Volume 31, Issue 5

A simulation optimization method based on design of experiments and adaptive metamodeling techniques is applied in this work to set process parameters in injection molding. The proposed method is used first to select the best processing conditions to injection molding a disposable camera front plate in the presence of either a single performance measure or a composite function of a series of performance measures. Secondly, it is used to select the best injection gate configuration from three different injection scenarios, as well as the values of mold temperature and melt temperature for a real automotive part in order to minimize process variability. The optimization results are discussed in light of the performance of the simulation optimization method.

Injection molding is the most important process for mass-producing plastic products. To help improve and facilitate the molding of plastic parts, advanced computer simulation tools have been developed. While modeling is complicated by itself, the difficulty of optimizing the injection molding process is that the performance measures involving the injection molding process usually show conflicting behaviors. Therefore, the best solution for one performance measure is usually not the best in some other performance measures. This paper introduces a simulation optimization method which considers multiple performance measures and is able to find a set of efficient solutions without having to evaluate a large number of simulations. The main components of the method are metamodeling, design of experiments, and data envelopment analysis. The method is illustrated and detailed here using a simple test example, and it is applied to a real injection molding case. The performance of the method using a different design of experiments is also discussed.

The high potential of layered silicate improving material properties of plastics has been discussed in a significant number of publications. However, homogeneously dispersing it with twin screw extruders is demanding. Available information on optimum screw configuration is contradictory. In this investigation, we develop a practical method for individually designing and optimising extruder sections. This method is applied for designing extruder sections for compounding masterbatches of high-density polyethylene and layered silicate. We found out that for best dispersion, dispersing sections should only be partially filled with melt. Thus, only right-handed kneading elements should be applied.

This article deals with hollow space formation that occurs during water injection technique (WIT). The tests presented help improve part quality by providing an in-depth understanding of the influence of polymers and the processes on the propagation of fluid bubbles. Moreover, typical part defects such as double-channel formation or water inclusions in the residual wall are avoided. As their formation has not yet been researched sufficiently, it is not currently possible to design WIT components in relation to the choice of material and residual wall thickness.

The effects of the length of glass fibers on the toughness of long glass fiber reinforced polyphenylene sulfide (PPS) composites (PPS-LFT), made by the pulltrusion process, were studied with regards to both the molding V notched specimen and the cutting V notched specimen. Toughness was excellent on the molding V notched specimen. By observing the fracture morphology of the molded V notched specimen, it was found that a crack was formed, due to a slip or debonding at the fiber surface. The crack was propagated along the fiber, due to the pulling out of fibers from the matrix polymer. Both the maximum load and the fracture energy increased with increasing length of the glass fiber, because the resistance created by pulling out the fibers increased with increasing fiber length. In the case of PPS-LFT, it is understood that toughness improved because the slip between the fiber and the resin occurs before the excessive elastic strain energy is stored.

In this work, the intrinsic viscosities of poly(ethylene glycol) (PEG) with a molar mass of 20,000 g·mol -1 were measured in water/acetone solutions from (283.1 to 313.1) K. The expansion factors of the polymer chains were calculated from the intrinsic viscosity data. The thermodynamic para­meters (entropy of dilution parameter, the heat of dilution para­meter, θ temperature, polymer-solvent interaction parameter and second osmotic virial coefficient) were derived by the temperature dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that mixtures of water/acetone are changed to the poorer solvents for PEG, by increasing temperature and volume fractions of acetone. Also, the temperature dependency of segment-segment and segment-solvent interactions for PEG in mixed water/acetone, is decreased by increasing volume fractions of acetone.

A large quantity of high-quality poly[ N -methyl B -methyl amino borazine] was synthesized via a solventless method from the monomer 1,3,5-trimethyl-2,4,6-tri(methyl amino)borazine. The thermal polymerization profile was investigated with differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), size exclusion chromatography (SEC), gas chromatography, and mass spectrometry. A polymerization mechanism involving the condensation reaction of two –N(H)CH 3 groups releasing methylamine was proposed and compared with the literature. As a result of cross-linking via the amino­methyl moiety, the cured polymer exhibited a molecular weight Mn of 790 g mol -1 , glass transition temperature of 64°C, high cross-link density, and thermal stability with a decomposition temperature of 165°C. Functionalized poly[ N -methyl B -methyl amino borazine] with chemical stability was fully characterized by 1 H, 13 C, 11 B nuclear magnetic resonance, FTIR, DSC, and SEC analyses. Ultraviolet absorption spectra evidenced changes in the structure of the aforementioned oligomers.

Graft copolymerization of granular starch maleate with acrylamide using Fenton’s initiator in aqueous dispersion was investigated for increasing grafting efficiency of the copoly­merization. The graft copolymerization was characterized in terms of grafting efficiency, grafting ratio, and conversion of monomer to polymer. Effects of maleate modification of starch on the efficiency, ratio, and conversion were explored. Influences of reaction variables such as pH value, molar ratio of H 2 O 2 to Fe 2+ , initiator concentration, monomer concentration, polymerization temperature, and time on the copolymerization were investigated. It was observed that the modification of starch markedly increased grafting efficiency and ratio. The graft copolymerization should be carried out under the protection of nitrogen gas at 30°C–45°C for 3 h using H 2 O 2 /Fe(NH 4 ) 2 (SO 4 ) 2 as initiator. Preferred molar ratio of H 2 O 2 /Fe(NH 4 ) 2 (SO 4 ) 2 /anhydroglucose was 20:1:1000 and optimal value of pH was in a range of 3–4. The condition could make grafting efficiency and conversion of monomer to polymer higher than 65% and 95%, respectively.

One of the most important applications of gamma irradiation is in the area of polymer modification. Nylon fibers that were gamma-irradiated with a dose higher than 25 kGy show fusion temperature and fusion enthalpy higher than the nonirradiated nylon. Nevertheless, under certain applications, the influence of nylon-irradiated fibers is noticeable below 50 kGy; therefore, physicochemical characterization is indispensable. In the present work, nylon 6,12 crystalline fibers were irradiated at low dose (from 1 to 25 kGy) at environmental conditions to confirm the thermal behavior. The melting point and fusion enthalpy were measured with differential scanning calorimetry; structural changes were studied using infrared spectroscopy; and fiber surface morphology was studied using atomic force microscopy. The results show an increase in both fusion temperature and fusion enthalpy, which are effects of the newly ordered high-molecular-weight oligo­mers. Recrystallization and oligomer formation can be observed in infrared spectra. Such behaviors are directly related to the partial damage over the surface and the mechanical performance of manufactured composites.