Preparation Of Polypropylene Research Articles

Preparation of polypropylene single‐polymer composites by injection molding

ABSTRACTThe hot compaction process is still the principle method to produce single‐polymer composites (SPCs) at present, which limits the industrial mass production of SPCs. In this article, an approach of preparing SPCs by injection molding was demonstrated. Polypropylene (PP) SPCs were prepared at different temperature and pressure. The flexural properties of the PP SPCs were tested. The optimum processing parameters, injection pressure of 140 MPa and nozzle temperature of 220°C were obtained. Flexural strength of the PP SPCs reached up to 43.3 MPa, which is 54.2% higher than that of nonreinforced PP. Flexural strength can be promoted by raising the injection pressure and nozzle temperature. The morphology of the fibers in the PP SPCs was investigated by optical microscope and scanning electron microscopy techniques. The matrix melt was able to penetrate into fiber webs under appropriate temperature and pressure, good interfacial compatibility and bonding properties were obtained. As the injection and holding pressure increased, the penetration capacity could be improved and the arrangement of fibers tended to be closer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2176–2183, 2013

Functionalized multi-walled carbon nanotubes with stereospecific Ziegler-Natta catalyst species: Towards facile in situ preparation of polypropylene nanocomposites

Multi-walled carbon nanotubes (MWCNTs) were functionalized with a stereospecific Ziegler-Natta catalyst species for in situ preparation of polypropylene (PP)/MWCNT nanocomposites. The functionalization process involved initially treating MWCNTs containing a few (∼3.0% w/w) surface hydroxyl groups (MWCNT-OH) with an excess amount of Grignard reagent followed by further reaction with TiCl4. Triethylaluminum (TEA) and dimethoxydiphenylsilane (DDS) were used as co-catalyst and external electron donor, respectively. The resulting MWCNTs (MWCNT/Mg/Ti) only behaved as a fair isospecific Ziegler-Natta catalyst, promoting propylene polymerization at a moderate rate and resulting in PP with moderate isotacticity indices (76.4–91.0%). To improve the catalytic performance, the electron-donating reagent 9,9-bis(methoxymethyl)fluorine (BMMF) was added into the MWCNT functionalization process, incorporating BMMF into the catalytic material and simultaneously reducing the quantity of TiCl4 immobilization. The BMMF-incorporated functionalized MWCNTs (MWCNT/Mg/BMMF/Ti) produced PP with a high isotacticity index (92.0%) without the use of an external electron donor. PP with an isotacticity index greater than 98% was achieved when DDS was used as external electron donor during the polymerization process.

Studies on morphology and mechanical properties of dispersing intercalated silane montmorillonite in polypropylene matrix

AbstractWe used a plastograph‐mixer by the twin‐screw mixed method to obtain the standard shaped specimens of polymer‐clay nanocomposites (PCN) to prepare polypropylene (PP)/silane montmorillonite (MMT) nanocomposites pellets, grafting with two kinds of different surfactant—hard grafting agent maleic anhydride (MA) or soft grafting agent thermoplastic polyolefin elastomers (TPO). The chemical structure and polymer morphology of these as‐synthesized PCN specimens were characterized by a wide‐angle powder X‐ray diffraction (XRD) and a scanning electron microscopy (SEM). In addition, we prepared these experimental specimens in order to probe into their mechanical properties. The tests used were: layer distance of PCN, tensile, impact, shore‐hardness, wearing tests, and so on. In addition, we used XRD to make the characterization analysis, and compare it to scatter and layer‐distance. It was found that when the MA is increased into the MMT, the layer‐distance at 3 wt% increased from 2.11 nm to 3.54 nm; when increasing the TPO into the MMT, layer‐distance at 3 wt% increased to the 3.28 nm. For the mechanical property, it was found that these specimens grafted with the MA have the following results: in the tensile test, the MMT weight percentage of 1 wt% had the best result, increasing by 3.2%. In the shore hardness test, the MMT of 3 wt% strengthens by 5.41%. In addition, the mechanical property of the specimens that grafted to the TPO decreased almost immediately at 1 wt%, but increased at 3–5 wt% trends. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Water-assisted extrusion as a novel processing route to prepare polypropylene/halloysite nanotube nanocomposites: Structure and properties

