Matjaž Denac

Effects of talc and gamma irradiation on mechanical properties and morphology of isotactic polypropylene/talc composites

Although isotactic polypropylene (iPP) has become one of the largest and fastest growing polymeric materials, some disadvantages in its properties, like poor stability to gamma (γ) irradiation, may impede its growth in commercial use. The popularity of γ irradiation use to sterilize iPP and iPP composites devices is increasing. The purpose of our research work was to examine the effects of talc and low dose γ irradiation on mechanical properties and the morphology of iPP and iPP/talc composites. The samples were prepared in a Brabender kneading chamber and by compression molding on a laboratory press. The iPP and iPP/talc composites were characterized by tensile testing, measurements of notched impact strength, FTIR spectroscopy, differential scanning calorimetry, optical microscopy, scanning electron microscopy and wide angle X-ray diffraction. The role of untreated talc or talc surface treated with aminosilanes as well as the influence of γ irradiation on mechanical properties and the morphology of modified iPP is discussed.

Interfacial and mechanical properties of polypropylene/silica nano- and microcomposites

Various silica grades differing in particle size (micro- versus nanosilica) and surface modification (untreated versus modified surface) have affected interfacial and mechanical properties of compression-molded polypropylene composites with 2, 4, 6, 8 vol% of added silica. Mechanical properties have been influenced primarily by combination of stiff fillers and tough polypropylene matrix and additionally by restructured matrix. Namely, silica particles with different surface properties have influenced nucleation and spherulite growth differently affecting thus tensile properties of the composites. All composites exhibited best tensile strength in silica content range 2–6 vol%.

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

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. GRAPHICAL ABSTRACT

Polypropylene Blends with m-EPR Copolymers: Structure, Morphology and Thermal Properties

ABSTRACT The effects of different contents of two metallocene propylene-based m-EPR elastomers on structure, morphology, thermal, and dynamic mechanical properties of the isotactic polypropylene/m-EPR blends were investigated. The both m-EPR copolymers have been built in isotactic polypropylene matrix as amorphous phase. However, the nucleation effect at lowest addition (2.5 vol%) and the solidification effect along with increased m-EPR’s additions have caused changes of the crystallinity degree and the size of spherulites in the isotactic polypropylene matrix. Higher degree of miscibility/compatibility of the isotactic polypropylene/m-EPR2, with lower viscosity has been observed. Homogeneous dispersion of m-EPR particles as well as their radial distribution has been observed. GRAPHICAL ABSTRACT

Polypropylene Blends with m-EPR Copolymers: Mechanical and Rheological Properties

The effects of two metallocene ethylene-propylene-based elastomers (m-EPR1 and m-EPR2) differing in molecular mass and viscosity on mechanical, rheological and interfacial properties were compared. The m-EPR elastomers were added to iPP in 2.5, 5, 10, 15, and 20 vol.%. Torque values, elongation at break and impact strength measured of the iPP/m-EPR1 blends were higher than the iPP/m-EPR2 blends due to higher molten viscosity of m-EPR1 than m-EPR2 copolymer. Slight differences in Young moduli as well as in tensile strength at yield and at break might indicate that tensile properties of iPP/m-EPR blends were not significantly affected by difference in viscosity or molecular mass, miscibility and spherulite size. Optimization diagrams indicated the metallocene m-EPR copolymers are efficient impact modifiers for polypropylene and showed good balancing of mechanical properties in iPP/m-EPR blends.