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1.
H. Nabil 《International Journal of Polymer Analysis and Characterization》2014,19(2):159-174
This article deals with blends based on natural rubber (NR) and recycled ethylene-propylene-diene rubber (R-EPDM). Natural rubber latex (NRL) was introduced into the blends to enhance interfacial adhesion between NR and R-EPDM. A new route of compounding was also suggested. The blends were prepared by mixing R-EPDM and other additives in NRL before blending with natural rubber on a two-roll mill. By applying this method, the homogeneity of the blends and cross-linking distribution are significantly improved. The blends exhibited superior state of cure, swelling resistance, mechanical properties and dynamic mechanical properties. The degree of entanglement between NR and R-EPDM also increased after NRL modification. 相似文献
2.
长碳链聚酰胺(LCPA)作为聚酰胺的特殊品种,较长的亚甲基链和极性酰胺基团使其兼具聚烯烃和聚酰胺的双重特性.在加工或使用过程中,拉伸诱导结晶现象对长碳链聚酰胺及其共聚物的强度和弹性行为具有重要影响,深入认识其在外场下的微观结构响应对该材料的设计及制备具有重要意义.围绕拉伸诱导结晶作用,该专论主要基于本团队2010年以来在长碳链聚酰胺及其共聚物的拉伸诱导结晶工作,并综述了国内外的相关研究,涉及拉伸诱导结晶现象、拉伸诱导结晶的影响因素、拉伸诱导结晶与力学性能的构效关系及拉伸诱导结晶的表征方法等方面. 相似文献
3.
利用快速增压和淬火2种方法分别制备了非晶聚醚醚酮(PEEK), 并利用二维广角X射线衍射(WAXD)研究了2种非晶样品在不同拉伸温度(Td)和不同应变速率(v)条件下的结晶行为. 结果表明, 在相同拉伸温度及应变速率条件下, 快压样品的临界结晶应变明显低于淬火样品; 随着拉伸温度和应变速率的升高, 2种样品的临界结晶应变均逐渐降低; 在相同应变条件下, 拉伸温度对PEEK材料结晶度的影响很大, 而应变速率对其影响较小. 相似文献
4.
Karger-Kocsis J. Moskala E. J. Shang P. P. 《Journal of Thermal Analysis and Calorimetry》2001,63(3):671-678
The toughness of amorphous copolyester sheets was assessed by the essential work of fracture (EWF) concept. While the yielding-related
work of fracture terms did not change significantly, the necking-related parameters strongly decreased with decreasing entanglement
density of the copolyesters having different amounts of cyclohexylenedimethylene (CHDM) units in their backbones. Furthermore, copolyesters with high CHDM content and thus less entanglement density showed full recovery of the necked region beyond the glass transition temperature,
i.e. the ‘plastic’ zone in the related specimens formed by cold drawing and not by true plastic deformation. By contrast,
the copolyester with negligible amount of CHDM did not show this shape recovery. Modulated differential scanning calorimetry (MDSC) revealed that the necking in the latter
system was accompanied by strain-induced crystallization. The superior work hardening in the necking stage of the respective
poly(ethylene terephthalate) (PET) specimens can thus be ascribed to stretching of the entanglement network with superimposed crystallization.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(43):13625-13629
Macromolecular crystallization has many implications in biological and materials science. Similar to the crystallization of other molecules, macromolecular crystallization conventionally considers a critical nucleus, followed by crystallographic packing of macromolecules to drive further crystal growth. Herein, we discover a distinctive macromolecular crystallization pathway by developing the concept of a macromolecular mesocrystal. This nonclassical polymer crystallization occurs through the mesoscale self‐assembly of (bio)macromolecular nanocrystals. The new concept for macromolecular crystallization presented herein is fundamental and relevant to many fields, including materials science, chemistry, biomimetics, nanoscience, and structural biology. 相似文献
6.
以角鲨烯作为天然橡胶的模型物合成了ATRP引发剂,即先通过双键的部分环氧化得到环氧化角鲨烯(ESq),ESq再与2-溴代异丁酸发生开环反应合成溴功能化角鲨烯(ESq-Br).采用FT-IR和1 H-NMR研究了ESq与ESq-Br的结构,并结合GC-MS和13C-NMR分析了环氧基、溴功能基等官能团的分布情况.结果表明:ESq中含有3种环氧结构,且环氧基是均匀分布的;环氧基开环的同时伴随着重排副反应,通过研究剩余环氧基的分布,可推测ESq-Br中溴功能化单元(即引发点)的分布也是均匀的. 相似文献
7.
