Starch-based polymers producers

Torres et al. (2006) reported a novel microwave processing technique to produce biodegradable scaffolds for tissue engineering from different types of starch-based polymers. Potato, sweet potato, com starch, and non-isolated amaranth and quinoa starch were used along with water and glycerol as plasticizers to produce porous stmctures. Figure 16.1 shows the manufacturing procedure of microwaved starch scaffolds. 

The focus of this work was to determine if a glyco-peptide or a simple dextrinized, oxidized starch could be produced which would enhance the behavior of a starch-based polymer for spray dried flavoring production. Enhancement of a starch s lipophilic/hydrophilic balance was anticipated to maintain the polymer s film forming" and cohesive wall development during the spray drying process while improving its emulsifying/interfacial activity capabilities. 

There is also US research interest in using pectin in polymer applications. Pectin is a complex plant cell wall heteropolysaccharide (based on galactose, rhamnose, arabinose and xylose) that can be blended with synthetic polyvinyl alcohol (PVA) to produce biodegradable polymers with a wider range of properties than those of starch-based polymers alone. The new pectin/PVA biodegradable polymer should be capable of replacing conventional PVA applications in blow-moulded, extruded, film and injection-moulded applications. 

Starch has been considered an attractive raw material for polymer applications for almost 200 years. Kirchoff s discovery in 1811 that treatment of starch with an acid yields a sweet substance was an unexpected result of the search for a low-cost substitute for natural rubber.1 Considerable research in the development of starch-based polymer materials has been stimulated by the facts that starch is produced from wide variety of sources, is an annually renewable resource and is inherently biodegradable. 

Biopolymers are polymers that were produced from renewable natural sources, which are biodegradable, and are not toxic. These can also be produced by biological systems (i.e., microorganisms, plants and animals) or chemically synthesized from biological starting materials (e.g., sugars, starch, natural fats, oils, etc.). These biopolymers are an alternative source to petroleum-based polymers traditional plastics. The biopolyesters have properties similar to traditional polyesters. Starch-based polymers are often... 

Starch-based polymers can be produced from potato, com, wheat, cassava, or tapioca. In the United States and Europe, com starch is the predominate source for starch-based polymers. Corn starch is mostly used for animal feed. Starch-based polymers can be processed on traditional thermoplastic forming operations of injection molding, extmsion, blow molding, compression molding, rotational molding, etc. Starch can be made from corn or vegetable oils and other renewable sources. The most common plasticizers for starch are water and glycerol. 

The third source of LCI data for starch-based polymers was produced for a Swiss Federal Agency for the Environment (Patel et al. 2003). The assumptions were cradle-to-gate LCI and end-of-hfe options are ignored. The functional unit was 1 kg of plastic. 

The polymers discussed up until now have all been made synthetically, however, polymers also occur naturally and are produced by microorganisms, plants and animals. Polymers that are produced by living organisms are called biopolymers. The monomers in this case can be materials such as sugars, amino acids and nucleic acids and by polymerisation can produce starch based polymers or protein based polymers. We have biopolymers inside us all - nucleic acid which produces our own DNA is a biopolymer. 

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. 

Biobased polymers from renewable materials have received increased attention recently. Lactate is a building block for bio-based polymers. In the United States, production of lactic acid is greater than 50,000 metric tons/yr and projected to increase exponentially to replace petroleum-based polymers. Domestic lactate is currently manufactured from corn starch using the filamentous fungus Rhizopus oryzae and selected species of lactic acid bacteria. The produced lactic acid can then be polymerized into polylactic acid (PLA) which has many applications (Hatti-Kaul et al., 2007). However, so far, no facility is built to use biomass derived sugars for lactic acid production. More research needs to be done to develop microbes using biomass derived sugars for lactate production. 

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. 

Starch blends have better physical and mechanical properties than pure plant based polymers, which open up more application possibilities. For example, starch blends can produce film with better moisture barrier protection and higher clarity. Also in film packaging made from starch blend, the perforations that are normally required can be dispensed with because the optimum moisture content soon establishes itself automatically, even in freshly packaged fruit and vegetables. 

Under the Mater-Bi trademark, Novamont produces different classes of starch-based biodegradable materials and blends of starch with synthetic polymers. Each class is available in several grades to meet the needs of specific applications. Classes include grades for film and sheet extrusion, injection moulding and foams. 

Nvyro was established to produce cassava (tapioca) starch based packaging solutions. Tapioca is one of the cheapest sources of raw materials for manufacture of starch based biodegradable polymers. 

While biodegradable polymers may be similar to petrochemical-based thermoplastics in terms of their structure, their chemical structure imbues them with technical properties that make them perform in different ways. For example, starch blends can produce film with better moisture barrier protection and higher clarity than some conventional plastics. PLA has a high water vapour transmission rate, which is beneficial for fresh food applications where it is important that the water vapour escapes quickly from the packaging. PLA also reduces fogging on the lid of the packaging. 

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