Propylene Copolymer Research Articles

Theoretical–Experimental Study of the Action of Trace Amounts of Formaldehyde, Propionaldehyde, and Butyraldehyde as Inhibitors of the Ziegler–Natta Catalyst and the Synthesis of an Ethylene–Propylene Copolymer

The copolymer synthesis process can be affected by failures in the production process or by contaminating compounds such as ketones, thiols, and gases, among others. These impurities act as an inhibiting agent of the Ziegler-Natta (ZN) catalyst affecting its productivity and disturbing the polymerization reaction. In this work, the effect of formaldehyde, propionaldehyde, and butyraldehyde on the ZN catalyst and the way in which it affects the final properties of the ethylene-propylene copolymer is presented by analyzing 30 samples with different concentrations of the mentioned aldehydes along with three control samples. It was determined that the presence of formaldehyde 26 ppm, propionaldehyde 65.2 ppm, and butyraldehyde 181.2 ppm considerably affect the productivity levels of the ZN catalyst; this effect increases as the concentration of aldehydes is higher in the process; likewise, these impurities affect the properties of the final product, such as the fluidity index (MFI), thermogravimetric analysis (TGA), bending, tension, and impact, which leads to a polymer with low-quality standards and less resistance to breakage. The computational analysis showed that the complexes formed by formaldehyde, propionaldehyde, and butyraldehyde with the active center of the catalyst are more stable than those obtained by the ethylene-Ti and propylene-Ti complexes, presenting values of -40.5, -47.22, -47.5, -5.2 and -1.3 kcal mol-1 respectively.

Study on the Low-Temperature Rheology of Polar Drilling Fluid and Its Regulation Method

Drilling fluid is the blood of drilling engineering. In the polar drilling process, the ultra-low temperature environment puts high demands on the rheological performance of drilling fluids. In this paper, the effects of temperature, ice debris concentration and weighting agent on the rheological properties of drilling fluids were studied. It was found that the lower the temperature and the higher the ice debris concentration, the higher the drilling fluid viscosity, but when the ice debris concentration was below 2%, the drilling fluid rheology hardly changed. Secondly, the low temperature rheological properties of drilling fluid were adjusted by three different methods: base fluid ratio, organoclay, and polymers (dimer acid, polymethacrylate, ethylene propylene copolymer, and vinyl resin). The results showed that the base fluid rheological performance was optimal when the base fluid ratio was 7:3. Compared with polymers, organoclay has the most significant improvement on the low temperature rheological performance of drilling fluid. The main reason is that organoclay can transform the drilling fluid from Newtonian to non-Newtonian fluid, which exhibits excellent shear dilution of drilling fluid. The organoclay is also more uniformly dispersed in the oil, forming a denser weak gel mesh structure, so it is more effective in improving the cuttings carrying and suspension properties of drilling fluids. However, the drilling fluid containing polymer additives is still a Newtonian fluid, which cannot form a strong mesh structure at ultra-low temperatures, and thus cannot effectively improve the low-temperature rheological performance of drilling fluid. In addition, when the amount of organoclay is 2%, the improvement rate of the yield point reaches 250% at -55 °C, which can effectively improve the cuttings carrying and suspension performance of drilling fluid at ultra-low temperature.

Stabilization Activity of Kelp Extract in Ethylene–Propylene Rubber as Safe Packaging Material

This paper presents the stabilization effects of the solid extract of kelp (Ascophyllum nodosum) on an engineering elastomer, ethylene-propylene copolymer (EPR), which may be used as packaging material. Progressive increase in additive loadings (0.5, 1, and 2 phr) increases the oxidation induction time for thermally aged rubber at 190 °C from 10 min to 30 min for pristine material and modified polymer by adding 2 phr protection powder. When the studied polymer is γ-irradiated at 50 and 100 kGy, the onset oxidation temperatures increase as a result of blocking the oxidation reactivity of free radicals. The stabilization effect occurs through the activity of alginic acid, which is one of the main active components associated with alginates. The accelerated degradation caused by γ-exposure advances more slowly when the kelp extract is present. The OOT value for the oxidation of EPR samples increases from 130 °C to 165 °C after the γ-irradiation of pristine and modified (2 phr of kelp powder) EPR, respectively. The altered oxidation state of EPR samples by the action of γ-rays in saline serum is faster in neat polymer than in stabilized material. When the probes are placed in physiological serum and irradiated at 25 kGy, the OOT value for neat EPR (145 °C) is much lower than the homologous value for the polymer samples protected by kelp extract (153 °C for the concentration of 0.5 phr, 166 °C for the concentration of 1 phr, and 185 °C for the concentration of 2 phr).

