Comparative Study of Table Margarine Prepared from Moringa oleifera Seed Oil‐Palm Stearin Blend and Commercial Margarines: Composition,Thermal, and Textural Properties

This study aims to produce an oleic acid‐rich table margarine from Moringa oleifera seed oil (MoO)‐palm stearin (PS) blend (70:30, w/w) and compare its composition, thermal behavior, and textural properties during storage with those of commercial margarines (CM1 and CM2). The major fatty acid in MoO/PS blend, CM1 and CM2 is oleic acid (67.85%, 38.54%, and 35.35%, respectively). Hence, many of their triacylglycerols are derived from the acid. MoO/PS blend has a higher complete melting temperature (43.50 °C) compared to CM1 (35.50 °C) and CM2 (35.53 °C). The solid fat content (SFC) of MoO/PS blend at 10 °C (28.7%) is lower than CM1 (32%) and CM2 (68.4%). However, the MoO/PS blend has a higher SFC (6.47%) at 35 °C compared to CMs. At 20 °C, the viscosity of experimental blend margarine (EBM) decreases but CM1 and CM2 increase at the end of the storage study. After 8 weeks of storage, all margarines are harder and CM2 is the hardest. The adhesiveness of EMB and CM2 is similar to the fresh samples while CM1 is more adhesive after storage. In short, it is possible to produce an oleic acid‐enriched margarine from MoO/PS blend that has better textural properties. Practical Applications: Moringa oleifera seed oil is one of the superior oils that contains high levels of oleic acid. However, its high iodine value and low melting point limit its application in the production of margarine. This study shows that direct blending of M. oleifera seed oil with palm stearin could produce margarine with high oleic acid contents and better textural properties in terms of viscosity, hardness, and adhesiveness. The informative data provide supporting evidence for blending of M. oleifera seed oil with palm stearin to produce margarine that could overcome the issues that hinder the M. oleifera seed oil from being produced into margarine.     

ABA low molar mass triblock copolymers in reverse emulsions: A rheological study

The effect of blocks length and molar mass of ABA triblock copolymers on the rheological behavior of water in oil (w/o) emulsions was investigated. Emulsion parameters such as water droplet concentration (and droplet size) of a series of inverted emulsion systems were evaluated. All copolymer/emulsion systems studied showed a non-Newtonian behavior, and the presence of the copolymer in the emulsion system led to an increase of the low shear viscosity when the size of the midblock of the copolymer was in a specific size range. This suggests the formation of a transient network through the interconnection, by the copolymer, of the smaller water droplets present in the emulsion. Consequently, the systems behave as w/o emulsions containing reversibly crosslinked oil-soluble polymers in the continuous phase, resulting in a pronounced shear thinning behavior. For the different emulsions studied, the relative viscosity increased, with few exceptions, with increasing droplet concentration. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A rheological and morphological study of treated PVC

This article reports a rheological and morphological study of poly(vinyl chloride) (PVC) that was subjected to a treatment capable of decreasing the simultaneous mass transfers occurring between liquid food (or simulant) and PVC packaging. The storage modulus (G′), loss modulus (G″), and the loss angle (tan δ), have been used to determine the glass transition temperature using a Rheometric Scientific Dynamic Analyzer. Young's modulus was measured on a dynamometer, and a morphological characterization was carried out with an optical microscope. The obtained results show that treated PVC behaves like a composite material, which is in agreement with a previously established model. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3497–3502, 2003     

Dynamic rheological and morphological study of the compatibility of thermoplastic polyurethane/ethylene–octene copolymer blends

Two grafted ethylene–octene copolymers [POEs; i.e., POE‐g‐maleic anhydried (MAH) and aminated POE (denoted by POE‐g‐NH₂) were used as compatibilizers in immiscible blends of thermoplastic polyurethane (TPU) and POE. The effects of the compatibilizers on the dynamic rheological properties and morphologies of the TPU/POE blends were investigated. The characteristic rheological behaviors of the blends indicated that the strong interactions between the two phases were due to the compatibilization. Microstructural observation confirmed that the compatibilizers were located at the interface in the blends and formed a stable interfacial layer and smaller dispersed phase particle size. Compared with POE‐g‐MAH, POE‐g‐NH₂ exhibited a better compatibilization effect in the TPU/POE blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A rheological study on kinetics of poly(butylene terephthalate) melt intercalation

