Silane and silazane surface modification of recycled glass fibers for polypropylene composites

Abstract

Glass fiber (GF) composites are one of the significant challenges in recycling thermoset materials. After pyrolysis, the glass fibers lack sufficient strength and show poor matrix compatibility. Here we have investigated a series of multifunctional silane and silazane agents for surface modification of recycled glass fibers that provide a combination of hydrophobic properties and residual reactive groups on the surface. This allowed testing of interfacial effects from the surface modification as well as a potential synergistic compatibilization using maleated PP (MAPP). The treated GFs were used to prepare new polypropylene (PP) composites by multiple extrusion steps, resulting in a series of composites where the dispersion efficiency was attributed mainly to the surface chemistry and compatibilization effects. The amino-silane modifications of the recycled fibers resulted in further improvements in the mechanical properties of the PP composites in comparison with the hydrophobized GFs. Moreover, synergistic effects from the addition of MAPP were observed with scanning electron microscopy. The results clearly demonstrate that the surface modifications were effective and good alternatives to currently used methods.

Ein Überblick zum Recycling und zur Verwertung glasfaserverstärkter Kunststoffe

“…Eine Fasernachbehandlung kann diese Auswirkungen deutlich verringern. Dabei wird auf die Reinigung der Faseroberfläche, das Wegätzen beschädigter Oberflächenschichten oder auf die nachträgliche Härtung der GF, zum Teil in Kombination mit einem neuen Schlichteauftrag [47] gesetzt. So wurde nach 30-minütiger Behandlung von GF bei 450-600 °C ein Verlust der Zugfestigkeit von 70-80 % beobachtet.…”

“…Dabei wird, abgesehen vom mechanischen Recycling, bei allen übrigen Recyclingverfahren auch die Schlichte nahezu vollständig von den GF entfernt [46]. Ein nachträglicher Schlichteauftrag kann die Qualität der rGF erheblich verbessern [47].…”

Surface Treatment Effect on the Mechanical and Thermal Behavior of the Glass Fabric Reinforced Polysulfone

“…Silanization of the GF surface usually proceeds via GF treatment in the solution of silane; the solvent may be either organic, such as ethanol [ 17 , 18 , 19 , 20 , 21 , 22 , 23 ], methanol [ 24 ], toluene [ 25 ], cyclogexane [ 26 ] or tetrohydrofuran [ 27 ] or water-based [ 28 , 29 , 30 , 31 ]. Silanized GF are widely used for polymer reinforcing.…”

“…The use of another matrix polymer, such as polylactide acid (PDA) [ 24 , 32 , 33 ], polypropylene [ 22 , 31 ], polypropylene oxide [ 28 ], polyoxymethylene [ 22 ] and polyamide 6.6 [ 21 ] were reported also. Filler in such composites may represent GF in a short [ 20 , 22 , 24 , 27 , 29 , 31 , 32 , 33 ], unidirectional [ 23 , 25 ] or fabric [ 17 , 18 , 19 , 21 , 28 , 30 ] state. Silane treatment of GF allows for an increase in the composite density [ 18 , 29 ], i.e., to decrease the defectivity of the macrostructure.…”