iPP Matrix Research Articles

Ultraviolet resistance and antimicrobial properties of ZnO-supported zeolite filled isotactic polypropylene composites

In order to increase the antimicrobial properties and ultraviolet resistance of isotactic polypropylene (iPP), ZnO-supported zeolite particles were prepared and used as multifunctional filler for iPP composites. The ZnO-supported zeolites with different ZnO contents were obtained by treating the mixture of zeolite and zinc acetate by different methods. Atomic absorption spectroscopy, scanning electron microscope and wide-angle X-ray diffraction experiment indicated that the ZnO was formed on the surface of zeolite particles. UV-irradiation results showed that the ultraviolet resistance of ZnO-supported zeolite filled iPP composites is higher than that of iPP composite filled by the same content of micro ZnO. The ZnO-supported zeolite filed iPP composites exhibit higher antimicrobial abilities than ZnO filled iPP composites prepared by directly adding micro ZnO into iPP matrix for the Staphylococcus aureus and Escherichia coli. Incorporation of ZnO and zeolite increases the crystallization temperatures of iPP due to the heterogeneous nucleation of ZnO and zeolite particles. The prepared ZnO-supported zeolite particles have no influence on the crystallization and melting behavior of zeolite filled iPP composites. The ZnO-supported zeolite particles are an effective filler to prepare iPP composites with antimicrobial ability and ultraviolet resistance.

Novel Polypropylene/Inorganic Fullerene-like WS2 Nanocomposites Containing a β-Nucleating Agent: Isothermal Crystallization and Melting Behavior

The isothermal crystallization and subsequent melting behavior of isotactic polypropylene (iPP) nucleated with different nucleating agents (NAs) are investigated. Tungsten disulfide (IF-WS(2)) and N,N'-dicyclohexyl-2,6-naphthalene (NJ) and dual-additive mixtures are introduced into an iPP matrix to generate new materials that exhibit variable α- and β-polymorphism. As shown in previous work, small amounts of IF-WS(2) or NJ have a nucleating effect during the crystallization of iPP. However, the isothermal crystallization and melting behavior of iPP nucleated by dual α(IF-WS(2))/β(NJ) additive systems are dependent on both the NA composition balance and the crystallization temperature. In particular, our results demonstrate that it is possible to obtain any α-phase to β-phase content ratio by controlling the composition of NAs under appropriate isothermal crystallization conditions. The nucleating behavior of the additives can be illustrated by competitive nucleation, and the correlation between crystallization and melting temperatures and relative α- and β-crystals content in iPP in the nanocomposites is discussed.

Microstructure evolution of isotactic polypropylene during annealing: Effect of poly(ethylene oxide)

The microstructure evolution of isotactic polypropylene (iPP) during annealing is reported. A few amount of poly(ethylene oxide) (PEO) which exhibits much lower melt temperature compared with iPP was introduced into iPP in this work. The crystalline structure of iPP was detected using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD), and the relaxation of iPP was characterized using dynamic mechanical analysis (DMA). The variation of PEO morphology was investigated by scanning electron microscopy (SEM). The results show that the crystallization, including the primary crystallization and second crystallization during annealing, as well as the relaxation of iPP matrix is promoted with the presence of PEO.

Preferential distribution of clay layers in iPP/OMMT/PEOc ternary nanocomposites

Isotactic polypropylene (iPP)/organo-montmorillonite (OMMT) nanocomposite was modified by poly(ethylene-co-octene) (PEOc). PEOc-rich domains were well dispersed in the iPP matrix, with narrowly distributed size. OMMT layers were well dispersed, mainly intercalated and partially exfoliated. Compared with the case in the binary composites, many OMMT layers were preferential distributed inside and around the PEOc-rich domains in the ternary composite samples, which formed an enhanced OMMT filler network. The reason for the OMMT preferential distribution was considered to be dragged or wrapped by PEOc-rich domains during sample preparation and phase separation.

