Anti-cracking Property of EVA-modified Polypropylene Fiber-reinforced Concrete Under Thermal-cooling Cycling Curing

In order to investigate the synergistic effect of re-dispersible powder-ethylene-vinyl acetate copolymer(EVA) and polypropylene fiber on the crack resistance of concrete under thermal fatigue loading, the compressive strength, ultimate tensile strength, ultimate tensile strain and tensile modulus of elasticity were tested. In addition, ultrasonic method and scanning electron microscope analysis were used to explain the microstructure mechanism. The results show that polypropylene fiberreinforced concrete presents a better performance on crack resistance than ordinary concrete, and the synergism of EVA and polypropylene fiber can improve the anti-cracking ability of concrete further.

Experimental study of polyurea-coated fiber-reinforced cement boards under gas explosions

Five types of polyurea elastomers were synthesized by changing the isocyanate component and the mechanical properties of polyurea materials were measured. Fiber-reinforced cement boards(FRCB)strengthened by polyurea with different formulations were processed, and a series of experiments were carried out on the specimens with gas explosion devices. The results showed that the conventional mechanical properties of different types of polyureas had their own advantages. Based on the gas explosion overpressure criterion, the blast resistances of reinforced plates were quantitatively evaluated,and the best polyurea was selected to guide the formulation design. The three typical failure modes of polyurea-reinforced FRCBs were flexural, shear, and flexural-shear failure. Dynamic thermodynamics and shock wave spectral analysis revealed that the polyurea did not undergo a glass transition in the gas explosion tests but retained its elastic properties, allowing it to effectively wrap the fragments formed by the brittle substrates.

A Circular Economy Use of Post-Consumer Polypropylene Packaging for Low Thermal Conductive and Fire-Retardant Building Material Applications

Wastes from polypropylene(PP)packages are accumulating every year because it is one of the most widely consumed and short lifecycle products.This paper aims to develop low thermal conductive and fire-retardant materials from post-consumer PP(pPP)packages.Ammonium polyphosphate(APP)and hollow glass microsphere(HGM)were further added to improve the fire retardancy and thermal conductivity of pPP.The influence of APP and HGM on the mechanical and thermal properties,fire retardancy and thermal conductivity of pPP were investigated and compared with that of virgin PP(vPP).HGM was constantly added at 5 wt%while the content of APP was varied from 5 to 20 wt%.Experimental results showed that the tensile and flexural strengths were reduced with increasing APP concentrations.A morphological study confirmed the poor interfacial adhesion and debonding of each component during the applied load.Formulations containing APP less than 10 wt%did not show a satisfying fire retardancy rating due to the long self-extinguishing time.Further flame dipping and cotton ignition were observed for these formulations.With 15 and 20 wt%APP,the fire rating was significantly improved from no rating to V-0.The conductive heat transfer coefficient(k)was reduced by the presence of HGM.Based on these results,the formulation with 15 and 20 wt%could be used as a low k,fire-retardant building material.

Production and Properties of Short Jute and Short E-Glass Fiber Reinforced Polypropylene-Based Composites

Short jute fiber (2 - 3 mm) reinforced polypropylene PP-based composites (20% fiber by weight) were fabricated using compression molding and the mechanical properties were evaluated. Tensile strength (TS), tensile modulus (TM), elongation at break (Eb%), flexural strength (FS), flexural modulus (FM), impact strength (IS), and hardness of the composites were found to be 32 MPa, 850 MPa, 12%, 38 MPa, 1685 MPa, 18 kJ/m2 and 96 shore-A, respectively. Then short E-glass fiber (2 - 3 mm) reinforced PP-based composites (20% fiber by weight) were fabricated and mechanical properties were compared with short jute-based composites. Short jute-based composites showed excellent mechanical properties and comparable to short E-glass-based composites. Soil degradation test of both types of composites indi-cated that jute/PP composites significantly lost much of its mechanical properties but E-glass/PP composites retained major portion of its original integrity. Interfaces of the degraded composites were investigated by scanning electron microscopy and supported the biodegradation properties of jute/PP composites.

