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Injection molded Short Glass Fiber Reinforced Thermoplastics (SFRTP) are widely used in industry because of advantages in material properties, availability, economics and ease of processing. The thermo-mechanical history experienced by the material during processing produces significantly anisotropic microstructural and consequently mechanical properties, varying not only spatially, but directionally. / This work attempts to examine quantitatively various aspects of microstructure and the effect of processing conditions in SFRTP. The matrix phase properties, such as crystallinity, morphology and molecular orientation distribution, as well as the fiber phase microstructure such as concentration, length and orientation distributions have been analyzed quantitatively, and explained. Experimental techniques, including optical and electron microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, thermo-gravimetric analysis, etc. have been used. The results indicate complex changes in microstructure from skin to core in the injection molded samples. Both matrix and fiber phase microstructures are affected by the basic thermal and flow processes that occur during the injection molding process. A first order model has been developed to predict fiber orientation distributions, which agree well with the experimental results.

Injection moulding is one of the most important manufacturing processes in the plastic industry. The temperature distribution of the polymer, while it is inside the mould cavity, influences the properties of the product. The measurement and control of these temperature profiles can enhance the economy of the process and the part quality. / A method to measure melt temperature inside the mould cavity was developed. It consists of an insert, located in the movable plate, that can place thermocouples at different positions. The depth of the thermocouple tip is adjusted manually. These sensors offer an attractive way to perform the measurements because of their easy calibration procedure. The temperature measurements were influenced by the thermocouple tip geometry. / Data were collected at different locations and depths of the mould cavity and the temperature profiles were analyzed. The temperature distribution depended on the wall temperature and the temperature of the polymer as it enters the cavity. The effect of different flow rates was also studied and it demonstrated to affect the temperature profiles. / A control algorithm was developed to control the average of the peak temperatures at three locations in the cavity. The manipulated variable was the coolant temperature and the process disturbance was the front barrel temperature. The transfer functions of the controlled variable with respect to the manipulated and disturbance variables were identified and modeled. / Finally two controllers were designed, tuned, simulated and implemented on the machine. The first is a static feedforward - feedback controller, and the second is a dynamic feedforward - feedback controller. The feedback loop was designed using an internal model control (IMC) algorithm. The static feedforward - feedback controller was found to have a better performance.

Three innovative plastic building products have recently been introduced to the residential construction industry: plastic shingles, plastic lumbers, and plastic foam core sandwich panels. They are each described, compared to conventional practice, and evaluated for their potential for implementation. It is shown that designers and builders will have to rework their budgets, study safety factors, and invest time and effort into acquiring new skills, if they wish to fully benefit from these products. However, an incentive for such concessions, is the possible financial reward from successfully meeting demands for efficiency, durability, and environmental sensitivity in housing.

The injection molding process, due to its versatility, cost effectiveness, and ability to produce precise complex articles is widely used in plastics processing. Mold cavity pressure is a good indicator of the processes taking place in the cavity and plays an important role in determining the quality of the molded articles. The dynamic modeling and control of cavity pressure, based on a physically-based approach, is studied in this research project. The work deals with the filling and packing phases. / A lumped physically-based model was developed in order to study the behavior of the system. The model is derived from conservation laws and incorporates a physical understanding of the process. The whole system was divided into subsystems including the hydraulic system, ram-screw, barrel, and polymer delivery system. It was found necessary to account for polymer melt elasticity as well as non-Newtonian behavior of the polymer melt flow. Consideration of the growing solid skin in the polymer delivery system was found to be necessary. / The dynamics of the cavity pressure during the filling phase were investigated and found to be non-linear and time-varying in relation to the hydraulic servo-valve opening which is the manipulated variable. The dynamic behavior of the cavity pressure is approximated by piece-wise linearization of the non-linear governing equations to derive a transfer function using the physically-based model which is of fifth order. Adaptive PI, PID, and IMC controllers were designed and tested for the control of the cavity pressure. Various tuning techniques, along with changes in set-point, were used to determine conservative settings for the PI and PID controllers. / A similar approach was used to study the dynamics of the cavity pressure during the packing phase. A sixth order transfer function, with piece-wise linearization, was derived to approximate the non-linear and time-varying behavior of the cavity pressure during packing. The adaptive PI, PID, and IMC controllers were successfully applied into the packing phase. The transition of the filling-to-packing was selected to be detected by the derivative of the cavity pressure and adaptive controllers were successfully used for this phase. / Two commonly used injection molding grade thermoplastics, polyethylene and polystyrene, were used in experimental part of this work for model validation and controller testing.

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An in-line process rheometer, employing a proven shear-stress transducer, was designed and built for polymer melts. The entire process stream runs through the rheometer, giving it a much faster response time than conventional side-stream models. The possibility of using the in-line rheometer for dynamic mechanical analysis was investigated and methods were developed to obtain the complex modulus over a wide range of frequencies with a single measurement. Measurement techniques for shear viscosity testing were also developed along with algorithms to compensate for the effects of process pressure and temperature. / The rheometer was used as a viscosity sensor to provide feedback control for a polypropylene visbreaking process. A first order plus dead time model was used to model the process and the rheometer together, and typically had dead times of less than 60 s and a first order time constant of 15 s. Gain scheduling was incorporated into minimum variance and proportional-integral controllers to achieve closed-loop settling times of 200 s for viscosity setpoint changes and process disturbances.

The compatibility of suspension PVC with a series of twelve different plasticizers was determined using the estimated values of compatibility predictors, such as the Hildebrand solubility parameter, as well as actual measurements of compatibility, such as the solid-gel transition temperature and the Flory-Huggins interaction parameter. Different relative orders of compatibility were obtained between the plasticizers studied using the two different approaches. Then, using the twelve different plasticized PVC compounds, the ease of fusion during processing (Brabender mixing and compression moulding) was evaluated and found to be closely related to the PVC/plasticizer compatibility. It was found that the more compatible the plasticizer, the more rapid the fusion during processing, but the higher the torque peak during Brabender mixing. It was also found that the temperature at the fusion peak in a Brabender torque rheometer is closely related to the various parameters used to measure the compatibility, (e.g. the solid-gel transition temperature, the interaction parameter, and the activity parameter). Finally, the rheological and tensile properties of plasticized PVC were determined and it was found that both the rheological and tensile behaviour are highly dependent on the level of fusion of the PVC compound, which in turn depends on the plasticizer type. However, once a high level of fusion is attained, these properties depend more on the viscosity of the plasticizer and the glass transition temperature of the compound.

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