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The influence of alumina (Al2O3) content and diameter on the viscosity characteristics of the alumina/linear low-density polyethylene (Al2O3/LLDPE) composites was discussed. The composites were fabricated by melt mixing with the two-rotor continuous mixer. The equivalent surface average particle diameter ( d ¯ A {\bar{d}}_{\text{A}} ) of Al2O3 was calculated by the scanning electron microscopic (SEM) images of samples. The steady-state and dynamic rheological measurements were used to study the evolution of viscosity parameters. With the Carreau model fitting to the steady-rate rheological data, zero-shear viscosity η 0, time constant λ, and power law index n of composites were obtained. On this basis, an optimized Carreau model was established by studying the changes of these parameter values. The rheological result presented that the parameter values (η 0, λ, and n) were linearly proportional to the filling content of Al2O3 particles for nano-Al2O3/LLDPE composites. However, these parameters were, respectively, related to d ¯ A {\bar{d}}_{\text{A}} , d ¯ A 2 {\bar{d}}_{\text{A}}^{2} , and d ¯ A 3 {\bar{d}}_{\text{A}}^{3} for micron-Al2O3/LLDPE composites.

Highly filled high-density polyethylene/alumina (HDPE/Al2O3) composites were fabricated by melt mixing with direct incorporation of poly(ethylene-co-methacrylic)-based ionomer (EMAA-Na) as an interfacial compatibilizer. SEM and EDX micrographs indicate EMAA-Na interfacial adhesion on the Al2O3 spheres. Under low EMAA-Na content conditions, the FT-IR characterization and an EMAA-Na neutralization degree analysis revealed the priority of the melt neutralization interaction between the acid groups of the ionomer and the Al2O3 spheres in the composite. Under high EMAA-Na content conditions, an AFM phase characterization revealed the formation of an EMAA-Na ionomer spherical domain (∼300 nm) dispersed in an HDPE matrix due to the microphase separation of ionic chains. Capillary and dynamic rheology measurements were also conducted to investigate the phase morphology evolution. The polymeric adhesion on the Al2O3 sphere surfaces contributed to the increase of the melt viscosity and gradual elongation thickening behavior of the composite melts. The formed spherical domain structure of EMAA-Na of the composite melts contributed to the shear thickening, elongation thickening and yield behavior. Three rheology criteria plots indicate large complex formation in the composite melts. The EMAA-Na incorporation in the highly filled HDPE/Al2O3 composite matrix not only improved the strength and toughness performance, with a 27% improvement in the elongation at break (EMAA-Na content 1 wt.%) and 21% improvement in the tensile strength (EMAA-Na content 10 wt.%), but also preserved the good thermal conductivity (∼1.5 W/(m·K)). This study reveals the potential application of the EMAA-Na ionomer to resolve the challenge of the strength and toughness performance degradation in highly filled polymer composites.

The measurement of impurity distribution in the divertor region of tokamaks is key to studying edge impurity transport. Therefore, a space-resolved vacuum-ultraviolet (VUV) spectrometer is designed to measure impurity emission in the divertor region on EAST. For good spectral resolution, an eagle-type VUV spectrometer with 1 m long focal length with spherical holograph grating is used in the system. For light collection, a collimating mirror is installed between the EAST plasma and the VUV spectrometer to extend the observing range to cover the upper divertor region. Two types of detectors, i.e. a back-illuminated charge-coupled device detector and a photomultiplier-tube detector, are adopted for the spectral measurement and high-frequency intensity measurement for feedback control, respectively. The angle between the entrance and exit optical axis is fixed at 15°. The detector can be moved along the exit axis to maintain a good focusing position when the wavelength is scanned by rotating the grating. The profile of impurity emissions is projected through the space-resolved slit, which is set horizontally. The spectrometer is equipped with two gratings with 2400 grooves/mm and 2160 grooves/mm, respectively. The overall aberration of the system is reduced by accurate detector positioning. As a result, the total spectral broadening can be reduced to about 0.013 nm. The simulated performance of the system is found to satisfy the requirement of measurement of impurity emissions from the divertor area of the EAST tokamak.