A Novel Phenolic Rigid Organic Filler/Isotactic Polypropylene Blend

A novel phenolic rigid organic filler (named K3) was dispersed in isotactic polypropylene matrix (iPP) by melt-mixing process, and a series of K3/iPP blends was prepared with or without maleic anhydride-grafted polypropylene (MAPP) as compatibilizer. The influences of K3 and MAPP on the filler dispersion were studied using Polarized Optical Microscope (POM) and Fourier Transform Infrared Spectroscopy (FTIR). The influences on the modulus of blends were studied by tensile test and Dynamic Mechanical Analysis (DMA). It was found that K3 can be dispersed in iPP matrix in a spherical form and its particles size can be adjusted by MAPP content. The incorporation of K3 and MAPP can obviously improve the Youngs modulus and storage modulus of blends.

Characterization of Isotactic Polypropylene and Hydrogenated Oligocyclopentadiene Blends

) and overall crystallinity of iPP/ HOCP blends decreased as a result of addition of pre-irradiated HOCP resin. Incorporation of HOCP resin in iPP matrix exhibited better mechanical properties, (tensile stress and elongation at break) as compared with blank iPP sample. The dynamic thermal mechanical data showed that the addition of HOCP resin slightly decreased the storage modulus from -100

Rheological and structural details of biocidal iPP-TiO2 nanocomposites

Nanocomposites obtained from incorporation of TiO2 nanoparticles in different amounts, ranging from 0.5 to 5wt.%, into an isotactic polypropylene (iPP) matrix are achieved via a straightforward and cost-effective melting process. These materials exhibit a powerful germicide capability over a wide variety of regular bacteria and other microorganisms widely present in the environment that cause infections and serious illness. The iPP-TiO2 nanocomposites show similar or improved structural characteristics than those of the pure iPP matrix and aspects as important as processability and final mechanical performance seem to be not affected because of the incorporation of these TiO2 nanoparticles. Validation of time–temperature superposition of the molten polymers is observed within the temperature range analyzed. On the other hand, the α polymorph is the one primarily attained for these specimens. Crystallinity and most probable crystallite size are slightly dependent on TiO2 content, both increasing as oxide composition is enlarged.

Influence of Mixing Technique on Microstructure and Impact Properties of Isotactic Polypropylene/ Poly(Cis-Butadiene) Rubber Blends

Isotactic polypropylene/poly(cis-butadiene) rubber (iPP/PcBR vol%: 80/20) blends were prepared by melt mixing with various mixing rotation speeds. The effect of mixing technique on microstructure and impact property of blends was studied. Phase structure of the blends was analyzed by scanning electron microscopy (SEM). All of the blends had a heterogeneous morphology. The spherical particles attributed to the PcBR-rich phase were uniformly dispersed in the continuous iPP matrix. With increase of the mixing rotation speed, the dispersed phase particle's diameter distribution became broader and the average diameter of the separated particles increased. The spherulitic morphology of the blends was observed by small angle light scattering (SALS). Higher mixing rotation speed led to a more imperfect spherulitic morphology and smaller spherulites. Crystalline structure of the blends was measured by wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). The introduction of 20 vol% PcBR induced the formation of iPPβ crystals. Higher rotation speed led to a decrease in microcrystal dimensions. However, the addition of PcBR and the increase of mixing rotation speed did not affect the interplanar distance. The long period values were the same within experimental error as PcBR was added or the mixing rotation speed quickened. The normalized relative degree of crystallinity of the blends slightly increased under lower rotation speeds (30 and 45 rpm) and decreased under higher rotation speeds. The notched Izod impact strength of the blends was enhanced as a result of the increase of mixing rotation speed.

