957 resultados para LATEX BLENDS


Relevância:

10.00% 10.00%

Publicador:

Resumo:

采用反应挤出的方法,通过使用Friedel-Crofts反应,以AICl3为催化剂对原位增容线性低密度聚乙烯(LLDPE)和聚苯乙烯(PS)共混体系的反应机理、接枝物结构、材料的结构一性能关系、共混物的相分布形态以及多重结晶行为进行了深入研究。使用激光拉曼光谱研究了以AICl3作为LLDPE/PS共混体系的Friedel-Crafts反应的催化剂生成的接枝物的结构,通过对一系列模型化合物结构的分析,确定了发生接枝反应的点应为聚苯乙烯苯环上次甲基的对位。对于增容后共混物的力学性能进行了分析,并找出有效提高力学性能的工艺。根据测定,增容后的LLDPE/PS(80/20)共混物的Izod冲击性能从80J/m提高到了400)/m以上。断裂伸长率从350%提高到了800%以上。相对应的共混物的相分布形态也得到了极大的改善。这种力学性能上的提高,使得LLDPE/PS共混物真正具有了使用价值及商业前景。这也是研究LLDPE/PS共混物主要目的之一。随着含量AICl3的增加,共混物中PS分散相粒子的尺寸逐渐减小,直至共混物的相分布形态由原来的分散相一连续相结构变为双连续结构。这种形态上的改变,正是力学性能提高的基础。添加过量的AlCl3会对共混物产生一定的降解作用。通过GPC和MER等手段的分析,发现这种降解作用对于共混物中的 PS组分更加明显,而且这种降解只发生在接枝反应之后,与接枝反应是一对竞争的反应。研究了增容后的LLDP/PS(20/80)共混物的熔融结晶行为,发现了这个共混物具有复杂的多重结晶行为。通过对共混物界面层的SEM和TEM观察分析发现:在共混物的LLDPE和PS两相的中间,具有一层由LLDPE-g-PS接枝共聚物形成的界面层。这个界面层中的LLDPE链段与LLDPE均聚物在熔体中紧密的缠结着。当共混体系从较高的熔融温度逐渐下降的时候,接枝共聚物会因为链段之间的相互作用而在熔体下就形成相分离。在接枝共聚物的有序化过程中,与之紧密缠结的LLDPE均聚物分子也会随着有序化的过程而进入相分离所形成的微域结构中。研究了共棍物的这种多重结晶行为。根据共聚物的特性,首次采用了对共混物进行熔点温度之上的高温退火来研究有序一无序转变对共混物多重结晶行为的影响。由于在两相界面层的LLDPE-g-PS接枝共聚物有序化所形成的大量的微域结构限制了处于其中的LLDPE分子的结晶,导致这部分LLDPE分子结晶所需的过冷程度增加,最终只能采用均相成核的方式结晶所致。研究发现,在不同的熔融温度、退火温度以及退火时间都会对共混物的这种受限结晶行为产生很大的影响。在低于接枝共聚物的有序一无序转化温度下退火时,受限于接枝物形成的微域结构中的LLDPE均聚物分子会在这个过程中从微域结构中脱离,重新进入更大的LLDPE分散相粒子中。如果退火的温度高于接枝共聚物的有序一无序转化温度,那么这些LLDPE均聚物分子仍然会在降温的时候被“吞入”有序化所形成的微域结构中而无法脱离这种受限环境。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

