Abstract
Poly(3-hydroxybutyrate) (PHB) was compounded with three different Bentonite clays: natural, purified by ultrasound/sonicated and organically modified with hexadecyltrimethylammonium bromide. PHB/Bentonite masterbatches with 30% clay were prepared in a laboratory internal mixer and letdown with pure matrix to 1% and 3% w/w clay. Test samples were injection molded and characterized by x-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Increase in Bentonite hydrophobic character was evinced by FTIR for organoclays. XRD of composites showed increase in clay interlayer distance and peak broadening, suggesting formation of intercalated nanocomposites. DSC showed increase in crystallinity and crystallization rate for compounds, especially for PHB/organoclay formulations. Thermal aging was conducted by exposing specimens at 115oC for up to 120 hours, and mechanical properties were measured according to ASTM standards. Elastic modulus increased and impact strength decreased with time and clay content; clay purification had little effect on the tensile properties. Tensile strength of thermal aged samples showed little variation, except for the organoclay nanocomposites, for which it significantly decreased with exposure time. SEM images displayed a whitened honeycomb structure and detachment of PHB/Bentonite layers which may be connected to cold crystallization and degradation processes taking place during thermal aging.Keywords:
Highlights
Nowadays there is a growing interest in developing bio-based polymers and innovative process technologies that can reduce the dependence on fossil fuel and move to a sustainable materials basis
The compounds were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electronic microscopy (SEM)
The intensity of these peaks decreased with clay purification and with clay purification and organophilization, indicating that the chemical modification reduced the clay hydrophilic character
Summary
Nowadays there is a growing interest in developing bio-based polymers and innovative process technologies that can reduce the dependence on fossil fuel and move to a sustainable materials basis. Bio-nanocomposites open an opportunity for new, high performance, light weight green nanocomposite materials to replace conventional non-biodegradable petroleum-based plastic materials.[1,2,3,4]. Polyhydroxyalcanoates, made from natural resources by low-impact biotechnological processes, are among the biodegradable polymers being widely investigated as alternative materials. Recent studies focus on PHB, poly(3hydroxy butyrate), a semi-crystalline polyester obtained by bacterial action upon sugars, with properties similar to many synthetic commodity polymers and processed by standard industrial methods. PHB is biocompatible, fully compostable, and quickly degrades under normal landfill conditions to water and carbon dioxide.[3,5,6,7]
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