Direct Synthesis of Ultrahigh Molecular Weight Functionalized Isotactic Polypropylene

Open AccessCCS ChemistryRESEARCH ARTICLES10 Jan 2023DirectSynthesis of Ultrahigh Molecular Weight Functionalized Isotactic Polypropylene Guanglin Zhou, Hongliang Mu, Xin Ma, Xiaohui Kang and Zhongbao Jian Guanglin Zhou Google Scholar More articles by this author , Hongliang Mu Google Scholar More articles by this author , Xin Ma Google Scholar More articles by this author , Xiaohui Kang Google Scholar More articles by this author and Zhongbao Jian Google Scholar More articles by this author https://doi.org/10.31635/ccschem.023.202202621 SectionsSupplemental MaterialAboutPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Ultrahigh molecular weight functionalized isotactic polypropylene (f-UHMW-iPP) through the direct copolymerization of propylene with polar monomers is highly desired but has not been accessed thus far, as it involves challenging regio- and stereo-chemistry along with usually reduced molecular weight. Herein, in contrast to the unsuccessful catalyst strategy, a polar monomer assisted strategy is used to access the above material. The introduction of O- or S-functionalized long-chain polar olefins into the hafnium-catalyzed copolymerization of propylene (and also bulkier α-olefins) significantly increases the copolymer molecular weight with a maximum observed increase of +488%. f-UHMW-iPP and isotactic poly(α-olefin)s (Mw> 2,000 kDa, [mmmm]: 99%) are thus prepared at ambient conditions. The incorporation of 1 mol% of polar monomer improves the surface property and significantly increases the long-sought toughness (860%) of brittle iPP, without reducing the tensile strength (42 MPa) due to the key achievement on ultrahigh molecular weight. A discussion of the mechanism involved in the beneficial effects of incorporating the polar monomer is presented by an in-depth density functional theory (DFT) calculation. Download figure Download PowerPoint Previous articleNext article FiguresReferencesRelatedDetails Issue AssignmentNot Yet AssignedSupporting Information Copyright & Permissions© 2023 Chinese Chemical Society Downloaded 0 times PDF downloadLoading ...

Critical conditions for liquid chromatography of statistical polyolefins: Evaluation of diene distribution in EPDM terpolymers

Liquid chromatography at critical conditions is of interest as it may unravel molecular information on macromolecular structures not accessible by any other analytical techniques. Yet so far, such conditions have never been experimentally established for copolymers, where a particular need for such information exists. Toward this goal, critical conditions for statistical ethylene propylene copolymers were identified. In the first approach the composition of the binary mobile phase was varied at a constant temperature, and secondly by modulating the adsorption-desorption temperature at constant mobile phase composition. Solvents for both methods were identified by using a novel approach that combines structure retention relationships with Hansen Solubility Parameters. As a result, for the first time, the heterogeneity of an ethylene propylene diene terpolymer sample with regard to the pendant double bond of the diene could be determined. The novel chromatographic approach was validated by measuring the composition of fractions taken over the chromatographic run offline by nuclear magnetic resonance. In summary, this work gave the first experimental evidence for the existence of critical conditions for polyolefin random copolymers, as postulated by Brun. This novel chromatographic approach holds immense potential to engineer complex polymers towards future applications by making use of the now-accessible molecular information.

Surfactant Control of Coffee Ring Formation in Carbon Nanotube Suspensions.

