Studies on the formation of intermolecular interactions and structural characterization of polyvinyl alcohol/lignin film

The intermolecular interactions of lignin with a hydrophilic polymer, poly (vinyl alcohol) (PVA), were studied using Nuclear Magnetic Resonance (NMR) and FT-IR spectroscopy of PVA/lignin blend fibres prepared by casting method. The structure of polyvinyl alcohol/lignin blended film has also been studied. The FT-IR technique indicates the formation of strong intermolecular hydrogen bonds between the hydroxyl groups of PVA and lignin. ¹H and ¹³C NMR spectra of the blend show extra peaks which confirm the formation of strong intermolecular hydrogen bonds between the hydroxyl groups of PVA and lignin. The results show that there is some specific intermolecular interaction between PVA and lignin.     

Aging of novel membranes made of PVA and cellulose nanocrystals extracted from Egyptian rice husk manufactured by compression moulding process

Novel membranes consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs) originated from Rice Husk (RH), Glutaraldehyde (GLA) and Glycerine (G) were manufactured by the compression moulding process. Rice husk is a new source to isolate pure cellulose nanocrystals via mechanical and chemical treatment. The biodegradability of the membranes has been evaluated using UV accelerated weathering as well as a soil burial test. The morphology of membranes (PVA/RH-CNCs) was characterized by using the Scanning Electron Microscope (SEM). The chemical structure of the membranes (PVA/RH-CNCs) was characterised by Fourier-Transformation Infrared (FTIR) spectroscopy as well as wide-angle X-ray diffraction. The mechanical properties of the membranes were evaluated using standard techniques. Swelling and weight loss resulting from biodegradation were also evaluated. The results showed that the developed transient membranes can be used as food packaging bags owing to biodegradability (weight loss) under irradiation and during soil burial.     

一种低模量、高断裂伸长率双组分聚氨酯密封胶的制备

在分析各物料用量对密封胶性能影响的基础上,通过配方优化调整,制备了双组分聚氨酯密封胶产品。性能测试结果表明,改进配方后的聚氨酯密封胶,拉伸强度达到2.4 MPa、断裂伸长率达到1100%、质量损失率仅3%,满足标准中低模量、高断裂伸长率密封胶的性能要求。     

聚硫密封胶的固化及其热老化性能研究

研究基膏与硫化膏的配比、促进剂二苯胍对聚硫密封胶的固化时间和力学性能的影响.结果发现,基膏与硫化膏的配比为100/12时,密封胶能完全固化;基膏与硫化膏的配比为100/8时,密封胶具有最佳的力学性能,断裂伸长率和拉伸强度分别为437%和2.65 MPa;添加二苯胍能促进密封胶的固化过程;100℃热老化7d会降低聚硫密封胶的硬度,并提高其拉伸强度和断裂伸长率.     

高分散性纳米片状氢氧化镁的制备及应用

以氯化镁为原料,氨水为沉淀剂,采用直接水热法制备了氢氧化镁阻燃剂,采用扫描电子显微镜和X射线衍射仪对其形貌和晶体结构进行了表征,同时对其在EVA中的应用进行了初步研究。结果显示,所制备的氢氧化镁产品为六方晶型,分散性高,与EVA的相容性好。氢氧化镁填充量为60%的EVA混合物的转矩流变性能和力学性能均优秀,平衡扭矩为12.7N·m,拉伸强度为10.1MPa,断裂伸长率达到1150%。     

Aging of membranes prepared from PVA and cellulose nanocrystals by use of thermal compression

Novel membranes consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs), nanosilica (NS), glutaraldehyde (GLA) and glycerine (G) were prepared using a compression moulding process. Rice husk is selected to isolate pure cellulose nanocrystals via mechanical and chemical treatment. The biodegradability of the membranes has been evaluated using UV accelerated weathering as well as a soil burial test. The chemical structure of the membranes were characterised by Fourier-Transformation Infrared (FTIR) spectroscopy. The microstructure of the membranes was characterised by using Scanning Electron Microscope (SEM). The mechanical properties of the membranes were evaluated using standard techniques. The swelling and weight loss resulting from biodegradation were also evaluated. The results showed that the developed membranes can be used as food packaging bags owing to biodegradability (weight loss) under irradiation and during soil burial. The membranes are environmentally friendly.     

乙烯基单体对聚氨酯丙烯酸酯性能的影响

分别以苯乙烯(SM)、甲基丙烯酸甲酯(MMA)、甲基丙烯酸(MA)和丙烯酸(AA)作为活性稀释剂,研究它们对聚氨酯丙烯酸酯性能的影响。结果表明,4种乙烯基单体与聚氨酯丙烯酸酯的相容性均很好,对体系稀释能力的大小顺序为MMA>SM>MA>AA。SM与MMA的反应活性相对较低,制得的样品力学性能较差。AA与MA的反应活性高,其中AA制备的样品断裂伸长率较高,柔韧性较好;MA制备的样品拉伸强度、硬度、压缩强度和压缩弹性模量较高,且随其含量增加,样品的凝胶时间、黏度和断裂伸长率降低,强度和刚度增大。在中后期(≥168 h),随着龄期增加,样品的压缩强度和压缩弹性模量增大,拉伸强度和硬度变化不大。     

