Modified, Natural Biodegradable Polymers

More recently, in the last 25 years, it has become increasingly apparent that, in addition to the major commodity synthetic plastics, water-soluble commodity and specialty polymers and plastics, such as poly(acrylic acids), polyacrylamide, poly(vinyl alcohol), poly(aIkylene oxides), and even some modified natural polymers, for example, cellulosics and starch, may potentially contribute to environmental problems and should also be targets for biodegradable substitutes. 

Results from biodegradation studies on numerous synthetic polymers, polymer blends, modified natural polymers and biopolymers have been reported. However, as pointed out earlier, biodegradability of a polymer is a function of several variables, including, but not limited to, the following. 

For ease of discussion, this section is divided into three broad classifications — natural, synthetic, and modified natural based biodegradable polymers and plastics. Natural polymers indicate no modification of isolated polymer, synthetic poisoners include carbon chain and heteroatom chain polymers, and modified natural polymers encompass grafts and blends, and chemical modifications such as oxidations and esterifications. 

Modified natural polymers offer a way of capitalizing on their well accepted biodegradability of natural polymers to develop environmentally acceptable... 

There are various ways to classify polymers. A simple way is to distinguish polymers with respect to their origin in synthetic and natural polymers. Natural polymeric materials such as shellac, cellulose, and natural rubber have been used for centuries. Natural polymers are a class of polymers derived from renewable biomass sources, such as plants, vegetable oil, com starch, pea starch. Generally, natural polymers (or biopolymers) are used after modification reactions. Some biopolymers are designed to biodegrade. Table 2.1.1 and Fig. 2.1.1 give examples of natural polymers and modified natural polymers. 

Based on the properties of the polymeric material, polymeric drug delivery systems (DDS) can be classified as non-degradable DDS or biodegradable DDS. Table 16.2 lists some of the most commonly used polymers in the preparation of DDS. This list includes synthetic, natural and modified natural polymers. Although natural polymers and their derivatives, as for example chitosan and gelatin [4,18], are also used in the development of ODDS, this work will be focused solely on synthetic polymers and on the ODDS based on these polymers. 

Therefore, is appropriate to study the sorption properties and ready biodegradability compositions based on ultrafme powders LDPE modified natural polymers HTZ under the combined effects of high-pressure and shear deformation. 

Water-soluble polymers may be anionic, cationic, or nonionic in character, which influences both their applications and their biodegradability. They may be totally synthetic, totally natural, or synthetically modified natural polymers. 

Biodegradable polymers and plastics are readily divided into three broad classifications (/) natural, (2) synthetic, and (J) modified natural. These classes may be further subdivided for ease of discussion, as follows (/) natural polymers (2) synthetic polymers may have carbon chain backbones or heteroatom chain backbones and (J) modified natural may be blends and grafts or involve chemical modifications, oxidation, esterification, etc. 

They are made of polymeric, waxy, or other protective materials, that is, biodegradable synthetic polymers and modified natural products such as starches, gums, proteins, fats, and waxes. The natural polymers include albumin and gelatin " the synthetic polymers include polylactic acid and polyglycolic acid. ... 

Hydrophobically modified polymers can associate in aqueous media to form micelle-like structures above their critical association concentrations (CACs). The nanosized self-aggregates were prepared using modified natural polysaccharides such as pullulan, curdlan, and glycol chitosan. The modified polysaccharides provide excellent biocompatibility, biodegradability, low immunogenicity, and biological activities. 

Some cellulose derivatives and P(3HB) and P(3HB-co-3HV) have been found to show good compatibility [114-116]. These are chemically modified natural and natural biodegradable polymer blend systems. Blends obtained by melts compounding P(3HB) with cellulose acetate butyrate (CAB, degrees of butyrate and acetate substitution are 2.50 and 0.18, respectively) have been found to be miscible over the whole composition range by DSC and dynamic mechanical spectroscopy [116]. 

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