Melt mixed compatibilized polypropylene/clay nanocomposites: Part 1 – the effect of compatibilizers on optical transmittance and mechanical properties

Polypropylene (PP)/clay nanocomposites were prepared via a melt mixing technique. Two types of compatibilizers, polyolefin elastomer grafted maleic anhydride (POE-g-MA), and polypropylene grafted maleic anhydride (PP-g-MA) were incorporated to improve the dispersion of commercial organoclay (20A). With the introduction of PP-g-MA, the optical transmittance of the nanocomposites displayed higher transmittance than those of the POE-g-MA compatibilized case. However, POE-g-MA greatly increased the interlayer spacing of the clay compared with PP-g-MA. This interesting observation is pertinent to the complex morphology of compatibilized nanocomposites. The PP-g-MA compatibilized system conferred higher tensile strength, Young’s modulus, and cutting strength than the POE-g-MA compatibilized case. The high cutting strength of the PP/clay nanocomposites, with or without compatibilizers, signified the importance of crystalline yielding even in the nano-fracture zone of deformation. This finding has not been published in the literature of this field. Clay and its dispersion effect that conventionally claimed to enhance the tensile properties were rather insignificant under this condition of confined deformation of the cutting design. The current results suggest that a high extent of exfoliation may not guarantee high transparency or strength for nanocomposites. The matrix properties and interphase whose variations were caused by the additional compatibilizers to aid the clay dispersion were also crucial factors to the derived properties.