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Pustak A.S.S.,Ruder Boskovic Institute | Denac M.,Institute of Technology | Leskovac M.,University of Zagreb | Svab I.,Production and Processing of Thermoplastics Ltd | And 2 more authors.
Journal of Applied Polymer Science | Year: 2015

The effects of different silica loadings and elastomeric content on interfacial properties, morphology and mechanical properties of polypropylene/silica 96/4 composites modified with 5, 10, 15, and 20 vol % of poly(styrene-b-ethylene-co-butylene-b-styrene) SEBS added to total composite volume were investigated. Four silica fillers differing in size (nano- vs. micro-) and in surface properties (untreated vs. treated) were chosen as fillers. Elastomer SEBS was added as impact modifier and compatibilizer at the same time. The morphology of ternary polymer composites revealed by light and scanning electron microscopies was compared with morphology predicted models based on interfacial properties. The results indicated that general morphology of composite systems was determined primarily by interfacial properties, whereas the spherulitic morphology of polypropylene matrix was a result of two competitive effects: nucleation effect of filler and solidification effect of elastomer. Tensile and impact strength properties were mainly influenced by combined competetive effects of stiff filler and tough SEBS elastomer. Spherulitic morphology of polypropylene matrix might affect some mechanical properties additionally. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41486. © 2014 Wiley Periodicals, Inc. Source


Smit I.,Ruder Boskovic Institute | Denac M.,University of Maribor | Svab I.,Production and Processing of Thermoplastics Ltd | Radonjic G.,University of Maribor | And 3 more authors.
Polimeri (Zagreb) | Year: 2010

Binary isotactic polypropylene (iPP) composites with talc and wol-lastonite were modified with different elastomers: poly(styrene-b-outadiene-b-styrene) (SBS), poly(styrene-b-ethylene-co-propylene) (SEP), poly(styrene-b-ethylene-co- butylene-b-styrene) (SEBS), SEBS grafted with maleic anhydride (SEBS-g-MA), ethylene/propylene/ diene terpolymer (EPDM), and propylene-based metallocene (mEPR) at different content ratios and studied by different microscopic techniques (optical, SEM, TEM), wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Complex investigations of the structure-property relationships by comparison of ternary İPP composites with constitutive binary composites and binary blends showed that different factors affect (re)structuring of the semicrystalline polypropylene matrix during its crystallization and solidification during preparation by compression moulding. Structural investigations were focused on determination of influencing factors in crystallite and spherulite growth, phase structure of the İPP crystallites, degree of crystallinity, orientation of filler particles and İPP crystallite, structuring/spherulitization of the İPP matrix, and phase morphology of particles and polypropylene composite and constitutive blend systems. From the interplay of different factors in structuring of the İPP matrix the following influencing factors could be recognized: (i) nucleation by tiny dispersed particles of polymers and filler particles, (ii) orientation of the İPP crystallite and filler particles, (iii) migration/transferring of the İPP chains from melt islands to growing lamellae during solidification, (iv) encapsulation of dispersed/filler particles leading to core-shell morphology, (v) steric hindrance factors generated by filler and dispersed elastomer particles in the spherulitization of the İPP matrix, and (vi) possible partly co-crystallization in the iPP/propylene-based metallocene copolymer (iPP/mEPR) regions. Source


Pustak A.,Ruder Boskovic Institute | Pucic I.,Ruder Boskovic Institute | Denac M.,University of Maribor | Svab I.,Production and Processing of Thermoplastics Ltd | And 3 more authors.
Journal of Applied Polymer Science | Year: 2013

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. © 2012 Wiley Periodicals, Inc. Source


Pustak A.,Ruder Boskovic Institute | Denac M.,University of Maribor | Leskovac M.,University of Zagreb | Svab I.,Production and Processing of Thermoplastics Ltd | And 2 more authors.
Polymer - Plastics Technology and Engineering | Year: 2015

The effects of different silica grades and elastomer content on interfacial properties, morphology and mechanical properties of polypropylene/silica 96/4 composites modified with added 5, 10, 15, and 20% of poly(styrene-b-ethylene-co-butylene-b-styrene) grafted with maleic anhydride (SEBS-g-MA) were investigated. The iPP/silica/SEBS-g-MA composites were designed by adding four silica fillers differing in size (nano- vs. micro-) and in surface properties (hydrophilic vs. hydrophobic) and SEBS-g-MA that was used as a proven effective impact modifier and compatibilizer simultaneously. The morphology of every composite was a spectrum of several morphologies rather than one exclusive morphology. Good concordance between observed and predicted morphology indicated that the morphology of a particular composite was controlled primarily by interfacial properties. Tensile and impact properties were influenced primarily by competitive effects of a stiff filler and tough SEBS-g-MA elastomer. Increased impact strength and strain at break caused by adding SEBS-g-MA indicated a significant overcoming of the elastomeric toughening effect in relation to the filler’s stiffening effect. © 2015, Copyright © Taylor & Francis Group, LLC. Source


Pustak A.,Ruder Boskovic Institute | Denac M.,University of Maribor | Leskovac M.,University of Zagreb | Svab I.,Production and Processing of Thermoplastics Ltd | And 2 more authors.
Journal of Polymer Research | Year: 2016

The effects of different silica (SiO2) types and different contents of two metallocene propylene-based m-EPR elastomers (differing in molecular weight and viscosity) on interfacial properties, structure and morphology of isotactic polypropylene/SiO2/m-EPR composites were investigated. Four silica fillers differing in size (nano- vs. micro-) and surface properties (hydrophilic vs. hydrophobic i.e. polar vs. non-polar) were chosen and added in 4 vol% to isotactic polypropylene. The m-EPR elastomers were added to iPP/SiO2 96/4 composites as possible impact modifier and compatibilizer at the same time in 5, 10, 15, and 20 vol% per 100 vol% of composites (phr). The investigation confirmed the overall prevailing of separated morphology of ternary iPP/SiO2/m-EPR composites, i.e. selectivity of dispersed m-EPR and silica particles toward iPP matrix as was predicted on the basis of adhesion properties. The increase of crystallinity degree and spherulite size with addition of m-EPR elastomers indicated significant solidification effect of added elastomers in addition to opposite nucleation effect of silica particles owing to surface character of filler. The effects of different silica fillers and different contents of two m-EPR elastomers were discussed within the context of morphology/structure-adhesion property relationships of the iPP/SiO2/m-EPR composites. © 2016, Springer Science+Business Media Dordrecht. Source

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