Rheological properties of calcium silicate‐filled isotactic polypropylene

Abstract

ABSTRACT:The melt rheological behavior of calcium silicate-filled isotactic polypropylene, with filler volume contents of 0 -17.8%, was determined at 493 K. The composites followed the power law in shear stress versus shear rate variations and were shear thinning. Initially, apparent melt viscosity decreased until a critical filler volume content of 8.5% was reached. However, on further increase in calcium silicate concentration, apparent melt viscosity increased. Melt elasticity also showed an initial decrease until 8.5% filler content was reached and then an increase beyond this filler content. Surface treatment of calcium silicate with a titanate coupling agent, LICA 38, modified the rheological properties because of the plasticizing/lubricating effect of LICA 38.

Rheological Properties of Isotactic Polypropylene/Alumina Composites

“…In i-PP=Al 2 O 3 composites at low f F values a flow favoring orientation of acicular Al 2 O 3 particles may give rise to this lowering of shear stress (4). Similar results were observed in iPP=Kaolin composites as well (11). In the i-PP=Al 2 O 3 =LICA 38 systems the flow curves also exhibit similar characteristics as their counterparts; at a fixed shear rate the extent of decrease and subsequent increase of shear stress is, however, less due to the modifying effect of LICA 38 through bonding of i-PP with Al 2 O 3 .…”

“…At a constant-g w , the Z app at first-decreases up to alumina volume % f F ¼ 5.8 whereas beyond this f F the data increased with f F . Similar results were observed in i-PP composites with kaolin and CaSiO 3 [11,12].…”

“…The n values were less than unity, being 0.348 AE 0.018 for i-PP=Al 2 O 3 and 0.326 AE 0.025 for i-PP=Al 2 O 3 =LICA 38 systems. This implies that the composite melts were pseudoplastic common to thermoplastic systems [11,13,21].…”

“…The rheological characterization of the systems are necessary to solve polymer processing problems. The melt viscosity and elasticity may decrease or increase with increase in filler concentration, depending on its shape and interaction with the matrix [9,12]. In isotactic polypropylene filled with wood flour and CaCO 3 , the melt viscosity increased and melt elasticity decreased with increase in filler concentration [9,13].…”

Melt shear viscosity of PP/Al(OH)3/Mg(OH)2 flame retardant composites at high extrusion rates

“…It has, therefore, received extensive attention in the past two decades. [15][16][17][18] In a study on rheological properties of calcium silicate-filled isotactic PP, Maiti et al 19 found that the apparent melt viscosity of the composites decreased until a critical filler volume content of 8.5% was reached. However, with further increase in calcium silicate concentration, apparent melt viscosity increased.…”