Curing reaction and mechanism of phenol-formaldehyde novolac resins for foundry

In this study on the curing dynamics of phenol-formaldehyde novolac resins(PFNR) and hexamethylene tetramine(HMTA), two typical commercial PFNR were selected as examples and the curing reactions of the resins with HMTA were studied by differential scanning calorimetry(DSC). Based on the data calculated by the Kissinger equation and the Crane equation, a thermocuring dynamic model was established, from which the process conditions, activation energy, reaction kinetics equation and a f irst-order reaction of the curing reactions were derived.

Study on binder system of CO_2-cured phenol-formaldehyde resin used in foundry

A new aqueous alkaline resol phenol-formaldehyde resin has been prepared from phenol and formaldehyde using NaOH as catalyst; the optimum synthetic process has been determined. With addition of some cross-linking agents, after passing carbon dioxide gas through the resin bonded sand, high as-gassed strength and 24 h strength are achieved. The bonding bridge of the resin bonded sand fracture has been analyzed by using SEM.

Developing polydopamine modified molybdenum disulfide/epoxy resin powder coatings with enhanced anticorrosion performance and wear resistance on magnesium lithium alloys

Epoxy resin powder coating has been successfully applied on the corrosion protection of magnesium lithium alloys.However,poor wear resistance and microcracks formed during the solidification have limited it extensive application.There are limited approaches to exploit such anti-corrosion and mechanical properties of magnesium lithium alloys.Herein,the epoxy resin powder coating with polydopamine modified molybdenum disulfide(MoS_(2)@PDA-EP powder coating with 0,0.1,0.2,0.5,1.0 wt.%loading)was well prepared by melt extrusion to investigate its anticorrosion performance and wear resistance.The results revealed that the addition of MoS_(2)@PDA enhanced the adhesion strength between coatings and alloys,wear resistance and corrosion protection of the powder coatings.Among them,the optimum was obtained by 0.2 wt.%MoS_(2)@PDA-EP powder coating which could be attributed to well dispersion and efficient adhesion with coating matrix.To conclude,MoS_(2)@PDA-EP powder coating is meaningfully beneficial for the anticorrosive and wear performance improvement of magnesium lithium alloys.

Preparation of Silica Powder in Epoxy Resin Wear-Resistant Coating

Silicon powders possess good thermal stability and rub resistance and can be used as the filler of high temperature wear-resistant coating;it can possess good wettability and dispersibility in the organic polymer by surface modification of silane coupling agent. Organic silicon has good thermal stability, which can modify the frangibility and thermal stability of epoxy resin. A certain proportion of modified silica powder, curing agent and additives were dispersed to modified epoxy resin can compound wear-resistant coating. The results show that: the modification effect can be the best if the dosage of silane coupling agent is 1.5% of silicon powder. If the methyl triethoxy silane is 50 phr and modified silica powder is 200 phr, then various performances of coating tend to be the best.

Synergistic regulation of current-carrying wear performance of resin matrix carbon brush composites with tungsten copper composite powder

Resin matrix carbon brush composites(RMCBCs)are critical materials for high-powered electric tools.However,effectively improving their wear resistance and heat dissipation remains a challenge.RMCBCs prepared with flake graphite powders that were evenly loaded with tungsten copper composite powder(RMCBCs-W@Cu)exhibited a low wear rate of 1.63 mm^(3)/h,exhibiting 48.6%reduction in the wear rate relative to RCMBCs without additives(RMCBCs-0).In addition,RMCBCs-W@Cu achieved a low friction coefficient of 0.243 and low electric spark grade.These findings indicate that tungsten copper composite powders provide particle reinforcement and generate a gradation effect for the epoxy resin(i.e.,connecting phase)in RMCBCs,which weakens the wear of RMCBCs caused by fatigue under a cyclic current-carrying wear.