Naturally occurring halloysite nanotubes (HNTs) are used to prepare Polypropylene (PP)/HNTs nanocomposites using a novel “one step” water-assisted extrusion process with and without the use of a PP-graft-maleic anhydride (PP-g-MA) as compatibilizer. In order to analyze the influence of PP-g-MA and/or water injection on the HNTs dispersion and therefore on nanocomposite properties, structural analysis (SEM and TEM) is combined with rheological and thermo-mechanical experiments. The best clay dispersion is obtained when compatibilizer and water injection are combined together (synergistic effect). As a consequence, the linear viscoelastic properties and the dynamic storage modulus are dramatically enhanced for this system. A mechanism explaining the interaction between HNTs and PP-g-MA in presence of water is proposed. The thermal stability and flame retardant property are also investigated. Thermal analyses reveal two opposite effects of HNTs on the thermal behaviour of PP. A surface catalytic action of the halloysite speeds up thermal degradation of PP. However, this effect is reduced with improved HNTs dispersion, presumably via an entrapment mechanism of the decomposition products inside the lumens. Finally, cone calorimeter results show that low flammability of nanocomposites is only achieved when combining water injection and PP-g-MA. In view of these results, PP/HNTs nanocomposites prepared using this novel processing route are promising candidates for flame retardant applications.

Preparation of polypropylene (PP)/ethylene octene copolymer (EOC) thermoplastic vulcanizates (TPVs) by high energy electron reactive processing

Thermoplastic vulcanizates (TPVs) based on 50/50 composition of PP/EOC blend were prepared by electron induced reactive processing. To facilitate dynamic crosslinking in the PP/EOC blend, a 1.5 MeV electron accelerator was directly coupled to an internal mixer to induce chemical reactions via high energy electrons under dynamic conditions of melt mixing process. This kind of setup has been conceptualized for the first time in our laboratory and termed as electron induced reactive processing (EIReP) technique. Mechanical, morphological, and rheological properties of PP/EOC TPVs were studied with special reference to the exposure time (16–64 s) keeping absorbed dose (100 kGy) and electron energy (1.5 MeV) invariable. Chain scission dominates over chain crosslinking in both EOC as well as PP phases with the increase in exposure time. The primary factor is found to be the predominance of oxidative degradation during electron induced reactive processing in air atmosphere. The above observation was supported by Fourier Transform Infrared analyses and gel content values. Furthermore, it was found that mechanical properties depend not only on the extent of degradation in the blend system but also on the state and the mode of dispersion of the blend components.

Nanosilica Addition Dramatically Improves the Cell Morphology and Expansion Ratio of Polypropylene Heterophasic Copolymer Foams Blown in Continuous Extrusion

Currently, the preparation of polypropylene (PP) foam with a well-defined cell structure and a high expansion ratio is receiving increased attention. However, the present technical problems such as poor cell nucleation ability and weak melt strength of polymer resin, hinder the broader use of linear PP in foam production. In this study, a PP heterophasic copolymer with a linear structure was selected together with nanosilica to challenge the fabrication of PP foam with uniform cell structure, high cell density, and a high expansion ratio using CO2 as a physical blowing agent. Scanning electron microscopy (SEM) observation indicated that silica particles tended to aggregate in the PP matrix, but the multisilica aggregates with sizes from 80 to 350 nm were well dispersed in PP because of the addition of a coupling agent (CA). PP foam exhibited poor cell morphology and low cell densities of ca. 104–5 cells/cm3 at different die temperatures. An introduction of a small amount of nanosilica, 0.5 wt % and 1 wt %, dramatically improved the foaming behavior of PP, where the cell structure distribution of the resultant foams was uniform, and the cell density and foam expansion were high (i.e., 108–9 cells/cm3 and 16.9–19.5, respectively). Furthermore, the presence of nanosilica clearly broadened the foaming window of PP. By further increasing silica content, however, the foaming behavior of PP/silica nanocomposites became poor, especially at slightly higher die temperatures (i.e., above 140 °C), even though a high silica loading increased the number of heterogeneous nucleation sites. The effect of foaming on the dispersion of nanosilica in the PP matrix was also investigated.

