Changes in Mechanical Properties of Polyhydroxyalkanoate with Double Silanized Cellulose Nanocrystals Using Different Organosiloxanes

Abstract

Polyhydroxyalkanoate (PHA) is a biodegradable plastic with great potential for tackling plastic waste and marine pollution issues, but its commercial applications have been limited due to its poor processability. In this study, surface-modified cellulose nanocrystals were used to improve the mechanical properties of PHA composites produced via a melt-extrusion process. Double silanization was conducted to obtain hydrophobically treated CNC-based fillers, using tetraethyl orthosilicate (TEOS) and methyltrimethoxysilane (MTMS). The morphology, particle size distributions, and surface characteristics of the silanized CNCs and their compatibility with a PHA polymer matrix differed by the organosiloxane treatment and drying method. It was confirmed that the double silanized CNCs had hydrophobic surface characteristics and narrow particle size distributions, and thereby showed excellent dispersibility in a PHA matrix. Adding hydrophobically treated CNCs to form a PHA composite, the elongation at break of the PHA composites was improved up to 301%, with little reduction of Young’s modulus, compared to pure PHA. Seemingly, the double silanized CNCs added played a similar role to a nucleation agent in the PHA composite. It is expected that such high ductility can improve the mechanical properties of PHA composites, making them more suitable for commercial applications.

Expanding Poly(lactic acid) (PLA) and Polyhydroxyalkanoates (PHAs) Applications: A Review on Modifications and Effects

“…Furthermore, they are also incorporated to modify the crystallization behavior, rate of degradation as well as the morphology. PHA-based nanocomposites have been fabricated using Cloisite 25A [ 202 ], carbon nanotubes (CNTs) [ 203 , 204 ], organ modified montmorillonite (OMMT) [ 205 , 206 , 207 ], multi Na-montmorillonite Cloisite Na (Na-MMT), a methyl tallow bis-hydroxyethyl quaternary ammonium-modified MMT Cloisite 30B [ 208 , 209 , 210 ], cellulose nanowhiskers (CNWs) [ 211 , 212 , 213 ], SiO 2 nanofibers [ 214 ], carbon nanofibers (CFs) [ 215 ], halloysite nanotube (HNT) [ 209 ] and CNCs [ 103 , 105 , 106 , 107 , 216 ].…”

“…Recently, Jo et al [ 216 ] have successfully improved the mechanical properties of PHA based composites through the addition of surface-modified CNCs via melt-extrusion. To obtain hydrophobically treated CNCs, double silanization using tetraethyl orthosilicate (TEOS) and methyltrimethoxysilane (MTMS) was conducted.…”

“…The addition of double silanized CNCs acted as a nucleating agent and improved the elongation at break up to 301% with a minor drop in the tensile modulus. The produced composites are likely appropriate for future utilization in commercial applications demanding high ductility [ 216 ].…”

Poly(3-hydroxybutyrate) Nanocomposites with Cellulose Nanocrystals

“…Different methods were applied to improve the compatibility between the strongly hydrophilic CNCs and the hydrophobic PHB matrix [ 108 , 109 , 110 , 111 ]. Dispersion agents and compatibilizers are one of the simplest and sometimes efficient additives for improving the compatibility in polymer nanocomposites with CNCs [ 112 ].…”

“…A mixture of PHB and poly(4-hydroxybutyrate), denoted as PHB/P4HB, was reinforced with surface hydrophobized CNCs, which were obtained by a double silanization process, as shown in Figure 3 [ 111 ].…”