Volume 35, Issue 9

Co-injection molding (CIM) is an advanced technology which was developed to meet quality requirements and to reduce the material cost. Theoretical investigations concerning it are very limited, especially for simultaneous CIM. The interactions of air, skin and core polymer melt in the process are very complex, which makes it more challenging to simulate free surface flows in the mold. Thus, this article presents a mathematical model for it. The extended Pom-Pom (XPP) model is selected to predict the viscoelastic behavior of polymer melt. The free surface is captured by the level set method. The article vividly shows the simultaneous CIM process by means of a visual numerical simulation technique. Both two-dimensional (2D) and 3D examples are presented to validate the model and illustrate its capabilities. The 3D flow behaviors of simultaneous CIM process are hard to predict numerically. To our knowledge, this is the first attempt at simulating melt flow behaviors in 3D simultaneous CIM based on the XPP constitutive equation and visual technique. The numerical results are in good agreement with the available experiment results, which establish the capability of the multiphase flow model presented in this article to simulate the flow behaviors of polymer melt in simultaneous CIM process.

Maleic anhydride (MAH) grafted polymers and silanes have been used as the compatibilizer in poly (butylene succinate)/lignin (PBS/lignin) composites. Compatibilized composites were fabricated by a novel vane extruder (VE). The effects of MAH grafted and coupling agent on the mechanical, thermal property, rheological property and water absorption of PBS/lignin were investigated. The results showed that the use of MAH grafted polymers and silanes resulted in significant improvements in flexural property, tensile modulus and tensile strength. Furthermore, MAH grafted polymers and silanes exhibited some improvement on the properties of vicat softening temperature as well as water absorption. The composites treated by MAH grafted polymers and silanes showed non-Newtonian behaviors from rheological tests. A better interfacial adhesion between lignin and matrix was observed from the scanning electron microscopy (SEM) of the compatibilized composites.

A new method is reported for preparing poly(butylene terephthalate) (PBT) / glass fiber (GF)-silicon carbide (SiC) composites. GFs were coated with SiC particles firstly and then the treated GFs (GF-SiC) were mixed with PBT. Scanning electron microscopy (SEM) images showed that some SiC particles dispersed on the surfaces of GFs, and other particles fell off from surfaces of GFs and dispersed around GFs after processing. The thermal conductivities of composites are increased with increase of GF-SiC. At 30 wt% GF-SiC, the thermal conductivity of composites reached 0.6392 W/mK, which improved nearly 160% compared to that of neat polymer. Differential scanning calorimetry (DSC) results indicated that GF-SiC increased crystallinity of PBT compared with that of neat PBT and had no obvious influence on the melting temperature of PBT. The crystallization temperature (T c ) and glass transition temperature of all samples shifted to a higher temperature. The addition of GF-SiC can improve the thermal stability of PBT/GF-SiC composites obviously. Dynamic mechanical properties and dielectric properties were also discussed in this paper.

The poly(methyl methacrylate-ethylene glycol dimethacrylate-2-acrylamido-2-methylpropanesulfonic acid) [poly(MMA-EGDMA-AMPS)] microsphere was produced by a soap-free emulsion polymerization of MMA, EGDMA and AMPS. The chemical composition, morphology, particle size distribution and properties of the obtained microspheres were characterized by energy dispersive spectrometer (EDS), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), a laser particle analyzer and thermogravimetric analysis (TGA). Results showed that the microspheres had a high-quality spherical morphology, irrespective of the components, and their particle sizes mainly ranged from 10 μm to 70 μm. The microspheres were thermally stable up to 190°C. As the AMPS loading was increased, the synthetic yield rate decreased and the water uptake increased. The optimum synthetic yield rate and water uptake were obtained at a 2.0 wt% AMPS. In addition, the selected microspheres with a diameter of approximately 25 μm provided an effective plugging, and the plugging rate was up to 80%. This study demonstrated that the plugging behavior of microspheres was due to their deformation, migration and aggregating properties in the plugging process, which made them potential materials for modifying the porous reservoir to enhance oil recovery in petroleum engineering.

The morphologies, crystalline structures, and thermal and rheological behaviors of isotactic polypropylene (iPP) blended with dicyclopentadiene based hydrogenated hydrocarbon resin (HCR) were investigated using scanning electron microscopy (SEM), wide-angle X-ray diffractometry, and differential scanning calorimetry in detail. Furthermore, the transparency, mechanical properties, and water vapor and oxygen permeability of biaxially oriented polypropylene films, fabricated from these iPP/HCR blends using a biaxial drawing machine, were examined. It was found that crystallinity varies with the HCR content of the iPP/HCR blend. In addition, amorphous HCR with its high glass transition temperature ( T g ) upon blending with iPP’s amorphous structure affords improvements in various film properties, such as mechanical properties, transparency, and gas permeabilities.

