Grafting of Bacterial Polyhydroxybutyrate (PHB) onto
Cellulose via In Situ Reactive Extrusion with Dicumyl Peroxide
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Abstract
Polyhydroxybutyrate (PHB) was grafted
onto cellulose fiber by dicumyl
peroxide (DCP) radical initiation via in situ reactive extrusion.
The yield of the grafted (cellulose-<i>g</i>-PHB) copolymer
was recorded and grafting efficiency was found to be dependent on
the reaction time and DCP concentration. The grafting mechanism was
investigated by electron spin resonance (ESR) analysis and showed
the presence of radicals produced by DCP radical initiation. The grafted
copolymer structure was determined by nuclear magnetic resonance (NMR)
spectroscopy. Scanning electronic microscopy (SEM) showed that the
cellulose-<i>g</i>-PHB copolymer formed a continuous phase
between the surfaces of cellulose and PHB as compared to cellulose-PHB
blends. The relative crystallinity of cellulose and PHB were quantified
from Fourier transform infrared (FTIR) spectra and X-ray diffraction
(XRD) results, while the absolute degree of crystallinity was evaluated
by differential scanning calorimetry (DSC). The reduction of crystallinity
indicated the grafting reaction occurred not just in the amorphous
region but also slightly in crystalline regions of both cellulose
and PHB. The smaller crystal sizes suggested the brittleness of PHB
was decreased. Thermogravimetric analysis (TGA) showed that the grafted
copolymer was stabilized relative to PHB. By varying the reaction
parameters the compositions (%PHB and %cellulose) of resultant cellulose-<i>g</i>-PHB copolymer are expected to be manipulated to obtain
tunable properties