Poly(lactic acid)-aspirin microspheres prepared via the traditional and improved solvent evaporation methods and its application performances

Drug-loaded microspheres are significant for the development of modern pharmaceutical products. It is well known that the taken of aspirin for long-term increases the risk of serious gastrointestinal complications, therefore a controllable delivery of aspirin is of importance to lighten those side effects. In this work, poly(lactic acid)(PLA) was chosen as the carrier to prepare PLA-aspirin microspheres by using the traditional and the improved solvent evaporation methods. It was found that no matter which experimental condition was, the encapsulation efficiency of aspirin was higher by using the improved method than that of the traditional method. Specifically, when the concentration of polyvinyl alcohol = 1%(mass),the polymer concentration = 1:20, the oil/water rate = 1:2.5, PLA-aspirin microspheres were obtained via the improved method with a high yield of 82.83%(mass) and an encapsulation efficiency of 44.09%. PLAaspirin microspheres were then prepared continuously using the improved method, which further enhanced the encapsulation efficiency to 54.56%. Approximate 85% aspirin released from microspheres within 7 days. Obvious degradation which was represented by reduction on hardness was observed by soaking microspheres in PBS for 60 days. This work is of interest because it provides a continuous route to prepare PLA-aspirin microspheres continuously with a high drug encapsulation efficiency.

Synthesis of melamine-formaldehyde microcapsules containing oil-based fragrances via intermediate polyacrylate bridging layers

A general and versatile strategy to prepare melamine-formaldehyde(MF)microcapsules encapsulating oil-based fragrances by combining solvent evaporation and in situ polymerization was proposed in this work.The oil-based fragrance was pre-encapsulated by an inner polyacrylate membrane via solvent evaporation,followed by in situ polymerization of MF precondensates as an outer shell.The polyacrylate membrane is used as an intermediate bridging layer to stabilize the oil-based fragrance,and to provide driving forces for in situ polymerization of MF precondensates through electrostatic attractions between carboxyl groups and ammonium ions.It was demonstrated that MF microcapsules containing clove oil were prepared successfully.The amount and the composition of the intermediate polyacrylate bridging layer were critical.Smooth and sphere-shaped MF-clove oil microcapsules were prepared when the weight ratio of polyacrylate to clove oil was over 60 wt%and the concentration of acrylic acid(AA)increased to 10 wt%in polyacrylate.In addition,MF microcapsules containing sunflower oil and hexyl salicylate were prepared by using this method.The work suggests that this new approach can be potentially used to encapsulate various core materials,tuning the shell properties of microcapsules such as thickness,mechanical strength and release properties.

An efficient preparation of porous polymeric microspheres by solvent evaporation in foam phase

This paper reports an efficient method of preparing porous polymeric microspheres by solvent evaporation in foam phase,in which phase separation between polymer and porogen occurs in foam phase instead of that in water phase by using the traditional solvent eva poration method.The method provides outstanding features,including being time-saving,of high-yield and able for continuous production,in which formation of porous polymeric microspheres finished within 3 min with a high production yield up to approximate 95 wt% and the process was able to be developed into a continuous process for production of porous polymeric microspheres.It was also universal to non-crosslinked polymers since the method is a development on the traditional emulsion solvent evaporation method.The new method is efficient and can be used potentially on the industrial scale for continuous production of porous polymeric microsphere s.

China＇s Anti-dumping Problems and Mitigation through Regional Trade Agreements

The present paper explores the opportunities for China＇s regional trade agreement （RTA） initiatives to mitigate its anti-dumping problems. The paper highlights the severity and discriminatory nature of China＇s anti-dumping problems. The high concentration of the share of anti-dumping actions taken by the top 4 and top 8 anti-dumping initiators is noted. Our finding of a weak effect of existing RTAs on mitigating China ＇s anti-dumping problems supports the argument that China could become more active in mitigating anti-dumping problems through RTA negotiations. An RTA can include a higher level of openness in exchange for an improvement in regional anti-dumping provisions. Case studies on RTAs involving the EU, the USA and India offer some precedents for offering inducements and modifying regional anti-dumping provisions. The approaches for China may lie in obtaining market economy status from intensive anti-dumping initiators at RTA levels and also altering regional anti-dumping provisions that could be put in place in exchange for some potential concessions.

Characterization and pilot scale test of a fluidized bed two-stage gasification process for the production of clean industrial fuel gas from low-rank coal

To utilize low rank coal efficiently,a fluidized bed two-stage(FBTS)gasification process,mainly consisting of a FB pyrolyzer and a transport FB(TFB)gasifier,has been proposed for the production of clean fuel gas.To verify the feasibility and technical features of this novel gasification technology,a pilot autothermal platform,with a treating capacity of 100 kg/h for coal,was designed and built up.By adopting a kind of lignite from Inner Mongolia,the running state and fuel gas quality were compared systematically under typical operational conditions.The results show that by keeping the reaction temperatures of pyrolyzer and gasifier at around 840
C and 1000
C,respectively,the corresponding tar content in fuel gas at the outlets of pyrolyzer and gasifier were 1127 mg/Nm3 and 365 mg/Nm3,reaching a high tar removal efficiency.Under the stable operation state,the volume fractions of CO,H2,CH4 and CO2 in fuel gas were 14.4%,8.3%,3.4%and 11.3%,respectively,and the corresponding higher heating value of fuel gas was about 1100 kcal/Nm3.Compared with the tar from pyrolyzer,the heavy oil fraction in tar from gasifier reduced significantly,while the light oil components increased sharply simultaneously,showing significant effect of catalytic reforming by hot char bed on tar removal.