Seng-Neon Gan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1939-1948
Abstract Natural rubber exhibits different storage properties when compared with synthetic polyisoprenes. Stored over an extended period of a few months, natural rubber is found to become progressively harder while the synthetic rubber is known to soften. This phenomenon of spontaneous crosslinking of natural rubber in storage is of considerable importance since it affects the processing properties. The process of storage hardening has been actively investigated and is believed to involve abnormal groups in the rubber molecules. This paper reviews the various proposals by different workers involving aldehyde, epoxide, and amino acids. Our recent results show that amino acids react with certain abnormal groups in rubber at the latex stage. The net effect of the reaction is to functionalize the rubber with carboxylic, hydroxylic, and amine groups in addition to the original abnormal groups. Storage of the dry rubber could lead to slow crosslinking reactions which are accelerated by anhydrous conditions. 相似文献
8.
针对锂离子电池内耦合电化学反应的多物理传输过程,采用光滑粒子水力学数值技术,开发了可以考虑电极(包括隔膜)介观微结构的数值模型.以电极中固体活性物颗粒尺寸为主要考虑参数,初步探讨了该模型用于电极介观微结构设计的可行性.模型模拟得到放电过程中电池内部Li/Li+浓度场、固/液相电势场以及交换流密度等微观细节分布,以及电池宏观性能如输出电压等,据此可以分析并揭示电池放电过程的基础物理化学机制、电池宏观性能与构成电极的固体活性物颗粒尺寸之间的关联.研究还发现:当阴、阳极固体活性物颗粒尺寸均较小时,固体活性物颗粒内部Li分布更为均匀,电化学反应更均匀发生,电池输出电压最高. 相似文献
9.
Ground rubber powder (GRP) with three different sizes was incorporated into nature rubber matrix with different loading. Cure characteristics, swelling behaviour, crosslink density, tensile fractured surface, and mechanical properties have been studied. Based on the cure characteristics, it is evident that the processability of the rubber compounds has not changed obviously with the different GRP loading. The introduction of GRP in virgin rubber leads to the increase in swelling degree and the decrease in crosslink density. Tensile strength, hardness and abrasion resistant deteriorate with the increase of GRP loading, but the tear resistance gets better. If the ground rubber particles are smaller, the properties are more similar to the virgin rubber. Because of the phase separation of the GRP and matrix, the properties get worse with the bigger ground rubber powder. 相似文献
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11.
Pham Huu Ly 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1931-1937
Abstract This paper deals with the grafting of acyl chloride capped liquid natural rubber (LNR–COCl) onto carbon black by the reaction of the acyl chloride group with the phenolic hydroxyl group on the surface. LNR–COCl was prepared by the reaction of hydroxyl-terminated liquid natural rubber (HTNR) with adipoyl dichloride. The percentage of grafting was estimated to be 18–21% depending on the grafting temperature and the molecular weight of HTNR used. It increased with an increase in the molecular weight of LNR–COCl. The LNR grafted onto carbon black was investigated by IR spectroscopy and by hydrolysis with a dilute THF solution of KOH. It was shown that LNR grafted onto the carbon black surface with ester bonds. 相似文献
12.
We propose a unified thermodynamic model of flow-induced crystallization of polymer (uFIC),which incorporates not only the conformational entropy reduction but also the contributions of flow-induced chain orientation,the interaction of ordered segments,and the free energy of crystal nucleus and crystal morphology.Specifically,it clarifies the determining parameters of the critical crystal nucleus size,and is able to account for the acceleration of nucleation,the emergence of precursor,different crystal morphologies and structures induced by flow.Based on the nucleation barrier under flow,we analyze at which condition precursor may occur and how flow affects the competition among different crystal forms such as orthorhombic and hexagonal phases of polyethylene.According to the uFIC model,the different crystal morphologies and structures in the flow-temperature space have been clarified,which give a good agreement with experiments of FIC. 相似文献
13.
