In this paper, thermal conductivity of polypropylene (PP) was measured at various temperature and pressure, in order to obtain the basic data-base of the thermal properties of polymeric materials applicable for the precise simulation of injection molding processes. The measurement of the thermal conductivity was performed by using the transient hot-probe method, the probe of which was installed in the cylinder of a PVT measurement system. The obtained results were correlated with the resin temperature and pressure, and an empirical correlation was derived. Since this empirical correlation enables to estimate the thermal conductivity of PP continuously from the molten state to the solidified state, the behaviors of injection-molded polymer, such as warping and solidification, can be simulated more accurately by using so-called CAE (Computer-Aided Engineering) technique.

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In this paper, the authors proposed a refined digital predictive control method of the barrel temperature in an injection-molding machine. In the refined method, duty ratio of the barrel heater is determined by the barrel temperature-change were derived from a simple two-layers model with lumped heat-capacity, and the coefficients of the equations were experimentally determined from the heating/cooling characteristics of the barrel.
Using the proposed method, temperature of a heating barrel of an injection-molding machine was controlled, and the controlling performance was discussed. The results showed that a clear “hunting” phenomenon observed, for the predicting interval equal to the controlling interval, but that the controlling performance was improved by optimizing the predicting interval.

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The measurement of temperature distribution inside melt flow is of great importance in clarifying the molding phenomena and in developing the models for numerical simulations. Temperatures inside an injection mold can be measured using thermocouples, infrared-probe monitoring systems, ultrasonic wave or other methods. However, none of these methods enable the measurement of the temperature distribution along the cavity thickness direction in detail.
In this paper, the authors proposed a measurement method using an Integrated Thermocouple Sensor which consists of several thermocouples plated on a thin polyimide film. We examined the sensor's output voltage, response time and errors, as well as measured temperature profiles along the cavity thickness direction inside an injection mold, in order to confirm its applicability. The results obtained were as follows:
(1) The preliminary experiments showed that the lead wire longer than 5mm along the flow direction was necessary in order to avoid error due to thermal conduction.
(2) The experiments, carried out on general purpose polystyrene with various injection rates, resulted in reasonable temperature profiles across the cavity thickness that corresponded with the expected velocity profiles.
(3) During the filling process, a constant heat balancing layer appeared, and the temperature core layer inside the boundaries slightly increased, probably due to heat generation.
(4) During the compression process, a distinct temperature rise was observed between the skin and the core layers due to the compression melt motion toward the cavity wall.
Through these measurements, we confirmed the feasibility of the sensor proposed in this study.

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Measurement of melt temperature in the nozzle of an injection molding machine is very important in clarifying molding phenomena. As stated in the previous paper, the Integrated Thermocouple Sensor consisting of many thermocouples plated on a thin polyimide film was developed to measure the temperature distribution along the cavity depth.
This paper reports on the application of this sensor to measure cross-sectional melt temperature profiles in the nozzle of an injection molding machine. We investigated the effects of several plasticating conditions and screw channel depth at metering zone on the radial temperature distribution of the melt injected through the nozzle, and obtained the following results.
(1) We confirmed that the Integrated Thermocouple Sensor can be successfully utilized as a practical tool for the investigation of plasticating conditions and screw design.
(2) Even if screw channel depth at metering zone, screw feed stroke or revolution rate change, the melt temperature deviation in the nozzle channel is at a maximum in the center of the region between the channel center and the channel wall. As the screw channel depth at metering zone decreases or the feed stroke increases, the maximum deviation increases.
(3) As the melt residence time in the reservoir increases, the temperature deviation distribution flattens.
(4) The temperature deviation distribution is closely related to how the melt accumulates in the reservoir during the charging process as well as the melt flow behavior in the nozzle channel during the injection process.

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The shrinkage degree ξ of polymer products must be considered when the molds are at the stage of designing. On the calculation of ξ, the descending temperature ΔT of polymer products after molding process and α (thermal expansion coefficient in polymer products) are necessary. It was found that α has the typical distributions at the various layers along the machine direction (MD) and the transverse direction (TD), especially HDPE products. Consequently, α distributions should be prodicted for estimation of accurate ξ of HDPE products.
The blow molding process is divided into the following two processes.
(a) Parison extrusion process (b) Blow-up process
We reported the previous paper that α_P (thermal expansion coefficient in parison) distributions correspond to the strain distributions under extrusion process. In this study, we have investigated the experimental data of α distributions after blow-up process and calculated the elongational strain in deforming parison by analysis using finite element method. The following results were obtained.
(1) The measured data of α in products correspond to that of α_P which gets the reduction by the elongational strain during blow-up process
(2) We proposed the model equation of relationship between α_P and α. The model equation expressed the characteristic of measured data of α in this study.

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In order to examine the effect of thermoforming process on the fracture behavior of thermoplastics, uniaxial tensile tests and deformation recovery measurements at heating were carried out for uniaxially stretched poly(methyl methacrylate)(PMMA). In spite of the development of tensile stress during rapid cooling processes, stretched specimens were much more ductile than undeformed ones. Plastic strain frozen in the thermoformed specimens was recovered at heating only in the glass transition range. Thus, the molecular structure of the stretched PMMA was supposedly free from the localization of strain energy which is probably a key factor reducing the static strength of thermoplastics. The smoothness of the specimen surface probably improved by stretching was also likely to contribute to the increase of ductility for the PMMA.

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This paper deals with a technique for improving the shape quality of injection-molded polymer products by controlling the heat transfer within the mold. In this paper, the authors tried to find a refined technique for improving the sink-mark problem, and examined the mechanism governing the sink-mark generation on an asymmetrically cooled polystyrene strip from the standpoint of thermal engineering. Sink-marks due to the shrinkage are considered to be controlled by both the cohesion between the molten polymer and the mold wall, as well as the stiffness of the frozen layer which gradually develops within the molded polymer adjacent to the mold wall. Although limited to polystyrene strip, the results obtained in the present study showed that the cohesive power of the molten polymer increases rapidly when the mold wall temperature exceeds the thermal deformation temperature of the polymer, and that the thickness of the frozen layer, which dominates its stiffness, monotonously increases with increasing time elapsed after the shot and decreasing with the mold wall temperature.

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