2011年硕士毕业生
发布人： 发布时间: 2014-02-27 作者: admin 访问次数: 125

 

论文题目：官能化SEBS增韧尼龙6/蒙脱土纳米复合材料的制备与性能研究
毕业学生：何三雄
指导老师：吴唯教授
中文摘要：
       本论文选用了热塑性弹性体苯乙烯-乙烯-丁二烯-苯乙烯嵌段共聚物（SEBS），并将其分别进行接枝甲基丙烯酸缩水甘油酯（GMA）和马来酸酐（MAH），得到2种官能化接枝物SEBS-g-GMA和SEBS-g-MAH。然后，用官能化SEBS、以及官能化SEBS与聚碳酸酯（PC）协同对PA6进行增韧，同时以纳米有机蒙脱土（OMMT）为填料对PA6进行补强， GMA或环氧树脂（EP）为相容剂，制备了综合性能优异的高韧性工程塑料。采用XRD、SEM、TGA、DSC、FTIR、Molau实验、力学性能测试以及流变性能测试等多种测试手段，研究了官能化基团种类及接枝率、填料和相容剂的用量、以及各组分间的微交联反应体系对纳米复合材料形态、结构和性能的影响。
        首先将PA6与国内工业化生产的OMMT进行熔融共混，制备了PA6/OMMT纳米复合材料。通过力学性能测试发现，当OMMT含量为4wt%时，复合材料具有较高的强度和弯曲模量，但冲击强度较纯PA6有所降低。对复合材料进行小角X射线衍射扫描以及透射电镜观察，发现OMMT已经被PA6剥离，较均匀地分散在基体中。Molau实验结果表明OMMT以胶体形式均匀地分散在甲酸溶液中，不沉降、不分相。
        分别以GMA和MAH为功能单体，熔融挤出制备了官能化弹性体SEBS-g-GMA和SEBS-g-MAH，用滴定分析测定了两种接枝物的接枝率，分别为2.39%和1.2%。再分别以SEBS-g-GMA和SEBS-MAH为增韧剂、OMMT为填料，制备了尼龙6/弹性体/蒙脱土三元纳米复合材料。研究了三元纳米复合材料的力学性能、结晶性能和热稳定性以及分散相在基体中的分散状态。结果表明，三元纳米复合材料的性能介于尼龙6、尼龙6/弹性体之间，弹性体使得PA6/OMMT纳米复合材料的冲击强度提高。当弹性体含量达到约30%时，三元纳米复合材料发生脆-韧转变，在进行缺口冲击强度测试时试样已经不能完全断裂，冲击韧性大幅提高。同时复合材料的强度仍保持在纯PA6的90%以上，材料的硬度与韧性达到较好地平衡。
        将SEBS-g-GMA和SEBS-g-MAH对PA6复合材料的增韧效果作比较后发现，不同的接枝物导致了分散相在基体中有不同的分散状态。由于熔融加工过程中SEBS-g-GMA与基体PA6之间会发生交联反应，组成、加工条件相同情况下SEBS-g-GMA的粒径远大于SEBS-g-MAH的粒径，其增韧的效果要差。少量的OMMT可以起到阻止分散相相互黏结作用，使得分散相粒子尺寸减小；较多量的OMMT又能阻碍官能化弹性体与PA6基体间的界面黏结，导致分散相粒子尺寸增大，降低了材料的冲击性能。用SEBS-g-GMA增韧制备的PA6/SEBS-g-GMA及PA6/SEBS-g-GMA/OMMT复合材料，均不能溶解于甲酸中，试样颗粒悬浮在甲酸溶液的最上方；而SEBS-g-MAH增韧制备的PA6/SEBS-g-MAH及PA6/SEBS-g-MAH/OMMT复合材料可溶于甲酸，显示的为一牛奶状的、胶状悬浮物。用3种不同接枝率的SEBS-g-MAH增韧制备的PA6/SEBS-g-MAH/OMMT复合材料中，随着MAH接枝率的增大，分散相的粒径减小，但复合材料的冲击强度基本保持不变、与MAH的接枝率大小无关。SEBS-g-GMA和SEBS-g-MAH均降低了PA6的熔融温度并且对PA6的结晶有阻碍作用。
        通过两步共混加工，即先将PA6与OMMT共混后，再将挤出物与SEBS-g-MAH共混制备的三元纳米复合材料具有优异力学性能，其冲击强度比用一步加工法（即，共混组分混合后同时加入到挤出机中进行挤出）制备的复合材料的冲击强度高122%。一步共混加工时，另加入少量GMA或EP作为相容剂，所制备的纳米复合材料与两步加工制备的具有相近的力学性能，并且极大地提高了材料的断裂伸长率，成为一种高韧性的工程塑料。相容剂的加入，使得共混体系间产生了微交联反应，共混物不能完全溶解于甲酸溶液中，复合材料体系的黏度增大，提高了材料的储能模量和损耗模量。
       采用弹性体SEBS-g-MAH与PC复合增韧PA6，极大地提高了PA6复合材料的冲击强度；同时用EP改善PC与基体PA6间的相容性，经反应挤出制备了高韧性的新型PA6工程塑料，当EP含量为1wt%时，冲击强度达到55.61kJ/m2，断裂伸长率达到306.4%，比纯PA的分别提高了313.2%和625.2%。这种新型增韧合金具有非常出色的机械性能，蒙脱土的引入进一步提高了复合材料的拉伸和弯曲性能。随着EP用量的增加，PA6与PC的相界面变的更加模糊，复合物的拉伸强度、弯曲强度及模量逐渐增大，冲击强度先增大后略下降。PC的加入有助于提高PA6/SEBS-g-MAH共混物的耐热性，相容剂EP使得体系中各相之间的界面黏结作用增强，进一步提高了材料的热分解温度。
Abstract：
A styrene-ethylene/butadiene-styrene triblock copolymers (SEBS) was functionalized respectively with glycidyl methacrylate (GMA) and maleic anhydride (MAH). PA6-based composites were prepared using the functionalized SEBS as a toughener, or adding polycarbonate at the same time, and one commercial organo-montmorillonite (OMMT) served as reinforcing filler. GMA or epoxy resin (EP) was used as a compatibilizer for the composites. Influence of the type of functional group, grafting degree, the contents of the filler and compatibilizer, and the micro-crosslinking among the components on the morphology, the structure and properties were investigated by all kinds of methods,e.g. XRD, SEM, TGA, DSC, FTIR, Molau test, mechanical properties test and rheology.
Firstly, PA6/OMMT nanocomposites were prepared by means of melt blending. When the content of OMMT was 4wt%, the nanocomposite has a higher tensile strength, flexile strength and flexile modulus. But the impact strength was decreased. The exfoliated behavior was confirmed by XRD and TEM. PA6/OMMT blend could scatter uniformly in the formic acid solution without sedimentation and phase separation.
