Rheological and thermal properties of soybean oils with modified FA compositions

Rheological and thermal properties of five soybean oils with modified FA compositions were studied. Viscosity decreased with increasing temperature at different rates for the different oils. Oil with a high-oleic acid content had higher viscosity and a greater rate of change than did oils with typical FA compositions, oil with low-saturated FA or low-linolenic acid content, or oil from lipoxygenase-free soybeans. The melting and crystallization behaviors of the oils were examined using DSC. The high-oleic acid oil and the oil with low-saturated FA content had different DSC profiles compared with the other oils. Specific heat capacities of oils were estimated using a mathematical model; the high-oleic acid oil had a higher specific heat value, and the low-saturated FA oil had a lower value than did the other oils.     

不同聚合物基体对复合材料性能的影响

研究了以不同类型聚合物为基体的高分子夏合材料的导电性和力学强度的变化规律，并从聚合物的结晶性，对填料的粘结性及其表面张力等方面进行了分析。若基体的结晶性和极性较强，则在导电性提高的同时，冲击强度下降；若基体本身比较柔软且对填料有足够的亲和力，则在一定的填料含量范围内，导电性和冲击强度可同时提高。     

Triacylglycerol composition and structure in genetically modified sunflower and soybean oils

Changes in composition were examined in oils extracted from genetically modified sunflower and soybean seeds. Improvements were made to the analytical methods to accomplish these analyses successfully. Triacylglycerols (TAG) were separated on two 300 mm × 3.9 mm 4μ Novapak C18 high-performance liquid chromatography (HPLC) columns and detected with a Varex MKIII evaporative light-scattering detector. Peaks were identified by coelution with known standards or by determining fatty acid composition of eluted TAG by capillary gas chromatography (GC). Stereospecific analysis (fatty acid position) was accomplished by partially hydrolyzing TAG with ethyl magnesium bromide and immediately derivatizing the resulting diacylglycerols (DAG) with (S)-(+)-1-(1-naphthyl)ethyl isocyanate. The derivatized sn-1,2-DAG were completely resolved from the sn-2,3-DAG on two 25 mm × 4.6 mm 3 μ silica HPLC columns. The columns were chilled to −20°C to obtain baseline resolution of collected peaks. The distribution of fatty acids on each position of the glycerol backbone was derived from the fatty acid compositions of the two DAG groups and the unhydrolyzed oil. Results for the sn-2 position were verified by hydrolyzing oils with porcine pancreatic lipase, isolating the resulting sn-2 monoacylglycerols by TLC, and determining the fatty acid compositions by GC. Results demonstrated that alterations in the total fatty acid composition of these seed oils are determined by the concentration of TAG species that contain at least one of the modified acyl groups. As expected, no differences were found in TAG with fatty acid quantities unaffected by the specific mutation. In lieu of direct metabolic or enzymatic assay evidence, the authors’ positional data are nevertheless consistent with TAG biosynthesis in these lines being driven by the mass action of available acyl groups and not by altered specificity of the acyltransferases, the compounds responsible for incorporating fatty acids into TAG.     

Dielectric properties of polymer/ceramic composites based on thermosetting polymers

Summary A series of thermosetting polymer/ceramic composites were prepared. Three kinds of thermosetting polymers, i.e. cyanate resin, bismaleimide resin, and epoxy resin, were used as matrixes, and BaTiO₃ particles were as fillers. The dielectric properties of these composites were investigated. Experimental data of the dielectric constants were fitted to several theoretical equations in order to obtain the best-fitting equations of the dielectric constants of these composites. The result indicates that the dielectric constants of composites all increase with the increase of BaTiO₃ content. Using bismaleimide resin and epoxy resin as matrixes, the dielectric losses both increase obviously as the amount of BaTiO₃ particles is increased, but the dielectric loss of cyanate/BaTiO₃ composite decreases. With the increase of the frequency, the variation ranges of the dielectric constant and dielectric loss of cyanate/BaTiO₃ composite are both the smallest. The predications of the effective dielectric constants by Lichterecker mixing rule are in good agreement with experiment data.     

