A strategy and mechanism of fabricating flame retarding glass fiber fabric reinforced vinyl ester composites with simultaneously improved thermal stability, impact and interlaminar shear strengths

Poor flame retardancy, even worse than that of their matrix, is the common bottleneck for glass fiber (GF) reinforced polymeric composites (GFRPs), however, overcoming this problem generally degrades other performances of GFRPs. Herein, new GF fabric (PHSi-g-GF) grafted with phosphorus-containing hyperbranched polysiloxane (PHSi) through grafting-from technique, and new matrix (PSiVE) consisting of vinyl ester matrix (VE) and PHSi were prepared to develop new composites; meanwhile other three kinds of composites (GF/VE, PHSi-g-GF/VE, GF/PSiVE), of which at least one composition (matrix or fabric) is the original one, were also fabricated. The flame retardancy, thermal and mechanical performances of these composites were intensively studied and compared. Results show that PHSi-g-GF/VE and GF/PSiVE composites have much better integrated performances than GF/VE composite. Interestingly, the PHSi-g-GF/PSiVE composite has the best flame retardancy, for example, compared with GF/VE composite, PHSi-g-GF/PSiVE composite has 7 s longer time to ignition and 34% lower peak of heat release rate as well as 13% higher limited oxygen index and much higher UL-94 grade. This is originated from the unique dual flame retarding mechanisms in both gaseous and condensed phases. In addition, PHSi-g-GF/PSiVE composite has significantly improved thermal stability, 14% higher interlaminar shear and 60% higher impact strengths than GF/VE composite, completely overcoming the common problems of GFRPs. The presence of PHSi provides good interaction between GF and matrix as well as toughening effect on VE resin due to the flexible Si-O-Si chain and cavity structure of PHSi. These attractive improvements in the performances of PHSi-g-GF/PSiVE composite demonstrate that the method and mechanism provided herein are effective to develop high performance GFRPs.