Qilong Tai

Synthesis, structure–property relationships of polyphosphoramides with high char residues

A series of polyphosphoramides with high char residues were successfully synthesized using solution polycondensation and well characterized. The thermal properties and flammability were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC). The evolved gases during decomposition were also analyzed using Fourier transform infrared coupled with the thermogravimetric analyzer (TG-IR) technique. The char residues of the polyphosphoramides were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and Raman spectroscopy. The results showed that polyphosphoramides with sufficient molecular weights could be obtained, having high glass transition temperatures (Tgs), high thermal stabilities, as well as lower flammability depending on the diamines incorporated. The char residues showed much difference among each other. Interestingly, one sample containing an ether group in the backbone exhibited a honeycomb-like char morphology, associated with a high degree of graphitization.

Enhanced flame retardancy of polypropylene by melamine-modified graphene oxide

Graphene oxide (GO) is modified by melamine (MA) via the strong π–π interactions, hydrogen bonding, and electrostatic attraction. PP composites are prepared by melt compounding method, and GO/functionalized graphene oxide (FGO) is in situ thermally reduced during the processing. The results of scanning electron microscopy and transmission electron microscopy indicate that FGO nanosheets are homogeneously dispersed in polymer matrix with intercalation and exfoliation microstructure. The FGO/PP nanocomposite exhibits higher thermal stability and flame retardant property than those of the GO counterpart. During the thermal decomposition, the intercalated MA is condensed to graphitic carbon nitride (g-C3N4) in the confined micro-zone created by GO nanosheets. This in situ formed g-C3N4 provides a protective layer to graphene and enhances its barrier effect. The heat release rate and the escape of volatile degradation products are reduced in the FGO-based nanocomposites.

Click-chemistry approach for graphene modification: effective reinforcement of UV-curable functionalized graphene/polyurethane acrylate nanocomposites

This work presents an effective method of preparing graphene reinforced UV-curable materials. Octamercaptopropyl polyhedral oligomeric silsesquioxane (OMP-POSS) functionalized reduced graphene oxide (FRGO) was prepared through a thiol–ene click approach and the FRGO/polyurethane acrylate (PUA) nanocomposite was fabricated by UV irradiation technology. The results of transmission electron microscopy and X-ray photoelectron spectroscopy indicated that OMP-POSS was successfully grafted onto the surface of graphene nanosheets. Thermal and mechanical properties were investigated by thermogravimetric analysis and dynamic mechanical analysis, respectively. The initial degradation temperature, storage modulus at −65 °C and glass transition temperature of FRGO/PUA1.0 nanocomposite were remarkably improved by 12 °C, 57.8% and 10 °C, respectively, compared to those of neat PUA. Those significant enhancements were attributed to the good dispersion of the nanofiller and the strong interfacial interactions between FRGO and PUA matrix.

Thermal and flame retardant properties of transparent UV-curing epoxy acrylate coatings with POSS-based phosphonate acrylate

A novel branched phosphonate acrylate monomer (BPA) containing phosphorus and polyhedral oligomeric silsesquioxanes (POSS) was successfully synthesized via thiol Michael addition of tri(acryloyloxyethyl) phosphate with octamercaptopropyl POSS, and then incorporated into epoxy acrylate (EA) resins in different ratios using ultraviolet curing technology. The structure of BPA was confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance. The effects of BPA on the thermal stability, combustion performance, degradation process and transparency of EA were investigated. The modified EA (MEA) retained a high transparency and exhibited significantly enhanced flame retardancy, as evidenced by the increased limiting oxygen index values and greatly reduced peak heat release rate. The thermal properties of MEA indicated that the presence of BPA promoted the degradation of the EA matrix and produced additional char residues. The thermal degradation processes of the MEA were further investigated by real time FTIR. The char structure of MEA, investigated by Raman spectra, revealed that the addition of BPA increased the ratios of graphitized carbon in residual chars, thus enhancing the thermal stability of MEA.