Grafting of telechelic poly(lactic-co-glycolic acid) onto O2 plasma-treated polypropylene flakes

In this work, we described a facile approach to preparing polypropylene (PP) surface functionalized with telechelic poly(lactic-co-glycolic acid) (HO-PLGA-COOH). The PP flakes were first treated with oxygen plasma and then grafted with different molecular weight PLGA (Mw = 50, 100, and 300 K) in dry dichloromethane solution with the addition of phosphorus pentachloride (PCl5). The attenuated total reflectance-Fourier transform infrared (ATR–FTIR) spectroscopy measurements were used to characterize the composition of the PP surface. The appearance of 1756 cm−1 for carbonyl (CO) stretching and 1090 cm−1 for COC and the morphologies observations by atomic force microscopy show that PLGA graft covered the surface of PP flake. The IR intensity at 1756 cm−1 increases with the decreasing Mw of PLGA, and the molecular weight of PLGA also influence the grafting of PLGA on PP. The contact angle was used to monitor the changes in hydrophilicity of PP flake surface along the treatment procedure. PLGA-grafted PP (PP-g-PLGA) was eventually obtained. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Preparation and mechanical properties of polypropylene / montmorillonite nanocomposites - After grafted with hard/soft grafting agent

Using a plastograph-mixer by the twin-screw mixed method to obtain the standard shaped specimens of polymer-clay nanocomposites (PCN), to prepare polypropylene (PP) / montmorillonite (MMT) nanocomposites pellets, grafting with two kinds of different surfactant − maleic anhydride (MA) or thermoplastic polyolefin elastomers (TPO). The chemical structure and polymer morphology of these as-synthesized PCN specimens were characterized by wide-angle powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). In addition, we prepare these experimental specimens in order to probe into its mechanical properties. These tests used are: layer distance of PCN, tensile, impact, shore-hardness, wearing tests, and so on. In addition, use XRD to make the characterization analysis, compare it to scatter and layer-distance. It is found that increasing the MA into the MMT, layer-distance at 5 wt% increase from 2.09 nm to 3.94 nm; and increase the TPO into the MMT, layer-distance at 1 wt% increase to the 3.27 nm. For the mechanical property, it is found that these specimens graft the MA have the following results: in the shore hardness test, the MMT weight percentage 5 wt% has the best result, increased by 51.2%. In the wearing test, the MMT 3 wt% strengthens by 81.48%. In addition, the specimens that graft the TPO, in the tensile test, increased by 5.79% have the best result.

Water-assisted extrusion of polypropylene/clay nanocomposites: A comprehensive study

Water-assisted extrusion process has been used to successfully prepare polypropylene (PP)/clay nanocomposites with high degree of clay delamination and markedly improved rheological, thermal and mechanical properties. PP-graft-maleic anhydride (PP-g-MA)-based nanocomposites and masterbatches were synthesized from untreated clay and organoclay, respectively, and fully characterized. The effects of using high-shear rates and water injection during the melt-compounding were examined. A mechanism explaining the formation of such nanocomposites is then proposed. The best clay dispersion and properties improvements of PP-g-MA/organoclay nanocomposites and masterbatches were obtained using high-shear rates and water injection (synergy effect). PP-based nanocomposites were then synthesized by dilution of PP-g-MA-based masterbatches into neat PP. For comparison, nanocomposites were also prepared by a one-pot process where PP, PP-g-MA and organoclay are directly melt-blended with or without water injection. The nanocomposites prepared by dilution into PP of a masterbatch prepared through water-assisted extrusion showed the highest clay dispersion and consequently the best thermal, mechanical and rheological properties.

