Fibers and Polymers 2013, Vol.14, No.4, 550-555 550 Preparation of Hybrid AHO-POSS/Polypropylene Nanocomposite Monofilaments by Radiation Induced Grafting Sachin Kumar, B. S. Butola 1 * , and M. Joshi 1 Guru Nanak Dev University, Amritsar, Punjab, India 1 Department of Textile Technology, IIT Delhi, Hauz Khas, New Delhi-110016, India (Received February 18, 2012; Revised May 31, 2012; Accepted June 3, 2012) Abstract: The Allyl-heptaisobutyl-polyhedral Oligomeric Silsesquioxane (AHO-POSS) grafted polypropylene (PP) nanocomposite monofilaments were prepared by γ-ray irradiation induced grafting. The structure and properties of physically blended and γ-ray irradiated AHO-POSS/PP nanocomposite filaments were investigated by FTIR, wide-angle X-ray diffraction (WAXD), Thermo-gravimetric Analysis and mechanical property studies. Chemical bonding of AHO-POSS with PP after γ-ray irradiation was confirmed by FT-IR spectroscopy. Grafting resulted in change in mechanical and thermal properties and the extent of change was critically dependent on loading of AHO-POSS in PP and radiation dose level. In general, tensile strength decreased almost continuously with increase in radiation dose whereas thermal stability increased upto a radiation dose of 5 kGy and then decreased. The loss in tensile strength was caused due to chain scission, cross linking and loss in orientation. Keywords: Nanocomposites, Allyl-heptaisobutyl-polyhedral oligomeric silsesquioxane, Radiation induced grafting, Chain scission, Cross-linking Introduction Polymer composites have traditionally been used in a diverse range of applications which require combination of two seemingly opposite properties i.e., flexibility and strength/rigidity. Recently, however, a lot of interest has been generated in the development of polymeric nanocomposites, where the filler phase is required to have at least one of its three dimensions in nanometer range (<100 nm). Typically, these fillers include nanoparticles, nanotubes/nanofibres and nanoclays which have either all, two or one of their dimensions respectively in nanometer range [1,2]. Polyhedral oligomeric silsesquioxanes (POSS), fall in the category of nanoparticles and belong to the family of silsesquioxanes, characterized by the general formula (RSiO 1.5 ) n where R is hydrogen or any organic group and n is an integer. POSS molecules are essentially a Silica core covered by organic groups sheath, making it a hybrid nanoparticle. POSS are versatile materials and lend themselves to functionalization by suitable alteration in R, which creates a possibility of copolymerization or grafting with a large range of monomers or polymers. A large amount of literature has been published [2] about POSS based polymeric nanocomposites. Though POSS molecules come in various shapes and sizes, cage shaped POSS molecules have been preferred for they combine the properties of rigid silica ceramic core with the compatibility of an organic sheath with different polymers [3,4]. POSS can be incorporated into polymer systems through melt/solution blending, grafting or copolymerization. Incorporation of POSS into polymers has been reported to improve thermal stability, oxidation resistance, mechanical properties and reduce flammability, heat evolution and processing viscosity [5]. Aggregation is a serious problem in POSS/polymer nano- composites during melt mixing. The aggregation results in failure of the transfer of the nanofiller properties to the resulting nanocomposites. Radiation-induced grafting has generally been known to simplify the whole process, reduce the cost of production and being largely a pollution free method. The process provides a simple route to create active sites on target polymer in rapid and uniform manner. The reaction can be carried in different polymeric forms like solid, solution, in a wide range of temperatures and avoids the use of initiators/catalysts [6]. In this paper, an attempt has been made to prepare Allyl-Heptaisobutyl-Polyhedral Oligomeric Silsesquioxane/Polypropylene (AHO-POSS/PP) nanocomposites by grafting of POSS unit into the PP backbone through in situ radiation-induced grafting reaction. AHO-POSS (Figure 1) is a reactive macromer with an allyl group which is capable of reacting with PP under suitable conditions. Nanocomposite monofilaments have been prepared *Corresponding author: bsbutola@textile.iitd.ernet.in DOI 10.1007/s12221-013-0550-4 Figure 1. Molecular structure of 1-Allyl-3,5,7,9,11,13,15-heptaisobutyl- POSS(AHO-POSS).