Reinforcement of Lignin-Based Phenol-Formaldehyde Adhesive with Nano-Crystalline Cellulose (NCC): Curing Behavior and Bonding Property of Plywood

The curing behavior of lignin-based phenol-formaldehyde (LPF) resin with different contents of nano-crystalline cellulose (NCC) was studied by differential scanning calorimetry (DSC) at different heating rates (5, 10 and 20&degC/min) and the bonding property was evaluated by the wet shear strength and wood failure of two-ply plywood panels after soaking in water (48 hours at room temperature and followed by 1-hour boiling). The test results indicated that the NCC content had little influence on the peak temperature, activation energy and the total heat of reaction of LPF resin at 5 and 10&degC/min. But at 20&degC/min, LPF0.00% (LPF resin without NCC) showed the highest total heat of reaction, while LPF0.25% (LPF resin containing 0.25% NCC content) and LPF0.50% (LPF resin containing 0.50% NCC content) gave the lowest value. The wet shear strength was affected by the NCC content to a certain extent. With regard to the results of one-way analysis of variance, the bonding quality could be improved by NCC and the optimum NCC content ranged from 0.25% to 0.50%. The wood failure was also affected by the NCC content, but the trend with respect to NCC content was not clear.

Impregnated Paper-Based Decorative Laminates Prepared from Lignin-Substituted Phenolic Resins

High Pressure Laminates(HPL)panels consist of stacks of self-gluing paper sheets soaked with phenol-formaldehyde(PF)resins.An important requirement for such PFs is that they must rapidly penetrate and saturate the paper pores.Partially substituting phenol with bio-based phenolic chemicals like lignin changes the physico-chemical properties of the resin and affects its ability to penetrate the paper.In this study,PF formulations containing different proportions of lignosulfonate and kraft lignin were used to prepare paper-based laminates.The penetration of a Kraft paper sheet was characterized by a recently introduced,new device measuring the conductivity between both sides of the paper sheet after a drop of resin was placed on the surface and allowed to penetrate the sheet.The main target value measured was the time required for a specific resin to completely penetrate the defined paper sample(“penetration time”).This penetration time generally depends on the molecular weight distribution,the flow behavior and the polarity of the resin which in turn are dependent on the manufacturing conditions of the resin.In the present study,the influences of the three process factors:(1)type of lignin material used for substitution,(2)lignin modification by phenolation and(3)degree of phenol substitution on the penetration times of various lignin-phenolic hybrid impregnation resins were studied using a complete twolevel three-factorial experimental design.Thin laminates made with the resins diluted in methanol were mechanically tested in terms of tensile and flexural strains,and their cross-sections were studied by light microscopy.

NaOH and Ba(OH)_2 Compound Catalyzed PhenolResorcinol-Formaldehyde Copolycondensation Resin Adhesive for Recombined Bamboo

In order to reduce the curing temperature, shorten the curing time of phenol-formaldehyde(PF) resin adhesive, and ensure the good water-solubility, NaOH and Ba(OH)_2 were used as compound catalysts. The influences of the adding time of Ba(OH)_2, the adding amount of NaOH, Ba(OH)_2 and resorcinol on the properties of adhesives were studied. The properties of NaOH catalyzed phenol-formaldehyde(PF) adhesive, NaOH and Ba(OH)_2 compound catalyzed PF adhesive, NaOH and Ba(OH)_2 compound catalyzed phenol-resorcinol-formaldehyde(PRF) adhesive, and the prepared recombinant bamboo with three kinds of adhesives were compared. The experimental results show that NaOH and Ba(OH)_2 compound catalyst not only shortens the curing time of PF adhesive, but also guarantees the suitable water solubility of adhesive. After copolycondensation with resorcinol, the curing time of adhesive is further shortened, the water solubility is improved obviously, and the highest bonding strength is obtained. Infrared spectrum analysis shows that the reaction activity point of NaOH and Ba(OH)_2 compound catalyzed PRF adhesive will increase, so that both the curing temperature and curing enthalpy decrease.