Foaming of linear isotactic polypropylene based on its non-isothermal crystallization behaviors under compressed CO 2

The non-isothermal crystallization behaviors of isotactic polypropylene (iPP) under ambient N 2 and compressed CO 2 (5–50 bar) at cooling rates of 0.2–5.0 °C/min were carefully studied using high-pressure differential scanning calorimeter. The presence of compressed CO 2 had strong plasticization effect on the iPP matrix and retarded the formation of critical size nuclei, which effectively postponed the crystallization peak to lower temperature region. On the basis of these findings, a new foaming strategy was utilized to fabricate iPP foams using the ordinary unmodified linear iPP with supercritical CO 2 as the foaming agent. The foaming temperature range of this strategy was determined to be as wide as 40 °C and the upper and lower temperature limits were 155 and 105 °C, which were determined by the melt strength and crystallization temperature of the iPP specimen under supercritical CO 2, respectively. Due to the acute depression of CO 2 solubility in the iPP matrix during the foaming process, the iPP foams with the bi-modal cell structure were fabricated.

The supermolecular structure of isotactic polypropylene/atactic polystyrene blends

AbstractThe supermolecular structure of binary isotactic polypropylene/atactic polystyrene (iPP/PS) injection‐molded blends were studied by wide‐angle X‐ray diffraction, differential scanning calorimetry, and optical microscopy. The combination of different methods gives a possibility of analysis of relation between the phase transformation in polypropylene and crystallization parameters. Effect of compatibilization of poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) grafted with maleic anhydride (SEBS‐g‐MA) block copolymers in the iPP/PS blends on the structure, nucleation, crystal growth, solidification, and the phase morphology was analyzed. We found that the β‐crystallization tendency of polypropylene matrix can be enhanced by adding atactic polystyrene. However, the incorporation of SEBS‐g‐MA into iPP/PS blends resulted in an important decrease in β‐content of iPP. It is evident that the presence of compatibilizing agent caused a very significant reduction of the α‐spherulite growth rates and the crystal conversion as well as increases of half‐time crystallization in comparison with the iPP/PS systems. The relation between kinetic parameters of crystallization process and polymorphic structure of iPP in blend systems has been satisfactorily explained. Moreover, a strong effect of processing parameters on the β‐phase formation was observed. The results clearly show that at a higher temperature of mold and lower injection speed, the amount of β‐phase of iPP matrix slightly decreases. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Effects of Carbon Black–Carbon Nanotube Complex Fillers on the Properties of Isotactic Polypropylene Nanocomposites

In this study, the reinforcing effects of carbon black (CB) and carbon nanotube (CNT) complex fillers on the properties of isotactic polypropylene (iPP) nanocomposites were investigated using various methods. The surface of the CNTs was modified using a linear alkyl chain in order to create a homogeneous CNT dispersion in the iPP matrix. When the CB content that was incorporated in the iPP matrix increased, the thermal and mechanical properties of the iPP/CB nanocomposites were enhanced. Additionally these enhancements in the properties were similarly induced by introducing a small amount of alkylated CNTs (a-CNTs). In contrast, the CB/a-CNT complex filler was more effective for the iPP nanocomposites than the CB or a-CNT single filler in terms of the thermal stability and the electrical properties. However, the mechanical properties of the CB/a-CNT complex filler incorporated iPP nanocomposites were poorer than the only a-CNT incorporated iPP nanocomposites. Additionally, the complex filler did not overcome the nucleation behavior of the a-CNTs in the re-crystallization of iPP.

Effect of tetra-needle-shaped zinc oxide whisker (T-ZnOw) on mechanical properties and crystallization behavior of isotactic polypropylene

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 5 wt.%. 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.

Crystallization Behavior and Melting Characteristics of Isotactic Polypropylene Nucleated by a Novel Nucleating Agent

The crystalline structure, morphology, and nonisothermal crystallization and melting behavior of isotactic polypropylene (iPP) with and without a novel nucleating agent containing amide group (TMC-328) were investigated with differential scanning calorimetric (DSC), polarized optical microscopy (POM) and X-ray diffraction (XRD). TMC-328 could increase the crystallization temperature and accelerate the crystallization rate of iPP. As an efficient α-form nucleating agent, the addition of TMC-328 could obviously reduce the spherulite size of iPP. There is a critical concentration of TMC-328. When the content of TMC-328 is 0.1%, iPP matrix exhibits the maximum crystallization peak temperature (123 °C) and the maximum crystallinity of 45.0%. With the content of TMC-328 increasing, crystallinity of iPP matrix decreases obviously. XRD measurements indicate that the crystal structure of the α-form of iPP is unaffected by TMC-328.

