微波提取苹果渣中总黄酮的工艺研究

采用微波辐射技术,以乙醇提取苹果渣中黄酮类化合物。考察了乙醇浓度、微波功率、处理时间、料液比和浸泡时间对总黄酮提取率的影响。结果表明,最佳工艺条件为:70%乙醇,微波萃取2 min,微波功率为350 W,料液比1∶30(g/mL),总黄酮1次提取率0.683 7%。     

溶剂、微波萃取法提取柑橘皮精油

用溶剂萃取和微波萃取法提取柑桔皮精油,研究了溶剂种类、浸泡时间、颗粒大小、料液比、微波功率对精油提取率的影响。结果表明,最佳溶剂为乙醇,溶剂萃取最佳工艺为:料液比1∶6 g/mL,浸泡时间48 h,颗粒粒度>60目,精油提取率可达到10.2%;微波萃取最佳提取工艺为:料液比为1∶6 g/mL,浸泡时间48 h,颗粒粒度40目,微波时间90 s,精油提取率可达到14.7%。     

岗梅根总皂苷微波提取及抗氧化活性研究

以野生岗梅根为原料，确定了微波法提取总皂苷最佳工艺为微波功率480 W,料液比1∶40(g∶mL),微波时间2 min,提取次数4次，此条件下，总皂苷提取率为5.040%。有机溶剂对粗提液进行萃取纯化，并研究萃取后水层、乙酸乙酯层、粗提液对DPPH·、·OH清除能力，结果表明萃取后水层和乙酸乙酯层对DPPH·、·OH清除能力高于粗提液层的。在实验浓度范围内，清除DPPH·、·OH的能力随岗梅根总皂苷浓度增大而加强，清除能力与皂苷浓度呈正相关的量效关系。     

微波辅助提取洋葱籽中皂苷类成分工艺研究

用微波辅助甲醇提取洋葱籽中的皂苷类成分,考察甲醇浓度、微波时间、微波功率、料液比对皂苷类成分得率的影响。结果表明,最佳提取工艺条件为:甲醇浓度100%,料液比1∶25 g/m L,微波功率400 W,微波时间25 min,总皂苷提取率为6.87%。     

微波辅助提取洋葱籽中皂苷类成分工艺研究

用微波辅助甲醇提取洋葱籽中的皂苷类成分,考察甲醇浓度、微波时间、微波功率、料液比对皂苷类成分得率的影响。结果表明,最佳提取工艺条件为:甲醇浓度100%,料液比1∶25 g/m L,微波功率400 W,微波时间25 min,总皂苷提取率为6.87%。     

超声提取女贞子中黄酮类化合物的工艺研究

采用超声辅助乙醇提取女贞子中黄酮类化合物,考察乙醇浓度、超声功率、超声时间和料液比对提取率的影响。结果表明,最佳提取条件为:乙醇体积分数为50%,料液比1∶70(g/mL),600 W功率下提取20 min,并通过实验确定在此条件下黄酮类化合物的提取率达到13.61%。     

响应面法优化百合多糖的超声辅助提取工艺

在单因素实验的基础上,以液料比、提取时间、超声功率、提取次数为考察因素,以百合多糖得率为评价指标,采用响应面法优化百合多糖的超声辅助提取工艺。确定最佳提取工艺为:液料比21∶1 (mL∶g)、提取时间4 min、超声功率400 W、提取次数2次,在此条件下,百合多糖得率为12.936%,与预测值(13.150%)相差0.214%。该优化提取工艺合理、可行,可用于百合多糖的提取。     

低含量油污染土壤中总石油烃测定萃取方法研究

对低含量油污染土壤中总石油烃(TPH)测定萃取方法进行了研究,通过制备模拟污染样品筛选出最优萃取溶剂和提取方法,考察了时间、料液比、温度和功率对超声萃取的影响,红外法测定土壤中的石油烃含量。结果表明,超声萃取土壤中石油烃的最优条件为:以CH_2Cl_2萃取17 min,功率150 W,萃取次数为2次,料液比1∶3 g/mL。该条件适用于低含量油污染土壤中总石油烃的萃取。以最优条件对不同污灌年限的新疆某污灌区土壤基进行总石油烃含量测定,石油烃浓度范围为172.01~320.56 mg/kg,RSD为4.3%~9.8%,表明超声萃取法回收率高、测定结果准确,重复性良好。     

低含量油污染土壤中总石油烃测定萃取方法研究

对低含量油污染土壤中总石油烃(TPH)测定萃取方法进行了研究,通过制备模拟污染样品筛选出最优萃取溶剂和提取方法,考察了时间、料液比、温度和功率对超声萃取的影响,红外法测定土壤中的石油烃含量。结果表明,超声萃取土壤中石油烃的最优条件为:以CH_2Cl_2萃取17 min,功率150 W,萃取次数为2次,料液比1∶3 g/mL。该条件适用于低含量油污染土壤中总石油烃的萃取。以最优条件对不同污灌年限的新疆某污灌区土壤基进行总石油烃含量测定,石油烃浓度范围为172.01³20.56 mg/kg,RSD为4.3%320.56 mg/kg,RSD为4.3%⁹.8%,表明超声萃取法回收率高、测定结果准确,重复性良好。     

