Effects of aging and moisture on the dynamic viscoelastic properties of oriental lacquer (urushi) film

The effects of aging and moisture on the dynamic viscoelastic properties of three oriental lacquer films were investigated. With aging over 1000 days at room temperature, the glass‐transition temperature of the lacquer films (T_α) shifted to higher temperatures, the maximum loss tangent (tanδ_α) decreased, and the storage modulus at 20°C (E) increased. These changes were analogous irrespective of lacquers. With increasing moisture content, E decreased and tanδ increased at room temperature. Although the equilibrium moisture content of the virgin lacquer (sap) film was higher than that of the clear lacquer film, its E and tanδ were more stable with an increase of moisture content. It was speculated that the polysaccharides aggregated in the sap film did not effectively contribute to the mechanical properties of the film, while their hygroscopicity resulted in higher moisture content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2288–2294, 2002     

生漆改性研究及漆酚金属高聚物

本文综述了生漆改性研究的概况 ,总结了漆酚金属高聚物的合成方法、结构特征及其主要性能 ,提出了今后生漆改性研究的发展方向和重点内容     

Viscoelastic behavior of polymer tape in a wound roll

A viscoelastic computational model is developed that uses experimentally determined viscoelastic material properties as input and can be used to predict the behavior of a tape material in a wound roll as stresses relax over time. Experimental creep test results are used to find best‐fit creep‐compliance parameters to describe two high density data storage tape media. The two tapes used in the analysis are a developmental tape with a poly(ethylenenaphthalate) (PEN) substrate and metal particle (MP) front coat similar to linear tape open (LTO4) (referred to in this work as “Tape C”), and LTO3, a commercially available tape with a PEN substrate and MP front coat. Sets of best‐fit creep‐compliance parameters are determined for both tapes. The differences between the predicted behavior using three‐, five‐, and seven‐parameter Kelvin–Voigt models are evaluated, both for a benchmark case and in a viscoelastic wound roll model. The choice of material model is found to significantly influence the predictions of the wound roll model. The differences between different material models for the same material are on the order of the differences found between the two different materials. A material model with a higher number of creep‐compliance parameters, although more computationally expensive, produces better results, particularly over long spans of time. The relative differences between the three‐, five‐, and seven‐parameter models are shown to be qualitatively consistent for several variations in the computational model setup, allowing predictions to be made based on simple benchmarks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Improvement on properties of Chinese lacquer by polyamidoamine

In this study, polyamidoamine (PAMAM) was added to raw lacquer in different proportions, and the curing process and properties of lacquer film were investigated by using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). To investigate the cross-linking state between PAMAM and urushiol, NMR was used in this study. The experiments revealed that the comprehensive mechanical properties of modified-film, especially the impact strength, were significantly improved. In addition, the touch-free drying time of lacquer film decreased, and its alkali resistance was improved due to the cross-linking of PAMAM and urushiol molecules.     

生漆的光氧化降解特性

本文综述了生漆的光氧化降解特性、光氧化降解机理的研究情况,以及提高生漆抗光氧化性能的改性方法和改性机理,并提出了改进生漆耐候性能的发展方向。     

Interaction between wood and polyurethane‐alkyd lacquer resulting in a decrease in the glass transition temperature

The long‐term properties of paint and glue are of great interest to both manufacturers and users of these materials. If a good bond is achieved, the surface between the wood and the paint or glue will be less susceptible to degradation. Thus, the wood and polymer must be compatible and develop some kind of bonding force between them. A high degree of interaction between wood and commercial polyurethane‐alkyd lacquer was shown as a decrease by 10°C of the glass transition temperature (T_g) for the lacquer on wood compared to the pure lacquer. The lacquer also demonstrated good adhesion to wood at a microscale. The interaction was investigated with dynamic mechanical thermal analysis and scanning electron microscopy fractography. The reason for the decrease in Tg is probably because of the lacquer having a higher free volume when applied to the wood, most likely due to it being subjected to tensile forces developed during the drying of the lacquer. Results from investigations of wood impregnated with two different acrylates, a polymethylmethacrylate and a more hydrophilic acrylate, support the suggestion that a decrease in T_g will occur if the polymer adheres to wood, but that poor interaction with little or no adhesion will result in no decrease in T_g. This article also presents results of the dynamic mechanical behavior of Scots Pine in the tangential direction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 595–605, 2002     

