Microstructural characteristics of glass bead‐ and wollastonite‐filled isotactic‐polypropylene composites modified with thermoplastic elastomers

Abstract

Microstructural characteristics of isotactic-polypropylene/glass bead (iPP/GB) and iPP/wollastonite (iPP/W) composites modified with thermoplastic elastomers, poly(styrene-b-ethylene-co-butylene-b-styrene) copolymer (SEBS) and corresponding block copolymer grafted with maleic anhydride (SEBS-g-MA), were investigated. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic mechanical analyses (DMA) showed that the iPP/SEBS and iPP/SEBS-g-MA blends were partially compatible two-phase systems. Well-dispersed spherical GB and acicular W particles without evidence of interfacial adhesion were observed in the iPP/GB and iPP/W binary composites respectively. Contrary to the blends, melt flow rates of the iPP/GB and PP/W composites decreased more with SEBS-g-MA than with SEBS because of enhanced interfacial adhesion with SEBSg-MA elastomer. The SEM analyses showed that the ternary composites containing SEBS exhibited separate dispersion of the rigid filler and elastomer particles (i.e., separate microstructure). However, SEBS-g-MA elastomer not only encapsulated the spherical GB and acicular W particles completely with strong interfacial adhesion (i.e., core-shell microstructure) but also dispersed separately throughout iPP matrix. In accordance with the SEM observations, the DSC and DMA revealed quantitatively that the rigid filler and SEBS particles in iPP matrix acted individually, whereas the rigid filler particles in the ternary composites containing SEBS-g-MA acted like elastomer particles because of the thick elastomer interlayer around the filler particles. The Fourier transform infrared analyses revealed an esterification reaction inducing the strong interfacial adhesion between the SEBS-g-MA phase and the filler particles. POLYM. COMPOS.FIG. 12. Storage modulus (E 0 ) and damping factor (tan d) variations of the ternary composites as a function of temperature.

Optimization of mechanical properties of glass‐spheres‐filled polypropylene composites for extrusion‐based additive manufacturing

“…Previous studies by the authors [2] showed that the stiffness of neat PP is sufficient for the use in FFF. As the incorporation of glass-spheres in PP increases the Young's modulus [30], the stiffness requirement related to 3Dprinting is met by all filled composites of the present work. However, it was shown that only filled polypropylene compounds with a strength of minimum 13 MPa were successfully printable using a similar printing setup as described in "Impact Specimen Preparation" [2].…”

“…1b compares the tensile test results of the glass spherefilled PP compounds containing am.PO to those of neat PP. As expected, for both materials, the addition of am.PO leads to an increase in E Y due to the dilution of the composite with the rubbery and more ductile material [2,30,87]. Moreover, a reduction in crystallinity due to the addition of an amorphous component may contribute to the E Y enhancement [30] (see "Thermal Properties").…”

“…Their geometry allows good dispersion and a close packing, resulting in an improved dimensional stability for different thermoplastics [13,28,29]. So far, many studies have been devoted to PP filled with the conventionally used inorganic soda lime glass, also known as A-glass [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49]. Other glass types, such as the borosilicate glass (E-glass), have established themselves as the filling material of choice for glass-fiber reinforced composites [50], also in connection with PP [51][52][53].…”

Polypropylene Filled With Glass Spheres in Extrusion‐Based Additive Manufacturing: Effect of Filler Size and Printing Chamber Temperature

“…Compared to neat PP (T Cryst = 111.4 ± 0.7 °C), all the filled filaments exhibit considerably increased T Cryst , because glass spheres are known to nucleate PP. [12,45,46] The compound containing the smallest filler (PP/E-1) seems to nucleate the PP matrix in the most efficient way. Compared to neat PP, an increase of roughly 12% to 125.3 ± 0.9 °C is observed.…”

“…As expected, the incorporation of spherical fillers as well as the change in the T Ch influences the impact behavior of the printed parts (Figure 9). Independent of the processing conditions, all the composites exhibit a notched impact energy decreased by 70-90% compared to neat PP, because the incorporated microspheres can act as initiation points for defects [20,45,83] and can reduce the impact fracture area. [84,85] A similar decrease in the impact energy by 65% to 80% was observed for 3D-printed Charpy specimens of the same PP compound filled with the broadly distributed glass spheres Spheriglass 3000E in a previous work.…”