JOURNAL OF CATALYSIS
·
2018
·
IF 6.759
Wei Li,Lei Hui,Bing Xue,Chuanding Dong,Yuming Chen,Linxi Hou,Binbo Jiang,Jingdai Wang,Yongrong Yang
A Polyhedral oligomeric silsesquioxane (POSS) modified Ziegler-Natta catalyst is reported to synthesize the weakly entangled ultra-high molecular weight polyethylene at a high temperature and with a high activity. Incorporation of POSS can form numbers of aggregates with a mean size of 48 nm adsorbing on the surface of SiO 2 . The structure of nanoaggregates is evidenced by the experiments and theoretical calculations where one POSS can coordinate with multiple MgCl 2 molecules serving as an electric donor to the further immobilized TiCl 4 . The catalyst is thus featured by two distinct active regions positioned in the POSS/MgCl 2 nanoaggregates and δ -MgCl 2 , respectively. The former regions present extremely low activity on ethylene polymerization, which function as horizontal separators for isolating the active TiCl 4 sites and the growing chains. This catalyst exhibits an exceptional activity ( i.e. 1.3 × 10 6 gPE mol Ti −1 h −1 bar −1 ) for the synthesis of weakly entangled polyethylene at 60 °C.
研究领域:
材料科学
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催化化学
✓ 已验证
产品关联
DOI
高影响因子
ACS Omega
·
2021
·
IF 3.512
Tianyu Lan,Na Zhang,Liduo Chen,Cuiqin Li,Jun Wang
The 1.0G dendrimer polyamidoamine (PAMAM), 3,5-dichlorosalicylaldehyde, and TiCl4·2THF were used as synthetic materials, and the dendritic salicylaldehyde imide ligand with substituent hindrance and its titanium catalyst were synthesized by the condensation reaction of Schiff base. The structure of the synthesized products was characterized by infrared spectroscopy, nuclear magnetic resonance hydrogen spectroscopy, ultraviolet spectroscopy, electrospray mass spectrometry, and inductively coupled plasma-mass spectrometry. Activated methylaluminoxane (MAO) was used as a catalyst precursor for ethylene polymerization in the process of ethylene catalytic. The effects of ethylene polymerization were studied in terms of the Al/Ti molar ratio, reaction time, reaction temperature, polymerization pressure, and ligand structure of the catalyst. The results show good catalytic performance (70.48 kg PE/mol Ti·h) for ethylene polymerization because of the existence of ortho substituent hindrance on the salicylaldehyde skeleton. Furthermore, high-temperature gel permeation chromatography (GPC)-IR, differential scanning calorimetry (DSC), and torque rheometer were used to characterize the microstructure, thermal properties, and viscoelastic state of the polyethylene samples obtained. The results showed that the product was ultrahigh-molecular-weight polyethylene.
研究领域:
化学
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材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Polymers
·
2023
·Vol. 15
·期 11
·2501
·
IF 5
Panpan Zhang,Qiongqiong Xu,Wenyu Mao,Jiaxing Lv,Haodong Tang,Huadong Tang
A novel synthesis of ultrahigh molecular weight poly(methyl methacrylate) (PMMA) using organosulfur compounds combined with a catalytical amount of transition metal carboxylates as an initiator has been developed. The combination of 1-octanethiol with palladium trifluoroacetate (Pd(CF3COO)2) was found to be a very efficient initiator for the polymerization of methyl methacrylate (MMA). An ultrahigh molecular weight PMMA with a number-average molecular weight of 1.68 × 106Da and a weight-average molecular weight of 5.38 × 106Da has been synthesized at the optimal formulation of [MMA]:[Pd(CF3COO)2]:[1-octanethiol] = 94,300:8:23 at 70 °C. A kinetic study showed that the reaction orders with respect to Pd(CF3COO)2, 1-octanethiol, and MMA are 0.64, 1.26, and 1.46, respectively. A variety of techniques such as proton nuclear magnetic resonance spectroscopy (1H NMR), electrospray ionization mass spectroscopy (ESI-MS), size exclusion chromatography (SEC), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electron paramagnetic resonance spectroscopy (EPR) were employed to characterize the produced PMMA and palladium nanoparticles (Pd NPs). The results revealed that Pd(CF3COO)2was firstly reduced by the excess of 1-octanethiol to form Pd NPs at the early stage of the polymerization, followed by the adsorption of 1-octanethiol on the surface of nanoparticles and subsequent generation of corresponding thiyl radicals to initiate the polymerization of MMA.Keywords:ultrahigh molecular weight;PMMA;polymerization;kinetics;mechanism
