• Poly(hydroxyalkanoate)s
• Composites
• Biodegradation

The packaging industry nowadays relies strongly on the use of petroleum-derived plastic materials, which raises some concerns from both economical and environmental perspectives. The continuing use of finite oil resources implies a likely eventual decrease in availability and thereby increasing costs of raw materials. Furthermore, being non readily biodegradable, petroleum-based products can pose significant waste disposal problem in some area. Packaging is a substantial part of our everyday life, and the consumer use of packaging materials has shown a continuous increase over time. Packaging products manufactured from renewable materials currently only represent about 2% of the market, except the traditional fiber-based packaging.
The research work of my doctoral thesis, performed in the BIOLAB (Laboratory of Bioactive Polymeric Materials for Biomedical & Environmental Applications, Department of Chemistry and Industrial Chemistry, University of Pisa) facilities deals with the assessment of the biodegradation propensity in different media (soil, compost, river water) of synthetic polyesters (Ecoflex and Ecovio) and bio-based polymers such as poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), poly(lactic acid) (PLA) and their blends and composites loaded with fillers of organic (lignin), inorganic (montmorillonite named Dellite) nature and chain extenders (Joncryl).
The composites obtained by melt-blending and the neat polymers have been analyzed also for their processing profile and thermal properties (TGA, DSC) with the aim to know the effect of each component on the overall composite biodegradation behavior.
The experiments performed at the CNR-ISE (National Research Council-Institute of Ecosystem Study) have been essentially two topics.
In the first investigation, the potential eco-toxicological effects of polymer materials such as Polyethylene (PE) and Polystyrene (PS) in soil-plant systems (Avena sativa and Raphanus sativus) were studied; the PE and PS polymer effects were compared with those of the biodegradable materials Ecoflex and Cellulose, used as positive controls. Several chemical and biochemical parameters, usually used to assess soil quality and its response to xenobiotic compounds, have been selected in order to follow the effect of biopolymer degradation on soil properties. Polymers seemed to stimulate the soil metabolic activity during the time, thus indicating their possible biodegradation propensity in soil. These effects were more evident in Raphanus sativus plant treatments than in Avena sativa, suggesting the higher sensitivity of the former to the polymer treatments. At the end of experimentation, Ecoflex compared to PE and PS showed the higher nitrate/ammonia ratio and the lower water soluble carbon content (WSC), thus indicating its higher ability to promote the carbon cycle and in turn to activate organic nitrogen metabolism, bringing the soil plant system towards the nitrate nutrient production.
In the second experiment, the biodegradation of the PHB polymer, added to the soil at two different concentrations (1% and 2%) was investigated. The biodegradation process was followed by monitoring specific microorganisms and enzyme activities involved in PHB metabolism. Total microbial cultivable population and Pseudomonas genus significantly increased in both PHB dose treatments with respect to the untreated soil. The stimulation of microbial growth and activity was confirmed by the activation of the arylesterase and PHB depolymerase activities