The Effect of Acid-Treatment of Carbon Nanotubes on the Thermal Kinetics of Isotactic Polypropylene

Isotactic polypropylene (iPP)/maleic-anhydride-grafted polypropylene (PP-g-MA)/raw and acid-treated single-walled carbon nanotube (SWCNT) nanocomposites were prepared in an internal mixer. Thermal and crystallization behaviors of these nanocomposites were evaluated. Thermal properties of the iPP and its nanocomposites were estimated using thermo-gravimetric analysis (TGA) under nonisothermal conditions. The kinetics of nonisothermal degradation of iPP and its nanocomposites were studied using the Friedman model based on the single heating rate method. In terms of onset temperature of degradation (Tonset) and activation energy for decomposition (E), it was found that raw and acid-treated SWCNTs provide improved thermal stability to the iPP matrix. The respective activation energy values were determined to be 84, 94, and 96 kJ/mol for iPP, iPP/SWCNT, and iPP/A-SWCNT, respectively. Differential scanning colorimetry (DSC) was used to study the isothermal crystallization kinetics of iPP and its nanocomposites. During isothermal crystallization, relative crystallinity developed with a time dependence described by the Avrami equation, with the exponent n = 3. Further analysis based on the Hoffman–Lauritzen theory revealed that the surface free energy (σe) for the nanocomposites was lower than that of iPP.

In situ fibrillation of polyamide 6 in isotactic polypropylene occurring in the laminating‐multiplying die

AbstractThe polyamide 6 (PA6)/isotactic polypropylene (iPP) in situ fibrillation composites are prepared by a novel extrusion die with an assembly of laminating‐multiplying elements (LMEs). The scanning electron micrographs illustrate that the dividing‐multiplying processes in LMEs elongate, break, and stabilize the dispersed PA6 phase in the iPP matrix along the flowing direction (FD). The morphology development of PA6 with different LME numbers greatly affects the rheological properties, crystalline behaviors, and mechanical properties. The dynamic rheological test performed at 195°C shows that the increased spatial restriction of the high‐aspect‐ratio PA6 particles increases the viscoelastic moduli, complex viscosity, and relaxation time. The crystalline analysis reveals that the heterogeneous nucleation becomes predominant and the transcrystalline morphology is observed in those samples produced by more LMEs. The tensile tests indicate that both, breaking strength and elongation, enhanced simultaneously because of the fibrillation of dispersed phase and the improvement in interfacial adhesion between the fibers and the matrix. Copyright © 2009 John Wiley & Sons, Ltd.

Towards a new generation of polymer nanocomposites based on inorganic nanotubes

We report for the first time the preparation and characterization of novel polymer nanocomposites based on inorganic nanotubes (INTs) processed by an advantageous melt-processing route. This strategy offers an attractive way to combine the merits of organic and inorganic materials into novel polymer/INTs and opens new perspectives for large scale production. The polymer matrix selected here is iPP and the inorganic nanofillers are MoS2 nanotubes. The morphological and structural investigations confirm the successful dispersion of the INT-MoS2 into the iPP matrix. A significant enhancement of the thermal stability of iPP and a nucleating effect of the INTs comparable to CNTs has been observed. The excellent dynamic mechanical data demonstrates the high performance of these novel nanocomposites for industrial applications.