The coffee ring effect regularly occurs during the evaporation of colloidal droplets and is often undesirable. Here we show that adding a specific concentration of a surfactant can mitigate this effect. We have conducted experiments on aqueous suspensions of carbon nanotubes that were prepared with cationic surfactant dodecyltrimethylammonium bromide added at 0.2, 0.5, 1, 2, 5, and 10 times the critical micelle concentration. Colloidal droplets were deposited on candidate substrates for printed electronics with varying wetting characteristics: glass, polyethylene terephthalate, fluoroethylene propylene copolymer, and polydimethylsiloxane. Following drying, four pattern types were observed in the final deposits: dot-like, uniform, coffee ring deposits, and combined patterns (coffee ring with a dot-like central deposit). Evaporation occurred predominantly in constant contact radius mode for most pattern types, except for some cases that led to uniform deposits in which early stage receding of the contact line occurred. Image analysis and profilometry yielded deposit thicknesses, allowing us to identify a coffee ring subfeature in all uniform deposits and to infer the percentage coverage in all cases. Importantly, a critical surfactant concentration was identified for the generation of highly uniform deposits across all substrates. This concentration resulted in visually uniform deposits consisting of a coffee ring subfeature with a densely packed center, generated from two distinct evaporative phases.

Propylene/Cyclic Olefin Copolymers with Cyclopentene, Cyclohexene, Cyclooctene, Tricyclo[6.2.1.0(2,7)]undeca-4-ene, and Tetracyclododecene: The Synthesis and Effect of Cyclic Structure on Thermal Properties

Propylene (P) copolymers with a series of cyclic olefins [cyclopentene (CPE), cyclohexene (CHE), cis-cyclooctene (COE), tricyclo[6.2.1.0(2,7)]undeca-4-ene (TCUE), and tetracyclododecene (TCD)] have been prepared in toluene in the presence of phenoxide-modified half-titanocene catalysts, especially Cp’TiCl2(O-2,6-iPr2C6H3) (Cp’ = 1,2,4-Me3C5H2, tBuC5H4), and methylaluminoxane (MAO) cocatalyst. The resultant copolymers are amorphous materials, and their compositions were uniform as confirmed by DSC thermograms [sole glass transition temperatures (Tg)]. The cyclic olefins were incorporated in a 1,2-insertion manner, and the incorporation was affected by the kind of cyclic olefin as well as the nature of catalysts employed. The CHE contents in the copolymers were up to 6.3 mol % (incorporated in an isolated manner), whereas the CPE, COE, TCUE, and TCD contents in the copolymers increased up to ca. 40 mol % (with a mixture of isolated and alternating incorporations) with an increase in the comonomer concentration charged. Linear correlations between Tg values and cyclic olefin contents were demonstrated in all copolymers. The cyclic structure affects the Tg values in the propylene copolymers, except that plots of Tg values vs cyclic olefin contents were close in the P/CPE and P/COE copolymers. In the low cyclic olefin content region (up to 25 mol %), the Tg values in the propylene copolymers were higher than those in the ethylene copolymers.

Fade resistance of propylene-ethylene copolymer. Effect of low concentration of organophilic montmorillonite

Propylene-ethylene copolymer (PEC) is an important material used in the production of a large diversity of plastic goods. However, its low polarity and lack of functional groups make PEC challenging for dye coloring. A method to obtain colored PEC using the cationic dye Rhodamine 6G (RA) was investigated. It involves modification with very low concentrations of organophilic montmorillonite (o-Mt) and a propylene copolymer grafted with maleic anhydride by producing nanocomposites having very thin clay tactoids. Mixing was performed in molten state in a batch mixer considering 0.1 wt% of dye and up to 3 wt% of clay. FT-IR, XRD, SEM and rheology were used to analyze the effect of clay and dye on composite morphology while fade resistance to solvent and UV-radiation was analyzed by UV–visible spectroscopy and colorimetry. Neither structure nor properties of polymeric systems are affected by addition of RA. In fact, the degree of oxidation reached by the polymeric material after UV irradiation as well as its fade resistance is determined by clay concentration. The addition of just 1 wt% of o-Mt reduces in about one eighth the exposure time at which the polymer reaches a given value of total color difference, ∆E*.