The chaotic mixing process in a continuous mixer plays an important role and has an essential influence on the performance of prepared materials. To reveal how a polymeric drop experienced the chaotic mixing and give more specific analysis about the chaotic mixing, the morphology development of a single drop was traced and recorded with an on-line visualization system. The drop would undergo elongation deformation, reorientation, and folding process, which were the typical signs of chaotic mixing. The elongation deformation was an important precondition for drop experiencing the reorientation and folding process and mainly existed in the region near the barrier, rotor tip clearance, and wedgelike region. The reorientation and folding process mostly appeared in the region near the rotor flat and interaction window. Besides, the erosion process of the drop was observed at the initial stage under lower rotor rotation speed. The chaotic mixing always held the dominant place in continuous mixer although the rotor rotation speed and drop viscoelasticity were adjusted. In this work, the chaotic mixing in a continuous mixer was dynamically presented. The dynamical results would give a more real and visual understanding of the chaotic mixing.

The deformation-induced crystallization of an isotactic polypropylene (iPP) sheet containing a &beta, nucleating agent was evaluated. The phase transformation of the &beta, modifications was investigated and the crystal morphology was observed at room temperature after stretching at different temperatures. The results showed that the crystallinity increased after solid-state stretching. When the stretching temperature was below the initial crystallization temperature, stretching deformation promoted the orientation of amorphous molecular chains. When the deformation temperature exceeded the crystallization temperature, part of the &beta, modifications underwent a phase transformation process and was stretched into a shish-kebab structure. However, once the stretching temperature was close to the melting point, the &beta, modifications melted and recrystallized, and the shish-kebab structure underwent stress relaxation due to poor thermal stability, transforming into &alpha, modifications. It was revealed that the crystal phase transformation mechanism of the &beta, modifications was based on the orientation of the molecular chains between the adjacent lamellae. In addition, the shish-kebab cylindrite structure played an important role in modifying the tensile and impact properties of the iPP sheet. The tensile and impact strengths increased by as much as 34% and 126%, respectively.

During the &ldquo, slit die extrusion-hot stretching&rdquo, process, highly oriented polyamide 6 (PA6) dispersed phase was produced and retained in the polypropylene (PP) matrix directly. By adjusting the stretching forces, the PA6 spherical phase evolved into the ellipsoid, rod-like microfibril with a decreasing average diameter, then, the PA6 microfibrils broke. Moreover, the effects of the PA6 phases formed in the process of the microfibrillation on PP&rsquo, s crystallization behaviors were studied systematically. As the stretching forces increased, the crystallization ability and orientation degree of PP crystals improved significantly. Differential scanning calorimetry and polarizing optical microscopy confirmed the formation of PP spherulite, fan-shaped lamellae and a transcrystalline layer under the induction of the PA6 phases with different morphology. In the PP/PA6 microfibrilar composites (MFCs), PP crystals showed smaller average size, more crystals and stronger interface adhesion due to more excellent heterogeneous nucleation ability of the PA6 microfibrils, which made contributions to the improvement of the melt elasticity responses and oxygen barrier properties of the PP/PA6 polymer blends.

Spatially arranged polymer brushes provide the essential capability of precisely regulating the surface physicochemical and functional properties of various substrates. A novel and flexible polymer brush patterning methodology, which is based on employing a digital mirror device (DMD)-based light modulation technique to spatiotemporally regulate a surface-initiated photoinduced atom transfer radical polymerization (photo-ATRP) process, is presented. Various characterization techniques confirm that the spatially and/or temporally controlled brush formation results in complex PEG-derived brush patterns in accordance with a customized digital image design. A series of step-and-exposure strategies, including in situ multiple exposure, dynamic multiple exposure and dynamic sequential exposure, are developed to implement spatiotemporal regulation of the photo-ATRP process, leading to complex patterned and gradient brushes featuring binary functionalities, pyramid nanostructures and radial directional chemical gradients. Moreover, tunable and radial directional concentration gradients of various biomacromolecules (e.g., streptavidin) are obtained through preparation of height gradients of azido-functionalized brushes and subsequent orthogonal chemical activation aimed at specific protein immobilization. Finally, a unidirectional concentration gradient of fibronectin, surrounded by non-fouling PEG brushes, is fabricated and applied for human umbilical vein endothelial cell (HUVEC) adhesion experiments, whose preliminary results indicate gradient-dependent cell adhesion behavior in response to the concentration gradient of fibronectin. The presented fabrication technique could be integrated with microfluidic devices for sensors and bio-reactors, paving the way for novel approaches for lab-on-a-chip technologies.

