Hollow glass microspheres having an average diameter of less than about 500 micrometers, also commonly known as “glass microbubbles”, “glass bubbles”, “hollow glass beads”, or “glass balloons” are widely used in industry, for example, as additives to polymeric compositions. In many industries, hollow glass microspheres are useful, for example, for lowering weight and improving processing, dimensional stability, and flow properties of a polymeric composition. Hollow glass microspheres have been incorporated into polypropylene composites for certain applications. See, for example, U.S. Pat. No. 7,365,144 (Ka et al.) The need for light weight solutions in polymer industry, for example for automotive applications, raises more and more interest in thermoplastic compounds including hollow glass microspheres.
The addition of glass bubbles to thermoplastics may, however, reduce the impact properties of the compounds. For polypropylene which is widely used in automotive interior applications also a decrease of tensile strength can be observed. In automotive interior applications, safety issues always have to be considered, and, therefore, the lack of sufficient impact properties, particularly notched impact strength, limits the possibilities to use thermoplastic compounds with added glass bubbles. In order to retain the impact properties, impact modifiers may be used. The positive effect on impact strength by impact modification combined with appropriate compatibilization was presented during the ANTEC conference 2014 (SPE ANTEC 2014, 2223-2228).
However, it has to be considered that the use of impact modifiers not only improves impact properties but also decreases strength and tensile modulus. For automotive interior applications, however, well balanced properties are required.
Therefore, a need still exists to improve the mechanical properties, i.e. tensile strength, tensile modulus and impact strength, of thermoplastic compounds with hollow glass microspheres.