Processability of biodegradable polymers

Lee, S. and Lee, J.W. (2005) Characterization and processing of biodegradable polymer blends of poly (lactic acid) with poly(butylene succinate adipate). Kor.-Aust. Rheol. J., 17,... 

Many efforts have been made to improve the mechanical properties of PHB and PHBHV. The combination of osteoconductive properties of HAp with the processability of biodegradable polymer can overcome limitations induced by the brittleness and can widen the application potential in bone tissue engineering. 

The properties of polymers are not only determined by their primary chemical structure but also by secondary structural elements. This is also tme for the process of biodegradation. In a first step, the secondary structures of the polymer, e.g., crystals in a partially crystalline polymer, have to be dissolved during the degradation process and temporarily flexible chains formed. 

Extrusion is a continuous conversion process via melting and subsequent transformation of granules or powders of biodegradable polymers and additives into semifinished or finished articles like sheets, profiles, tubes, bottles, films, tapes or... 

Mader, K., Gallez, B., Liu, K.J., and Swartz, H.M. (1996). Non-invasive in vivo characterization of release processes in biodegradable polymers by low-frequency electron paramagnetic resonance spectroscopy. Biomaterials, 17, 457-461. 

Weisel, J. W., and Cederholm-Williams, S. A. (1997). Fibrinogen and fibrin Characterization, processing and medical applications. In Handbook of Biodegradable Polymers (A. J. Domb, J. Kost, and D. M. Wiseman, Eds.), pp. 347-365. Harwood, Amsterdam. 

Product development and improvement has a crucial role to play in the further development of the biodegradable polymers market. These include development of more reliable and lower cost raw materials for manufacture of biodegradable polymers, improvement in performance properties vis-a-vis standard thermoplastics, improvement in processing performance and development of new polymers and blends. 

At the moment, there are a growing number of biodegradable polymers performing well in niche applications. Many of these materials can be even more cost competitive in the future compared to petroleum-based resins including PET, polyethylene (PE), and polypropylene (PP) as suppliers develop better material properties that can lead to thinner films or lower processing costs. 

The production of biodegradable polymers using carbon as the starting material can be carried out using a 3-stage or a 2-stage process. 

While, synthetic biodegradable polymers are more costly than either starch-based or PLA polymers, they often have better physical and mechanical properties than types of biodegradable polymers based on renewable resource. These include higher strength, better clarity, better barrier properties and a greater ease of processing. 

Vertex is actively involved in the commercialisation of biodegradable polymers and uses Nature Works PLA material. The company initiated a development project to ascertain the technical and commercial viability of PLA in 2003, which has resulted in a decision to supply various stock products made from PLA. These include disposable cups, fresh food containers including deli containers and salad bowls, bakery containers including sandwich wedges, bottles, food trays and extruded sheet for further processing. 

The report starts with an overview of biodegradable polymers including an examination of the processes of biodegradation, classification of biodegradable polymers including their chemical structure, properties, and processing performance. 

Clearly, the deposition of a variety of microbial genera and their adaptation to live on an environment with limited nutrient availability are important in the colonization process of the polymer surface and subsequent degradation. The capability of these genera for secretion of extracellular enzymes and production of low-molecular-weight metabolites aids in the establishment of successive microflora and hence intensifies the biodeterioration and biodegradation processes (Webb et al., 1999, 2000). 

---