A multilayered sample with alternatively superposed poly(butylene terephthalate) (PBT) and nonpolar polymer/clay sheets was elaborately prepared to investigate the whole hybridization process of polar polymer. The kinetics of PBT melt intercalation was studied by a rheological approach. The whole intercalation process was demonstrated by the changes of the low‐frequencies viscoelastic response with annealing time. The results of the apparent diffusivities and the calculated activation energy indicate that the PBT/clay hybrid formation presents a molecular weight dependence, which may result from the enhancement of interactions between polar groups on PBT chains and the silicate surface. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1865–1871, 2006     

Polydimethylsiloxane crosslinking kinetics: A systematic study on Sylgard184 comparing rheological and thermal approaches

In this work a systematic investigation of crosslinking kinetics of Sylgard184 polydimethylsiloxane is performed in both isothermal and dynamic conditions. The results are discussed in terms of two conversions, α_C and α_R determined by thermal and rheological analysis, respectively. Thermal analysis can well detect the first stage of the reaction, while rheological analysis starts being sensitive only at longer time. However, once the rheological response is observable, it changes with time faster than the calorimetric one. From rheology experiments it comes out that the gel point occurs at α_R = 0.53, independently of the applied thermal history. At gel point, α_C is around 0.30 indicating that about 30% of the bonds involved in the crosslinking process is enough to create an infinite network. A modified version of the Kamal's autocatalytic model allows to fit and predict the experimental findings from both the techniques; however, two distinct sets of parameters have been used. The results of this work may be a useful tool to design appropriate curing cycles for the preparation of Sylgard184.     

A study of the rheological behavior of high‐temperature polymer electrolyte membrane solutions

The viscosity behavior of various compositions of polymer electrolyte membrane solutions, which are later hydrolyzed into proton conducting membrane film for fuel cells, is characterized. Using the Carreau‐Yasuda model and time–temperature superposition, an empirical model relating the viscosity as a function of temperature and shear strain rate has been developed for several membrane solution compositions. It is observed that the viscosity of the non‐Newtonian membrane has a strong correlation to the membrane's inherent viscosity (a property determined during membrane synthesis). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A rheological study of the gelling of UF polycondensates

The gelling process of urea–formaldehyde resins has been investigated by rheological methods. The gel point values were determined by three methods, and compared with those obtained by low resolution impulsional ¹H‐nuclear magnetic resonance. The activation energy of the curing process was determined and the effect of the molar ratio was investigated. In addition, the critical power exponents were calculated and the parameters of the relaxation modulus function were also determined. Equations describing the gel time as a function of degree of conversion and reactants molar ratio are presented. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1296–1302, 2000     

Effects of microstructures on the viscoelastic and rheological properties of metallocene‐catalyzed cyclo‐olefin copolymers: A preliminary study

We characterized metallocene‐catalyzed cyclo‐olefin copolymers (mCOCs) with similar heat distortion temperatures but dramatic differences in melt‐flow indices to understand how the molecular conformation affected their rheological and viscoelastic properties. The mCOC conformations were identified with ¹³C‐NMR, whereas the viscoelastic and rheological properties were measured with cone‐and‐plate and high‐pressure capillary rheometers. Our preliminary results showed that the mCOC rheological and viscoelastic properties might depend strongly on the conformation rather than the norbornene content, molecular weight, and molecular weight distribution. mCOCs containing ‐NNN‐ locks (where N represents norbornene) exhibited stronger molecular entanglements than those having no ‐NNN‐ blocks, as reflected in lower crossover frequencies and higher crossover torque. Furthermore, the existence of larger rigid ‐NNN‐ blocks resulted in higher molten viscosities and flow activation energies. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3695–3701, 2002     

结合吸附模型预测油水液滴的界面流变性质

界面活性分子在油水界面的吸附将改变其界面性质,如界面张力、界面流变性质,从而影响乳状液体系的稳定。通过吸附模型较为准确地描述活性分子在界面上的吸附行为,是定量描述油水界面性质的有效方法之一。以Span80为界面活性物质,模拟油、去离子水为实验介质,研究了低于及超过临界胶束浓度(实验中确定为0.45 mmol·L^-1)下界面张力及界面扩张模量的影响特性,表现为界面扩张模量随Span浓度的增加而先增大后减小的趋势。将描述纯扩散弛豫的Lucassen-van den Tempel模型,同Langmuir、Frumkin、reorientation和rigorous reorientation(严格重排)吸附模型相结合,用于预测含活性分子油水界面张力及扩张流变的性质;结果表明,结合严格重排吸附模型能够准确地预测油水界面张力,界面扩张模量、相角、弹性和黏性模量随浓度、频率的变化趋势。     

A study of rheological properties of cellulose diacetate in acetone solution at low and high shear rates

