Jianxin Mu

Preparation and properties of epoxy resin composites containing hexaphenoxycyclotriphosphazene

Hexaphenoxycyclotriphosphazene (HPCTP) was synthesized by a nucleophilic substitution reaction between hexachlorocyclotriphosphazene and phenol. The chemical structure of HPCTP was then characterized by Fourier transform infrared spectroscopy as well as 1H and 31P nuclear magnetic resonance spectroscopy. The synthesized HPCTP was incorporated into the diglycidyl ether of bisphenol A to prepare epoxy resin (EP) composites using 4,4′-diamino diphenylmethane as curing agent. The thermal and flame-retardant properties of cured samples were investigated by differential scanning calorimetry, thermogravimetric analysis, UL-94 vertical burning test, and cone calorimetry. Evaluation of thermal properties demonstrated that the resulting composites achieved high thermal stability with high char yields. The UL-94 V-0 rating was easily achieved with the addition of HPCTP, and the heat release intensity simultaneously decreased. Results of scanning electron microscopy and energy-dispersive x-ray spectroscopy confirmed that HPCTP can enhance the thermal stability and flame retardancy of epoxy resin.

Effect of hexaphenoxycyclotriphosphazene combined with octapropylglycidylether polyhedral oligomeric silsesquioxane on thermal stability and flame retardancy of epoxy resin

A novel phosphazene-based compound called hexaphenoxycyclotriphosphazene (HPCTP) was synthesized and characterized by Fourier transform infrared spectroscopy as well as proton and phosphorus nuclear magnetic resonance spectroscopies. Epoxy (EP) resin composites containing HPCTP and octapropylglycidylether polyhedral oligomeric silsesquioxane (OGPOSS) were prepared using 4,4′-diamino diphenylmethane as curing agent. Differential scanning calorimetry, thermogravimetric analysis, UL 94 vertical burning test, and cone calorimetry test were used to assess thermal stability and flame retardancy of the composites. Evaluation of thermal properties demonstrated that the resulting composites achieved less thermal stability compared with control EP resin but possessed high char yields at high temperatures. It indicated that both HPCTP and OGPOSS could induce the formation of intumescent char layer that retarded the degradation and combustion process of EP resin. The peak heat release rate of EP resin composite containing 15 wt% HPCTP was 61% less than that of control EP resin. Meanwhile, other flame-retardant parameters were also improved. Results of scanning electron microscopy and energy-dispersive x-ray spectroscopy of residual chars confirmed that both HPCTP and OGPOSS can enhance thermal stability and flame retardancy of EP resin.

Octasilsesquioxane-reinforced TMBP epoxy nanocomposites: Characterization of thermal, flame-retardant, and morphological properties

Organic–inorganic nanocomposites comprising epoxy resins and polyhedral oligomeric silsesquioxanes (POSS) were prepared via in situ polymerization of 3,3′,5,5′-tetramethyl-4,4′-biphenyl diglycidyl epoxy resins and 4,4′-diaminodiphenylsulfone. The thermal, fire-retardant, and morphological properties of the nanocomposites were studied using thermogravimetric analysis (TGA), thermogravimetry-Fourier transform infrared (TG-FTIR) spectroscopy, microscale combustion calorimeter (MCC), limiting oxygen index (LOI), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The peak heat release rate and the total heat release were significantly reduced with the incorporation of POSS into the epoxy networks, based on the MCC results. Moreover, the LOI value slightly increased with the increase in POSS content. Further, SEM and XPS were used to explore the char residues of the pure epoxy resin and POSS-containing system. The introduction of POSS was found to lead to the formation of an inert layer on the surface of the materials, which protects the internal structure from decomposition.

A comparative structure–property study of polyphosphazene micro-nano spheres

Novel fluorinated cross-linked polyphosphazene micro-nano spheres have been prepared by precipitation polymerization of hexachlorocyclotriphosphazene (HCCP) monomer. The influence of molecular structure on the morphology of polyphosphazene micro-nano spheres was investigated by SEM and TEM. The micro-nano spheres were also characterized by Fourier transforms infrared, X-ray photoelectron spectroscopy and thermo gravimetric analysis. The results indicate that the 5xa0% thermal degradation temperature is 366xa0°C. It was found that a silicon wafer dip-coated with thus prepared micro-nano spheres has a water contact angle as high as 137°xa0±xa01.5°. Furthermore, the effects of the concentration of HCCP and ultrasonic power on the morphology were also discussed.

Morphology, thermal properties, and fire behavior of epoxy resin nanocomposites containing octaammonium polyhedral oligomeric silsesquioxane-modified montmorillonite

A series of epoxy resin (EP) nanocomposites containing octaammonium polyhedral oligomeric silsesquioxane-modified montmorillonite (OAPOSS-MMT) was prepared via in situ polymerization using 4,4′-diaminodiphenyl sulfone as the curing agent. X-Ray diffraction and transmission electron microscopy were used to characterize the morphology of the resulting nanocomposites. Characterization results indicated the formation of intercalated and exfoliated structures. Thermogravimetric analysis (TGA) was performed to study the thermal properties of epoxy nanocomposites. Analysis results revealed that OAPOSS-MMT improved the thermal stability of EP matrix. TGA coupled with Fourier transform infrared spectrometry was used to detect pyrolytic gases. The gas species produced by epoxy nanocomposites were the same as those of control EP. A cone calorimeter was used to evaluate the flame retardancy of epoxy nanocomposites containing different concentrations of OAPOSS-MMT. Results showed that OAPOSS-MMT improved the flame retardancy of EP to some extent. The enhanced thermal oxidative stability was also confirmed by the data obtained through x-ray photoelectron spectroscopy.

