Properties of Differently Compatibilized Bamboo Fiber Reinforced PE Composites - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 110

melt-grafting experiment, LLDPE granular polymer was first melted by dosing into
the Haake chamber and then bamboo-fibers were added to this molten polymer. The
powdered MA and DCP as a radical initiator were dosed after 5 min via a hopper into
a Haake Rheomix 600 (equipped with a pair of high shear rollers). The melt grafting
reaction was done for i-GMA (30 min) and for i-MA (15 min) at melting temperature
of 170°C and 50 rpm speed. The grafting reaction mechanism of GMA onto PE in melt
phase process when DCP was used as an initiator was discussed earlier (Jang et al.,
2001). No special precautions were taken to exclude air from the rheomixing chamber.
The mixing torque and melt temperatures were monitored on-line and recorded for all
the samples. The ejected products before making composite sheets were heated for 30
min to remove the unreacted MA/GMA in an oven at 190°C. The composite sheets
(having average thickness of 3 mm) were prepared by controlled press molding at
200°C and 6 ton pressure for 15 min. The sheets were cooled around for 15 min under
pressure with water circulatory system and after removing from mold, cut for further
testing.

determination of Grafting degree
Maleic anhydride (MA)
The grafting degree (GD) of MA was determined by the back-titration method includ-
ing the dissolution of a small amount of composite sample (1.0 g) in 100 ml of boiling
xylene in a conical flask and a few drops of water was added to hydrolyze all anhy-
dride functionability. Then, 10 ml ethanol solution of NaOH (0.1 mol/l) was added
and mixed gently by stirrer. After refluxing for 30 min under stirring, this solution was
back-titrated with HCl (0.1 mol/l) using methyl red as the indicator. The GD MA was
defined (Nakason et al., 2004; Qi et al., 2004; Shi et al., 2001) as the amount of grafted
MA as a percentage of LLDPE- g -MAH and is calculated by equation given below:

(V -V )×C×M

0g

GD (%)= ×100

MA

2W ×1000

S

where, V 0 is the amount of HCl consumed by using LLDPE as reference (ml),
V g is the amount of HCl consumed by the grafted LLDPE (ml),
C is the molar concentration of HCl (mol/l),
M (98) is the molecular weight of maleic anhydride,
W s is the weight of sample (g).
Glycidyl methacrylate (GMA)
After melt grafting of GMA onto LLDPE the weight was recorded, the grafted LL-
DPE were extracted with acetone by means of a Soxhlet extractor for 48 hr to remove
residual GMA and possible homopolymer that is poly-GMA. To evaluate the degree
of grafting (GD) of GMA, the left over products, pure graft copolymers, were dried in
vacuum at 60°C and weighed. The GD GMA was calculated by the following equations
(Chen et al., 1996; Jang et al., 2001; Kim et al., 2001):