Preparation and radiation effect on composite films containing both polypropylene and novel phthalocyanines with functionalized bulky phenoxy groups

AbstractNovel symmetrically substituted 2,3,9,10,16,17,23,24‐octa(p‐methylphenoxy)phthalocyanines [(p‐methylphenoxy)8PcM (3–5,where Pc is phthalocyanine and M is H2or one of its metal complexes, Mg or Zn, respectively)] were synthesized and characterized as target precursors for the preparation of polypropylene (PP)/Pc composite films [PP/(p‐methylphenoxy)8PcM (labeledI–IIIfor composites with Pcs3–5,respectively)]. We prepared the composites by embedding the Pcs into the PP using the cast method. The effects of γ irradiation on the physicochemical properties of PP after the formation of the PP/(p‐methylphenoxy)8PcM composite films (I–III) were studied. The structure of the prepared composite series (I–III) was characterized with Fourier transform infrared spectroscopy. For compositeIII,minor differences in the Fourier transform infrared spectra were observed after irradiation treatment; these occurred because the zinc Pc additives in the repeating units of compositeIIIacted as stabilizing elements against γ‐irradiation‐induced degradation because of the delocalization of excitation energy in the double and aromatic units and also because of the large ionic radius of Zn in compositeIIIcompared with those in compositeII(containing Mg) and compositeI(metal‐free). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Double Functions of Chlorinated Carbon Nanotubes in Its Combination with Ni2O3 for Reducing Flammability of Polypropylene

Chlorinated carbon nanotubes (CNT-Cl) and its combination with Ni2O3 were used to prepare polypropylene (PP) composites via melt mixing The cone calorimetry and TGA results showed that both the flame retardancy and the thermal stability of the composites containing CNT-Cl were better than the samples containing unchlorinated CNTs NMR measurements confirmed that CNT-Cl could react with the double bond of degradation products at high temperature. Furthermore, the role of CNT-Cl in the combination between CNT-Cl and Ni2O3 was investigated by carbonization experiments and rheology measurements. The results demonstrated that CNT-Cl could significantly promote the carbonization of degradation products of PP catalyzed by nickel catalyst during combustion In contrast, the combination between unchlorinated CNTs and Ni2O3 could not promote the carbonization of degradation products of PP compared to the case containing Ni2O3 alone This was attributed to Cl radicals releasing from CNT-Cl, which worked as a catalyst to accelerate dehydrogenation-aromatization of degradation products of PP and promoted the carbonization of degradation products catalyzed by nickel catalyst

Polypropylene-based nano-composite formation: Delamination of organically modified layered filler via solid-state processing

Solid-state processing for the preparation of polypropylene (PP)-based nano-composites having finely dispersed layered fillers was conducted. The mixture of PP and organically modified layered filler (OMLF) (95:5 wt./wt.) was subjected to the processing using alumina mortar heated 65 °C, below Tm of PP (i.e., PP is still at the solid-state), and ground for 8 h before melt compounding. On X-ray diffraction, the d(001) peak of OMLF was broaden and peak position shifted slightly. The mixture prepared by solid-state processing exhibited disorder and delaminated layer structure with the thickness of 3–7 nm into PP matrix through TEM observations. On the contrary, nano-composite prepared by melt compounding at 180 °C for 3 min (without solid-state processing) showed the large stacked silicate layers in the PP matrix. Furthermore, instead of using alumina mortar, we carried out solid-state processing using internal mixer. X-ray diffraction pattern and TEM observation exhibited similar results. The solid-state processing led to delaminate of the silicate layers and attained the discrete dispersion.

Microstructure and Properties of Polypropylene/Carbon Nanotube Nanocomposites

In the last few years, great attention has been paid to the preparation of polypropylene (PP) nanocomposites using carbon nanotubes (CNTs) due to the tremendous enhancement of the mechanical, thermal, electrical, optical and structural properties of the pristine material. This is due to the unique combination of structural, mechanical, electrical, and thermal transport properties of CNTs. However, it is well-known that the properties of polymer-based nanocomposites strongly depend on the dispersion of nanofillers and almost all the discussed properties of PP/CNTs nanocomposites are strongly related to their microstructure. PP/CNTs nanocomposites were, mainly, prepared by melt mixing and in situ polymerization. Young’s modulus, tensile strength and storage modulus of the PP/CNTs nanocomposites can be increased with increasing CNTs content due to the reinforcement effect of CNTs inside the polymer matrix. However, above a certain CNTs content the mechanical properties are reduced due to the CNTs agglomeration. The microstructure of nanocomposites has been studied mainly by SEM and TEM techniques. Furthermore, it was found that CNTs can act as nucleating agents promoting the crystallization rates of PP and the addition of CNTs enhances all other physical properties of PP. The aim of this paper is to provide a comprehensive review of the existing literature related to PP/CNTs nanocomposite preparation methods and properties studies.