An investigation into the effects of lime on compressive and shear strength characteristics of fiber-reinforced clays

To meet the ever-increasing construction demands around the world during recent years,reinforcement and stabilization methods have been widely used by geotechnical engineers to improve the performances and behavior of fine-grained soils.Although lime stabilization increases the compressive strength of soils,it reduces the soil ductility at the same time.Recent research shows that random fiber inclusion modifies the brittleness of soils.In the current research,the effects of lime and polypropylene(PP)fiber additions on such characteristics as compressive and shear strengths,failure strain,secant modulus of elasticity(E50)and shear strength parameters of mixtures were investigated.Kaolinite was treated with 1%,3% and 5% lime by dry weight of soil and reinforced with 0.1% monovalent PP fibers with the length of 6 mm.Samples were prepared at optimum conditions and cured at 35℃ for 1 d,7 d and 28 d at 90% relative humidity and subsequently subjected to uniaxial and triaxial compression tests(UCT and TCT)under cell pressures of 25 kPa,50 kPa and 100 kPa.Results showed that inclusion of random PP fibers to clay-lime mixtures increases both compressive and shear strengths as well as the ductility.Lime content and curing period were found to be the most influential factors.Scanning electron microscopy(SEM)analysis showed that lime addition and the formation of cementitious compounds bind soil particles and increase soil/fiber interactions at interface,leading to enhanced shear strength.The more ductile the stabilized and reinforced composition,the less the cracks in roads and waste landfill covers.

基于改性PP成型的工控机电路板支撑架注射模设计

针对工控机电路板支撑架大型塑件的成型,选用了一种玻纤改性增强聚丙烯(PP)复合材料用于塑件的注射成型。模具结构为三板模结构,分3次开模打开。为保证塑件模腔充填均衡性、饱满性而设计了两个点浇口用于模腔的浇注。针对塑件二级子特征较多,特别是异型螺柱深筋位较多的特点,设计了多个局部镶件用于这些局部特征的成型,在提高局部成型镶件强度的同时,降低了这些成型件的加工难度。针对模腔局部位置排气难点,设置了多个透气镶件以增强排气。设置了锁扣机构、定距拉杆机构用于模具的开模闭模控制;设计了弹料机构用于流道废料的可靠脱模、定位机构以确保塑件的成型精度和模具工作寿命;3个滑块机构用于塑件侧壁直壁及直壁上侧孔的成型与脱模。模具结构形式合理,成型件便于加工且实用可靠,能为同类模具设计提供有益借鉴。

高温与冷却方式对纤维混凝土影响研究

研究了高温对玻璃-聚丙烯混杂纤维混凝土的影响,对比了不同的冷却方式对混凝土强度的影响,基于试验结果分析了高温损伤机理和纤维增强机理。研究表明:喷水冷却对混凝土强度损伤大,玻璃纤维和聚丙烯纤维混掺掺量分别为0.4%和0.1%时,能够显著提高混凝土的耐火性能,在400℃下,自然冷却时,抗压和抗折强度较基准组分别提高了15.3%和30.9%;喷水冷却时,抗压和抗折强度较基准组分别提高了21.3%和30.3%。

