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.

Flame-retardant Mechanism of Magnesium Oxychloride in Epoxy Resin

Flame-retardant mechanism of magnesium oxychloride （M OC） in EP was in-vestigated by limiting oxygen index （LOI）, XRD, SEM, TG-DTG and DSC. The results show that MOC performed well as an inorganic flame-retardant in EP. When the content of MOC is 50%, the LOI of EP reaches 29.6% and mass of residual char reaches 9.6%. The flame retarde mechanism of MOC is due to the synergies of diluting, cooling, catalyzing char forming and obstructing effects.

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.

Synthesis of cation exchange resin-supported iron and magnesium oxides/hydroxides composite for nitrate removal in water

In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.

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.

螯合树脂脱除钨酸盐溶液中铜镁离子的研究

采用离子交换法,选用对铜离子和镁离子具有高选择性的CH-93螯合树脂和LSC-500螯合树脂深度脱除钨酸盐溶液中铜镁离子,探究不同因素对吸附效果的影响,并对吸附类型、吸附热力学及动力学进行分析。结果表明:在不同吸附参数下,铜镁离子的吸附率均可达到99%以上。热力学研究表明,树脂吸附铜镁离子是自发、吸热和熵增的过程。动力学研究表明,树脂吸附铜镁离子的过程符合Langmuir等温吸附模型和准二级动力学模型,液膜扩散是控速步骤。柱上离子交换结果表明,钨酸盐溶液经过12 h的CH-93/LSC-500树脂吸附后,铜镁离子含量分别从60000μg/L降低至14.6,24.4μg/L,且没有出现穿漏现象。

碱式硫酸镁水泥基树脂透光混凝土的界面黏结机理

使用碱式硫酸镁水泥(BMSC)作为基体材料,制备了树脂透光混凝土(RLTC),并利用界面剪切强度测试、超景深三维显微镜和扫描电镜(SEM)等分析了BMSC基体与树脂的界面黏结性能.结果表明:BMSC与树脂界面处裂纹较少且宽度较窄,在界面处观察到大量针状5·1·7相(5Mg(OH)_(2)·MgSO_(4)·7H_(2)O)结构,微米级5·1·7相晶须填充了BMSC基体与树脂的孔隙,增强了界面间的机械啮合作用;与使用普通硅酸盐水泥的RLTC相比,硬化后BMSC基体与树脂的界面黏结性能明显提高,其中28 d界面剪切强度提高了59.2%.

不同添加剂配比对镁合金砂型铸造用树脂砂性能的影响研究

针对镁合金砂型铸造中使用的树脂砂,探讨了混砂时加入树脂、固化剂、阻燃剂、硅烷等添加剂的配方及作用。通过测定树脂砂的可使用时间、起模时间、抗压强度等参数,分析了不同添加剂配比对树脂砂性能的影响。研究结果表明,在确保树脂砂强度的基础上,尽量减少树脂和固化剂的配比量,可减少铸件气孔缺陷,改善高温性能,提高铸件质量,降低生产成本。该研究结果可为镁合金铸件的高质量生产提供技术支持。

微胶囊化改性氢氧化镁及其在低密度聚乙烯中的阻燃性能研究

采用一步法合成了三聚氰胺树脂和脲醛树脂。分别对氢氧化镁阻燃剂进行微胶囊化改性,通过对其FT-IR、SEM、TEM、TG-DSC、XRD,以及添加至高聚物中后进行复合材料常规力学性能测试和极限氧指数(LOI)的测定,研究微胶囊化改性超细氢氧化镁的改性效果。结果表明,三聚氰胺树脂和脲醛树脂被成功包覆在氢氧化镁表面,并且改性后氢氧化镁热稳定性良好,粉体与聚合物基体之间的界面粘结性得到提高,与未改性氢氧化镁相比机械性能有较大提高,其极限氧指数较低密度聚乙烯有很大提升。其中,以反应温度70℃、包覆量15%的微胶囊化改性效果最好。

亚氨基二乙酸树脂对镍和镁离子的吸附性能研究

为解决比较复杂的镍浸出液的分离问题,研究了亚氨基二乙酸树脂对镍和镁的吸附性能,考察了亚氨基二乙酸树脂对镍和镁的吸附模型,同时考察了树脂用量、溶液pH值、镍的初始浓度、吸附时间、镍铁浓度比对树脂的吸附量及镍和铁的分离系数。结果显示:镁在D401树脂上的吸附遵循Langmuir模型和Freundlich模型,存在着单分子层吸附和双分子层吸附。镍不符合以上两个模型。溶液的初始浓度和溶液pH值是影响吸附过程的主要工艺因素,最佳工艺条件为CNi=0.5 g/L、pH=4、[Mg]/[N i]=3∶1、T=36 h。50 mL的树脂用量时吸附较多,镍对镁的分离系数明显提高。不进行酸洗、碱洗时树脂吸附较大,分离系数增大。

