PHB/Bentonite Compounds. Effect of Clay Modification and Thermal Aging on Properties

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.

Characterization of Optimized Ternary PLA/PHB/Organoclay Composites Processed through Fused Filament Fabrication and Injection Molding

“…An increase in the percentage of crystallinity of PHB-J is noted when it is processed by additive manufacturing. This result can be attributed to the scission of the macromolecules chains caused by the degradation of PHB-J [46]. Tg = 30 °C The addition of OMLS allows a single melting peak at 146 • C to be obtained, which confirms the compatibilization effect of nanoclay.…”

“…An increase in the percentage of crystallinity of PHB-J is noted when it is processed by additive manufacturing. This result can be attributed to the scission of the macromolecules chains caused by the degradation of PHB-J [46].…”

Effects of thermoplastic poly(ether-ester) elastomer and bentonite on properties of recycled poly(ethylene terephthalate)

“…24,30,33,34 The TEM images (Figure 3(b)−(d)) of these nanocomposites confirmed the agglomerated or tactoid structure of bentonite (the darker area), which seemed to become denser with increasing bentonite loading and thus played only a slight role on property improvement. 35

Figure 2.XRD patterns of R-PET, R-PET/TPEE blend, bentonite and R-PET/TPEE blend nanocomposites with 1, 2, 3, and 5 phr bentonite.

Figure 3.Representative TEM images of R-PET/TPEE blend nanocomposites with bentonite at (a) 1 phr, (b) 2 phr, (c) 3 phr and (d) 5 phr.

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“…24,30,33,34 The TEM images (Figure 3(b)À(d)) of these nanocomposites confirmed the agglomerated or tactoid structure of bentonite (the darker area), which seemed to become denser with increasing bentonite loading and thus played only a slight role on property improvement. 35 The mechanical properties of the resulting nanocomposites are also listed in Table 1. Among the four different nanocomposites, the one with 1 phr bentonite exhibited the highest impact and tensile strength, showing a significant improvement in these properties (1.3-fold and 1.7-fold, respectively) compared with those of the neat 70/30 (wt%/wt%) R-PET/TPEE blend.…”

Effect of organoclay and corn straw on the properties of polycaprolactone composite films

“…PCL is well known for its excellent properties (high flexibility, impact and tearing resistance) (Reul et al, 2018;Sousa et al;Silva et al, 2022). Organoclay composites are reported to improve and preserve these characteristics (Santos et al, 2019;Almeida et al, 2017;Falcão et al, 2019). The data therefore indicate that the compounds under study have efficient barrier properties for possible applications in food packaging and protective coatings, among other applications.…”