High-performance Polyolefin Research Articles

Multi-approach synthesis of functionalized graphene oxide as reinforcement for polyethylene: Make a strong interaction

Nanoparticles need to be well dispersed in a polymer matrix to employ their advantages. Their agglomeration may cause defects and stress concentrations, deteriorating the final properties of polymer/graphene nanocomposite. Here graphene oxide (GO) was functionalized in several ways to improve its interaction with polyethylene and dispersion. Polyethylene-grafted maleic anhydride (PE-g-MA) with strong polar groups was used as the matrix to consider a high potential of enhanced interaction with the GO nanoparticles and therefore obtain a high-performance polyolefin composite. First, GO was produced by modified Hammer’s method from graphite. The GO was aminated by phenylene diamine and named FGO. Also GO was reduced chemically to obtain CRGO and thermally to obtain TRGO and then the recent ones were amino functionalized, named FCRGO and FTRGO, respectively. In another route GO was first amino functionalized and then was reduced chemically and named FCRGO+. The synthesized nanoparticles were characterized by visual tests, FTIR, XRD, SEM, and TGA analysis. Subsequently, the study investigates the fabrication of nanocomposites using these nanoparticles at 2 wt% in the PE-g-MA matrix by solution-casting method. The nanocomposites were characterized by optical microscopy, tensile and rheometric tests, FTIR, DSC, and SEM analysis. Based on the results, FCRGO+ was identified as the optimum nanoparticle having better dispersion, improved interfacial interaction, and stronger mechanical properties. The GO functionalized nanocomposites showed up to 36% in tensile modulus, 56% in tensile strength and 70% in elongation at break as compared to those of GO nanocomposites without functionalization of GO.

Recent advancements in multinuclear early transition metal catalysts for olefin polymerization through cooperative effects

Abstract The pursuit of high-performance polyolefin materials has been an objective for chemists. Recently, the development of multinuclear catalysts has significantly enabled the preparation of high-performance polyolefin materials. In this review, we mainly focus on the cooperative effects of multinuclear early transition metal catalysts and provide a comprehensive summary of the research progress in binuclear and multinuclear early transition metal catalysts over the past decade. Compared with the catalytic performance and polymer structure of these catalysts with mononuclear catalysts, we have found that various factors, such as steric hindrance effect, electronic effect, heteroatom effect, hydrogen bonding interaction, the distance between metal centers in multinuclear metal catalysts, and the use of additives, have distinctive and significant impacts on catalyst performance. These effects give rise to notable cooperative effects. This review offers crucial insights and serves as a valuable reference for shaping the future development directions of binuclear and multinuclear early transition metal catalysts.

Covalent Organic Framework-Supported Metallocene for Ethylene Polymerization.

Loading of homogeneous catalysts with support can dramatically improve their performance in olefin polymerization. However, the challenge lies in the development of supported catalysts with well-defined pore structures and good compatibility to achieve high catalytic activity and product performance. Herein, we report the use of an emergent class of porous material -- covalent organic framework material (COF) as a carrier to support metallocene catalyst -- Cp2ZrCl2 for ethylene polymerization. The COF-supported catalyst demonstrates a higher catalytic activity of 31.1 × 106 g/(mol·h) at 140 °C, compared with 11.2 × 106 g/(mol·h) of the homogenous one. The resulting polyethylene (PE) products possess higher weight-average molecular weight (Mw) and narrower molecular weight distribution (Ɖ) after COF supporting, i.e., Mw increases from 160 kDa to 308 kDa and Ɖ reduces from 3.3 to 2.2. The melting point (Tm) is also increased by up to 5.2 °C. Moreover, the PE product possesses a characteristic filamentous microstructure and demonstrates an increased tensile strength from 19.0 MPa to 30.7 MPa and elongation at break from 350% to 1400% after catalyst loading. We believe that the use of COF carriers will facilitate the future development of supported catalysts for high-efficient olefin polymerization and high-performance polyolefins.