The SEBS-g-GMA and SEBS-g-MAH were respectively prepared using GMA and MAH though melt extrusion. The grafting degrees were respectively 2.39% and 1.2%, which were decided by titration. SEBS-g-GMA and SEBS-g-MAH were used to prepare PA6/elastomer/OMMT nanocomposites. The mechanical properties, crystallization behavior, thermal stability and the morphology were investigated. The PA6/elastomer/OMMT had mechanical properties balanced between those of PA6 and PA6/elastomer blends. Brittle-ductile transition could happen when the content of elastomer was 30wt%, and the toughness improved rapidly. The tensile strength and flexile strength are above 90% of pure PA6. There is a clear trade-off between stiffness/strength versus toughness/ductility.
SEBS-g-GMA and SEBS-g-MAH had the different morphology in the composites. The particle size of SEBS-g-GMA is much larger than that of SEBS-g-MAH, due to the possible crosslinking with PA6. The toughening efficiency of SEBS-g-GMA was much lower than SEBS-g-MAH. The elastomer particle size decreased at low OMMT loading because OMMT could prevent dispersed phase coalescence. With increasing OMMT content, OMMT weakened the interfacial adhesion between PA6 and functionalized elastomer leading to an increase in the elastomer particle size and a decrease in the impact strength of the composites. PA6-based composites toughened by SEBS-g-GMA did not dissolve in the formic acid, and suspended in the upper of the tube. A milky and colloidal suspension was observed for PA6-based composites toughened by SEBS-g-MAH. The elastomer particle size clearly decreased with increasing MAH content. The impact strength remained almost constantly. SEBS-g-GMA and SEBS-g-MAH both decreased the melt temperature, and hindered the crystallization of the composites.
The ternary composites were prepared by two different blending sequences (N1 and N2). The method N1 means PA6, elastomer, and OMMT were blended simultaneously. The method N2 means that the ternary composite was produced through the premixing of PA6 and OMMT first and then melt blending with elastomer. The composite (N2) has better mechanical properties. The notched impact strength of the one composite (N2) was 122% higher than that of the other composite (N1), even for the same formulation. For the ternary composites prepared via method N1 with the addition of GMA or EP, the tensile strength, flexural strength, and flexural modulus just slightly decreased, whereas the impact strength and elongation at break were significantly enhanced. The chemical reaction between PA6, SEBS-g-MAH, and the compatilizer could enhance the viscosity, storage modulus, and loss modulus. The blends couldn’t dissolve in formic acid solution.
The impact strength of PA6/SEBS-g-MAH/PC composite improved greatly compared with that of PA6/SEBS-g-MAH composite. Epoxy resin was used to improve the compatibility between PA6 and PC. Then adding EP (1wt%) to PA6/SEBS-g-MAH/PC alloy, the notched impact strength of alloy is 55.61kJ/m2 (increasing 313.2%  as that of pure PA6) and the elongation at break is 306.4% (increasing 625.2% as that of pure PA6). Novel toughening alloy is gained with outstanding mechanical properties. In addition, the adding of OMMT improved the tensile and flexile properties of the composite remarkably. The interphase boundaries became increasingly indistinctive with the adding of EP, and the tensile and flexile strength increased. The notched impact strength increased firstly and then decreased. Polycarbonate would improve the thermal stability of the composites. The thermo-decomposing temperature rises obviously due to the crosslinking caused by the compatilizer EP.

