Enzyme-catalyzed Transesterification of Unusual Substrate: Synthesis of Acyclovir and L-ascorbic Acid (Vitamin C) Vinyl Esters

The synthesis of acyclovir and L-ascorbic acid with divinyladipate was performed with alkaline protease from Bacillus subtilis and lipase from Lipozyme (immobilized from Mucor miehei) in different anhydrous organic solvents. Two corresponding derivatives were obtained.

Lipase-catalyzed Regioselective Synthesis of Vinyl Ester Derivatives of Thiamphenicol: Novel Thiamphenicol Monomers for Preparation of Macromolecular Antibiotic

Three polymerizable vinyl thiamphenicol esters with different acyl donor carbon chain length (C4, C6, C10) were regioselectivly synthesized by Lipozyme? (immobilized from mucor miehei) in acetone at 50 oC for 12 h to give 73%, 81%, 63% yield, respectively. The products were valuable monomers for preparation of macromolecular antibiotic.

KINETIC MODELING OF ESTERIFICATION OF EPOXY RESIN IN THE PRESENCE OF TRIPHENYLPHOSPHINE FOR PRODUCING VINYL ESTER RESIN: MECHANISTIC RATE EQUATION

Due to its mechanical properties and ease of use, vinyl ester resin is enjoying increasing consideration. This resin normally is produced by reaction between epoxy resin and unsaturated carboxylic acid. In the present study, bis-phenol A based epoxy resin and methacrylic acid was used to produce vinyl ester resin. The reaction was conducted under both stoichiometric and non-stoichiometric conditions in the presence of triphenylphosphine as catalyst. The stoichiometric and non-stoichiometric experiments were conducted at 95, 100, 105 and 110℃ and at 90 and 95℃, respectively. The first order rate equation and mechanism based rate equation were examined. Parameters are evaluated by least square method. A comparison of mechanism based rate equation and experimental data show an excellent agreement. Finally, Arrhenius equation and activation energy were presented.

Effect of Strain Rate on Compression Behavior of Vinyl Ester Resin Casting

Quasi-static and high strain rate compressive experiments on vinyl ester casting were carried out by means of MTS (Material Test System) and Hopkinson bar. The behaviors of the compressed unstable and fracture of the resin casting at different strain rates were investigated.The results indicate that the response behavior of the resin casting is controlled by different mechanisms at different strain rate, and some mechanical properties of vinyl ester casting are rate-dependent: the casting are destroyed in toughness model under strain rate 3.3×10 -4～6.6×10 -3/s, while the casting are destroyed in brittleness model under strain rate 950～5800/s. The yield stress, yield strain energy density are all increased with the increasing strain rates at quasi-static as well as at high strain rates. What is interesting is that the yield strain decreased with the strain rates increasing at quasi-static while increased at high strain rates. It is considered that the casting occurred forcing high elastic deformation at high strain rates. The damage of the specimens is mainly controlled by axial stress before unstable deformation, while mainly controlled by shear stress after unstable deformation, and then developed to fracture finally. This progress is rate-dependent: the development of the cracks inside the castings increased with the strain rate increasing.

The Curing for Modified Vinyl Ester Resin by Hexamethylene Diisocyanate and Its Influence on Performances

The commercial vinyl ester resins(VER)was modified by diphenylmethane diisocyanate(MDI)to enhance its toughness,which is called MVER.Hexamethylene diisocyanate(HDI),a common curing agent for polyurethane(PU),was found to be a reactive agent for MVER and can contribute to the toughness of MVER.Based on present experiment results,the crosslinking mechanism of MVER and HDI system is very similar to that of PU.The FTIR result shows the-NCO of HDI can react with the-OH of MVER.The microstructure of material prepared by MVER and HDI was characterized by NMR,and it was revealed that the unique microstructure leads to the good performances.The different content of HDI has an influence on the microstructure,and the microstructure gradually reduces the toughness and mechanical performances of the MVER cured with increasing concentration of reactive curing agent(HDI).This feature is consistent with a maximum in toughness as a function of the additive(HDI)content,followed by a rapid deterioration in toughness at higher concentrations.The toughness exhibits the maximum at such an HDI concentration(20wt%).Therefore,the special curing agent(HDI)and reactive mode is very important to the microstructure and mechanical properties of material.Furthermore,there should be other reactions which contribute to the curing and microstructure of the material,which needs the further research.

