丁腈橡胶阻尼材料的研究及其影响因素

丁腈橡胶是一种具有强极性的高分子弹性体,不仅具有良好的耐油性和粘接性,较其他橡胶还具有更宽的使用温度,在汽车、航空、石油、复印等行业中成为必不可少的阻尼减振材料.为了改善单一橡胶力学性能较差、有效阻尼温域较窄等弊端,使橡胶阻尼材料在实际中得到更好的应用,大量的学者对丁腈橡胶进行了不同方法的改性.本文主要综述了近年来国内...     

辐射技术在聚乙烯改性的研究进展

聚乙烯(PE)是用途非常广泛的通用塑料,具有优良的韧性、耐化学性和良好的加工性能,但耐热性能差,非极性和极低表面能等缺点限制了它的使用。辐射技术可以有效地改善聚乙烯的耐热性、提高聚乙烯的极性,拓展其应用领域。从辐射交联、辐射接枝和辐射增容三个方面综述了辐射技术在聚乙烯改性加工的应用研究进展。今后不断加强无污染、无公害的辐射技术在聚乙烯加工改性的开发和应用。     

SBS和SBS环氧化与顺酐化研究

SBS是(苯乙烯-丁二烯-苯乙烯)三嵌段共聚物，是含有聚苯乙烯玻璃化微区及聚丁二烯连续相的多相聚合物，具有热塑性橡胶的性质。它具有良好的拉伸性能、耐湿性、透气性、溶解性及抗滑性，而被大量用于橡胶制品、粘舍剂及沥青和树脂的改性剂等。其缺点是耐油性差，与极性物质不相容，不粘接等。用环氧化及顺酐化改性可改进这方面的缺点。SBS的环氧化改性多半使用过甲酸或过乙酸在溶液中进行。产物可作为压敏胶、热熔胶、密封胶等，用于粘接极性材料，也可作为耐油热塑性橡胶。SBS的顺酐化改性可在熔融态进行，也可在溶液中进行。产物可用作极性聚合物与非极性聚合物的共混增容剂、胶粘剂及进一步合成离聚体。     

EAA基热致型热塑性形状记忆高分子弹性体的制备与性能研究

采用乙烯-丙烯酸共聚物(EAA)热塑性弹性体制备了热致型形状记忆高分子材料,并对其力学性能、微观取向结构、结晶行为和不同变形模式下的形状记忆效应进行了研究,还对变形温度与回复温度对其形状记忆效应的影响进行了探讨。结果表明,EAA样品拉伸表面存在明显取向结构,为其形状回复提供了驱动力;根据EAA样品的熔融、结晶和粘弹行为可确定其形状记忆变形温度和回复温度范围;在拉伸、旋转和卷曲模式下,EAA样品均表现出良好形状记忆效应;当变形温度接近EAA熔点且为95℃时,EAA样品同时具备优异的形状固定率(98.7%)和良好的形状回复率(91.5%);升高回复温度可提高EAA样品形状回复速率。     

聚双环戊二烯耐腐蚀性能研究

为了拓展聚双环戊二烯(PDCPD)材料的应用潜力,利用溶剂浸泡法研究PDCPD材料的耐腐蚀性能。结果表明：PDCPD材料能够耐受大多数极性有机溶剂、酸碱溶液的腐蚀,但在部分强氧化性的浓酸中,PDCPD分子结构的不饱和CC双键易被氧化,导致材料被腐蚀;由于相似相溶原理,在部分非极性和弱极性有机溶剂中,PDCPD材料会发生溶胀腐蚀,造成材料性能下降。     

EAA/C9树脂/天然橡胶阻尼材料的制备及性能研究

以乙烯丙烯酸共聚物(EAA)、C9树脂、天然橡胶(NR)为主要原料制备阻尼材料,并应用于高阻尼橡胶隔震支座中,考察了EAA/NR质量比、C9树脂用量对阻尼材料的剪切模量、等效阻尼比和老化性能的影响。结果表明,EAA/NR质量比为15/85、C9树脂用量为20份,所制备的阻尼材料具有良好的阻尼性能和耐老化性能,制备的高阻尼橡胶隔震支座竖向刚度、水平刚度、等效阻尼比与设计值偏差分别为13.7%、9.9%和-1.3%,经过80℃×1 296 h老化后,竖向刚度、水平刚度、等效阻尼比变化率分别为12.2%、9.8%和-6.8%,支座性能满足寿命设计要求。     

