提高与树脂界面复合性能的黄麻纤维酶促接枝疏水化改性研究

发布时间：2018-05-16 08:11

本文选题：黄麻 + 漆酶　；参考：《江南大学》2017年博士论文

【摘要】：近年来,采用自然界丰富的植物纤维(如麻纤维等)替代玻璃纤维和合成纤维作为树脂基复合材料的增强体日益受到人们的关注。植物纤维增强复合材料具有质量轻、强度高、力学性能好等优点,但由于植物纤维具有较强的极性和亲水性,使其与非极性树脂间的界面黏结性差,导致复合材料性能下降。为了得到性能优良的植物纤维增强复合材料,需要对植物纤维进行表面改性,降低植物纤维的亲水性,提高与疏水性树脂基体间的相容性。本课题利用黄麻纤维表面富含木质素及漆酶可催化氧化木质素分子结构中的酚羟基产生自由基的特性,引发具有疏水结构的外源功能单体(没食子酸月桂酯、十八胺)接枝到黄麻纤维表面的木质素上,实现黄麻纤维的表面疏水化改性,建立一种新型、高效的非均相体系下基于漆酶催化作用的麻纤维生物法接枝功能化改性方法,并将生物法表面疏水改性的黄麻纤维用于增强非极性聚丙烯(PP)树脂制备复合材料。通过研究麻纤维-酶-功能分子(疏水性单体)三者组成的非均相体系下麻纤维疏水性表面的酶法高效构筑与调控、麻/树脂复合材料界面结构特征和力学性能及其与纤维表面性能之间的关系,提高麻增强复合材料中麻纤维与树脂的界面相容性,进而提高界面的黏结强度和复合材料的整体性能。主要研究内容和结论如下:首先,研究了非均相体系下漆酶处理对黄麻纤维中木质素含量、化学结构及黄麻织物性能的影响。黄麻纤维经漆酶处理后,仅少部分木质素(约占总木质素的4%)发生降解溶于反应液中;大部分木质素仍保留在纤维上,且发生聚合、分子量增大、分子量分布变宽,同时木质素被漆酶氧化,分子结构中酚羟基及甲氧基含量减少,羰基含量增加,结构单元间连接方式β-O-4和β-β键的比例降低,β-5和β-1结构增多;黄麻纤维表面(复合胞间层)的木质素浓度高于纤维主体中,有利于基于木质素的漆酶催化纤维表面改性。漆酶处理黄麻织物表面木质素的酚羟基含量减少,醚键基团增多;织物的表面疏水性略有提高,由未处理的静态水接触角98.7°、润湿时间22.0 s增至漆酶处理的接触角109.2°、水滴润湿时间79.4 s;木质素在漆酶催化作用下发生前期降解-后期聚合的可逆反应,使黄麻纤维表层凸出的木质素在纤维表面移位重组,木质素等较紧密地附着在表面上,黄麻纤维表面变得较为平整、光滑、有序;由于纤维间木质素发生交联聚合,使黄麻织物的拉伸断裂强力提高,纬向增加4.9%、经向增加2.6%,同时由于纤维表面变得光滑,纱线中纤维间的抱合力降低,织物的断裂伸长率得到提高,纬向增加173.0%、经向增加151.7%。其次,研究了利用黄麻织物富含木质素及漆酶催化木质素、没食子酸月桂酯的酚羟基形成自由基引发交联耦合的特性,将分子结构中含长烷基链的疏水性外源单体-没食子酸月桂酯(DG)在非均相体系漆酶催化作用下接枝到黄麻织物表面。首先,通过ATR-IR、XPS、SEM、AFM等测试手段对其进行了定性表征;其次,采用称重法和皂化返滴定法对黄麻织物的漆酶催化接枝DG反应进行了定量表征,称重法测得的单体接枝率为4.16%,接枝效率为49%,皂化返滴定法测得的接枝黄麻织物上DG的含量为3.19%;漆酶催化黄麻织物接枝DG的最佳反应条件为缓冲液p H 3、漆酶用量1.0 U/m L、单体用量5 m M、反应温度50℃、反应时间4 h;黄麻织物经酶促接枝没食子酸月桂酯后,表面疏水性得到提高,由未处理的静态水接触角29.8°、水滴润湿时间3.6 s增至接枝改性处理的接触角111.5°、润湿时间≥30 min。而后,研究了利用黄麻织物富含木质素及漆酶催化氧化木质素形成自由基引发伯胺类化合物交联耦合的特性,将分子结构中含长烷基链的疏水性外源单体-十八胺(OA)在非均相体系漆酶催化作用下接枝到黄麻织物表面的木质素上。