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The foaming of PP has encountered challenges because of its low melt strength and semi-crystalline characteristics. Introducing long chain branching (LCB) onto the PP backbone and the addition of particles as cell nucleating agent are the commonly used methods to improve the cell structure of PP foams. In this paper, clay-supported sodium benzoate (NaB-OMMT) was prepared from Na-montmorillonite (Na-MMT) via the partial ion exchange reaction with surfactant and subsequent reaction with benzoic acid. The as prepared NaB-OMMTs were then applied to prepare LCBPP/NaB-OMMT nanocomposites and their foams. The dispersion state of clay, crystallization behaviors and rheological properties of the nanocomposites, as well as the cell structure and compression properties of the foams were investigated. The results show that clay layers are mostly exfoliated in the nanocomposites with low NaB-OMMT content, while intercalated layers dominant with the content reaches 2% or higher. The melting temperature of the nanocomposites decreases and the crystallinity increases, while the spherulite size decreases compared to LCBPP. The melt viscosity and elasticity of nanocomposites increase significantly when the content of NaB-OMMT reaches 2% or higher. LCBPP/NaB-OMMT nanocomposites foams exhibit higher cell density, smaller cell size and its standard deviation. Therein, the foam with 1% of NaB-OMMT shows the maximum cell density and the minimum cell size. It is concluded that the cell structure of the foam is highly dependent on the content, dispersion state and structure of the cell nucleating agent. When NaB is supported on well dispersed and exfoliated clay layers, the cell nucleation efficiency is significantly enhanced. The compression properties of the foams depend on their cell structures and exhibit the similar variation trend with the latter with the content of NaB-OMMT increasing. Graphical Abstract [ABSTRACT FROM AUTHOR]

PP-g-malic anhydride (MAH)/styrene (St) was prepared by a twin-monomer solid phase gratting method. The optimum condition was determined by orthogonal experiments with a reaction temperature of 120 °C, a reaction time of 1 h, a St/MAH molar ratio of 1.2 = 1, a MAH/PP mass ratio of 0.14/1, and a BPO/PP mass ratio of 0.02/1. The characterization results of FTIR and NMR spectroscopy indicated that MAH and styrene were successfully grafted into PP by free radical copolymerization. DSC and XRD investigations indicated that PP presented α-form crystals without any changes before and after gratting. However, the crystallinity degree of PP decreased, and its crystallization temperature increased. As a compatibilizer, the incorporation of PP-g-MAH/St enhanced the impact strength of PP compounds. [ABSTRACT FROM AUTHOR]

ABSTRACT Improvement of mechanical and thermal properties is always the goal of high-performance general plastic for engineering applications. Herein, isotactic polypropylene/glass fiber/tetrapod-shaped zinc oxide (iPP/GF/T-ZnOw) composites are developed via melt-extrusion on twin-screw extruder. To improve the distribution of T-ZnOw in iPP matrix, T-ZnOw is first modified by various silane coupling agents and its structure is characterized by scanning electron microscopy, Fourier transform infrared spectra, and X-ray diffraction (XRD). The optimized treatment condition is determined via comparison of activation index. The introduction of GF and T-ZnOw could improve the mechanical properties including tensile strength, elastic modulus, flexural strength, flexural modulus, and impact strength, indicating that the surface modification and compatibilizer could enhance the interfacial interaction of iPP/GF/T-ZnOw composites. Moreover, XRD and differential scanning calorimentryresults show that T-ZnOw as a novel β-nucleating agent could induce the formation of β-crystal and the existence of GF counteracts the formation of β-crystal induced by T-ZnOw. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44217. [ABSTRACT FROM AUTHOR]

β-nucleated long chain branched (LCB) polypropylene random copolymers (PPRs) were prepared via reactive extrusion by introducing β nucleating agent (NA), dicumyl peroxide (DCP) and various contents of 1, 6-Hexanediol diacrylate (HDDA) into PPR. Results of Fourier infrared spectroscopy (FTIR) and the rheological properties demonstrate the existence of LCB polypropylene. Mechanical properties including impact strength, tensile strength and elongation at break were studied. The crystal structure, morphology and crystallization behavior were investigated via wide-angle X-ray diffraction (WAXD), polarized light microscopy (PLM) and differential scanning calorimetry (DSC). Non-isothermal crystallization kinetics using the Jeziorny method was also studied. The results show an increased LCB degree with increasing HDDA amount. For the sample with a moderate LCB level, synergistic toughening effect of NA and LCB is achieved without deterioration of yield strength or elongation at break, partially because of its higher β-phase content and much smaller spherulite size. It exhibits the minimum values of T c and Z c1 , and the maximum values of t 1/2 and n 1 in the primary stage of crystallization, regardless of the cooling rate, indicating a slower crystallization rate and more complicated nucleation and crystal growth model. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel flame-retardant synergist, chitosan/urea compound based phosphonic acid melamine salt (HUMCS), was synthesized and characterized by Fourier transform infrared spectroscopy and 31P-NMR. Subsequently, HUMCS was added to a fire-retardant polypropylene (PP) compound containing an intumescent flame-retardant (IFR) system to improve its flame-retardant properties. The PP/IFR/HUMCS composites were characterized by limiting oxygen index (LOI) tests, vertical burning tests (UL-94 tests), microscale combustion calorimetry tests, and thermogravimetric analysis to study the combustion behavior and thermal stability. The addition of 3 wt % HUMCS increased the LOI from 31.4 to 33.0. The addition of HUMCS at a low additive amount reduced the peak heat-release rate, total heat release, and heat-release capacity obviously. Furthermore, scanning electron micrographs of char residues revealed that HUMCS could prevent the IFR-PP composites from forming a dense and compact multicell char, which could effectively protect the substrate material from combusting. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40845. [ABSTRACT FROM AUTHOR]

