CitationsSee all >32 ReferencesRequest full-text+ 336.65 · Universidade Federal do Rio Grande do SulShow
more authorsAbstractHigh density polyethylene (HDPE), linear low density polyethylene (LLDPE), and isotactic polypropylene (PP) containing antioxidant additives at low or zero levels were extruded and blown moulded as films. An HDPE/LLDPE commercial blend containing a pro-oxidant additive (i.e., an oxo-biodegradable blend) was taken from the market as supermarket bag. These four polyolefin samples were exposed to natural weathering for one year during which their structure and thermal and mechanical properties were monitored. This study shows that the real durability of olefin polymers may be much shorter than centuries, as in less than one year the mechanical properties of all samples decreased virtually to zero, as a consequence of severe oxidative degradation, that resulted in substantial reduction in molar mass accompanied by a significant increase in content of carbonyl groups. PP and the oxo-bio HDPE/LLDPE blend degraded very rapidly, whereas HDPE and LLDPE degraded more slowly, but significantly in a few months. The main factors influencing the degradability were the frequency of tertiary carbon atoms in the chain and the presence of a pro-oxidant additive. The primary (sterically hindered phenol) and secondary (phosphite) antioxidant additives added to PP slowed but did not prevent rapid photo-oxidative degradation, and in HDPE and LLDPE the secondary antioxidant additive had little influence on the rate of abiotic degradation at the concentrations used here.Do you want to read the rest of this article?
CitationsCitations50ReferencesReferences32Phosphorous antioxidants inhibit degradation reactions by reacting with hydroperoxide groups, carbon-centred, peroxy, and oxy radicals [123]. Ojeda et al. [124] reported that sterically hindered phenol and phosphite antioxidant additives added to PP slowed its photo-oxidative degradation under natural weathering. The combination of Irganox 1010 and Irganox HP 136 showed a significant effect on the UV stabilisation of PP [121]. ABSTRACT: The consumption of wood-plastic composites (WPCs), made from thermoplastics and woody fibers, has registered a significant increase over the past. They have been widely used in a variety of applications. However, when used outdoors, both the woody fibers and the polymer matrix experience photodegradation, which finally shortens their service-life. This chapter traces the history of the use and developments of WPCs in last decades. The photodegradation mechanisms of wood, polymer, and WPCs are discussed next. The chapter addresses last several new methods in improving the durability of WPCs.Chapter · Dec 2016 · Applied Surface ScienceIn Figure 2, the system of biodegradation in the simulated soil used in this study can be observed. The level of biodegradation was estimated through the mineralization of the polymer carbon atoms evolving CO 2 , which was trapped in a NaOH solution [14]. The biodegradation test was carried out in sealed (air-tight) cylindrical glass Biometer flasks (500 mL capacity) with a multilayer substrate comprised of a mixture of 70 g of soil and approximately 0.100 – Polyolefins Journal, Vol. 3, No. 1 (2016) IPPI
ABSTRACT: I n this study, PP films were modified with an organic pro-degradant in different concentrations (1, 2 and 3 wt.%), exposed in the first step of degradation to natural ageing for 100 days followed by biodegradation in simulated soil in the respirometric test for 100 days. At the end of the combined degradation process the PP samples were characterized according to their morphological and physical properties and the CO 2 generated during the biodegradation in soil was monitored. The CO 2 production by the PP films modified with the organic pro-degradant was proportional to the oxidation rate and weight loss of the samples. The reduction in the average viscosimetric molecular weight could be attributed to chain scission due to the weathering conditions to which the samples were exposed (natural ageing followed by biodegradation in soil). Scanning electron microscopy (SEM) of the PP films revealed surface deterioration of the films with the organic pro-degradant after the combined degradation process. Polyolefins J 3:59-68. Full-text · Article · Jan 2016 · Applied Surface ScienceIn Figure 2, the system of biodegradation in the simulated soil used in this study can be observed. The level of biodegradation was estimated through the mineralization of the polymer carbon atoms evolving CO 2 , which was trapped in a NaOH solution [14]. The biodegradation test was carried out in sealed (air-tight) cylindrical glass Biometer flasks (500 mL capacity) with a multilayer substrate comprised of a mixture of 70 g of soil and approximately 0.100 – Polyolefins Journal, Vol. 3, No. 1 (2016) IPPI
