Tannin–phenolic resins: Synthesis,characterization, and application as matrix in biobased composites reinforced with sisal fibers

A tannin–phenolic resin (40 wt% of tannin, characterized by ¹H nuclear magnetic resonance (NMR) and ¹³C NMR, Fourier transform infrared, thermogravimetry, differential scanning calorimetry) was used to prepare composites reinforced with sisal fibers (30–70 wt%). Inverse gas chromatography results showed that the sisal fibers and the tannin–phenolic thermoset have close values of the dispersive component and also have predominance of acid sites (acid character) at the surface, confirming the favoring of interaction between the sisal fibers and the tannin–phenolic matrix at the interface. The Izod impact strength increased up to 50 wt% of sisal fibers. This composite also showed high storage modulus, and the lower loss modulus, confirming its good fiber/matrix interface, also observed by SEM images. A composite with good properties was prepared from high content of raw material obtained from renewable sources (40 wt% of tannin substituted the phenol in the preparation of the matrix and 50 wt% of matrix was replaced by sisal fibers).     

Failure mechanisms in toughened epoxy resins—A review

The subject of improving the fracture toughness of brittle epoxy resins is receiving significant attention in order to improve the design strain of fiber-reinforced composites for aerospace structural applications. Various rubber-modified and particle-filled epoxy resins have been considered as candidate materials. Such modified resins have been observed to yield a ten- to thirty-fold increase in fracture toughness compared to the unmodified material. In order fully to utilize the potential of such materials, it is necessary to understand the failure mechanisms leading to the improvement in toughness. This paper provides a critical review of the existing theories that have been proposed for the various toughening mechanisms related to modified epoxy resins.     

Effect of glass fiber sizing on the cure kinetics of vinyl–ester resins

The cure characteristics of thermosetting resins are affected by the presence of reinforcements as a result of surface–resin interactions. Surface treatments and sizing can significantly affect such interactions; hence, sizing or surface treatment selection may significantly affect resin cure characteristics. This is of particular concern in the processing of composite materials, since neat resin cure characteristics often will not provide the appropriate basis for predicting the cure behavior of the composite. In this work, the effect of several commercially sized S-2 glass systems on the cure of vinyl–ester resin was investigated. Generally, a significant increase in the cure rate of the glass-modified systems is observed. Furthermore, a relationship between the surface energy characteristics of the fibers and the degree of cure acceleration is established, and possible mechanisms for the effect are discussed. It is apparent that sizing selection can significantly affect cure processes for vinyl–ester systems.     

Effect of fluid–particle-interactions on dispersing nano-particles in epoxy resins using stirred-media-mills and three-roll-mills

Fibre reinforced composites are indispensable in the field of modern lightweight structures, such as used in aerospace, automotive industry or in wind power plants. Those materials provide high weight savings and increase the efficiency of a structure significantly. Therefore, various efforts are made to continuously improve the quality of the matrix and the fibres. By embedding nano-particles into the epoxy matrix, the mechanical properties as well as the electrical and thermal characteristics can significantly be improved [1]. In most cases these nano-sized particles are produced as dry powders not as single primary particles but rather as particle collectives consisting out of several primary particles. For the application in reinforced composites the particles must be suspended in epoxy resin as separately dispersed primary particles or in a certain aggregate size. Generally, the influencing parameters to break up the aggregates in a dispersion process can be divided into the stress mechanism, the intensity and the frequency of the dispersing machine itself, the properties of the dispersed particles (e.g. the particle–particle interactions) the properties of the homogenous phase and the particle–resin-interactions. Besides the effect of the chosen dispersing machine the optimization of the dispersing process was investigated by applying modified particle surfaces and varying the fluid properties. The results show that the surface properties of the particles must fit to the epoxy resin properties and the attractive forces between the primary particles must be reduced or the stabilization improved, respectively. An indication for an improved stabilization and adjustment of the particles surface properties to the fluid properties can be obtained by measurements of the contact angle and the rheological properties. Generally, an increase of viscosity and mass fraction of the product leads to a higher energetic efficiency of the dispersion process in the stirred media mill and three-roll-mill.     

The shrinkage compensation of unsaturated polyester resins — polyvinyl acetate blends polymerization proceeds through fractal morphologies: characterization and simulation

Blends of unsaturated polyester, styrene and polyvinyl acetate are hot cured either between glass plates or under pressure in a molding simulator. The morphologies of the products are observed using microscopy and show their usual aspects. They are characterized according to fractal concepts by image processing; the influence of mixture composition, pressure and temperature is investigated. Based on the hypothesis that phase separation governs the shrinkage compensation, a computer simulation of the fissuration phenomenon is performed using the diffusion limited agregation (DLA) model. This fractal model gives realistic results, and is used to show the effect of network parameters on the fissures fractal dimensions.     

