Shibin Nie

Thermal degradation and flame retardancy of microencapsulated ammonium polyphosphate in rigid polyurethane foam

Abstract Microencapsulated ammonium polyphosphate MFAPP or VMFAPP with shell of melamine–formaldehyde or poly (vinyl alcohol)–melamine–formaldehyde resin was prepared by in situ polymerization, respectively. The flame-retardant performance of rigid polyurethane foam (PU) containing MFAPP or VMFAPP was analyzed by limiting oxygen index and UL-94 test. Thermal degradation behaviors of PUAPP, PUMFAPP and PUVMFAPP were studied using TG and TG–FTIR. Above results indicated that VMFAPP and MFAPP have better water resistance and flame retardancy compared with ammonium polyphosphate (APP) in PU composites. Flame-retardant properties of PUMFAPP and PUVMFAPP composites were rarely changed after hot water treatment. Due to better compatibility and the presence of active groups on the surface of APP, microencapsulation demonstrated a positive effect on the mechanical property of PU composites.

Study of the Synergistic Effect of Nanoporous Nickel Phosphates on Novel Intumescent Flame Retardant Polypropylene Composites

A char forming agent (CFA) and silica-gel microencapsulated ammonium polyphosphate (Si-MCAPP) were selected to form novel intumescent flame retardant system to prepare flame retardant polypropylene (PP) composites, and then the influences of nanoporous nickel phosphates (NiP) on the thermal and flame retardant properties of flame retardant PP composites were studied by the real time FTIR (RTFTIR) spectra, limited oxygen index (LOI) test, and the scanning electron microscopy. RTFTIR shows the addition of NiP can improve the thermal stability of flame retardant PP composites. LOI test shows LOI value is increased with the increase of the content of NiP, and the optimized concentration of NiP is 1.0%. Furthermore, smoke toxicity of the novel flame retardant PP composites was studied by mice experiment. The upper limit of the no death smoke concentration of the composite is 12.37 mg/L.

Thermal decomposition of polypropylene by tunable synchrotron vacuum ultraviolet photoionization mass spectrometry

The application of synchrotron vacuum ultraviolet (VUV) photoionization combined with molecular-beam mass spectrometry, also called synchrotron VUV photoionization mass spectrometry (SVUV-PIMS), in the research of the thermal decomposition of polypropylene (PP) was studied, and some main pyrolysis products formed at different photon energies have been identified. Using SVUV-PIMS, some isomers can be distinguished, which are much helpful for further understanding of the thermal decomposition of PP.

The growth mechanism of multi-wall carbon nanotubes produced by pyrolyzing polypropylene composite

The growth mechanism of multi-wall carbon nanotubes (MWCNTs) produced by pyrolyzing polypropylene composite were studied. Scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy (HRTEM) were employed to demonstrate that the charred residue formed from PP/organically modified montmorillonite/nickel oxide (Ni2O3) composite contains an abundance of MWCNTs with almost homogeneous distribution of diameters. X-ray diffraction and HRTEM reveals that a real active site for the growth of MWCNTs is Ni not Ni2O3. Meanwhile, the growth mechanism described as the yarmulke mechanism is proposed based on the experimental analysis.

Investigation on pyrolysis of intumescent flame-retardant polypropylene (PP) composites based on synchrotron vacuum ultraviolet photoionization combined with molecular-beam mass spectrometry

The pyrolysis of intumescent flame-retardant polypropylene (PP) composites was studied by synchrotron vacuum ultraviolet photoionization combined with molecular-beam mass spectrometry (SVUV-PIMS). Pyrolytic products of intumescent flame-retardant PP composite formed at certain temperature have been identified by the measurement of photoionization mass spectra at different photon energies. By using SVUV-PIMS, some isomers were identified. Meanwhile, the effect of high-efficient flame-retardant synergist–nanoporous nickel phosphate on pyrolytic products of intumescent flame-retardant PP composite was also studied. By analyzing the pyrolysis of the intumescent flame-retardant PP composites with or without the flame-retardant synergist, the synergistic flame-retardant mechanism was discussed as the condensed-phase flame-retardant mechanism not gas flame-retardant mechanism as expected. The studies in this work are much helpful for further understanding the flame-retardant mechanism of intumescent flame-retardant PP composites.

