Volume 33, Issue 3

This paper compares two metamodel-based methodologies for multi-criteria simulation optimization (SO), using the injection molding of a disposable camera front housing as a case study. The first methodology uses linear regression metamodels and data envelopment analysis (DEA) to iteratively identify potential Pareto solutions, while the second one uses a Gaussian process metamodel and calculates an expected improvement to determine the new input runs sequentially. A one-to-one comparison of the approaches is presented using two optimization examples. The first example involves two process outputs and the second involves three. The approaches are evaluated using the same number of simulations, and are compared in terms of the quality of the obtained Pareto front, based on the hypervolume indicator. Advantages and disadvantages of both methods are discussed.

In the present study, a modified vacuum-assisted compression resin transfer molding (VACRTM) process has been developed to reduce the cycling period. The process uses an elastic bag placed between the upper mold and the preform to replace the mobile rigid mold in compression resin transfer molding. During resin injection, the bag is pulled upward by the vacuum applied in between the upper mold and the bag, and a loose fiber stack is then present. Resin is easily injected into the mold. Once enough volume of resin is injected, the compression pressure is applied on the bag, which compacts the preform and drives the resin through the remaining dry preform. Numerical results show that the bag compression phase is much longer than the resin injection one. A multistage compression strategy can be used to control the compression time. Due to inherent process defects, a higher volume of the injected liquid is essential and thus leads to a longer injection and compression phase in order to inject and squeeze the excess resin. The late compression is very slow in draining the residual resin. As compared with resin transfer molding, VACRTM can reduce the mold-filling time/injection pressure.

In this article, polypropylene (PP), short glass fiber-reinforced polypropylene (SFT-PP), and direct long glass fiber-reinforced polypropylene (DLFT-PP) interleaves were added as interleaves between fabrics during laminated molding to improve the interlaminar shear strength (ILSS). The test results showed that the ILSS was obviously improved. Furthermore, DLFT-PP interleaves were preheated to melt the PP before laminated molding and were then immediately placed between two fabrics to make the melted PP enter the gaps of the fabric and more fibers were used to further improve the ILSS. As expected, the ILSS increased.

The effects on the thermal, morphological, and crystallinity properties of the different loadings of magnesium oxide (MgO) blended with 10% rubbers [9:1 natural rubber (NR)/epoxidized NR] and metallocene linear low-density polyethylene (mLLDPE) in the presence of N , N - m -phenylenebismaleimide (HVA-2) compatibilizer were investigated. Fourier transform infrared spectroscopy showed that the epoxy and double-bond groups were absent in the blends. The crystallinity degree of mLLDPE composites were determined based on the results of differential scanning calorimetry. The crystallinity of the blends was continuously increased by the loading of MgO compared with blend of 0 phr MgO. Based on thermogravimetric analysis, the degradation temperature of NR in the blends with MgO is significantly enhanced compared with a pure NR and 0 phr MgO blend. The observations of the scanning electron micrographs indicate that the HVA-2 had caused a cross-linking reaction in the rubber phase and the domains of the MgO are separated from the continuous phase (mLLDPE).

Alginates are composed of β-D-mannuronic acid (M) and α-L-guluronic acid (G). In this study, block distributions of alginate samples were measured by a chemical fractionation method and 1 H-NMR spectroscopy, to compare the usefulness of the two methods. Block distribution results obtained from the two methods were found to be statistically different from each other; the chemical fractionation method gave consistently lower estimates for the amount of homopolymeric blocks. The repeatability of the results was also lower in the chemical fractionation method. By contrast, 1 H-NMR spectroscopy was found to be a reproducible and a faster method for determining the distribution of monomeric blocks in alginates.

Brake pad waste (BPW) powders were incorporated into styrene-butadiene rubber (SBR) formulations with varying amounts [2.5, 5, 10, 15, 20 and 40 parts per hundred parts of resin (phr)], by replacing the same amount of carbon black (CB). The physico-mechanical properties of the SBR/CB/BPW vulcanizates were determined before and after heat aging at 90°C. There was a slight reduction in the tensile strength, tensile modulus and surface hardness, as the BPW filler content was increased in SBR vulcanizates, up to 5 phr of BPW content, and a further increase in the waste filler content reduced the property significantly. A significant improvement in the compression set was noticed up to 20 phr BPW content loaded SBR systems. This is due to the synergistic effect of CB and the BPW filler. Swelling studies in different aromatic organic solvents, and the rheological behaviors of SBR/CB/BPW, were also studied. The swelling index of all formulations increased and the crosslink density decreased, with increase in BPW content. The degree of reinforcement between the elastomer and the BPW was studied using the Kraus equation.

