改性水溶性高分子粘结剂的制备及性能的研究

动物胶粘结剂是水溶性天然高分子粘结材料,具有无毒无害、可降解等特性,但其也具有在常温下易凝聚、流动性差、型砂强度低等问题,针对这一问题需要对其进行改性处理。在碱解条件下,采用丙三醇、乙醇和糊精对动物胶进行改性处理。试验表明:在碱解过程中,水胶比为8∶5,Na OH加入量为动物胶质量的5%,在改性过程中,选择的改性剂最佳配比(质量比)为:动物胶∶丙三醇∶乙醇∶糊精=100∶10∶10∶10,改性温度为75℃、改性时间为90 min。测得其表面张力值为26.451m N/m、抗压强度达到3.30 MPa,最后通过红外光谱对改性机理进行理论分析,分析认为改性剂丙三醇、乙醇和糊精可与动物胶发生反应。结果证明丙三醇、乙醇和糊精复合改性剂可以降低动物胶表面张力,提高表面润湿性,最终使得砂型强度增大。     

铸造用有机与无机粘结剂优缺点对比与分析

正有机粘结剂技术发展方向强调使用性能的提高和完善,更加关注环保的技术指标。无机粘结剂体系还是以硅酸盐发展为主线,辅以有机物和无机盐对其进行改性的思路。铸造有机粘结剂和无机粘结剂是砂型(芯)粘结体系中两个重要种类。究其技术来源,均发展于20世纪50~60年代的欧美国家,CO2硬化水玻璃砂出现的更早。对新型粘结剂体系硬化机理探求和现有产品应用性能提高成为没有停止的工作,特别是无机     

邦尼树脂砂生产铸钢件的应用案例

正进入21世纪以来,对各种新型铸造粘结剂材料的研究和应用进展迅猛。目前,国内各大、中、小型铸钢企业逐渐采用自硬砂工艺,确切地说在造型方面,传统的石灰石砂、简易吹CO2水玻璃砂已逐渐被淘汰,取而代之的是作为以下几种主流的富有生命力的自硬砂粘结剂工艺:即酯硬化水玻璃砂工艺、碱酚醛树脂     

不同造型粘结剂对铸钢件表面质量的影响

正在砂型铸造方面,铸钢件的生产目前普遍采用水玻璃(CO2/酯硬化)、碱性酚醛树脂、呋喃树脂作为造型粘结剂。一般来说,笔者认为水玻璃粘结剂成本较低,但铸件表面质量、铸件尺寸精度,以及清理和旧砂再生等方面处于相对劣势;树脂类造型材料尽管可以弥补水玻璃的相对劣势,但在生产成本和铸件裂纹倾向方面还需要不断改善。铸件的清理是水玻璃粘结剂最为棘手的问题,耗费很多的人工和成本。然而,一些铸件生产企业在将水玻璃砂更换为碱性     

水玻璃自硬砂短流程再生设备的选用

正1.水玻璃自硬砂绿色铸造工艺水玻璃是一种硅酸钠真溶液和二氧化硅胶粒组成的多相分散的水溶液。其优点有成本低廉,资源广,操作方便无污染,应用灵活,能源省,铸件优质废品少等。但水玻璃砂有一些固有缺点,其中最主要的有:采用传统CO2硬化工艺,水玻璃本身的粘结强度未能得到充分的发挥,水玻璃加入量高(一般达7%~     

水溶性铸造粘结剂(PANa树脂)铸造性能的研究

PANa树脂是以聚丙烯酸钠水溶液为粘结剂,氢氧化钙为硬化剂,造型后吹二氧化碳气体快速硬化的铸造用水溶性树脂。本文讨论了吹气时间,粘结剂加入量、硬化剂加入量对铸型强度的影响,得出了型砂的合理配方。本文研究了提高铸型强度的途径,测定了粘结剂的主要工艺性能,以及PANa树脂砂的铸造性能。通过生产实践,产出合格铸件,证明了PANa树脂适用于铸造生产的可行性。     

快速固化脱醇型RTV-1硅酮密封胶的制备

采用α-官能团硅烷为交联剂,以α,ω-二羟基聚二甲基硅氧烷为基础聚合物,配合其他助剂制备一种快速固化脱醇型RTV-1硅酮密封胶。研究结果表明:当α-官能团硅烷交联剂质量分数为8%时,密封胶的表干时间可缩短到2 min,拉伸强度可达2.26 MPa,剪切强度为2.00 MPa,断裂伸长率为210%;未硫化胶料在胶管中于95℃烘箱中放置96 h后,胶料表干时间不变,拉伸强度和剪切强度仅分别下降0.09%和0.05%。与以甲基三甲氧基硅烷为交联剂的密封胶相比,采用α-官能团硅烷作为交联剂的密封胶不仅贮存性能好,而且密封胶在生产过程中无增稠现象,操作工艺简便。     

