Optical monitoring of polypropylene crystallization during injection molding

Abstract

The nonisothermal crystallization of polypropylene resins, i-PP, during injection molding, using an optical device inserted in the injection mold cavity was monitored. The device detected the change of optical properties which occurs in polymers during their crystallization process; thus the intensity of a laser beam after it passed through the crystallizing polymer was measured during an injection molding cycle. The collected light intensity after the end of the cycle was correlated with the morphologies and final crystallinity degree of the samples. The influence of nucleating agents and the change of the parameters of the injection molding process on the morphology and optical signals were also investigated. The morphologies were analyzed by polarized light optical microscopy, PLOM. The % of crystallinity of the samples was measured by wide angle X-rays diffraction, WAXS. It was concluded that the optical device was sensible to different polymer crystallization kinetics, morphology type, and changes in the injection molding parameters. It was also found that the mold temperature and packing pressure and time were the factors that affected most the kinetics of crystallization of these polymers in this particular disk geometry. The WAXS results showed that the lower the final light intensity the higher the % of crystallinity in the samples. POLYM. ENG. SCI.,

Mechanical properties and stem cell adhesion of injection‐molded poly(ether ether ketone) and hydroxyapatite nanocomposites

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A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins

“…An iron-constantan thermocouple was used to check the mold temperature periodically. The mold cavity had disk geometry, with diameter of 90 mm and thickness of 2 mm, a sapphire window to optically monitor each injection molded cycle and a pressure transducer, as already described in our previous work 40 . The polymer was injected through the center of the cavity, as shown in Figure 1a.…”

“…Table 2 shows the analyzed molding conditions. These analyzed conditions were chosen based on early study 40 that shows that the mold temperature and flow rate are the parameters that affected most the kinetics of crystallization of these polymers in this particular disk geometry.…”

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Tailoring the crystalline structure of polypropylene parts molded through water‐assisted injection molding: Effects of melt temperature and polymeric nucleating agent

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