Comparison of ISO 14902:2001 with AOCS Ba 12a-2020 for determining trypsin inhibitor activity in protein products

For measuring trypsin inhibitor activity (TIA), there are two major official methods: American Oil Chemists Society (AOCS) method Ba 12a-2020 and International Organization for Standardization (ISO) 14902:2001. The former was recently approved. The two methods differ in sample preparation, extraction, colorimetric assay systems and TIA calculations. In this study, the two methods were symmetrically compared using three unique sets of samples: assorted protein products of soybeans, pulses, and grains; soybeans boiled for varied durations; and soy white flakes toasted for varied durations. For given samples, significant differences existed in TIA measured by the two methods, resulting from effects related to the assay systems and TIA calculations, not from the difference in sample preparation and extraction. When the same trypsin was used, TIA (in mg trypsin inhibited/g sample) measured by the two methods were highly correlated (r = 0.9973, n = 27), giving an equation of y = 0.5464x − 0.4887, where y represents ISO values and x for AOCS values. The line connecting ratios of ISO/AOCS in TIA and AOCS values remained relatively flat around 0.53 but started to curve down when TIA approached the lowest. Furthermore, for the same samples, TIA values measured by the ISO method decreased with increasing specific activity of trypsin used, while AOCS values remained consistent, leading to decreasing ratios of ISO/AOCS. Therefore, accurate and direct comparison of the two methods was impossible. It could not be resolved by simply changing ISO method's calculations as hypothesized earlier. Regardless, for most samples, ISO values were roughly about 55% of AOCS values.     

Polyethylenimine-modified sugarcane bagasse cellulose as an effective adsorbent for removing Cu(II) from aqueous solution

Polyethylenimine-modified sugarcane bagasse cellulose (SBCMP), as a new adsorbent, was synthesized by the reaction of polyethylenimine (PEI) with sugarcane bagasse cellulose and glutaraldehyde. The adsorption of Cu(II) by SBCMP was pH-dependent, and the higher removal efficiency of Cu(II) appeared in the range of pH 3.0–6.0. The adsorption isothermal data fitted well with the Langmuir model, and the maximum adsorption capacity of SBCMP was up to 107.5 mg/g. The adsorption kinetics was best described by the pseudo-second-order kinetic. The adsorption of Cu(II) by SBCMP was unfavorable at high temperatures, and thermodynamic analyses implied that the adsorption of Cu(II) by SBCMP was an exothermic reaction. Fourier transform infrared spectroscopy (FT-IR) combined with X-ray photoelectron spectroscopy (XPS) revealed that Cu(II) adsorption on SBCMP mainly controlled by the nitrogen atoms of  NH group in PEI. The results of regeneration cycles showed that SBCMP was suitable for reuse in the adsorption of Cu(II) from aqueous solution. These experimental results suggested that SBCMP is expected to be a new biomass adsorbent with high efficiency in removing Cu(II) from wastewater.     

Reinforcement of polypropylene by cellulose microfibers modified with polydopamine and octadecylamine

Cellulose microfibers (CMFs) having surfaces modified with polydopamine (PDPA) and octadecylamine (ODA) were prepared, and their reinforcing abilities for polypropylene (PP) were investigated. The PDPA coating was made via self-polymerization of dopamine (P-CMF), and subsequent alkylation was conducted by the reaction with ODA (OP-CMF). The modified CMFs exhibited improved dispersibility in the PP matrix due to the reduced hydrophilicity. The OP-CMF/PP composite prepared by batch mixing had a higher tensile modulus compared to that for the pure PP and composites with unmodified CMFs. However, excess alkylation lowered the tensile modulus, and the presence of an optimal degree of alkylation was demonstrated. The CMF/PP-IM composites fabricated by injection molding exhibited improved tensile properties compared to those prepared by batch mixing. Both the tensile modulus and yield stress were increased by increasing the CMF content and improved by the surface modification of the CMFs.     

Preparation of treelike and rodlike carboxymethylated nanocellulose and their effect on carboxymethyl cellulose films

In this work, carboxymethyl cellulose (CMC) with low substitution degree, followed by different posttreatments, was applied to prepare treelike CMC nanofibrils (CMCNFs) and rodlike CMC nanocrystals (CMCNCs), and their performance in CMC composite film was evaluated simultaneously. From transmission electron microscopy results, it was found that the treelike CMCNCFs exhibited a lager aspect ratio compared to the rodlike CMCNCs. As for reinforcing CMC film, 4 wt% was the best adding amount, at this time, the tensile strength of CMC/CMCNFs and CMC/CMCNCs composite films was increased by 72.1% and 47.3%, respectively. Moreover, adding these nanofillers to CMC also could enhance the thermal stability of composite films slightly, while the transmittance of composite films was reduced at the same time. In addition, CMC/CMCNFs film was designed as a packaging box to determine its performance. Therefore, this study could reveal the differences of properties for composites with different types of nanocellulose and provide a foundation for further application of nanocellulose.     