有机硅改性苯丙乳液的合成及其性能研究

采用半连续乳液聚合反应的方法合成有机硅改性苯丙乳液,系统考察了乙烯基硅油、乳化剂、引发剂等因素对乳液聚合反应及乳胶粒尺寸和涂膜性能的影响。以乙烯基质量分数为0.30%的羟基硅油与苯乙烯、丙烯酸丁酯、甲基丙烯酸乳液共聚,以过硫酸铵(APS)为引发剂,采用m(十二烷基苯磺酸钠)∶m(聚乙二醇辛苯基醚)=1∶2的复合型乳化剂,70℃下共聚5～6h。所得的乳液带蓝色荧光,乳胶粒粒径为70～100nm,粒径分布窄,乳液具有良好的钙离子稳定性、贮存稳定性和耐温性,涂膜耐水性较好。     

改性空心玻璃微珠/环氧树脂复合材料力学性能研究

采用偶联剂对玻璃微珠表面进行改性处理,借助超声波振动,使改性空心玻璃微珠在环氧树脂中均匀、稳定分散,增强了玻璃微珠与环氧树脂之间的相容并探讨了改性空心玻璃微珠对环氧树脂力学性能的影响。结果表明,复合材料中改性空心玻璃微珠添加质量分数为3%时,其拉伸强度达到最大值68.54 MPa,与空白样相比提高了20.3%;冲击强度达到最大值24.42 kJ/m2,比纯环氧树脂提高了166%;KIC(断裂韧性)达到最大值2.338 MPa/m2,是空白试样的2.27倍,增韧效果较为明显。     

Mechanical properties and morphology of impact modified polypropylene–wood flour composites

The mechanical properties and morphology of polypropylene/wood flour (PP/WF) composites with different impact modifiers and maleated polypropylene (MAPP) as a compatibilizer have been studied. Two different ethylene/propylene/diene terpolymers (EPDM) and one maleated styrene–ethylene/butylene–styrene triblock copolymer (SEBS–MA) have been used as impact modifiers in the PP/WF systems. All three elastomers increased the impact strength of the PP/WF composites but the addition of maleated EPDM and SEBS gave the greatest improvements in impact strength. Addition of MAPP did not affect the impact properties of the composites but had a positive effect on the composite unnotched impact strength when used together with elastomers. Tensile tests showed that MAPP had a negative effect on the elongation at break and a positive effect on tensile strength. The impact modifiers were found to decrease the stiffness of the composites. Scanning electron microscopy showed that maleated EPDM and SEBS had a stronger affinity for the wood surfaces than did the unmodified EPDM. The maleated elastomers are, therefore, expected to form a flexible interphase around the wood particles giving the composites better impact strength. MAPP further enhanced adhesion between WF and impact-modified PP systems. EPDM and EPDM–MA rubber domains were homogeneously dispersed in the PP matrix, the diameter of domains being between 0.1–1 μm. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1503–1513, 1998     

尼龙6改性研究

采用经化学改性的芳纶纤维增强尼龙6,并通过红外光谱和电镜分析其界面层,结果表明芳纶纤维经异氰酸酯化及封端稳定处理后,其表面所接技的不稳定基团-NCO转化成稳定的-NHCO-,封端结果较为明显;改性后纤维表面附有接枝物,从而使表面粗糙程度大大增加。用挤出和注塑的方法加工了PA6／Kevlar纤维（KF）复合材料,研究了它的拉伸、弯曲和冲击性能破坏形态。力学性能测试表明了改性尼龙6复合材料的拉伸和弯曲强度得到了改善,但冲击性能略为下降。     

改性无醛大豆基胶粘剂的研究

采用表面活性剂(A)改性豆粕的方法制备了无甲醛大豆基胶粘剂。研究了A的用量、热压时间和热压温度对大豆基胶粘剂胶合性能的影响,采用差示扫描量热(DSC)仪对大豆基胶粘剂的热性能进行了研究。研究结果表明,当w(A)=2.5%(相对于豆粕而言)、热压时间为15min和热压温度为140～160℃时,大豆基胶粘剂表现出最佳的胶合强度;其主要的热反应在160℃以下完成。     

Frying stability of soybean and canola oils with modified fatty acid compositions

