Petroleum-based polyesters

Indeed, a large number of biodegradable polyesters are based on petrolenm resources, obtained chemically from synthetic monomers and polycaprolactone, poly-esteramide, or aliphatic/aromatic copolyesters can be distinguished. Generally, these petroleum-based polyesters are soft at room temperature since their glass transition temperatures are lower. 

Propanediol. In its racemic form, 1,2-propanediol is a petroleum-based high-volume chemical with an aimual production of over 500,0001, mostly used to manufacture the unsaturated polyester resins, yet also featuring excellent antifreeze properties. Enantiomerically pure (/ )-1,2-propanediol accumulates along two different pathways via DAHP (3-deoxy-D-flrahmo-heptulosonic acid 7-phosphate) and methylglyoxal, which then is reduced with either... 

Copper complex-catalysed carboxylation polycondensation of dibromoalkanes with arenediyls in the presence of carbon dioxide [scheme (17)], although producing low molecular weight polyesters in moderate yields, also represents pioneering efforts in the use of carbon dioxide as a non-petroleum-based carbon source [5],... 

In the end Monsanto didn t share that optimism. It decided to drop the program in late 1998. Michael Berezo, the Monsanto executive who had headed the Biopol program before the shutdown, told me in early 1999 that these materials cost about 10 times as much as comparably performing petroleum-based (and not biodegradable) commodity plastics, such as polyesters, some polyolefin, and polystyrenes. Berezo didn t consider biodegradability a big, positive selling aspect. ... 

Natural polymers such as starch and protein are potential alternatives to petroleum-based polymers for a number of applications. Unfortunately, their high solubility in water limit their use for water sensitive applications. To solve this problem thermoplastic starches have been laminated using water-resistant, biodegradable polymers. For example, polylactic acid and P(3HB-co-3HV) were utilised as the outer layers of the stratified polyester/PWS (plasticized wheat starch)/polyester film strucmre in order to improve the mechanical properties and water resistance of PWS which made it useful for food packaging and disposable articles [65]. Moreover, improved physic-chemical interactions between P(3HB-CO-3HV) and wheat straw fibres were achieved with high temperature treatment. It resulted in increased P(3HB-co-3HV) crystallization, increased Young s moduli and lowered values of stress and strain to break than the neat matrix of P(3HB-co-3HV). There was no difference in the biodegradation rate of the polymer [66]. 

As vegetable oil-modified polyesters have been studied over a long period of time, most known vegetable oils are now being utihsed to produce these polymers. Vegetable oil-based polyesters are used in almost aU the fields where a petroleum-based one can be used. These include protective coatings and paints, printing inks, varnishes and lacquers. 

Aliphatic polyesters are best known for their comparable properties to existing petroleum-based polymers biodegradability and resistivity to... 

This family of polyesters and copolyesters (Fig. 1.19) has inteested the polymer community both because of their remarkable physical properties and biodegradability. Efforts have been actively implemented to improve the economy of the biotechnological processes used to prepare these matraials, so that they can become commercially competitive compared with petroleum-based pol3mers with similar properties. All these aspects are thoroughly tackled in Chapter 22. 

During the last two decades the interest in biodegradable polyesters has increased immensely. There are at least two reasons for this. The first one is related to the steady increasing adverse environmental impacts of synthetic, petroleum-based polymers, and the second one to the unique opportunities for application of biodegradable polyesters in medicine, arising from their biocompatibility and biodegradability. 

Due to the rapidly increased production cost of fossil (petroleum)-based chemicals, fermentatively produced fumaric acid from renewable resources could replace current petrochemically based maleic acid as unsaturated dibasic acid mainly in the polyester resin industry but also in medicine and food industries in the nearby future. However, this can be achieved only if the bio-based production process for fumaric acid would be economically competitive with the current fossil-based process. This change requires the improvement of the large, past-operating fermentation processes for acid production in many aspects, such as production of free acid at a low pH, product yield and productivity, cheap and renewable raw material, and problems related to cell morphology and mass transfer. 

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