Xinlong Wang

Versatile nanostructured processing strategy for bone grafting nanocomposites based on collagen fibrillogenesis

Abstract Strong bone-like nanocomposites of collagen type I and hydroxyapatite were prepared by coupling the in situ synthesis, hybrid gel formation and subsequent dehydration consolidation. The calcium phosphate synthesis was initiated at 4°C in the concentrated collagen monomeric solutions. Under this condition collagen molecules inhibited the calcium phosphate uncontrollably rapid growth and the predominant collagen fibril aggregation was retarded. Elevating temperature induced collagen fibrillogenesis leading to the formation of elastic hybrid gels. The dehydration consolidation of the elastic gels gave rise to strong nanocomposites. The mechanical properties and bone-like characteristics of the prepared nanocomposites were explicated. The in situ formation of a hybrid gel together with its facile processing capability suggests the versatility of this biomimetic strategy either in fabricating different structural forms (films, scaffolds and monoliths) of bone grafts or in further inclusion of other biosubstance into the nanocomposites.

Structural characteristics of poly(vinyl alcohol)-calcium carbonate composites prepared by sequential method

Abstract Composites of poly(vinyl alcohol) (PVA) and calcium carbonate (CaCO3) were prepared by a sequential method involving first in situ synthesis of CaCO3 in PVA solution, then physical crosslinking of synthetic suspension and subsequently washing of resultant elastic gel followed by consolidation. The phase and composition, mechanical properties and microstructure of the composites and possible molecular interactions between both components were evaluated. X-ray diffraction analysis revealed that calcium carbonate was mainly composed of aragonite and calcite. Compression tests confirmed the composites prepared by this sequential method had good mechanical properties and that the compressive strength of the composites increased with higher content of calcium carbonate. PVA formed an interconnected network and needle-like CaCO3 crystals together with some fine grains were well compatible with PVA. In situ synthesis induced a spectral shift of hydroxyl groups and C–O bonds of PVA and the suppression of the characteristic adsorption of calcite was also observed, according to Fourier transform infrared spectroscopy measurements.

Thermal studies on Li(CH 3 CN) 4 PF 6 and Li(C 4 H 10 O 2 ) 2 PF 6 complexes by the TG–DTA–MS and DSC

Li(CH3CN)4PF6 and Li(C4H10O2)2PF6 complexes are important intermediates created in the synthetic process of high-purity LiPF6 electrolyte via transformation method. The thermal decomposition behavior of as-prepared Li(CH3CN)4PF6 and Li(C4H10O2)2PF6 crystals in pure nitrogen atmosphere has been studied by means of thermogravimetric–differential thermal analysis coupled with mass spectrometry (TG–DTA–MS). Results suggest that the decomposition of Li(CH3CN)4PF6 complex can be roughly divided into a three-stage process, and CH3CN is the primary gas product of decomposition process for Li(CH3CN)4PF6 in open Al2O3 pans. Further insight into Li(C4H10O2)2PF6 crystal indicates that it undergoes a similar decomposition process to Li(CH3CN)4PF6. Accordingly, the detailed deduction of the thermal decomposition mechanism formulas for them was presented in this paper. Besides, the thermal behaviors of Li(CH3CN)4PF6 and Li(C4H10O2)2PF6 complexes in hermetic aluminum pan were also investigated by differential scanning calorimetry (DSC).

Study on in-situ polymerization of PANI/APP and its application in HDPE

An organo-inorganic composite material PANI–APP based on conjugated polyaniline (PANI) and ammonium polyphosphate (APP) was prepared by performing in situ polymerization of aniline with ammonium persulfate in the presence of APP, and then it was doped by P-toluene sulfonic acid (PTSA). PANIPTSA–APP was possessed of flame retardancy and electrical conductivity and it was introduced into high density polyethylene for preparing PE/PANIPTSA–APP composites. The structural and morphological properties of PANIPTSA–APP were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction (XRD) and other analyses. The results showed that PANI doped with PTSA was prepared. The electrical conductivity and flame retardancy of PE/PANIPTSA–APP composites were investigated by measuring the electrical resistance and scanning electron microscope, photomicrography, limiting oxygen index (LOI), thermal gravity (TG) and XRD, respectively. Experimental results showed that the LOI of composite reached to 29.2% and the volume resistivity dropped to 6.80xa0×xa0108xa0Ωxa0cm−1 when the amount of PANIPTSA–APP was 30%. The thermal degradation mechanism of PANIPTSA–APP was explored and we found out that PANIPTSA coupled with APP had a positive synergistic effect on the flame retardancy.