Heterogenization Strategies for Nickel Catalyzed Synthesis of Polyolefins and Composites

ConspectusPolyolefin is one of the most common synthetic polymers. However, most polyolefins are nonpolar materials, which leads to poor compatibility with polar materials, thus limiting their application in some fields. Polar functionalized polyolefins can lead to significantly improved dyeability, adhesiveness and compatibility with polar fillers, and can realize customized properties of polyolefin materials. Transition-metal-catalyzed coordination copolymerization of olefin and polar functionalized comonomers represents a direct and potentially economic route to synthesize polar-functionalized polyolefin materials, which has attracted great attention in recent decades. Literally hundreds of nickel and palladium catalysts have been synthesized and investigated in olefin-polar monomer copolymerization to achieve high copolymerization efficiency by tuning the molecular structures of the catalysts. In particular, earth-abundant and low-cost nickel-based catalysts hold great potential for industrial applications. However, most research efforts focus on homogeneous copolymerization catalysts, while the industrially preferred heterogeneous systems have remained largely unexplored. With the objective of bridging this gap, our group has recently developed a series of heterogenization strategies for the synthesis of high-performance heterogeneous nickel catalysts taking advantage of hydrogen bond anchoring, ionic anchoring, coanchoring, cocatalyst, and ionic cluster formation. These strategies involve known or easily accessible catalysts, can be easily adapted to various catalytic systems, and can lead to simultaneous enhancement in all copolymerization parameters such as thermal stability, activity, comonomer incorporation ratio, and copolymer molecular weight versus the homogeneous counterparts. In addition, the performance of the catalysts can be tuned by changing the type of the support, thereby facilitating the discovery of high-performance heterogeneous nickel catalysts. Most importantly, great product morphology control can be achieved. This is desirable for industrial polymerization processes because it avoids reactor fouling and results in significant improvements in the safety and operational efficiency of the polymerization processes. Finally, these heterogenization strategies give access to high-performance polyolefin materials (polar-functionalized polyolefins, polar-functionalized polyolefin in-reactor blends and polyolefin-based functional composites) with custom-made properties. Compared with melt blending, polyolefin composites obtained by heterogeneous catalytic in situ polymerization have better material properties. By using functional fillers, customized polyolefin composites with high performance can be prepared in situ. These polyolefin-based materials have potential applications in many fields, such as electrical and thermal conductivity, photodegradation, flame retardancy, barrier, etc. It is expected that the continuous research on the copolymerization mechanism/catalysts, heterogenizatioin strategies and material properties of polar functionalized polyolefins and their composites will eventually achieve commercialization of nickel-catalyzed production of polyolefins and composites.

Preparation of Polyethylene/α-Zirconium Phosphate Nanocomposites via a Well-Controlled Polyethylene-Grafted Interface.

It is a daunting task to prepare polyolefin nanocomposites that contain well-exfoliated nanoplatelets due to the nonpolar and high crystallinity nature of polyolefins. In this research, a robust approach was developed to prepare polyethylene (PE) nanocomposites by grafting maleated polyethylene (MPE) onto pre-exfoliated α-zirconium phosphate (ZrP) nanoplatelets via a simple amine-anhydride reaction to form ZrP-g-MPE. Several variables, including maleic anhydride (MA) content, MPE graft density, MPE molecular weight, and PE matrix crystallinity, were investigated to determine how they influence ZrP-g-MPE dispersion in PE. It was found that grafted PE has a different morphology and that the long PE brushes with medium graft density on ZrP can achieve sufficient chain entanglement and cocrystallization with PE matrix to stabilize and maintain ZrP-g-MPE dispersion after solution or melt mixing. This leads to enhanced Young's modulus, yield stress, and ductility. The structure-property relationship of PE/ZrP-g-MPE nanocomposites and usefulness of this study for the preparation of high-performance polyolefin nanocomposites are discussed.

