Properties of Differently Compatibilized Bamboo Fiber Reinforced PE Composites - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 108

Chapter 10
Properties of differently Compatibilized Bamboo
Fiber reinforced Pe Composites
Sandeep Kumar
iNtroduCtioN
Process of “grafting” is a very useful method for making branches or chemical modifi-
cation in polymeric materials. Natural fiber reinforced thermoplastic composites graft-
ing, in context of compatabilizer, can be done by two ways: one is pre-grafting (the
polymer is first taken and grafted as compatabilizer) and another is ---- in situ grafting.
In ----in situ grafting process, polymer is grafted during the fabrication of composites/
blends. The later kind of compatibilization is also called reactive compatibilization.
Polyolefins are commonly functionalized with maleic anhydride (MA) to enhance ad-
hesion to polar materials and are used as a compatibilizer. The bamboo-fiber is often
brittle compared to other natural fibers, because the fibers are covered with lignin and
it undergoes degradation above 200°C (Seema and Kumar, 1994). Polyethylene (PE)
and polypropylene (PP) are among the commonly used thermoplastics for the prepara-
tion of natural fiber reinforced composites due to their relatively low prices and good
processability (Deshpande et al., 2000; Kim et al., 2006).
The synthesis of polyolefin graft copolymers by melt processing was reviewed and
interdependent factors (include, mixing efficiency, temperature, pressure, residence
time, venting, polyolefins, monomer(s), initiator(s), and screw/extruder design) are
to be optimized so as to maximize the degree of grafting (DG) and minimize the
side reactions (Moad, 1999). Various coupling agents or compatibilizers have been
reported in the literatures to improve the interface between the thermoplastic matrix
and natural fibers. Among them, maleic anhydride-grafted PE or PP is the most com-
monly available compatabilized matrix because of their ability to effectively enhance
the mechanical properties of the composites (Liu et al., 2008). The solution surface
grafting of MA onto PP in toluene solvent by using benzoyl peroxide as an initiator in
nitrogen atmosphere to remove dissolved oxygen has been done to prepare bamboo-fi-
ber PP composites. These composites revealed improved mechanical properties when
compared with commercially available wood pulp composite (Chen et al., 1998). Lit-
erature reported the free radical melt grafting of glycidyl methacrylate onto a range of
PP grade in a Haake Rheomix 600 batch mixer and then grafted product was purified
with toluene and acetone (Chen et al., 1996). The grafted structures of MA onto PE
have been investigated (Heinen et al., 1996). Reduction in melting temperature and
crystallization percentage or increase in crystallization peak temperature was observed
to be an effect of MA grafted onto PE (Martínez et al., 2004). The mechanism of
cross-linking or grafting by melt blending technique has been discussed by researchers
(Gaylor et al., 1989; Heinen et al., 1996; Shi et al., 2001).