无光耐沾污蒙皮面漆的研制及其应用

介绍了蒙皮涂层耐沾污性的影响因素以及无光蒙皮面漆耐沾污的难点。对比了丙烯酸树脂体系无光、半光、高光漆膜的耐沾污性,并研究了氟碳树脂的添加量对无光漆膜耐沾污性的影响。结果表明:无光丙烯酸树脂体系的漆膜因消光粉添加量高,其表面粗糙度大,导致耐沾污性较差;在丙烯酸树脂体系中加入氟碳树脂,可提高无光漆膜的耐沾污性;且当丙烯酸树脂与氟碳树脂的比例接近1:1时,既能满所需的性能要求,又能降低成本。

CeO_(2)-ZrO_(2)-Al_(2)O_(3)/丙烯酸防腐涂料的制备及性能研究

为探究填充不同质量的无机填料CeO_(2)-ZrO_(2)-Al_(2)O_(3)(CZA)粉体对丙烯酸涂料防腐性能及各项力学性能的影响,采用共沉淀法经过干燥煅烧合成了CZA粉体样品,将得到的CZA粉末配以市场上常用的分散剂、消泡剂等助剂在丙烯酸树脂中充分分散,并以刮涂的处理方法在经过处理的铁板上制备不同质量分数的丙烯酸防腐涂层。采用XRD、SEM和EDS对CZA粉体样品进行物相分析,利用力学性能测试和电化学防腐性能测试对涂层附着力、硬度、粗糙度、弯折性能、耐磨性、拉伸强度、断裂伸长率、防腐性能等特性进行评估。结果表明,制备得到的CZA粉体为固溶体,呈现四面体结构,添加CZA粉末后,涂层硬度提高,由HB上升至1H,弯曲性能皆为1T,耐磨性能得到提高,附着力皆为1级。与没有添加CZA的丙烯酸防腐涂层相比,CZA增强了涂层的防腐性能,当填料添加质量分数为10%时,涂层防腐性能最佳。该丙烯酸类防腐涂料具有一定的防腐性能,能够有效防止腐蚀介质对材料的腐蚀,未来在防腐领域具有一定的应用前景。

低温固化聚酯粉末涂料的研究与应用

以热固性聚酯粉末涂料为研究对象,介绍了成膜物质中聚酯树脂和固化剂的特性及其在粉末涂料中的作用,并从制备、固化机理、改性、应用4个方面综述低温固化聚酯粉末涂料的研究进展。为改善聚酯粉末涂料出现缩孔的问题,将活性官能团丙烯酸酯引入聚酯树脂中进行表面改性,得到聚酯/丙烯酸混合型粉末涂料,并对耐候性聚酯/丙烯酸粉末涂料的耐候性及固化反应原理进行概述。为降低粉末涂料的固化温度,使其符合低温固化的发展要求,针对合成聚酯粉末涂料成膜物质的相对特性,在树脂合成过程中引入环氧型官能团作为功能单体或直接与环氧树脂混合。聚酯粉末涂料已在家具、汽车及家用电器领域得到广泛应用。未来,聚酯粉末涂料朝着节能环保、多样性和更广泛的适用性发展。

脲醛树脂包覆对片状羰基铁粉电磁吸波性能的影响

目的提高片状羰基铁粉(FCI)的吸波性能。方法采用原位聚合法制备脲醛树脂(UF)包覆片状羰基铁粉核壳复合粒子。通过透射电子显微镜(TEM)和X射线衍射仪(XRD)分别对试验前后样品的微观形貌和物相组分进行表征。采用矢量网络分析仪对处理前后片状羰基铁粉在0.5~18 GHz频率范围内的电磁参数进行测试,基于传输线理论对其反射损耗曲线进行拟合分析。结果微观形貌及X射线衍射谱结果表明,成功合成了脲醛树脂包覆片状羰基铁粉复合粒子(FCI@UF)。对测得的电磁参数进行分析,与原始片状羰基铁粉相比,包覆后铁粉介电常数和磁导率的实部、虚部均呈下降趋势,电磁波衰减能力减弱,与空气的阻抗匹配能力增强。反射损耗曲线图中,包覆后铁粉能有效吸收频带变宽(以反射损耗小于‒10 dB的带宽作为有效吸收频带),由3.15GHz变为4.38GHz,在13.84GHz时有最小反射损耗(‒20.64dB),最小反射损耗向高频移动,最小值降低率达41.38%。结论使用脲醛树脂对片状羰基铁粉进行包覆,制备了综合吸波性能更具优势的FCI@UF复合粒子,有效提高了片状羰基铁粉的吸波性能。