玻璃纤维增强聚丙烯/尼龙混杂板材的制备与性能研究

玻璃纤维增强热塑性复合材料具有重复成型、高韧性、高耐久性、可设计、环境友好及可回收利用等优势。为解决由聚丙烯树脂粘度高与尼龙树脂吸水率高引起的复合材料成型工艺与耐久性问题,本项目采用模压工艺研发并制备了玻璃纤维增强聚丙烯/尼龙混杂复合材料板材,研究了混杂模式对于板材力学性能与热性能的影响规律与机理,比较分析了水分子在混杂复合材料内的扩散行为。研究发现,单层层间交替混杂模式板材具有最高的力学性能,拉伸、弯曲和剪切强度最大提升率为132.8%、127.4%和110.4%,归因于混杂板材中两种预浸带在层间粘结-挤压作用下协同受力,材料性能充分发挥;相比之下,五层预浸带层间交替混杂模式板材存在明显薄弱界面层,削弱了板材整体协同受力作用。此外,混杂板材由于聚丙烯树脂憎水性以及逐层交替混杂模式,延缓或阻止了水分子在尼龙树脂内部的吸收和扩散行为,导致混杂板材吸水率大幅下降,这对于提升尼龙树脂基复合材料的耐久性具有重要意义。

玻纤质量分数对长玻纤增强聚丙烯水驱动弹头辅助注塑管件的影响

分别以玻纤质量分数10%,20%,30%和40%的长玻纤增强聚丙烯(LGFRPP)材料制取一系列水驱动弹头辅助注塑(W-PAIM)管件。探究了玻纤质量分数对玻纤断裂长度、纤维取向、壁厚以及耐压性的影响。结果表明,随着玻纤质量分数的增加,玻纤断裂长度在较长区间内占比降低;不同玻纤质量分数的W-PAIM制件在壁厚层的取向不同,水道层的玻纤沿流动方向取向较模壁层和中间层更好,当玻纤质量分数为10%与40%时,水道层玻纤取向度最好,玻纤质量分数为20%时,中间层取向最差,玻纤质量分数为30%时,模壁层的玻纤取向较好;随着玻纤质量分数的增加,WPAIM管件壁厚呈先增加后减小再增加的趋势;随着玻纤质量分数的增加,管件的耐压性先增加后减小最后又增加,当玻纤质量分数为20%时,耐压性最好。

PPF增强玻璃粉混凝土耐腐蚀性研究

为了研究在腐蚀环境下混凝土的力学性能变化,文章秉承废物利用的原则,以不同比例的玻璃粉取代胶凝材料,以聚丙烯纤维(Polypropylene fiber,PPF)作为增强材料,且利用5%的Na_(2)SO_(4)溶液模拟腐蚀环境,探究PPF对玻璃粉混凝土力学性能和耐腐蚀性能的增益效果。试验结果表明:当玻璃粉含量一定,混凝土的抗压、抗折强度随着聚丙烯纤维掺量的增加呈现先增大后减小的趋势,且聚丙烯纤维的掺入可以提高玻璃粉混凝土耐腐蚀性,其最优掺量为0.3%。

热氧老化对马来酸酐接枝聚丙烯的结构与性能的影响

以自制的马来酸酐接枝聚丙烯(PP-g-MAH)为研究对象,研究了PP-g-MAH对玻璃纤维增强聚丙烯材料性能的影响以及热氧老化对PP-g-MAH分子结构和性能的影响。结果表明,自制的PP-g-MAH大幅度提高了30%玻纤增强聚丙烯材料的力学性能;随着热氧老化时间的延长,PP-g-MAH的MFR不断增加,对玻璃纤维增强聚丙烯材料的力学性能的提升作用不断降低;通过凝胶色谱仪(GPC)、红外光谱(IR)和马来酸酐(MAH)接枝率测定结果的分析,热氧老化过程没有对PP分子链接枝的马来酸酐产生明显的影响,而是引起了聚丙烯分子链的断裂,造成PP-g-MAH分子量下降,导致自身力学性能下降,使得PP与玻璃纤维之间的界面强度下降,使得PP-g-MAH对玻璃纤维增强聚丙烯材料的力学性能提升作用下降。

