Silica having amine functional groups (A-SiO2) obtained by the sol-gel process was used to improve compatibility of polyamide 11 and poly(phenylene oxide) (PA11/PPO 80/20) blend via reactive extrusion in a co-rotating twin screw extruder. Amine functional groups of A-SiO2 can react with the carboxyl groups of PA11 to form graft copolymer with PA11 which can efficiently control the phase morphology of the blend. Silica, thanks to the reinforcing effect, significantly increased stiffness of PA11/PPO blend. On the other hand, it greatly improved impact strength and reduced the crystallinity without affecting the crystallization temperature of PA11due to excellent compatibilizing effect. SEM results showed that despite the lower content of PPO, it formed a continuous phase and PA11 - a dispersed. The addition of A-SiO2 changed the morphology from the droplet-matrix to co-continuous with interpenetrating phases. The greatest size-reduction of both phases, reflecting the highest impact toughness, was observed for the content of 3 wt % A-SiO2. With a higher silica loading, phase inversion was observed with the reappearance of the droplet structure, resulting in a slight decrease in impact strength and significant in elongation at break. TGA showed that the composites exhibited better thermal properties as evidenced by the higher initial degradation temperature (Tonset) and the maximum weight loss rate temperature (Tmax).
Zastosowanie odpadowego fosfogipsu w kompozytach termoplastycznych i chemoutwardzalnych APPLICATION OF WASTE PHOSPHOGYPSUM IN THERMOPLASTIC AND CHEMOSETTING COMPOSITES Summary-Application of thermally treated phosphogypsum as a filler for thermoplastic polymers such as low density polyethylene, polypropylene, polyamide 6 and PVC as well as for chemically cured composites based on epoxy or polyester resins has been investigated. Phosphogypsum used was a by-product from phosphorous fertilizers' industry (Table 1), and was treated by method elaborated in Poland. Amounts of phosphogypsum were in the range of 10-50 wt. % in PE-LD, PP or PA 6, 97.5-205 phr in PVC (Table 2) and 30-50 wt. % in chemically cured composites (Table 3 and 4). Phosphogypsum as filler causes similar changes of mechanical properties as another mineral fillers. Filled thermoplastic composites were tested with the aim to substitute talc or chalk with treated phosphogypsum (Table 8, Figs. 3-6). Effect of silanes as compatibilizers for thermoplastic composites was investigated, too. Composites polypropylene/phosphogypsum were used for preparation of automotive fittings instead of polypropylene/talc ones (Fig. 10). PVC compositions with treated phosphogypsum were used for preparation of flooring (Fig. 11). Chemically cured composites with treated phosphogypsum were used for preparation of self-leveling flooring.
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