Abstract
In this work, a commercial linear low density polyethylene (LLDPE) utilized for packaging applications was melt compounded with different amounts (from 10 wt% up to 50 wt%) of poly(3-hydroxybutyrate) (P(3HB)), with the aim to evaluate the possibility to partially replace LLDPE with a biodegradable matrix obtained from renewable resources. The processability, microstructural and thermo-mechanical behaviour of the resulting blends was investigated. Melt flow index (MFI) values of the LLDPE matrix were not much affected until a P(3HB) content of 20 wt%, while for higher P(3HB) concentrations an evident decrease of the viscosity was detected. Scanning electron microscope (SEM) observations on the blends highlighted that at limited P(3HB) concentrations the secondary phase was homogeneously dispersed in form of isolated domains, while at a P(3HB) content of 50 wt% a continuous layered morphology could be detected. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) did not evidence any chemical or physical interaction between the two polymer phases. Quasi-static tensile tests and dynamical mechanical analysis showed that the introduction of P(3HB) led to a pronounced stiffening effect, while the progressive drop of the yield and ultimate mechanical properties could be attributed to the weak interfacial adhesion and poor compatibility between the two matrices. The resistance to hydrolytic degradation of the LLDPE/P(3HB) blends was evaluated over a period of 100 days of immersion in water at 50 °C. It was observed that the weight variation and the decrease of the tensile properties due to the hydrolytic process on the biodegradable phase were evident only for a P3HB content of 50 wt%. In conclusion, this work showed that the partial replacement of LLDPE with a biobased P(3HB) could lead to the development of an innovative blend with good processability and mechanical properties, until a P(3HB) amount of 20 wt%.
Highlights
In the last few decades global climate change and ecosystems deterioration have been the main driving forces for a progressive switch from a take-make-dispose economy based on continuous growth and increasing resource throughput to a circular economy in which resource input, waste, emission, and energy leakage are minimized by slowing, closing, and narrowing material and energy loops (Geissdoerfer et al, 2017)
In order to evaluate the processability of the resulting blends, melt flow index (MFI) measurements were performed according to ASTM D1238–04 standard, by using a Kyeness 4003DE plastomer at a temperature of 180◦C under a load of 2.16 kg investigating about 10 g of material for each sample
Considering that the selected linear low density polyethylene (LLDPE) grade is generally used for the production of extruded film for food packaging, it is clear that the retention of the original Melt flow index (MFI) is a fundamental processability requirement for this process (Van Krevelen and Te Nijenhuis, 2009)
Summary
In the last few decades global climate change and ecosystems deterioration have been the main driving forces for a progressive switch from a take-make-dispose economy based on continuous growth and increasing resource throughput to a circular economy in which resource input, waste, emission, and energy leakage are minimized by slowing, closing, and narrowing material and energy loops (Geissdoerfer et al, 2017). In order to evaluate the processability of the resulting blends, melt flow index (MFI) measurements were performed according to ASTM D1238–04 standard, by using a Kyeness 4003DE plastomer at a temperature of 180◦C under a load of 2.16 kg investigating about 10 g of material for each sample.
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