聚芳醚酮是一种高性能热塑性材料,但其熔融温度高,熔体粘度大,流动性较差。液晶聚芳醚酮则具有非常丰富的液晶相织构和复杂的相转变行为,并且其熔体粘度低,流动性较好。将二者共混,液晶的加入势必降低聚芳醚酮的熔融粘度,改善其熔体流动性,另一方面液晶聚芳醚酮的液晶织构和相行为等势必受很大影响。因此开展这一研究工作不但有重要的理论意义,同时对改善这类材料的性能和拓宽其应用范围具有重要的实际意义。发现液晶聚芳醚酮/聚醚醚酮共混物的复杂相行为与组成密切相关。在以液晶聚芳醚酮为主的共混物中,高分子量的聚醚醚酮易于从低分子量的液晶聚芳醚酮基质相中分离出来,形成了特殊的环带结构。在50:50液晶聚芳醚酮/聚醚醚酮共混物中,两个组分在熔融状态下发生了液一液相分离,导致环带结构和聚醚醚酮球晶同时形成。在以聚醚醚酮为基质相的共混物中,低分子量的液晶聚芳醚酮很难从高分子量的聚醚醚酮基质相中分离出来,最后只能在聚醚醚酮球晶的边界形成单独的相区。当聚醚醚酮含量很高时,仅生成聚醚醚酮球晶。首次在液晶聚芳醚酮与聚醚醚酮共混物中发现了环带球晶,并利用溶剂选择性蚀刻的方法确定了其相结构和组成。环带球晶中的亮心和亮环是液晶聚芳醚酮相,其c轴(分子链方向)垂直于膜平面,而。和b轴则在膜平面内没有固定的取向。暗环则是聚醚醚酮与部分液晶聚芳醚酮的共存相,其中液晶聚芳醚酮晶体的分子链也垂直于膜平面,但聚醚醚酮片晶则呈现复杂的结晶取向。确定环带球晶的形成机理,从分子水平上提出环带球晶的生长模型,即间歇式增长过程,符合结构不连续模型。总结了环带球晶的形成规律和必要条件为:(l)液晶聚芳醚酮为主要成分;(2)液晶聚芳醚酮与聚醚醚酮有一定相容性,至少在熔融态分子相容;(3)液晶聚芳醚酮的各向同性相向液晶相的转变温度要高于聚芳醚酮的结晶温度;(4)液晶聚芳醚酮相转变(或结晶)速率与共混物的相分离速率相匹配或前者略大于后者;(5)降温速率或等温结晶温度适当。聚醚醚酮/含氟液晶聚芳醚酮共混物在熔体状态下的流动行为与共混物的组成、两相的相容性及相的转变有着密切的关系。在聚醚醚酮/含氟液晶聚芳醚酮共混物中,当前者为主要成份时,流动曲线形状与纯PEEK的相似,而当后者为主要成份时,表现出与含氟液晶聚芳醚酮相似的流变行为。共混物的复数粘度、储存模量和损失模量总体来说随F一队EK含量的增加而逐渐下降,只有当含氟液晶聚芳醚酮含量为50%时,共混物的复数粘度、储存模量和损失模量出现了局部极大值。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

目前,可降解塑料作为一种解决塑料废弃物污染环境的最有效的全新技术途径,是各国塑料领域研究的热门课题之一。降解塑料大体可分为光降解、生物降解、光/生物降解和水降解塑料,其中光/生物双降解塑料的发展最快,形成产业化的商品也比较多。本论文选用通用塑料中应用最广泛的聚乙烯和天然可降解高分子材料中最具有代表性的淀粉作为共混体系,应用硬脂酸铁作为光敏化剂,系统的研究了共混体系的光降解特性和生物降解性能,同时还对淀粉的改性加工进行了研究。1、天然淀粉不具有热加工性能,采用甘油为淀粉的增塑剂,经过适当的工艺处理,可使其转化为具有加工性能的热塑性淀粉。并通过差热分析、流变学研究,讨论了热塑性淀粉的稳定性和加工性能。2、采用硬脂酸铁作为聚乙烯/淀粉共混物的光敏化剂,随着光敏化剂用量和光照时间的增加,聚乙烯和聚乙烯/淀粉共混物的力学性能呈明显下降趋势,分子量降低,碳基指数上升。说明硬脂酸铁对聚乙烯及其与淀粉的共混物具有很好的光敏化效果,在降解过程中伴有交联反应发生。同时,淀粉的加入对聚乙烯光氧化降解的发生具有促进作用。3、聚乙烯/淀粉共混物在堆肥一段时间后,表面出现大量的空洞,淀粉含量越高空洞越多,当淀粉含量)30%时,聚乙烯的分子量开始下降,说明共混物具有明显的生物降解特性。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本工作对不同分子构成的丁苯嵌段共聚物SBS(SB三嵌段共聚物)和SB-4A(SB四臂星型嵌段共聚物)分别与均聚物PPO,以及分别与不同分子量的均聚物PBD的共混体系进行了研究,探讨了嵌段共聚物分子构造,均聚物分子量和共混组成对共混体系的相容性和形态结构的影响。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文选取比较常见的PP/EVA、PE/EVA共混体系作为增强交联研究的对象,研究了共混体系的增强交联规律,并针对目前普通使用的多官能团单体存在着与聚合物体系相容性差、易析出、高温挥发大的弱点,设计合成几种多官能团单体。此外,还研究了共混体系增强界面反应,讨论了增强界面反应的一般原理和增强界面反应对改善不相容共混体系相间粘附的作用影响。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文概括地介绍了高分子液晶的发展史的分类、合成方法、性能、高分子液晶的结构与性能的关系、二羟基二苯酮型液晶共聚酯、液晶聚酰亚胺、固相后聚合、高分子液晶共混物、以及高分子液晶及其原位复合材料的应用。以4,4'-二羟基二苯酮为单体之一,利用直接熔融缩聚和界面缩聚等方法合成了一系列的热致液晶共聚酯和聚酯酰亚胺。采用示差扫描热分析法,广角X-射线衍射法,偏光显微镜,红外光谱,电子显微镜,流变仪,力学性能测试仪等对聚合物进行表征。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Controlled vertical drying deposition method was used to make high-quality single crystal close-packed colloidal films formed of different radii polystyrene latex spheres on glass substrates coming from a low concentration water suspension (0.1% volume fraction). Regardless of the spheres radii the film thickness was about 6.3 microns. However, cracks destroyed the crystalline film structure during the colloidal film growth. The effect of particle radius (85-215 nm range) on film cracking was systematically studied using in situ optical fracture monitoring. Primary parallel cracks run along the vertical growth direction, later followed by secondary branched cracks in-between the primary cracks due to residual water evaporation. Quantitative theoretical relationship between the cracks spacing and particles radius was derived and shows good agreement with experimental observations. Normalized cracks spacing is related to a reciprocal ratio of the dimensionless particle radius.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