PP复合材料的性能研究

通过添加改性碳酸钙、POE、玻璃纤维、碳纤维研究其对PP复合材料性能的影响。研究表明:随着改性CaCO3含量的逐渐增加,PP复合材料的拉伸强度和冲击强度呈先增后减的趋势,改性CaCO3添加量为2%(wt.)时,拉伸强度为23.7MPa,冲击强度为17kJ·m^(-2);随着POE添加量的增加,复合材料的拉伸强度和弯曲模量降低,冲击强度增大,当POE添加量超过17%(wt.)时,冲击强度增幅减缓,综合力学性能及经济性,确定POE的添加量为17%~20%(wt.);添加玻璃纤维后,复合材料的拉伸强度、弯曲模量是增加的,冲击强度明显下降,但当玻璃纤维添加量为10%(wt.)以上,复合材料的拉伸强度和弯曲模量是逐渐增大的,冲击强度明显下降。通过复合材料冲击断面SEM表征发现:断面粗糙,有较多的片状结构,部分可见明显的“拉丝”形态,是典型的韧性断裂特征;玻璃纤维和碳纤维集束在树脂基体中随机取向分布,形成了足够的骨架网络,起到增强增韧作用。

基于FDM的PP/GF 3D打印材料性能研究

以玻璃纤维(GF)、聚丙烯(PP)、尼龙6(PA6)等为原料,制备了PP/GF复合材料,采用自主开发的工业级熔融沉积成型(FDM)设备制备了PP/GF复合材料打印件(PP/GF打印件),研究了GF种类、PA6和乙撑双硬脂酸酰胺(EBS)用量、打印件形状特征对PP/GF打印件拉伸性能和弯曲性能的影响。结果表明:与连续GF相比,加入短切GF的PP/GF打印件力学性能更好。当PA6的质量分数为10.0%时,PP/GF打印件的拉伸强度和弯曲强度比未加入PA6的PP/GF打印件分别提高了32.76%和24.32%。加入EBS可以改善PP/GF复合材料的表面粗糙度以及打印过程中挤出量的稳定性,但对PP/GF打印件的力学性能不利。当PP/GF打印件的截面边长和打印速率不变时,其拉伸强度和弯曲强度均随截面边数增多而降低。

氟改性硅溶胶的制备及性能

[目的]具有特殊润湿性的透明疏水材料在自清洁、金属防腐、微流体运输、防结冰、油水分离等领域具有广阔的应用前景。[方法]以正硅酸乙酯(TEOS)作为前驱体,十七氟硅烷偶联剂(FAS)和环氧硅烷偶联剂(KH560)为改性剂,采用两步法制备了氟改性硅溶胶,并将其涂覆在载玻片和聚丙烯(PP)纤维织物表面,制成了疏水材料。采用接触角测量仪、傅里叶变换红外光谱仪和扫描电镜对其进行表征,考察了改性剂的用量、水解时乙醇的比例及稀释倍数对材料疏水性能的影响。[结果]在乙醇与水的质量比为3∶2,偶联剂总用量为3%(质量分数),FAS与KH560的质量比为1∶1的条件下制备的硅溶胶稀释10倍后可以在载玻片和织物表面形成致密的涂层,它们对水的接触角分别达到了112°和153°,且具有优异的自清洁性能。[结论]通过溶胶-凝胶法,利用TEOS与FAS共水解的方式,可以获得性能优异的疏水材料。

甲基纤维素对PP/EVA/GF浮纤现象及性能的影响

将甲基纤维素(MC)填充于聚丙烯/乙烯-醋酸乙烯酯共聚物/玻璃纤维(PP/EVA/GF)复合体系制备了PP/EVA/GF/MC。研究了MC对PP/EVA/GF的力学性能、微观结构、结晶性能和流动性能的影响。结果表明,在MC用量2份的情况下,PP/EVA/GF/MC表现出优异的力学性能,其拉伸强度为20.20 MPa,弯曲强度为38.79 MPa,分别比PP/EVA/GF提高了12.97%和56.28%。加入MC能有效改善PP/EVA/GF的浮纤现象,制品表面玻纤数目明显减少。PP/EVA/GF/MC结晶度为35.72%,比PP/EVA/GF结晶度提高了4.97%。剪切速率低于100 s^(-1)时,PP/EVA/GF/MC黏度低于PP/EVA/GF,表明MC能提升PP/EVA/GF的流动性。