Mechanical Properties of Submicron Glass Fiber Reinforced Vinyl Ester Composite

Vinyl ester (VE) resin inherently has intrinsic brittleness due to its high cross-link density. To improve mechanical performance, micro/nano fillers are widely used to modify this matrix. In present study, glass fiber in submicron scale at low contents was added into VE to prepare submicron composite (sMC). The impact resistance of un-notched sMC degraded with the increase of sGF content while that of notched-sMC remained the unchanged. Flexural properties of sMCs also were the same with that of neat resin. The results of Dynamic mechanical analysis (DMA) test showed the slight increase of storage modulus and the decrease of tan delta value in the case of sMC compared to those of un-filled matrix. However, the Mode I fracture toughness of sMC improved up to 26% and 61% corresponding to 0.3 and 0.6 wt% glass fiber used. The compact tension sample test suggests that there is the delay of crack propagation under tensile cyclic load in resin reinforced by submicron glass fiber. The number of failure cycle enlarged proportionally with the increment of sGF content in matrix.

Studies on interacting Blends of Acrylated Epoxy resin based Poly(Ester-Amide)s and Vinyl EsterResin

Epoxy resin based Unsaturated poly(ester-amide) resins (UPEAs) can be prepared by many methods but here these were prepared by reported method [1]. These UPEAs were then treated with acrylotl chloride to afford acrylated UPEAs resin (i.e. AUPEAs). Interacting blends of equal proportional AUPEAs and vinyl ester epoxy (VE) resin were prepared. APEAs and AUPEAs were characterized by elemental analysis, molecular weight determined by vapour pressure osmometer and by IR spectral study and by thermogravimetry. The curing of interacting blends was monitored on differential scanning calorimeter (DSC). Based on DSC data in situ glass reinforced composites of the resultant blends have been prepared and characterized for mechanical, electrical and chemical properties. Unreinforced blends were characterized by thermogravimetry (TGA).

Enzymatic Regioselective Synthesis of Vinyl Lactose Ester and Its Chemical Polymerization

Transesterification reaction of lactose with divinyladipate in pyridine catalyzed by an alkaline protease from Bacillus subtilis at 50C for 3 days gave 6-O-vinyladipoyl-lactose (yield 35%). Poly(6-O-vinyladipoyl-lactose) with Mn = 21,200, Mw = 32,900, Mw/Mn = 1.56 could be obtained by chemical polymerization. Poly(vinyl alcohol) containing lactose branch was biodegradable. After 6 days in aqueous buffer (PH 7), this alkaline protease could degrade the polymer to an Mn of ca. 2100, Mw/Mn = 2.56.

Toughening of vinyl ester resins by two-dimensional MXene nanosheets

Two-dimensional nanosheets are highly effective tougheners for vinyl ester resins.The toughening effect is related to the high specific surface area and unique two-dimensional planar structure of the nanosheets.In this study,a coupling agentγ-(2,3-epoxypropoxy)propytrimethoxysilane(Kh-560)was used to modify MXene nanosheets(M-MXene)for use in toughening vinyl ester resin.The mechanical properties,including the tensile strength,flexural strength,Young’s modulus and elongation,of neat vinyl ester resin and vinyl ester resin modified with MXene and M-MXene were investigated.The results showed that modification significantly improved the mechanical properties of the vinyl ester resin.The tensile and flexural strengths of the MXene-nanosheet-modified vinyl ester resin were 27.20%and 25.32%higher,respectively,than those of the neat vinyl ester resin.The coupling agent improved the interfacial compatibility between the MXene nanosheets and vinyl ester resin,which resulted in the tensile and flexural strengths of the M-MXene-nanosheet-modified vinyl ester resin being 52.57%and 54.60%higher,respectively,than those of the neat vinyl ester resin for a loading quantity of nanosheets of only 0.04 wt%,which is economically viable.The main mechanisms by which the nanosheets toughen the resin are crack deflection and crack pinning.