Viscoelastic properties of suspensions with weakly interacting particles

Rheological characterization of a model suspension containing hydroxyl-terminated polybutadiene and glass beads with filler concentration up to 30% by volume was performed by using a Haake parallel disk rheometer. The rheological tests conducted were the measurement of the storage modulus, G′, loss modulus, G′, and complex viscosity, η*, as functions of the frequency and the steady shear viscosity as a function of the shear rate. The linear viscoelastic region was determined to extend up to 50% strain by measuring G′, G′, and η* as functions of strain amplitude. By using multiple gap separations between the disks, it was found that the suspension did not exhibit slip at the walls of the rheometer. G′ and G′ were used to determine the relaxation times distribution, G_i(λ_i, ⊘) as functions of the relaxation time, λ_i, and the filler content, ⊘. The relaxation moduli, G_i(λ_i, ⊘), decreased with the relaxation time, but increased with the filler content. The Cox–Merz rule was also observed to be valid for these suspensions. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 507–514, 1998     

中国生漆文明的起源

漆器和生漆技术是中国独特的发明,有着7000年不间断的文明史,是"地地道道从中国传过去的整个化学最重要的根源之一。生漆是从漆树皮层采集的天然树脂,具有神奇的变色现象和惊人的黏结力,自然固化后又能形成光亮的黑色物质。远古的人类在同大自然的抗争中,学会了生存技巧,增长了智力,发展了谋生手段,掌握了生漆的特性,积淀了生漆的知识,并利用生漆用于制器、装饰和记事表意,美化生活,记录文字,成为贵族阶层财富和地位的象征物。随着技术进步,生漆技术逐渐演化成为一种成熟的、高级的营造工艺和极致的艺术形态,孕育出了髹漆工艺体系和生漆文明,成为人类永远的财富。探究人类对髹漆器物的最初需求以及与之相应的髹漆工艺的发生和进化轨迹,能使我们更加深刻地理解生漆与人类源远流长的文化关系以及人类与环境的关系。     

Viscoelastic properties of lupin proteins produced by ultrafiltration-diafiltration

The linear and nonlinear rheological properties of defatted lupin proteins produced by ultrafiltration-diafiltration were investigated. Five concentrations ranging from 10 to 30% of the defatted ultrafiltered-diafiltered (DUD) lupin proteins were prepared. The viscoelastic properties strongly depended on concentrations. Below 12%, the DUD lupin proteins exhibited more fluid-like behavior. At 15%, lupin proteins became more viscoelastic, and above 20%, the viscoelastic solid-like properties became stronger. Below 12%, the high-frequency behaviors of moduli were proportional to ω^1/2, as expected for a semiflexible coil. Above 20%, the high-frequency behaviors of moduli were proportional to ω^1/2, indicating a flexible coil. The nonlinear steady shear rheological properties were also concentration-dependent and showed shear-thinning behavior, which could be described by a power law constitutive model. The trend of the power law exponent shift is very consistent with the linear viscoelastic behavior change with the lupin protein concentration. These results suggest DUD lupin proteins undergo a structural change between 12 and 20%.     

四氯化钛在天然生漆膜表面的化学修饰

通过四氯化钛和生漆膜的化学反应,在天然生漆膜表面形成一层修饰层。用红外光谱、X-射线能量色散光谱和扫描电子显微镜等,对该修饰层进行测试表征。结果表明漆膜易与四氯化钛发生化学反应并生成漆酚钛聚合物,反应后金属氧化物含量达10.76%,X-射线能量色散光谱(EDS)分析证明,反应主要在漆膜表面进行。     