研究领域:
高分子化学
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材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
·
2024
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IF 2.9
Phichet Ketsamee,Alun Vaughan,Thomas Andritsch
This work highlights the potential of polypropylene (PP) as a power cable insulation material by blending with ultrahigh molecular weight polyethylene (UHMWPE), as well as blends filled with magnesium oxide (MgO) nanoparticles. In PP/UHMWPE blends, increasing the UHMWPE content up to 50 weight percentage (wt.%) increases the number of interfaces between PP and UHMWPE, promoting heterogeneous surface nucleation and strengthening the interfacial adhesion. This enhanced interfacial adhesion in PP/UHMWPE blends results in improved dielectric properties, particularly reduced relative permittivity, suppressed charge accumulation, and decreased dc electrical conductivity. In PP/UHMWPE/MgO nanocomposites, MgO nanoparticles are primarily observed at the interface between PP and UHMWPE in the PP phase. The presence of MgO does not function as a nucleating agent; instead, it acts as a compatibilizer, promoting the dispersion of UHMWPE and enhancing the interfacial adhesion between both polymers. The improved dispersion of UHMWPE results in the nonformation of phase co-continuity within the PP matrix; consequently, adding MgO up to 3 wt.% is insufficient to establish the interfaces forming percolating pathways. Thus, the good dispersion and compatibilizing effect of MgO between the PP and UHMWPE interfaces enhance interfacial adhesion and further improve the dielectric properties compared to the unfilled PP/UHMWPE blend counterparts.
研究领域:
材料科学
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电气工程
✓ 已验证
产品关联
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2022
·
IF 4.326
Qianbin Ni,Mei Chen,Yuming Chen,Wei Li,Qi Zhou,Jincheng Dai,Shuyao Ye,Binbo Jiang,Jingdai Wang,Yongrong Yang
Polyhedral oligomeric silsesquioxane (POSS) nanoaggregates can serve as a modifier of the MgCl2-supported Z-N catalyst, thus controlling the polymerization behavior and modifying the microstructure of the synthesized polymer. In this study, a series of POSS-modified MgCl2-supported Z-N catalysts were explored to reveal the relationship between the entanglement formation of ultrahigh-molecular-weight polyethylene (UHMWPE) and the adhesive effect control of hydroxy groups in POSSs. X-ray photoelectron spectroscopy (XPS) and CO in situ FTIR low-temperature adsorption technology were employed to investigate the catalytic surface structure. It was evidenced that POSSs can coordinate with the MgCl2 (110) plane, acting as adhesive of a cage structure to be in situ embedded into the MgCl2-based support. Therefore, the loaded TiCl4 active sites were isolated in the molecular scale on the MgCl2-based support and the entanglements were greatly suppressed thereof. The ″adhesion effect″ of the MgCl2 support can be controlled by adjusting the type (i.e., hydroxyl content) of POSS introduced, thereby suppressing entanglements to a greater extent. The MgCl2 support modified with POSS with no hydroxy groups endowed it with the optimum entanglement reduction effect. As a consequence, the as-synthesized polyethylene exhibits an overall promotion of the impact resistance (+14.1%), tensile strength (+13.9%), Young’s modulus (+16.8%), and break elongation (+10.5%), compared to those of UHMWPE synthesized from the POSS-free catalyst. In addition, the POSS-modified MgCl2-based catalyst shows more stable catalytic activity and responsiveness of molecular weight with hydrogen modulation, which exhibits great prospects of industrial application in polyethylene production.
