Development of cellulose nanofibrils reinforced polyvinyl alcohol films incorporated with alizarin for intelligent food packaging

Visual pH-sensing films were fabricated using cellulose nanofibrils (CNF) reinforced polyvinyl alcohol (PVA) and alizarin. The relationships between the ratio of PVA: CNF hydrogel (2:1, 1:1, 1:2) and the physical properties and colour response efficiency of indicator films were investigated. Fourier transform infrared spectroscopy of films evidenced alizarin and CNF was properly incorporated by physical interaction. A new weak X-ray diffraction peak appeared at 2θ = 22.4°, which was affected by the incorporation of CNF. The increase in the CNF content induced enhancements of thermal stability, tensile strength, water contact angle and colour sensitivity of the indicator films. The colourimetric films had a higher sensitivity to discolouration when exposed to acidic vapours than alkaline vapours. The films presented a remarkable colour change varied from purple in alkaline condition to yellow in acidic condition. Therefore, this colourimetric film can be used as a volatile acid sensor for intelligent packaging.     

抑菌纸对吐司保鲜作用

研究了抑菌纸对吐司保鲜作用的影响。将抑菌纸与PP薄薄膜结合得到纸塑复合材料来包装吐司，与单一的PP薄膜包装以及未采取包装的吐司对比质构、色差、水分活度、菌落总数、热焓值的差异。结果表明：采用纸塑复合材料包装的吐司相较于仅用PP薄膜包装以及未采取包装的吐司，其质构特性和色差的劣变变缓，水分活度有一定程度降低，菌落总数的增长得到有效抑制，热焓值的上升也得到延缓。该抑菌纸与PP薄膜结合得到的复合材料可避免直接向食品中添加防腐剂，并且能有效延长吐司的货架期。     

Fabrication of porous titania sheet via tape casting: Microstructure and water permeability study

In this article, we report the effects of slurry formulation and sintering conditions on the microstructure and permeability of porous titania sheets prepared by tape casting. It was found that solid concentration and binder content in the titania slurry play a vital role in the porosity and microstructure of the sintered titania sheets. Solid concentration and binder content were optimized based on the green tape quality and open porosity of the sintered titania sheets. The optimum solid concentration with the lowest surface roughness was obtained at 0.61 g/cm³. The effects of temperature and sintering time on the open porosity and crystal structure of the final product were also investigated. Increasing the sintering temperature from 1000 to 1100 °C resulted in increasing the pore size from 170 to 264 nm and decreasing the open porosity. Finally, water permeability of the porous titania sheets was studied to evaluate the permeation flux and maximum operating pressure. The results revealed that the permeability of the porous titania sheet is increased not only by increasing the open porosity but also by increasing the pore size.     

Electrical Breakdown Properties and Space Charge Formation in High Temperature Region in Ultraviolet Ray Irradiated PVC

Polyvinyl chloride (PVC) is the most popular insulating material for electric wiring instruments. However, an exothermic reaction above 150 °C may cause deterioration of the insulating properties of PVC. Therefore, it is important to clarify the heat degradation in PVC, not only to investigate the ignition of electrical wiring products but also to use electrical products safely. It is known that ultraviolet (UV) irradiation causes chemical deterioration of PVC and an increase in its conductivity. Generally, it has been thought that the electrical breakdown properties, electrical conduction, and insulating performance are affected by space charge accumulation in an insulating material. A high temperature pulsed electroacoustic (PEA) system usable up to 250 °C has been developed, and the PEA system can measure the space charge distribution and conduction current in the high temperature range simultaneously. In this investigation, the space charge distribution and conduction current were measured up to electrical breakdown in a non‐UV irradiated sample (normal PVC) and in 353 nm and 253 nm UV‐irradiated PVC samples in the range from room temperature to 200 °C in a DC electric field. In the short wavelength UV irradiated PVC sample (253 nm, 300 h), a deterioration of breakdown strength at 90 °C to 150 °C and negative packet‐like charges were observed at 60 °C and 100 °C, a positive charge accumulated in front of both the anode and cathode above 90 °C, and a higher electric field near the cathode side because the positive charge of the cathode side was greater.     