The present study investigated the effects of two types of natural rubber and different blend ratios on the cure, tensile properties and morphology of natural rubber/recycled chloroprene rubber blends. The blends of natural rubber/recycled chloroprene rubber were prepared by using laboratory two-roll mill. The result showed that the cure time prolonged with the addition of recycled chloroprene rubber (rCR). Comparability, natural rubber/recycled chloroprene rubber (SMR L/rCR) blendcured rapidly than epoxidized natural rubber/recycled chloroprene rubber (ENR 50/rCR) blend. The addition of rCRalso caused a decrement in the tensile strength and elongation at break for both rubber blends. The SMR L/rCR blendsshowed higher tensile strength and elongation at break compared to those of ENR 50/rCR blends at any blend ratios. 相似文献
14.
15.
Abstract North Vietnamese NR latexes were successfully epoxidized using peracetic acid at moderate temperature and pH range. The epoxide contents of pure epoxidized natural rubber (ENR) are from 5 to 70 mol%. The ENR products were characterized and determined by spectral and thermal analysis besides the chemical titration. Conditions of longlasting or excessive temperature, or high acidic pH led to side ring opened products, proved easily by IR, 1H-NMR, and DSC analysis. The ENR were vulcanized using a semiefficient system. The epoxidation increased the adhesion between rubber and tire cord and metal. This effect becomes stronger beyond 25 mol% and tends to be limited at over 60 mol%. The ENRs were used to formulate special-purpose adhesives. The shear strength of the adhesive ranges from 32 to 45 kg/cm2 for bonding rubber to nylon and rubber to metal, respectively. 相似文献
16.
Epoxidized natural rubbers (ENRs) with different extents of epoxidation (B) were prepared under various reaction conditions. The effects of the amount of H2O2 and the reaction time on B are discussed. The glass transition temperature Tg, the thermal degradation temperature and the activation energy of thermal degradation of the ENRs increase with B. The results indicate that the thermal stability of the ENRs increases with B.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
17.
Siripon Anantawaraskul João B.P. Soares Preechathorn Jirachaithorn 《Macromolecular Symposia》2007,257(1):94-102
Summary : A series of ethylene homopolymers and ethylene/1-hexene copolymers with different molecular weight distributions (MWD) and chemical composition distributions (CCD) was analyzed by crystallization analysis fractionation (Crystaf) at several cooling rates to investigate the effect of MWD, CCD, and cooling rate on their Crystaf profiles. Using these results, we developed a mathematical model for Crystaf that considers crystallization kinetic effects ignored in all previous Crystaf models and can fit our experimental profiles very well. 相似文献
18.
Jareerat Samran Pranee Phinyocheep Philippe Daniel Daniel Derouet Jean-Yves Buzare 《Macromolecular Symposia》2004,216(1):131-144
The diimide hydrogenation of natural rubber (NR) was studied by using p-toluenesulfonylhydrazide (TSH) as a diimide-releasing agent. The microstructure and the percentage of hydrogenation were studied by Raman, 1H-NMR and 13C-NMR spectroscopic techniques. Quantitative measurements on fraction of hydrogenated part gave the results in good agreement by using these techniques. The results indicated that percent hydrogenation increased with increasing of reaction time and about 80-85 % hydrogenation was achieved when a two-fold excess of TSH was used. The vibrational characteristic of C=C bond of NR is strongly Raman active and noted at 1663 cm−1. The decrease of this signal was clearly observed during the progress of hydrogenation but the vibrational frequency of the cis and trans structures of the trisubstituted olefin unit of NR can not be differentiated by this technique. While 1H- and 13C-NMR analysis showed that cis-trans isomerization of carbon-carbon unsaturation of NR occurred during hydrogenation. 相似文献
19.
Some synergistic effects of antioxidants in natural rubber were investigated considering results obtained by differencial
scanning calorimetry (DSC). Rubber formulations were obtained with mixtures of diaminic(DPPD, IPPD, HPPD) and monoaminic (ADPA,
PBN) stabilizers and evaluated. The samples containing the mixture diamine/ADPA stabilizers showed synergistic effects while,
for those containing diamine/PBN, no effect was observed. Additionally, the diffusion constants determined by use of vulcanized
rubber disks confirmed the molar mass dependence of the stabilizer.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
Dao Pham Kim Gaidadin A. N. Gorkovenko D. A. Navrotskiy V. A. 《Russian Journal of Applied Chemistry》2018,91(2):320-324
Russian Journal of Applied Chemistry - Coagulation of natural rubber and polyvinyl chloride latices with poly(diallyldimethylammonium chloride) was studied. The influence exerted on coagulation of... 相似文献