Nanocomposites of poly(vinylidene fluoride) with organically modified silicate

Abstract We report a study of the impact of cold crystallization on the structure of nanocomposites comprising poly(vinylidene fluoride) (PVDF) and Lucentite STN™ organically modified silicate (OMS). Nanocomposites were prepared from solution over a very wide composition range, from 0.01 to 20% OMS by weight. Thermal preparation involved cold crystallization at 145 °C of quenched, compression-molded plaques. Static and real-time wide and small angle X-ray scattering (WAXS, SAXS), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) were used to investigate the crystalline phase of PVDF. For OMS content greater than 0.50 wt%, WAXS studies show that that the silicate gallery spacing increases modestly in the nanocomposites compared to neat OMS film, indicating a level of polymer intercalation. Using Gaussian peak fitting of WAXS profiles, we determine that the composition range can be divided into three parts. First, for OMS greater than 0.5 wt%, alpha phase fraction, ϕalpha, is insignificant (ϕalpha∼0–0.01). Second, at the intermediate range, for OMS between 0.5 wt% down to 0.025 wt%, beta phase dominates and the beta fraction, ϕbeta, is related to alpha by ϕbeta>ϕalpha. Third, below 0.025 wt% OMS, alpha dominates and ϕalpha>ϕbeta. The ability of small amounts of OMS (≥0.025 wt%) to cause beta crystal domination is remarkable. Overall, crystallinity index (from the ratio of WAXS crystal peak area to total area) ranges from about 0.36 to 0.51 after cold crystallization. Real-time WAXS studies during heating of initially cold crystallized nanocomposites show that there is no inter-conversion between the alpha and beta phase PVDF crystals, where these crystals coexist at room temperature. While all samples showed a strong SAXS Bragg peak, indicating existence of two-phase lamellar stacks, the sample containing predominantly beta phase had poorly correlated lamellar stacks, compared to samples containing predominantly alpha phase.

[1]  W. Prest,et al.  The morphology and thermal response of high‐temperature–crystallized poly(vinylidene fluoride) , 1975 .

[2]  W. Prest,et al.  The formation of the G phase from the a and polymorphs of polyvinylidene fluoride , 1978 .

[3]  D. M. Lincoln,et al.  Isothermal Crystallization of Nylon-6/Montmorillonite Nanocomposites , 2004 .

[4]  T. D. Fornes,et al.  Crystallization behavior of nylon 6 nanocomposites , 2003 .

[5]  E. B. Gowd,et al.  High-temperature X-ray diffraction studies on the crystalline transitions in the α- and γ-forms of nylon-6 , 2001 .

[6]  Andrew J. Lovinger,et al.  Unit cell of the ? phase of poly(vinylidene fluoride) , 1981 .

[7]  J. Koenig,et al.  An infrared study of phase-III poly(vinylidene fluoride) , 1979 .

[8]  D. M. Lincoln,et al.  Temperature dependence of polymer crystalline morphology in nylon 6/montmorillonite nanocomposites , 2001 .

[9]  C. Yoon,et al.  Polarization Mechanisms in Phase II Poly(Vinylidene Fluoride) Films. , 1983 .

[10]  A. Bottino,et al.  Characterization of PVDF membranes by vibrational spectroscopy , 2002 .

[11]  K. Matsushige,et al.  The II-I crystal transformation of poly(vinylidene fluoride) under tensile and compressional stresses , 1980 .

[12]  O. Glatter,et al.  19 – Small-Angle X-ray Scattering , 1973 .

[13]  D. R. Paul,et al.  Nylon 6 nanocomposites by melt compounding , 2001 .

[14]  W. Zhong,et al.  Vibrational mode analysis of β-phase poly(vinylidene fluoride) , 2002 .

[15]  N. Ogata,et al.  Structure and thermal/mechanical properties of poly(ethylene oxide) : clay mineral blends , 1997 .

[16]  K. Tashiro,et al.  Molecular Vibrations of Three Crystal Forms of Poly(vinylidene fluoride) , 1975 .

[17]  J. Jog,et al.  Intercalated poly(vinylidene fluoride)/clay nanocomposites: Structure and properties , 2003 .

