Hongdian Lu

In situ polymerization of graphene nanosheets and polyurethane with enhanced mechanical and thermal properties

Polyurethane (PU) composites reinforced with graphene nanosheets (GNSs) were prepared by in situpolymerization. Graphene nanosheets, which were derived from chemically reduced graphite oxide (GO) nanosheets, were characterized by solid-state 13C MAS NMR, XRD and FTIR. A morphological study showed that, due to the formation of chemical bonds, the GNS was dispersed well in the PU matrix. With the incorporation of 2.0 wt% of GNSs, the tensile strength and storage modulus of the PU increased by 239% and 202%, respectively. The nanocomposites displayed high electrical conductivity, and good thermal stability of PU was also achieved. The facile and rapid technique presented here will provide an effective and promising method of preparing graphene-based polymer composites.

Flammability Performance and Char Behavior of Poly(vinyl alcohol)-Zirconium Phosphate-Montmorillonite Composites

Flammability performance and the microstructure of chars from poly(vinyl alcohol) (PVA) with α-type zirconium phosphate (α-ZrP) and montmorillonite (MMT) hybrid composites and multilayer composite were elucidated with microscale combustion calorimetry (MCC) and scanning electron microscopy (SEM). MCC revealed that the combination of α-ZrP and MMT did not impart synergistic effect in improving flame retardancy to PVA/ZrP/MMT hybrid composites, while multilayer composite showed better flame-resistant properties than hybrid composite. SEM demonstrated that the minimal loading levels of MMT in PVA/ZrP/MMT composites obstructed the development of intumescent chars in hybrid composites, but on-site mechanically reinforced the intumescent char in multilayer composite.

Effects of Charring Agents on the Thermal and Flammability Properties of Intumescent Flame-Retardant HDPE-based Clay Nanocomposites

Intumescent flame-retardant (IFR) high-density polyethylene, poly[ethylene-co-(vinyl acetate)], and organically-modified clay nanocomposites consisting of ammonium polyphosphate (APP) and other charring agents, as well as the nanocomposites pentaerythritol (PER), polyamide-6 (PA), and PA/OMT were investigated. Their thermal and flammability properties have been characterized by thermogravimetric analyses, cone calorimetry, a limiting oxygen index, and the UL-94 test. Results show that the PER-contained sample exhibits different thermal and flammability behaviors from the samples containing polymer charring agents. The difference is postulated to be responsible for the formation of various intumescent structures and their changes in response to heightened temperatures.

Carbon nanotube reinforced polylactide/basalt fiber composites containing aluminium hypophosphite: thermal degradation, flame retardancy and mechanical properties

This work aims to develop modified carbon nanotube (m-CNT) reinforced polylactide/basalt fiber (PLA/BF) composites with enhanced thermal stability, flame retardancy, and mechanical properties using aluminium hypophosphite (AHP). Morphological observations revealed that both the m-CNT and AHP particles were homogeneously dispersed in the PLA/BF composites. The improvement of thermal stability and tensile strength/modulus strongly depended on the uniform dispersion of the mixed particles and the interactions between m-CNT and PLA. The presence of AHP and m-CNT significantly reduced the peak heat release rate of PLA/BF in microscale combustion calorimetery testing. The combustion behaviors were evaluated by limiting oxygen index (LOI), Underwriters Laboratories 94 (UL 94), and cone calorimetery. For PLA/BF containing 19 wt% AHP and 1 wt% m-CNT, it achieved a V-0 classification in UL 94 testing with a high LOI (31%). Additionally, the peak heat release rate and total heat release were respectively reduced by around 64% and 27% in comparison with PLA/BF. The residue analysis showed that many microspheres formed by the sufficient reaction between AHP and PLA under the physical barrier effect of m-CNT migrated to or accumulated on the surface of residues. The compact char layer composed of these microspheres could effectively reduce the heat conduction of basalt fibers and cut off the mass transfer path resulting in the weakening of the wick effect resulting in the significant improvement of the composites.

Study on Flame-Retardant LLDPE/EPDM Thermoplastic Elastomers with Magnesium Hydroxide Sulfate Hydrate Whiskers

The mechanical properties and flame retardancy of linear low-density polyethylene/ethylene-propylene-diene terpolymer thermoplastic elastomers (TPEs) containing magnesium hydroxide sulfate hydrate (MHSH) whiskers and their corresponding un-vulcanized blends (UVBs) were evaluated using static tensile measurements, cone calorimetry and limiting oxygen index (LOI) tests. TPEs exhibited better fire-resistant properties in reducing peak heat release rate and improving LOI values to UVBs. Scanning electron microscopy (SEM) images showed that TPE sample left a more compact char after cone test. Results from tensile tests confirmed that TPEs had superior mechanical properties to UVBs due to the better compatibility between MHSH whiskers and polymer matrix.

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.

