Other Biodegradable Plastics

There are a number of other families of biodegradable plastics, most at an earlier stage of development than those discussed above. Examples include protein-based 

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In 2004, Office Media (Tokyo) developed a new PLA film exhibiting vastly improved functionality as a packaging material. Through combination with other biodegradable plastics, the film s transparency, flexibility, heat resistance and impact resistance, have been balanced in multiple dimensions, and through adopting two-layer and three-layer structures, gas barrier properties have also been improved. Technology to eliminate the characteristic odour of PLA developed independently by Office Media, have also been applied. 

Compared with most other biodegradable plastics and/or bio-based plastics, PLA is by far the most important and promising one. The leading position of PLA is demonstrated by the current scale of the PLA industry, the number of pilot projects announced or under construction, the numerous products and applications of PLA in biodegradable and/or bio-based polymer markets, the number of polymer companies and converters involved with PLA, the news and attention created by PLA, the patents and publications related to PLA, etc. 

Students could also investigate or research other biodegradable plastics. The Other resources section at the end of the chapter provides further details. 

A comparison of the physical properties of PHBV with those of other biodegradable plastic... 

The market is ready for biodegradable plastics in many diffoent areas of application, if they prove to have acceptable processing parameters, ultimate propraties and viable prices. Since other biodegradable plastics are developing rapidly, for example polylactic acid (see Chapta- 21) and starch (see ChaptCT 15), if PHAs should aspire to be among them, their competitive industrial production should start soon. 

Masaki, K., Kamini, N.R., and Ikeda, H. (2005) Cutinase-like enzyme from the yeast Cryptococcus sp. strain S-2 hydrolyzes polylactic acid and other biodegradable plastics. Appi Environ. Microbiol, 71, 7548-7550. 

Polyesters and polyamides are the most prevalent of this type of polymer. Poly(ethylene terephthalate) is used in bottle manufacture and along with other packaging plastics is not biodegradable. Potts(54) established very early that only low melting and low molecular weight aliphatic polyesters were biodegradable. 

Several CDs applications have been discussed in Chapter 6. Their lack of toxicity forms the basis for their applications in pharmaceutical, agrochemical, and food industries as well as in toiletry and cosmetics [lb, lc]. They are also used or have been proposed to be applied, as sensitizers and stabilizers of dyes in photography, for impregnating paper, as fluorescent and other sensors [28], as corrosion inhibitors and rust proofing materials, UV stabilizers and antioxidants. One of the most spectacular is the prospective use of CDs as biodegradable plastics [29]. The complex of nitroglycerine with p-CDmarketed in Japan was mentioned in Chapter 1 while some other CDs applications have been presented in Chapter 6. 

Figure 14.24a), have been developed. Other common categories of degradable plastics include synthetic biodegradable plastics which are broken down by bacteria, as well as plastics which dissolve in water (Figure 14.24b). The property that allows plastic to dissolve in water has been used in relatively new products, including soluble capsules containing liquid detergent. However, the vast majority of polymers are still non-biodegradable.

The most immediate advantage of making biodegradable plastics is to address the problems of litter and marine pollution resulting from plastics disposal, which are difficult to solve any other way. 

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. 

Loose-fill packaging was one of the first successful areas of application for starch-based biodegradable polymers. Loose-fill starch-based foam is used for packaging consumer products as an alternative to polystyrene and polyethylene. While, biodegradable plastics have made some inroads into these markets, the future prospects for their growth in loose-fill are not so exciting as they are in some other areas of packaging. 

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