Study On Preparation And Properties Of Polyethylene/Montmorillonite Nanocomposite

Using maleic anhydride grafted polyethylene (PEMA) as compatilizer, nanocomposites based on high-density polyethylene (HDPE) and organic–montmorillonite (MMT) were prepared by melt intercalation. X-ray diffractometry ( XRD ) and transmission electron microscopy(TEM)were used to investigate the intercalation behavior and microstructure of composites. The intercalation effect of MMT in polymer and the factors affecting the effect were discussed. Mechanical properties, thermal properties, crystallization properties and barrier properties on gas and organic solvent were also studied. As examinating the affection on strength of polymer by the intercalation effect and the content of compatilizer, it was found that the tensile strength of PE could be enhanced by increasing the content of MMT. The maximum value in tensile strength (34.79MPa) was achieved when the concentration of MMT was 3wt %, and increased by nearly 13.5% compared to the unfilled PE. The tensile strength initially increased and then decreased with increasing contents of PEMA. However, the elongation decreased . The thermal degradation behaviour was studied by thermogravimetry analyser (TGA). The results of TGA showed that the Tmax of PE/MMT was 5℃higher than that of PE. And at the same time, the degradation velocity was slower than unfilled PE. That is to say the thermal properties of PE were improved by introduction of MMT. The barrier properties upon gas and organic solvent were also studied. Compared with those of PE, the permeability value of gas in composites decreased 15% nearly and the permeability coefficient was smaller. By means of permeability measurement the barrier properties upon organic solvent were improved significantly. At last, the isothermal and non-isothermal crystallization kinetics of composites were studied by means of differential scanning calorimetry (DSC). It was found that nuclearion mechanism and dimension of spherulite growth of the nanocomposite were different from those of PE to some extent by calculating the Avrami exponent(n). It showed clearly that MMT had a heterogeneous nucleation effect on crystallization of PE. The crystallization rate of composites was faster than that of PE at the same condition. Moreover, the methods proposed by Arrhenius and Kissinger were used to evaluate the activation energy of the mentioned samples in isothermal and non-isothermal crystallization, respectively. The apparent activation energy of composites was higher than that of PE.