Epoxy-Functionalized POSS and Glass Fiber for Improving Thermal and Mechanical Properties of Epoxy Resins  
[PERSON]  
1 School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China 12 China (Yangzhou) Material Handling Tech-Engineering Ltd., Yangzhou 225009, China 2  
[PERSON]  
1 School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China 1  
[PERSON]  
1 School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China 1  
[PERSON]  
3 Tianjin Joaboa Technology Co., Ltd., No. 24 Road, Tianjin 301609, China 3  
[PERSON]  
1 School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China 14  
The functional POSS is a class of intramolecular organic-inorganic hybrid material with a three-dimensional cage-like network structure, which contains a thermally stable inorganic core composed of Si-O bond, while the outer side of the cage is surrounded by substituent R groups (R = hydrogen, alkyl, epoxy group, arylene group, or other organic functional derivatives) [20]. The diameter of the cubic cage core of POSS is about 0.53 nm. POSS possesses many excellent properties, such as nano-size effects, excellent thermal stability, and molecular designable ability, because of its special micro-hybrid structure. Thus, functional POSS offers opportunities to modify polymers on the molecular level and has potential applications in compatibilities organic and inorganic materials. Many researchers studied POSS/epoxy resin composites and found that thermal and mechanical properties of epoxy resins could be improved by incorporating POSS into epoxy resins. [PERSON] et al. [21] investigated the MAP-POSS/epoxy resins' nanocomposites, and the dynamic mechanics showed that the glass transition temperature (T\({}_{\text{g}}\)) had a slight increase when the MAP-POSS content was between 4 wt% and 8 wt%. The T\({}_{\text{g}}\) of an 8 wt% MAP-POSS/epoxy resin sample was 175.6 \({}^{\circ}\)C, which was 6.1 \({}^{\circ}\)C higher than the pure epoxy resin. [PERSON] et al. [22] introduced EP-POSS and SiO\({}_{2}\) into epoxy resins; their results showed that the impact strength, flexural strength, and modulus of the SiO2/EP-POSS/epoxy composites increased by around 57.9, 14.1, and 44.0%, compared with the pure epoxy resin. POSS (which contains a partial T8 cage with one corner Si missing, leaving three Si-OH groups) with free Si-OH groups can be grafted on the epoxy resin's chain to improve flame retardancy by forming a stable char layer to protect decomposition [23]. [PERSON] et al. [24] found that the amine-functionalized POSS could act as a coupling agent for epoxy resin/GF-reinforced nanocomposites. [PERSON] et al. [25] synthesized the biphenyl diol formaldehyde resin as a curing agent and found that POSS with glycolydixopropyl groups can improve the mechanical and thermal properties of the composite.  
Figure 1: The chemical structures of (**A**) functional POSS, (**B**) polyethylenepolyamine (PEPA), (**C**) E51 resin, and (**D**) the preparation of E-POSS.  
It has been well established that the mixed species could exert a significant influence on the mechanical and thermal properties of epoxy resins. To the best of our knowledge, little attention has been focused on the ternary composite of E51, POSS, and GF (E51 + E-POSS + GF). In this work, both E-POSS and GF were used to improve the properties of polyethylenepolyamine (PEPA)-cured epoxy resins. The influence of E-POSS and GF on mechanical properties and thermal stability was investigated in detail.