Silane functionalization of sodium montmorillonite and halloysite (HNT) nanoclays by 'grafting to' method to improve physico-mechanical and barrier properties of LLDPE/clay nanocomposites

Clay-reinforced polymer composites have been considered as highly demand nano-composites since several decades. To be utilized as packaging materials, these nano-composites should possess good impermeability to oxygen and water vapor. The major compatibility issue of the hydrophilic inorganic nanofillers with hydrophobic thermoplastics has been overcome in this work by using the 'grafting to' silylation method of two different nanoclays, namely montmorillonite Na+ and halloysite (HNT) nanoclays, at 85 degrees C. Organosilanes: 3-aminopropyltriethoxysilane (3-APTES) and vinyltrimethoxysilane (VTMS) were used to functionalize these nanoclays to improve interfacial bonding with linear low-density polyethylene (LLDPE) polymer chains. TGA analysis resulted in higher amount of grafting yield percentages for silane-treated MMT nanoclays (28.9% for MMT-APTES and 24.3% for MMTVTMS) which are much higher than silane-functionalized HNT nanoclays. The amount of 1, 3 and 5 wt% of each organoclay was melt and mixed with LLDPE to enhance the overall performance properties of the resultant nanocomposites. The maximum tensile strength exhibited by the nanocomposite is around 20.6 MPa for 3 wt% of MMT-APTES concentration. Also, Young modulus improves up to 56% compared to neat LLDPE on the addition of 5 wt% of silane-treated organoclay. The microscopic analysis, especially TEM, provided information about the better dispersion of anisotropic fillers inside the thermoplastic matrix. Moreover, such filler compatibilization also showed 29.4% reduction in oxygen transmission rate (OTR) and 63.5% reduction in water vapor transmission rate (WVTR) value of composite materials with only 5 wt% of nanoclay loading along with improved rheological and ultraviolet (UV) barrier properties of these nanocomposites. The prepared nanocomposites with improved barrier properties could be ideal alternatives for flexible thermoplastic composites as packaging materials. [GRAPHICS] .