Thermo-Mechanical Behavior and Hydrolytic Degradation of Linear Low Density Polyethylene/Poly(3-hydroxybutyrate) Blends

Abstract

In this work, a commercial linear low density polyethylene (LLDPE) utilized for packaging applications was melt compounded with different amounts (from 10 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 behavior 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.%.

Blending of Low-Density Polyethylene and Poly(Butylene Succinate) (LDPE/PBS) with Polyethylene–Graft–Maleic Anhydride (PE–g–MA) as a Compatibilizer on the Phase Morphology, Mechanical and Thermal Properties

“…These outcomes were expected and can be explained by the fact that the obtained blends led to non-homogenous structures and decreased polymer adhesion, which resulted in void spaces that decreased network strength [ 49 ]. The same result (6.42 MPa) was observed in the case of LDPE/PLA (80/20) compared to pure LDPE with 13.3 MPa [ 50 ] and LLDPE/PHB (80/20), which exhibited a low value (10.0 MPa) as compared to the LLDPE reference (16.6 MPa) [ 16 ] due to the immiscibility of the blends and poor interfacial adhesion between two polymers. Therefore, the decrease in tensile properties seems to reflect the low degree of miscibility and minimal interfacial contact among the two polymeric components of these blends, as discovered in morphological characterization.…”

“…There will be no discernible differences in the FTIR spectra if two polymers formed completely immiscible blends with regard to the incorporation of each component. Conversely, when two polymers are miscible, a chemical interaction occurs between the chains of two different polymers, changing the blend’s IR spectra [ 16 ]. As a result, FT-IR spectroscopy can provide information about the potential interaction of LDPE and PBS with or without PE–g–MA, as shown in Figure 1 .…”

“…Meanwhile, the total substitution of synthetic plastic with biodegradable polymers is an inefficient process since biodegradable polymers are costly and have low performance and a limited shelf life [ 14 ]. Therefore, manufacturing PE combined with biodegradable counterparts, including poly(butylene succinate) (PBS) [ 15 ], polyhydroxybutyrate (PHB) [ 16 ] and poly(lactic acid) (PLA) [ 17 ], has attracted considerable interest as a result of the potential to reduce the cost for large-scale applications and improving the properties of end-products and reducing the environmental issues.…”

Study and Characterization of the Dielectric Behavior of Low Linear Density Polyethylene Composites Mixed with Ground Tire Rubber Particles

“…Thus, this research is focused on particles of GTR with a diameter under 200 µm. For this purpose, it was used as a matrix LLDPE, which has good electrical, processing and mechanical properties as well as relatively low price [28][29][30]. In general, the incorporation of fillers in LLDPE increases the elastic modulus of the material and its tensile strength, but often decreases the elongation at break [31,32].…”

Commercial Marine-Degradable Polymers for Flexible Packaging

“…These semi-degradable blends can fragment and show signs of biodegradation in aerobic and anaerobic conditions, but the residual polyolefins are resistant to microbial attack and biological assimilation ( Portillo et al., 2016 ; Leja and Lewandowicz, 2010 ; Kyrikou and Briassoulis, 2007 ; Al-Salem et al., 2019 ). Oxo- and semi-degradable polymers streamline the creation of microplastics rather than accelerating biodegradation ( Obasi et al., 2020 ; Rigotti et al., 2020 ; Portillo et al., 2016 ). If oxo- and semi-degradable polyolefins were to be regarded as sustainable replacements for today's single-use packaging, these materials would persist in marine environments.…”