研究领域:
材料科学
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高分子化学
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催化化学
✓ 已验证
DOI
高影响因子
EUROPEAN POLYMER JOURNAL
·
2025
·
IF 6.3
Shiyang Wang,Liting Wei,Xinglong Zhao,Lantian Li,Yuxin Gao,Shuang Chen,Yang Yang,Boping Liu,Yulong Jin
A series of mono-, bi- and tri-metallic catalysts including Ind 2 ZrCl 2 /silica, CrO x /VO x /silica and CrO x /VO x /Ind 2 ZrCl 2 /silica were synthesized for C 2 H 4 polymerization in this work. The results show that conventional cocatalyst TiBA could hardly activate Ind 2 ZrCl 2 /silica. However, under the assistance of the surface species over CrO x /VO x /silica, traces of TiBA (Al/metal ＜15, molar ratio) endowed the Zr species with moderate activity. The combined results of XPS, FTIR-pyridine-adsorption and DRS Uv–vis show that the Lewis acidic Cr and V sites could interact with Ind 2 ZrCl 2 and improve the electronic deficiency of Zr center, which is possible to promote zirconocene activation, though direct Si-O-Zr linkage was non-negligible, and redox between Cr(VI)/V(V) and zirconocene existed. The Zr species were responsible for ultra-high molecular weight polyethylene (UHMWPE) synthesis, and the relative content of UHMWPE fractions could be controllably regulated by polymerization temperature, partial pressure of hydrogen and the loading amount of Zr. Generally, these tri-metallic catalysts CrO x /VO x /Ind 2 ZrCl 2 /silica could synthesize trimodal HDPE/UHMWPE in-reactor blends with very broad molecular weight distribution. Meanwhile, owing to the excellent copolymerization ability of zirconcene, preferential distribution of the short chain branches along the ultra-high molecular weight (MW) chains for C 2 H 4 /1-hexene trimodal copolymers was achieved. The rheological results show that the fractions with extreme MW difference in the trimodal polyethylene (PE) exhibited excellent miscibility, and its superiority in processing and mechanical properties over the monomodal PE with similar MW was verified by rheological, tensile and impact tests.
研究领域:
材料科学
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高分子化学
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催化化学
✓ 已验证
产品关联
DOI
高影响因子
CLINICAL ORTHOPAEDICS AND RELATED RESEARCH
·
2019
·
IF 4.154
Yue Ren,Xin Wei,Song-Tao Wei,Fei-Yu Wang,Jing Wang,Jia-Zhuang Xu,Lu Xu,Rizwan M. Gul,Zhong-Ming Li
Background Synovial fluid components, especially lipids, can trigger oxidation of ultrahigh-molecular-weight polyethylene (UHMWPE) artificial joint components in vivo. The use of antioxidants such as vitamin E effectively diminishes the oxidative cascade by capturing free radicals and reducing the oxidation potential of UHMWPE implants. Using a thermo-oxidative aging method, we recently found that tea polyphenols can enhance the oxidation resistance of irradiated UHMWPE in comparison with commercial vitamin E. However, it is yet unknown whether tea polyphenols can reduce lipid-induced oxidation. Questions/purposes We explored whether tea polyphenol-stabilized UHMWPE would exhibit (1) lower squalene absorption; (2) stronger oxidation resistance; and (3) lower content of free radicals than vitamin E-stabilized UHMWPE under a physiologically-motivated in vitro accelerated-aging model. Methods Tea polyphenol (lipid-soluble epigallocatechin gallate [ ls EGCG]) and vitamin E were blended with UHMWPE powders followed by compression molding and electron beam irradiation at 100 and 150 kGy. Small cubes (n = 3, 60 mg, 4 × 4 × 4 mm 3 ) cut from the blocks were doped in squalene at 60°, 80°, 100°, and 120° C for 2 hours. Gravimetric change of the cubes after squalene immersion was measured to assess absorption. Thin films (n = 3, ∼60 μm) were also microtomed from the blocks and were doped at 120° C for 24 hours. Oxidation induction time (n = 3, 5 mg of material from the cubes) and incipient oxidation temperature (n = 3, thin films) were obtained to determine the oxidation stability. Signal intensity of the free radicals, obtained by electron spin resonance spectroscopy, was used to qualitatively rank the antioxidant ability of vitamin E and ls EGCG. Results Squalene absorption was comparable between ls EGCG/UHMWPE and vitamin E/UHMWPE at a given temperature and radiation dose. The oxidation induction time of 100 kGy-irradiated UHMWPE was increased with ls EGCG compared with vitamin E except at 120° C. For example, the oxidation induction time value of 100 kGy-irradiated ls EGCG/UHMWPE immersed at 60 o C was 25.3 minutes (24.2–27.8 minutes), which was 8.3 minutes longer than that of 100 kGy-irradiated vitamin E/UHMWPE which was 17.0 minutes (15.0–17.1 minutes) (p = 0.040). After squalene immersion at 120° C, the incipient oxidation temperature of 100 and 150 kGy irradiated ls EGCG/UHMWPE was 234° C (227–240° C) and 227° C (225–229° C), which was higher than vitamin E-stabilized counterparts with value of 217° C (214–229° C; p = 0.095) and 216° C (207–218° C; p = 0.040), respectively. The electron spin resonance signal of 150 kGy irradiated ls EGCG/UHMWPE was qualitatively weaker than that of 150 kGy irradiated vitamin E/UHMWPE. Conclusions ls EGCG-stabilized UHMWPE demonstrated higher oxidation resistance than vitamin E-stabilized UHMWPE after squalene immersion, likely because ls EGCG donates more protons to eliminate macroradicals than vitamin E. Clinical Relevance Our in vitro findings provide support that ls EGCG may be effective in protecting against oxidation that may be associated with synovial fluid-associated oxidation of highly crosslinked UHMWPE joint replacement components.
