Poly（lactic acid） （PLA） composites with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide （DOPO） and DOPO- containing polyhedral oligomeric silsesquioxane （DOPO-POSS） were prepared via melting extrusion and i...Poly（lactic acid） （PLA） composites with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide （DOPO） and DOPO- containing polyhedral oligomeric silsesquioxane （DOPO-POSS） were prepared via melting extrusion and injection molding. The crystallization, mechanical, and flame-retardant properties of PLA/DOPO and PLA/DOPO-POSS were investigated by differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, tensile testing, thermogravimetric analysis （TGA）, limiting oxygen index （LOI）, and cone calorimeter test. The DSC results showed that the DOPO added could act as a plasticizer as reflected by lower glass transition temperature and inhibited crystallization of part of the PLA; the DOPO-POSS acted like a filler in the PLA matrix and slightly improved the crystallinity of the PLA matrix. The XRD and DSC analyses indicated that the PLA composites by cold molding injection were amorphous, and the PLA composites following a heat treatment in an oven at 120 ℃for 30 min achieved crystallinity. All the PLA and its composites after heat treatment had improved mechanical properties. The thermogravimetric analysis （TGA） tests showed that the PLA, DOPO and DOPO-POSS decomposed separately in the PLA/DOPO and PLA/DOPO-POSS, respectively. The cone calorimeter tests offered clear evidence that addition of the DOPO-POSS resulted in an evident reduction of 25% for the peak of heat release rate （p-HRR）. It was also confirmed that the crystalline flame-retardant PLA composites after heat treatment had better flame retardant properties than the amorphous PLA composites prepared by the cold molding.展开更多
Polystyrene （PS）/triphenyl phosphate （TPP） composites were prepared by both suspension polymerization and melt extrusion, and a comparative study of the flame retardance and mechanical properties was carried out. ...Polystyrene （PS）/triphenyl phosphate （TPP） composites were prepared by both suspension polymerization and melt extrusion, and a comparative study of the flame retardance and mechanical properties was carried out. The results showed that suspension polymerization was a better technique than melt extrusion for obtaining good dispersity of the PS/TPP composite. The TPP nanoparticles, which were approximately 50 nm in size, were homogenously and uniformly dispersed in the PS matrix by suspension polymerization in one-step. However, the PS/TPP composite was partially agglomerated, exhibiting irregularly shaped micron-scale particles as a result of melt extrusion. In contrast to the melt extrusion, the limited oxygen index （LOI） of the PS/TPP nanocomposite by suspension polymerization increased to 22.6% from 21.8%, and time to ignition （TTI） increased by 12.3%, the peak heat release rate （PHRR） decreased by 8.5%, and the total heat release （THR） decreased by 11.0%. The mechanical properties of the PS/TPP nanocomposite by suspension polymerization also increased. The tensile strength, elongation at break, and flexural strength increased by 36.4%, 8.5%, and 108%, respectively.展开更多
To explore the application of click chemistry in the field of elastomer materials, propargyl-terminated ethylene oxide-tetrahydrofuran copolymer （PTP（E-co-T）） was prepared from hydroxyl-terminated ethylene oxide-t...To explore the application of click chemistry in the field of elastomer materials, propargyl-terminated ethylene oxide-tetrahydrofuran copolymer （PTP（E-co-T）） was prepared from hydroxyl-terminated ethylene oxide-tetrahydrofuran copolymer （P（E-co-T）） by end-etherisation modification. FTIR and ^13C-NMR results indicate that P（E-co-T）-terminated hydroxyl was etherified thoroughly, yielding the target product PTP（E-co-T）, and the content of terminated alkynyl of PTP（E-co-T） was evaluated to be 0.428 mmol.g^-l. Using a polyazide compound as a cross-linker, polytriazole elastomers with various functional molar ratio （R） values were prepared from PTP（E-co-T） by virtue of the CuAAC reaction. Mechanical property tests indicate that with the increase in R, the modulus E and stress Orb of the polytriazole elastomers first increase and subsequently decrease, whereas the strain first decreases and later increases. The mechanical properties of the polytriazole elastomers show a parabolic dependence on the R value. Near the stoichiometric ratio, E and Orb show maxima and the strain εb shows a minimum. Swelling tests demonstrate that the apparent molecular weight of polytriazole elastomer strands also first decreases and subsequently increases. At the stoichiometric ratio, the network structure possesses strands with a minimum apparent molecular weight and a maximum apparent density. Dynamic mechanical analysis reveals that the polytriazole elastomers presented damping peaks at approximately -64℃, corresponding to the glass transition of copolyether strands, and the elastomer exhibited the lowest dissipation factor tanδ at the stoichiometric ratio. Thermal analysis suggests that the weight-loss process of the polytriazole elastomer is characteristic of one-step decomposition, and the elastomer begins to decompose from polyether strands, not triazole groups.展开更多
A comprehensive study on the efficient one-pot synthesis of polyhedral octaphenylsilsesquioxane (OPS) is reported via the hydrolytic condensation of phenyltrimethoxysilane (PTMS) in the presence of basic catalyst to i...A comprehensive study on the efficient one-pot synthesis of polyhedral octaphenylsilsesquioxane (OPS) is reported via the hydrolytic condensation of phenyltrimethoxysilane (PTMS) in the presence of basic catalyst to investigate the specific synthesis mechanism.The synthetic reactions are monitored with real time infrared (RTIR) spectroscopy.Then RTIR coupled with 29Si nuclear magnetic resonance spectroscopy (NMR) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) are used to monitor the reactions and identify the intermediary species during the reaction.The rapid hydrolysis of PTMS is detected by RTIR.Contrary to previous reports,the ladder-like structured species are identified as intermediates during the reaction process.it is suggested that formation of caged T8OPS is realized through the chain break and rearrangement of the ladder-like phenyltrimethoxysilanes.Accordingly,a scheme from hydrolysis of the PTMS to formation of the OPS is provided.展开更多
