Abstract
Fiber–matrix interfacial adhesion is one of the key factors governing the final properties of natural fiber-based polymer composites. In this work, four extrusion reactive agents were tested as potential compatibilizers in polyhydroxylbutyrate (PHB)/cellulose composites: dicumyl peroxide (DCP), hexamethylene diisocyanate (HMDI), resorcinol diglycidyl ether (RDGE), and triglycidyl isocyanurate (TGIC). The influence of the fibers and the different reactive agents on the mechanical properties, physical aging, and crystallization behavior were assessed. To evaluate the compatibilization effectiveness of each reactive agent, highly purified commercial cellulose fibers (TC90) were used as reference filler. Then, the influence of fiber purity on the compatibilization effect of the reactive agent HMDI was evaluated using untreated (U_RH) and chemically purified (T_RH) rice husk fibers, comparing the results with the ones using TC90 fibers. The results show that reactive agents interact with the polymer matrix at different levels, but all compositions showed a drastic embrittlement due to the aging of PHB. No clear compatibilization effect was found using DCP, RDGE, or TGIC reactive agents. On the other hand, the fiber–polymer interfacial adhesion was enhanced with HMDI. The purity of the fiber played an important role in the effectiveness of HMDI as a compatibilizer, since composites with highly purified fibers showed the greatest improvements in tensile strength and the most favorable morphology. None of the reactive agents negatively affected the compostability of PHB. Finally, thermoformed trays with good mold reproducibility were successfully obtained for PHB/T_RH/HMDI composition.
Highlights
The development of biobased biodegradable thermoplastic materials is a topic research of special interest because it can represent a cost-effective and environmental-friendly alternative to commodities [1]
The morphology of PHB/TC90, PHB/unpurified rice husk fiber (U_RH), and PHB/treated rice husk fiber (T_RH) composites with and without reactive agents was examined by scanning electron microscopy (SEM), using a high-resolution field-emission microscope (JEOL 7001F, Tokyo, Japan)
In order to assess the role of the reactive agents, blends with TC90 were prepared as detailed in the experimental section
Summary
The development of biobased biodegradable thermoplastic materials is a topic research of special interest because it can represent a cost-effective and environmental-friendly alternative to commodities [1]. The applicability fields where the PHB-based material results are more interesting are those in which biodegradability is desired either because composting could be a viable option for their waste management or because they can potentially end up in the environment. Among those applications, we can highlight food packaging or disposable products such as single-use tableware, hygiene-related single-use products, straws, etc. PHB presents mechanical properties in terms of a stiffness and strength that is similar to PP, good barrier properties, which are comparable or even superior to PET [6,7,8,9,10], and it is biodegradable in different environments, such as soil and marine [7,11,12], and compostable at lab-scale, industrial, and home composting conditions [13]
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