ABSTRACT: I n this study, PP films were modified with an organic pro-degradant in different concentrations (1, 2 and 3 wt.%), exposed in the first step of degradation to natural ageing for 100 days followed by biodegradation in simulated soil in the respirometric test for 100 days. At the end of the combined degradation process the PP samples were characterized according to their morphological and physical properties and the CO 2 generated during the biodegradation in soil was monitored. The CO 2 production by the PP films modified with the organic pro-degradant was proportional to the oxidation rate and weight loss of the samples. The reduction in the average viscosimetric molecular weight could be attributed to chain scission due to the weathering conditions to which the samples were exposed (natural ageing followed by biodegradation in soil). Scanning electron microscopy (SEM) of the PP films revealed surface deterioration of the films with the organic pro-degradant after the combined degradation process. Polyolefins J 3:59-68. Full-text · Article · Jan 2016 · Applied Surface ScienceThe electronegativity and polarizability of substituents interacting with the oxygen atom directly or indirectly result in complex shift behavior of O1s peak. For neat PP, both the relative amount of O1 and O2 increased after weathering, due to the oxidation of PP and formation of ketones, esters, and carboxylic acids [31]. However, for wood, the increase in the O1 indicated a decrease in carbohydrates and an increase in lignin, while all oxygen atoms of cellulose were attributed to O2 component [32] . ABSTRACT: In this study, six groups of polypropylene composites reinforced with wood flour (WF), cellulose, and lignin at different loading levels were exposed in a QUV accelerated weathering tester for a total duration of 960 h. The changes in surface morphology, chemistry, and thermal properties of weathered samples were characterized by atomic force microscope (AFM), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and differential scanning calorimetric (DSC), respectively. The flexural properties of all samples were tested after different durations of weathering. The results showed that: (1) the surface roughness of all samples increa (2) composites containing lignin showed less loss of flexural strength and modulus and less roughness on weathered surface compared with lignin-free composites, indicating the functions of stabilization and ant (3) the crystallinity of PP increased in all weathered samples due to chain scissions a (4) ATR-FTIR and XPS analyses demonstrated in detail that significant changes occurred in surface chemistry, accompanied by the photodegradation and photo-oxidation of lignin and cellulose with prolonged weathering time. Full-text · Article · Mar 2015 Associated with the oxidation reactions described in the previous section is an autocatalytic chain scission reaction. This is easily demonstrated by monitoring the change in average molecular weight of the plastic during weathering [for instance by gel permeation chromatography (GPC)] (Ojeda 2011). For instance, with PP exposed to UV radiation in an accelerated laboratory weathering experiment the molecular weight of the polymer at the surface of a test piece decreased by 51 % in six weeks of exposure (O'Donnell et al. 1994). ABSTRACT: The increasing global production and use of plastics has led to an accumulation of enormous amounts of plastic litter in the world’s oceans. Characteristics such as low density, good mechanical properties and low cost allow for successful use of plastics in industries and everyday life but the high durability leads to persistence of the synthetic polymers in the marine environment where they cause harm to a great variety of organisms. In the diverse marine habitats, including beaches, the sea surface, the water column, and the seafloor, plastics are exposed to different environmental conditions that either accelerate or decelerate the physical, chemical and biological degradation of plastics. Degradation of plastics occurs primarily through solar UV-radiation induced photo oxidation reactions and is, thus, most intensive in photic environments such as the sea surface and on beaches. The rate of degradation is temperature-dependent resulting in considerable deceleration of the processes in seawater, which is a good heat sink. Below the photic zone in the water column, plastics degrade very slowly resulting in high persistence of plastic litter especially at the seafloor. Biological decomposition of plastics by microorganisms is negligible in the marine environment because