Reinforcing and toughening of polypropylene with self‐assembled low molar mass additives

AbstractThis study presents a new approach to reinforce and toughen thermoplastic polymers by using a low molecular weight additive; calcium stearate (CaSt2). The method involves melt blending isotactic polypropylene (iPP) and CaSt2 at a process temperature where the CaSt2 reduces the process viscosity through its characteristic morphology. Once the mixture cools, CaSt2 coalesces and solidifies to develop reinforcing domains. Differential scanning calorimeter experiments demonstrate a significant reduction in the percent crystallinity of iPP with the addition of CaSt2. The changes in yield strength and modulus suggest a synergistic effect between the CaSt2 domains and iPP. Addition of 10% CaSt2 increases the fracture energy by almost four‐fold with a simultaneous increase in the elastic modulus. The melt flow rate of the composite is dramatically increased with CaSt2 incorporation. Reduction in coefficient of thermal expansion was also observed. Simultaneous positive effects of CaSt2 filler is attributed to its rich mesomorphic structure and its interaction with the iPP matrix. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Flow induced orientated morphology and properties of nanocomposites of polypropylene/vapor grown carbon fibers

Nanocomposite filaments composed of isotactic polypropylene (iPP) and vapor grown carbon fibers (VGCF) were prepared by melt mixing extrusion, followed by melt drawing. The effect of composition and flow on the morphology was investigated by X-ray diffraction and high resolution scanning electron microscopy. Apparently in the drawn filaments, the presence of nanofibers resulted in a higher degree of orientated morphology and – as revealed by differential scanning calorimetry – higher degrees of crystallinity and crystallization kinetics enhancement. The amount of the orientated crystals increased as a result of VGCF addition, suggesting that the nanofibers obstructed the motion of polymer chains after the cessation of stretching force resulting in the delayed relaxation of stretched polymer segments. Significant stiffness improvements were observed due to the nanofibers and high draw ratios of the filaments. These results indicate that the orientated VGCF aligned in the flow direction, joined by fiber-induced crystallization of the surrounding iPP matrix, generate a strong stiffening effect.

Effect of Malonic Acid/Calcium Stearate Bicomponent Nucleator on the β-Crystalline Formation in Isotactic Poly(propylene)

Abstract The effect of a new bicomponent β-nucleator composed of malonic acid (MA) and calcium stearate (CaSt) on the formation of the β-crystalline form in isotactic polypropylene (iPP) has been investigated. It has been found that the relative content of the β-crystalline form (k value) of iPP notably increases with the addition of the MA/CaSt mixture, and it attains a maximum value of 0.94 at 0.15% MA/0.30% CaSt. For iPP nucleated with the bicomponent nucleator, the spherulitic size decreases continuously with increasing CaSt dosage. FTIR analysis has shown that an “in situ” reaction may occur between MA and CaSt during melt blending, yielding an effective β-nucleator (calcium malonate, CaMt). The β-nucleation efficiency of an MA/CaSt mixture is higher than that of CaMt itself; this may be ascribed to greater dispersion of the “in situ” produced CaMt in the iPP matrix through the assistance of the CaSt residue and the stearic acid.

Morphology and mechanical properties of binary blends of polypropylene with statistical and block ethylene‐octene copolymers

AbstractIn the present work, statistical (EOCs) and block (OBCs) ethylene‐octene copolymers, with similar densities and crystallinities, were used as impact modifiers of isotactic polypropylene (iPP), and the toughening effects of these two types of elastomers were compared. The viscosity curves of EOCs were similar to those of OBCs with equivalent melt flow rate (MFR), enabling a comparison of the viscosity ratio and elastomer type as independent variables. No distinct differences on the crystal forms and crystal perfection of iPP matrix in various blends were observed by thermal analysis. Morphological examination showed that OBCs form smaller dispersed domains than EOCs with similar MFRs. The flexural modulus, yield stress, stress and strain at break showed the same variation tendency for all the investigated polypropylene/elastomer blends. However, the room temperature Izod impact toughness of iPP/OBC blend was higher than that of iPP/EOC blend containing elastomer with the similar MFRs. The experimental results indicated that the compatibility of iPP/OBCs was much higher than that of iPP/EOCs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011