10urnal of Scientific & Industrial Research Vo1.58, October 1999, pp 795-798 Effect of Red Mud Addition on Abrasive Wear Rate of Isotactic PolypropylenelLow Density Polyethylene Blend under Low Stress Conditions Navin Chand a nd S A R H as hmi Regional Research Laboratory (CS IR ), Near Habibganj Naka, Bhopal 462 026, In dia Revised rece ived: 12 Apri l 1999; accepted: 24 June 1999 Wear characteristics of red mud (RM) filled iSOlac ti c polypropylene (PP)/I ow density polyethylene (LDPE) blends are reported. Elastic melt extruder, which was based on Weissenberg pump has bee n used for compounding th e LDPE, PP and RM. The effect of RM loading on th e abrasive wear behaviour is studied. Surfaces of the wo rn samples are examin ed us in g scanning electron microscope. The mecha ni sm of material removal is proposed with th e help of surface microstructure. Introducution Polymers and filled polymers have been studied un- der various sliding conditions because of their che mi cal resistance, hi gh damping properties, low noise e mi ssion, ability of dry sliding, etc. I - 3 • The problem associated with polymers lies in their low operating temperature due to which strength goes down due to the development of creeps under load. In such cases, particulate-filled poly- mers can provide a hi gh load capacity2. Th ese particu- late fillers red uced wear by modifyi ng the co unterphase or by changing the crystalline structure of a poly- mers or inhibiting the lar ge scale destruction of bonded structureo . In rece nt yea rs, many studies have been re- ported to expla in the wear behaviour of some selected polymeric systems such as te fl on-based mate ri als, but less attention has been focused on polyolefin blends. These polyol efin blt!nds can be modified by add iti on of fillers to improve flexural modulu s, dimensional stabil- it y, heat defl ection temperature, etc 7 - 12 . Tn previous pa- pers, Chand and Ha shmi 12- 16 reported th e mecha ni cal, rheological and morphologi ca l properties of red mud ( RM ) particles-fill ed PP/LDPE b le nd s. The tens il e modulus has been found to increase with th e add iti on of RM particles. In the present stud y, th e effect of red mud particulate loading on abrasive wear rate of PPILDPE (50/50) un - der low stress co nditions has been reported a nd exam- ined on the basis of thermal stability of the filled blend and the surface mi crostructure of th e wo rn s urfaces. Materials & Methods Materials Isotactic polypropylene (PP) powoer ( PN 670 ) was supp li ed by Mi s Takuyama Co . Ltd, Japan. The density of polypropylene used was 0.90 g/cm 3 and me lt flow index wa s 23 g il 0 min. Low density poly ethylene (G20 I) was obta in ed from Mis Seitetsu Kagaku Co. Ltd, Japan. The density of this polyethylene was 0.92 g/cm 3 with melt flow index as 2 gtJ 0 min . RM particles of the size less than 45 11m were sepa- rated by wet siev in g of red mud which was co ll ected fro m BALCO , Korba, India. Mineral phases, and struc- ture of RM particles used in this study have been re- ported in a previous co mmuni ca tion l2 • Chemical co n- stituents of RM particles were: AIP3 -18 .3 4 %, Fep ) - 35.85%, SiO l -8.80%, Ti0 2 -12.96%, Nap -4 .75 %, CaO -4. 15 %, L.I.O .- 14 .85 %. An eals ti c melt extruder fabricated on the principle of Weissenberg pump, was used for mixing the poly- mers and fi ll ers. This extrud er is better than other sys- tems for mixing of polymers. In the elastic extrude r, materials are fed direc tl y into th e shearing zone, which is built by th e rotor and stator. The effective diameter of the rotor was 14 cm. A sma ll screw was co nnected as a submecha ni sm in ser ies to the main shea ring zone to ensure stable operation. The ext ru sion die was attached at the end. Details of in strument have been descr ibed else where 17 .