Viscoelastic behavior of Cytec FM73 adhesive during cure

In this work, the viscoelastic properties of Cytec FM73 structural film adhesive were characterized. Several resin plates were cured using various process cycles to achieve a range of final cure states. Specimens cut from these plates were tested using a dynamic mechanical analyzer (DMA) and the glass‐transition temperature at each degree of cure was determined. Stress relaxation tests at different temperatures were then performed using DMA in stress relaxation mode and time‐temperature superposition was used to generate master stress relaxation curves and associated shift functions for each degree of cure. Several different constitutive models were examined for their ability to describe relaxation modulus development during cure. A simple three‐parameter model consisting of a stretched exponential with cure‐dependent terms was found to provide the best results. The results indicate that of the parameters used in the model, relaxation time strongly depends on cure state. The empirical DiBenedetto equation was used to obtain an expression for glass‐transition temperature as a function of degree of cure. This expression was in turn used to derive a new relation to describe stress relaxation time as a function of degree of cure. The shift function was modeled using a simplified form of the Vogel equation with cure‐dependent coefficients. Good correlation between measured relaxation modulus and model predictions was observed. © 2003 Wiley Periodicals, J Appl Polym Sci 91: 2548–2557, 2004     

氢氧化钠对生漆膜腐蚀行为的研究

本文用氢氧化钠水溶液对天然生漆漆膜进行腐蚀,并用红外分析、元素分析、热重分析和扫描电镜分析等手段来研究漆膜的腐蚀机理。结果表明,漆膜在氢氧化钠水溶液腐蚀下,漆膜的酚羟基氧化生成醌、侧链不饱和键生成醛或酮,醚键上发生断裂,漆膜中的部分多糖和糖蛋白发生降解而流失,漆膜出现多而大的孔洞,吸水率升高,光泽度和耐热性降低。     

Viscoelastic properties and extrusion processability of poly(vinyl butyral)

Rheological properties and flow instability at capillary extrusion of a random terpolymer composed of vinyl butyral, vinyl alcohol, and vinyl acetate, that is denoted as PVB in this article, are studied. It is found that the rubbery plateau modulus is 1.3 MPa at 100°C from the oscillatory shear modulus. Furthermore, the average molecular weight between entanglement couplings M_e is found to be 2670. Because of the relatively high value of , it shows rubbery region in the wide temperature range (90°C–180°C). At the capillary extrusion, the surface instability (shark‐skin failure) appears prior to volumetric melt fracture. The onset stress of the shark‐skin failure, ca. 0.18 MPa, is similar to that of polyethylene, although PVB used in this study has narrow molecular weight distribution. Moreover, the apparent slippage is not detected, presumably due to good adhesion to the die wall. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40337.     

良渚文化的髹漆艺术

良渚文化是中国长江三角洲平原范畴内的新石器时代晚期文化,以其精湛的琢玉技术闻名于世,其实,良渚文化的髹漆工艺也很精彩,反山、瑶山、卞加山、梅堰等遗址都出土了为数不少的髹漆器物,器形多样,胎骨主要有木胎、陶胎和石胎等,以生活用器为主。髹漆彩绘和髹漆嵌玉技术是这一时期的重大创新,代表了良渚文化漆器装饰艺术的最高成就,是器物实用与审美相结合的完美体现,也是等级分化的标志之一。髹漆工艺的发展是人类审美发展、欲求膨胀、技术进步、财富增长的结果,是为贵族服务的产物,富裕的环境促使人去注意生活装饰,愉悦自己。     

Viscoelastic properties of polyelectrolyte solutions in non-entangled concentrated regions

Viscoelastic properties of non-entangled concentrated aqueous solutions of three sodium polystyrenesulfonates with low molecular weights were measured in oscillation flows. Master curves of dynamic moduli were obtained by shifting the moduli data measured at different concentrations along the frequency (ω) axis for each molecular weight. The concentration shift factor used in making the master curves composes a single line irrespective of molecular weight. Storage and loss moduli are proportional to ω² and ω, respectively, in the terminal region, while they are proportional to ω^1/2 in the transition region. All the master curves can be well represented by the modified Rouse theory using the experimental values of concentration, molecular weight and viscosity in a reference state.     

