Abstract:

Unsaturated polyester （UP） resin composites were modified with an intumescent flame?retardant （IFR） system based on the mela mine?coated a mmonium polyphosphate （APP）， pentaerythritol （PER）， and mela mine （MEL）， and the effect of APP/PER/MEL mass ratio and total amount on the flame retardant and mechanical properties of the UP/IFR composites were investigated. According to the optimal mass ratio of IFR， alu minum diethyl phosphate （ADP） was then added into the UP/IFR composites as a flame?retardant synergistic agent， and the flame retardant properties， mechanical properties， and thermal stability of UP/IFR?ADP composites with different content of ADP were evaluated. The results indicated that the composites achieved a UL 94 V?0 classification in the vertical burning test at a APP/PER/MEL mass ratio of 4∶1∶1， a IFR content of 15 wt%， and a limiting oxygen index （LOI） of 27.4 vol%， and their flexural strength and impact toughness were 100.3 MPa and 6.3 kJ/m²，respectively. The introduction of ADP further improved the flame retardancy of IFR/UP composites， and the flame?retarding effect was enhanced with an increase in the mass fraction of ADP. When the mass fraction of ADP was 2 wt%， the UP/IFR?ADP composites obtained an LOI of 28.5 vol%， a UL?94 V?0 classification， flexural strength of 110 MPa， and impact toughness of 7.8 kJ/m². Compared to the UP/IFR composite containing 15 wt% of IFR， the UP/IFR?ADP composites achieved an increase in flexural strength by 9.7 % and in impact toughness increased by 23.8 %. TG analysis results indicated that ADP could promote the formation of amorphous char layer and slow down the thermal degradation of the matrix.

Key words: unsaturated polyester resin, flame retardancy, aluminum diethyl phosphate