一体化反应器由于投资少、占地小、管理运行方便等优点而备受青睐。但现有的一体化反应器大都适用于处理中低浓度废水,耐受负荷普遍偏低。本课题研制出新型高效的厌氧好氧一体化生物反应器,旨在通过反应器结构优化、高效微生物载体研制、配合高效微生物菌剂技术处理中高浓度有机废水,实现高效和低耗,降低设备造价,提高反应器运行稳定性。 首先开展了菌剂对废水的适配试验。采用15种不同的微生物菌剂,以葡萄糖配水、中药提取废水、啤酒废水、氨氮配水为基质,分别测定了微生物菌剂的耗氧速率和厌氧比产甲烷速率,以其为指标比较了各菌剂对废水的适配性。根据结果选择活性高的14#、8#、10#菌剂,在试验室进行了菌剂对废水的连续处理试验,取得良好的处理效果,为菌剂在厌氧好氧一体化生物反应器的小试、中试中的应用奠定了基础。 经小试研究后,又对厌氧好氧一体化生物反应器进行了处理发酵废水的中试研究。试验结果表明,反应器启动快,系统有机负荷2.72 kgCODm-3d-1时整个反应器去除率保持在84.5%~93.19%,在30多天内一次启动成功。冲击负荷试验中,系统总有机负荷最高可达到8.88 kgCODm-3d-1,系统去除率稳定在88.10%~96.88%,说明反应器处理效率高,抗冲击能力强。稳定运行期间,COD去除率可达90%以上,各项指标都能达到国家排放标准。 此外,对反应器配套系统高效菌剂、高分子复合颗粒载体进行了研究。结果显示,菌剂与反应器适配良好,各功能区形成了丰富、高活性的微生物,厌氧区颗粒污泥TS高达83.9 gL-1,VS/TS为56.9%~57.4%,比产甲烷活性为280~350 mLCH4 gvss-1d-1;好氧区固定化微生物TS高达1.921 gL-1,VS/TS为94.02~94.30%。对载体性能的研究表明,此高分子复合颗粒载体密度适中,易于流化,不易流失;粗糙多空,易于挂膜;且无生物毒害作用,稳定安全,是一种优良的生物载体。反应器各功能区对废水的降解过程分析,说明了反应器、菌剂、载体适配良好,在其协同作用下,实现了污染物的高效降解。 The integrated reactors were popular because of their characteristics such as little investment, small occupation of land, convenient of manage and running etc. But the present integrated reactors were mostly applied for treating wastewater of low concentration, the load tolerance was generally on the low side. A new type integrated anaerobic-aerobic bio-reactor was developed, which was conducted to treating organic wastewater of middle or high concentration by optimization of reactor structure, development of efficient microbe carrier and adaptation of high active microbial blends, to achieve high efficiency and low consume, reduce equipment cost, enhance running stabilization of reactor. The adaptability test of microbial blends on different wastewater was carried on firstly. Oxygen consumption rate and anaerobic specific activity of methane producing of 15 different microbial blends were measured separately taking glucose artificial wastewater, Chinese herb extracting wastewater, brewery wastewater and ammonia nitrogen artificial wastewater as substrate, by which the adaptabilities of different microbial blends to wastewater were compared. According to the results high active microbial blends 14#, 8# and 10# were selected and used in the continuous treatment of wastewater in the laboratory and had obtained good effect, which had laid a foundation for application microbial blends to small scale test and pilot test of integrated anaerobic-aerobic bio-reactor. After the small scale test, the pilot test of the integrated anaerobic-aerobic bio-reactor treating fermentation wastewater was carried on. The test results showed fast initiation of the reactor. When system organic load reached 2.72 kgCODm-3d-1the COD removal rate of the reactor was stable between 84.5%~93.19% and it initiated successfully in more than 30 days at a time. In the load shock test the maximum organic load of system could reach to 8.88 kgCODm-3d-1 and the COD removal rate could be stable between 88.10%~96.88% which indicated that the reactor was efficient for treating wastewater and had strong resistance to shock load. At stable running period the COD removal rate of the reactor was over 90% and each index of wastewater could reach to the national discharge standards. In addition, the high active microbial blends and the macromolecule compound granule carrier, the matching system of the reactor was studied. It showed that the microbial blends adapted well to the reactor and abundant and high active microbes were formed in each functional field. The TS of granule sludge in anaerobic field was as high as 83.9 gL-1, the VS/TS was 56.9%~57.4%, the specific activity of methane producing was 280~350 mLCH4 gvss-1d-1. And the TS of immobilized biological granule was as high as 1.921 gL-1, the VS/TS was 94.02%~94.30%. Study on the carrier showed that the self-made macromolecular compound granule carrier was moderate of density, easy of fluidization, unease of running off, rough and porous, easy of films fixation, no bio-toxic, stable and safe, was a kind of superior carrier. Analysis of degradation process in each functional field confirmed the reactor, microbial blends and carriers were in good adaptation and wastewater was decontaminated by their cooperation.