A potential biodegradable rubber—Viscoelastic properties of a soybean oil-based composite

Scientists are more and more interested in biodegradable materials owing to their environmental advantage. We investigated viscoelastic properties of a newly developed biomaterial made from epoxidized soybean oil (ESO). ESO cross-linked by triethylene glycol diamine exhibited viscoelastic solid properties. The storage modulus (G′) was 2×10⁴ Pa over four frequency decades. The phase angles were 14–18°. Stress relaxation measurements showed that there was no relaxation up to 500 s. From the plateau modulus we estimated that the M.W. of this cross-linked soybean oil was on the order of 10⁵. The composites of cross-linked ESO with three different fibers had 50 times higher elasticity (G′) than those without fiber. Phase shifts were the same as those of cross-linked oil without fibers, but the linear range of rheological properties was much narrower than that of the material without fibers. All these results indicated that this new biopolymer made from soybean oil exhibited strong viscoelastic solid properties similar to synthetic rubbers. These rheological properties implied that this biomaterial has high potential to replace some of the synthetic rubber and/or plastics.     

Dielectric characterization of relaxation and curing behavior of oriental lacquer

Dielectric analysis was used to investigate the effects of temperature and humidity on the curing behavior of oriental lacquer and to characterize the dielectric properties of the lacquer film. It was found that the oriental lacquer could not cure to its hardened state at relative humidity less than 50% in ambient temperature and that the cure time could be shortened tremendously by increasing the curing temperature. In order to study the dielectric properties of oriental lacquer film, two films were prepared at different curing temperatures. The glass transition and secondary relaxation temperatures of ordinary oriental lacquer film, room temperature cured purified lacquer, were observed at 45 and −40°C, respectively. The high temperature cured purified lacquer film showed a secondary relaxation at around −50°C. The relationship between thermodynamic properties and chemical structures was explored based on the analysis of the dielectric relaxation behavior using Cole–Cole plots and the dielectric relaxation intensity Δϵ. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1804–1810, 2000     

Viscoelastic properties and morphological characteristics of polymer‐modified bitumen blends

The state of dispersion, the viscoelastic properties and the mechanical properties (such as Young's modulus, ductibility, penetration, and Fraas breaking point) of polymer‐modified bitumen are investigated. Bitumen was modified with low‐density polyethylene from processed bags (PE_bags) and styrene‐butadiene random block copolymer (SBR). The blends were characterized by optical microscopy, dynamic mechanical thermal analysis (DMTA), and other conventional methods. Photomicrographs indicated that different morphologies were obtained; PE_bags gave dispersions with almost spherical polymer particles; whereas in the case of SBR, fibrillar domains were observed. DMTA measurements indicated significant changes of the storage and loss moduli of modified bitumen; depending on the polymer content in the bitumen matrix, these values were three to four times higher compared with neat bitumen. Blends with SBR showed a significantly increased resistance to cracking at low temperatures due to decrease of the glass transition temperature from ?14 to ?34°C. Contrary, PE_bags gave better results at higher temperatures where as a result of the increased resistance to permanent deformation the softening point of modified bitumen was shifted from 52 to 73°C. It was also investigated the influence of mixtures of PE_bags/SBR on the properties of bitumen as function of the composition and ratio between PE_bags and SBR. It was found that the best improvement in deformation resistance, permanent deformation, and cracking of bitumen was achieved with the addition of PE_bags/SBR mixture as the rubber increased the bitumen properties at low temperatures and the polyolefin at high temperatures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

黏弹性表面活性剂压裂液室内研究

优选了VES压裂液体系,最优配比为黏弹性表面活性剂VES 4%,助剂1.0%,还研究了体系的耐温、抗剪切、抗盐、破胶性能。结果显示,随着温度的升高,VES压裂液的黏度有明显的变化。不同的无机盐对VES压裂液有完全不同的影响,NH4C l具有明显的增黏作用,而KC l则有降黏作用;煤油、柴油都可使VES压裂液破胶,而且破胶后无残渣。     

中国大漆的故事

数千年来,大漆是中国人生产生活的重要组成部分,在中国文化中打下深深的烙印。本文拟从漆字的演变过程,与漆有关的姓氏、成语、地域及河流,中国大漆的特性等方面,全方位的讲述中国大漆的故事。