Late Transition Metal Catalysts with Chelating Amines for Olefin Polymerization

Polyolefins are the most consumed polymeric materials extensively used in our daily life and are usually generated by coordination polymerization in the polyolefin industry. Olefin polymerization catalysts containing transition metal–organic compound combinations are undoubtedly crucial for the development of the polyolefin industry. The nitrogen donor atom has attracted considerable interest and is widely used in combination with the transition metal for the fine-tuning of the chemical environment around the metal center. In addition to widely reported olefin polymerization catalysts with imine and amide donors (sp2 hybrid N), late transition metal catalysts with chelating amine donors (sp3 hybrid N) for olefin polymerization have never been reviewed. In this review paper, we focus on late transition metal (Ni, Pd, Fe, and Co) catalysts with chelating amines for olefin polymerization. A variety of late transition metal catalysts bearing different neutral amine donors are surveyed for olefin polymerization, including amine–imine, amine–pyridine, α-diamine, and [N, N, N] tridentate ligands with amine donors. The relationship between catalyst structure and catalytic performance is also encompassed. This review aims to promote the design of late transition metal catalysts with unique chelating amine donors for the development of high-performance polyolefin materials.

Necessity and feasibility of new polymerization methodology research for China’s high-performance polyolefin technology development

为加快解决我国聚烯烃产业结构不合理问题和可持续发展问题，聚烯烃高性能化技术的发展须三管齐下，在注重聚合工艺和催化剂技术发展的同时，应加强烯烃聚合反应新方法的研究，探索独立于聚合工艺和催化剂技术发展之外的聚烯烃高性能化技术发展新路径.作为这一理念的实践，同步/原位交联烯烃聚合（S/ICOP）技术基于我国成熟的Ziegler-Natta催化剂和通用聚合工艺分别发展出聚烯烃热塑性弹性体和长链支化聚丙烯的有效制备方法，并均已实现了工业化应用，为新发展路线提供了可行性.未来，通过不断创新功能聚合助剂分子结构，S/ICOP技术还将在基于茂金属催化剂的新一代高端聚烯烃领域发挥作用，创新材料品种、制备方法和制备工艺，推动我国聚烯烃高性能化技术不断向前发展.

Preparation of Polyethylene Nanocomposites Based on Polyethylene Grafted Exfoliated α-Zirconium Phosphate

Polymer nanocomposites containing well-exfoliated nanoplatelets have been shown to possess greatly enhanced physical and mechanical properties. However, it is still a significant challenge to achieve adequate exfoliation of 2D nanoplatelets in polyolefin matrices due to poor compatibility and associated entropic penalty between 2D inorganic filler and nonpolar polyolefin matrices. Grafting polyolefin chains onto the surfaces of an already exfoliated nanoplatelet is a simple, yet effective solution to this problem. The grafted polyolefin chains on the nanoplatelets can entangle and cocrystallize with the polyolefin matrix, preventing agglomeration. In this study, polyethylene (PE) grafted α-zirconium phosphate (ZrP), ZrP-g-PE, was prepared and blended with the PE matrix. The graft density of ZrP-g-PE was designed to maintain ZrP exfoliation during subsequent blending with the PE matrix. It was found that PE confined crystallization formed in ZrP-g-PE, resulting in the formation of PE crystal orientation perpendicular to the ZrP nanoplatelets. The usefulness of this study for preparation of high-performance polyolefin nanocomposites is discussed.

Innovative route for the preparation of high-performance polyolefin materials based on unique dendrimeric silica particles

An innovative methodology for the preparation of high-performance polyolefin-based materials combining a unique dendrimeric silica carrier, a straightforward in situ supporting procedure and in situ ethylene polymerization technique was developed.

Catechol-Functionalized Polyolefins.

The incorporation of comonomers during ethylene polymerization can efficiently modulate important material properties of the polyolefins. Utilizing bioresourced comonomers for the generation of high-performance polyolefin materials is attractive from a sustainability point of view. In this contribution, bioresourced eugenol and related comonomers were incorporated into polyolefins through palladium-catalyzed copolymerization and terpolymerization reactions. Importantly, high-molecular-weight catechol-functionalized polyolefins can be generated. The introduction of different metal ions induces efficient interactions with the incorporated catechol groups, leading to enhanced mechanical properties and self-healing properties. Moreover, the catechol functionality can greatly improve other properties such as surface properties, adhesion properties, and compatibilizing properties. The catechol-functionalized polyolefin was demonstrated as a versatile platform polymer for accessing various materials with dramatically different properties.