 

 

论文题目：聚丙烯/天然海藻纤维复合材料的制备与性能研究
毕业学生：栾立醒
指导老师：吴唯教授
中文摘要：
       本论文以聚丙烯(PP)为基体树脂、以天然海藻纤维(SW)为增强材料，制备了全新的聚丙烯/天然海藻纤维(PP/SW)复合材料。基于对“熔融加工-注塑成型”工艺参数的优化，在普通热塑性复合材料成型设备中成功制备了PP/SW复合材料，并对其力学性能、热机械性能、结晶性能、动态流变特性、热稳定性及燃烧性能进行了详细表征。本论文提出了PP/SW复合材料内部相结构的转变模型，并发现SW纤维对PP树脂的固相阻燃剂功效。
       首先探讨PP/SW复合材料的可加工性，比较了SW纤维添加量、螺杆挤出机类型对复合材料熔融过程的影响。实验结果表明，双螺杆挤出机可有效对PP/SW复合材料进行熔融加工，能在保证SW纤维热稳定性的同时实现其在PP树脂中良好的分散性。TPU可作为高效熔融助剂消除熔体破裂现象。然而SW纤维添加量不应超过50wt%，以保证足够的熔体流动性能；熔融温度不应超过185°C，螺杆转速不应超过60rpm，以避免SW纤维剧烈热降解的发生。同时，PP/SW复合材料可通过注塑成型工艺制备，最佳注塑成型参数为：注塑温度=180°C，螺杆转速=60rpm，注塑压力=保压压力=60bar，模具温度=60°C，冷却时间=45s。
       通过力学性能表征衡量了SW纤维对PP树脂的增强效果。研究表明，表面碱处理能去除杂质从而提高SW纤维强度。然而PP树脂与SW纤维之间的弱相容性导致复合材料低劣的力学强度，因此必须使用界面相容剂。本论文将界面相容剂作用机理区分为“内相容机理”及“外相容机理”。结果表明“外相容剂”MAPP及“内相容剂”CESA均能有效提高PP/SW复合材料的力学强度；热机械测试中储能模量及损耗模量的提高同样证明了SW纤维对PP树脂的增强作用。然而损耗因子的不同改变趋势证明两种相容剂不同的作用机理；MAPP提高了PP/SW复合材料的刚性而CESA提高了柔性。SW纤维能加快PP树脂的结晶过程，但降低了相对结晶度。MAPP及CESA均能提高PP树脂的相对结晶度，充分发挥SW纤维的异相成核作用。
       动态流变学测试给出界面相容剂对PP/SW复合材料相结构改变的信息。SW纤维能有效的增强PP树脂，末端区“牛顿平台”的出现说明PP树脂与SW纤维物理交联网络的形成；同时PP/SW复合材料较宽的线性粘弹区域证明了成型加工工艺的可行性。CESA通过对相结构的改变，从本质上提高了PP树脂与SW纤维之间物理交联网络的表观屈服应力；而MAPP对末端区特性改变不明显。通过“时-温等效原理”分析，CESA将PP/SW复合材料从非均相体系转变为均相体系，从而提高了相结构的稳定性。在测试温度范围内，CESA避免了PP/SW复合材料内部相分离情况的发生。
       本论文还系统研究了PP/SW复合材料的热降解及燃烧性能。SW凭借自身良好热稳定性，能有效推迟PP树脂的热降解过程。SW纤维同时能发挥固相阻燃功效，显著降低PP树脂的燃烧参数。稳定的相结构有利于充分发挥SW纤维阻燃效应，最终实现其热释放总量及热释放速率峰值分别下降25%和75%，达到普通应用标准。然而，SW纤维没有改变PP树脂的可燃性。
       研究表明，PP/SW复合材料具有理想的加工性能，其基本性能达到使用要求；同时PP/SW复合材料的耐热、耐燃烧性能明显优于PP树脂，具有耐热复合材料的应用前景。本论文的研究丰富了PP/NVF复合材料中的界面相容剂作用理论，并为此类复合材料研究提出新的思路。
Abstract：
In this thesis, seaweed fibre (SW) is adopted as reinforcing fibre for polypropylene matrix (PP) for the first time, the novel polypropylene/seaweed fibre (PP/SW) composites is prepared. After optimization of the parameters during “melt extrusion-injection moulding”, PP/SW composites are successfully prepared by traditional processing equipments. The mechanical, thermal dynamical, crystallization, dynamic rheological properities as well as thermal decomposition and combustion progressions are well characterized. The model for phase structure transition of PP/SW composites is proposed as well as the solid-phase flame retardancy of SW fibre for PP matrix.
Taking consideration of the influence of SW content and type of extruder on the compounding, the processability of PP/SW composites is well evaluated. Based on the results, PP/SW composites are successfully prepared in a twin-screw extruder, which maintain the thermal stability of SW fibre as well as realize fine dispersion within PP matrix. TPU could act as efficient PPA (Polymer Processing Aid) in compounding that eliminates melt-fracture phenomena in PP/SW melt. However, SW content should below 50wt% in order to keep enough melt flow rate. Compounding temperature and rotation speed of screw should be strictly controlled below 185°C and 60rpm to avoid fierce thermal decomposition of SW fibre during extrusion. PP/SW composites could be easlier moulded in injection maschine, the ideal moulding parameters in this thesis are: injection temperature=180°C, rotation speed of screw=60rpm, injection pressure=moulding pressure=60bar, moulding temperature=60°C and cooling time=45s.
