Unsaturated polyester resins modified with phosphorus-containing groups: Effects on thermal properties and flammability

A novel reactive phosphorus-containing monomer [1-oxo-2,6,7-trioxa-1- phosphabicyclo-[2.2.2]octane-methyl diallyl phosphate, PDAP] was synthesized, and various amounts of PDAP were combined with unsaturated polyester by radical bulk polymerization. The resulting flame-retardant unsaturated polyester resin (FR-UPR) samples were investigated by thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC), and limiting oxygen index (LOI) tests. Due to the relatively high phosphorus content of PDAP (18.2 wt%), incorporation of this monomer into unsaturated polyester resin (UPR) led to a marked decrease in the heat release capacity (HRC), the total heat release (THR), an increase in the LOI and the char yield upon combustion. In order to elaborate the interactions between the UPR and PDAP in degradation, differences between the experimental and theoretical mass losses of a FR-UPR sample were evaluated. Furthermore, thermogravimetry-Fourier transform infrared (TG-FTIR) and real-time Fourier transform infrared (RTIR) spectroscopy were employed to investigate the degradation behavior of UPRs, providing insight into the degradation mechanism.     

New phosphorus- and nitrogen-containing poly(methyl methacrylate)-based copolymer

Journal of Thermal Analysis and Calorimetry - Pure poly(methyl methacrylate) (PMMA) always exhibits high flammability and low thermal stability. To address that, a novel reactive comonomer...     

Maximally resonant polygonal systems

A benzenoid system G is k-resonant if any set F of no more than k disjoint hexagons is a resonant pattern, i.e, G−F has a perfect matching. In 1990’s M. Zheng constructed the 3-resonant benzenoid systems and showed that they are maximally resonant, that is, they are k-resonant for all k≥1. Recently, the equivalence of 3-resonance and maximal resonance has been shown to be valid also for coronoid systems, carbon nanotubes, polyhexes in tori and Klein bottles, and fullerene graphs. So our main problem is to investigate the extent of graphs possessing this interesting property. In this paper, by replacing the above hexagons with even faces, we define k-resonance of graphs in surfaces, possibly with boundary, in a unified way. Some exceptions exist. For plane polygonal systems tessellated with polygons of even size at least six such that all inner vertices have the same degree three and the others have degree two or three, we show that such 3-resonant polygonal systems are indeed maximally resonant. They can be constructed by gluing and lapping operations on three types of basic graphs.     

Highly Contorted 1,2,5‐Thiadiazole‐Fused Aromatics for Solution‐Processed Field‐Effect Transistors: Synthesis and Properties

A straightforward strategy has been used to construct 1,2,5‐thiadiazole‐fused 12‐ring π systems through twofold Stille coupling and subsequent cyclodehydrogenation by utilizing the building blocks of naphthodithiophene and 5,6‐substituted benzo[b]‐2,1,3‐thiadidazole. Molecules 1 a and 1 b , which exhibit highly contorted π surfaces, show a butterfly‐shaped conformation according to DFT calculations. Within the molecules, a plane‐to‐plane angle of 44.8° was found. UV/Vis absorption, thermogravimetric analysis, differential scanning calorimetry, and cyclic voltammetry (CV) were used to study their physical properties. Strong intermolecular interactions of the nonplanar molecules were also observed by concentration‐dependent ¹H NMR spectroscopy measurements and thin‐film XRD characterization. The low‐lying LUMO and high‐lying HOMO levels of the molecules are ?3.73 and ?5.48 eV, respectively, as estimated from CV measurements; this indicates their potential as semiconducting materials for solution‐processed organic field‐effect transistors (OFETS). A field‐effect hole mobility of up to 0.035 cm² V^?1 s^?1, a threshold voltage of 6.98 V, and a current on/off ratio of 8.65×10⁵ in air for 1 a have been demonstrated with the top‐contact bottom‐gate field‐effect transistor device structures; this represents an important step toward the solution‐processed OFET application of contorted aromatics.     

The influence of melamine phosphate modified MoS2 on the thermal and flammability of poly(butylene succinate) composites

This work reported a facile fabrication method to modify molybdenum disulfide (MoS₂) nanosheets with common flame retardant melamine phosphate (MAP) and then were incorporated into poly(butylene succinate) by melt blending method with the purpose of improving the thermal and flame retardancy properties. MAP modified MoS₂ nanosheets dispersed well in poly(butylene succinate) composites with intercalated structure. The incorporation of MAP modified MoS₂ nanosheets led to an increase of thermal degradation temperature and char formation as well as reduction of the peak heat release rate. Copyright © 2016 John Wiley & Sons, Ltd.     