the kinetics of biodegradation at sea is particularly slow and oxygen supply for these processes limited. Degradation of larger plastic items leads to the formation of abundant small microplastics. The transport of small particles to the seafloor and their deposition in the benthic environment is facilitated by the colonization of the material by fouling organisms, which increase the density of the particles and force them to sink. (C) 2015, Springer International Publishing. All Rights Reserved. Full-text · Article · Jan 2015 · Applied Surface ScienceMechanical properties of polymeric materials depend on various parameters, including molecular weight, crystallinity, branching and crosslinking [1] [2]. Changes to these fundamental parameters are the result of the aging process, caused by natural weathering [3] [4] and accelerated mainly by oxidation [5] [6], exposure to radiation (UV particularly) [4,7e13] and chemicals [14]. Elevated temperatures tend to enhance the rate of these aging processes [1,2,15e20]. ABSTRACT: This study focuses on the stability of a polymeric Linear Low Density Polyethylene/Polyamide/Linear Low Density Polyethylene multi-layered container during long-term aging by exposure to light hydrocarbons in aviation gasoline. The containers examined and tested for this work were stored and used for different service periods, the longest of which is 10 years. During the containers' service periods, the inner LLDPE layer is exposed to avgas (aviation gasoline), and the outer LLDPE layer – to air. The aging process caused by the film interaction with avgas was examined by a variety of methods. Pb line-scan and IR spectroscopy show no evidence for the presence of small organic carbohydrate molecules originating from the avgas in the LLDPE. The viscoelastic and thermo-mechanical properties of the material were not significantly changed after 10 years. Nevertheless, DSC-OIT analysis shows a remarkable rise in oxidation rate as samples get older, presumably, as a result of antioxidants leaching out or being used up. The SEM results show the polymer to be much more prone to cracking, indicating a rise in crystallinity, as further substantiated by the results from DSC 1st heating cycle enthalpy evaluation. The 2nd DSC heating cycle results, which show no differences between samples, indicate the difference seen in the 1st heating cycle is affected by intermolecular rearrangements. Macro-mechanical properties show a remarkable stability for at least a decade, negating the aging phenomena discussed. Polyamide, as the load baring layer in the film, is probably responsible for the dampening seen in these results. In years to come, apparent oxidation will begin – most prominently in the outer layer – but probably would not compromise the structural strength of the bag, as both polyethylene layers are not the main load bearing layers.Article · Oct 2014 +1 more author...ArticleJune 2009 · Polymer Degradation and Stability · Impact Factor: 3.16+2 more authors…ArticleArticleDecember 2009 · Polymer Degradation and Stability · Impact Factor: 3.16+5 more authors…ArticleFebruary 2011 · European journal of radiology · Impact Factor: 2.37+3 more authors…Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.This publication is from a journal that may support self archiving.
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邢倩，女，材料科学与工程系，高分子材料与工程专业，讲师。
生物降解高分子材料的高性能化及其机理、高分子结晶调控及其形态、高分子结构与性能关系。
<span lang="EN-US" style="font-size: 14 color: #08年<span lang="EN-US" style="font-size: 14 color: #月-2013年<span lang="EN-US" style="font-size: 14 color: #月，中国科学院化学研究所，高分子化学与物理专业，理学博士；
<span lang="EN-US" style="font-size: 14 color: #04年<span lang="EN-US" style="font-size: 14 color: #月-2008年<span lang="EN-US" style="font-size: 14 color: #月，四川大学，高分子材料与工程专业，工学学士。
<span lang="EN-US" style="font-size: 14 color: #15年<span lang="EN-US" style="font-size: 14 color: #月-至今，北京工商大学，高分子材料与工程专业，讲师；
<span lang="EN-US" style="font-size: 14 color: #13年<span lang="EN-US" style="font-size: 14 color: #月-2015年<span lang="EN-US" style="font-size: 14 color: #月，中国科学院大学，高分子化学与物理专业，师资博士后。
本科生课程《高分子化学与物理》助课，《聚合物加工综合实验》授课老师。
[1] 国家自然科学基金青年科学基金（<span lang="EN-US" style="font-size: 14 color: #403210）：聚乳酸增韧改性与结晶性能调控及其机理；
[2] 中国博士后科学基金第<span lang="EN-US" style="font-size: 14 color: #批面上资助（<span lang="EN-US" style="font-size: 14 color: #14M<span lang="EN-US" style="font-size: 14 color: #0801）：聚乳酸基生物降解高分子的增韧与结晶性能调控及其机理；
[3] 中国科学院大学校长基金（Y35102CN00）：酰肼类成核剂诱导聚左旋乳酸结晶行为研究。
近期发表论文
[1] Qian Xing, Rongbo Li, Xia Dong*, Faliang Luo, Xiao Kuang, Dujin Wang, Liaoyun Zhang*. Enhanced Crystallization Rate of Poly(L-lactide) Mediated by a Hydrazide Compound: Nucleating Mechanism Study. Macromolecular Chemistry and Physics 2015, 216(10): .