铁粉/碳纤维增强树脂复合材料的制备 及脆化损伤研究

将偶联剂改性纳米铁(Fe)粉与预处理后的碳纤维混合,浸润于环氧树脂基料中,经过搅拌混合制备纳米Fe粉/碳纤维增强树脂复合材料,研究了复合材料在高温老化、水浸老化环境下的脆化损伤行为。结果表明:树脂受到高温老化和水浸泡老化后会出现脆化损伤,碳纤维和纳米Fe粉加入会对该损伤有一定抑制;加入质量分数为4.0%的纳米Fe粉后,随着高温老化时间延长,碳纤维质量分数为3.0%的纳米Fe粉/碳纤维增强复合材料的拉伸强度、断裂韧性下降幅度较小,同时脆化损伤后树脂与纳米Fe粉、碳纤维仍结合紧密;碳纤维质量分数为3.0%、纳米Fe粉质量分数为4.0%的纳米Fe粉/碳纤维增强复合材料经水浸老化后,断裂韧性仍旧保持较高水平。

冷涂烯锌涂料的制备与性能研究

首先研究了不同环氧树脂(E20、E44和E51)对环氧含锌涂层基本性能的影响,其次探究了纯薄石墨烯的添加对涂层防腐蚀性和力学性能的影响,确定了锌质量分数30%涂料体系中纯薄石墨烯的最佳添加量,最后考察了膨润土、聚脲、聚酰胺钠作为防沉体系对冷涂烯锌涂料贮存稳定性的作用。通过中性盐雾试验,并结合扫描电镜、表面电阻率、剩余锌含量和力学性能测试,制备出符合T/CHTS 10105—2023标准要求的冷涂烯锌涂料。结果表明:采用环氧树脂E44所制备的涂层基本性能最佳;加入质量分数0.5%纯薄石墨烯后,涂层的力学性能均有提升,表面电阻率≤10^(6)Ω,锌粉利用率超过80%,耐中性盐雾时间可达3000 h;添加质量分数0.9%膨润土、0.6%聚脲和1%聚酰胺钠防沉体系后,冷涂烯锌涂料可在50℃下稳定贮存60 d。

碱性酚醛树脂砂表面安定性的试验研究

碱性酚醛树脂砂作为一种环保型树脂砂,在铸钢件生产上得到了广泛应用,但存在表面安定性差的问题,容易导致生产的铸钢件易发生夹砂和粘砂缺陷。为此,首先以碱性酚醛树脂砂为主要研究对象,确定达到实际生产需求的表面安定性为99%,其次筛选碱性酚醛树脂和粉末添加剂,选用了两种粉末添加剂,进行正交试验后得到的最佳工艺方案为:树脂加入量1.2%,原砂采用大林砂40/70号,氧化镁0.1%,可溶性淀粉0.1%。结果表明,相较于优化前,优化后的方案1 h强度提高至0.55 MPa,24 h强度提高至0.93 MPa,表面安定性提高至99.12%,最后进行浇注验证,与优化前相比,优化后的造型方案生产的铸钢件表面质量较好,无夹砂和粘砂缺陷。

烷氧基硅烷低聚物改性球形硅微粉及其应用

分别以自制乙烯基烷氧基硅烷低聚物、氨基烷氧基硅烷低聚物、多元烷氧基硅烷低聚物为改性剂,对液相法球形硅微粉进行表面改性,通过红外光谱、扫描电镜、粒度分布仪等表征了改性剂的结构、硅微粉微观形貌及粒径分布,并考察了改性硅微粉对环氧树脂力学性能的影响。结果表明,采用实验合成的改性剂对液相法球形硅微粉进行表面处理后,硅微粉的粒径增大且尺寸均一性提高,硅微粉颗粒间夹杂碎片杂质的情况得到改善,添加到环氧树脂体系后材料的力学性能提高。