The reinforcing effect of SW fibre for PP matrix is evaluated by mechanical characterization. According to the properties, surface alkalization is could remove impurities from SW fibre thus improve its stiffness. However, the poor adhesion between PP matrix and SW fibre limits the properties of PP/SW composites; compatibilization and lubricating are of necessity. The lubricating effects are classified into “inner effect” and “outter effect” in this thesis. Based on the results, MAPP as “inner lubricant” and CESA as “outter lubricant” can both enhance the mechanical properties of PP/SW composites, which is in agreement to the raing of storage modulus and loss modulus from DMA test. Diversed effects on the damping factor state their difference in lubricating mechanisms, the stiffness is raised by MAPP while CESA improved the elasticity of PP/SW composites.
SW fibre accelerates the process of crystallization of PP matrix, but reduces its degree of crystallization. With either MAPP or CESA, the degree of crystallization is improved which proves the heterogeneous nucleation effect of SW fibre for PP matrix.
Dynamic rheological characterizations provide important information on the transition of phase structure for PP/SW composites. The wide linear viscoelastic region signifies fine dispersion of SW fibre, as well as feasibility of compounding and moulding process. A formation of “Newton Plateau” indicates the establishment of physical network between PP matrix and SW fibre. CESA remarkably changes the phase structure of PP/SW composites, and achieve a higher apparent yield stress; while MAPP leads to slight influence on the rheological properties. With “time-temperature superposition principle”, it can be concluded that CESA transforms PP/SW composites from heterogeneous system into homogeneous system. Within studied temperature region, no evidence for phase-separation is traced after the addition of CESA.
Moreover, the thermal decomposition and combustion behaviour of PP/SW composites are well studied in this thesis. With high thermal stability, SW fibre could delay the thermal decomposition of matrix. SW fibre also acts as a solid-phase flame retardant in the composite, remarkably reduces the combustion parameters of PP matrix. Higher uniformity in the composite is beneficial for SW fibre’s retarding effect, the total heat release and peak heat release rate are declined by 25% and 75%, respectively. However, SW fibre hardly reduces the flammability of PP matrix.
To conclude, PP/SW composites possess favourable processability with satisfying mechanical properties for normal usage. The heat and flame resistance of PP/SW composites is greatly higher in comparsion to PP matrix, thus promises its potential in applications. The lubricating mechanism for PP/NVF composites and SW fibre’s interesting flame retarding effect found in this thesis could promote related research.

