Accelerated Weathering Testing (AWT) and Bacterial Biodegradation Effects on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/Rapeseed Microfiber Biocomposites Properties

Abstract

In the context of sustainable materials, this study explores the effects of accelerated weathering testing and bacterial biodegradation on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/rapeseed microfiber biocomposites. Accelerated weathering, simulating outdoor environmental conditions, and bacterial biodegradation, representing natural degradation processes in soil, were employed to investigate the changes in the mechanical, thermal and morphological properties of these materials during its post-production life cycle. Attention was paid to the assessment of the change of structural, mechanical and calorimetric properties of alkali and N-methylmorpholine N-oxide (NMMO)-treated rapeseed microfiber (RS)-reinforced plasticized PHBV composites before and after accelerated weathering. Results revealed that accelerated weathering led to an increase in stiffness, but a reduction in tensile strength and elongation at break, of the investigated PHBV biocomposites. Additionally, during accelerated weathering, the crystallinity of PHBV biocomposites increased, especially in the presence of RS, due to both the hydrolytic degradation of the polymer matrix and the nucleating effect of the filler. It has been observed that an increase in PHBV crystallinity, determined by DSC measurements, correlates with the intensity ratio I_1225/1180 obtained from FTIR-ATR data. The treatment of RS microfibers increased the biodegradation capability of the developed PHBV composites, especially in the case of chemically untreated RS. All the developed PHBV composites demonstrated faster biodegradation in comparison to neat PHBV matrix.

Keywords: N-methylmorpholine N-oxide treatment; accelerated weathering; alkali treatment; biocomposite; biodegradation; poly(3-hydroxybutyrate-co-3-hydroxyvalerate); rapeseed microfibers.

Figure 3

Young’s modulus E (a), stress at break σ_B (b), and ultimate deformation ε_B (c), of the PHBV and PHBV biocomposites before accelerated weathering and after 250 h and 500 h of the combined exposure of UV irradiation, temperature, water sprinkling and condensation.

Figure 3

Young’s modulus E (a), stress at break σ_B (b), and ultimate deformation ε_B (c), of the PHBV and PHBV biocomposites before accelerated weathering and after 250 h and 500 h of the combined exposure of UV irradiation, temperature, water sprinkling and condensation.

Figure 1

Change of colorimetric parameters L* (a) and ΔE (b) with accelerated weathering time.

Figure 2

DSC thermograms change of PHBV20 (a) and PHBV20/2RS (b) during accelerated weathering process.

Figure 4

Optical microscopy pictures of PHBV and its plasticized composite samples before and after 3 month biodegradation.

Figure 4

Optical microscopy pictures of PHBV and its plasticized composite samples before and after 3 month biodegradation.

Figure 4

Optical microscopy pictures of PHBV and its plasticized composite samples before and after 3 month biodegradation.

Figure 5

Mass loss during degradation of PHBV and its plasticized composites.