Water absorption rates and mechanical properties of material extrusion-printed continuous carbon fiber-reinforced nylon composites

Material extrusion (ME) is considered as an effective and economic method to process continuous carbon fiber (CCF)-reinforced polymer composites with complicated structures. In this investigation, water absorption tests and tensile tests were conducted on ME-printed CCF-reinforced polymer composites under hydrothermal conditions. The purpose is to meet the growing need of CCF-reinforced polymer composites for high-humidity and high-heat aerospace applications. In order to achieve optimal comprehensive performance, both the L16 (45) orthogonal array method and the fuzzy reasoning algorithm were employed to carry out multi-objective optimization of four selected input variables, including layup angle, nozzle temperature, fiber filling density, and layer thickness. Experimental results show that the comprehensive performance of composites obtained by inputting data into the fuzzy reasoning system was greater than that obtained from orthogonal test results. Specifically, the optimized input variables are 0° layup angle, 260 °C nozzle temperature, 80% fiber filling rate, and 0.6 mm layer thickness

Quantitative determination of zidovudine diaryl phosphate triester pro-drugs in rat plasma by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry

A rapid, simple, and sensitive high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) method was developed and validated for quantitative analysis of 3'-azido-3'-deoxythyrmidine (zidovudine, AZT) diaryl phosphate triester pro-drugs, in rat plasma using 2',3'-dideoxy-2'3'-didehydrothymidine (d4T) as internal standard (IS). The analytes were extracted from rat plasma with methanol after protein precipitation. The compounds were separated by HPLC with gradient elution (on a Shim-pack VP-ODS C-18 analytical column using a mobile phase of methanol/10 mM ammonium acetate). All the analytes were detected in positive ion mode using multiple reaction monitoring (MRM). The method was validated and the specificity, linearity, lower limit of quantitation (LLOQ), precision, accuracy, recoveries and stability were determined. LLOQs were 10 ng mL(-1) for M1, M2, M3, M4. and M5, respectively. Cori-elation coefficient (r)values for the linear range of 10-10,000 ng mL(-1) were greater than 0.999 for all the analytes. The intra-day and inter-day precision and accuracy were higher than 7.13%. The relative and absolute recovery was above 72% and no matrix effects were observed for all the analytes. This validated method provides a modern, rapid, and robust procedure for the pharmacokinetic studies of the pro-drugs after intravenous administration to rats. Some important results of AZT diaryl phosphate triester pro-drugs concerning chemical effect on pharmacokinetic performance are also studied. (C) 2008 Elsevier B.V. All rights reserved.Major Program of National Natural Science Foundation of China [20732004]; People's Republic of China [2006DFA43030