Pilot plant-processed samples of soybean and canola (lowerucic acid rapeseed) oil with fatty acid compositions modified by mutation breeding and/or hydrogenation were evaluated for frying stability. Linolenic acid contents were 6.2% for standard soybean oil, 3.7% for low-linolenic soybean oil and 0.4% for the hydrogenated low-linolenic soybean oil. The linolenic acid contents were 10.1% for standard canola oil, 1.7% for canola modified by breeding and 0.8% and 0.6% for oils modified by breeding and hydrogenation. All modified oils had significantly (P<0.05) less room odor intensity after initial heating tests at 190°C than the standard oils, as judged by a sensory panel. Panelists also judged standard oils to have significantly higher intensities for fishy, burnt, rubbery, smoky and acrid odors than the modified oils. Free fatty acids, polar compounds and foam heights during frying were significantly (P<0.05) less in the low-linolenic soy and canola oils than the corresponding unmodified oils after 5 h of frying. The flavor quality of french-fried potatoes was significantly (P<0.05) better for potatoes fried in modified oils than those fried in standard oils. The potatoes fried in standard canola oil were described by the sensory panel as fishy.     

Synthesis and properties of boron-containing soybean oil based thermosetting copolymers

The first example of boron-containing soybean oil based copolymers was prepared from soybean oil, styrene, divinylbenzene and 4-vinylphenyl boronic acid by cationic polymerization using boron trifluoride etherate as initiator. Soxhlet extraction and NMR spectroscopy indicate that the copolymers consist of a crosslinked network plasticized with varying amounts of oligomers and unreacted oil. The thermal degradation mechanism was studied and the thermal, dynamomechanical and flame retardant properties of these materials were examined. Thermosets with glass transition temperatures ranging from 43 to 60 °C, which are thermally stable below 350 °C and with LOI values from 23.7 to 25.6 were obtained. The LOI tests indicate that the flame retardant properties of vegetable oil can be improved by adding boron covalently bonded to the polymer.     

Friction and adsorption properties of normal and high-oleic soybean oils

The steel/steel boundary friction properties of soybean oil (SBO) and high-oleic soybean oil (HOSBO) are compared. HOSBO is significantly more saturated than SBO and more oxidatively stable. Changes in degree of unsaturation affect lateral interactions of adsorbate molecules, which in turn affects their adsorption and, hence, their boundary lubrication properties. To investigate this possibility, the free energies of adsorption (ΔG _ads) of SBO, HOSBO, and methyl laurate (ML) were determined from the analysis of friction-derived adsorption isotherms using the Langmuir and Temkin adsorption models. The results showed a stronger adsorption for the vegetable oils than for ML, an indication of multiple interactions between the ester groups of the triglycerides and the steel surface. The result also showed no difference in the ΔG _ads values of SBO and HOSBO obtained using either the Langmuir or Temkin models. This was interpreted as an indication of the lack of appreciable net lateral interaction between triglyceride adsorbates.     

TDI/BPO改性PBS的力学性能研究

本文采用扩链手段和交联手段对PBS进行改性研究.分别选用甲苯2,4-二异氰酸酯(TDI)为扩链剂,过氧化苯甲酰(BPO)为交联剂.使用乌氏黏度计、索氏抽提器对改性体系的特性黏数和交联度进行测定;使用哈克转矩流变仪、毛细管流变仪、差示扫描量热仪、万能拉力测试机等手段测试了改性体系的加工性能,流变性能,结晶与热性能,以及力...     

A simulation study on the effects of shear flow on the microstructure and electrical properties of carbon nanotube/polymer composites

We employ a fiber-level simulation technique to simulate carbon nanotube (CNT)/polymer composites in simple shear flow. This model incorporates CNT flexibility, irregular CNT equilibrium shapes and CNT interactions. Electrical conductivity of the composites is determined using a resistor network algorithm. Tunneling resistance of the insulating matrix film between nanotubes is also considered. We show that the rate of imposed shear flow influences the composite conductivity by facilitating the formation or destruction of the conductive aggregates. In addition, the conductivity evolution during shearing for different concentrations is investigated. At low concentration, percolating clusters form and break simultaneously which causes large conductivity fluctuations during the simulations. When sufficiently large concentrations are reached, percolating clusters persist during shearing and the conductivity fluctuations decrease. In agreement with previous research we determine that increasing the shear rate causes alignment of the nanotubes in the flow direction. We show that upon shearing at constant shear rate, the system attains a state with substantially constant electrical conductivity, nanotube orientation and agglomerate size that is a function of the applied shear rate. The state reached for a given shear rate is independent of the initial state of orientation and aggregation.     

