Melting processing window analysis

The previous process examinations show that the molded parts within the selected process window often show significant variations in e examined quality parameters. Not only the melt temperature, but also the mold temperature and the injection speed considerably influence the fiowability and the mechanical properties of the molded part. Still, a further process analysis has to be performed to gain additional and extensive knowledge of the optimum processing conditions. 

An analytical approach for estimating the bulk melt temperature within a mold eavity using data from in-mold temperature sensors has been further developed. The analysis uses a conveetive boundary eondition to approximate the contact resistance of the mold-melt interface. The measured mold coolant temperature was also taken into account. The accuraey of the predietions was tested over a wide processing window. While most trends were eorreetly predicted, the magnitude of the predietions varied greatly due to the high sensitivity of the analysis to the temperature measurements. 

Determination of the thermal decomposition temperature by thermal gravimetric analysis (tga) defines the upper limits of processing. The tga for cellulose triacetate is shown in Figure 11. Comparing the melt temperature (289°C) from the dsc in Figure 10 to the onset of decomposition in Figure 11 defines the processing temperature window at which the material can successfully be melt extmded or blended. 

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