending can extend the applicability of starch polymers and thus lower the overall environmental impact at the macroeconomic level. 

By comparison to loose fills, the range of results for starch polymer films and bt s is to a large extent understandable from the differences in film thickness. Taking this factor into account, the environmental impacts of the starch films/bags are lower with regard to energy, GHG emissions and ozone precnrsors. The situation is less clear for acidification. For eutrophication, PE films tend to score better. 

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McCormick, C.L., D.K. Lichatowich, and M.M. Fooladi, "Controlled Activity Pendant Herbicide Systems Utilizing Chitin and Other Biodegradable Polymers," Proceedings of the 5th International Symposium on Controlled Release of Bioactive Materials, pp. 3.6-3.17, Gaithersburg, MD (1978). 

A special group of carrier-linked prodrugs are the site-specific chemical delivery systems [23], Macromolecular prodrugs are synthetic conjugates of drugs covalently bound (either directly or via a spacer) to proteins, polypeptides, polysaccharides, and other biodegradable polymers [24],... 

It is a local haemostatic and antiseptic agent. The haemostatic effect of feracrylum is based on the formation of synthetic complex consisting of its adduct with plasma proteins principally albumin. Like other biodegradable polymers, the feracrylum-albumin complex formed gets broken down over a period of time. 

A particular mention goes to Mater-Bi, produced by Novamont, who have revolutionised starch-based biomaterials for two decades. The commercial success of this biodegradable and biocompostable plastic relies on two main factors the scale economy that allows the reduction of costs, and the diversity of formulations to develop different end products (plastic bags, tableware, toys, etc.). More than 210 references in Chemical Abstracts are available on this (registered) keyword, and the number of patents related to different formulations and developments is also impressive. Mater-Bi can be essentially described as a blend of starch with a small amount of other biodegradable polymers and additives. The actual compositions are still known only by a very few people. 

Starch-based biopolymers are lower cost materials than some other biodegradable polymer types such as synthetic co-polyesters and PLA. They are produced from relatively cheap agricultural feedstock and have simpler manufacturing processes compared with synthetic biopolymers. 

Gas barrier properties - Metabolix PHA polymers have lower moisture vapour transmission rates than other biodegradable polymers. The oxygen transmission rates for unoriented PHA films are 25-30 cc-mil/(100 in2-day) at 77 °C, 0% relative humidity. 

Biodegradability - Metabolix PHA offer hydrolytic stability under normal service conditions but when exposed to microbial organisms naturally present they break down enzymatically in soil, composting, waste treatment processes, river water and marine environments. They also rapidly decompose to carbon dioxide and water and will degrade in anaerobic environments, unlike some other biodegradable polymers. 

Nodax can be blended with other biodegradable polymers such as polylactic acid and thermoplastic starch for improved processing performance. 

Other biodegradable polymers studied by solid-state NMR... 

U.S. Pat. No. 6,274,652 [127] discloses a biodegradable composite material comprising bacterial cellulose in a powdery state and a polymeric material such as poly-hydroxybutyrate, polyhydroxyvalerate, polycaprolactone, polybutylenesuccinate, polyethylenesuccinate, polylactic acid, polyvinylalcohol, cellulose acetate, starch, and other biodegradable polymers. 

Other biodegradable polymers include polyanhydrides, which are suitable for the fabrication implantable controlled release microspheres. Since polyanhydrides undergo hydrolysis in aqueous medium often their microspheres are prepared using Oi/On emulsion technique. ... 

Poly(butylene succinate) is often used in blends with other biodegradable polymers like starch [109], PLA [110-114] and PHAs [115,116]. In many cases PBS is added to other biopolymers to improve properties like heat stability (heat distortion temperature) and impact resistance, and to improve processing behaviour. Although PBS and PLA are immiscible, compatibility is sufficient to allow preparation of blends with good mechanical properties [92, 105]. Peroxides can be used to improve the compatibility of the blend leading to improved impact strength [117]. 

Totally biodegradable blends are polymer mixtures containing PHAs and another (or other) biodegradable polymer(s) as components. The blending of PHAs with certain biodegradable polymers usually improves the biocompatibility and the... 

Blends of various PHAs or PHAs with other biodegradable polymers are commonly used for adjusting the properties of the final materials, while maintaining their biodegradability. The blends of two different PHAs are usually immiscible [175], at least in the crystalline state [176], even in the case of a blend of isotactic bacterial PHB and synthetic atactic PHB, which is miscible only in a limited concentration range [177]. 

The same approach was apphed to other biodegradable polymers, important for biomedical apphcations, such as PHB and poly(caprolacton) (PCL). The morphology of the scaffold materials of these polymers is demonstrated in Figure 9.6. 

Other biodegradable polymers include Konjac, a water-soluble natural polysaccharide produced by FMC Chitin, another polysaccharide that is insoluble in water and Chitosan, which is soluble in water. Chitin is found in insects and in shellfish. Chitosan can be formed from chitin and is also found in fungal cell waUs. Chitin is used in many biomedical applications, including dialysis membranes, bacteriostatic agents, and wound dressings. Other applications include cosmetics, water treatmenfi adhesives, and fungi-cides. y... 

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