聚氨酯改性环氧胶粘剂的研究

聚氨酯预聚体通过催化剂与环氧树脂接枝反应合成了蒙氨酯改性环氧树脂。该树脂在改性胺和催化剂作用下，具有良好的施工性能和较高的强度，对极性基材和非极性PE材料具有良好的粘接性能。     

端异丙黄原酰硫基液体聚氯丁二烯的性能及应用研究

端异丙黄原酰硫基液体氯丁橡胶具有良好的耐介质性能及耐烯性,可作为化工设备的衬里材料、极性固体橡胶的耐抽提性增塑剂及耐燃涂料使用。对三元乙丙橡胶具有一定的增粘作用,可作为固体橡胶的改性剂。     

r-PET/POE/EAA共混材料性能的研究

以回收聚对苯二甲酸乙二醇(酯r-PET)为基体材料,乙烯-辛烯共聚(物POE)为增韧材料,乙烯-丙烯酸共聚物(EAA)为相容剂,制备了r-PET/POE/EAA共混材料。用DSC、SEM分析了POE及EAA对r-PET结晶性能、断面结构的影响,并测试了共混材料的力学性能。结果表明:加入12%POE后,r-PET/POE共混材料的熔融温度降低了1.76℃,结晶度降低了16.49%,断裂伸长率及缺口冲击强度明显提高,弯曲强度和拉伸强度略有下降;在r-PET/POE共混材料中加入1.5%EAA后,POE球状粒子嵌入r-PET基体中,二者相容性提高,结晶速率加快;与纯r-PET相比,r-PET/POE/EAA共混材料的断裂伸长率和缺口冲击强度分别提高了698.01%和227.45%柔,韧性也大幅度提高。     

烷基酚醛增粘树脂改性方法及增粘机理分析

介绍烷基酚醛增粘树脂的合成工艺、改性方法和作用机理。烷基酚醛增粘树脂由于酚环上有一定支化度且柔顺性好的取代烷烃基团,与橡胶分子具有良好的相容性,酚羟基具有一定的极性,彼此之间能形成氢键,混炼过程中在胶料界面上形成互穿氢键网络结构,使粘合材料达到均一充分的融合。通过改性可进一步提高烷基酚醛增粘树脂的极性,从而提高其增粘效果。     

Surface modification of ethylene copolymers molded against different mold surfaces. Part 2. Changes at the outermost surface

The influence of the mold surface on the surface composition of thermoplastics has been investigated. Two different random copolymers, poly(ethylene-co-acrylic acid) (EAA) and poly(ethylene-co-vinyl acetate) (EVA), with varying comonomer contents were used. Specimens were prepared in molds coated with films of perfluorinated ethylene-propylene copolymer (FEP) and of poly(ethylene terephthalate) (PET). Samples were also molded against air and vacuum. Changes in the concentration and arrangement of the functional groups at the outermost surface were studied using X-ray photoelectron spectroscopy (XPS or ESCA), Fourier transform infra-red techniques (FTIR), and contact angle measurements. The concentration of functional groups at the outermost copolymer surface depended on the nature of the surface against which the random copolymers were molded. Results are interpreted in terms of differences in surface energy between the mold surface and the copolymer. The polar acrylic acid groups in EAA increased when molded against the polar PET mold surface and decreased when molded against nonpolar mold surfaces. Air exposure affected the EAA copolymer surface so that the nonpolar parts migrated to the outermost polymer surface, which resulted in a decreased content of acrylic acid groups. Acetate groups in EVA were found to be in excess at the surface when molded against both polar PET and nonpolar FEP. The signal of O 1s in the XPS spectra depended on the mold surface and the time in the XPS vacuum environment. This can be explained in terms of preferential arrangement of the acrylic acid and the vinyl acetate groups.     

