Optical Monitoring of Polypropylene Crystallization During Injection Molding

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., 2008. © 2007 Society of Plastics Engineers

[1]  P. Zhu,et al.  Studies of Injection-Moulded Isotactic Poly(propylene) by Synchrotron WAXD/SAXS: Effects of Nucleating Agent on Morphological Distribution , 2003 .

[2]  J. Viana.  Development of the skin layer in injection moulding: phenomenological model , 2004 .

[3]  James L White,et al.  Comparison of structure development in injection molding of isotactic and syndiotactic polypropylenes , 2002 .

[4]  C. Xie,et al.  The effect of nucleating agent on the crystalline morphology of polypropylene (PP) , 2003 .

[5]  A. Isayev,et al.  Crystallinity and microstructure in injection moldings of isotactic polypropylenes. Part 1: A new approach to modeling and model parameters , 1999 .

[6]  D. Y. Yoon,et al.  Effect of interference between anisotropic scattering entities on light scattering from polymer films. II. The correlation function approach , 1974 .

[7]  A. J. Bur,et al.  In‐situ monitoring of product shrinkage during injection molding using an optical sensor , 1999 .

[8]  R. E. S. Bretas,et al.  Characterization of i‐PP shear‐induced crystallization layers developed in a slit die , 2004 .

[9]  J. P. Berry,et al.  Mechanical properties of nucleated polypropylene and short glass fiber-polypropylene composites , 1996 .

[10]  A. L. Marinelli,et al.  Optical monitoring of polyesters injection molding , 2006 .

[11]  M. Polášková,et al.  Injection-moulded α- and β-polypropylenes: I. Structure vs. processing parameters , 2005 .

[12]  A. Cunha,et al.  The thermomechanical environment and the microstructure of an injection moulded polypropylene copolymer , 2002 .

[13]  J. Spruiell,et al.  An experimental method for studying nonisothermal crystallization of polymers at very high cooling rates , 1996 .

[14]  M. Fujiyama,et al.  Melting and crystallization behaviors of injection-molded polypropylene , 2000 .

[15]  G. Titomanlio,et al.  Modeling the interactions between light and crystallizing polymer during fast cooling , 2004 .

[16]  C. Chiu,et al.  Dynamic modeling of the mold filling process in an injection molding machine , 1991 .

[17]  G. Seytre,et al.  In‐line monitoring of the injection molding process by dielectric spectroscopy , 2002 .

[18]  M. Viens,et al.  On-line ultrasonic monitoring of the injection molding process , 1997 .

[19]  P. Zhu,et al.  Morphological distribution of injection-moulded isotactic polypropylene: a study of synchrotron small angle X-ray scattering , 2004 .