 

 

论文题目：木粉填充聚丙烯复合材料的制备和性能研究

毕业学生：王茹 

指导老师：吴唯教授
中文摘要：
       本课题以聚丙烯（PP）为基体，80目松木粉（WF）为填充体，采用双螺杆挤出机通过熔融共混法制备了PP/WF复合材料。分别研究了木粉含量、不同相容剂及其含量、木粉碱处理、以及添加有机化蒙脱土（OMMT）对PP/WF复合材料性能的影响及其机理。结果表明，当添加未经处理的木粉时，随着木粉含量的增加，PP/WF复合材料力学性能下降，热稳定性降低，吸水率增加，熔体流动性变差。在所研究的PP-g-MAH、SEBS-g-MAH和EPDM-g-MAH三种相容剂中，PP-g-MAH对PP/WF复合材料的增容改性效果最为明显。当PP-g-MAH添加量为木粉质量的10%时，PP/WF复合材料的拉伸强度提高40.9%，弯曲强度提高47.3%，弯曲模量提高35.3%，并提高结晶速率，增加结晶度，提高热稳定性。木粉经18wt%浓度NaOH溶液处理后，可有效提高PP/WF复合材料的力学性能，且熔融流动性也变好。PP/MF中引入有机化蒙脱土（OMMT）可产生一定的插层效果，能提高复合材料的力学性能和热稳定性。马来酸酐中的极性酸酐基团一部分与木粉表面的羟基发生酯化反应，一部分与木粉中的羟基形成氢键，而非极性长链部分与PP基体相容性良好，由此对PP和木粉产生良好的增容效果。碱处理可去除木粉表面的杂质、灰分等，以及使木粉原纤化，增加PP和木粉接触的比表面积，从物理角度增加PP和木粉的界面粘合力。
       综上所述，木粉进行适当表面处理并添加合适的相容剂，可采用通用热塑性熔融成型设备制成PP/木粉复合材料。这种以天然纤维为添加组分的木塑复合材料，符合节约资源和保护环境的要求，存在巨大的市场价值和发展前景。
Abstract:
In this paper, PP and wood fiber with 80 meshes were choosed to prepare for PP/WF Composites. Research showed that tensile strength, flexural strength, impact strength, elongation at break was decreased with increased wood fiber content except flexural modulus which was increased. Addition of wood fiber brings faster crystallization, lower crystallinity, and poorer thermostability. Three maleated compatibilizer were used in this paper to improve the surface bonding of PP and wood flour. Research showed that PP-g-MAH is the best compatibilizer in this system and mechanical properties exhibited a great reinforcement by 10% adding. Alkali treatment was used to treat wood fiber. Result showed that alkali treatment for wood fiber is beneficial for mechanical properties, flowability, thermostability, but make water absorption increased. At last, added OMMT in PP/WF system. Research shows that OMMT is good for mechanical properties and thermostability of PP. The layer distance is enlarged after adding in PP which was found by XRD. PP-g-MAH can be used as compatibilizer for both of PP/OMMT and PP/WF. Tensile strength, flexural strength, flexural modulus were increase except impact strength when PP-g-MAH was added in PP/OMMT system.OMMT was peeling in PP if 3% PP-g-MAH was used which was researched by XRD. But OMMT brings PP/WF composites poorer mechanical properties. If OMMT and PP-g-MAH both were added in PP/WF system, then a better thermostability was produced.