研究领域:
生物医学工程
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材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2021
·
IF 3.764
Mei Chen,Yuming Chen,Wei Li,Peng Liang,Congjing Ren,Binbo Jiang,Jingdai Wang,Yongrong Yang
A facilely catalytic approach to prepare weakly entangled ultra-high-molecular-weight polyethylene (UHMWPE) with a fine particle size is reported with the polyhedral oligomeric silsesquioxane (POSS)-modified MgCl2-based Ziegler–Natta catalyst. CO in situ FTIR spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and N2 adsorption and desorption experiments revealed that the POSSs can coordinate with the MgCl2(110) plane, acting as adhesives with a cage structure to be in situ embedded into the MgCl2-based support. This in situ embedding of POSS facilitated the uniform dispersion of POSS nanoparticles, contributing the isolation effect for active TiCl4 sites in the molecular scale, thus synthesizing the weakly entangled UHMWPE with exceptional activities. Simultaneously, the MgCl2-based catalysts afforded UHMWPE particles with small sizes, where POSS-modified catalysts brought the UHMWPE particle size down to below 200 μm, thanks to their considerable activities. To the best of our knowledge, this is the first time that nascent UHMWPE with a less entangled state and a fine particle size was synthesized. This combination of structural advantages enables substantial improvements in the toughness/stiffness/strength balance of nascent UHMWPE, especially for the impact strength which can reach 113.6 kJ/m2 with a relatively low molecular weight.
研究领域:
材料科学
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高分子化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2016
·Vol. 134
·期 7
·
IF 1.866
Mengyu Zhan,Siyu Li,Yi Zhong,Chunhui Shen,Shanjun Gao
Multistage emulsion polymerization was used to prepare ultra-high molecular weight foam regulator of low cost, with methyl methacrylate (MMA), butyl acrylate (BA), styrene (St) as main raw materials. Ubbelohde viscometer, dynamic light scattering, infrared and raman spectra, TEM, DSC, TGA, and GPC were all used to characterize constituent and structure, morphology, and molecular weight. As a result, when the ratio of soft monomer (BA) and hard monomer (St + MMA) is 1:3, MMA:St = 4:1, potassium persulfate (KPS): 0.15%, sodium hydrogen sulfite (SHS): 0.05%, azodiisobutyronitrile (AIBN): 0.15%, divinyl benzene (DVB): 0.3%, the final product terpolymer has obvious core-shell structure and ultra-high molecular weight ( M w = 1,400,000). This kind of foam regulator showed improvements in the melt strength, prevention of bubble coalescence and reduction on cost when compared with the traditional. Finally, the coefficients of poly (methyl methacrylate-butyl acrylate-styrene) terpolymer's Mark-Houwink equation were calculated with tetrahydrofuran (THF) solvent at 25 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44479.