Mechanical Properties, Morphologies and Thermal Decomposition Kinetics of Poly(lactic acid) Toughened by Waste Rubber Powder

Abstract To improve the impact resistance and reduce the product cost, poly(lactic acid) (PLA) blends containing varying mass fraction of waste rubber powder (WRP) were fabricated via melt compounding. The effects of WRP contents on the mechanical properties, morphologies and thermal stabilities of PLA/WRP blends were investigated. Mechanical tests showed that WRP could increase the ductilities of PLA, leading to the significant improvements in the impact toughness and elongation at break. In contrast, the tensile strength was just heightened slightly, while elastic modulus declined gradually. Scanning electron microscopy observations indicated that well bonded interfacial morphologies were formed between PLA and WRP. From the results of thermo gravimetric analysis, WRP decreased the onset and peak decomposition temperatures of PLA phase and increased the char contents of samples significantly. Average activation energies of samples were increased first and then decreased with increasing WRP. Finally, theoretical lifetimes of PLA/WRP blends were also estimated.

Fabrication and Characterization of Poly(lactic acid) Biocomposites Reinforced by Calcium Sulfate Whisker

The biodegradable poly(lactic acid) (PLA) composites filled with calcium sulfate whisker (CSW) were fabricated via melt-blending and subsequent injection molding. Surface organification of γ-aminopropyltriethoxysilane (APTES) on CSW was applied to accelerate the wettability of PLA to CSW. The mechanical properties, morphological structures, crystallization behaviors and thermal stabilities of PLA/CSW composites were investigated in detail. Results showed that modification of APTES changed the surface morphologies and element compositions, helping to form the well bonded interfaces. By adding CSW, the elastic modulus of PLA/CSW composites presented a sustained increment, while tensile strength, elongation at break and impact toughness were increased first and then decreased. The presence of CSW impeded the melt-crystallization but accelerated the cold-crystallization process. On the whole, the actual crystallinity for the composites was suppressed except for the case with 20% CSW. The thermal stability was enhanced by CSW as expected, and all the samples showed the exact same reaction order (n = 1) according to Carrasco method. Nevertheless, the activation energies were declined, indicating CSW was in favor of thermal decomposition of PLA phases. Finally, it was interestingly found that CSW could improve the comprehensive properties of PLA without deteriorating the processibility.

Thermoplastic Blends of PP and Waste Rubber Powder: Effects of Compatibilizer on Tensile Properties, Thermal Behavior and Decomposition Kinetics

Abstract To improve the performances of waste rubber powder filled polypropylene (PP/WRP) blends, WRP was modified by γ-aminopropyltriethoxysilane (APTES) via mechano-chemical method, and then maleic anhydride (MAH) grafted PP (mPP) and MAH grafted ethylene-α-octene copolymer (mEOC) were chosen as the interfacial compatibilizers. The PP/WRP blends were prepared by melt-compounding and compression, and their morphological structures, tensile properties and thermal behavior were investigated carefully. Results showed that modification of APTES decreased the surface energy of WRP and facilitated its compatibility to PP. Both mPP and mEOC could further enhance their interfacial bonding and mPP was superior to mEOC in increasing the tensile strength and elastic modulus. Thermal analysis revealed relative lower melting temperature and crystallinity but higher activation energy for PLA/WRP blends in comparison to pristine PP.

Morphology Influence of Nanoporous Nickel Phosphate on Intumescent Flame Retardant Polypropylene Composites

Abstract The morphology of nanoporous nickel phosphate (NP) has a close relationship with its properties, so in this work NP with needle-like and mushroom-like shape was synthesized. Then NP with needle-like and mushroom-like shape was applied in intumescent flame retardant polypropylene (PP) composites. With the addition of suitable content of NP, both mushroom-like and needle-like NP can improve the combustion and thermal properties of intumescent flame retardant PP composites. Needle-like NP shows a better thermal ant flame retardant synergist effect with intumescent flame retardants compared to mushroom-like NP. However, mushroom-like NP shows a better effect on smoke suppression. With the addition of suitable content of needle-like NP, the peak heat release rate of flame retardant PP composite decreases by 68.2 % comparing with that of the pure PP, and decreases by 23.8 % comparing with that of flame retardant PP composite without NP. The maximum weight loss temperature of PP composites can be increased from 408 °C to 485 °C with the addition of needle-like NP. Furthermore, the pyrolysis products of flame retardant PP composite with needle-like NP were investigated. From the research, it provides a further understanding of the influence on synergic effects in intumescent flame retardant systems.