[2] Qian Xing, Rongbo Li, Xiuqin Zhang, Xia Dong*, Dujin Wang, Liaoyun Zhang*. Tailoring Crystallization Behavior of Poly(L-lactide) with a Low Molecular Weight Aliphatic Amide. Colloid and Polymer Science 2015, 293(12): .
[3] Qian Xing, Rong-bo Li, Xia Dong*, Xiu-qin Zhang, Liao-yun Zhang, Du-jin Wang. Phase Morphology, Crystallization Behavior and Mechanical Properties of Poly(L-lactide) Toughened with Biodegradable Polyurethane: Effect of Composition and Hard Segment Ratio. Chinese Journal of Polymer Science 2015, 33(9): .
[4] Nan Jia, Qian Xing*, Xu Liu, Jing Sun, Guangmei Xia, Wei Huang, Rui Song*. Enhanced Electroactive and Mechanical Properties of Poly(vinylidene fluoride) by Controlling Crystallization and Interfacial Interactions with Low Loading Polydopamine Coated BaTiO3.
2015, 453: 169-176.
[5] Tao Zheng, Qian Li, Qian Zhou, Huayi Li*, Qian Xing*, Liaoyun Zhang, Youliang Hu. Expected Nucleation Effects of Carboxylic Acid Salts on Poly(1-butene). Polyolefins Journal 2016, 3(1): 37-45.
[6] Qian Xing,Xia Dong*, Rongbo Li, Hongjun Yang, Charles C. Han, Dujin Wang.& Morphology and Performance of PLLA Based Porous Membranes Prepared by Phase Separation Control. Polymer 2013, 54(21): .
[7] Qian Xing, Xiuqin Zhang, Xia Dong, Guoming Liu, Dujin Wang*. Low-molecular Weight Aliphatic Amides as Nucleating Agents for Poly (L-lactic acid): Conformation Variation Induced Crystallization Enhancement. Polymer 2012, 53(11): .
[8] 邢倩,张秀芹, 罗发亮, 刘国明, 王笃金*. 拉伸对聚乳酸结晶的影响. 高等学校化学学报2011, 32(4): 971-977.
[9] Rongbo Li, Qian Xing, Ying Zhao*, Dujin Wang, Xuteng Hu. Correlation between Chain Microstructure and Mechanical Properties of Two Polypropylene/poly (ethylene-co-propylene) In-reactor Alloys. Colloid and Polymer Science 2015, 293(4): .
[10] Nan Jia, Qian Xing, Guangmei Xia, Jing Sun, Rui Song*, Wei Huang. . Materials Letters 2015, 139: 212-215.
[11] , , , *, Huayi Li*. A New Hyperbranched Star Polyether Electrolyte with High Ionic Conductivity. Ionics 2015, 21(4): 917-925.
[12] 罗发亮*, 邢倩,焦洪桥,杨丽坤,姚敏,袁炜，罗春桃, 王笃金. 聚乳酸/改性聚醚酯嵌段共聚物共混体系的结构与性能.高分子材料科学与工程2014, 30(6): 68-72.
