Sichuan University

About: Sichuan University is a education organization based out in Chengdu, China. It is known for research contribution in the topics: Catalysis & Population. The organization has 107623 authors who have published 102844 publications receiving 1612131 citations. The organization is also known as: Sìchuān Dàxué.

Ammonium polyphosphate chemically-modified with ethanolamine as an efficient intumescent flame retardant for polypropylene

Abstract: Ammonium polyphosphate (APP) is not an efficient flame retardant for polypropylene (PP) when it is used alone. In order to improve its flame-retardant efficiency, ethanolamine (ETA) was used to chemically modify APP via ion exchange reaction. The resulting ethanolamine-modified ammonium polyphosphate (ETA-APP) was alone applied to flame retard PP, the limiting oxygen index (LOI) value could reach 35.0% and the vertical burning test (UL-94) could pass the V-0 rating at a loading of 35 wt% ETA-APP. Moreover, cone calorimeter (CC) test results showed that the heat release rate (HRR), the total heat release (THR), the mass loss rate (MLR), the smoke production rate (SPR) and the total smoke production (TSP) of PP/35 wt% ETA-APP composite largely decreased, for example, by 77.2%, 88.5% and 77.9% for THR, TSP and the fire growth rate (FGR), respectively, compared with PP containing an equal amount of APP. In addition, the residual char of PP/35 wt% ETA-APP increased by 195.6% compared with that of PP/35 wt% APP. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the flame retardant mechanism of ETA-APP. It was confirmed that the formation of P–O–C and P–N–C structures, resulting from the incorporation of ETA could greatly improve the stability of intumescent char layer and consequently lead to the much better flame retardancy of ETA-APP than that of unmodified APP. Experimental results demonstrated that the prepared ETA-APP acted not only as the acid source and blowing source as efficient as unmodified APP, but also as an excellent charring agent beyond the unmodified APP.

Preparation and in vitro investigation of chitosan/nano-hydroxyapatite composite used as bone substitute materials.

Abstract: Chitosan/nano-hydroxyapatite composites with different weight ratios were prepared through a co-precipitation method using Ca(OH)2, H3PO4 and chitosan as starting materials. The properties of these composites were characterized by means of TEM, IR, XRD, burn-out test and universal matertial test machine. Additionally, in vitro tests were also conducted to investigate the biodegradability and bioactivity of the composite. The results showed that the HA synthesized here was poorly crystalline carbonated nanometer crystals and dispersed uniformly in chitosan phase and there is no phase-separation between the two phases. Because of the interactions between chitosan and n-HA, the mechanical properties of these composites were improved, and the maximum value of the compressive strength was measured about 120 MPa corresponding to the chitosan/n-HA composite with a weight ratio of 30/70. The specimens made of 30/70 chitosan/n-HA composite exhibit high biodegradability and bioactivity when being immersed in SBF solutions. The composite is appropriate to being used as scaffold materials for bone tissue engineering. © Springer Science + Business Media, Inc.

Highly Thermoconductive, Thermostable, and Super-Flexible Film by Engineering 1D Rigid Rod-Like Aramid Nanofiber/2D Boron Nitride Nanosheets.

Abstract: Polymer-based thermal management materials have many irreplaceable advantages not found in metals or ceramics, such as easy processing, low density, and excellent flexibility. However, their limited thermal conductivity and unsatisfactory resistance to elevated temperatures ( 100 MPa, 450 °C) enable effective thermal management for microelectrodes operating at temperatures beyond 200 °C.