In this work, carbon black (CB)/polyamide 6 (PA6)/polypropylene (PP) microfibrillar composites (MFCs) were fabricated through an extrusion (hot stretching) heat treatment process. The CB-coated conductive PA6 microfibrils with high aspect ratio were in situ generated as a result of the selective accumulation of CB at the interface. At the proper temperature, a 3D entangled conductive structure was constructed in the PP matrix, due to topological entanglement between these conductive microfibrils. This unique conductive structure provided the PP composites with a low electrical conductivity percolation threshold. Moreover, the electromechanical properties of conductive MFCs were investigated for the first time. A great stability, a high sensitivity and a nice reproducibility were achieved simultaneously for CB/PA6/PP MFCs. This work provides a universal and low-cost method for the conductive polymer composites’ (CPCs) fabrication as sensing materials.

Microarray technology holds enormous promise in the development of various fields ranging from tissue engineering, regenerative medicine to high-throughput screening. Here, based on the digital micromirror device (DMD)-based spatiotemporal regulation of surface-initiated photoinduced atom transfer radical polymerization (Photo-ATRP) process, a flexible and versatile methodology was developed to fabricate a hierarchical microarray structure constituted with a homogeneous hyperbranched polyethylene glycol (PEG)-derived brush layer as anti-fouling background and an extension layer of square-grid poly(2-(2-azido-2-methyl-1-oxopropoxy) ethyl methacrylate) (PAMEMA) brushes micropatterns on the silicon substrate. The terminal azido groups on the side chains of PAMEMA brushes provide abundant reactive sites to realize the covalent immobilization of target biomolecules, including RGD peptide, fibronectin, BSA and streptavidin. The TOF-SIMS and fluorescence characterizations demonstrated the feasibility and efficiency of spatially modulating the density of surface-bound biomolecules through regulating the 3D architecture parameters of the PAMEMA brush micropatterns and consequentially the azido chemical functionality. Moreover, culture experiments of human bone-derived marrow stromal cells (BMSCs) and mouse L929 cells were conducted on the obtained hierarchical microarray structure in a high-throughput manner. The presented hierarchical microarray structure holds excellent potential as a high-throughput screening platform, allowing for the parallel assessment of cell-surface interactions.

The microstructure evolution of an isotactic polypropylene (iPP) sheet during solid-state stretching was studied. The transition of the spherulites&mdash, cylindrites was evaluated using in-situ two-dimensional wide-angle and small-angle X-ray scattering methods. The crystallinity of stretched iPP sheets was characterized by differential scanning calorimetry. The crystal morphology was observed by means of scanning electron microscopy. It was found that the differences of crystal microstructure of the iPP sheet depended on the stretching strain, which promoted the orientation of molecular chains. Amorphous molecular chains in the spherulites oriented and formed into a mesophase near the yield point, and the partially ordered mesophase was further stretched to form an oriented cylindrite structure after the yield point. The highest relative content of cylindrites appeared at 15% strain. Notably, as the amorphous phase embedded into the lamellae layer, the crystal size decreased with the increase of strain, which indicated that the crystallinity of the stretched iPP sheet was much higher than that of unstretched iPP sheet. The induced cylindrites structure played a more important role in improving the mechanical properties and heat resistance of iPP sheets. Compared with the unstretched iPP sheets, the tensile strength increased by 28%, the notch impact toughness significantly increased by 78%, and the vicat softening point increased from 104 to 112 &deg, C.

The screw combination of twin-screw extruder affects the filler size in inorganic filler-reinforced polymeric compounds. This article tried to conveniently and precisely model the agglomerate size evolution in modular co-rotating twin-screw extruder. The break-up process of agglomerate was analyzed to obtain the relationship between average deagglomerating energy (M) and agglomerate size, the result presented a mathematic relationship between M and agglomerate size. Numerical simulation study was conducted to consider the effect of kneading blocks (KB) or flight elements (FE) number on dispersion capacity of screw combination. The average deagglomerating energy, calculated based on POLYFLOW simulation, was introduced as major parameter to evaluate the dispersion capacity, which presented a proportional relationship to the KB or FE number. The model was developed by combining the agglomerate break-up process and simulation results. In validation, CaCO3/linear low-density polyethylene (LLDPE) compounds were prepared by modular co-rotating twin-screw extruder with different screw combinations. The optical image analysis showed that CaCO3 agglomerate size decreased with the KB or FE number rising, while it achieved minimum when the KB number was 4. The model was in accordance with the experimental results, and proved to be valid for KB and FE combinations in preparing CaCO3/LLDPE compounds. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45535.