变性淀粉/聚乙烯醇复合膜的研究进展

随着环保意识的日益增强,人们对绿色可降解包装材料的需求量逐渐增大。变性淀粉/聚乙烯醇(PVA)复合膜因良好的生物降解特性而显现出巨大优势。介绍了聚乙烯醇薄膜的性能和改性方法,国内外变性淀粉/聚乙烯醇复合膜的相关研究进展,以及我国目前研究中面临的问题。变性淀粉/聚乙烯醇复合膜不仅可用作包装膜,在抗菌防腐、抗紫外线和保鲜检测方面也展现出不俗的潜力,有望得到广泛应用。     

蓝藻基生物降解共混膜的力学性能

以聚乙烯醇(PVA)和水华蓝藻为主要原料,通过溶液铺膜法制备了蓝藻/PVA共混膜,采用万能试验机,研究了不同助剂对蓝藻/PVA共混膜力学性能的影响。结果表明,蓝藻的添加显著降低了共混膜的力学性能。当添加比例为PVA的1/2时,膜的拉伸强度和断裂伸长率分别比无藻处理下降了65.89%和79.57%。甘油、尿素显著提升了蓝藻/PVA共混膜的断裂伸长率,当添加比例为蓝藻的1/2时,分别能使共混膜的断裂伸长率提高73.20倍和62.02倍。虽然柠檬酸、硅烷偶联剂能够提升蓝藻/PVA共混膜的拉伸强度,但只能在低剂量时促进断裂伸长率的小幅提高,当柠檬酸添加比例为蓝藻的1/40时,膜的断裂伸长率能提高4.41倍,而当硅烷偶联剂添加比例为蓝藻的1/20时,膜的断裂伸长率能提高1.49倍。尿素与甘油复合增塑,更有利于提升共混膜的断裂伸长率。硅烷偶联剂与甘油复合增塑,更有利于提升共混膜的拉伸强度。     

聚乙烯醇对过氧化银电极分解和电性能的影响

采用不同浓度的聚乙烯醇(PVA)溶液对过氧化银(Ag O)电极进行浸渍处理。采用示差扫描量热法(DSC)、扫描电子显微镜(SEM)、化学分析和单片放电对电极进行表征和电性能测试。结果表明,经浓度为1.0%的PVA溶液处理后,电极性能远远优于未处理的过氧化银电极,表现在过氧化银分解表观活化能为143.91 k J/mol,70 o C高温贮存后Ag O分解率仅为0.9%,放电容量衰减仅为18.4%。     

Preparation of a modified crosslinked chitosan/polyvinyl alcohol blended affinity membrane for purification of His-tagged protein

Based on a crosslinked chitosan (CS)/polyvinyl alcohol (PVA) matrix membrane, an immobilized metal ion affinity membrane (IMAM) using Cu²⁺ and Ni²⁺ ions as affinity ligands was prepared for purification of the His-tagged recombinant protein. The affinity membrane possessed a favorable membrane structure including 1.39 μm average pore size and 0.33 mL·cm⁻²·s⁻¹ water flux under 0.08 MPa pressure at 25 °C. The Cu²⁺ and Ni²⁺ ions capacities immobilized on the IMAM were 155.6 and 137.3 μmol·disk⁻¹, respectively. The IMAM had an excellent specific affinity to His-tagged protein. About 10-fold purification factor for the model protein was obtained in a batch adsorption, and serine hydroxymethyl transferase could be purified to a single band in sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis from its crude extract solution with an affinity membrane cartridge by a dynamic purification process. This work provides a promising IMAM for the purification of His-tagged recombinant proteins. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47347.     

助剂对聚醋酸乙烯酯乳液涂料对比率的影响

研究分析了聚醋酸乙烯酯(PVAc)乳液涂料中,各功能助剂(纤维素、丙二醇、聚丙烯酸钠盐、十二碳醇酯)对涂料对比率的影响。通过对实验数据的分析比较,得到结论:增稠剂纤维素用量增加对涂料对比率无明显影响;分散剂聚丙烯酸钠盐用量增加到6g时涂料对比率最高;聚结剂十二碳醇酯用量增加使对比率呈上升趋势;成膜助剂丙二醇质量的增加使涂料对比率呈无规律变化。     

Hydroxyl Group Separation Distances in Anti-Freeze Compounds and Their Effects on Ice Nucleation

Since the discovery of biological antifreeze glycoproteins (AFGPs), which can inhibit ice nucleation, there has been considerable interest in understanding their mechanisms and mimicking them in synthetic polymers. In this study, we used molecular dynamics simulations of modified polyvinyl alcohol (PVA) compounds to show that the hydroxyl (OH) group distance is a key factor in whether certain compounds promote or inhibit ice nucleation. A hydroxyl distance smaller than ~2.8 Å but greater than ~7.1 Å in modified PVA (MPVA) compounds was associated with the promotion of ice nucleation, while a hydroxyl group separation distance of approximately ~5.0 Å was correlated with a delay in ice nucleation, owing to changes in the energy of the system. Thus, these results may help explain some of the mechanisms of current known anti-freeze compounds and may have implications for designing new anti-freeze compounds in the future.