PVC/Elvaloy/NBR三元共混热塑弹性体的研究

Elvaloy是美国杜邦公司开发的一种新型PVC专用高分子增塑剂,是高分子增塑剂的一个重要突破。近年来,Elvaloy用于PVC方面的研究和应用在美国、日本和西欧已很广泛。据报道,Elvaloy与DOP并用于PVC制成的软制品,克服了低分子增塑剂所存在的迁移、渗出和挥发等缺点,使其耐久性、耐寒性、耐油性和耐候性等显著改善。在国内,这方面的工作已开始起步,但总的来看,这方面的研究应用还不广泛。关于PVC/Elvaloy/NBR三元共混方面的研究还未见报道,本文报道了笔者在这方面做的上些工作。     

活性炭对聚丙烯腈共混熔液流变性的影响

共混是合成纤维改性常用的方法．用活性炭与丙烯脯─氯乙烯共聚体共混制得纺丝溶液,以二甲基甲酰胺为溶剂湿法纺丝制造了吸附和阻燃双功能聚丙烯膊纤维．本文主要探讨了共混溶液中活性炭含量,温度等条件对纺丝溶液流变性能的影响．     

明胶基共混纺丝原液流变性能的研究

主要考察了不同温度,浓度及交联剂用量与明胶/PVA,明胶/粘胶以及明胶/粘胶/PVA共混纺丝原液的流变性能之间的关系。结果表明,明胶基共混纺丝液的黏度主要受温度,共混液浓度和各组成成分间比例影响,通过调节溶液浓度、配比以及温度可以控制共混纺丝液的流变性能。明胶基共混液的黏度随剪切应力的增加而减小,呈现＂剪切变稀＂现象,符合非牛顿流体＂剪切变稀型流体＂的黏度变化规律。     

共混可润湿聚丙烯的流变性能研究

共混可润湿聚丙烯流体的流动特征与常规聚丙烯相似 ,为典型的假塑性流动 ,其非牛顿指数随剪切速率的增大而减小 ,表观粘度和粘流活化能随共混比的增大而减小     

水溶性甲壳素／纤维素共混液的流变性研究

用高效毛细管流变仪与DV-Ⅱ旋转粘度计,研究了纺制新型抗菌纤维的水溶性甲壳素与纤维素共混溶液的流变性.研究表明:在一定温度范围内,不同配比的混合液属于非牛顿流体,表观粘度随剪切速率的增大而降低,非牛顿指数随温度的升高而增大;当w(甲壳素)为5%时,共混液在30～40 ℃内.结构粘度指数Δη变化较缓慢,温度超过40℃,Δη迅速下降.当w(甲壳素)达到10%、15%时,Δη随温度变化缓慢.     

PU/PP二元共混可染丙纶的研究

研究了PU／PP共混物的流变性、相态、密度及纤维的染色性能。结果表明PU／PP共混纤维密度低于纯PP纤维PU／PP共混纤维可以用分散性染色染色,且色牢度良好。     

胶原蛋白/聚乙烯醇共混纺丝原液的流变性能

研究了影响不同配比的胶原蛋白／聚乙烯醇共混纺丝原液流变性的因素,如原液的温度、浓度和交联剂用量对共混原液的非牛顿指数、结构黏度指数、零切黏度及粘流活化能等流变参数的影响。结果表明,各配比的胶原蛋白／聚乙烯醇共混纺丝原液均属非牛顿剪切变稀型流体,非牛顿指数n随原液温度的升高而增大,但随浓度和交联剂用量的增大而减小;结构黏度指数随温度的升高而减小,但随浓度和交联剂用量的增大而有所增大;粘流活化能随原液中胶原蛋白比例的增加而增大,说明了共混原液的零切黏度对温度的敏感程度较高,这就要求纺丝过程须注意控制好共混原液的温度。     

聚乳酸接枝马来酸酐/淀粉共混物对涂料流变性及纸张性能的影响

将聚乳酸接枝马来酸酐与淀粉共混物作为胶黏剂用于造纸涂料中,研究了改性聚乳酸不同用量对涂料流变性以及对涂布纸白度、表面强度、油墨吸收性能的影响;同时与涂料中常用的合成胶乳丁苯胶乳作比较。结果发现:改性聚乳酸用量的增加可以显著降低涂料低剪切黏度和高剪切黏度,改善涂料流变性;同时,随着改性聚乳酸用量增加,涂布纸白度、表面强度和油墨吸收性提高;另外,改性聚乳酸/淀粉共混物作为胶黏剂使用与丁苯胶乳对涂布纸性能影响相差不大,可替代丁苯胶乳或与之配合使用,获得更好的涂布纸性能。     

PBT／PA6共混物的流变性探讨

本文用Instron3211毛细管流变仪探讨了聚对苯二甲酸丁二酯(PBT)/聚酰胺-6(PA6)共混物的流变性。结果表明,PBT/PA6共混物熔体为切力变稀性流体,在组成为75%和90%(PBT的重量百分数)时分别出现粘度的极大值和极小值;共混物粘度对温度的依赖性可用Andrade方程来描述。     

RHEOLOGICAL PROPERTIES OF BLENDS OF SATURATED GLYCERIDES AND LIQUID SOYBEAN OIL

Abstract . Rheological behaviour of model blends (shortenings) prepared from liquid soybean oil, completely hardened cottonseed oil and glycerol monostearate was evaluated using the coaxial cylinders or the plate and cone system of the Rotovisko Viscometer. Initial and residual yield points, plastic (Bingham) viscosities, shapes and areas of hysteresis loops, and rates of recovery during rest and after shear were determined. There was almost linear intercorrelation between the yield points and the other rheological parameters, including the relative shear thinning. The determined rheological properties were correlated to the amount of total solid glycerides in the blend. It was shown that pumpability of shortenings could be evaluated from selected rheological properties.     