乙烯丙烯酸共聚物型不可逆示温材料的研究

以乙烯丙烯酸共聚物为原料,以低毒性溶剂正庚烷为溶剂,在低温下通过加热和搅拌,制备了环保型低温不可逆示温材料。通过X射线衍射仪测试和分析不可逆示温材料的粒径及结晶规整度。采用差示扫描量热法测定不可逆示温材料的结晶性能和熔点熔限。通过单因素法讨论制备工艺对不可逆示温材料性能的影响。最终确定实验的最佳组成。结果表明,EAA580起始变色温度为82 ℃,变色温度区间为3 ℃,而EAA540起始变色温度为86 ℃,变色温度区间为10 ℃;由EAA580制备的示温贴片具有起始变色温度低、变色温度窄、灵敏度高的特点。     

C5石油树脂改性及其在路标漆中的应用

C5石油树脂是以裂解乙烯副产品的C5馏分为原料,经阳离子催化聚合得到的功能树脂。它的分子结构上缺少极性基团,这使其与一些极性树脂如EVA,EAA等份难以充分互容,从而限制了它的有效利用。实验根据接枝反应原理,采用马来酸酐为改性剂对C5石油树脂进行化学改性。提高其软化点。实验考察了马来酸酐用量、引发剂用量、反应温度和反应时间四个因素对产品软化点的影响。实验结果表明：马来酸酐用量为0．5％（质量分数）,引发剂用量为1％,反应温度为200℃,反应时间为2．5h时,为最佳改性条件。根据最佳反应条件制备出的路标漆性能优良。     

用接触角法测量聚合物共混体系的表面性能

利用接触角的方法研究了聚合物HDPF、PET及其共混物HDPE／PET的表面自由能、极化度以及与不同液体一水和甘油间界面张力的大小。     

Some practical aspects of thin-layer chromatography of lipids

This report describes methods for the thin-layer chromatography (TLC) of lipids and some practical aspects of the methods. In order to present some basis for choosing the correct powder for particular separations, some properties of several widely used silica gel powders are compared. The effect of binder material such as calcium sulfate in silica gel is studied. The three systems, silica gel as a polar phase, silver nitrate-impregnated silica gel, and reversed phase systems are described with application to neutral lipids. Also included are the applications of TLC to the polar lipids, such as phospholipids, cerebrosides, sulfatides, sphingomyelin and other glycolipids from various sources. The pitfalls and precautions involved in these separations are discussed in detail.     

Studies on Blends of Acetate and Acrylic Functional Polymers with Bitumen

Blends with a 100 penetration grade bitumen from Venezuela have been made with five commercial polar polymers in up to 40 parts per hundred (29%) proportions, and examined by fluorescence optical microscopy, differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA), to reveal developments in the performance of the colloid, a readily‐made nanocomposite. The low temperature stiffness of the bitumen was enhanced by two orders of magnitude whatever polymer or its quantity used, but the ionomer additive was more effective than this when its proportion was low, indicating a specific organisation of the asphaltenes. All the polymers dispersed in and lowered the glass transition of the bitumen‐rich phase, and all raised the modulus at high temperatures, some copolymers of ethylene doing this by creating within the polymer‐rich phase – when this was extensive – a network which failed only when the crystallite crosslinks melted. Blends of the EVA with 28% ester groups almost lacked such crystallinity but had a second tanδ process and enhanced high temperature stiffness, perhaps caused by the polar groups bonding to the asphaltenes, the highly anisotropic nanoparticulates. Phase inversion – the development of an extensive polymer‐rich phase – was demonstrated by the two EVA systems and the EAA polymer in the fluorescence photomicrographs, and by the resolution of a clear peak at the glass transition in the tan δ plot, but the DMTA plots of the blends of PMMA and the ionomer lacked such features. The PMMA was present mainly as a dispersed phase, for its T_g was hardly depressed by any component of the bitumen, but the latter, according to the fluorescence photomicrographs, did have an extensive polymer‐rich phase. Activation energies from the E″ measurements were about 150 to 200 kJ·mol^–1 for the glass transition, in keeping with the absence of extensive crystalline regions. Several polymers caused the T_g of the material to fall by up to 24°C when in small proportions (the EAA being most effective), but to rise upon further additions. The 9% EVA and the ionomer were the least effective plasticisers. Polymers with a cohesive energy density of more than 17 (J/cm³)^0.5 caused blends to adhere to glass, whatever their proportion.     

