Dispersion, crystallization kinetics, and parameters of Hoffman–Lauritzen theory of polypropylene and nanoscale calcium carbonate composite

Abstract

Isothermal and nonisothermal crystallization of polypropylene (PP)/calcium carbonate (CaCO3) with two particle sizes (250–300 nm and 20–25 nm) were studied by differential scanning calorimeter. Equilibrium melting temperature (T m0) determined from both linear and nonlinear Hoffman–Weeks relations showed that the composites had a lower T m0 as a result of the CaCO3 particles destroying the crystal of PP. Kinetics of the isothermal and nonisothermal crystallization was described by Avrami equation. For the first time, without the assumption of a constant U* value, Lauritzen–Hoffman parameters (U* and Kg) were evaluated directly by data‐fitting method for isothermal crystallization, and by Vyazovkin's method for nonisothermal crystallization. Kg values obtained were similar with and without the assumption of a constant U*and comparable to those in the literature. Both U* and Kg indicate the dual role the CaCO3 particles as nucleating agents to enhance the crystallization and as obstacles to the chain movement to reduce the crystallization. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Isothermal crystallization and melting behavior of polypropylene with lanthanum complex of cyclodextrin derivative as a β‐nucleating agent

“…Comparing with T , the values of T were higher in all samples, and similar trend have been reported by some studies, where T was determined by linear and nonlinear Hoffman‐Weeks procedure. 37, 43, 44 The a values for α‐crystal in pure iPP determined in the present work was very close to that reported by Xu et al ( a = 3.45). 42 T of both α‐crystal and β‐crystal in iPP/β‐CD‐MAH‐La became higher with the incorporation of β‐CD‐MAH‐La, which indicated the β‐nucleating agent could enhance the crystalline of iPP.…”

Polypropylene random copolymer/MWCNT nanocomposites: Isothermal crystallization kinetics, structural, and morphological interpretations

“…Secondary nucleation theory of Hoffman and Lauritzen suggest that the overall crystallization rate should be controlled by nucleation and transport of macromolecules in melt . This theory was used to analyze the nucleating effect of MWCNTs on crystallization of PPCP According to Hoffman–Lauritzen theory, the temperature dependence of the linear growth rate of PPCP can be represented by eq.…”

“…Usually differential scanning calorimetry (DSC) is used to determine such type of thermophysical properties of polymers whereas Avrami and Hoffman‐Lauritzen analysis were used to evaluate the overall crystallization kinetics of polymer. Avrami analysis is based on the assumption that the heat released during crystallization is directly proportional to the relative crystallinity whereas Hoffman‐Lauritzen analysis suggests that the nucleation and movement of the macromolecules were controlled by the crystallization in the melt …”

“…Avrami analysis is based on the assumption that the heat released during crystallization is directly proportional to the relative crystallinity whereas Hoffman-Lauritzen analysis suggests that the nucleation and movement of the macromolecules were controlled by the crystallization in the melt. [6][7][8][9][10][11][12] It is well reported in the literature that the crystallization kinetics of polymer is very much affected by the presence of external materials (filler). The most commonly used fillers include various grades of calcium carbonate, quartz, mica, silica flour, talc, various clays, fibers, and carbon nanotubes (CNTs).…”

Morphology, Crystallization and Dynamical Mechanical Behavior of iPP/Nano-CaCO3Composites

“…Most literature focused on modified nano-CaCO 3 composite and related crystallization kinetics ] [18][19][20][21] . Previous work reported double crystallization behavior in iPP=nano-CaCO 3 composites [21] .…”