Development Strategies for High Performance Synthetic Resins in China

High performance synthetic resin is a key basic material that supports the development of strategic emerging industries such as advanced manufacturing, new energy, and electronic information. In this article, we analyze the demand for high performance synthetic resins by industrial development and review the technical development trends of the industry in China in terms of high performance polyolefin resin and other high performance synthetic resins using the methods of literature research and expert consultation. Moreover, we summarize the problems of the industry including outdated domestic technology and equipment, foreign dependence on several high-end products, insufficiency in basic research, and inadequate efforts in solving the environmental pollution caused by waste plastics. After analyzing the key technologies regarding the high performance synthetic resins, we propose some industrial development suggestions. High-end products should be developed using existing equipment and technology and then put into large-scale application. Basic research and personnel training should be strengthened to guarantee technological innovation. Biodegradable plastics should be developed to promote sustainable development. Technical exchange and cooperation between petrochemical enterprises and universities should be enhanced to improve the efficiency of technology transformation and application.

A displacement-type fluorescent probe reveals active species in the coordinative polymerization of olefins

The correct identification of active species is an important prerequisite to study the mechanism of coordinative polymerization of olefins, which can afford important theoretical guidance for the design and synthesis of new organometallic catalysts and high-performance polyolefin materials.

Design and properties of high-performance polyamide 6/fluoroelastomer blends by electron-induced reactive processing

In recent years, electron-induced reactive processing (EIReP) has emerged as a state-of-the-art technology to modify and develop several kinds of polymeric materials. EIReP uses the spatial and temporal tuneable energy input by high energy electrons during melt mixing process in order to precisely control the desired chemical reactions and processability. Motivated by the successful development of high performance polyolefin based compounds by EIReP, we report herein for the first time the successful preparation of high-performance polyamide 6/fluoroelastomer (50/50, w/w) blends. Relationships between EIReP process parameters (non-reactive mixing time, dose per revolution, electron energy), morphology and properties of blends were established. The blends were prepared using a range of absorbed dose (12.5, 17.5 and 25kGy) while keeping constant values of electron energy (1.5MeV), dose per revolution (17.2kGy/rpm), temperature (230°C) and rotor speed (60rpm). The EIReP-modified blends exhibited excellent mechanical properties and outstanding oil swelling resistance along with good thermal stability. For example, volume swell of the blends was only 5–8% in IRM oil at 150°C for 72h, which was found to be the lowest amongst this type of rubber-plastic blends reported. The improved properties of these blends were explained with the help of interfacial tension between the phase components and electron-induced long-chain branching.

Effect of processing parameters on essential work of fracture toughness of LLDPE blown films

Blown film process is one of the most attractive processes for producing low-cost, high-performance polyolefin films. In this study, mode-I essential work of fracture (EWF) analysis and Elmendorf tear test were performed on m-LLDPE films to investigate how different processing conditions influence blown film EWF and tear properties. After the EWF test, the film was carefully characterized, especially within the necked zone. Effects of frost-line height, draw down ratio, blow-up ratio, and haze-zone region on the EWF parameters of the films were determined. Correlation between the EWF parameters and the films' Elmendorf tear properties was also made. The usefulness of the EWF test for investigating ductile polymeric blown films fracture performance is discussed. POLYM. COMPOS., 55:2403–2413, 2015. © 2015 Society of Plastics Engineers

Supported Single-Site Organometallic Catalysts for the Synthesis of High-Performance Polyolefins

