4.2 Result of characterization
4.2.1 Fourier Transform Infra-Red (FT-IR)
FT-IR spectroscopy is performs on clay samples before and after it is being modified by using octadecylamine and 3-aminopropyltrimethoxysilane in order to evaluate the cationic exchange reaction and silylation reaction and ascertain the presence of organic moieties on the clay surfaces after surface functionalization. After absorption of IR radiation, the molecules of a chemical substance vibrates will giving rise to close packed absorption bands called IR absorption spectrum which will correspond to the characteristic functional group and bands present in a chemical substance in modified clays. For cationic process, FT-IR have all the typical bands of the amine and of the clay , mainly N-H and C-H band at the peaks around of 3240 and 2920 cm- respectively meanwhile for silylation process, there will be a peak around 3626 cm- correspond to the hydroxyl stretching vibration of the structural –OH group bonded to silicon.The infrared spectroscopic study in a polymer nanocomposite shows that the FT-IR spectra of Si-O stretching vibrations are sensitive to the extent of nanoclay dispersion at the molecular level.
4.2.2 Thermal Gravimetric analysis (TGA)
TGA curves of Na+-MMT and organoclays could be distinguished with specific characteristics. When the nanocomposite with 1% OMMT content is analysed by the TGA, the onset of the degradation temperature is higher than neat LDPE/MMT nanocomposite. Arupt et al., 2007 stated that the dispersion of modified clay generally retards thermal degradation of the polymer by inducing significant polymer-clay interaction. The thermal decomposition temperatures (Td) at a 50 wt.% weight loss from the thermogravimetry will reveal that the organoclays will increase the thermal stability of the nanocomposites.
4.2.3 X-ray Diffraction (XRD)
XRD analysis was used to identify nanocomposite structures with the calculation of the basal reflections of the separated silicate layers by monitoring the position, shape and intensity of these reflections. XRD analysis of Na+ -MMT, octadecylamine-MMT (ODA-MMT), silated-MMT and silated-ODA-MMT show that there is an increase in interlayer spacing. The modified MMTs show the maximum peaks and shift towards smaller angles relative to the unmodified Na+-MMT. Their maximum d-spacing also larger than pristine Na+-MMT. This indicate that insertion of modifying agent molecules into the layers of Na+-MMT galleries affected the d-spacing by the different molecular arrangements of the modifying agent molecules between the clay platelets. The increased basal spacing shows that the improvement of physical and chemical properties.
4.2.4 Tensile test
Tensile tests will be applied to observe the strength of the LDPE nanocomposites. During the tensile testing, deformation occurs at the central region of the sample, which contains a uniform cross-sectional area along its length. The difference in mechanical properties could be attributed to the dispersion of the fillers, because the presence of agglomerated particles would act as stress concentrators.
4.2.5 Impact test
The blend of LDPE/OMMT nanocomposites possess optimal mechanical properties, enough impact strength and flexibility. The nanofiller layers make the fracture delay due to the damping of the stress. But as the addition of nanofiller concentration up to 3 wt%, the impact strength become lessen. It is due to the limited of motion of the polymer chain.