Investigation of crystallization behavior of solid and microcellular injection molded polypropylene/nano-calcium carbonate composites using carbon dioxide as a blowing agent

This work is aimed at investigating the crystallization behavior of solid and microcellular injection molded polypropylene/nano-calcium carbonate composites. The effects of processing conditions, such as injection speed, mold temperature, and carbon dioxide concentration (used in microcellular injection molding), as well as the filler concentration on the crystal form, crystal orientation, and crystallinity were studied using 2D-wide-angle X-ray diffraction and differential scanning calorimetry. β-form crystals found in the surface layer of injection molded samples under high injection and mold temperature due to stronger shear effect. The orientation degree calculated from the X-ray diffraction images by the Hermans function was high in the surface layer and decreased as the distance from the mold surface increased. The addition of the nano-calcium carbonate filler promoted the formation of β-form crystals but reduced the orientation degree and crystallinity as the nanoparticles disturbed the orientation of the molecular chains. On the other hand, when using the foaming process, the formation of β-form crystals was inhibited and the orientation degree was reduced, but the crystallinity of the samples increased, likely due to enhanced molecular chain mobility from the supercritical carbon dioxide which acted as a plasticizer. The crystallinity of the samples was greater in the surface layer but showed no dependence on the injection speed or mold temperature.

[1]  Xiangmin Han,et al.  Polymer nanocomposite foams , 2013 .

[2]  L. Turng,et al.  Artificial neural network–based supercritical fluid dosage control for microcellular injection molding , 2012 .

[3]  Changyu Shen,et al.  Crystal morphology and structure of the β‐form of isotactic polypropylene under supercooled extrusion , 2011 .

[4]  Jungjoo Lee,et al.  A novel method for improving the surface quality of microcellular injection molded parts , 2011 .

[5]  Constantine D. Papaspyrides,et al.  Polymer/layered silicate (clay) nanocomposites: An overview of flame retardancy , 2010 .

[6]  Changyu Shen,et al.  Morphological Evolution and Orientation Development of Stretched iPP Films: Influence of Draw Ratio , 2010 .

[7]  D. Tasis,et al.  Carbon nanotube–polymer composites: Chemistry, processing, mechanical and electrical properties , 2010 .

[8]  J. Yeh,et al.  The mechanical/thermal properties of microcellular injection-molded poly-lactic-acid nanocomposites , 2009 .

[9]  D. Rodrigue,et al.  The effect of injection molding conditions on the morphology of polymer structural foams , 2009 .

[10]  R. Misra,et al.  Nonisothermal crystallization behavior of polypropylene–clay nanocomposites , 2006 .

[11]  Jian Shen,et al.  Studies on crystal morphology and crystallization kinetics of polypropylene filled with CaCO3 of different size and size distribution , 2006 .

[12]  Chul B. Park,et al.  The Effects of Exfoliated Nano-clay on the Extrusion Microcellular Foaming of Amorphous and Crystalline Nylon , 2006 .

[13]  Giuseppe Titomanlio,et al.  Modeling of morphology evolution in the injection molding process of thermoplastic polymers , 2005 .

[14]  Pj Piet Lemstra,et al.  Effect of in situ prepared silica nano-particles on non-isothermal crystallization of polypropylene , 2005 .

[15]  Mingjun Yuan,et al.  Microstructure and mechanical properties of microcellular injection molded polyamide-6 nanocomposites , 2005 .

[16]  L. Turng,et al.  Microstructure and crystallography in microcellular injection-molded polyamide-6 nanocomposite and neat resin , 2005 .

[17]  M. Okamoto,et al.  Visual observation of CO2 foaming of polypropylene‐clay nanocomposites , 2004 .

[18]  Chul B. Park,et al.  Effects of die geometry on cell nucleation of PS foams blown with CO2 , 2003 .

[19]  L. J. Lee,et al.  Extrusion of polystyrene nanocomposite foams with supercritical CO2 , 2003 .

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

[21]  C. Chan,et al.  Polypropylene/calcium carbonate nanocomposites , 2002 .

[22]  Mitsuko Takada,et al.  Effects of CO2 on crystallization kinetics of polypropylene , 2001 .

[23]  G. Vigier,et al.  Influence of the β crystalline phase on the mechanical properties of unfilled and CaCO3-filled polypropylene. I. Structural and mechanical characterisation , 2001 .

[24]  Pj Piet Lemstra,et al.  Innovation in polymer processing , 1999 .

[25]  Y. P. Handa,et al.  Effect of compressed CO2 on phase transitions and polymorphism in syndiotactic polystyrene , 1997 .

[26]  Y. P. Handa,et al.  CO2-Assisted Melting of Semicrystalline Polymers† , 1997 .

[27]  Dimitris I. Collais,et al.  Tesile toughness of microcellular foams of polystyrene, styrene‐acrylonitrile copolymer, and polycarbonate, and the effect of dissolved gas on the tensile toughness of the same polymer matrices and microcellular foams , 1995 .

[28]  Vipin Kumar,et al.  Semi-continuous production of solid state pet foams , 1995 .

[29]  G. Ehrenstein,et al.  Extrusion of self‐reinforced polyethylene , 1991 .

[30]  Z. Wilchinsky.  Measurement of Orientation in Polypropylene Film , 1960 .