2-resonance of plane bipartite graphs and its applications to boron-nitrogen fullerenes

A set H of disjoint faces of a plane bipartite graph G is a resonant pattern if G has a perfect matching M such that the boundary of each face in H is an M-alternating cycle. An elementary result was obtained [Discrete Appl. Math. 105 (2000) 291-311]: a plane bipartite graph is 1-extendable if and only if every face forms a resonant pattern. In this paper we show that for a 2-extendable plane bipartite graph, any pair of disjoint faces form a resonant pattern, and the converse does not necessarily hold. As an application, we show that all boron-nitrogen (B-N) fullerene graphs are 2-resonant, and construct all the 3-resonant B-N fullerene graphs, which are all k-resonant for any positive integer k. Here a B-N fullerene graph is a plane cubic graph with only square and hexagonal faces, and a B-N fullerene graph is k-resonant if any disjoint faces form a resonant pattern. Finally, the cell polynomials of 3-resonant B-N fullerene graphs are computed.     

On maximal resonance of polyomino graphs

A polyomino graph is a finite plane 2-connected bipartite graph every interior face of which is bounded by a regular square of side length one. Let k be a positive integer, a polyomino graph G is k-resonant if the deletion of any i ≤ k vertex-disjoint squares from G results in a graph either having perfect matchings or being empty. If graph G is k-resonant for any integer k ≥ 1, then it is called maximally resonant. All maximally resonant polyomino graphs are characterized in this work. As a result, the least integer k such that a k-resonant polyomino graph is maximally resonant is determined.     

Combined effect of transition metal phosphide (MxPy,M = Ni,Co, and Cu) and intumescent flame retardant system on polypropylene

In this paper, three typical transition metal phosphide nanocrystallines (M_xP_y, M = Ni, Co, and Cu) were synthesized by a novel hydrothermal method, and their structures were characterized by X‐ray diffraction and transmission electron microscopy. Then they were used as synergistic agents with intumescent flame retardant (IFR) to improve the fire safety of polypropylene (PP). Thermogravimetry analysis (TGA) results indicated that the introduction of these synergists could improve the thermal stability and char yields of the PP/IFR system. The addition of 2 wt.% Ni₁₂P₅ and Co₂P increased the limiting oxygen index values of the PP/IFR system significantly from 28% to 36% and 34%, respectively, and the system could reach V‐0 rating. The cone calorimeter test results revealed that the combination of transition metal phosphide nanocrystallines and IFR system could result in excellent flame retardancy. The incorporation of these synergists into IFR led to a remarkable influence on charring of PP composites as revealed by TGA and cone data. The morphological structure of char residue proved that the addition of transition metal phosphide nanocrystallines was capable of forming a compact and homogeneous char on the surface, which turned out to be of most importance for the flame retardancy. Thermogravimetric analysis/infrared spectrometry results indicated that the flame retardant mechanism of PP/IFR/M_xP_y (M = Ni, Co, and Cu) system was in the condensed phase rather than in the gas phase. Copyright © 2014 John Wiley & Sons, Ltd.     

Sol–gel synthesis and enhanced properties of a novel transparent PMMA based organic–inorganic hybrid containing phosphorus,nitrogen and silicon

A novel flame-retardant silane containing phosphorus and nitrogen, tetramethyl(3-(triethoxysilyl)propylazanediyl) bis(methylene) diphosphonate (TMSAP), is firstly synthesized and then incorporated into poly(methyl methacrylate) (PMMA) matrix through sol–gel method to produce organic–inorganic hybrids. The chemical structure of TMSAP was confirmed by Fourier transform infrared spectra, ¹H nuclear magnetic resonance (NMR) and ³¹P NMR spectra. The hybrids obtained maintain relatively high transparency, and exhibit a significant improvement in thermal properties, mechanical performance and flame retardancy when compared to pure PMMA, including increased glass transition temperature (T _g ) by 11.4 °C, increased onset thermal degradation temperature (T_0.1) by 82.6 °C, increased half thermal degradation temperature (T_0.5) by 42.0 °C, increased hardness, increased limited oxygen index and decreased heat release rate. Morphological studies of hybrids by scanning electron microscopy (SEM) and ²⁹Si MAS NMR suggest that cross-linked silica network is formed in the hybrids and the inorganic silica particles are distributed well in the polymer matrix. Thermal degradation behaviors investigated by thermogravimetric analysis and char structure analysis studied by SEM and X-ray photoelectron spectroscopy demonstrate the catalytic charring function of TMSAP, and synergistic effect between phosphorus, nitrogen and silicon element. The formation of network structure, homogeneous distribution of silica and the char formation during degradation play key roles in these property enhancements. Detailed mechanisms for these enhancements are proposed.     

逻辑斯谛方程中参数的估计

在本文中，用逐次加密搜索和回归分析相结合的方法讨论逻辑斯谛方程的参数选优，用此方法，参考文献［１］中的曲线拟合结果得到了明显的改进．