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This review surveys the recent progress in the adsorbed stationary phases for capillary electrochromatography (CEC). Adsorption-based methods for preparation of stationary phase are novel approaches in CEC, which allow rapid and facile preparing stationary phases with desirable selectivity onto an open-tubular fused-silica capillary, a baresilica or ion-exchange packed column or a monolithic silica or polymer column. A variety of adsorbing agents have been developed as adsorbed stationary phases, including ionic long-chain surfactant, protein, peptide, amino acid, charged cyclodextrin (CD), basic compound, aliphatic ionene, and ion-exchange latex particle. The adsorbed stationary phases have been applied to separation of neutral, basic and acidic organic compounds, inorganic anions and enantiomers. They have also been applied to on-line sample concentration, fast separation and study of the competitive binding of enantiomers with protein.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The domain-structure of samples containing a series of starch/poly(sodium acrylate)-grafted superabsorbents, pure starch, pure poly(sodium acrylate), and blend of starch/poly(sodium acrylate) has been studied by high-resolution solid-state C-13 NMR spectroscopy at room temperature. The result shows that the crystallinity of starch decreases greatly in the grafted and blended samples.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Thermal properties and crystallization-behavior of ultrafine fully-vulcanized powdered rubber (UFPR) toughened poly propylene (PP) were studied by Differential scanning calorimetry (DSC) and Wide angle X-ray diffraction (WAXD) measurements. It was found that the fraction of beta-form in the PP crystal increased at first, then sharply deceased up to zero with increasing UFPR content

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The novel phase field model with the "polymer characteristic" was established based on a nonconserved spatiotemporal Ginzburg-Landau equation (TDGL model A). Especially, we relate the diffusion equation with the crystal growth faces of polymer single crystals. Namely, the diffusion equations are discretized according to the diffusion coefficient of every lattice site in various crystal growth faces and the shape of lattice is selected based on the real proportion of the unit cell dimensions.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A reactive type nonionic surfactant, polyether pentaerythritol mono-maleate (PPMM) was synthesized in our laboratory. PPMM was adopted as functionalizing monomer and grafted onto linear low density polyethylene (LLDPE) with a melt reactive extrusion procedure. FT-IR was used to characterize the formation of grafting copolymer and evaluate their degree of grafting. The effects of monomer concentration, reaction temperature and screw run speed on the degree of grafting were studied systematically. Isothermal crystallization kinetics of LLDPE and LLDPE-g-PPMM samples was carried out using DSC.