The rheological properties of cellulose diacetate (CDA) with different intrinsic viscosity (IV) and different concentration in acetone solutions were studied at low and high shear rates. The zero-shear viscosity increased and the structural index increased, when the IV of CDA was increased or the acetone solution concentration was increased. Evidence suggested that a sulfate structure may be forming. It is shown that the increase of hemicellulose and sulfur content is associated with an increase of chain entanglements between CDA molecules and the abnormal increase of solution zero-shear viscosity. At a high shear rate, the correlation curve between inlet pressure drop and solution concentration obtained by Bagley method analysis shows an inflection point, which appears to be the critical concentration at which the cellulose diacetate molecular chains in the solution form a long range entangled elastic network. After the concentration exceeds a certain range of above critical points, the entanglement of the molecular chains in the solution is significantly enhanced. The zero shear viscosity inflection point concentration calculated by the rheological curve with low shear velocity and the inlet pressure drop inflection point concentration calculated by the capillary rheological calculation have good consistency.     

Phenol–formaldehyde–pyrolytic oil resins for wood preservation: A rheological study

The rheological properties of a phenol–formaldehyde resin containing various ratios of softwood pyrolytic oil as phenol substitute were investigated using the simple Bingham rheological model for viscoplastic fluids. Flow activation energy was determined for the various resin blends and the pyrolytic oil between room temperature and 50°C and correlations relating the flow activation energy to the weight fraction of pyrolytic oil in the resin are proposed. Apparent crosslinking activation energy with and without copper chloride used as an activator was also evaluated based on two gel time measurements between 75 and 105°C. A significant decrease in activation energy was observed for the phenol–formaldehyde resin cured with copper chloride, while the effect was less important for resins containing pyrolytic oil even when gel times were much shorter for PF‐resins. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

High temperature stability of different polymer‐modified bitumens: A rheological evaluation

Polymer‐modified binders are increasingly used by the pavement industry. In practice, the bituminous binders are stored at high temperatures previous to its application on the road. The instability problems of the bitumen due to the polymer‐rich phase separation may affect the final properties of the pavement. Most polymers tend to be insoluble, to some degree, in the bitumen matrix, and phase separation may result. Chemical compatibility between the polymer additive and the bitumen, and processing conditions, are crucial to obtain suitable properties of the polymer‐modified bitumens. In this work, different polymer‐modified binders were manufactured by using a high‐shear mixing device. Once a good mechanical dispersion of the polymer in the bitumen matrix was achieved, the binders were stored in tubes at high temperatures. During the storage, the unstable polymer‐rich phase segregates and starts to ascend up to the surface. The progression of the polymer phase separation was followed through the evolution of the linear viscoelastic and the viscous properties of the samples collected, after different storage periods, from the top part of the storage tube. From the experimental results obtained, we may conclude that the use of a reactive polymer as additive is a promising alternative to obtain more stable binders. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 103: 1166–1174, 2007     

A study of rheological limitations in rotary jet spinning of polymer nanofibers through modeling and experimentation

The recently popularized method of rotary jet spinning (RJS) or centrifugal spinning is investigated to evaluate the rheological limitations of polymer solutions and melts to optimal spinnability. The influence of Newtonian or non-Newtonian behavior of the polymer on spinnability is discussed. We observe that highly viscous polymers tend to block the die channels within a rotary jet spinneret and therefore suggest the use of relatively low Newtonian viscosities of between 1 and 10 Pa s for optimal fiber production. Computational fluid dynamics simulations are used in conjunction with experimental data to establish important processing parameters, such as typical shear rates in the device and optimal polymer melt or solution viscosities. A theoretical model for RJS is compared to measured fiber diameters. The comparison shows that although fiber diameters can be estimated very roughly in the case of polymer solutions, the prediction of fiber diameter in the case of polymer melts require further modeling work. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48963.     

Effect of the type of SAN in SAN/CPE blend: Morphology,mechanical, and rheological properties

The effect of the molecular weight and acrylonitrile (AN) content of the styrene-acylonitrile copolymer (SAN) on the morphology, mechanical, and rheological properties of SAN/chlorinated polyethylene (CPE) blends was studied. The interaction between dispersed particle and matrix is expected to be optimal at the 25% AN content of SAN. Phase inversion from a dispersion to a continuous phase appears to occur above 50 wt % CPE. Mechanical properties increased with molecular weight at a constant AN content of SAN. Morphological, mechanical, and rheological properties were more sensitive to the AN content, rather than the molecular weight of SAN. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 27–36, 1998     

