有机硅树脂耐高温改性方法及机理研究进展

有机硅树脂是一种性能优异的耐高温材料,在耐热领域具有广阔的应用前景。随着国防工业等的高速发展,传统的有机硅树脂热防护涂层难以满足当前发展的需要。因此,提高有机硅树脂的耐高温性具有极其重要的战略价值。文中从有机硅树脂的结构和特性出发,分析有机硅树脂的热稳定性机理及热降解机理。硅树脂的热降解主要来自于侧链降解、解链降解和重排降解。在此基础上,综述了侧链改性、主链改性、填料改性、封端、协同改性等方法对有机硅树脂耐热改性的研究进展,探讨了其优缺点,并展望了耐高温改性有机硅树脂未来的研究方向及应用前景。

A low-density polyethylene composite with phosphorus-nitrogen based flame retardant and multi-walled carbon nanotubes for enhanced electrical conductivity and acceptable flame retardancy

Design and exploitation of flame retardant polymers with high electrical conductivity are desired for polymer applications in electronics.Herein,a novel phosphorus-nitrogen intumescent flame retardant was synthesized from pentaerythritol octahydrogen tetraphosphate,phenylphosphonyl dichloride,and aniline.Low-density polyethylene was combined with the flame retardant and multi-walled carbon nanotubes to form a nanocomposite material via a ball-milling and hot-pressing method.The electrical conductivity,mechanical properties,thermal performance,and flame retardancy of the composites were investigated using a four-point probe instrument,universal tensile machine,thermogravimetric analysis,and cone calorimeter tests,respectively.It was found that the addition of multi-walled carbon nanotubes can significantly improve the electrical conductivity and mechanical properties of the low-density polyethylene composites.Furthermore,the combination of multi-walled carbon nanotubes and phosphorus–nitrogen flame retardant remarkably enhances the flame retardancy of matrixes with an observed decrease of the peak heat release rate and total heat release of 49.8%and 51.9%,respectively.This study provides a new and effective methodology to substantially enhance the electrical conductivity and flame retardancy of polymers with an attractive prospect for polymer applications in electrical equipment.

Boosting fire safety and mechanical performance of thermoplastic polyurethane by the face-to-face two-dimensional phosphorene/MXene architecture

Black phosphorus(BP), as one of the most promising fillers for flame retarding polymer, has been seriously limited in practical application, due to the agglomeration and poor structural stability challenges.Here, the BP was modified by MXene and polydopamine(PDA) via ultrasonication and dopamine modification strategy to improve the structural stability and dispersibility in the matrix. Then, the obtained(BP-MXene@PDA) nanohybrid was employed to promote the mechanical performance, thermal stability,and flame retardancy of thermoplastic polyurethane elastomer(TPU). The resultant TPU composite containing 2 wt.% of BP1-MXene2@PDA showed a 19.2% improvement in the tensile strength and a 13.8%increase in the elongation at break compared to those of the pure TPU. The thermogravimetric analysis suggested that BP-MXene@PDA clearly enhances the thermal stability of TPU composites. Furthermore,the introduction of the BP-MXene@PDA nanohybrids could considerably improve the flame retardancy of TPU composite, i.e., 64.2% and 27.3% decrease in peak heat release rate and total heat release, respectively. The flame-retardant mechanisms of TPU/BP-MXene@PDA in the gas phase and condensed phase were investigated systematically. This work provides a novel strategy to simultaneously enhance the fire safety and mechanical properties of TPU, thus expanding its industrial applications.