Properties of Differently Compatibilized Bamboo Fiber Reinforced PE Composites - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 109

Most of the grafting reaction studies have been carried out using different grafting
recipes (type and amount of peroxide and MA content) and different processing condi-
tions (type of reactor, screw speed and temperature) (Machado et al., 2001; Qi et al.,
2004; Sclavons et al., 2000; Shi et al., 2001) for the polymer blend system. Consider-
able efforts have been made in producing newly polymeric composite materials with
an improved performance/costs balance. This can be achieved by using a direct graft-
ing of MA/GMA instead of pre-grafting of MA/GMA onto existing polymers in the
process of fabrication of natural fiber composites. From a research and development
point of view, the direct grafting routes of monomer (MA/GMA) are usually more ef-
ficient and less expensive.
The objective of this research is to compare the thermal and tensile properties of
----in situ (i-) grafted polymer compatibilized composites with pre (p-) grafted poly-
mer compatibilized composites. In turn, this research gives an idea of advantages and
disadvantages of both the process in terms of the manufacturing methods employed to
fabricate the composites.
materials aNd methods
Linear low density polyethylene (LLDPE) (G-Lene) (MFI 0.9, ρ 0.92g/cm 3 ) was ob-
tained from GAIL (India) Limited. The LLDPE-g-maleic anhydride (TP-568/E) (MFI
2-3@190°C-2.16Kg, MAH content (%) 0.4-0.6 and ρ 0.923 g/ml) was obtained from
Pluss Polymers (P) Limited (India). Glycidyl methacrylate (GMA) (ρ 1.450 g/ml,
bp142°C, Aldrich) and MA (mp 52-55°C, Aldrich) was used for ----in situ grafting.
The MA or GMA was chosen for ----in situ melt grafting because it has been report-
ed that the anhydride or methacrylate groups strongly associates with the hydroxyl
groups (Chen et al., 1996; Chen et al., 1998). The present research was carried out by
using bamboo species- Ochlandra travancorica (one year old)-grown in India. The
process of delignification of bamboo to produce deglinified bamboo fiber and their
physical properties has been reported by earlier research work (Kumar et al., 2010).
Composite Preparation with i-/p-grafted Polymer
Short delignified bamboo-fiber (SDBF) having an average length of 1-2 mm were
pre-dried for processing in an oven at 110°C for 8 hr to expel moisture. In order to
distinguish the properties of differently compatibilized composites, the ratio of ma-
trix to fiber was kept constant in all the formulations that is, 30% w/w fiber content
depending on the optimized properties of fiber reinforced composites at this fiber
weight fraction (Kumar et al., 2010). To compare the properties with ----in situ grafted
polymer as a compatibilizer, MA-g-LLDPE content have therefore converted into MA
content. The LLDPE was replaced by pre-grafted polymer (LLDPE-g-MA having MA
content 0.75-5%) and the effect of MA content in graft copolymer on the properties
was investigated. ----in situ grafted composites were prepared by melt grafting of 1%,
3%, and 5% (w/w) GMA or MA onto LLDPE with 1% dicumyl peroxide (DCP) as an
initiator and SDBF. The low level of DCP was chosen as it gives best result for graft-
ing reaction of MA/GMA (Ho et al., 1993; Jang et al., 2001). It was considered that the
excess of initiator results in a greater extent of degradation/side reactions. In a typical