Effects of chronic exposure of naturally weathered microplastics on oxidative stress level, behaviour, and mitochondrial function of adult zebrafish (Danio rerio)

Microplastics (MPs) are a big and growing environmental concern, with studies showing sublethal to acute biological impacts on typical aquatic organisms. However, little is known about the biological effects of naturally weathered MPs, particularly focusing on mitochondria dysfunction as the key trigger of the biological effects. Therefore, in this study, naturally weathered MPs were produced from day-to-day life products, characterized, and chronically exposed (21 days) to adult zebrafish at the concentration of 0.1 and 1 mg/L. Locomotion and unconditioned anxiety-like behaviour was assessed. Mitochondrial respiration, membrane potential, mitochondrial complex activity and oxidative-related parameters were evaluated in the brain and liver. The results revealed the weathered MPs as a copolymer of propylene and ethylene that induced anxiety-like behaviour. There was an increase in brain catalase activity while the brain lactate dehydrogenase activity was inhibited after exposure to 1 mg/L. Brain glutathione levels were increased while their ratio was not affected. Mitochondrial respiratory chain complex Ⅱ and IV were also significantly decreased in the brain, although not compromising mitochondrial function. On the other hand, exposure to 1 mg/L caused a deficiency in liver mitochondrial respiration and decreased mitochondrial membrane potential, which were associated with the mitochondrial respiratory chain inhibition. An increase in hepatic superoxide dismutase and catalase activity was noticed, supporting the occurrence of ROS-induced ROS release as the potential trigger for the mitochondrial dysfunction. Overall, these findings highlight the potential indirect and cumulative environmental effects these particles may pose to aquatic ecosystems.

Digital Strategies to Improve Product Quality and Production Efficiency of Fluorinated Polymers: 1. Development of Kinetic Model and Experimental Verification for Fluorinated Ethylene Propylene Copolymerization

Digitalization of industrial polymerization processes represents an effective and efficient approach for product-grade upgrading and for production efficiency improvement. A mechanistic model based on the first principles of elementary reactions and mass balances provides a powerful tool in the practice of process digitalization. In this work, we developed a comprehensive kinetic model for the batch process of bulk copolymerization of tetrafluoroethylene with hexafluoropropylene. A series of experimental runs were carried out under various conditions. The fluorinated ethylene propylene copolymer samples were collected, with the monomer conversions, copolymer compositions, and polymer molecular weights, as well as the melting and crystallization properties, fully analyzed. The model was then correlated with the data for estimation of the model parameters. The reactivity ratios were found to be r1 = 65.5 and r2 = 2.6 × 10–3. With a whole set of estimated parameters, the model was used to simulate results under different polymerization conditions close to industrial production processes, which were further verified with additional experimental data. The agreement between simulated and experimental results was good. The experimentally verified model provides a powerful tool for industrial process optimization aiming at improvement of product quality and production efficiency.

Stereoselective Copolymerization of Olefin with Polar Monomers to Access Stereoregular Functionalized Polyolefins

Introducing polar functionalities to polyolefins such as polyethylene and polypropylene is highly desirable for improving physical properties of the otherwise non-polar material. The synthesis of stereoregular functionalized polyolefins, however, has been a relatively underdeveloped area compared to that of functionalized polyethylene because of the lack of suitable catalysts that tolerate polar groups while possessing stereoselectivity. This review summarizes recent advances concerning the access to stereoregular functionalized polyolefins, including synthetic strategies such as post-functionalization, chain transfer and direct copolymerization methods. The focus of the review lies in the copolymerization approach, in which various polar comonomers and versatile stereoselective polymerization catalysts based on both early and late transition metals are involved. Polymer properties and potential applications for these materials are simply discussed.1. Introduction2. Reactive-Intermediate-Polymer Approach to Stereoregular Functionalized Polypropylene3. Preparation of Stereoregular Functionalized Polypropylene by Chain-End Functionalization4. Stereoselective Copolymerization of Propylene and Polar Monomers by Early Transition Metal Catalysts5. Stereoselective Copolymerization of Propylene with Polar Monomers by Late Transition Metal Catalysts6. Stereoselective Copolymerization of α-Olefins with Polar Monomers7. Stereoselective Homopolymerization of Polar Monomers8. Polymer Properties and Potential Applications9. Conclusion and Outlook

Copolymerization of propylene with higher α‐olefin using supported titanium catalyst system

AbstractCopolymers of propylene/1‐octene and propylene/1‐hexene were synthesized in slurry phase polymerization using MgCl2/TiCl4/Diester based catalyst system. The Al/Do (co‐catalyst/external donor), Al/Ti (co‐catalyst/catalyst) mole ratio variations were investigated for effect on polymerization and copolymer properties. Incorporation of comonomer (1‐hexene and 1‐octene) has influenced the molecular weight distribution (MWD) of resultant copolymers as well as isotacticity. The differential Scanning Calorimetry (DSC) results showed lower melting point for propylene/1‐hexene than propylene/1‐octene copolymer. The gel permeation chromatography (GPC) study indicated broad MWD of both type of copolymers compared to homo PP. The 13C NMR has also been performed to quantitatively evaluate incorporation of comonomer in polymer backbone. Propylene copolymerizaiton with hexene resulted in the copolymer which have relatively higher amount of 1‐hexene compared to 1‐octene incorporation in copolymer of propylene/1‐octene with similar catalyst system explain the reason for lower peak melting points.

