Morphology of polypropylene/silica nano‐ and microcomposites

Abstract

The aim of this study was to compare the effects of different silica grades on the structure and morphology of isotactic polypropylene (iPP)/silica composites to better understand their structure-property relationships. Isotactic polypropylene composites with 2, 4, 6, 8 vol % of added silica fillers differing in particle size (micro-vs. nanosilica) and surface modification (untreated vs. treated surface) were prepared by nonisothermal compression molding and characterized by different methods. The addition of all silica fillers grades to the iPP matrix significantly influenced the spherulitic morphology, while phase characteristics of the iPP matrix seemed to be unaffected. Surface modification of silica fillers exhibited stronger effects on spherulite size than size of silica particles. Nonpolar silica particles, more miscible or compatible with iPP chains than polar silica particles, enabled better spherulitic growth. The spherulite sizes tended to reach equal values at 8 vol % of added silicas showing that spherulite size became independent of filler concentration and surface modification above optimum filler concentration.

Morphology and Mechanical Properties of iPP/Silica Composites Modified with (Styrene-b-ethylene-co-butylene-b-styrene) Grafted with Maleic Anhydride

“…The addition of all silica grades to plain iPP decreases the size of spherulite due to their nucleation ability. [15] Even the treated nonpolar S-D17 microsilica with minimal nucleation ability decreases the spherulite size, as illustrated by polarized optical micrographs in Figs. 6 a,b. On the other hand, an increase in spherulite size with the increasing elastomer content (Fig.…”

“…The largest spherulites were observed in composites containing the S-D17 non-polar silica filler that exhibits the weakest nucleation ability because its surface is compatible with the iPP matrix. [15,32] Preferential iCS and SM morphologies with a significant iPPÀS-D17 interface area may reduce nucleation and additionally enhance the spherulite growth.…”

“…The volume content ratio iPP/SiO 2 96/4 was chosen because all binary iPP/SiO 2 composites exhibit the best spherulitic morphology and tensile strength values in the silica content range 2 À 6%. [15,16] A relatively wide (0-20%) SEBS-g-MA elastomer content range was used in order to explore its efficiency as impact modifier (not only as compatibilizer). The components were put into the kneading chamber preheated up to 200°C with the rotor speed of 50 min À1 , then kneaded for 7 min.…”

Polypropylene/silica micro‐ and nanocomposites modified with poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene)

“…10,28 Relatively wide content range 0-20 vol % of added SEBS elastomer was used in order to research its efficiency as compatibilizer (5 vol %) as well as impact modifier and compatibilizer at higher SEBS content. The iPP/SiO 2 volume ratio was kept constant at 96/4 and 5, 10, 15, and 20 vol % of SEBS elastomer was added to 100 volume parts of composite (added 20 vol % of SEBS corresponds to 16.7 vol % of SEBS in total mass).…”

“…Presented results confirm common findings in literature that the filler is not fully located only in one phase or only at interface. 10,27,28 Schematic presentation in Figure 4 reveals mainly interspherulitic acommodation of large micro-sized S-D17 particles beside some S-D17 particles engulfed by iPP spherulites. Polarization micrographs of binary iPP/silica composites indicated that silica particles with polar surfaces like A-R7200 more significantly decreased the spherulite size than silica particles with hydrophobic, non-polar surfaces like S-D17 due to stronger nucleation effect.…”