Novel ionomers based on blends of ethylene-acrylic acid copolymers with poly(vinyl amine)

The polymerization of N-vinyl formamide followed by hydrolysis yields a linear, water-soluble poly(vinyl amine). The high concentration of pendant primary amine groups leads to a polymer with an interesting set of properties. Complexation with water-soluble anionic polyelectrolytes in water solutions leads to a highly water-insoluble material. The study described herein investigated the phase behavior/properties of melt blends of poly(vinyl amine) with ethylene-acrylic acid (EAA) copolymers of less than 10 wt % acrylic acid. The calorimetric and dynamic mechanical analyses of the resultant blends show that the vinyl amine groups are accessible to the acrylic acid groups of the copolymers and the major property changes occur up to the stoichiometric addition of vinyl amine/acrylic acid. At higher levels of vinyl amine (vinyl amine/acrylic acid mol ratio > 4), additional poly(vinyl amine) forms a separate phase. The mechanical, dynamic mechanical, and calorimetric properties of these blends below the stoichiometric ratio show analogous trends as with typical alkali/alkaline metal neutralization. These characteristics relative to the base EAA include improved transparency, lower melting and crystallization temperature, lower level of crystallinity, and increased modulus and strength. The emergence of the β transition in dynamic mechanical testing is pronounced with these blends (as with alkali/alkaline metal neutralization), indicative of microphase separation of the amorphous phase into ionic-rich and ionic-depleted regions. A rubbery modulus plateau for the blends exists above the polyethylene melting point, demonstrating ionic crosslinking. Above 150°C exposure, further modulus increases occur presumably due to amide formation. This study demonstrates that the highly polar poly(vinyl amine) can interact with acrylic acid units in an EAA copolymer comprised predominately of polyethylene (>90 wt %). The thermodynamic driving force favoring ionic association overrides the highly unfavorable difference in composition. © 1996 John Wiley & Sons, Inc.     

Complexes of starch polysaccharides and poly(ethylene co-acrylic acid): Structure and stability in solution

Chiroptical methods have been used to study the conformation and interactions of amylose and amylopectin with poly(ethylene co-acrylic acid) (EAA) in aqueous solution. These studies, along with X-ray diffraction and solid-state NMR data, show that amylose and EAA, as well as amylopectin and EAA, form helical V-type inclusion complexes when mixed in aqueous suspension. This structure apparently accounts for the partial compatibility observed in films containing starch and EAA. About 2/3 by weight of EAA does not interact with amylose and probably represents the ethylene-rich central core of the EAA micelle. EAA/amylose complexes in 10 mM NaOH were stable to temperatures > 90°C, whereas EAA/amylopectin complexes in the same solvent were largely disrupted at this temperature. Urea, at a concentration of 8 M, further destabilized both EAA/amylopectin and EAA/amylose complexes. Solutions with an alkaline pH (> 9.5) dispersed EAA optimally and allowed maximum complexing with amylose. At pH values > 13, the EAA/amylose complexes were weaker, most likely due to electrostatic repulsion between ionized hydroxyl groups of amylose and carboxyl groups of EAA.     

Cyclic FA monomers in high-oleic acid sunflower oil and extra virgin olive oil used in repeated frying of fresh potatoes

The measurement of FA profile, polar material, oligomers, oxidized triacylglycerols (OTG), total polyphenols, and cyclic FA monomers (CFAM) was used to evaluate the alteration of a high-oleic sunflower oil (HOSO) and an extra virgin olive oil (EVOO) used in 75 domestic fryings of fresh potatoes with frequent replenishment (FR) of unused oil. CFAM were absent in the unused EVOO but appeared in small amounts in the unused HOSO. Although polar material, oligomers, OTG, and CTAM contents increased and linoleic acid and polyphenols content decreased in both oils during repeated frying, the changes produced should be considered small and related to the use of very stable oils and FR. Throughout the 75 fryings, the total CFAM concentration was higher in HOSO than in EVOO. OTG increased more quickly in EVOO, whereas oligomers increased more quickly in HOSO. Polar material and oligomer content appear significantly correlated (r=0.9678 and r=0.9739, respectively; for both, P<0.001) with the CFAM content. A 25% polar material and 12% oligomer content would correspond to about 1 mg·kg⁻¹ oil of CFAM. Data suggest that both oils, particularly EVOO, perform very well in frying, with a low production of oligomers, polar materials, and CFAM.