Linear low‐density polyethylene/poly(ethylene terephthalate) blends compatibilization prepared by an eccentric rotor extruder: A morphology,mechanical, thermal,and rheological study

In this study, various poly(ethylene terephthalate) (PET) and linear low‐density polyethylene (LLDPE) with maleic anhydride‐grafted LLDPE (LLDPE‐g‐MAH) compatibilizer were melt blended under an elongational flow. A novel extrusion device, eccentric rotor extruder (ERE), was developed to supply such flow during the process. Including morphology, mechanical properties, melting behavior, and rheological behavior were studied. The morphological study showed that the compatibility between LLDPE and PET was greatly improved with LLDPE loading up to 80 wt %. Mechanical tests indicated that LLDPE could toughen PET to some extent. Moreover, a comparison of samples prepared between ERE and conventional extruder was made and demonstrated the sample prepared by ERE can exhibit better mechanical properties. Differential scanning calorimetry results revealed that PET can promote the crystallinity of LLDPE. Rheological behavior indicated that the complex viscosity of the blends exhibited strong shear thinning phenomenon with increasing LLDPE content, particularly in high‐frequency range blend with the LLDPE weight ratio of 80 wt % was more sensitivity to shear rate than neat LLDPE. The G′‐G″ curves of the blends also revealed that the microstructure of the blends changed significantly with the addition of LLDPE which was consistent with the scanning electron micrographs that PET particles became smaller and distributed more uniform with increasing LLDPE content. Furthermore, the blends showed similar stress relaxation mechanism with adding LLDPE content from 60 to 100 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46489.     

A comparative study of the effect of some paraffinic oils on rheological and dynamic properties and behavior at low temperature in EPDM rubber compounds

The influence of some paraffinic oils on rheological properties, dynamic properties, and behavior at low temperature of various ethylene–propylene–diene monomer rubber (EPDM) compounds was studied. Three different types of EPDM, Dutral TER 4049, Dutral Ter 4038, and Nordel IP 4770 R, and five different paraffinic oils were used. The properties of the compounds were evaluated with reference to the oil characteristics: viscosity, composition, glass transition temperature, and solubility parameter. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1825–1834, 2005     

Effects of quasi‐nanogel particles on the rheological and mechanical properties of natural rubber: A new insight

The influence of sulfur‐crosslinked, quasi‐nanosized gels on the rheological and mechanical properties of raw natural rubber (NR) was investigated. Latex gels with different crosslink densities were prepared through the variation of the sulfur‐to‐accelerator ratio. These gels were characterized by dynamic light scattering, solvent swelling, and mechanical properties. The gels were mixed with raw NR latex at concentrations of 2, 4, 8, and 16 phr, and their effect on the rheological properties of NR was studied by Monsanto processability tester. The presence of gel in raw NR reduced the apparent shear viscosity and die swell considerably. Initially, the viscosity decreased up to a 8 phr gel loading and then increased with an increase in the gel loading. However, the change in the viscosity was related to the crosslink density of the gels. A new empirical equation relating the viscosity, volume fraction of the gels, and crosslink density was proposed. The die swell of gel‐filled raw NR was at least 10% lower than that of unfilled raw NR and decreased with an increase in the gel loading. The effect of the gels on the die swell properties was explained through the calculation of the principal normal stress difference of gel‐filled NR systems. Scanning electron photomicrographs of the extrudates revealed much better surface smoothness for the gel‐filled virgin rubber systems than for the unfilled rubber. The addition of the gels to raw NR increased the modulus and tensile strength, whereas the elongation at break decreased. The effect of the gels on the dynamic mechanical properties of NR was also investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

陶瓷材料微波加热特性计算分析

为更清楚和准确了解材料微波加热行为,提出了球形陶瓷材料微波加热升温过程的一个数学模型。用有限差分隐式格式推导了离散方程,通过编程进行了数值迭代计算,得到了Si C陶瓷球加热升温过程动态温度曲线,并分析了其加热基本特性。在此基础上,探讨了材料热导率和微波功率的影响。计算结果表明,微波体积加热效应决定了物体内部温度分布比较均匀;与普通加热方式不同,微波加热的物体内部温差随时间逐渐增加,加热初期温差比较小,这一特性决定了微波加热特别适合快速加热;对每一微波功率,有一个最大稳定温度值,因此烧结不同材料,所用微波功率应不同。材料热导率越大,物体内部温度分布越均匀,但能达到的稳定温度越低;微波功率越大,物体能达到的稳定温度越高,但物体内部温度均匀性越差,因此,为保证材料均匀烧结,不宜用大功率。