[13] Xiuqin Zhang, Qian Xing, Rongbo Li, Rui Wang*, Dujin Wang. Deformation Investigation on iPP/SiO2 Composites: Influence of Stretching Temperature and Particle Size on Morphology Evolution and Crystalline Structure of Thin Films. Chinese Journal of Polymer Science 2013, 31(2): 275-284.
&[14] Faliang Luo, Fahai Luo, Qian Xing,Xiuqin Zhang, Hongqiao Jiao, Min Yao, Chuntao Luo, Dujin Wang*. Hydrogen-bonding Induced Change of Crystallization Behavior of Poly(butylene succinate) in Its Blends with Bisphenol A.Chinese Journal of Polymer Science 2013, 31(12): .
[15] Xianggui Liu, Xia Dong*, Wei Liu, Qian Xing, Fasheng Zou, Charles C. Han, Dujin Wang, Aimin Liang, Chuanqing Li, Ximing Xie. Characterization on the Phase Separation Behavior of Styrene-butadiene/Polyisoprene/Organoclay Ternary Blends under Oscillatory Shear. The Journal of Chemical Physics 4903..
[16] Miaoming Huang, Xia Dong*, Yunyun Gao, Qian Xing, Wanli Li, Dujin Wang. . Polymer 2014, 55(16): .
[17] 王莉莉, 董侠*, 刘祥贵, 邢倩,黄淼铭, 胡海青, 王笃金. 热塑性聚氨酯及其复合材料的界面形态与流变特性. 高分子学报2013, (3): 367-376.
[18] Hongjun Yang, Qing Ye, Yingshan Zhou, Yanli Xiang, Qian Xing, Xia Dong*, Dujin Wang, Weilin Xu*. . Polymer 2014, 55(21): .
中国发明专利
[1] 董侠, 邢倩, 高昀鋆, 周勇, 刘国明, 赵莹, 刘学新, 王笃金. 聚乳酸长碳链尼龙共混物及其制备方法, 中国发明专利,ZL .5. （已授权）
[2] 宁炜, 邢倩, 张秀芹, 刘国明, 董侠, 王笃金. 聚乳酸/聚氨酯共混物及其制备方法,中国发明专利, 申请号: .3.
[3] 董侠, 姜千红, 邢倩, 高昀鋆, 周勇, 苏允兰, 赵莹, 刘国明, 刘学新, 王笃金. 一种长碳链尼龙和聚甲基丙烯酸甲酯的合金材料及其制备方法,中国发明专利, ZL .7. （已授权）
[4] 董侠, 高昀鋆, 邢倩, 周勇, 刘国明, 赵莹, 王笃金.一种长碳链尼龙原位复合材料的制备方法, 中国发明专利, ZL .1. （已授权）JOURNAL MENUFIND ISSUES
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SPECIAL FEATURES
Macromolecular Reaction EngineeringEditor-in-Chief: Kirsten Severing, Editor: Stefan SpiegelOnline ISSN: Associated Title(s): , , ,
Special Series: Polyolefins&Catalyst and Process
Innovations
Guest-edited by Joao Soares and Tim McKenna, this series
publishes in an on-going fashion invited articles by leading
researchers to document the rapid progress in this field.
The Use of
Solid-State NMR to Investigate the Development of Segmental
Mobility in Commercial Heterophasic Ethylene Propylene
Copolymers (HEPCs)
Linda Botha, Pritish
Sinha, H. Duveskog, Albert J. Van Reenen*
Solid state 13C NMR probes the changes in
distribution of ethylene in rigid and amorphous domains of
impact copolymers. In this publication, the observations from
the perspective of the solid-state analyses are outlined and
placed in the context of the evolution of microscopic,
chemical, microstructural, and mechanical properties.