A model anti-cancer/tumor drug cis-diammineplatinum (II) dichloride (cisplatin) was loaded into micro- and nanofibers of cellulose, cellulose acetate (CA) and poly(ethylene oxide) (PEO), using various electrospinning techniques. Single-nozzle electrospinning was used to fabricate neat fibers of each category. Drug loading in cellulose fibers was performed using single-nozzle electrospinning. Encapsulation of cisplatin in CA and PEO-based fibers was performed using coaxial electrospinning. Morphological analysis of the fibers was performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The various categories of fibers exhibited diverse morphological features depending on the material compositions and applied process parameters. The drug-loaded cellulose nanofibers showed attached particles on the surface. These particles were composed of both the polymer and the drug. The CA-cisplatin fibers exhibited drug encapsulation within various diverse morphological conformations: hierarchical structures such as straw-sheaf-shaped particles, dendritic branched nanofibers and swollen fibers with large beads. However, in the case of PEO fibers, drug encapsulation was observed inside repeating dumbbell-shaped structures. Morphological development of the fibers and corresponding mode of drug encapsulation were correlated with process parameters such as applied voltage, concentrations and relative feed rates of the solutions and conductivities of the solvents.

This work was undertaken to examine the effect of poly(2-acryloyloxyethyl trimethyl ammonium chloride) (PATAC) branches grafted onto the backbones of starch on the toughening of starch film. A series of starch- g -PATAC samples having different levels of grafting ratio were prepared by the graft copolymerization of granular corn starch with ATAC in an aqueous system, using Fenton’s initiator through changing the weight ratio of the monomer to starch. The influences of grafted branches on the properties such as tensile strength, breaking elongation, work-to-break, bending endurance, moisture regain, swelling power, and solubility of starch film were evaluated by comparison with those of acid-treated starch (ATS). It was found that the branches were able to toughen starch film due to the significant increases in breaking elongation, work-to-break and bending endurance of the film. The branches were also able to increase its moisture regain, water swelling power, and solubility. In addition, the properties were dependent on the amount of the branches. Furthermore, the grafted starch was biodegradable when its grafting ratio did not exceed 7.5 wt%.

The present study investigated the solid particle erosion characteristics of Teflon under different impingement angles (15–90°), impact velocities (30–50 m/s), erodent sizes (300–600 μm) and stand-off distances (15–25 mm) at ambient temperature. The Teflon showed ductile erosion behavior exhibited a peak erosion rate at a 30° impact angle. The design of experiments approach utilizing Taguchi’s orthogonal arrays was applied to test the specimens on a compressed air jet type erosion test rig. Erosion efficiency ( η ) values were 0.29–16.7%, which indicates micro-plugging, plastic deformation and micro-cutting action as dominating erosion mechanisms. The experimental results are closer to the theoretical model. An optimal parameter combination was determined, which leads to minimization of erosion rate. Analysis of variance (ANOVA) was performed on the measured data and signal-to-noise (S/N) ratios. A mathematical correlation, consistent with the experimental observations, is proposed as a predictive equation for estimation of erosion rate of tested material. The morphology of erodent surfaces was examined by using scanning electron microscopy (SEM). Possible erosion mechanisms are discussed.

Linseed polyetheramide (LPEtA) resin was synthesized by the condensation polymerization of N-N-bis (2-hydroxyethyl) linseed oil fatty amide (HELA) with pyrogallol. The residual hydroxyl groups of LPEtA resin were further modified with isophorone diisocyanate (IPDI) to obtain linseed poly(urethane-etheramide) (ULPEtA) via addition polymerization. ULPEtA was modified with iron oxide nanoparticles in different weight percent (0.1 wt%, 0.2 wt%, 0.3 wt% and 0.4 wt%) producing ULPEtA/Fe 2 O 3 nanocomposite. Spectroscopic characterization of HELA, LPEtA and ULPEtA was carried out by using Fourier transform infrared (FT-IR), proton nuclear magnetic resonance ( 1 H-NMR) and carbon nuclear magnetic resonance ( 13 C-NMR) techniques. Physicochemical and physico-mechanical properties of LPEtA and ULPEtA were carried out by using standard methods. Thermal stability and anticorrosion performance were assessed by thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) and potentiodynamic polarization. The corrosion behavior of ULPEtA/Fe 2 O 3 nanocomposite coatings on mild steel was investigated in different corrosive environments (3.5 wt% HCl, 5.0 wt% NaCl, 3.5 wt% NaOH, and tap water) at room temperature. Surface morphology study was performed through scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Coating properties such as gloss, scratch hardness, flexibility and impact resistance were evaluated using standard methods. The results of this study showed that ULPEtA/Fe 2 O 3 nanocomposite coatings exhibit good physico-mechanical, anticorrosive properties and can be safely used up to 220°C.