碱式硫酸镁晶须表面改性及其在聚丙烯材料中的应用研究

发布时间：2017-12-28 09:02

本文关键词：碱式硫酸镁晶须表面改性及其在聚丙烯材料中的应用研究　出处：《中国科学院大学(中国科学院青海盐湖研究所)》2017年博士论文　论文类型：学位论文

【摘要】：碱式硫酸镁晶须(MOSw)是一种典型的无机镁盐晶须,具有良好的阻燃性能及较强的机械性能,被广泛应用于聚合物基复合材料的增强和阻燃领域。然而,在相关的研究中人们发现,MOSw填充聚合物基体主要存在两个问题:i)MOSw表面自由能较大,容易发生团聚,导致其在基体中分散不够均匀;ii)MOSw表面极性较大,属于亲水性,而绝大多数聚合物均属于亲油性,两者相容性很差。基于以上问题,本研究采用表面改性的方法对MOSw进行处理,再将改性后的MOSw添加到聚丙烯(PP)基体中,测试其力学性能、结晶性能、热性能、阻燃性能、流变性能等变化情况。研究内容主要包括以下几个方面:(1)通过测试改性MOSw的接触角与亲油化度,考察改性剂用量、温度、时间等条件对MOSw改性效果的影响,确定了五种脂肪酸改性MOSw的较优条件;以月桂酸(LA)为例,进一步研究其改性机理:即LA与MOSw表面发生了类似“酸碱中和”的化学反应,LA以单分子层形式均匀包覆在晶须表面。(2)类似地,通过测试改性MOSw的接触角与亲油化度,确定了乙烯基三乙氧基硅烷(VTES)改性MOSw的较优条件:V(VTES):V(H2O):V(C2H5OH)=20:8:72,水解时间为3 h,水解温度为25°C,VTES用量为晶须质量的5 wt%,改性温度为60°C,改性时间为60 min;改性后的晶须样品中存在Si-O-Mg和Si-O-Si键,而不存在Si-O-C键,说明硅烷偶联剂与晶须发生了化学键合作用。(3)类似地,通过测试改性MOSw的接触角与亲油化度,确定了十二烷基单磷酸酯(DDP)改性MOSw的较优条件:以H2O为溶剂,加入KOH促进DDP溶解,DDP用量为3 wt%,改性温度为25°C、改性时间为30 min;改性后晶须在有机相中分散性很好,P-O-Mg键的存在说明DDP与晶须表面发生了化学键合作用。(4)采用熔融共混法制备PP/MOSw复合材料,考察不同改性剂对其力学性能、结晶性能、热性能及阻燃性能的影响。结果表明,LA改性对PP基体的异相成核促进效果最佳,并且可以诱导生成一定量β晶型PP,因此其增韧效果最佳;VTES改性能够有效提高MOSw与PP基体的界面相互作用强度,导致复合材料屈服强度和杨氏模量明显增大;DDP改性则能够进一步提高PP/MOSw复合材料的阻燃性能,主要是因为DDP促进PP基体成炭,形成结构更加完整、致密的保护层,从而更好的阻隔燃烧所需的能量及可燃性物质的传递。(5)以PP-g-MAH或POE-g-MAH为相容剂,采用熔融共混法制备PP/相容剂/MOSw复合材料,考察不同相容剂对PP/MOSw复合材料力学性能、结晶性能、热性能等的影响。结果表明,PP-g-MAH增强PP/MOSw复合材料效果更好,原因有三点:i)PP-g-MAH接枝率较高,能够与较多的MOSw发生开环酯化反应;ii)PP-g-MAH与PP基体结构非常相似,两者相容性较好;iii)PP-g-MAH的加入能够促使MOSw在PP基体中均匀分布。另一方面,POE-g-MAH增韧PP/MOSw复合材料效果较好,原因有两点:i)POE-g-MAH能够诱导生成一定量的β晶型PP;ii)POE-g-MAH对PP/MOSw的界面相容性有一定程度改善。(6)以PP-g-MAH为相容剂,采用熔融共混法制备PP/PP-g-MAH/不同形貌碱式硫酸镁(MOS)复合材料,通过测试复合材料力学性能、结晶性能、流变性能等,考察不同形貌MOS对PP基体性能影响。结果表明,颗粒状MOS的加入能够提高PP基体的韧性,与β晶型PP的生成及异相成核效应有关;晶须状MOS在PP基体中容易形成连续的网状结构,这是MOSw增强PP基体的主要原因。随着MOSw添加量的增大,复合材料样品的结构从“类液体”转变为“类固体”。总而言之,本论文的研究结果为MOSw填充聚合物复合材料的应用提供了详细的理论支持,同时对其他晶须材料填充聚合物复合材料的研究具有一定的参考意义。
[Abstract]:The basic Magnesium Sulfate whisker (MOSw) is a typical inorganic magnesium salt whisker. It has good flame retardancy and strong mechanical properties. It is widely used in the field of polymer matrix composites for enhancing and flame retardancy. However, people found in related research, MOSw filled polymer matrix, there are two main problems: I) MOSw surface free energy is large, easy to agglomerate, resulting in the dispersion in the matrix is not uniform; ii) MOSw large surface polarity, which belongs to the hydrophilicity, and the vast majority of polymer are lipophilic, both compatibility poor. Based on the above problems, the surface modification method was used to treat MOSw and the modified MOSw was added to polypropylene (PP) matrix. The mechanical properties, crystallization properties, thermal properties, flame retardancy and rheological properties of the PP were tested. The main contents are as follows: (1) through the test of modified MOSw contact angle and lipophilicity, the effects of modifier dosage, temperature and time conditions on the modification effect of MOSw, five kinds of optimal conditions for modified MOSw fatty acid; with lauric acid (LA) as with the further study of the mechanism of modification: LA and MOSw surface chemical reactions similar to "Neutralization", LA to form the single molecular layer evenly coated on the surface of whiskers. (2) similarly, through the test of modified MOSw contact angle and lipophilicity, determine the vinyltriethoxysilane (VTES) byhydrothermalmethod modification of MOSw: V (VTES): V (H2O): V (C2H5OH) =20:8:72, the hydrolysis time was 3 h, hydrolysis temperature is 25 at C, VTES dosage is 5 of the mass of wt% whisker, modification temperature is 60 ~ C, modification time