Evaluation of the Mechanical and Thermal Properties Decay of PHBV/Sisal and PLA/Sisal Biocomposites at Different Recycle Steps

Abstract

The recyclability of polylactide acid (PLA) and poly (3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV)-based biocomposites (10%, 20% and 30% by weight of sisal natural fibre) was evaluated in this work. The mechanical and thermal properties were initially determined and were shown to be similar to commodity plastics, such as polyethylene or polypropylene. Three recycle steps were carried out and the mechanical and thermal properties of recycled samples were evaluated and compared to the reference samples. The tensile modulus increased for recycled PLA biocomposites, whereas it was hardly influenced by recycling the PHBV biocomposites. The tensile strength and deformation at the break decreased notably after the first cycle in all cases. Although all the biocomposites became more brittle with recycling, the properties were conserved along until the third cycle, proving their promising recyclability. From the data obtained from the dynamic mechanical analysis, a slight decrease of the storage modulus of PHBV was observed, whereas PLA showed a significant decay of its properties at the 3rd recyclate. The PLA specimens were filled with sisal fibres until they reached 20%wt, which seemed also less subject to the embrittlement occurring along the recycling phase. The characteristic temperatures (glass transition-Tg, crystallization-Tc, melting-Tm) of all the biocomposites were not highly affected by recycling. Only a slight decrease on the melting point of the recycled PHBV was observed suggesting an overall good reprocessability. Moreover, the processing conditions lied in the same range as the conventional plastics which would facilitate potential joint valorization techniques.

Environmental Degradation of Plastic Composites with Natural Fillers—A Review

“…Biocomposites of PLA and PHBV with 10%, 20%, and 30% sisal fibers became more brittle but had acceptable overall properties after two recycling steps, with only tensile strength and deformation at break decreasing after the first processing step. After the third recycling, the composite with PHBV had a slight decrease of storage modulus while the one with PLA showed significant loss of properties [45]. Oak wood fiber (50%) and PLA-g-MA as the coupling agent limited the reprocessing of PLA composites to two cycles, after which a sharp decrease in mechanical properties was observed.…”

The Influence of Compatibility on the Structure and Properties of PLA/Lignin Biocomposites by Chemical Modification

“…The most important finding was that the individual constituents and the interactions of matrix-filler played a significant role on the dynamic mechanical properties of the biocomposites. In addition, the adhesion between the polymer matrix and the filler is evaluated by DMA technique [43]. Figure 11 displays the E , E", and tanδ of pure PLA, PLA/Ac-lignin, PLA/At-lignin, and PLA/By-lignin biocomposites as a function of frequency.…”

Influence of the Degradation Medium on Water Uptake, Morphology, and Chemical Structure of Poly(Lactic Acid)-Sisal Bio-Composites

“…Agave Sisalana (also known as sisal) with concentrations up to 30% w / w has been proved to be an adequate filler for PLA, improving its mechanical, thermal, and water uptake performance [ 9 , 10 ]. In addition, the characteristic properties of these bio-composites are retained after several recycling cycles, which would foster valorization techniques [ 11 ].…”