硅铁末新法粘结回用

过去硅铁粉末多用水泥粘结回用,用水泥作粘结剂,不仅工艺复杂,由于水泥是酸性材料,不利于控制铁水中的硫量。为克服上述缺点,我们用氧、氯化镁复合物(XMgCl_2·YMgO·ZH_2O)来粘结硅铁末。由于这些材料是碱性,有利于控制铁水中的硫量;同时还具有快干、快硬、强度高、吸     

酯硬化水玻璃自硬砂在铸造青铜合金中的应用

根据铸造镍铝青铜(Al9Ni4Fe4Mn2)合金的铸造性能,应用有机酯硬化水玻璃自硬砂取代传统的CO2硬化水玻璃砂铸型,使铸件的气源性缩孔、缩松、气孔、夹砂、结疤等缺陷大大降低,旧砂再生率明显提高,显著提高了铸件质量,降低了生产成本,同时提高了生产效率,改善了环境污染.应用有机酯硬化水玻璃自硬砂制作铸型后,水玻璃加入量为:2%～3%,仅是CO2硬化水玻璃砂中水玻璃加入量的1/3,同时铸型的强度稳定提高,使得铸型的吃砂量由300～400 mm降低为200～250 mm,从而铸型烘烤后的残留水分量显著减少,因此显著提高了铸件质量,气源性缩孔、渣孔缺陷由48.0%降低为3.5%,表面夹砂结疤缺陷由25.4%降低为4.5%.     

超细粉末硬化水玻璃砂的性能特征研究

采用课题组配置的超细复合粉末作固化剂,研究测试了超细粉末硬化水玻璃砂的性能特征,将它与目前大量采用的酯硬化水玻璃砂在性能上作了比较,并通过SEM对常温下和800℃焙烧后粉末硬化水玻璃砂样以及酯硬化水玻璃砂样的粘结桥微观结构进行了观察。试验结果表明：超细粉末硬化水玻璃砂工艺中,当水玻璃加入量占原砂质量的3%,粉末加入量占水玻璃加入量的25%时,砂样的常温强度比酯硬化水玻璃砂的强度提高约23%,残留强度降低约76%;粉末硬化水玻璃砂对水玻璃的模数敏感度不高,硬化过程中使用高模数水玻璃将显著改善水玻璃砂的溃散性和再生回用性能;粉末硬化水玻璃砂的抗湿性远远优于酯硬化水玻璃砂。     

苎麻增强环氧树脂复合材料的力学性能

分别以苎麻原麻和碱麻为增强体,KH550为偶联剂,制备了苎麻增强环氧树脂复合材料,研究了偶联剂用量和纤维含量对复合材料力学性能的影响,并对拉伸断口进行了观察。结果表明:当纤维的质量分数为50%,偶联剂用量为2%时,原麻/环氧树脂复合材料的力学性能最好,拉伸强度为172.9MPa,弯曲强度达365.4MPa;当纤维的质量分数为50%,偶联剂用量为3%时,碱麻/环氧树脂复合材料具有最好的拉伸性能,拉伸强度为117.3MPa;当纤维的质量分数为40%,偶联剂用量为3%时,碱麻/环氧树脂复合材料具有最好的弯曲性能,弯曲强度达293.2MPa。     

Fabricating hollow turbine blades using short carbon fiber-reinforced SiC composite

The development of hollow turbine blades fabricated by nickel-base superalloy is limited by its high density and low operating temperature (<1,100 °C). A new technology for fabricating hollow turbine blades of fiber-reinforced SiC composite was put forward. The chemical corrosion process of DSM Somos 19120 resin mold was investigated, and the pyrolysis of phenolic resin and the infiltration of liquid silicon were analyzed by using scanning electron microscope and X-ray diffraction. The influence of carbon fiber content on fracture strength and fracture toughness of fiber-reinforced SiC composite was investigated using the measurement of three-point flexural strength test. Results showed that stereolithography molds of photosensitive resin were corroded perfectly using KOH alcohol water solution. The porous carbon preforms were obtained after phenolic resin was pyrolyzed from 400 to 800 °C, which were then infiltrated with molten silicon to gain SiC matrix at the temperature of 1,450 °C in 1 h. The fracture strength and fracture toughness of SiC ceramic matrix were enhanced with the increase of short carbon fiber content. The maximum fracture strength and fracture toughness of samples were about 270 MPa and 5.1 MPa m^1/2, respectively. Finally, hollow turbine blades were successfully fabricated using short carbon fiber-reinforced SiC composite.     

