Polymerization-filled composites prepared with highly active filler-supported Al/Ti/Mg catalysts. II. Properties of homogeneous polyethylene-based composites

Abstract

Polyethylene-based composites have been prepared by ethylene polymerization with a Al/Ti/Mg catalyst previously deposited on the surface of kaolin (Satintone W/W and Satintone 5) or barite.1 Molecular weight (M w ) of the polyethylene matrix has been estimated from melt viscosity under steady shear flow and compared to the value measured by size exclusion chromatography. Tensile stress and strain, Young modulus, and impact energy have been measured in relation to the matrix molecular weight and the filler content. The effect of the main polymerization parameters, such as the Al/Ti/Mg composition, the addition of a transfer agent, e.g., an a-olefin or hydrogen, have also been investigated. These tensile and impact properties have been compared to composites of the same composition but prepared by melt blending of the filler and the preformed polyolefin. As a rule, the polymerization-filled composites have an improved mechanical strength compared to the analogues prepared by melt blending.

Polyolefin-Clay Nanocomposites from Olefin Polymerization between Clay Layers

“…The preparation of polyolefin/clay nanocomposites from olefin polymerization is essentially the same although four types of catalysts including Ziegler-Natta catalysts [12][13][14][15][16][17][18][19][20][21][22], metallocene catalysts [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38], non-metallocene catalysts [39], and late transition metal (LTM) catalysts [40][41][42] are used. To achieve uniform dispersion of clay layers throughout polyolefin matrix, the key factor is the immobilization of precatalysts onto clay.…”

“…Using a magnesium based catalyst, very high catalyst efficiency was reached (14650 kg PE (mol Ti h) -1 ) for kaolin filler [13]. Whatever the investigated Al/Ti/Mg composition, the melting temperature (T m ) of the PE matrix is ca.…”

“…The filler particles were firstly coated by the growing PE chains, followed by the interconnection of the near neighbor particles through PE threads (Fig. (6)), thus increasing the mechanical strength of the composites due to improved compatibility between the polymer and the filler [13]. The superiority of polymerization-filled composites (PFCs) over melt-blended composites emerges from the comparison of the impact energy (I.E.…”

“…The superiority of polymerization-filled composites (PFCs) over melt-blended composites emerges from the comparison of the impact energy (I.E. ), the elongation at rupture ( r ), and the rc / yc tensile strength ratio [13]. With regard to an inorganic fiber, palygorskite, both the tensile strength and elongation at break were much lower for polyethylene/palygorskite nanocomposites prepared by in situ polymerization compared to the composites from melt blending due to poor bonding between polyethylene and palygorskite [14].…”

“…The molecular weight of these PP-clay nanocomposites could be controlled by the polymerization temperature and monomer concentration in the polymerization slurry. The isotacticity of the PP matrix varied over a very narrow range, typically from 95-98 %, as determined by 13 C NMR. Also realized in this case is the drastically improved Young's ten-sile modulus, up to 600 kpsi, which is well above the modulus of highly crystalline PP.…”