聚氨酯丙烯酸酯改性聚甲基丙烯酸甲酯防水涂料的研究

以聚氨酯丙烯酸酯树脂(PUMA)为柔性链段与活性单体甲基丙烯酸甲酯进行自由基共聚反应,生成改性的聚甲基丙烯酸甲酯(PMMA)防水涂料。研究了PUMA的用量对PMMA防水涂膜性能的影响,包括固化情况、硬度、附着力、力学性能、不透水性及低温柔性等。当PUMA的用量为60%时制得的PMMA涂膜拉伸强度为16.5 MPa,断裂伸长率达130%,与混凝土粘结强度为3.5 MPa,1.8 MPa、24 h不透水,是一种性能优异的防水材料。     

Comparative experimental study of mechanical properties of concrete prepared by different fibres

This paper reports a comparative experimental study on the mechanical properties of concrete containing different types of fibres: polyvinyl alcohol (PVA), polypropylene (PP) and steel fibres. Compression and three-point bending tests are performed on both plain concrete and each type of fibre-reinforced concrete (FRC). The experimental results show that the presence of fibres has less of an effect on the FRC's compressive strength. The tensile strength is commonly increased by the addition of fibres, but an appropriate fibre content of PVA or PP fibres should be selected. PVA and PP fibres decrease the concrete's elastic modulus, but steel fibres increase the modulus due to the steel's higher Young's modulus. The FRC containing PVA shows brittle characteristics, but the FRC containing steel or PP fibres have load-deflection curves with flattened descending paths. Flexural behaviour of the concrete is improved by addition of steel or PP fibres, but not by PVA fibres, and the concrete's fracture toughness is increased by the addition of steel fibres.     

高性能再生骨料混凝土力学性能的研究

研究了不同水胶比、不同再生骨料替代率的高性能再生混凝土抗压强度、抗折强度、劈裂抗拉强度、弹性模量等力学性能.结果显示,再生混凝土的强度等级在C30～C60之间,抗折强度大于4MPa,劈裂抗拉强度大于2MPa,弹性模量在20～40GPa之间,力学性能满足应用技术要求.再生骨料替代率在60%以内时,不影响混凝土各项强度指标...     

透明环保型建筑防水涂料的研制

分别以闭端型预聚体高分子材料、丙烯酸酯乳液、乙烯-醋酸乙烯酯乳液为主要成膜物质,复配成膜助剂、抗老化剂等助剂,制成透明型防水涂料.测试表明,以闭端型预聚体高分子材料配制的透明型防水涂料拉伸强度大于20 MPa,断裂延伸率大于700％,透明性大于98％,类似普通透明玻璃,十分适合有特殊要求的建筑外墙或外围护结构的防水或防护.     

增材制造技术制备316L不锈钢的拉伸性能

选择性激光熔融技术(Selective Laser Melting, SLM)是一种常用的金属增材制造方法,在过去20多年里得到快速发展。然而,产品力学性能缺乏全面描述的问题仍然阻碍着这一技术在土木工程中进一步的发展与应用。文章分别采用两种SLM生产设备制备了两种厚度、五个方向的共48个316L不锈钢制样,通过拉伸试验获得其基本力学性能。制样的弹性模量范围为172.61～215.55 GPa,屈服强度为446.90～583.47 MPa,极限强度为576.22～734.43 MPa,延伸率为20.69%～49.56%。屈服强度和极限强度均远高于经固溶处理的316L不锈钢型钢板和钢带规范值,且均高于未退火处理的锻件水平;屈强比也远高于经固溶处理的不锈钢型钢板和钢带水平。不同设备、不同厚度和不同方向制样的力学性能表现出较为明显的差异。结合进一步的断口扫描电镜试验和已有文献结果,分析不同生产设备、不同厚度、不同方向制样的力学性能存在差异的原因及随角度变化趋势。     

石英高岭石白云母共混补强丁苯橡胶的试验研究

将石英、高岭石、白云母三者按15∶4∶1比例共混,经气流磨超细粉碎,硅烷KH570表面改性,填充丁苯橡胶。结果表明,改性后矿物微粉补强效果得到提高;填充量为60份时,复合材料的综合力学性能较高,其中抗拉强度、撕裂强度分别提高了76.7%、39.9%;矿粉粒度变细,有利于提高复合材料的最大载荷和断裂伸长率。FTIR和SEM研究表明,-5μm微粉与丁苯橡胶基体结合较好,3种矿物能发挥协同补强作用。     