室温快固型环氧树脂的研究

以环氧树脂E-51和T-31固化剂为主体研究了一种新型的室温快速固化环氧树脂体系。对树脂的配方、固化行为和力学性能进行了研究。结果表明：树脂体系能在30min左右固化;在清洁粘接面的抗剪强度达到15．56MPa,油面抗剪强度能达到9．85MPa;树脂固化物的抗拉强度达到36．11MPa,但冲击性能稍差。     

环氧树脂改性氰酸酯树脂的研究

研究了环氧树脂改性双酚 A型氰酸酯树脂体系的物理性能、粘度特性、反应性和贮存稳定性以及固化树脂的力学性能、耐热性、耐湿热性和介电性能     

碳化硅零件的激光选区烧结及反应烧结工艺

为了获得高密度、高性能、复杂结构的碳化硅陶瓷件,提出采用机械混合法制备含有黏结剂和乌洛托品固化剂的碳化硅复合粉体,对复合粉体进行激光选区烧结（SLS）形成陶瓷素坯,并对素坯进行气氛烧结和渗硅处理,使其与基体发生反应烧结,最终形成复杂陶瓷异形件。实验证明：若激光功率为8.0 W、扫描速率为2 000 mm/s、扫描间距为0.1 mm、单层厚度为0.15 mm,获得的 SLS 陶瓷样品密度和强度最好。对SLS试样进行合理的中温碳化和高温渗硅,所得碳化硅陶瓷烧结体的抗弯强度最高可达 81 MPa,相对密度大于86%。     

夹布酚醛树脂导向环热成型工艺研究

夹布酚醛树脂是一种抗压强度较高的导向支撑材料,在工程液压缸中广泛运用。但夹布酚醛树脂导向带在小规格液压缸的安装中存在一定的困难。通过对夹布酚醛树脂在热空气中老化后的抗压强度测试,以及在乳化液中的加热并浸泡后的抗压强度测试,确定夹布酚醛树脂的成形工艺;通过模具的设计,进行夹布酚醛树脂导向带的成型试验,使带状夹布酚醛树脂导向带成型为环状导向环,解决了小规格夹布酚醛树脂导向带在活塞杆中安装困难的问题。     

Compressive and Tensile Properties of Molybdenum Disulfide Compacts

Compact of molybdenum disulfide powder were made, without the use of a binder, over a wide range of compacting pressures and length-to-diameter ratios. Their specific gravity, hardness, and compressive and tensile properties were determined at approximately sea-level pressure and 75 F. The ultimate compressive strength and ultimate tensile strength were found to be essentially functions of specific gravity only, and the relationships are presented. The modulus of elasticity was found to be essentially the same in compression and in tension, and is also presented as a function of specific gravity.     

Measurement of mechanical and physical properties of particleboard by hybridization of kenaf with rubberwood particles

Kenaf is one of the potential raw materials available in Malaysia to use for particleboard manufacturing as an alternative solution to balance shortage of rubberwood (RW) supply. In this study, particleboard manufactured from kenaf stem (KS) and RW particle blends at different RW loading (0%, 50%, 70%, 100%) and resin levels (6%, 8%, 10%). Urea formaldehyde resin is used as a binder. The effects of RW:KS ratio and resin content on mechanical and dimensional stability properties of hybrid particleboard were determined. The results indicated that particleboards bonded with 10% resin level and 50:50 (RW:KS) had the highest strength (19.08 MPa) while particleboards made of 70:30 (RW:KS) display better stiffness (2.23 GPa). Statistical analysis using ANOVA and LSD were conducted on the obtained results. The results show that RW:KS ratio has greater influence over thickness swelling (TS) and water absorption (WA) of particleboard than the level of resin content. The relationship between internal bonding (IB) and TS of particleboards were also examined and obtained strong inverse relationship between IB and TS. Hybrid particleboards made from 70% RW and 30% KS with 10% resin content display over all good properties and comparable with 100% RW (control) samples. It concluded that kenaf stem can replace rubberwood particles up to 50% but the resin level must be kept at 10% or more because lower resin level (⩽8%) significantly decrease strength of the particleboard.     

Effect of rubber component on the performance of brake friction materials

Various composite friction materials containing 40 vol.% organic binder (phenolic resin plus styrene–butadiene–rubber (SBR)) with varying phenolic-resin/SBR ratio were prepared. The content of phenolic resin in each composite was indicated by the resin value (RV) index ranging between 0 and 100%. The composites with RVs greater than 50% form resin-based friction materials in which the primary binder is the phenolic resin. For RVs less than 50%, the composites become the rubber-based materials where the primary binder is the SBR. The analysis of mechanical properties exhibited that the conformability of the composites increases upon incorporation of SBR. The frictional analysis revealed that type of polymeric binder, i.e. resin or rubber, dominates greatly the frictional behavior of the composites. The increment of friction force and higher improvement in the frictional fade and recovery with sliding velocities are the general features of rubber-based friction materials. It was attributed to the inherent properties of rubber on the viscoelastic response at higher sliding velocities and entropic contribution on the mechanical properties at higher temperatures. The wear rate of resin-based materials and its drum temperature is lower than those of rubber-based materials. It was attributed to the strongly adhered multilayer secondary plateaus formed on the surface of resin-based materials.