镁合金微弧氧化添加剂的优选

为了获得耐蚀性更优的微弧氧化膜,以NaAlO2-NaOH体系为基础氧化液,考察了EDTA、蒙脱石、阿拉伯树胶等添加剂对AZ91D镁合金微弧氧化膜层耐蚀性能的影响。在3.5%的NaCl水溶液中测定了微弧氧化处理前后镁合金样品的动电位极化曲线,利用腐蚀电阻等参数来判定膜的耐蚀性能。确定了铝酸盐体系中添加剂的最优用量为:3g/L蒙脱石,0g/LEDTA,50mL/L5%阿拉伯树胶。利用SEM,EDS和XRD等初步研究了陶瓷膜表面的微观结构及成分。结果表明:在该体系中添加最佳用量的添加剂可以得到致密的微弧氧化膜,膜层主要由MgO以及MgAl2O4组成;微弧氧化处理后的镁合金比处理前具有更好的耐蚀性能。

硼-氮阻燃剂与氢氧化镁协同阻燃环氧树脂

将硼-氮阻燃剂2,4,6-三(4-硼酸-2-噻吩)-1,3,5-三嗪(3TT-3BA)与Mg(OH)_2进行复配,然后将其添加到环氧树脂(EP)中,通过热重分析、锥形量热、极限氧指数、垂直燃烧等测试方法,研究了3TT-BA/Mg(OH)_2复配体系对EP的阻燃性能。研究发现,3TT-3BA与Mg(OH)_2具有协同阻燃作用,添加10%3TT-3BA/10%Mg(OH)_2到EP中,其极限氧指数达到了32.5%,垂直燃烧达到了UL94 V-0等级。同时,3TT-BA/Mg(OH)_2复配体系还能有效减小EP热释放速率、热释放总量和生烟总量。通过扫描电镜等手段探讨了3TT-BA/Mg(OH)_2复配体系的阻燃机理。

镁盐晶须原位复合酚醛树脂及其性能研究

采用原位复合方式制备了镁盐晶须 -酚醛树脂复合物 ,考察了镁盐晶须的分散行为 ,利用TGA和DSC研究了镁盐晶须 -酚醛树脂复合物的热稳定性和固化特性。发现原位复合方式有利于晶须在树脂中的均匀分散 ,引入晶须提高了树脂的热稳定性 ,加快了树脂的固化速率。研究表明 。

碱式碳酸镁阻燃环氧树脂的研究

研究了碱式碳酸镁[Mg(OH)2.4MgCO3.5H2O]对环氧树脂阻燃性能的影响。当碱式碳酸镁含量达到56.5%时,环氧树脂的氧指数(LOI)值达到了29.7%。通过X射线衍射(XRD)、热重分析(TG)、示差扫描量热法(DSC)和扫描电镜(SEM)研究了碱式碳酸镁的阻燃机理。结果表明,碱式碳酸镁是通过稀释、冷却以及隔离等方式协同作用而阻燃的。

海水氢氧化镁对硼的吸附及卤水降硼的研究

针对海卤水沉淀反应过程中氢氧化镁对硼化物的吸附现象以及树脂法对卤水脱硼进行了研究。研究表明,氢氧化镁对海卤水中的硼化物有很强的吸附作用,溶液的pH值对吸附过程影响明显。试验使用的脱硼树脂,对卤水中的硼化物具有良好的吸附分离作用,获得的脱硼卤水含硼浓度达到5mg/L,可满足生产低硼氧化镁的要求。

负载树脂预富集薄层树脂相分光光度法测定痕量镁

以阳离子交换树脂为载体 ,显色剂偶氮氯膦I与缔合在树脂上的Mg 络合 ,薄层树脂相分光光度法测定痕量镁。络合物最大吸收波长为 5 70nm ,表观摩尔吸光系数ε570 =2 4× 10 5,灵敏度比水相光度法提高 12 6倍。方法线性范围 0～12 μg/mL ,检出限 0 15 μg/L。对 10 μgMg 测定 6次 ,RSD =1 3 7% ,实测了二次精制盐水中镁 ,回收率 99%～ 10 0 5 %。

新型无卤膨胀/MH阻燃环氧树脂的制备及阻燃性能

通过极限氧指数(LOI)、水平垂直燃烧(UL-94)、锥形量热(cone)等方法,研究了纳米氢氧化镁(MH)添加到六(4-DOPO羟甲基苯甲酸)环三磷腈化合物(FR)、聚磷酸铵(APP)和环氧树脂(EP)后,制备的新型复合阻燃材料(FR/APP/MH/EP)的阻燃及力学性能。结果表明:在固定FR/APP比例为1/1的前提下,添加1%(质量分数)的MH时,复合阻燃材料EP2(10%FR/10%APP/1%MH/EP)的LOI值达到36.4%,其热释放速率(pk-HRR)、有效燃烧热平均值(av-EHC)、比消光面积平均值(av-SEA)、一氧化碳释放率平均值(av-CO)较纯环氧树脂(EP0)分别下降了79.8%,6.73%,47.2%,33.3%,相对于EP1(10%FR/10%APP/EP)分别下降了20.0%,69.6%,83.6%,58.6%,同时EP2的拉伸、弯曲、冲击强度较EP1也分别提高了47.6%,75.2%,196%;SEM分析表明EP2燃烧后能够形成一层均匀、致密、连续的炭层,具有良好的阻燃、抑烟、降毒效果。