剑麻皂素提取工艺研究

以剑麻水解物为原料,乙醇为溶剂,对剑麻皂素提取工艺进行研究。考察了乙醇浓度、皂素在乙醇中的浓度、提取时间、皂素/活性炭质量比、脱色时间对剑麻皂素产品收率和质量的影响。以高效液相色谱作为分析手段,通过单因素和正交设计实验,确定了乙醇提取剑麻皂素的最佳工艺条件:乙醇浓度95%,皂素在乙醇中的浓度为7.8g·L~(-1),提取时间1h,皂素/活性炭=1∶1.8,脱色时间1.5h。在此条件下,皂素含量为92.14%,提取率为81.16%,产品的醇溶度和色泽合格。     

Some structural aspects of sisal fibers

A critical account has been presented of the recent investigation on the chemical modification of lignocellulosic sisal fibers. The molecular structure of the paracrystalline cellulose, which forms the major constituent of the fiber, was studied by x-ray diffraction technique. Scanning electron microscope examination of the multicellular structure, surface topology, and fracture morphology of the fiber was carried out. The mechanical properties of the sisal ultimate cell and the “technical” fiber have been investigated by means of a microextensometer and an Instron tensile tester, respectively.     

Preparation and characterization of benzylated sisal fibers

Sisal fibers were benzylated under different conditions and were characterized with infrared spectroscopy, X‐ray diffraction, thermal analysis, and scanning electron microscopy. The benzylation reaction was monitored by the mass gain as a function of the reaction time. In the first stage, there was a mass loss associated with the loss of lignin and polyoses from the raw fiber, which was accompanied by an increase in mass due to benzyl incorporation. When fiber delignification was carried out before benzylation, the mass gain curves of the benzylation reaction presented no initial mass loss and a much higher mass gain. Benzylation promoted several morphological changes: (1) the loss of the parenchyma cells, (2) the defibrillation of the technical fibers into ultimate fibers, (3) the microdefibrillation of the ultimate fibers, and (4) benzyl incorporation. The crystallinity of the fibers decreased with benzylation, as observed by X‐ray diffraction. The thermal stability of the fibers varied according to the treatment used. Other changes promoted in the fibers by chemical modification were examined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2957–2965, 2003     

Short sisal fiber reinforced styrene-butadiene rubber composites

Styrene-butadiene rubber (SBR) composites were prepared by incorporating short sisal fibers of different lengths and concentrations into the SBR matrix in a mixing mill according to a base formulation. The curing characteristics of the mixes were studied and the samples were vulcanized at 150°C. The properties of the vulcanizates such as stress-strain behavior, tensile strength, modulus, shore-A hardness, and resilience were studied. Both the cured and uncured properties showed a remarkable anisotropy. It has been found that aspect ratio in the range of 20–60 is effective for sufficient reinforcement. The mechanical properties were found to increase along and across the grain direction with the addition of fibers. The effects of fiber length, orientation, loading, type of bonding agent, and fiber-matrix interaction on the properties of the composites were evaluated. The extent of fiber orientation was estimated from green strength measurements. The adhesion between the fiber and the rubber was enhanced by the addition of a dry bonding system consisting of resorcinol and hexamethylene tetramine. The bonding agent provided shorter curing time and enhanced mechanical properties. The tensile fracture surfaces of the samples have been examined by scanning electron microscopy (SEM) to analyze the fiber surface morphology, orientation, fiber pull-out, and fiber-matrix interfacial adhesion. Finally, anisotropic swelling studies were carried out to analyze the fiber-matrix interaction and fiber orientation. © 1995 John Wiley & Sons, Inc.     

Ultrathin and nanofibers via room temperature electrospinning from trifluoroacetic acid solutions of untreated lignocellulosic sisal fiber or sisal pulp

Lignocellulosic sisal fiber (LSF) and sisal pulp (SP) were electrospun at room temperature from solutions in trifluoroacetic acid (TFA) prepared at concentrations of 2 × 10⁻² g mL⁻¹ and 3 × 10⁻² g mL⁻¹, respectively. Scanning electron microscopy images of the electrospun LSF showed fibers with diameters ranging from 120 to 510 nm. The presence of defects decreased along with increasing the flow rate of the SP solution, which generated nanofibers and ultrathin fibers with diameters in the range of 40–60 (at 5.5 µL min⁻¹) up to 90–200 nm (at 65.5 µL min⁻¹). Despite the known ability of TFA to esterify the hydroxyl groups present in the starting materials, the Fourier transform infrared spectra indicated the absence of trifluoroacetyl groups in the electrospun samples. The thermal stability of the final materials proved suitable for many applications even though some differences were observed relative to the starting materials. This study demonstrated a feasible novel approach for producing nano/ultrathin fibers from lignocellulosic biomass or its main component, which allows for a wide range of applications for these materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41826.     

