Preparation of zinc and calcium hydroxide-modified fly ash and its utilization as filler in nylon 6

In this article, an attempt is made to improve the filler-loading capacity of fly ash (FA) by its surface modification with zinc hydroxide and calcium hydroxide. In the modification reaction, FA to calcium hydroxide weight ratio was maintained constant at 5:1, while that of FA to zinc hydroxide was varied as 5:0.4, 5:0.6, and 5:0.8 and the optimized composition was utilized as filler in nylon 6. Modified FA was found to have formed hemimorphite on to its surface, giving rise to spine-structured surface morphology. FA surface modified with 5:0.6 weight ratio of FA to zinc hydroxide (FaZn6Ca) provided FA with the highest level of spine-structured surface morphology and thus was determined to the optimized composition to be utilized as filler in nylon 6. Concentration of FaZn6Ca was varied up to 40 phr in nylon 6. Prepared composites were characterized for mechanical, thermal, rheological, crystallinity, and morphological properties. Melting and crystallization temperatures remained approximately constant; tensile strength, flexural strength, crystallinity, tensile modulus, flexural modulus, enthalpy of melting (Hm), and enthalpy of crystallization increased, whereas elongation at break and impact strength decreased with increase in FaZn6Ca concentration in nylon 6. Spine-structured surface morphology formed on the surface of FA increased the filler-loading capacity of FaZn6Ca in nylon 6; while the improvement in the properties were caused due to better interactions happening between nylon 6 and FaZn6Ca due to the hydrophilic nature of both the materials. Since FA is obtained as waste from thermal power plant, the use of this material as a filler in nylon 6 would help ease the solid waste disposal problem which will benefit the environment.