Deliverable 3.5 - Thermoplastic durables and biocomposites
The technical activities aimed at obtaining engineered thermoplastic materials composed of PHA generated from biowaste were successfully carried out by SABIO and by INRA.
In particular, SABIO focussed firstly on evaluating properties of PHA obtained from biowaste, secondly on a study aimed at the design of the compositions of the materials containing PHA obtained from biowaste and thirdly on the implementation into production process of these innovative formulations.
The result of these activities is a sample (in form of pellets) of a material containing a relevant share of PHA proceeding from biowaste (MIX 3).
The material containing PHA obtained from biowaste was benchmarked against a traditional oilbased material currently used for the manufacturing of parts of electronic devices.
Further evaluations were performed in order to assess the implementability of the material containing PHA obtained from biowaste into process that are currently used to manufacture objects. In this way it was also possible to assess additional technological properties and verify the feasibility of the substitution of traditional oilbased material with a material based containing PHA obtained from biowaste. The technical activity performed by SABIO brought the evidence that it is possible to make use of materials containing PHA obtained from biowaste in place of traditional thermoplastics for the production of parts for consumer electronic industry.
With reference to INRA’s activity, the objective of the work was to convert green Park and Garden waste into fillers and to study their potential reinforcing effect in PHA-based biocomposites. For this purpose, a typical sample of green park or garden waste was collected by DTU at the Copenhagen waste management facilities, open air dried and then sent to INRA for characterization and further processing. Five valuable fractions could be produced from park and garden green wase, i.e branches (23 wt%), leaves (5 wt%), grasses (3 wt%), a medium size fraction containing particles which are retained by the sieve (higher than 4.0 mm) (9 wt%), and a fine Fraction (47 wt%) contained the smallest particles (lower than 4.0 mm) and a large amount of soil which passed through the sieve (lower than 4.0 mm). A last fraction was identified, corresponding to the unusable fraction (13 wt%) and comprising soil, stones and foreign objects (paper and cardboard, glass, cigarette butts, cans, etc…).
This study demonstrated that all lignocellulosic fractions produced from parks and gardens wastes could be rather considered as filling agents rather than reinforcing fillers since the mechanical properties of the tested PHA matrices were not improved, but at the best preserved. Filler contents up to 30 wt% were used. It was shown that the branches fraction displayed the best reinforcing effect, whereas the grasses fraction is significantly degrading the overall mechanical performance. We can thus advice, in view of up-cycling this solid waste for composite application, to remove grasses from green park and garden wastes, and/or to keep only branches. It was shown that better mechanical properties and higher thermal stability were obtained when decreasing the size of fillers down to an average apparent diameter of about 20 μm.
First biocomposites were produced using a PHBV grade developed in the frame of the RESURBIS project, with a HV content of 19 mol% and produced from mixed cultures. It was shown that lignocellulosic fillers could play an interesting nucleating effect. It is worth noting that the neat PHBV copolymer produced and purified in the frame of the project displayed poor mechanical properties. In the future, the impact of purification and processing conditions on the overall performance of materials should be explored. In conclusion, depending on the overall targeted performance, the whole sample could be used, including residues of soil or not, and RES URBIS (GA 730349) the filler size could be controlled and adjusted accordingly. The development of biocomposites could be thus a very interesting strategy to decrease the overall cost of PHA-based materials, while up-cycling solid urban waste.
For the sake of simplicity, the two activities by SABIO and INRA are separately reported in Sections 1 and 2, respectively.