Grafting starch nanocrystals onto the surface of sisal fibers and consequent improvement of interfacial adhesion in sisal reinforced starch composite

Starch nanocrystals (SNCs) were obtained by the hydrolysis of waxy starch and used to improve the interfacial adhesion of a composite of sisal fibers and starch. Sisal fibers were first treated with acrylic acid (AA), and the modified fibers were then reacted with SNCs to form ester groups. The grafted fibers were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The FTIR and XPS results showed that the SNCs were successfully grafted onto the surface of SF-AA, and an ester linkage was formed during the reaction of AA with the SNCs. The SEM analysis showed that the SNCs were distributed over the fiber surface. Tensile tests and pull-out tests were also performed utilizing a two-parameter Weibull distribution analysis to study the effect of the grafted SNCs on the mechanical and interfacial properties. Compared to the untreated fibers, the interfacial shear strength of the grafted SNCs fibers increased by 79.3%. Therefore, the structural similarity between starch and the SNCs contributed towards their compatibility and improved interfacial properties, with the introduction of SNCs being used as an alternative material for fiber surface modification. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47202.     

剑麻纤维的热处理及热行为的研究

本工作借助红外光谱、X-射线衍射和热重分析等手段，研究了剑麻纤维经热处理后化学结构、聚态结构及热行为的变化。结果表明，在200℃以下热处理的创麻纤维其红外光谱基本不变，密度和结晶度提高，剑麻纤维在空气中的热分解主要分三个阶段进行。在150℃～200℃下进行热处理对剑麻纤维的热行为影响不大。     

Crystalline transition behavior of sisal in cycle process

In this study, the effects of cycle process on crystalline transition behavior of sisal fiber were investigated in various conditions (in air, in composites and in argon) by XRD analysis. The results indicated that the sisal cellulose falls into cellulose I, and the polymorphic transformation didn't occur for sisal cellulose after cycle process. With increasing of thermal cycle times, the crystalline size of sisal became smaller gradually, but the change was not obvious when sisal fiber was treated thermally in air and in argon before five times. The change trend of crystalline index of sisal after cycle process in air and in argon was similar. However, it is different in composites. From once to 10 times cycle process, the crystalline index of sisal fiber was degressive. When the cycle times was close to 15, crystalline index increased gradually. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Behavior of polyolefin blends with acetylated sisal fibers

The influence of acetylation on the mechanical, thermal and thermodegradative behavior of sisal fiber‐reinforced PP, PP/HDPE and PP/HDPE with functionalized and non‐functionalized EPR composites was studied. Acetylation of the fiber improves adhesion of the fiber to the polyolefin matrix. In general, acetylation of the sisal fiber was found to enhance the tensile strength and modulus of the resulting composites, except in some cases. Thermal properties suggest that the mixing and molding temperatures are between 160 and 230 °C and that when acetylated fiber is mixed with polyolefins, greater polymer‐fiber interactions takes place, which slightly favor stability of these composite materials. The results allow us to suggest that a satisfactory profit/cost relation justifies the addition of acetylated fiber to PP, PP/HDPE, and PP/HDPE/EPR. © 2000 Society of Chemical Industry     

Mechanical properties of plasma-treated sisal fibre-reinforced polypropylene composites

In recent years, sisal fibres have become a promising reinforcement for composites because of their low cost, low density, high specific strength, high specific modulus, easy availability and renewability. However, the poor adhesion between the hydrophilic sisal fibre and the hydrophobic thermoplastic matrices has adversely affected the widespread use of these composites. In this study, argon and air-plasma treatments have been used to modify the fibre surfaces under suitable treatment parameters to improve the compatibility between sisal fibres and polypropylene (PP). Sisal fibres and PP fibres are blended together to form a random mat which is then vacuum hot-pressed into a preimpregnated composite sheet. Mechanical properties such as tensile strength and modulus, flexural strength and modulus, and the storage modulus of the composite sheets improve after the incorporation of plasma-treated fibres. Furthermore, scanning electron microscopy analyses reveal the increased surface roughness of sisal fibre. Surface characterisation has been performed by X-ray photoelectron spectroscopy, showing an increase in oxygen/carbon ratio of sisal fibres after plasma treatment.     

Fire behaviour of sisal short fibers reinforced gypsum

The fire behaviour of sisal short fibers reinforeed gypsum in laboratory tests is described Specially designed testing equipment that is easily available has been implemented in this work to analyze the fibers under load and their composite fire performance.