The relationship between molecular structure and the effect of coupling agents in flame-retardant ABS blends

Tetrabromobisphenol A and antimony trioxide were used as flame-retardant ad ditives in flame-retardant acrylonitrile-butadiene-styrene (FR-ABS) blends. Four types of coupling agents, LICA 38, LICA 44, NZ 38, and SMA-g-L44, wer e employed to improve the physical properties of the blends by inorganic su rface treatment. The molecular structures of these coupling agents differ f rom each other in the polymer binding functional groups (PB groups), the ce ntral tetravalent metal, and the molecular weight. The octyl molecular segm ents in the PB groups of the coupling agents are advantageous to the tensil e strength and elongation of FR-ABS. The high-MW coupling agents, SMA-g-L44 copolymers, provide the highest impact resistance and elongation of all. T he coupling agent with the central metal Zr brings better tensile propertie s to FR-ABS than Ti does; however, Zr will slightly decrease the LOI of FR- ABS. All the coupling agents are able to lower the glass transition tempera ture and increase the thermal resistance of FR-ABS blends. Finally, the dis appearance of both voids and the interfacial boundary are clearly observed in scanning electron microscope (SEM) photographs. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.