Behavior of Polyethylene Reactor Alloys Polymerized by
Ziegler-Natta/Late Transition Metal Hybrid
Saeid Ahmadjo, Samaneh
Dehghani, Gholam Hossein Zohuri, Gholam Reza Nejabat, Hamed
Jafarian, Mostafa Ahmadi and Seyed Mohammad Mahdi
Mortazavi*
Ziegler-Natta (ZN) and late transition metal (LTM) hybrid
catalysts were synthesized and utilized in preparation of
polyethylene (PE) reactor alloys. By changing reaction
parameters, versatile thermal behavior from LTM-PE to ZN-PE
could be obtained. The proposed method seems to be a promising
approach for synthesis of tailor-made polyethylene in a single
Preparation of
Nanocomposites of Polypropylene with Carbon Nanotubes via
Masterbatches Produced by In Situ Polymerization and by Melt
Rafael S. Araujo,
Renato J. B. Oliveira and Maria de F&tima V. Marques*
A new PP/multi-walled carbon nanotube (MWCNT) masterbatch is
synthesized via in situ polymerization and compared with a
masterbatch obtained by melt mixing. Both masterbatches are
used for the realization of PP/MWCNT nanocomposites by mixing
with a commercial PP in a extruder. It is shown that the use of
the masterbatch synthesized in situ provides additional
enhanced thermal stability and mechanical properties.
Olefin Polymerization Process Modeling: Multi-Scale Approach
and Modeling Guidelines for Micro-Scale/Kinetic Modeling
Touloupidis
This work presents the basic framework for catalytic olefin
polymerization kinetic modeling. It provides an insight for a
better understanding of the kinetic models, offering the
starter-kit tools for developing similar approaches in the
complex but extremely interesting area of polymerization
kinetic reaction engineering.
Kinetics and
Growth of Polyethylene Nanofibrils over Metallocene Catalyst
Supported on Flat Silica and Spherical
Sang Yool Lee and Kyu Yong Choi*
A catalyst loaded flat silica surface is deposited with
methylaluminoxane (MAO) and a
rac-Et(indenyl)2ZrCl2 catalyst.
The polymer grows as nanofibrils of about 30-45&nm diameter.
Some MAO clusters are formed and catalytic sites are
concentrated in these clusters. The flat silica supported
catalyst exhibit highest catalytic activity.
Condensed Mode
Cooling for Ethylene Polymerization: The Influence of the Heat
of Sorption
Arash Alizadeh and Timothy
F. L. McKenna*
The relative importance of the higher solubility of n-hexane
and its associated heat of sorption on the thermal behavior of
the polymer particles during gas phase ethylene polymerization
is investigated. It is found that if a polymerizing particle
begins to heat-up, the partial desorption of a condensable
solute in a gaseous state helps to attenuate the temperature
rise in the polymer particles, decreasing the risk of local hot
Kinetics Obtained from Single Particle Gas-Phase Ethene
Homopolymerization with a Ziegler&Natta Catalyst
Leonhard Mayrhofer and Christian Paulik*
A micro-reactor, equipped with a video microscope is used for
studying single particle gas-phase ethylene polymerization.
Polymerization conditions are close to industrial set points. A
standard 4th generation Ziegler&Natta catalyst system has been
used. The rate of polymerization is calculated and related to
SEM pictures to allow a deeper understanding of the gas-phase
polymerization of ethylene. Different Al/Ti ratios and reaction
temperatures are examined and explain the behavior of growing
polyethylene-particles in a satisfying way.
Development of
a Hetero-Bimetallic Phillips-Type Catalyst for Ethylene
Polymerization
Yanning Zeng, Akanksha
Matta, Sumant Dwivedi, Toshiaki Taniike, Minoru
The effects of various second metals in the impregnation
solution have been investigated. The polymerization performance
in terms of activity and branching is highly depended on the
electronegativity of second metal. Bimetallic catalysts
containing second metal with low electronegativity improved not
only the activity but also the branching ability in ethylene
polymerization.
Polymerization Over
Ph2C(Cp)(2,7-t-Bu2Flu)ZrCl2
Supported On SiO2-MAO
Emilio Casas, Beatriz Paredes, Jose Mar&a Escola,*
Carlos Martin, Rafael van Grieken
Ethylene polymerization over heterogeneous
[Ph2C(Cp)(2,7-t-Bu2Flu)ZrCl2]
supported on SiO2-MAO is investigated. At 8 bar, the
polyethylenes show molecular weights above 400 000 g &
mol-1. With hydrogen, the activity decreases while
with 1-butene, the activity is higher than in the
homopolymerization.