Starch plasticized with glycerol and blended with polyvinyl alcohol (PVA) is recommended for use as a biodegradable material. The present article reports the results of studies of the natural weather ageing of starch/PVA blends having various amounts of glycerol in natural weather conditions of Saudi Arabia, with special reference to morphology and thermal behavior. Neat PVA has been used as a control to understand its behavior in its blend with starch. Differential scanning calorimeter studies indicated that an increase in the exposure time of samples to natural environment increases the crystallinity of PVA due to the breakage of intermolecular hydrogen bonding, thus facilitating the removal of the amorphous portion of the polymers in the blend. Thermogravimetric analysis revealed that an increase in glycerol content enhanced the degradation of the polymer, which is corroborated with the findings from the surface morphology using scanning electron microscopy and Fourier transfer infrared spectroscopy analyses.

In this study, magnetic polymeric nanoparticles were prepared use in for targeted drug delivery. First, iron oxide (Fe 3 O 4 ) magnetic nanoparticles (MNPs) were synthesized by coprecipitation with ferrous and ferric chloride salts. Then, to render the MNPs hydrophobic, the surfaces were covered with oleic acid. Finally, the hydrophobic MNPs (H-MNPs) were encapsulated with polymer. The emulsion evaporation technique was used for the preparation of polymer-coated H-MNP. Poly( dl -lactide-co-glycolide) (PLGA) and chitosan-modified PLGA were used as polymers. The polymeric nanoparticles were characterized and compared. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, small-angle X-ray scattering, size distribution, ζ potential, magnetic properties, and magnetite entrapment efficiency measurements were performed to investigate the properties of the nanoparticles. The XTT assay was performed to understand the biocompatibility (i.e., toxicity) of MNPs and magnetic polymeric nanoparticles to MCF-7 cells.

The novel proton exchange membranes of a direct methanol fuel cell (DMFC), the sulfonated functional polynorbornenes P(BN/NOH/NS), are successfully prepared via the sulfobutylation of poly(butoxymethylenenorbornene-co-norbornenemethanol) [P(BN/NOH)] with 1,4-butane sultone, and a cross-linked composite membrane consisting of P(BN/NOH/NS), P(BN/NOH), 4,5-imidazole dicarboxylic acid (IDA), and H 3 PO 4 has also been developed. Adding the IDA/H 3 PO 4 to the membrane promotes the proton conductivity of the cross-linked composite membrane to 2.79×10 -3 S/cm at 80°C, which is six times higher than the P(BN/NOH/NS) membrane. At the same time, the rigid polynorbornene backbones remarkably improved the methanol permeability resistance and dimensional stability of P(BN/NOH/NS) and its cross-linked membrane, compared with the Nafion 115 membrane. A single cell based on the cross-linked composite membrane showed an open-circuit voltage of 0.483 V and power density of 1.35 mW/cm 2 .

Polyurethane (PU) pervaporation (PV) membranes are promising for the recovery of phenol from water. The four kinds of PU membranes, with hydroxyl terminated polybutadiene (HTPB) as a soft segment and diamine or β-cyclodextrin (CD) as a chain extender, were prepared. The structures and properties of these membranes were characterized by means of Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and contact angle. Furthermore, the PV performances were investigated for separating phenol/water mixtures at different temperatures. The results showed that CD increased the permeability and selectivity of PU, at the same time. At 80°C, the total fluxes of pure PU membranes with HTPB (Mn=2500 g/mol) (H2500) and with HTPB (Mn=2000 g/mol) (H2000) were 6.96 kg μm m -2 h -1 and 6.09 kg μm m -2 h -1 , respectively, while those of PU membranes containing CD with HTPB (Mn=2500 g/mol) (H2500-CD) and with HTPB (Mn=2000 g/mol) (H2000-CD) were 9.16 kg μm m -2 h -1 (increased by 31%) and 8.23 kg μm m -2 h -1 (increased by 26%), respectively. The separation factors of H2500 and H2000 were 23 and 34, while those of H2500-CD and H2000-CD were 33 (increased by 43%) and 40 (increased by 9%). Additionally, the modification of CD crosslinking was simple and easy with less modifying agent.