提升水性涂料耐盐雾性能方法浅析

论证了不同材料对水性涂料耐盐雾性能有着很大影响,如丙烯酸乳胶、聚氨酯乳液、有机硅树脂、云母粉及耐盐雾助剂的使用,均可以提高产品耐盐雾性。主要研究水性涂膜在盐雾箱中1080 h的表现,确认不同材料对耐盐雾性能的提升有如何影响,在此基础来改善汽车钢板或者电泳板材料耐腐蚀性能,并在常温固化的情况下满足产品其他所需性能。

碳纤维粉改性环氧树脂基体的性能研究

研究了向692-2k环氧树脂中添加碳纤维粉的方法,以制备碳纤维粉改性的环氧树脂基体,并考察了不同掺量(质量分数0、15%、20%、2%)和尺寸(500目和1 000目,即25μm和13μm)的碳纤维粉对基体力学性能和耐热性能的影响。结果表明:不同尺寸和掺量的碳纤维粉可以显著改善环氧树脂基体的力学性能和耐热性能。未掺碳纤维粉的环氧树脂基体最大抗拉强度和最大弯曲强度分别为8、10 MPa,当加入500目(25μm)且掺量为20%的碳纤维粉时,其改性的环氧树脂具有最大抗拉强度为11 MPa,掺量为15%时具有最大弯曲强度(18 MPa),而当加入1 000目(13μm)且掺量为25%时,具有最大抗拉强度为14 MPa,掺量为20%时具有最大弯曲强度(25 MPa)。同时,在干燥烘箱120℃连续5天的加热下,500目(25μm)25%掺量的碳纤维粉改性692-2k环氧树脂有效提高了材料耐热性能,其失重率最小。

含钨粉体改性三维间隔连体织物复合材料γ射线屏蔽性能研究

核能会产生电离辐射,如X,γ射线,需采用屏蔽材料进行防护。传统的X射线和γ射线屏蔽材料存在重量大、易腐蚀、有毒和结构力学性能低等缺点,因此研制质轻、辐射性能优异、结构/功能一体化的新型复合材料是辐射防护技术发展的重要方向。根据各类含钨粉体的质量衰减系数理论计算值及密度,优选了氧化钨作为γ射线屏蔽填料,采用含钨粉体改性环氧树脂,并与玻璃纤维三维间隔连体织物复合形成具有夹层结构的纤维增强复合材料。考察了不同含量氧化钨对复合材料屏蔽60Co和137Csγ射线的能力及平压性能的影响。实验结果表明:氧化钨粉对复合材料的辐射屏蔽性能有显著的提升,提升程度与理论计算值相近;相同屏蔽率下,复合材料重量明显低于铁的重量;此外氧化钨也提高了连体织物复合材料的平压强度和平压模量。

基于网络层次分析法的废电路板树脂粉典型利用处置技术综合评价

面对产量快速增长的废电路板(WPCBs),通过机械物理等方法得到的废树脂粉若不能妥善利用处置会造成资源浪费和二次污染等一系列问题,亟须对现有WPCBs树脂粉典型利用处置技术进行综合评价。本研究运用基于网络层次分析法结合专家打分的综合评估方法,从资源、环境、经济、技术和社会五个方面构建网络层次关系,以确定其准则和指标间的联系与反馈,同时对WPCBs树脂粉三种典型利用处置技术填埋、焚烧和物理法进行优劣排序。研究结果表明,物理法以优异的环境、资源和经济准则获得最高的综合评价水平。最后以苏州某资源再生利用企业为例,应用本研究建立的评价模型对其开展在准则和指标方面的综合评价,验证了该模型的有效性,以期为WPCBs树脂粉工业化利用处置技术路线选择提供理论依据和参考。