Density Functional Theory Study of the Regioselectivity in Copolymerization of bis-Styrenic Molecules with Propylene Using Zirconocene Catalyst

Density functional theory (DFT) was used to study the regioselectivity of the copolymerization of propylene and the bis-styrenic molecules (DVB and BVPE) using a zirconocene catalyst. This study reveals the following: when hydrogen is introduced to reactivate the catalyst on the vinyl bonds containing DVB or BVPE, the second vinyl bond is inserted into the polymer in a regio-irregular 1,2-way. (I) The 1,2-insertion mode forms more thermodynamically stable products. (II) The 2,1 insertion, DVB-PP1, or BVPE-PP1 needs to rotate 180° along the Zr-C1 bond to complete the process; thus, it is easier to accomplish the 1,2 insertion. (III) The analysis of the local electrophilicity/nucleophilicity index and the Fukui functions also indicate that the 1,2-insertion mode is the optimal insertion mode. Investigating the mechanism of this experimental phenomenon is important in the development of a functionalization strategy for polypropylene (PP) polymers.

Crosslinked anion exchange membranes prepared from highly reactive polyethylene and polypropylene intermediates

To obtained polyolefin-based anion exchange membranes (AEMs) with high performance in high efficiency, reactive polyolefin intermediates were prepared via polymerization of ethylene or propylene with 1-iodo-10-undecene (IUD) by single-site rac-ethylenebis(indenyl)Zr(IV) dichloride and dimethyl (pyridylamido)Hf(IV) catalysts, respectively. The catalytic activity for synthesis of these reactive polyolefin intermediates was up to 2.94 × 106 for ethylene copolymers (PEI-x) and 7.20 × 106 gpolymer molcat.−1 h−1 for propylene copolymers (PPI-x), respectively. Moreover, incorporation ratio of IUD in copolymers was high up to 19.8 (PEI-x) and 29.7 mol% (PPI-x), respectively. These copolymers could be well dissolved in o-xylene, make them easily crosslinked and quaternized to give polyolefin-based AEMs. These AEMs with crosslinking structure exhibited high hydroxide conductivity (131 and 143 mS/cm for PEI-20-C100-QA and PPI-30-C70-QA at 80 °C, respectively) and excellent alkaline stability without visible loss in hydroxide conductivity after 1680 h. These AEMs exhibited evident microphase separation via microphase study, presented low swelling ratio even with high water uptake. A H2/O2 fuel cell with PEI-20-C100-QA presented a peak power density of 439 mW cm−2 without optimized membrane electrode assembly fabrication process.

Novel titanium (IV) diolate complexes with thiophene-containing OSO-type ligand as pre-catalyst for ethylene polymerization and ethylene - propylene copolymerization

New titanium (IV) complexes with diolate ligand containing additional donor sulfur atom have been synthesized and characterized. Structure of complex 2 was established by X-ray diffraction. Titanium atom adopts a distorted tetrahedral geometry formed by oxygen atoms of two ligands and isopropoxy-groups. Activation of these complexes with {EtnAlCl3-n + Bu2Mg} led to a highly active catalytic system for ethylene polymerization with an activity up to 2 tons PE·molTi-1·atm-1·h-1. Linear ultrahigh molecular weight polyethylenes (1.9-5.7 106 Da) were obtained under these conditions. The obtained polyethylenes are suitable for the modern methods of polymer processing - the solventless solid state formation of super high-strength (breaking strength up to 2.6 GPa) and high-modulus (elastic modulus up to 164 GPa) oriented films and film tapes. The precatalysts 1-3 were also active in ethylene-propylene copolymerization producing copolymers with a content of propylene units in the range 28-33%. The influence of the nature of the «leaving» monodentate σ-ligands (Cl, OiPr and N(CH3)2) and the organoaluminum co-catalyst (Et2AlCl and Et3Al2Cl3) on the activity of catalytic systems and the properties of the resulting polymers were studied.