[18]  J. Jog,et al.  Polymorphism in intercalated poly(vinylidene fluoride)/clay nanocomposites , 2003 .

[19]  J. Runt,et al.  P(VDF-TrFE)-layered silicate nanocomposites. Part 1. X-ray scattering and thermal analysis studies , 2004 .

[20]  A. Nandi,et al.  The influence of chain structure on the equilibrium melting temperature of poly(vinylidene fluoride) , 1991 .

[21]  Tianxi Liu,et al.  Crystal transformation and thermomechanical properties of poly(vinylidene fluoride)/clay nanocomposites , 2005 .

[22]  C. Batt,et al.  Dramatic Enhancements in Toughness of Polyvinylidene Fluoride Nanocomposites via Nanoclay‐Directed Crystal Structure and Morphology , 2004 .

[23]  H. Kawai,et al.  The Piezoelectricity of Poly (vinylidene Fluoride) , 1969 .

[24]  J. Lando,et al.  A reexamination of the crystal structure of phase II of poly(vinylidene fluoride) , 1981 .

[25]  C. Ramesh,et al.  Studies on the Crystallization Behavior of Nylon-6 in the Presence of Layered Silicates Using Variable Temperature WAXS and FTIR , 2005 .

[26]  Y. Ishida,et al.  Estimation of amorphous specific volume of poly(vinylidene fluoride) as a function of temperature , 1973 .

[27]  J. Jog,et al.  Poly(vinylidene fluoride)/clay nanocomposites prepared by melt intercalation: Crystallization and dynamic mechanical behavior studies , 2002 .

[28]  Donald R Paul,et al.  Effect of melt processing conditions on the extent of exfoliation in organoclay-based nanocomposites , 2001 .

[29]  Kwang Man Kim,et al.  The Effect of Silica Addition on the Properties of Poly((vinylidene fluoride)‐co‐hexafluoropropylene)‐Based Polymer Electrolytes , 2001 .

[30]  D. Bassett,et al.  Developments in crystalline polymers , 1982 .

[31]  L. Mathias,et al.  Observation of α and γ crystal forms and amorphous regions of nylon 6-clay nanocomposites using solid-state 15N nuclear magnetic resonance , 1999 .

[32]  N. Ogata,et al.  Structure and thermal/mechanical properties of poly (∈-caprolactone)-clay blend , 1997 .

[33]  G. Strobl,et al.  Direct evaluation of the electron density correlation function of partially crystalline polymers , 1980 .

[34]  Xiao-hui Liu,et al.  An Unusual Crystallization Behavior in Polyamide 6/Montmorillonite Nanocomposites , 2001 .

[35]  Xiao-hui Liu,et al.  Non-isothermal crystallization behaviors of polyamide 6/clay nanocomposites , 2002 .

[36]  Steven C. Roth,et al.  Monitoring the relaxation behavior of nylon/clay nanocomposites in the melt with an online dielectric sensor , 2005 .

[37]  F. Chang,et al.  Crystallization kinetics and crystallization behavior of syndiotactic polystyrene/clay nanocomposites , 2001 .

[38]  Y. Ishida,et al.  Annealing effects in poly(vinylidene fluoride) as revealed by specific volume measurements, differential scanning calorimetry, and electron microscopy , 1973 .

[39]  N. Stribeck,et al.  Novel aspects in the structure of poly(ethylene terephthalate) as revealed by means of small angle x-ray scattering , 1991 .

[40]  K. Tashiro,et al.  Vibrational spectra and disorder-order transition of poly(vinylidene fluoride) form III , 1981 .

[41]  P. Maiti,et al.  Influence of Crystallization on Intercalation, Morphology, and Mechanical Properties of Polypropylene/Clay Nanocomposites , 2002 .

[42]  Yozo Chatani,et al.  Crystal Structures of Three Crystalline Forms of Poly(vinylidene fluoride) , 1972 .

[43]  N. S. Murthy,et al.  PREMELTING CRYSTALLINE RELAXATIONS AND PHASE TRANSITIONS IN NYLON 6 AND 6,6 , 1991 .