Awakening Sleeping Beauty:Vinyl Esters for Macrolactonization

Macrolactones play a critical role in pharmaceuticals and agrochemicals.Numerous efforts have been devoted to developing synthetic methods for them.We highlighted a recent progress for building macrocycles(≥12-membered)via bench-stable vinyl ester(VE)intermediates,which have been underdeveloped for half century.

Regioselective Synthesis of Polymerizable Vinyl Guaifenesin Esters Catalyzed by an Alkaline Protease of Bacillus subtilis

Three polymerizable vinyl guaifenesin esters with different acyl donor carbon chain lengths (C4,C6,C10) were regioselectivly synthesized by an alkaline protease from Bacillus subtilis in pyridine at 50C for 1, 3, 5 days respectively.

含磷POSS阻燃乙烯基酯树脂性能研究

将含磷POSS(DMPOSS)以5wt%、10wt%和15wt%的添加量添加到乙烯基酯树脂中,通过差示扫描量热仪(DSC)、热重分析(TG)、极限氧指数(LOI)、锥形量热仪和扫描电镜(SEM)测试研究了DMPOSS对乙烯基酯树脂玻璃化转变温度、热稳定性和燃烧性能的影响。DSC测试结果表明:DMPOSS的加入能够明显提升乙烯基酯树脂的玻璃化转变温度。LOI测试结果表明:添加DMPOSS改性的乙烯基酯树脂的氧指数随DMPOSS含量的增加而逐渐升高。当添加15wt%DMPOSS时,乙烯基酯树脂的氧指数达到23.8%。锥形量热仪测试结果表明:DMPOSS的加入能够有效降低乙烯基酯树脂的热释放。当添加15wt%DMPOSS时,乙烯基酯树脂的热释放速率峰值降低了44.9%,总的热释放降低了30.4%。

乙烯基树脂及其团状模塑料的耐磨性研究

本文对比了乙烯基树脂浇注体和乙烯基团状模塑料(乙烯基BMC)的力学性能、热性能和耐磨性能,结果表明,相比乙烯基树脂,乙烯基BMC材料具有优异的综合性能,其中硬度在60以上,提升了77%;弯曲强度达到160 MPa以上,提升了14%;老化前质量磨损在4~5 mg之间,体积磨损在2~3 mm 3之间,分别降低了约96%和97%;老化后质量磨损为8~30 mg,体积磨损在4~14 mm 3之间,分别降低了65%和80%以上。

典型海洋环境碳纤维增强树脂基复合材料老化规律研究

目的研究典型海洋大气环境下碳纤维增强树脂基复合材料的老化规律。方法针对一种典型舰船用碳纤维增强树脂基复合材料,在青岛、厦门和三亚海洋大气环境下开展0.5、1、1.5、2a的自然曝晒试验。基于拉伸、弯曲和剪切强度等力学性能演变数据,采用灰关联分析方法构建环境损伤因子Rr,以综合评价其性能退化情况。结合形貌与傅里叶红外光谱,分析其老化损伤机制。结果及结论海洋大气环境下,碳纤维复合材料表层树脂发生老化降解,该过程主要源于酯基的水解,水解产物有多元醇类和多元羧酸类化合物等,这导致复合材料内部纤维外露,且随时间增加和纬度降低,表面降解减薄程度增大。各地的环境损伤因子Rr表明,经青岛和厦门长周期暴露试验后,在光氧老化和湿热老化等环境“损伤效应”主导作用下,其力学性能随时间呈下降趋势;三亚恶劣海洋环境则更早地对复合材料造成老化损伤,0.5 a起力学性能即单调下降。

光固化工艺条件对乙烯基酯玻璃鳞片胶泥固化速度的影响探究

本研究以乙烯基酯树脂为基料,制备了光固化乙烯基酯玻璃鳞片胶泥。设计了光固化乙烯基酯玻璃鳞片胶泥的最佳固化条件。结果表明:引发剂种类和用量、涂膜厚度、照射光波长及照射距离均会对固化速度产生影响;当引发剂TPO添加量为1%,涂膜厚度为1000μm,照射距离为50 mm,波长为405 nm时,乙烯基酯玻璃鳞片胶泥的固化速度最快。

