In-mould coating (IMC) is carried out by injecting a thermosetting dilute carbon black suspension onto the surface of an injection-moulded part after the part has solidified, but while it is still in the mould. Due to the microscopic length scale of the IMC flow (10–25 µm), a study of the slip flow and rheological properties at high shear rates of the coating liquid is critical in modelling the IMC process. A customized microslit rheometer using micrometer-sized channel gaps between 25 and 100 µm was developed and used for that purpose. A reduced viscosity of the suspension due to slip (or apparent slip) at the fluid–wall interface was found in the 25 µm gap channel. Rheological equations for slit rheometers using no-slip and slip boundary conditions were used to determine the viscosity of the suspension at the microscale level. By analysing the viscosity data using the rheological equations developed, we can determine the values of the slip parameter, known as slip length. The slip boundary condition and high-shear-rate-plateau viscosity model are then applied to model the slip flow of the suspension. By including both the wall slip and high-shear-rate-plateau viscosity in the flow model, we can better predict the pressure distribution of the suspension.

Microfluidics and rheology are critical to modeling material processes such as In-Mold Coating (IMC). In the IMC process, a carbon black suspension is injected onto the surface of the molded part while the part is still in the mold. Due to the microscopic length scale of the IMC flow (10-25 μm), a study of the slip flow and rheological properties at high shear rates of the coating liquid becomes significant. A customized microslit rheometer was developed and used to measure the viscosity of a coating material being considered for IMC in the channel gaps between 25 and 100 μm (C. Aramphongphun Ph.D. Dissertation, The Ohio State University, 2006).

This research work studies the effects of processing conditions on mechanical properties of polymer nanocomposites. Polypropylene (PP) nanocomposites reinforced with 0.5 and 2.5 %wt multiwall carbon nanotubes (MWCNTs) were prepared via melt compounding and formed by injection molding. 2k Full Factorial design was used to plan the experiments and determine the influences of the processing conditions on mechanical properties and carbon nanotube dispersion in the nanocomposites. These conditions consist of five factors: (a) %wt content of MWCNTs (0.5 and 2.5 %wt), (b) barrel temperature (190 and 220°C), (c) injection velocity (25 and 45 mm/sec), (d) screw rotational speed (75 and 227 rpm) and (e) holding pressure (45 and 65 bar) while injection pressure and cooling time were set at 75 bar and 50 sec, respectively, for all conditions. The samples were examined by Young’s modulus and tensile strength using a Universal Testing Machine (UTM). In addition, Scanning Electron Microscopy (SEM) was applied to study the dispersion of carbon nanotubes in the nanocomposites. The results showed that PP/MWCNT nanocomposites had Young’s modulus of 1,740 MPa and tensile strength of 34.5 MPa while original PP had 1,450 MPa and 28 MPa, respectively. Therefore, the mechanical properties were improved significantly with the content of MWCNTs. Full Factorial experiments investigate that significant factors are %wt, barrel temperature, injection velocity, and screw rotational speed. Moreover, SEM showed that a high content of MWCNTs led to a highly oriented skin layer with well-dispersed MWCNTs.

Abstract.A gold plating process in the electronics industry can be classified as (i) all surface plating or (ii) selective plating. Selective plating is more widely used than all surface plating because it can save more gold used in the plating process and takes less plating time. In this research, the selective plating process called jet plating was studied. Factors that possibly affected the gold usage and plating voltage were also studied to reduce the production cost. These factors included (a) plating temperature, (b) crystal (inhibitor) amount, (c) distance between workpiece and anode, (d) plating current and (e) plating speed. A two-level Full Factorial design with center points was first performed to screen the factors. A Central Composite Design (CCD) was then employed to optimize the factors in jet plating. The amount of gold usage should be reduced to 0.366 g / 10,000 pieces, the plating speed should be increased to 4 m/min and the plating voltage should not exceed 8.0 V. According to the analysis, the optimal settings should be as follows: the plating temperature at 55.5 deg C, the crystal amount at 90%, the distance at 0.5 mm, the plating current at 2.8 A, and the plating speed at 4.5 m/min. This optimal setting led to gold usage of 0.350 g / 10,000 pieces and a plating voltage of 7.16 V. Confirmation runs of 30 experiments at the optimal conditions were then performed. It was found that the gold usage and the plating voltage of the confirmation runs were not different from the optimized gold usage and plating voltage. The optimal condition was then applied in production, which could reduce the gold usage by 4.5% and increase the plating speed by 12.5% while the plating voltage did not exceed the limit.

This paper presents a 3-D microstructures forming technique by inventing a new photomask making technique called Multi-Film Thickness mask (MFT mask). The paper also includes experiments using two 3-D microstructure forming techniques: (i) Gray Scale Lithography mask (GSL mask) and (ii) Multi-Film Thickness mask (MFT mask). The MFT mask is economical for the lithography process of 3-D microstructure forming, which is typically applicable to the making of Micro Electro Mechanical Systems (MEMS). A limitation of the MFT mask is that only 3-D microstructures with vertical sidewall profiles can be made.