Effect and mechanism of hepta-phenyl vinyl polyhedral oligomeric silsesquioxane on the flame retardancy of silicone rubber. (January 2019)

• Record Type: Journal Article
• Authors: Wu, Tongyi; Qiu, Jiedong; Lai, Xuejun; Li, Hongqiang; Zeng, Xingrong
• Is Part Of: Polymer degradation and stability. Volume 159(2019)
• Page Start: 163
• Page End: 173
• Publication Date: 2019-01
• Subjects: Silicone rubber -- Hepta-phenyl vinyl polyhedral oligomeric silsesquioxane -- Flame retardancy -- Mechanical properties -- Thermal stability; Polymers -- Deterioration -- Periodicals; Stabilizing agents -- Periodicals; Polymères -- Dégradation -- Périodiques; Stabilisants -- Périodiques; 668.9
• DOI: 10.1016/j.polymdegradstab.2018.11.026
• Languages: English
• ISSNs: 0141-3910

Abstract

Abstract: It is challenging to simultaneously improve the flame retardancy and mechanical properties of silicone rubber. We herein proposed an efficient method to address this issue by incorporating hepta-phenyl vinyl polyhedral oligomeric silsesquioxane (HPVPOSS) into addition-cure liquid silicone rubber (ALSR). HPVPOSS meanwhile enhanced the flame retardancy and thermal stability of ALSR. With the addition of 10 phr HPVPOSS, ALSR passed the V-0 rating in the vertical burning test (UL-94) and had a limiting oxygen index (LOI) value as high as 31.0%. Moreover, compared with ALSR, the peak heat release rate and total heat release were decreased by 31.8% and 28.7%, respectively. Besides, the ALSR/HPVPOSS nanocomposites were demonstrated to have excellent mechanical properties. The possible flame retardant mechanism of HPVPOSS, which was attributed to the free-radical quenching effect and the catalysis effect on the crosslinking charring of ALSR, was further revealed. By generating the rigid core free-radicals and phenyl free-radicals, HPVPOSS suppressed the thermal degradation of ALSR in the condensed phase and quenched the active free-radicals in the gas phase. Moreover, HPVPOSS promoted the crosslinking charring of ALSR and the formation of a compact ceramic protection layer on the ALSR surface, effectively hindering the heat transfer and oxygen diffusion. Our findings provided a new way to fabricate silicone rubber with prominent flame retardancy and outstanding mechanical properties. Highlights: The flame retardancy and mechanical properties of ALSR were simultaneously improved by the incorporation of HPVPOSS. The ALSR/HPVPOSS nanocomposites were demonstrated to have decent thermal stability. The probable flame retardant mechanism of HPVPOSS was detailedly revealed and elaborated.