*e-mail: ckd@matsc.iitkgp.ernet.in 1598-5032/12/506-05 ©2003 Polymer Society of Korea 506 Macromolecular Research, Vol. 11, No. 6, pp 506-510 (2003) Nanofiller as Crosslinker for Halogen-Containing Elastomers N. G. Sahoo, E. Shiva Kumar, and C. K. Das* Materials Science Centre IIT, Kharagpur, 721302 A. B. Panda and P. Pramanik Department of Chemistry IIT, Kharagpur, 721302 Received May 30, 2003; Revised Oct. 24, 2003 Abstract: A Zn ion-coated nanosilica filler has been developed and tested, in chlorosulfonated polyethylene (CSPE) and polychloroprene (CR), as a vulcanizing activator, cum was reinforcing filler. In this study, ZnO was replaced by the Zn ion-coated nanosilica filler with an aim of studying the dual role of this nanofiller in CSPE and CR. In the case of CSPE vulcanizates, the presence of MgO deteriorated the state and rate of cure when the Zn ion-coated nanosilica filler was used, but in the case of CR it improved the state of cure and enhanced the modulus and tensile strength. The Zn ion-coated filler proved to be a better reinforcing-cum-curing agent than was externally added ZnO and NA- 22 also proved to be a better curative in the presence of the Zn ion-coated nanosilica filler for both CSPE and CR. Keywords: vulcanization, chlorosulfonated polyethylene, polychloroprene, nanofiller, silica, zinc ion. Introduction Nanostructured composites consisting of layered inorganic solids and organic polymers have been widely investigated in recent years due to their interesting mechanical, thermal, optical, magnetic and barrier properties. 1 For polymer/clay nanocomposites, tremendously large interface surfaces are responsible for the benefits such as reinforcement with a low nanofiller loading. Some of these improvements can be achieved with conventional fillers but at 20-50% loading compared to 3-5% loading with nanofiller. Thus relatively small amounts of plate like clay particles, provided they are well dispersed into individual platelets, can result large improvements in composite properties. 2 The intercalation and exfoliation chemistry of epoxy-clay 3,4 nanocomposites have been successfully transferred to a thermoset polyurethane system. 5 Amine terminated butadiene- acrylonitrile (ATBN) intercalated clay has been used to form acrylonitrile-butadiene rubber (NBR)-nanocomposites. 6 Poly(styrene-butadiene) copolymer nanocomposites have been prepared using similar approach from modified clay. 7 Previous literatures suggested the use of layered clay for making the composites, but very little information is avail- able regarding the use of other nanofillers in the composite preparation specially their use as vulcanizing/curing aids. Recently Das et al. 8 have used Zn-ion coated nano silica filler as the vulcanizing aid for sulfur curing of styrene butadiene rubber (SBR) and suggested the dual action of such nano filler both as vulcanizing aid and rubber reinforc- ing agent. In this study we explore the possibilities of using Zn-ion coated nano silica filler as curing agent for halogen contain- ing polymers like chlorosulphonated polyethylene and poly- chloroprene. Rubber-nanofiller composites, thus prepared, were assessed for their technical properties. Experimental Chlorosulphonated polyethylene (CSPE), from Du Pont (USA) and polychloroprene rubber (CR), from Bayer (Ger- many), were mixed with nanofiller along with NA-22 from Du Pont (USA), and MgO from Loba Chemie (India), in a two roll open mixing mill at a fixed nip gap at around 35 o C. The nanofiller was Zn-ion coated silica having average par- ticle size 20 nm, which has been developed following the chemical process. The mixed compound was sheeted out from the two roll mixing mill and vulcanized by compression molding at 150 o C up to the optimum extent (t 90 ) under a pressure of 20 MPa. All technical properties were measured on this vulcanized sheet. Cure characteristics of the com- pounds were measured with a help of Monsanto Rheometer R-100 at 150 o C. Percent volume swell was studied by imm- ersing the sample in the toluene up to equilibrium. Tensile Notes