Advanced Materials Research Vols. 87-88

Abstract: Microfluidic chip has bright application prospect in the field of chemical and biological analysis. PMMA is the best material for microfluidic chip fabrication because of its low cost, prominent electrochemical properties and biological compatibility. In this work, a triple-channel microfluidic chip was designed; a nickel mold insert with microstructure was fabricated by UV-LIGA technology, and then the injection mold was designed and fabricated. The change in cross-section dimensions of microchannel was chosen as evaluating indicator, and micro-injection molding experiments were carried out. Then the influence of process parameters on cross-section dimensions of microchannel was observed with microscope. Experiment results demonstrated that substrate and cover plate could be manufactured in a single injection molding process by "1+1" type mold, and the manufacturing cycle was reduced to less than 20s, so production efficiency was greatly enhanced. Best combination of process parameters was obtained when mold temperature was 80°C, melt temperature was 250°C and injection rate was 297mm/s. Thereby, high quality substrate and cover plate could be manufactured efficiently.

Abstract: Crosslinked amphoteric starches (CAS) with quaternary ammonium cationic and carboxymethyl anionic groups were prepared by a microwave radiation method. Their adsorption behavior for Cr(VI) was investigated. The results showed that high the degree of substitution (DS) of modified starch was favorable to the synthesis by the microwave heating and crosslinked amphoteric starches prepared with higher the adsorption capacity than by the drying reaction. The adsorption capacity increases with the increasing cationic groups and decreased with increasing degree of substitution of anionic groups. The adsorption capacity was found to follow the Langmuir isotherm.

Abstract: Microfibrillated cellulose (short for MFC) has rapidly advanced due to its unique nano-order-unit web-like network structure and such special properties as extremely high strength, large specific surface area and high aspect ratio. In the present paper, the processing technology and the research progress of the preparation methods of MFC with mechanical and it combined with enzymatic treatment are briefly reviewed, then the four main challenges about preparation of MFC are figured out. In the last section, the direction of this research field is also highlighted.

Abstract: The improved mixing extruding machine is made up of mixer and unconventional double-cone screw extruder, which has both the excellent mixing capabilities and the continuous extruding characters. Its extruding part is an unconventional double-cone screw extruder, which are integrated double merits about double cone screw and single screw with strong feeding ability, stable extrusion pressure, supplementary mixing and more excellent quality of products. The pair of rotors and screws can be stepless speed regulating, which ensures match between the feeding capacity of the internal mixer and the extrusion output as well as the perfect mixing property. The mathematical model of the continuous mixing extruding can provide guidance for the actual production. The limitation of the batch-type production is overcome, and fulfilling the manufacture from the raw materials of polyblends to finished product in one machine.

Abstract: The impact of fine content of carbon black pellets on rubber mixing process and reasons for carbon black pellet degradation during pneumatic conveying process has been investigated and analyzed. The influential factors of carbon black degradation are introduced. It is identified and concluded that specific surface area of carbon black, size of carbon black pellets, parameters of pressure in conveying, conveying modes, materials of pipelines and conveying distance are major factors in the impact of degradation of carbon black. The conclusion is confirmed by the results of tests. The measures to reduce carbon black pellet fine content are proposed.

Abstract: With the increasing development of polymeric materials, it becomes important for research on mechanical properties of polymeric materials under large deformation conditions. To know displacement distributions in the polymeric structures could help us to better understand the deformation characteristics of polymeric structures in fracture analysis. In this paper, an experimental digital moiré method for the in-plane deformation measurement in a sample of transparent polymeric material, which is a non-contact method for full-field, large deformation and real-time measurement, is presented. The measurement principles and the basic procedures of the method are explained in detail. In order to demonstrate this method, a cross grating is generated and put into a transparent polymeric specimen. The subsequent fringe and displacement analysis is carried out using the method developed by the authors.

Abstract: Upilex-s [poly(biphenyl dianhydride-p-phenylene diamine)] polyimide have been widely employed in the area of flexible electronics. For its potential application on fabricating flexible solar cells, the optical properties of Upilex-s are measured in this paper. Intrinsic hydrogenated amorphous silicon layers are then deposited on Upilex-s substrates at temperatures 100°C and 180°C by plasma enhanced chemical vapor deposition (PECVD) system. As an comparison, intrinsic a-Si:H layers are also fabricated on glass substrate of Corning2000. Both layers on flexible and rigid substrates are thoroughly characterized by activation energy and dark conductivity measurements. It can be concluded that the intrinsic layer on Upilex-s has favorable properties and could be a competitive candidate as substrate materials of flexible solar cells.

Abstract: In this work, the biodegradable poly(lactic acid) (PLA)/organic-montmorillonite (O-MMT) nanocomposites were successfully prepared by the in situ polymerization intercalation process of D,L-lactide with organically-modified montmorillonite which was first treated by Cu cations and second treated by n-hexadecyl trimethylammonium bromide (CTAB) cations. O-MMT was characterized by FT-IR and XRD, the results showed that Cu cations and CTAB cations had been inserted to the interlayer of MMT, and the interlayer spacing of CTAB-Cu-MMT (O-MMT) increased by 1.829nm. The biodegradable PLA/O-MMT nanocomposites were characterized by XRD, SEM, FT-IR, TG, and the results showed that silicate layers were intercalated into the PLA matrix and the biodegradable PLA/O-MMT nanocomposites were of two different types: intercalated nanocomposites and exfoliated nanocomposites. This new nanocomposites frequently exhibited remarkable improvements when compared with the neat PLA matrix. Improvements could include increased heat distortion temperature, an increase in the biodegradability rate of biodegradable polymers.

Abstract: The structure, thermal behavior and flame retardant properties of polypropylene (PP) nanocomposites treated with complex flame retardants composed of layered double hydroxides (LDH) and ammonium polyphosphate (APP)/pentaerythritol (PER) intumescent flame retardant systems have been investigated by XRD, TEM, LOI, UL-94, and TGA analysis. The results showed that introduction of LDH nanofillers into the samples can obtain good flame retardant synergistic effects with APP/PER additives at appropriate LDH loadings. Such synergism between LDH and APP/PER in PP matrix can be explained by a proposed condensed phase flame retardant mechanism. And based on this study, different types of modified PP products were developed in a ten-thousand-ton scale to be used for the automobile industries, such as car bumpers and dashboards.

Abstract: Polyacrylamide (PAM) nanofibers was spun by electrospinning. In order to increase the molecular weight of the PAM, It has been cross linked by Glutaraldehyde solution. By means of scanning electron microscopy (SEM), the effect of electrospun technological parameters on the fibers’ morphology were researched. The parameters include the concentration of PAM spinning solution, the applied voltage and tip-collector distance (TCD). The PAM nanofibers of uniform thickness with the fibers’ diameter distribution of 80 ~ 160nm were got under the conditions as followers: the concentration of 16 wt.%, applied voltage of 23 kV, the TCD of 13cm.