Abstract: Isotactic polypropylene (iPP) composites with unmodified and modified tetra-needle-shaped zinc oxide whisker (T-ZnOw) were prepared via melt blending in a twin-screw extruder. The mechanical properties, thermal properties, morphology and crystallization behavior were investigated. The mechanical properties of iPP with T-ZnOw modified by silane based coupling agent were much better than that of iPP with unmodified T-ZnOw. The reason was that the interfacial interaction between T-ZnOw and iPP matrix became stronger when T-ZnOw was modified by coupling agent. Besides, the addition of T-ZnOw improved thermal properties of iPP, including heat deflection temperature and thermal degradation temperature. Furthermore, wide angle X-ray diffraction (WAXD) results showed that T-ZnOw can be used as a novel β-nucleating agent, and the relative content of β-crystal was 0.38 when T-ZnOw content was 5wt.%. iPP/T-ZnOw composites were found to exhibit higher crystallization temperature, smaller spherulites, and faster crystallization rate than those of pure iPP, indicating that T-ZnOw played a role of nucleating agent on the crystallization of iPP and could induce accelerated crystallization. [Copyright &y& Elsevier]

Abstract: Non-isothermal crystallization kinetics of isotactic polypropylene (iPP) was simulated with the assumption that the non-isothermal crystallization process was composed of some finite isothermal crystallization processes, while each isothermal crystallization process consists of three main steps—induction, nucleation and crystal growth. In the simulation, induction time was taken into account, allowing one to make predictions on the start of the non-isothermal crystallization of iPP; nuclei density was treated as a function of temperature; the Hoffman–Lauritzen theory was employed to describe the spherulite growth rate varied with temperature, and the relative crystallinity was determined by the equation of Kolmogorov. Finally, model prediction was verified by quantitative comparison between the theoretical results with the experimental results. [ABSTRACT FROM AUTHOR]

Ca-montmorillonite (Ca-MMT) was first modified with different amount of two different kinds of surfactants to obtain organo-montmorillonites (OMMTs) directly via ion exchange between Ca 2+ and alkyl ammonium cations. Then remained Ca 2+ in OMMTs was reacted with pimelic acid (HA) to obtain CaHA-OMMTs. PP/CaHA-OMMT composites were prepared. Results of FT-IR demonstrate the existence of long-chain alkyl in OMMTs, and CaHA in CaHA-OMMTs. The reaction between HA and OMMT could lead to an increase in d-spacing value of clay. CaHA-OMMTs with high CaHA contents and obviously increased d-spacing values were obtained. Results of WAXD and TEM show exfoliated clay platelets in PP/CaHA-OMMT composites. The obviously increased T c , and the high β-phase content in PP/CaHA-OMMT composites demonstrate the high β-nucleation efficiency of CaHA-OMMTs. Composites with higher content of β-phase epitaxial crystallized on exfoliated clay platelets display largely improved impact strength. [ABSTRACT FROM AUTHOR]

Abstract: To improve both the mechanical and thermal properties of kaolin/polypropylene (PP) composites, kaolin was modified by using 3-(trimethoxysilyl) propylmethacrylate (YDH-570) as a coupling agent to form polymerizable particle. Styrene was radically polymerized through the immobilized vinyl using benzoyl peroxide (BPO) as an initiator. Fourier transform-infrared (FTIR) spectroscopy, particle size distribution, X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA) well demonstrated that the kaolin–polystyrene particles were successfully synthesized via in-situ polymerization. While the modified kaolin and raw kaolin were introduced into the PP matrix, it could be concluded that modified kaolin/PP composites have better mechanical and thermal properties than raw kaolin/PP composites, and these improvements were attributed to the desirable dispersion of kaolin in PP matrix. [Copyright &y& Elsevier]

Abstract: To improve the thermal and mechanical properties of isotactic polypropylene (iPP), iPP/Kevlar fiber (KF)/polyamide 6 (PA6) composites were prepared via the melt-extrusion method on twin-screw extruder. Kevlar fiber was modified with caprolactam using toluenediisocyanate (TDI) as bridge. The microstructure of modified KF was successfully characterized by Fourier transform infrared (FT-IR), X-ray photoelectron spectrometer (XPS) and scanning electron microscopy (SEM), the results showed that KF was bonded with caprolactam and became coarser. Then the modified KF was introduced into iPP, the composites have better mechanical and thermal properties, implying that modification of KF was helpful to improve the interfacial interaction of iPP/KF/PA6 composites. Besides, the crystallization curves indicated that crystallization behavior of PA6 in the composites was homogeneous and fractional. Furthermore, compatibilizer content played an important role in the mechanical and thermal properties of composites. [Copyright &y& Elsevier]