Potential of Functionalized Polyolefins in a Sustainable Polymer Economy: Synthetic Strategies and Applications.

Polymers play a crucial role in our modern life as no other material exists that is so versatile, moldable, and lightweight. Consequently, the demand for polymers will continue to grow with the human population, modernization, and technological developments. However, depleted fossil resources, increasing plastic waste production, ocean pollution, and related growing emission of greenhouse gases has led to a change in the way we think about the use of polymers. Although polymers were never designed to be recycled, it is clear that a linear polymers economy is no longer sustainable. The design for recycling and reuse and life-cycle analyses will become increasingly important factors when deciding on which polymer to choose for a certain application. Of all polymers, polyolefins have the lowest life-cycle environmental impact and even outperform renewable polymers. However, polyolefins are chemically inert and reveal a low surface energy. Combining their excellent mechanical properties with the ability to adhere to other materials or create self-assembled or nanostructured materials would widen the application window of polyolefins even more.This Account covers part of our personal account in the field of functionalized polyolefin synthesis and their application development. We start with addressing the challenge of finding suitable catalysts that tolerate nucleophilic functionalities, which tends to poison most electrophilic catalysts even when passivated with, for example, an aluminum alkyl. We argued that lowering of the oxidation state of a titanium-based catalyst might lower the electrophilicity of the metal center. Indeed, this simple approach resulted in an unprecedentedly high tolerance toward aluminum alkyl-passivated alkenols during their copolymerization with ethylene. Interestingly, catalyst deactivation was much less pronounced during the copolymerization of propylene and aluminum-passivated alkenols, clearly demonstrating the protective effect of the methyl branch in the growing polymer. Because the use of randomly functionalized polypropylenes is rather underdeveloped, as compared to the corresponding randomly functionalized polyethylenes, we focused on potential applications of the former material. Atactic or low-crystalline hydroxyl- and carboxylic acid-functionalized propylene-based co- and terpolymers form elastomers with interesting properties that can be influenced by enhancing the hydrogen bonding within the system or by creating ionomers. The polar functionalities cluster together in domains that can host small polar molecules such as, for example, a pH indicator, thus affording useful sensors. The functionalized polyolefins can also be used as precursors for amphiphilic graft copolymers, undergoing self-assembly and therefore being suitable for nanoporous membrane preparation. The graft copolymers also proved to be effective compatibilizers in various polymer blends.

Chemically Recyclable Ester-Linked Polypropylene.

Polyolefins represent the largest class of commodity materials due to their excellent material properties; however, they have limited pathways to chemical recycling and are often difficult to mechanically recycle. Here we demonstrate a new catalyst for the isoselective copolymerization of propylene and butadiene capable of favoring 1,4-insertion over 1,2-insertion while maintaining good molecular weights and turnover frequencies. This isotactic propylene copolymer with main-chain unsaturation was depolymerized to a telechelic macromonomer using an olefin metathesis catalyst and 2-hydroxyethyl acrylate. After hydrogenation, the telechelic macromonomer was repolymerized to form an ester-linked polypropylene material. This polymer shows thermal and mechanical properties comparable to linear low-density polyethylene. Finally, the telechelic macromonomer could be regenerated through the depolymerization of the ester-linked polypropylene material, which allows for the chemical recycling to macromonomer. This process provides a route to transform partially unsaturated polyolefins to chemically recyclable materials with similar properties to their parent polymers.

Multistep Bulk‐/Gas‐Phase Polymerization of Propene in a Reaction Calorimeter

AbstractThis article outlines a kinetic study of two different Ziegler–Natta type catalysts in multistep bulk‐/gas‐phase polymerization of propene in a reaction calorimeter. In the first stage, bulk‐phase polymerization of propene, the matrix material is produced and kinetic information about the polymerization is extracted from power compensation calorimetry data. Focus is set on the influence of hydrogen on polymerization kinetics and comparing the performance of the two catalysts. In the 2nd stage, gas‐phase copolymerization of propene and ethylene, an elastomeric copolymer is produced as impact modifier and kinetic information is obtained from semibatch operation in constant conditions. The influence of monomer/comonomer ratio on copolymerization behavior of the two catalysts is investigated and compared.