Achieving Highly Effective Non-biofouling Performance for Polypropylene Membranes Modified by UV-Induced Surface Graft Polymerization of Two Oppositely Charged Monomers

A major problem in membrane technology for applications such as wastewater treatment or desalination is often the loss of membrane permeability due to biofouling initiated from protein adsorption and biofilm formation on the membrane surface. In this study, we developed a relatively simple and yet versatile approach to prepare polypropylene (PP) membrane with highly effective non-biofouling performance. Copolymer brushes were grafted to the surface of PP membrane through UV-induced polymerization of two oppositely charged monomers, i.e., [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TM) and 3-sulfopropyl methacrylate potassium salt (SA), with varying TM:SA molar ratios. Surface analysis with scanning electron microscope (SEM) clearly showed the grafted copolymer brushes on the membrane surfaces and that with X-ray photoelectron spectroscope (XPS) revealed a similar TM:SA ratio of the grafted copolymer brushes to that of the monomer solution used for the polymerization. Water contact angle measurements indicated that the hydrophilicity of the membrane surfaces was remarkably improved by the grafting of the TM/SA copolymer brushes, with the lowest water contact angle of 27 degrees being achieved at the TM:SA ratio of around 1:1. Experiments for antiprotein adsorption with bovine serum album (BSA) and lysozyme (LYZ) and antibiofilm formation with Escherichia coli (E. coli) demonstrated a great dependence of the membrane performance on the TM:SA ratios of the grafted copolymer brushes. It was found that the characteristics of the surface charges of the membrane surfaces played a very important role in the non-biofouling performance, and the membrane surface with balanced positive and negative charges showed the best non-biofouling performance for the proteins and bacteria tested in this study.

Preparation of extruded melt‐mixed polypropylene/montmorillonite nanocomposites with inline monitoring

AbstractThis article advances the use of an inline optical detector to monitor the disaggregation of the montmorillonite (MMT) clay tactoids during the preparation of polypropylene (PP)/MMT nanocomposites via polymer melt compounding. During the exfoliation of the tactoids their size are reduced below the minimum particle size to produce light extinction and so, the signal of the inline detector reduces as the nanosize composite is formed. The measurement is done at the transient state with the MMT clay added as a pulse with constant weight into the PP extrusion melt flow and followed by the optical detector. The data comes out as the common residence time distribution curves having its maximum intensity related to the tactoids average particle size, keeping all other variables constants. The light extinction was measured for composites with different clays (Cloisite® 15A, 30B, Na+, and Sintered 20A) using the same PP grafted with maleic anhydride compatibilizer. The dissaglomeration/exfoliation efficiency increases as: ‘‘Sintered 20A’’ < ‘‘Na+ clay’’ < ‘‘organo‐modified clay’’ < ‘‘organo‐modified clay + compatibilizer’’. The best result is obtained using Cloisite® 15A and Cloisite® 20A following the expected reduction of the particle size obtained during a nanocomposite melt processing. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

Preparation of polypropylene‐graft‐cardanol by reactive extrusion and its composite material with bamboo powder

AbstractThe polypropylene‐graft‐cardanol was prepared by reactive extrusion, which is solvent‐free melt process, continuous processing, and controllable over residence time. The effect of monomer and initiator concentration on grafting ratio, grafting efficiency, and melt flow index (MFI) was also studied. The yield was quantified by UV–vis spectrometer. The chemical structure was investigated by infrared spectroscopy and gel ratio. A possible mechanism was supposed. The particular structure of cardanol can retain the MFI value of matrix resins and prevent polypropylene (PP) from being decomposed. The grafting ratio could be easily obtained from an experimental formula deduced from the linearity relationship between grafting ratio and MFI. The effect of cardanol grafted onto PP on the compatibility of PP and bamboo powder was studied by contact angle measurements, scanning electron microscopy, and tensile properties test. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Preparation of polypropylene fiber/banana fiber composites by novel commingling method