汽车用聚丙烯轻量化设计与制备

以不同种偶联剂对空心玻璃微珠(HGB)表面进行改性并与聚丙烯(PP)进行混合,制备不同比例PP/HGB复合材料。通过扫描电子显微镜(SEM)、傅里叶红外光谱(FTIR)表征复合材料的形貌与结构,证明了HGB成功被偶联剂修饰;利用密度测试仪、万能试验机测试复合材料的密度及力学性能。研究结果表明,经过不同偶联剂改性HGB后,其与PP的相容性都有所改善;其中,通过KH550改性复合材料改善最为明显。加入含KH550改性HGB的复合材料大幅度降低了PP的密度并提高了复合材料的力学性能。当加入5%KH550改性的HGB后,复合材料的密度达到了0.906 g/cm 3;冲击强度为30.5 MPa,相比于纯PP上升了了64.6%,断裂伸长率和冲击强度有着相同的趋势,达到最大值58.9%,相比于纯PP增加了89%;拉伸强度相比于纯PP上升了4.6%,弯曲强度上升了14.67%。

Assessment of fracture process in forta and polypropylene fiber-reinforced concrete using experimental analysis and digital image correlation

This paper aims to characterize the evolution of the fracture process and the cracking behavior in fortaferro(FF)and polypropylene(PP)fiber-reinforced concrete under the uniaxial compressive loading using experimental analysis and digital image correlation(DIC)on the surface displacement.For this purpose,6 mix designs,including two FF volume fractions of 0.10%,and 0.20%and three PP volume fractions of 0.20%,0.30%,and 0.40%,in addition to a control mix were evaluated according to compressive strength,modulus of elasticity,toughness index,and stress–strain curves.The influence of fibers on the microstructural texture of specimens was analyzed by scanning electron microscope(SEM)imaging.Results show that FF fiber-reinforced concrete specimens demonstrated increased ductility and strength compared to PP fiber.DIC results revealed that the major crack and fracture appeared at the peak load of the control specimen due to brittleness and sudden gain of large lateral strain,while a gradual increase in micro-crack quantity at 75%of peak load was observed in the fiber specimens,which thenbegan to connect with each other up to the final fracture.The accuracy of the results supports DIC as a reliable alternative for the characterization of the fracture process in fiber-reinforced concrete.

Deriving Tensile Properties of Glass Fiber Reinforced Polymers (GFRP) Using Mechanics of Composite Materials

This work addresses the tensile properties of glass fiber reinforced polymers (GFRP) and investigates the different ways of estimating them without the cost associated with experimentation. This attempt is achieved through comparison between experimental results, derived in accordance with the ASTM standards, and results obtained using the mechanics of composite materials. The experimental results are also compared to results derived from work by other researchers in order to corroborate the findings regarding the correlation of tensile properties of the GFRP material and the fiber volume fraction.

纤维种类及掺量对微孔混凝土力学性能的影响研究

通过调整玻璃纤维(GF)和聚丙烯纤维(PPF)掺量,在其他材料和配比不变的情况下,以800、1200 kg/m^(3)两种表观密度的微孔混凝土为基本对象,2种纤维按0、1.0、1.5、2.0、2.5 kg/m^(3)单掺以及按1∶2、1∶1、2∶1体积比复掺,对比不同表观密度微孔混凝土力学性能的变化。结果表明:随着PPF掺量的增加,抗压强度先提高后降低,其余试验组抗压强度大体上均呈逐渐提高的趋势。表观密度800 kg/m^(3)时单掺较复掺抗压强度明显提高。随着表观密度增大至1200 kg/m^(3),复掺纤维组的强度开始优于单掺纤维组,特别是早期强度提升较明显。所有试验组的抗压强度均随表观密度的增大而提高。