超支化聚合物改性环氧树脂的研究进展

超支化聚合物因其独特的结构和性能特点,已在众多领域得到了广泛的应用,尤其是在热固性树脂的改性中的应用,可作为热固性树脂的增韧剂。该文介绍了环氧树脂的性能特点及应用,超支化聚合物的结构及特点,着重论述了近年来超支化聚合物在改性环氧树脂力学性能、固化行为及热性能方面的研究进展,并指出了超支化聚合物在环氧树脂和其它热固性树脂改性方面的发展方向。     

Effects of alkali treatment on the properties of WF/PLA composites

In this study, composites of thermoplastic poly (lactic acid) filled with wood flour (WF) were prepared via melt extrusion. Before that, alkali treatment was performed on WF to improve the properties of the WF/PLA composite materials. The effect of the solution concentrations of NaOH, namely 0.5, 1.0, 5.0, and 10.0%, on mechanical properties of the composites was evaluated. The results showed that the properties of the composites with treated WF were enhanced greatly compared with that of the untreated composites. The composites had a best improvement in its compatibility and mechanical strength when the concentration of NaOH solution was 5.0%. The brittle fracture of composites showed that the chemical modification of WFs improved the compatibility between the filler and matrix.     

改性炭黑对复合材料介电性能的影响

为提高复合材料的介电性能,采用硅烷偶联剂KH550对炭黑表面进行改性,并与聚偏氟乙烯、钛酸钡制成复合材料,研究了复合材料介电性能.结果表明,硅烷偶联剂KH550改变了炭黑表面结构,使炭黑/聚偏氟乙烯复合材料的介电常数在104 Hz时提高了15％以上,填充钛酸钡后介电常数进一步增加,介电损耗可控制在较低的范围.     

The effect of various anhydride modifications on mechanical properties and water absorption of oil palm empty fruit bunches reinforced polyester composites

The chemical modification of oil palm empty fruit bunches (EFB) using non‐catalysed reaction with acetic, propionic and succinic anhydrides were investigated. Proof of modification was indicated by the increase of weight and was confirmed by Fourier‐transform infrared analysis (FT‐IR). The mechanical and water‐absorption properties of all anhydride‐modified EFB composites were evaluated at different volume fractions (V_f). The properties were improved for these modified fibres, whereas unmodified EFB fibres exhibited poor mechanical properties and higher water absorption. Acetic anhydride modification showed the greatest benefit on composite properties, followed by propionic and succinic anhydride modification. © 2001 Society of Chemical Industry     

Effect of interesterification on the structure and physical properties of high-stearic acid soybean oils

Triglyceride structures of genetically modified soybean oils high in stearic acid were determined by high-pressure liquid chromatography, and their physical properties were assessed by dilatometry and dropping point. In their natural state, these oils lack sufficient solids at 10–33°C to qualify as margarine oils. However, after random interesterification, soybean oil containing 17% stearic acid shows a solid fat index (SFI) profile and dropping point closely matching those of a liquid margarine oil. Other oils, with stearic acid contents in the range of 20–33%, showed appreciable SFI values at 10°C but lacked sufficient solids at 21.1–33.3°C. After random interesterification, these oils also exhibited SFI profiles suitable for soft tub margarine, and their drop points increased from 18–19°C to 36–38°C.     

环氧树脂改性有机硅聚合物的合成与应用性能研究

正硅酸乙酯水解可得有机硅聚合物,但产物分子量不高,成膜性差。用环氧树脂对其改性,制得物的涂膜成膜性优良,且大大缩短固化时间。研究了水解温度与时间,催化剂种类,溶剂用量和环氧树脂用量、反应温度与时间对改性物的影响。结果表明,水解温度50℃,时间3h,硫酸催化,乙醇用量35%,环氧树脂用量20%～50%,反应温度50℃,反应时间1h,涂膜性能优良。