PREDICTING STEADY AND OSCILLATORY SHEAR RHEOLOGICAL PROPERTIES OF CMC/GUAR BLENDS USING THE BIRD-CARREAU CONSTITUTIVE MODEL

The Bird-Carreau constitutive model, a five parameter semi-empirical set of equations, was used to predict the steady shear viscosity η, the dynamic viscosity η', and the out-of-phase component of the complex viscosity divided by frequency η"/ω, for aqueous blends of sodium carboxymethylcellulose (CMC) and guar gum. The five Bird-Carreau constants were derived from equations which correlate the constants to concentration and molecular weight of the CMC/guar blends. Blends of ratios 3:1, 2:1, 1:1, 1:2, and 1:3 by weight were studied in concentrations of 0.5, 0.75, 1.0, and 1.5% by weight. For most blends the model accurately predicted the experimental η and η' data in the frequency/shear rate range of 0.1–100 s^-1 and the experimental η"/ω data in the frequency/shear rate range of 1.0–100 s⁻¹.     

A SINUSOIDAL COMPRESSION SYSTEM TO STUDY RHEOLOGICAL PROPERTIES OF FOODS IN THE TRANSIENT STATE

A testing device specially designed to study rheological properties of meats and their relation to tenderness is described. Samples are submitted to a sinusodal compression during 1 to 2 cycles with recovery delay of 0 to 10 s at frequencies between 0.05 and 25 Hz so that deformation rates thus attained overlapped those of chewing. The compression can be regulated between 10 and 90%, and adjusted to initial sample height from 3 to 30 mm. Sample strength is measured by a force quartz transducer connected to a high speed data acquisition and storage system, versus the deforming tool displacement whose specific law is given.     

RHEOLOGICAL PROPERTIES OF HYDROCOLLOIDS IN THE PRESENCE OF SUCROSE AND MILK

Apparent viscosities of guar gum, locust bean gum, and sodium carboxymethylcellulose were measured at shear rates of 16-2620s^-1 in water, sucrose, milk, and sucrose/milk solutions. The effect of different heat treatments was also studied. For all solutions, a power law equation described the variation of relative viscosity with shear rate allowing comparison of their non-Newtonian behaviour. With the neutral hydrocolloids, the hydration was limited by the presence of sucrose and milk which reduced the effective length of the polymer molecules. The behaviour of the polyanionic hydrocolloid, Na CMC, although influenced by milk and sucrose separately, was controlled by milk in a milk/sucrose mixture. This is due to milk salts which reduced the intramolecular repulsions along the polyanion and substantially lowered its effective hydrated length.     

RHEOLOGICAL PROPERTIES OF BEDS OF RAISINS

The rheological properties of beds of Sun-dried Sultana and Corinth raisins equilibrated to various moisture levels were investigated. Raisin beds of fixed bulk density at various configurations were compressed in a cylindrical test cell, and the apparent modulus and the two constants of an empirical model were estimated from the linearized stress/strain and relaxation curves. Beds of black Corinth raisins were more elastic than Sultana (seedless) raisins at moistures lower than 18%, but both types of raisins showed similar rheological behavior at higher moistures. The unrelaxed stress of all beds, after 10 min of relaxation, was about 25% of the initial stress. Beds of randomly mixed raisins of different moisture content appeared to be more elastic when the proportion of the moist raisins was increased. The apparent modulus of columns of raisins decreased as the number of raisins per column and the number of adjoining rows were increased.     

RHEOLOGICAL PROPERTIES OF ALGINATE GELS

Rheological properties of alginate gels formed in various ways were studied using a parallel plate viscoelastometer and an Instron. All the gels studied exhibited linear viscoelastic behaviour. The creep compliance-time response was fitted by a model consisting of a Maxwell element in series with two or three Kelvin-Voigt elements. Despite the fact that alginate gels are non-thermoreversible the crosslinks do not appear to be permanent. Gels formed with an alginate containing a high proportion of mannuronic acid residues are weaker and more elastic than gels prepared with an alginate predominantly composed of guluronic acid residues. When the level of calcium in the gel was high, the reciprocal of the creep compliance was proportional to the square of the polysaccharide concentration. A reduction in calcium level for a given polysaccharide concentration resulted in a more elastic gel. The nature of the temperature dependence varied with the degree of crosslinking and time of measurement after application of stress. The results were explained by assuming that the creep compliance could be regarded as the sum of two components: a time independent factor given by the theory of rubber elasticity, or some modification of this, and a time dependent factor associated with the breakage of crosslinks.     

RHEOLOGICAL PROPERTIES OF PECTATE GELS

Creep compliance measurements were made on calcium pectate gels using a paralled plate viscoelasto-meter. Linear viscoelastic behaviour was observed and the response was consistent with a model containing a Maxwell element in series with three Voigt elements. When gels were prepared with the calcium level necessary for maximum gel strength a linear relationship was found between the reciprocal of the creep compliance and the square of the polysaccharide concentration.
The rheological behaviour of pectate gels had many similarities to gels prepared from alginates containing a high proportion of guluronic acid residues. However, pectate gels were more sensitive to calcium ions than alginate gels and at high calcium levels the Newtonian viscosity of the pectate gel was much higher than that found for the alginates. These differences have been interpreted in terms of the structure and molecular weight of the two polymers.