3. Result and Discussion
3.1 Melt Flow Index
The melt flow index is one of the most common parameters specified when describing a polymer. It is
convenient method for expressing important flow characteristics of polymer, which clarifies the way in which the
polymer can be processed.
As observed from Table 1that the MFI value increases as the foam percentage increases up to 6% after
which MFI value decreases. As observed the maximum value of melt flow index is obtained at 6% of foam mixed
with LLDPE. High melt flow index at 6% indicates ease of melting and easy to process. But, the material with this
behavior would have shorter chains and therefore low molecular weight and lower viscosity.
As the foam % is increased further from 6% to 8% (or) 10% the MFI value decreases as shown in Fig 2.
The decrease in MFI value increases the molecular weight. This intern may affect some of the key physical and
mechanical properties of the polymer such as tensile strength, creep resistance and liquid temperature etc. The
reason is primarily due to intermolecular interactions. The two most common of these interactions are entanglement
and secondary bonding. Entanglement is simply the mutual wrapping of polymer chains around each other. Higher
molecular weight implies longer polymer chain and longer polymer chain implies more entanglement. When the
polymers are highly entangled, they resist sliding over each other. More additional energy must be put in to system
to cause the molecules to move relative to each other. The additional energy is seen as a higher softening
temperature and higher mechanical property. Secondary bonding has much the same effect as entanglement of the
polymer. The underlying purpose of determining melt index is to estimate the ease of melting of polymer. Therefore,
attention of moulder lie on selecting optimum value of MFI which leads to optimum mechanical property and
processability. When the foam percentage is increased beyond 6% (or) below 6% the processability is greatly