Impact polypropylene copolymers containing multifold H-shape long-chain-branching structures: Synthesis and properties

ω -Alkenylmethyldichlorosilane as a proven in-situ long-chain-branching agent particularly effective with olefin polymerization by Ziegler-Natta catalysts was seamlessly fit into fully implemented impact copolymerization of propylene exercised by polymerization, steam-treatment of afforded polymer granules, and twin-screw extrusion in a row to deliver, for the first time, long-chain-branched impact polypropylene copolymers (LCB-IPCs). Multifold H-type LCB structures were revealed with the LCB-IPCs, including two homologous structures based on polypropylene (PP- H -PP) and ethylene-propylene copolymer (EPC- H -EPC) individually, and a heterologous structure mixed of PP and ethylene-propylene copolymer (PP– H -EPC). Though all in minute amount, the LCB structures induced significant improvement in IPCs on many fronts. On melt properties, LCB-IPCs gained the unprecedented strain hardening property in extensional flow. On phase morphology, the LCB structures helped reduce the dispersion dimension of ethylene-propylene copolymer and the tendency of grain coarsening in post-preparation processing. On melt crystallization, the LCB structures enhanced the crystallization in an all-round way by prompting self-nucleation. On mechanical properties, by reinforcing the PP matrix and strengthening the interface to facilitate stress transfer between PP and EP copolymer, the LCB structures enabled an all-out promotion of mechanical properties with simultaneous reinforcement on stiffness and toughness. Fully implemented impact copolymerization of propylene preparing impact polypropylene copolymers was engaged with LCB agent 5-hexenylmethyldichlorosilane, which prompted formation of multifold H-shape LCB structures in the copolymers. The multifold LCB structures in turn induced profound improvement on multiple fronts of the copolymer properties. • ω -Alkenylmethyldichlorosilane is used as a LCB agent in impact copolymerization of propylene. • The new IPC polymers contain multifold H-type LCB structures. • The LCB structures induced significant improvement in properties of IPC on many fronts.

Wear resistance effects of alumina and carbon nanoscale fillers in PFA, FEP, and HDPE polymers

Following numerous studies demonstrating the ability of nanostructured alpha-alumina filler to reduce the prohibitively high wear rate of polytetrafluoroethylene (PTFE) down to extremely small values (∼10−7 mm3/Nm) well below those of conventional PTFE micro-composites, alpha-alumina filler was also shown capable, in a couple recent studies, of imparting similar performance to another fluoropolymer, perfluoroalkoxy (PFA) copolymer, which otherwise was similarly lacking wear resistance in the unfilled state. In addition to duplicating such alpha-alumina performance in PFA, in this study such an extreme wear-reducing capability has also been demonstrated using nanocarbon powder, as an example representative of several other forms of nanoscale carbon filler that like alpha-alumina had been shown capable of providing extreme resistance to PTFE. Fluorinated ethylene propylene (FEP) copolymer, whose nanocomposites have not been tribologically explored previously, was thus more fully investigated here with not only alpha-alumina and nanocarbon, but also other nanotube (CNT) and mesoporous forms of nanoscale carbon fillers. In preliminary testing, only the alpha-alumina filler indicated an ability to impart its wear-reducing capability to FEP; a wear rate of ∼0.8 × 10−6 mm3/Nm was observed at 2 wt% alpha-alumina concentration. While this is an impressive reduction in wear rate, it is not quite as extreme a reduction as that observed in PTFE or PFA. The transport of the extreme wear resistance of nanocarbon powder in PTFE and PFA was even more partial and incomplete in FEP, with the ∼0.3 × 10−3 mm3/Nm unfilled FEP wear rate only reduced to ∼10−5 mm3/Nm, while the CNT and mesoporous carbon fillers were even less effective. Correspondingly, ATR-FTIR spectra from FEP wear surfaces displayed sizable peaks evident of the chelation of chemical interactions known to be associated with wear resistance for PTFE and PFA matrices only in the most wear-resistant alpha-alumina case and to a lesser extent for the nanocarbon. Finally, it is demonstrated that such fillers demonstrate such strongly beneficial effects only in polymers that otherwise lack wear resistance, and may actually be deleterious for polymers such as high density polyethylene (HDPE) already having some inherent wear resistance in their unfilled state.