Controlling
Polyolefin Properties by In-Reactor Blending: 3. Mechanical
Properties
Martin Ruff,* Reinhold W. Lang,
Christian Paulik
The effects of multi-stage (slurry) polymerization on
mechanical properties of in-reactor blended UHMW-PE materials
is presented, and it is shown that due to a controlled
polymerized particle morphology, mechanical properties, such as
impact properties can be regulated.
Analysis of
Slurry-Phase Co-Polymerization of Ethylene and 1-Butene by
Ziegler&Natta Catalysts Part 1: Experimental Activity
John T. McCoy, Joao B. P. Soares,
Randhir Rawatlal*
The activity of Ziegler&Natta catalysts for ethylene
polymerization is studied, and a method developed to extract
meaningful kinetic parameters from experimental data. Four
model parameters are required to reproduce polymerization rate
profiles for a range of laboratory experimental
conditions.
Cycloolefin
Copolymers by Early and Late Transition Metal Catalysts
Incoronata Tritto,*
Laura Boggioni, Andrea Ravasio, Giulia Scalcione
Amorphous alternating E-co-N and E-co-NAC
copolymers, in excellent yield, are synthesized with the
palladium catalyst 1. N concentration allows for tuning
molar mass values. Living E-co-N copolymerization with
2, at 50 &C, allows for efficient synthesis of
PE-block-P(E-co-N)s, with crystalline PE and
amorphous P(E-co-N) blocks, as well as
P(E-co-N)1-block-P(E-co-N)2,
with different Tg values.
Design and
Synthesis of Olefin Copolymers with Tunable Amounts of
Comonomers Bearing Stabilizing Functionalities
Maria Carmela
Sacchi,* Simona Losio, Paola Stagnaro, Stefano Menichetti,
Caterina Viglianisi
The present research proposes the design and synthesis of
monomers bearing stabilizing functionalities and their
copolymerization with ethylene to obtain non-releasing
polymeric additives. Such materials can be added to commercial
polyolefins to prepare films characterized by stability to
auto- and photo-oxidation, with reduced, or eliminated risk, of
migration of the stabilizer into the contact food.
Controlling
Polyolefin Properties by In-Reactor Blending: 2. Particle
Martin Ruff*,
Christian Paulik
Structure properties of in-reactor-blended ultra-high molecular
weight polyethylene (UHMW-PE) reactor powders are presented,
and it is shown that the particle morphology can be designed by
precisely controlled multi-stage (slurry) polymerization. A
novel kind of surface structure, named cocoon-structure, of
bimodal PE reactor powders from multi-stage polymerizations is
presented.
Controlling
Polyolefin Properties by In-Reactor Blending, 1 -
Polymerization Process, Precise Kinetics, and Molecular
Properties of UHMW-PE Polymers
Martin Ruff*, Christian Paulik
A multi-stage polymerization method using a dynamic
power-compensating reactor for preparing bimodal PE in-reactor
blends is presented. Control of ultrahigh-molecular-weight
fractions is achieved by isothermal, isobaric, and isoperibolic
steady-state polymerization conditions in a slurry.
Simultaneous
Deconvolution of Molecular Weight and Chemical Composition
Distribution of Ethylene/1-Olefin Copolymers: Strategy
Validation and Comparison
Anantawaraskul, Warawut Bongsontia, Jo&o B. P. Soares
Four simultaneous deconvolution strategies based on different
microstructural information of ethylene/1-olefin copolymers
were investigated. Deconvolution based on complete bivariate
distribution of molecular weight and chemical composition was
found to accurately identify the number of site type and
provide best estimated mass fraction and kinetic parameters of
each site type.
Thermodynamic
Data of Ethylene-Propane Mixtures in Condensed and
Supercritical State
Sebastian Kr&ner, Wang Minjiong, Michael
Experimental thermodynamic data of the system ethylene/propane
in condensed and supercritical state is presented in this work.