研究领域:
高分子化学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Materials & Interfaces
·
2020
·
IF 8.758
Binbin Dong,Yahao Guo,Shuangjie Sun,Hao-Yang Mi,Ping He,Maxwell Fordjour Antwi-Afari,Chuntai Liu,Changyu Shen
High-performance low-cost superhydrophobic sponges are desired for selective recycling of leaking oils from open water. Herein, an ingenious method is proposed to fabricate an ultrathin superhydrophobic coating layer on a commercial sponge. The coating layer is composed of a shish–kebab-structured porous ultrahigh molecular weight polyethylene (UHMWPE) film that is fabricated from a UHMWPE/xylene solution by shear flow-induced crystallization. A strong relationship between the shish–kebab crystallite morphology and the superwetting performance is confirmed. The UHMWPE coating layer fabricated at a 900 rpm rotation rate possesses a lamellae size of 95.1 nm and a lamellae distance of 27.4 nm, which lead to a high water contact angle of 157° and a low contact angle hysteresis of 4.5°. The UHMWPE layer prepared in 4 min of treatment is thick enough to prevent the intrusion of water even under vacuum and remain superoleophilic. The developed UHMWPE-coated sponge (UCS) exhibited a high absorption capability of 70–191 g/g toward various oils and solvents, which is comparable with the neat melamine sponge. Its excellent compressibility and durability enabled fast recovery of absorbed oil with a high recovery rate (over 85%) by mechanical squeezing. The UCS could be assembled into small devices to selectively collect oil from open water and a water/oil mixture using a pump, which manifests its promising practical applicability. Apart from these extraordinary properties, the approach developed has the lowest material cost and the shortest processing time hitherto.
研究领域:
材料科学
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环境科学
✓ 已验证
DOI
高影响因子
RSC Advances
·
2019
·Vol. 9
·期 37
·21371-21380
·
IF 3.049
Huaming Wang,Jingshi Cao,Fubin Luo,Changlin Cao,Qingrong Qian,Baoquan Huang,Liren Xiao,Qinghua Chen
The potential prospect of expandable graphite (EG) in the development of polymer composites is severely limited by required large additions and poor interface compatibility with the polymer. Inspired by mussels, polydopamine (PDA) can be used as an effective interface modifier for EG to prepare ultra high molecular weight polyethylene (UHMWPE) composites with superior mechanical properties and high flame retardancy. The surface of expandable graphite (EG) was coated with a thin adhesive PDA film through self-polymerization of dopamine. The modified expandable graphite (EG@PDA) was combined with APP to prepare UHMWPE flame retardant composites. Compared with UHMWPE/APP/EG (with 20 wt% APP/EG), UHMWPE/APP/EG@PDA (with 20 wt% APP/EG@PDA) gives a decrement by 16.7% in limiting oxygen index, 29.7% in the peak of the heat release rate, 20.4% in total heat release and 49.3% in total smoke release, with an increment by 37% in tensile strength and 67.9% in elongation at break, respectively. It is suggested that the presence of PDA as an interface modifier can greatly improve the interfacial compatibility between EG and UHMWPE. Moreover, it can lead to forming more char residue and reducing the release of smoke particulates during combustion of the composites.
研究领域:
材料科学
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化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Soft Matter
·
2023
·Vol. 19
·期 29
·5459-5467
·
IF 3.4
Yang Sui,Yi Cui,Peng Wei,Chuanbo Cong,Xiaoyu Meng,Hai-Mu Ye,Qiong Zhou
Considering the molar mass between entanglements to be an intrinsic property of ultra-high molecular weight polyethylene (UHMWPE), the number of entanglements per chain increases with increasing molar mass, correspondingly making the UHMWPE intractable. Herein, we dispersed TiO2 nanoparticles with different characteristics into UHMWPE solutions to disentangle the molecular chains. Compared with the UHMWPE pure solution, the viscosity of the mixture solution declines by 91.22%, and the critical overlap concentration increases from 1 wt% to 1.4 wt%. A rapid precipitation method was utilized to obtain UHMWPE and UHMWPE/TiO2 composites from the solutions. The melting index of UHMWPE/TiO2 is 68.85 mg, which is in sharp contrast to that of UHMWPE which is 0 mg. We characterized the microstructures of UHMWPE/TiO2 nanocomposites using TEM, SAXS, DMA, and DSC. Accordingly, this significant improvement in processability contributed to the reduction of entanglements and a schematic model was proposed to explain the mechanism by which nanoparticles disentangle molecular chains. Simultaneously, the composite demonstrated better mechanical properties than UHMWPE. In summary, we provide a strategy to promote the processability of UHMWPE without sacrificing its outstanding mechanical properties.
研究领域:
材料科学
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纳米技术
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聚合物工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）