Melt processing of nanocomposites of cellulose nanocrystals with biobased thermoplastic polyurethane

Nanocomposites of thermoplastic polyurethane (TPU) with cellulose nanocrystals (CNC) without and with surface treatment are obtained by melt processing. Nanocomposites are obtained with nanofiller weight content near of the theoretical percolation threshold (3.9 wt%). Visual observation of CNC agglomerates is sufficient to prove the inefficiency of the mixing in systems with untreated CNC. The crystallization kinetics of the TPU changes with the addition of CNC and this is confirmed by differential scanning calorimetry analysis. Thermogravimetric analysis prove that the addition of CNC increases the thermal stability of the TPU. From the rheological analysis it is possible to verify the absence of percolation and an intermediate state of sol–gel transition in the nanocomposites. CNC/TPU nanocomposites with 5 wt% of treated CNC present better mechanical performance than de neat TPU and the other processed nanocomposites and display around 130% increase in Young's modulus while retaining significant values of toughness, tensile strength and elongation at break.     

The challenge of predicting spinnability: Investigating benefits of adding lignin to cellulose solutions in air-gap spinning

In this study, the underlying mechanism for improved spinnability when mixing lignin and cellulose in solution was investigated. Co-processing of lignin and cellulose has previously been identified as a potential route for production of inexpensive and bio-based carbon fibers. The molecular order of cellulose contributes to the strength of the fibers and the high carbon content of lignin improves the yield during conversion to carbon fibers. The current work presents an additional benefit of combining lignin and cellulose; solutions that contain both lignin and cellulose could be air-gap spun at substantially higher draw ratios than pure cellulose solutions, that is, lignin improved the spinnability. Fibers were spun from solutions containing different ratios of lignin, from 0 to 70 wt%, and the critical draw ratio was determined at various temperatures of solution. The observations were followed by characterization of the solutions with shear and elongational viscosity and surface tension, but none of these methods could explain the beneficial effect of lignin on the spinnability. However, by measuring the take-up force it was found that lignin seems to stabilize against diameter fluctuations during spinning, and plausible explanations are discussed.     

纤维增强复合材料与现代基础设施建设

高性能纤维增强复合材料(Advanced Fiber Reinforced Polymer,简称FRP)应用于基础设施建设中是近年来国际上研究的热点,结合"八六三"项目开展了基础设施建设用高性能低成本的FRP材料及其关键应用技术的开发工作,取得了一系列成果.在材料改性研究以及产品开发方面,通过纤维混杂改性,开发出适用于不同工程要求的单一品种纤维和混杂纤维的FRP产品及配套树脂材料、配套设备机具等;在关键应用技术开发方面,根据工程需要,开发出钢结构加固技术、砌体结构加固技术、预应力加固技术、结构无损检测技术等基础设施建设中应用FRP材料的关键技术;在规范标准编制方面,主持编制国家规范标准4项,1项已获批准实施,其它3项正在按计划进行;在工程应用方面,应用自主开发的材料和技术,改造、加固工程100多项,创造了巨大的经济效益及广泛的社会效益.这些工作极大地推进了我国在基础设施建设用FRP技术领域的发展.     

PDM在制造企业中的应用

通过分析制造企业与产品有关的信息流程，详细描述了在制造企业中构建PDM的方法，并给出了一个以PDM产品IMAN为集成平台的CAD／CAPP／CAM系统集成结构及实现方案。     

精密挤压(拔制)圆角方型材等相似成形模具映射建模优化

本文针对亟待实现的挤压 (拔制 )异型材模具精密快速加工设计理论课题 ,借助于近代共形映射理论研究成果 ,求解了异型材挤压 (拔制 )模具相似成形塑性流动的数学模型 ,建立了圆角方型材精密挤压 (拔制 )模具模腔数学模型及其优化函数方程 ,建立了为实现模腔精密快速的CAD/CAM一体化的理论模型     

美国3年来钽铌进口情况述评

依据英国金属网公布的2003年、2004年、2005年第1季度美国钽铌原料和制品进口统计数据．评述了美国钽铌市场的状况,着重关注了中国向美国出口钽铌的情况。