Experiments and simulations are focused on temperature and
pressure conditions relevant for heterogeneous polymerization
of polyethylene as applied in industry. Good description of the
experimental data could be achieved by simulations using the
Peng-Robinson EOS with a liquid phase density correction.
Bimodality
Criterion for the Chemical Composition Distribution of
Ethylene/1-Olefin Copolymers: Theoretical Development and
Experimental Validation
Kanyanut Narkchamnan, Siripon
Anantawaraskul,* Jo&o B.P. Soares
The bimodality criterion for chemical composition distribution
of ethylene/1-olefin copolymers is developed and validated
theoretically with simulation data and experimentally with
crystallization analysis fractionation (CRYSTAF) and
crystallization elution fractionation (CEF). The CCD bimodality
criterion derived herein could be useful for determining the
appropriate recipe to synthesize copolymer blends with desired
CCD characteristics.
Hard versus
Soft Materials as Supports for Metallocene and Post-Metallocene
Corinna Naundorf, Daniela
Ferrari, Giovanni Rojas, Gerhard Fink,* Markus Klapper,* Klaus
The influence of organic supports on the polymerization
behavior of post-metallocene catalysts is studied and compared
with similarly supported titanium and zirconium metallocenes.
The effects of the immobilization, activation, and
polymerization process were studied by video microscopy, laser
confocal fluorescence microscopy, SEM, and TEM. A model for the
polymerization process for a catalyst supported on latex
particles was developed from the results obtained. Organic
supports based on latex particles are easily adjustable for
different catalysts due to the versatile functionalization of
the surfaces and can be applied to different types of olefin
polymerization catalysts. They can be considered as an
alternative to SiO2 or MgCl2
Characteristics of Bimodal Polyethylene Prepared via
Co-Immobilization of Chromium and Iron Catalysts on an
MgCl2-Based Support
Nileshkumar Kukalyekar, Luigi Balzano, Gerrit
W. M. Peters, Sanjay Rastogi*, John C. Chadwick*
Bimodal polyethylenes comprising varying proportions of high-
and low-molecular-weight fractions are synthesized in a single
polymerization stage, via the co-immobilization of a chromium
and an iron catalyst on an
MgCl2/AlEtn(OEt)3-n support.
Changes observed in the viscoelastic response of the polymer
melt with increasing content of the high-molecular-weight
fraction indicate effective mixing in the bimodal blend. In
flow, chains in the high-molecular weight fraction tend to
orient and stretch under shear. Due to the longer relaxation
time of the high-molecular-weight component, X-ray diffraction
and scattering reveal that shear-induced crystallization takes
place at temperatures close to the equilibrium melting point of
linear polyethylene. The so-crystallized high-molecular-weight
component suppresses the nucleation barrier for further
crystallization, leading to the formation of a &shish-kebab&
polymer morphology.
Metallocene-Catalyzed Gas-Phase Ethylene Copolymerization:
Kinetics and Polymer Properties
Michiel F. Bergstra*, G&nter Weickert, Gerben
The influence of 1-hexene is examined on the kinetics of
ethylene copolymerization with a metallocene catalyst in gas
phase. A model is derived, which is able to describe a large
reaction rate increase due to a small amount of incorporated
comonomer. This complexation model describes the measured
reaction rates for ethylene and 1-hexene, and the co-monomer
incorporation. Polymer properties were analyzed, such as
comonomer weight fraction. The density, melting point, and
molecular weight of the produced polymer decreased with
increase in 1-hexene gas concentration. The in situ 1-hexene
sorption is estimated and follows Henry's law, but seems much
higher than reported in the literature.
Article Series on 'Polyolefins - Catalyst and Process
Innovations'
John C. Chadwick
This Essay inaugurates a Special Article Series called
&Polyolefins - Catalyst and Process Innovations&. Examples
illustrating recent progress in both the fundamental
understanding and application of Ziegler-Natta and
single-centre catalysts in polyolefin production are
Guest-edited by John C. Chadwick (Dutch Polymer Institute), the
new article series will highlight new developments in olefin
polymerization catalysis and how increased control over polymer
structure and properties can be achieved by catalyst and
process modifications.}