Vinyl Epoxy Resins Research Articles

Synergistic effects of a half‐cage and cage structure phosphorus and nitrogen‐containing POSS with tetrabutyl titanate on flame retardancy of vinyl epoxy resins

AbstractTo improve the flame retardancy of vinyl epoxy (VE) resins more effectively, a half‐cage and cage structure polyhedral oligomeric silsesquioxanes (P/N‐POSS) containing phosphorus and nitrogen was synthesized by a one‐step Kabachnik‐Fields reaction from paraformaldehyde, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and 3‐aminopropyltriethoxysilane. It was then blended with tetrabutyl titanate (TBT) in VE resins to construct a phosphorus‐nitrogen‐silicon‐titanium synergy flame retardant system. P/N‐POSS was well dispersed in the VE matrix at low loadings (≤4 wt%). With the addition of only 4 wt% P/N‐POSS and 0.2 wt% TBT, the LOI value reached 29.2 and the UL‐94 grade passed V‐1 rating. Moreover, compared with VE‐0, the peak heat release rate, total heat release, smoke production rate and total smoke production decreased significantly. The investigations on pyrolysis volatiles and char residue of cured VE composites revealed that the excellent flame retardancy of the VE composites were due to the superior free radical capturing ability, the dilution effect of P/N‐POSS in the gas phase, and the promoting the carbonation effect of P/N‐POSS, the catalyzing char formation ability of TBT in the condensed phase. Meanwhile, VE composites exhibited improved mechanical properties, thermal stabilities and retained the low viscosity and good processability of VE resins.

Synergistic Effects of Ladder and Cage Structured Phosphorus-Containing POSS with Tetrabutyl Titanate on Flame Retardancy of Vinyl Epoxy Resins.

The cage and ladder structured phosphorus-containing polyhedral oligomeric silsesquioxanes (DOPO-POSS) have been synthesized through the hydrolytic condensation of 9,10-dihydro-9-oxa-10-phosphenanthrene-10-oxide (DOPO)-vinyl triethoxysilane (VTES). The unique ladder and cage–ladder structured components in DOPO-POSS endowed it with good solubility in vinyl epoxy resin (VE), and it was used with tetrabutyl titanate (TBT) to construct a phosphorus-silicon-titanium synergy system for the flame retardation of VE. Thermal stabilities, mechanical properties, and flame retardancy of the resultant VE composites were investigated by thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA), three-point bending tests, limiting oxygen index (LOI) measurement, and cone calorimetry. The experimental results showed that with the addition of only 4 wt% DOPO-POSS and 0.5 wt% TBT, the limiting oxygen index value (LOI) increased from 19.5 of pure VE to 24.2. With the addition of DOPO-POSS and TBT, the peak heat release rate (PHRR), total heat release (THR), smoke production rate (SPR), and total smoke production (TSP) were decreased significantly compared to VE-0. In addition, the VE composites showed improved thermal stabilities and mechanical properties comparable to that of the VE-0. The investigations on pyrolysis volatiles of cured VE further revealed that DOPO-POSS and TBT exerted flame retardant effects in gas phase. The results of char residue of the VE composites by SEM and XPS showed that TBT and DOPO-POSS can accelerate the char formation during the combustion, forming an interior char layer with the honeycomb cavity structure and dense exterior char layer, making the char strong with the formation of Si-O-Ti and Ti-O-P structures.

New Chemical Grouting Materials and Rapid Construction Technology for Inclined Shaft Penetrating Drift‐Sand Layer in Coal Mine

Drift‐sand layer is a common weak stratum in mine construction. The construction of the shaft passing over the drift‐sand layer is very difficult. Traditional construction method faces many problems such as long construction period, high construction cost, poor working environment, and uncontrollability of the support effect. In view of the loose and fragile rock mass with great deformation of sinking and driving engineering penetrating drift‐sand layers in coal mine, the reaction mechanism and shortcomings of conventional chemical grouting materials were analyzed. New‐type polymer grouting materials were prepared with catalysts and vinyl epoxy resin, which was made from epoxy resin. A comprehensive chemical grouting construction technology was proposed, which comprises initiative closing, concentrated bypass flow, water plugging priority, and secondary sand curing for the inclined shaft passing over the drift‐sand layer. Results show that new‐type polymer sand‐cured materials have lower viscosity, better grout ability, and fire resistance, and the solidified material has stronger bonding strength and better deformation resistance compared with traditional chemical grouting materials. The engineering application effect is very prominent in controlling water burst and leakage at the drift‐sand layer; thus the on‐site comprehensive construction progress and safety are guaranteed.

Simple Synthesis of Hydroxyl and Ethylene Functionalized Aromatic Polyamides as Sizing Agents to Improve Adhesion Properties of Aramid Fiber/Vinyl Epoxy Composites.

To improve interfacial adhesion between aramid fibers and vinyl epoxy resins, a series of hydroxyl and ethylene-functional aromatic polyamides ((ClPPTA)m-R′) with different chain segments were successfully synthesized via a one-pot low-temperature polycondensation. The hydroxyl and ethylene-functional aromatic polyamides were characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state 13C CP/MAS nuclear magnetic resonance spectroscopy (13C CP/MAS NMR), thermal gravimetric analysis (TGA), and wide-angle X-ray diffraction (WXRD). The contact angle of the hydroxyl and ethylene-functional aromatic polyamides films were measured. The hydroxyl and ethylene-functional aromatic polyamides were used as the sizing agents for aramid fiber/vinyl epoxy composites. The surface chemical composition and morphology of the unsized and sized fibers were identified using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The interfacial adhesion between aramid fibers and vinyl epoxy composites was investigated by the micro-debond tests. The results showed that the interfacial shear strength between the sized aramid fibers and vinyl epoxy composites was greatly improved.