文摘Poly（lactic acid） （PLA） composites with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide （DOPO） and DOPO- containing polyhedral oligomeric silsesquioxane （DOPO-POSS） were prepared via melting extrusion and injection molding. The crystallization, mechanical, and flame-retardant properties of PLA/DOPO and PLA/DOPO-POSS were investigated by differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, tensile testing, thermogravimetric analysis （TGA）, limiting oxygen index （LOI）, and cone calorimeter test. The DSC results showed that the DOPO added could act as a plasticizer as reflected by lower glass transition temperature and inhibited crystallization of part of the PLA; the DOPO-POSS acted like a filler in the PLA matrix and slightly improved the crystallinity of the PLA matrix. The XRD and DSC analyses indicated that the PLA composites by cold molding injection were amorphous, and the PLA composites following a heat treatment in an oven at 120 ℃for 30 min achieved crystallinity. All the PLA and its composites after heat treatment had improved mechanical properties. The thermogravimetric analysis （TGA） tests showed that the PLA, DOPO and DOPO-POSS decomposed separately in the PLA/DOPO and PLA/DOPO-POSS, respectively. The cone calorimeter tests offered clear evidence that addition of the DOPO-POSS resulted in an evident reduction of 25% for the peak of heat release rate （p-HRR）. It was also confirmed that the crystalline flame-retardant PLA composites after heat treatment had better flame retardant properties than the amorphous PLA composites prepared by the cold molding.
文摘Polystyrene （PS）/triphenyl phosphate （TPP） composites were prepared by both suspension polymerization and melt extrusion, and a comparative study of the flame retardance and mechanical properties was carried out. The results showed that suspension polymerization was a better technique than melt extrusion for obtaining good dispersity of the PS/TPP composite. The TPP nanoparticles, which were approximately 50 nm in size, were homogenously and uniformly dispersed in the PS matrix by suspension polymerization in one-step. However, the PS/TPP composite was partially agglomerated, exhibiting irregularly shaped micron-scale particles as a result of melt extrusion. In contrast to the melt extrusion, the limited oxygen index （LOI） of the PS/TPP nanocomposite by suspension polymerization increased to 22.6% from 21.8%, and time to ignition （TTI） increased by 12.3%, the peak heat release rate （PHRR） decreased by 8.5%, and the total heat release （THR） decreased by 11.0%. The mechanical properties of the PS/TPP nanocomposite by suspension polymerization also increased. The tensile strength, elongation at break, and flexural strength increased by 36.4%, 8.5%, and 108%, respectively.
基金financially supported by the National Natural Science Foundation of China(No.51473022)
文摘To explore the application of click chemistry in the field of elastomer materials, propargyl-terminated ethylene oxide-tetrahydrofuran copolymer （PTP（E-co-T）） was prepared from hydroxyl-terminated ethylene oxide-tetrahydrofuran copolymer （P（E-co-T）） by end-etherisation modification. FTIR and ^13C-NMR results indicate that P（E-co-T）-terminated hydroxyl was etherified thoroughly, yielding the target product PTP（E-co-T）, and the content of terminated alkynyl of PTP（E-co-T） was evaluated to be 0.428 mmol.g^-l. Using a polyazide compound as a cross-linker, polytriazole elastomers with various functional molar ratio （R） values were prepared from PTP（E-co-T） by virtue of the CuAAC reaction. Mechanical property tests indicate that with the increase in R, the modulus E and stress Orb of the polytriazole elastomers first increase and subsequently decrease, whereas the strain first decreases and later increases. The mechanical properties of the polytriazole elastomers show a parabolic dependence on the R value. Near the stoichiometric ratio, E and Orb show maxima and the strain εb shows a minimum. Swelling tests demonstrate that the apparent molecular weight of polytriazole elastomer strands also first decreases and subsequently increases. At the stoichiometric ratio, the network structure possesses strands with a minimum apparent molecular weight and a maximum apparent density. Dynamic mechanical analysis reveals that the polytriazole elastomers presented damping peaks at approximately -64℃, corresponding to the glass transition of copolyether strands, and the elastomer exhibited the lowest dissipation factor tanδ at the stoichiometric ratio. Thermal analysis suggests that the weight-loss process of the polytriazole elastomer is characteristic of one-step decomposition, and the elastomer begins to decompose from polyether strands, not triazole groups.
基金This work was funded by grants from the China Postdoctoral Science Foundation funded project(Grant No.2018M631353)National Science Foundation for Young Scholars of China(Grant No.51803008).
文摘A comprehensive study on the efficient one-pot synthesis of polyhedral octaphenylsilsesquioxane (OPS) is reported via the hydrolytic condensation of phenyltrimethoxysilane (PTMS) in the presence of basic catalyst to investigate the specific synthesis mechanism.The synthetic reactions are monitored with real time infrared (RTIR) spectroscopy.Then RTIR coupled with 29Si nuclear magnetic resonance spectroscopy (NMR) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) are used to monitor the reactions and identify the intermediary species during the reaction.The rapid hydrolysis of PTMS is detected by RTIR.Contrary to previous reports,the ladder-like structured species are identified as intermediates during the reaction process.it is suggested that formation of caged T8OPS is realized through the chain break and rearrangement of the ladder-like phenyltrimethoxysilanes.Accordingly,a scheme from hydrolysis of the PTMS to formation of the OPS is provided.