Chromatographic selectivity of rare Earth elements on iminodiacetate-type chelating resins having spacer arms of different lengths: importance of steric flexibility of functional group in a polymer chelating resin

Three types of chelating resins containing iminodiacetic acid homologues (IDA resins) with spacer arms of different lengths were prepared and examined as the column stationary phase for ion chromatography. The chromatographic retention behavior of rare earth elements (REEs) on the IDA resins was evaluated with respect to a capacity factor (k') to elucidate the selectivity profile of the resins. The k' values for a series of REEs on the IDA resins were compared with the chelate formation constants (K(ML)) of the corresponding free ligands of analogous structure. Selectivity of the chelating resins having longer spacer arms between the ligand group and the polymer matrix showed a better correlation with the corresponding monomeric ligands in solution. This trend has been attributed to the increase in steric flexibility of the ligand group by the presence of the spacer arm.     

H与He,Ne,Ar,Kr,Xe,碰撞角分布的理论研究

本文用我们计算了氢原子与惰性气体原子间的相互使用势，系统地研究了低能（０．４－５０ｍｅＶ）情况下出在０°－１８０°范围，氢原子被惰性气体原子弹性散射，角分布的计算值与查到的实验值基本一致。     

端正路线,发动群众,加强管理,提高质量

我们沈阳市真空机械二厂在上级党委的领导下,经过无产阶级文化大革命,特别是经过 批林整风和批林批孔运动,广大职工的阶级斗争和路线斗争觉悟有了很大提高。革命的大好 形势不断地促进了生产的发展。今年的计划产值是一九六八年的四倍,到三季度末已完成年计 划的82%,其他各项经济指标也都在大幅度增长。产品质量一直稳定在二等品上。但由于我 们领导班子路线觉悟不高,存在着保守思想满足于一般状况,不求进步,放松了质量。因而 在七四年连续出现成批质量事故,年末鉴定时险些将稳定的二等品滑到等外品上。这件事引起了我们极大重视,经过发动群…     

CCS,CCUS,CCRS,CMC系统集成

二氧化碳捕集—封存、生产生活中的节能减排和可再生能源的开发是实施低碳经济的三个核心举措。近年来提出的碳捕集—利用—封存和碳捕集—再利用—封存是更为积极的CO2减排应对策略。人类在未来必须要把宝贵的碳元素同时作为资源和能源载体循环利用,进行全程管理。     

特种气体贮运,应用,安全与特性：氯,氯化氢,硫化氢,六氟化硫

特种气体贮运、应用、安全与特性氯、氯化氢、硫化氢、六氟化硫梁国仑（化工部光明化工研究设计院大连１１６０３１）氯英文名称：Ｃｈｌｏｒｉｎｅ分子式：Ｃｌ２１物化性质氯是一种黄绿色、有毒、不可燃、具有氧化性的气体。分子量７０．９０６。蒸汽压（ｋＰａ）：１９...     

ICP-AES法测定超高强度钢中Mn,Si,Al,Ti,Nb,La杂质元素

介绍了采用ICP-AES测定超高强度钢中Mn,Si,Al,Ti,Nb,La的方法.研究了超高强度钢中基体元素,常见元素对六种杂质元素分析谱线的光谱干扰情况;选择了合适的分析谱线;工作曲线线性良好;根据钢中共存元素的含量范围,进行了加入回收实验和精密度、准确度实验,测量结果满足分析要求.     

芬兰,德国,美国,日本废纸回收情况

芬兰：废纸回收居全球之冠在世界纸张生产大国芬兰,废纸的回收率达61％,在世界各国名列前茅。首先,全民对废物利用有著较强的意识,对于工业和生产垃圾,例如废纸、废玻璃制品,废金属和废电池等,人们自觉地放入分门别类的垃圾桶,以便废品收购公司处理。这不仅大大提高了废品的二次利用,同时也保护了生态环境。此外,制定垃圾税法,规定如果将掺有废纸板和纸箱的垃圾倒入垃圾场,每吨垃圾将征收90芬兰马克（约合20美元）的垃圾处理费。芬兰有序的废纸回收工作大大方便了废纸再生产。德国：以立法保护废纸回收德国是实行废纸回收最早的…     

卡尺多,快,好,省修理法

游标卡尺主要用于测量制件的外尺寸和内尺寸，是机械制造业中最多，最常胜的量具。由于频繁使用，加之使用不当，量爪极易磨损，平面性和平行性超差，当两测量面合拢时，有明显的间隙或成“嗽叭口”。