2. Experimental
2.1. Materials
Polyhydroxybutyrate-co-valerate (PHBV) was obtained from
Biomer, Germany with the trade name Biopol (Zeneca Bio Products).
Micro sized talc was supplied by Luzenac America with the
trade name of Jetfill 700C. The particulate dimensions of the talc
range from 2 to 10 lm. Wood fibers used were the maple wood fiber
from the American Wood fiber Schofield, WI with the trade
name 2010 MAPLE.
2.2. Fabrication of composites
Hybrid bio-composite specimens were fabricated using microcompounder
(manufactured and designed by DSM Research, Netherlands
with a barrel volume of 15 cc) and a mini injection molder.
It was equipped with co-rotating twin-screws of the length
150 mm and L/D (length to diameter ratio) 18 and has three consecutive
heating zones. The wood fiber and PHBV were dried at a
110 C and 80 C under vacuum for 2 and 4 h respectively, to devoid
of any moisture during the processing. The hybrid composite
fabrication was carried out in two step process and that of the
PHBV and wood fiber composite in a single step. The different compositions
and processing parameters used during composite fabrication
are listed in Table 1. For the hybrid composite, PHBV pellets
and wood fiber in fixed compositions as listed in Table 1 were
physically mixed and fed to the micro-extruder. PHBV pellets
and wood fibers were allowed to melt mix in the extruder for
4 min. and latter talc (as per the composition) was added to the
melt mix of PHBV and wood fiber. Finally, all the three components
were mixed for another 4 min in the micro-extruder for an appropriate
dispersion of the talc and wood fibers in the melt. The processing
temperatures of the three consecutive zones were 165, 160
and 155 C. The melt from the extruder was collected in a pre
heated mini injection (at a temperature of 155 C), and this was
transferred to molding machine for specimen fabrication. The optimized
injection pressure of 551.5 kPa was used to extricate the
melt from the injection cylinder to the mold located in the molding