Abstract
In order to measure the melt temperature profiles inside the nozzle of an injection molding machine, we proposed a new integrated thermocouple ceramic sensor plated on a zirconia ceramic sheet. In this study, we discussed the relationship between the radial melt temperature profiles inside the nozzle and plastication conditions, and the effects of polymer type and viscosity. The results can be summarized as below:
(1) We confirmed that this sensor can be repeatedly utilized for the exact measurement of melt temperature profiles under actual plastication conditions, high injection rates, and high temperatures.
(2) During the continuous plastication process, the melt temperature profiles and plastication capacity are considerably influenced by the screw position, which is the gap between the screw head and reservoir wall, and by the revolution rate.
(3) The followings were confirmed during the reciprocating plastication process; the temperature drop with an increase in revolution rate, the rise of the average temperature and peak value near the nozzle wall with an increase in the injection rate, and the temperature drop with a reduction of residence time inside the heating cylinder with an increase in the charge stroke.
(4) It was also clarified that the melt temperature of crystalline polymers decreases more than that of amorphous polymers because of the heat of fusion, and that the melt temperature of high viscosity polymers rises and becomes uniform with an increase in the residence time inside the cylinder due to the decrease of the plastication capacity and the increase of heat generation during the shearing process.
(5) Three layers are formed due to the difference in the flow velocity of polymers in the radial direction inside the reservior, and the above effects of plastication conditions are mainly reflected in the middle layer, which has a high velocity.