was 60 min; Si-O-Mg and Si-O-Si bond after the existence of whisker in the sample, and there is no Si-O-C key that silane coupling agent and whisker the chemical bonding. (3) similarly, through the test of modified MOSw contact angle and lipophilicity, identified twelve alkyl monophosphate (DDP) byhydrothermalmethod modified MOSw: using H2O as solvent, promote the dissolution of DDP into KOH, DDP dosage is 3 wt%, the modification temperature is 25 ~ C, modification time 30 min; modified whisker in organic phase dispersion is very good, there are P-O-Mg bond DDP and whisker surface chemical bonding effect. (4) PP/MOSw composites were prepared by melt blending, and the effects of different modifiers on the mechanical properties, crystallization properties, thermal properties and flame retardancy of the composites were investigated. The results show that the LA modification of PP matrix nucleation promoting the best effect, and can be induced to produce a certain amount of beta crystalline PP, so the toughening effect is best; VTES modification can effectively improve the MOSw and PP matrix interfacial interaction strength, the resulting composite material yield strength and Young's modulus increased significantly; DDP it can further improve the flame retardant properties of PP/MOSw composite materials, mainly because the carbon matrix of PP promoting DDP, forming a protective layer structure is more complete and compact, so as to better transfer barrier needed for the combustion of combustible material and energy. (5) using PP-g-MAH or POE-g-MAH as compatibilizer, PP/ compatibilizer /MOSw composites were prepared by melt blending method, and the effects of different compatibilizer on mechanical properties, crystallization and thermal properties of PP/MOSw composites were investigated. The results show that the PP-g-MAH reinforced PP/MOSw composites better effect, there are three reasons: I) PP-g-MAH higher grafting rate, can ring opening esterification reaction with more MOSw; II PP-g-MAH) and PP matrix structure is very similar to the good compatibility; iii) the addition of PP-g-MAH can promote the uniform distribution of MOSw in PP matrix. On the other hand, the toughening effect of POE-g-MAH on PP/MOSw composites is good. There are two reasons: I) POE-g-MAH can induce a certain amount of beta crystal PP, II) POE-g-MAH has a certain degree of improvement on the interfacial compatibility of PP/MOSw. (6) using PP-g-MAH as compatibilizer, PP/PP-g-MAH/ different morphology Magnesium Sulfate (MOS) composites were prepared by melt blending. The effects of MOS on the properties of PP matrix were investigated by testing the mechanical properties, crystallization and rheological properties of composites. The results show that the addition of granular MOS can improve the toughness of PP matrix, which is related to the formation and heterogeneous nucleation effect of beta crystalline PP. Whisker MOS is easy to form continuous network structure in PP matrix, which is the main reason for MOSw to enhance PP matrix. With the increase of the amount of MOSw, the structure of the composite samples changed from "liquid like" to "like solid". In conclusion, the research results in this paper provide detailed theoretical support for the application of MOSw filled polymer composites, and have some reference significance for other whisker materials filled polymer composites.
【学位授予单位】：中国科学院大学(中国科学院青海盐湖研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ325.14;TB332

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