Study on Preparation and Properties of Silane-crosslinked Polyethylene/ Magnesium Hydroxide/ Montmorillonite Nanocomposites:

Silane-crosslinked polyethylene/magnesium hydroxide/organomontmorillonite nanocomposite is prepared from linear low density polyethylene (LLDPE), vinyltrimethoxysilane, magnesium hydroxide (MH), and organomontmorillonite (OMT). The morphology is characterized by the X-ray diffraction and high resolution electron microscopy. It is indicated that the intercalated morphology is formed in the polymer matrix. The mechanical properties, thermal stability, flammability, and crystallization are investigated by tensile, limiting oxygen index, cone calorimetry, thermogravimetry, and differential scanning calorimetry experiments. Results indicate that the crosslinked nanocomposite shows lower thermal-oxidative stability and fire safety than the crosslinked LLDPE/MH composite at the same additive level, the reason is postulated to be that the presence of MH and OMT decreases the crosslinking degree and the crosslinking network structure prevents the migration of OMT layers to the surface. *Author to whom correspondence should be addressed. E-mail: yuanhu@ustc.edu.cn JOURNAL OF FIRE SCIENCES, VOL. 26 – November 2008 493 0734-9041/08/06 0493–15

Numerical study of fire spread using the level-set method with large eddy simulation incorporating detailed chemical kinetics gas-phase combustion model

10.00/0 DOI: 10.1177/0734904108092117 SAGE Publications 2008 Los Angeles, London, New Delhi and SingaporeSilane-crosslinked polyethylene/magnesium hydroxide/organomontmorillonite nanocomposite is prepared from linear low density polyethylene (LLDPE), vinyltrimethoxysilane, magnesium hydroxide (MH), and organo-montmorillonite (OMT). The morphology is characterized by the X-ray diffraction and high resolution electron microscopy. It is indicated that the intercalated morphology is formed in the polymer matrix. The mechanical properties, thermal stability, flammability, and crystallization are investigated by tensile, limiting oxygen index, cone calorimetry, thermogravimetry, and differential scanning calorimetry experiments. Results indicate that the crosslinked nanocomposite shows lower thermal-oxidative stability and fire safety than the crosslinked LLDPE/MH composite at the same additive level, the reason is postulated to be that the presence of MH and OMT decreases the crosslinking degree and the crosslinking network structure prevents the migration of OMT layers to the surface.

Comparative Studies on Thermal, Mechanical, and Flame Retardant Properties of PBT Nanocomposites via Different Oxidation State Phosphorus-Containing Agents Modified Amino-CNTs

Abstract A fire code has been developed for the purpose of modelling wildland fires via Large Eddy Simulation (LES) and the use of the level-set approach to track the flame front. Detailed chemical kinetics have been considered via the strained laminar flamelet approach for the combustion process which included the consideration of the yields of toxic volatiles such as CO, CO2 and soot production. Numerical simulations have been validated against an experimental study on the fire spread on a pine needle board under different slope angles. Peak temperatures and occurrence times during the propagation process were predicted with an overall average error of 11% and 3% respectively. This demonstrates that the flaming behaviour could be well predicted under different slope conditions. By incorporating the level set with the gas phase models, information including temperature field, toxic volatiles and soot particle concentrations can be realised in comparison to empirical fire spread models.

Simultaneous enhancements in the mechanical, thermal stability, and flame retardant properties of poly(1,4-butylene terephthalate) nanocomposites with a novel phosphorus–nitrogen-containing polyhedral oligomeric silsesquioxane

High-performance poly(1,4-butylene terephthalate) (PBT) nanocomposites have been developed via the consideration of phosphorus-containing agents and amino-carbon nanotube (A-CNT). One-pot functionalization method has been adopted to prepare functionalized CNTs via the reaction between A-CNT and different oxidation state phosphorus-containing agents, including chlorodiphenylphosphine (DPP-Cl), diphenylphosphinic chloride (DPP(O)-Cl), and diphenyl phosphoryl chloride (DPP(O3)-Cl). These functionalized CNTs, DPP(Ox)-A-CNTs (x = 0, 1, 3), were, respectively, mixed with PBT to obtain the CNT-based polymer nanocomposites through a melt blending method. Scanning electron microscope observations demonstrated that DPP(Ox)-A-CNT nanoadditives were homogeneously distributed within PBT matrix compared to A-CNT. The incorporation of DPP(Ox)-A-CNT improved the thermal stability of PBT. Moreover, PBT/DPP(O3)-A-CNT showed the highest crystallization temperature and tensile strength, due to the superior dispersion and interfacial interactions between DPP(O3)-A-CNT and PBT. PBT/DPP(O)-A-CNT exhibited the best flame retardancy resulting from the excellent carbonization effect. The radicals generated from decomposed polymer were effectively trapped by DPP(O)-A-CNT, leading to the reduction of heat release rate, smoke production rate, carbon dioxide and carbon monoxide release during cone calorimeter tests.