Single-site organometallic catalysts supported on solid inorganic or organic substrates are making an important contribution to heterogeneous catalysis. Early and late transition metal single-site catalysts have changed the polyolefin manufacturing industry and research with their ability to produce polymers with unique properties. Moreover, several of these catalysts have been commercialized on a large scale. Their heterogenization for slurry or gas phase olefin polymerization is important to produce polyolefin as beads and to avoid reactor fouling. The large majority of supports currently used in industry are inorganic materials (SiO2, Al2O3, MgCl2), with silica being the most important. Single-site supported catalysts are most commonly prepared by molecular-level anchoring/chemisorption, in which a molecular precursor undergoes reaction with the surface while maintaining most of the ligand sphere of the parent molecule. Chemisorption of discrete organometallic complexes on solid supports yields catalysts with well-defined active sites, greater thermal stability than the homogeneous analogues, and decreased reactor fouling versus the homogeneous analogues. This review presents a detailed account of the synthesis, characterization and polymerization properties of single-site catalysts supported on metal oxides and metal sulfated oxides, primarily carried out at Northwestern University. Early and late transition metal single-site catalysts supported on inorganic surfaces have changed the polyolefin research and production with their unique ability to produce polymeric materials with unique architectures. This review presents a detailed account of the synthesis, characterization, and polymerization properties of single-site catalysts supported on metal oxide surfaces.

2D-QSPR/DFT studies of aryl-substituted PNP-Cr-based catalyst systems for highly selective ethylene oligomerization

1-Hexene and 1-octene are important comonomers for the synthesis of high performance polyolefins. Recently, various N-substituted Cr-bis(diphenylphosphino)amine (PNP-Cr) catalysts show the potential as excellent candidates for highly selective ethylene trimerization/tetramerization. In this work, a series of aryl-substituted PNP-Cr catalysts were studied by two-dimensional quantitative structure-property relationship (QSPR) method based on density functional theory (DFT) calculations. The heuristic method (HM) and best multi-linear regression (BMLR) were used to establish the best linear regression models to describe the relationship between selectivities and catalyst structures. Both Cr(I) and Cr(II) active site models for ethylene trimerization/tetramerization were considered. It was found that 1) the relativity and stability of the models were increased by using self-defined descriptors based on DFT calculations; 2) Cr(I)/Cr(III) centers were the most plausible active sites for ethylene trimerization, while Cr(II)/Cr(IV) active sites were most possibly responsible for ethylene tetramerization; and 3) the skeleton structures of the PNP-Cr system with good complanation and symmetry were crucial for achieving excellent catalytic selectivity of 1-octene, while the PNP-Cr backbone with a large steric effect on N atom would benefit ethylene trimerization. Six new PNP ligands with high selectivity toward ethylene trimerization/tetramerization were predicted based on descriptor analysis and the best linear regression models providing a good basis for further development of novel catalyst systems with better performance.

Preparation of nano-compounded polyolefin materials through in situ polymerization technique: status quo and future prospects

Nano-compounding of polyolefins, an economical yet very effective route to high-performance polyolefin materials, has received considerable attention in recent years. Unlike most of the other polymers, polyolefins are chemically inert, which dictates that nano-compounding of polyolefins has to be conducted via in situ polymerization. In this review, a technological progress of the nano-compounding of polyolefins via in situ polymerization technique was summarized thoroughly, with emphasis laid on the current research status of polyolefin/montmorillonite (MMT) nanocomposites. A clear perspective for future researches on this specific family of materials was envisaged.

Novel Olefin Block Copolymers through Chain‐Shuttling Polymerization

Shuttle chain in operation: “Chain-shuttling” polymerization is a promising strategy for the synthesis of high-performance polyolefins. Polymerization takes place block by block using two different catalysts to generate new block copolymers with special properties.

Recent progress in polyolefin materials and processing

In 1998, about 50% of plastic materials production in the world was made up by polyethylene (PE), polypropylene (PP) and other such polyolefin groups. Recently, various types of high-performance polyolefin materials including alloy and blend with other materials have been developed and accepted broadly in the market. For further widespread use, enhanced performance, further cost reduction, and considerations for environmental protection are needed. To find appropriate approaches to these requirements, polyolefin should be investigated in terms of not only materials but also processing.

Development of High Performance Polyolefin Nonwovens and Polymers

Development of High Performance Polyolefin Nonwovens and Polymers