Pulse injection molding

The ring-opening metathesis polymerization of dicyclopentadiene was monitored by ultrasonic spectroscopy.16 The thermoset poly(dicyclopentadiene) is formed by ringopening and cross-linking in a reaction injection molding system. A reaction cell with a plastic window was constructed for use with pulse echo ultrasonic spectroscopy. Realtime measurements of density, longitudinal velocity, acoustic modulus and attenuation were monitored. Reaction kinetics were successfully determined and monitored using this technique. 

Various processes are reported to provide a means to pulsate the melt to improve performance of the extruded product. An example is the Scorim process reviewed in the Injection Molding section in this chapter. A variation in the IM process has been applied to production of reinforced extruded TP pipe. This has been a center of interest, on the argument that a predictable orientation of fiber would considerably increase the pressure resistance of the pipe, without the need to increase wall-thickness (on the analogy of winding a TS resin pipe with continuous filament). The Scorim process combines the extrusion of a fiber-reinforced compound with pressure pulsing around the periphery of the die, which appears to have the effect of orientating the reinforcement. 

To study the skin-core effects in more detail, ultrasonic measurements were made on a sample as it was machined progressively thinner from alternate sides, with the removed layer being 0.4 mm thick. Results from successive experiments were compared to obtain the pulse transit times for the layer of material which had been removed. Analyses of these transit times gave the profiles of 3 and for sample 1 shown in Figures 14.8 and 14.9, respectively. Besides the peak in the modulus in the skin region there is another peak about 1.2 mm from the surface of the plaque. This peak has also been observed in static modulus experiments on other injection molded plaques and has been attributed... 

Implantable DDSs can be used for antibiotic administration and immunization, treatment of diseases such as diabetes and bone infections. The latter can be treated via sustained release, cyclic release, multi-phase release, pulse release and the controlled release of multiple drugs. Traditionally, the most common method for manufacturing implants is to blend the drug with the excipients and then use a compression- or injection-molding technique to manufacture the devices. However, this technique has some disadvantages regarding the optimal control of the structure and internal architecture of the DDS. Biotextiles may provide novel strategies for the development of implantable DDSs. 

Pulse cooling is a method where mold temperatures are monitored, and cold water is introduced to control the steel temperature. A variation of this technique delivers water immediately after mold closing for variable pulse times. Using this approach, better distribution of surface temperature on injection molded parts may be achieved compared to traditional cooling with a thermolator. Thermocouples and a thermal camera were used to evaluate mold and part surface temperatures respectively. 

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