基于非线性热响应的玻璃纤维/乙烯基酯复合材料拉伸响应预报方法

为探究复合材料结构在火灾条件下的力学响应,建立考虑基体热解和纤维软化效应的复合材料热-拉伸响应模型,通过多维数组运算对非线性方程组进行求解,研究高温下玻璃纤维/乙烯基酯复合材料的拉伸性能变化规律、预测玻璃纤维/乙烯基酯复合材料在不同拉伸载荷和单侧热流工况下的失效时间。结果表明:建立的非线性热-拉伸性响应模型,能够有效预测乙烯基酯及玻璃纤维/乙烯基酯复合材料在单侧恒定热流下的拉伸性能。通过模型预测曲线可知,玻璃纤维/乙烯基酯复合材料拉伸强度随温度的下降主要分为两个阶段:第一阶段为其在玻璃化转变温度附近快速下降;第二阶段为材料基体完全玻璃化转变后,玻璃纤维/乙烯基酯复合材料拉伸强度的缓慢下降。另外,随着拉伸载荷的增加,玻璃纤维/乙烯基酯复合材料失效时间迅速缩短,且失效时间随拉伸载荷变化情况在不同热流密度下具有相同的趋势。在相同拉伸应力下,热流密度的下降可延长材料的失效时间。在80%室温强度的拉伸应力下,层合板在10 kW/m^(2)下的失效时间较75 kW/m^(2)延长了300 s。在10 kW/m^(2)条件下,施加拉伸应力低于50%室温强度时,层合板在长时间内不会发生失效。

苯基乙烯基低聚硅倍半氧烷的合成及乙烯基酯树脂复合物的性能

以苯基三甲氧基硅烷和甲基丙烯酰氧基丙基三甲氧基硅烷为原料,制备了苯基乙烯基低聚硅倍半氧烷(MPOSS),采用^(1)H-NMR,^(13)C-NMR,^(29)Si-NMR和MALDI-TOF-MS证明MPOSS段主体为完整的T10和T12笼型结构。将MPOSS用于乙烯基酯树脂(VER)制备了VER/MPOSS复合物,热重分析、差示扫描量热分析和力学性能测试表明,VER/MPOSS复合物的热稳定性和玻璃化转变温度随MPOSS比例增加而升高;相对于纯VER,添加20%的MPOSS后复合物的弯曲强度、弯曲模量和断裂力分别提高了203%,365%和200%,力学性能显著提升。极限氧指数、锥形量热、热重-红外等阻燃性能与机理研究表明,MPOSS促进了致密炭层的形成,阻止了有机挥发性产物的释放,降低了VER的热释放、烟释放和有毒气体释放量,增强了VER/MPOSS复合物的阻燃性能。综合认为,MPOSS同时提高了乙烯基酯树脂的力学性能、阻燃性能和综合性能。

紫外光固化复合材料综合性能分析研究

紫外光固化复合材料是一种在紫外光照射下能够迅速固化的一种新型材料,具有广泛的应用前景。该文主要对其综合性能进行分析研究。研究结果表明,该材料具有良好的光固化性、热稳定性、透明度和折射率。此外,该文还对紫外光固化复合材料的环境影响进行评估,验证该材料在生产和使用过程中对环境的影响较小,符合环保要求。

碳纤维/乙烯基酯树脂复合材料界面性能研究

采用改性上浆剂对SCF-35S-48K碳纤维上浆,分析了上浆工艺对上浆碳纤维的表面形貌和碳纤维/乙烯基酯树脂复合材料界面性能影响。复合材料的微观结构和层间剪切性能结果表明:上浆层对碳纤维起到了一定的保护作用,碳纤维表面平整、可加工性好,与树脂基体的界面黏结性好,复合材料的层间剪切强度达到68.18 MPa,比未上浆碳纤维/乙烯基酯树脂复合材料高7.56%,满足复合材料应用要求。

某企业合成树脂产线产污系数研究

结合实例对某企业乙烯基酯树脂生产线有机废气产污情况进行比对,方法包括系数法、实测法和公式法。系数法根据物料或产品产量及其产污系数计算工艺废气的VOCs产生量。实测法通过在正常工况下,对生产线废气排气筒进口进行监测获取污染物排放量数据,未检测特征污染物排放量。公式法参考美国EIIP文件,模拟化学过程,从而计算出不同污染物在投料、搅拌等不同阶段中产生的排放量。比对后,项目最终采用公式法进行产污量计算。