AbstractShort natural fiber thermoplastic composites are usually fabricated by melt mixing or solution mixing followed by conventional methods like injection molding or compression molding. In melt mixing, the fibers are subjected to high shear and this damage the natural fiber. In solution mixing, the use of the organic solvent is essential and its use is hazardous. Development of a novel method commingling to prepare polypropylene (PP)/short natural fiber composite is the main objective of this study. The influence of fiber loading on the mechanical properties of the composites prepared by the above method has been evaluated. The applications and limitations of several equations to predict physical properties such as tensile strength and modulus of the composites have been described. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Morphology and properties of halloysite nanotubes reinforced polypropylene nanocomposites

AbstractHalloysite nanotubes (HNTs) were utilized to prepare polypropylene (PP) nanocomposites by simple melt-compounding approach. Compared with other silicates such as montmorillonite and kaolinite, HNTs show much better dispersion property. The PP nanocomposites with HNTs exhibit concurrence increase in tensile and flexural strength, flexural modulus and impact toughness. Surface modification of HNTs lends the PP nanocomposites higher strength, modulus and lower toughness. The increase in mechanical properties is correlated with the well dispersion of the high aspect ratio HNTs and the orientation of HNTs in PP matrix. Morphology studies show that HNTs can be dispersed in PP uniformly at lower HNTs loading and excessive loading of HNTs causes a little aggregation. Surface modification of HNTs can alleviate the aggregation effectively. The storage modulus of the nanocomposites increases consistently with the HNTs concentration. The surface modification is beneficial to the further improvement in storage modulus. Similar to other silicates, HNTs facilitate the crystallization of PP due to the heterogeneous nucleation

Effect of nanosized and surface-modified precipitated calcium carbonate on properties of CaCO 3/polypropylene nanocomposites

The nanosized and surface-modified precipitated calcium carbonate (PCC) particles have been synthesized by carbonation reaction and used as reinforcing filler for preparing polypropylene (PP) composites. Both a crystallization inhibitor (sodium tripolyphosphate, TPP) and an organic surface modifier (stearic acid) were used to get narrow size distribution, uniform shape and nanometer size. The comprehensive results of morphological and mechanical analyses on PP composites, prepared with trivial, untreated PCC (t-PCC); nanosized and surface-unmodified PCC (n-PCC); nanosized and surface-modified PCC (ns-PCC) separately, were reported and discussed thoroughly.

PPgMA/APTS compound coupling compatabilizer in PP/clay hybrid nanocomposite

AbstractA compound coupling compatibilizer employing coupled use of γ‐(aminopropyl) triethoxy silane (APTS) and maleic anhydride‐graft‐polypropylene (PPgMA) was synthesized for the preparation of polypropylene (PP)/clay hybrid nanocomposites. The designed PPgMA/APTS compound coupling compatabilizer, through condensation of the amino groups of APTS with the anhydride groups of MA moieties in PPgMA, is capable of forming chemical bonding with the organo clay (org‐clay) while maintaining compatibility with the organic PP compartment. Various PPgMA to APTS ratios of these compound coupling compatibilizers were first reacted with clay to form PPgMA/clay masterbatches. The obtained masterbatches were then compounded with PP to produce PP/clay hybrid nanocomposites possessing different characteristics. The composition effects were studied. For org‐clay content of 5 wt %, intercalated‐exfoliated structure of the nanocomposite could be maintained for better reinforcement. Td of 484°C was achieved, indicating significant improvement over neat PP (Td was 386°C) in thermal property. The ultimate tensile strength (30% higher than control) and Young's modulus (57% higher than control) measurements also justified the application of the PPgMA/APTS compound coupling compatibilizer in the incorporation of org‐clay in PP matrix. The use of the PPgMA/APTS compound coupling compatibilizer can provide design flexibility in manufacturing PP/clay hybrid nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008