Synergistic Effects of Nanoporous Nickel Phosphates VSB-1 on an Intumescent Flame-Retardant Low-Density Polyethylene (LDPE) System

Nanoporous nickel phosphates VSB-1 was synthesized by hydrothermal method, and its structure was characterized by X-ray diffraction (XRD), thermogravimetric analyses (TGA) and high resolution transmission electron microscopy (HRTEM). The flame retardancy and thermal behaviour of intumescent flame retardants (IFR) with and without VSB-1 for low-density polyethylene (LDPE) were evaluated by LOI, UL-94 burning test, TGA and cone calorimeter test. With the addition of 2 wt% VSB-1 to LDPE/IFR systems, the LOI value increases from 28.7 to 31, and UL-94 rating raises from V-1 rating to V-0 rating. The results of cone calorimeter show that heat release rate (HRR) peak decrease substantially from 511 KW/m2 to 407 KW/m2 with 2 wt% VSB-1 in LDPE/IFR systems. The scanning electron microscopy (SEM) indicates the quality of char forming of LDPE/IFR/ VSB-1 is superior to that of LDPE/IFR.

Investigation of a combination of novel polyphosphoramide and boron-containing compounds on the thermal and flame-retardant properties of polystyrene

A novel phosphorus, nitrogen-containing compound, poly(4, 4′-diaminodiphenyl methane phenyl dichlorophosphate) (PDMPD) with high thermal stability was synthesized. The PDMPD was then incorporated into polystyrene (PS) to be used as halogen-free flame retardant. Moreover, small amounts of two boron-containing compounds, Zinc borate (ZnB) and boron phosphate (BP) were combined with PDMPD,to explore effective flame-retardant formulations for PS. The flammability and the thermal properties of the composites were evaluated using limiting oxygen index (LOI) test, microscale combustion calorimeter (MCC) and thermogravimetric analysis (TGA) respectively. A Fourier transform infrared (FTIR) spectroscopy coupled with a thermogravimetric analyzer (TG-IR) was also used to study the gas phase from the degradation of PS composites. Furthermore, the char residues of the samples were investigated by scanning electron microscopy (SEM) and FTIR. The results showed that the incorporation of PDMPD can significantly decrease the flammability of virgin PS, and enhance the thermal stability at high temperature region, in both nitrogen and air atmosphere. A combination of PDMPD with small amounts of boron compounds can further decrease the flammability.

Synergistic Effect of Novel Synergists–Transition Metal Ion-incorporated Nickel Phosphates with Intumescent Flame Retardants in Polypropylene

The two kinds of transition metal ion-incorporated nickel phosphates (TMIVSB-1) were synthesized by the hydrothermal method. The flame retardancy and thermal behavior of intumescent flame retardants (IFR), with and without TMIVSB-1 for PP, were investigated by LOI, UL-94 test, thermogravimetric analyses (TGA) and cone calorimetry. TMIVSB-1 can obviously improve the flame retardant behavior of IFR systems according to the results of LOI values and UL-94 test. The results of LOI show that 2 wt% TMIVSB-1 can increase the LOI value by 3–5 unit compared with that of PP/IFR composite. The UL-94 test shows that PP with 20% IFR burns and has no rating, but the addition of a small content 2 wt% of TMIVSB-1 with 18 wt% of IFR can reach a UL-94 V-0 rating. TGA results show that the thermal stability of PP/IFR/TMIVSB-1 increases obviously more than that of PP/IFR when the temperature is above 265°C. From cone calorimetry results, it can be observed that the HRR peaks are not obviously decreased, but the burning time of PP/IFR/FeVSB-1 (351s) and PP/IFR/ZnVSB-1 (380s) is obviously prolonged compared with that of PP/IFR (303s). The real time FTIR spectra (RTFTIR) demonstrates that the addition of TMIVSB-1 further staves the decomposition of the PP composites. The scanning electron microscopy (SEM) indicates the quality of char forming of PP/IFR/ TMIVSB-1 is superior to that of PP/IFR.

Preparation of layered graphitic carbon nitride/montmorillonite nanohybrids for improving thermal stability of sodium alginate nanocomposites

Graphitic carbon nitride (g-C3N4)/montmorillonite (Na-MMT) nanohybrids were successfully fabricated by a facile mixing strategy and then introduced into a sodium alginate host to prepare nanocomposites with different loading levels using a casting technique. The introduction of 4.0 wt% nanohybrids led to the maximal improvement by ca. 149 °C in thermal stability. The improvement of the thermal stability was due to the reason that the mutual intercalation weakened the interlayered interaction of g-C3N4 nanosheets or Na-MMT sheets and enhanced the physical barrier effect that retarded the permeation of heat and the escape of volatile products. This work may provide an approach for exploiting g-C3N4 based materials.