白炭黑对硅橡胶性能的影响

采用电子万能试验机、极限氧指数、垂直燃烧仪、同步热分析仪和锥形量热仪等,系统研究了白炭黑添加量对硅橡胶/白炭黑复合材料的力学性能、阻燃性能、热稳定性和燃烧性能的影响。结果表明：白炭黑能显著提高复合材料的力学性能,白炭黑添加40 份时,复合材料力学性能达到最佳,其拉伸强度为9.35MPa,断裂伸长率为614.7%;白炭黑能改善复合材料的阻燃性能,白炭黑量达到50 份时,复合材料极限氧指数可达25.0%;白炭黑添加能明显提高复合材料的初始热分解温度和高温成炭率,白炭黑添加量为40 份时初始热分解温度为495.4 ℃,高温残炭率为31.4%;白炭黑的添加能有效降低复合材料的热释放速率、总热释放量、总生烟量和二氧化碳生成量,对硅橡胶有较好的阻燃抑烟作用。     

加载速率对大直径GFRP筋足尺试件抗拉性能的影响

 玻璃纤维增强聚合物(GFRP)筋是一种由玻璃纤维与树脂复合而成的新型加固材料,具有良好的应用前景。GFRP筋为非均质各向异性材料,横向抗压强度远小于轴向抗拉强度,具有显著的尺寸效应,因此,GFRP筋强度指标的测试比钢筋材料更复杂。本文试验解决大直径GFRP筋足尺试件的端部锚固问题。通过在拉力试验机上进行大直径GFRP筋足尺试件的抗拉破坏性试验,研究不同加载速率下大直径GFRP筋的抗拉强度、拉伸弹性模量、延伸率等基本力学指标的变化规律,并对比分析GFRP筋与钢筋的受力破坏机制。试验结果表明,随着加载速率的增大,大直径GFRP筋的抗拉强度、延伸率明显增大,拉伸模量的变化幅度较小,基本保持恒定;并分析得出,材料的组成结构决定材料的力学特征和破坏形式。     

木质素纤维增强干混砂浆的制备与性能表征

在普通干混砂浆中掺加木质素纤维,获得木质素纤维增强干混砂浆,对其物理力学性能、热学性能以及收缩性能等进行研究。结果表明:随着木质素纤维含量的增加,砂浆试样硬化后的物理力学性能有显著的提高,尤其是抗折强度,木质素纤维占胶凝材料质量0.26%时,28 d抗折强度增加为7.5 MPa,拉伸粘接强度增加至0.8 MPa,收缩率降低至0.07%,导热系数降低至1.41 W/(m·K),吸水率增加了0.02%。     

碳纤维布力学性能指标取值探讨

对320组碳纤维布进行拉伸试验,测定拉伸强度、弹性模量及伸长率等力学性能,并依据试验结果确定力学性能的取值,为以后的研究提供参考。     

热冲压球壳Q235钢材高温后力学性能试验研究

为研究热冲压球壳Q235钢材高温后的力学性能,对经历400~900℃高温后由自然冷却和喷水冷却到常温空心球加工制作成的受拉试样进行拉伸试验,得到高温冷却后该材料的应力-应变曲线、弹性模量、屈服强度、抗拉强度和断后伸长率,并与普通Q235钢高温后力学性能进行了对比。研究结果表明：当经历温度不超过500℃时,钢材高温后强度与断后伸长率在两种冷却方式下变化规律基本类似,且变化很小。当经历温度超过500℃后,不同冷却方式对材料高温后强度与断后伸长率产生明显影响,且温度越高,相差越大,自然冷却方式下,随着温度的升高,强度降低而断后伸长率变大。喷水冷却方式下,抗拉强度增大而伸长率减小,屈服强度在500~700℃之间逐渐增大,700℃之后又快速下降。弹性模量受经历温度与冷却方式的影响较小。     

超高强混凝土的配制及基本力学性能试验研究

结合当地情况采用常规材料及通用工艺,成功研制工作性能良好、抗压强度超过100MPa的超高强混凝土材料。研究内容包括超高强混凝土材料的配合比,超高强混凝土的抗压强度、劈裂抗拉强度、轴心抗压强度、静力弹性模量、抗弯强度等力学性能,为进一步研究超高强混凝土的力学性能规律提供依据。     

Experimental investigation of cold-formed steel material at elevated temperatures

This paper presents the mechanical properties data for cold-formed steel at elevated temperatures. The deterioration of the mechanical properties of yield strength (0.2% proof stress) and elastic modulus are the primary properties in the design and analysis of cold-formed steel structures under fire. However, values of these properties at different temperatures are not well reported. Therefore, both steady and transient tensile coupon tests were conducted at different temperatures ranged approximately from 20 to 1000 °C for obtaining the mechanical properties of cold-formed steel structural material. This study included cold-formed steel grades G550 and G450 with plate thickness of 1.0 and 1.9 mm, respectively. Curves of elastic modulus, yield strength obtained at different strain levels, ultimate strength, ultimate strain and thermal elongation versus different temperatures are plotted and compared with the results obtained from the Australian, British, European standards and the test results predicted by other researchers. A unified equation for yield strength, elastic modulus, ultimate strength and ultimate strain of cold-formed steel at elevated temperatures is proposed in this paper. A full strain range expression up to the ultimate tensile strain for the stress–strain curves of cold-formed carbon steel at elevated temperatures is also proposed in this paper. It is shown that the proposed equation accurately predicted the test results.