Preparation of a novel pH-sensitive hydrogel based on acrylic acid and polyhedral oligomeric silsesquioxane for controlled drug release of theophylline

Hydrogels based on pH-sensitive polymers are of great interest as potential biomaterials for the controlled delivery of drug molecules. In this study, a novel pH-sensitive copolymer hydrogel based on acrylic acid (AA) monomer by free-radical solution polymerization were synthesized with organic–inorganic cross-linking agent of octavinyl polyhedral oligomeric silsesquioxane (OVPOSS). And its properties were compared with conventional hydrogels using N,N′-methylenebisacrylamide (MBA) as cross-linking agent. The copolymers were characterized by Fourier transform infrared spectra and differential scanning calorimetry. The morphology after swelling was presented by scanning electron microscopy. Swelling behaviors in different pH and potential applications in controlled drug delivery of the hydrogels were also examined. The results showed that both hydrogels were pH sensitive. However, as the addition of OVPOSS limited the movement of the molecular chain segment, the swelling ratio and the drug-release rate of theophylline in SGF decreased obviously when using OVPOSS as cross-linking agent, comparing with P(MBA-co-AA) hydrogels. The results in this study suggested that P(OVPOSS-co-AA) could serve as potential candidate for theophylline drug delivery.

Synthesis and thermal stability of hybrid polymers using UV photopolymerization based on polyhedral oligomeric silsesquioxanes

A series of hybrid polymers based on methacrylphenyl polyhedral oligomeric silsesquioxanes (MA-POSS) and methylmethacrylate (MMA) were rapidly synthesized via UV photopolymerization through a (2,4,6-trimethylbenzoyl)diphenylphosphine oxide-initiated reaction. The structure and morphology of hybrid polymers were characterized via Fourier transform infrared spectroscopy, proton nuclear magnetic spectroscopy, gel permeation chromatography, X-ray diffraction, transmission electron microscopy and scanning electron microscopy, which confirmed that the MA-POSS cage could be successfully incorporated into the polymethylmethacrylate (PMMA) chain. The obtained hybrid polymers had no obvious aggregation of MA-POSS. It can be concluded that MA-POSS were well-dispersed in the hybrid polymers. The thermal properties of PMMA–POSS hybrid polymers were investigated through differential scanning calorimetry and thermogravimetric analysis. Results show that the incorporation of POSS cage results in the enhancement of the glass transition temperature and the decomposition temperature of hybrid polymers as compared with PMMA polymers without MA-POSS.

Preparation and properties of novel fluorinated cross-linked polyphosphazene micro-nano spheres

Novel fluorinated cross-linked polyphosphazene micro-nano spheres with controllable particle size ranging from 0.57 to 4.33 µm were prepared by precipitation polymerization of hexachlorocyclotriphosphazene (HCCP) monomer. The formation of the non-porous micro-nano spheres was found to obey an oligomeric species-absorbing mechanism. The micro-nano spheres were characterized by scanning electron microscopy, Fourier transform infrared spectrometry, energy-dispersive X-ray spectroscopy, nuclear magnetic resonance imaging and X-ray diffraction. No glass-transition temperature of the spheres was observed and the onset of the thermal-degradation temperature was found to be 366 °C. It was found that a silicon wafer dip-coated with thus prepared micro-nano spheres had a water contact angle as high as 137 ± 1.5°. By changing such experimental conditions, as concentration of HCCP, temperature and ultrasonic power, the particle size of the polymeric micro-nano spheres can be controlled.

Synthesis and properties of novel poly(ether ether ketone) copolymers with (3,5-ditrifluoromethyl)phenyl and (4-phenoxy)phenyl side groups

A new nonfluorinated bisphenol monomer 2-(4-phenoxyphenyl)-1,4-diphenol was prepared via a four-step synthesis process. A series of poly(ether ether ketone) copolymers (6FPOP-PEEKs) were derived from 4,4′-difluorobenzophenone via a nucleophilic aromatic substitution polycondensation with various molar feed ratios of bisphenol monomer, 2-(4-phenoxyphenyl)-1,4-diphenol to (3,5-ditrifluoromethyl)phenylhydroquinone. The molecular weights (Mn values), polydispersities and T g values of 6FPOP-PEEKs increase as the molar feed ratio of 6FPH/(6FPH+POPH) increases. These 6FPOP-PEEKs show very high thermal stability. At a wavelength of 1550 nm, the refractive indices of the 6FPOP-PEEKs films are in the range of 1.5992–1.6396 and birefringences are in the range of 0.0034–0.0043. The near-infrared spectra show that the 6FPOP-PEEK films have small light absorption at the telecommunication wavelengths of 1300 and 1550 nm.