首先,通过ATR-IR、XPS、SEM等测试手段对其进行了定性表征;其次,将漆酶催化接枝十八胺后黄麻织物中的木质素提取出来进行MALDI-TOF MS和1H-NMR、13C-NMR、HSQC-NMR等分子结构表征,证明在漆酶催化作用下伯胺类单体以共价键接枝到黄麻织物的木质素结构单元上;然后,采用微量凯氏定氮法对黄麻织物的漆酶催化接枝OA反应进行了定量表征,测得的单体接枝率为0.712%,接枝效率为10.571%,由于伯胺类单体本身不能被漆酶催化聚合,只能发生与木质素自由基的耦合反应接枝到木质素分子上或木质材料表面,剩余单体可回收再用,而酚类单体在漆酶催化作用下不可避免地发生自聚反应,降低了单体的利用率,故伯胺类单体较酚类单体在实际应用中更具有经济优势。经酶促接枝十八胺后,黄麻织物的表面疏水性得到提高,由未处理的前进接触角43.5°、后退接触角零、水滴润湿时间4 s增至接枝改性处理的静态接触角112.5°、前进接触角116.4°、后退接触角42.7°、润湿时间1110 s;对漆酶催化接枝反应过程中的单体浓度和反应时间进行工艺优化,发现随单体浓度增加,OA在黄麻织物上的接枝率逐渐增加,但单体的接枝效率不断降低。随反应时间延长,黄麻织物的接枝率与单体的接枝效率均逐渐增加,但超过12 h后增长变得缓慢。黄麻织物的接触角和润湿时间表现出不同的增长趋势,润湿时间随单体浓度或反应时间的增加逐渐提高,而接触角在织物接枝处理后迅速增加,但随单体浓度或反应时间的增加基本维持不变。最后,将漆酶催化改性后的黄麻织物用于增强PP树脂制备复合材料。仅经漆酶处理的黄麻织物与PP复合材料的力学性能有所提升,与对照样相比,拉伸断裂强力提高4.5%,拉伸模量提高18.2%,剪切断裂强力提高14.7%,剪切模量提高32.6%,但断裂伸长率均降低,拉伸断裂伸长率降低2.9%,剪切断裂伸长率降低12.8%。动态热机械性能中,复合材料的储能模量增加,基体树脂熔融温度略有提高;DG接枝疏水化黄麻织物/PP复合材料的拉伸断裂强力较未处理样提高了58.3%,断裂面较为规则、整齐,纤维与树脂同时被拉断,表现出良好的界面黏结性;OA接枝疏水化黄麻织物/PP复合材料的拉伸断裂强力和杨氏模量较未处理样分别提高了82.0%和22.2%,当复合材料拉伸时增强纤维与树脂基体一起受力断裂,断裂面较为平整,同时复合材料的储能模量与损耗模量提高,表明改性后的黄麻织物与PP树脂的界面相容性改善,界面黏结牢度增强。
[Abstract]:In recent years, more and more attention has been paid to the use of natural rich plant fiber (such as hemp fiber, etc.) instead of glass fiber and synthetic fiber as resin matrix composites. Plant fiber reinforced composites have the advantages of light quality, high strength and good mechanical properties, but the plant fiber has strong polarity and hydrophilic properties. In order to get better performance of the plant fiber reinforced composites, the surface modification of plant fiber, the hydrophilicity of the plant fiber and the compatibility with the hydrophobic resin matrix are needed to obtain the excellent performance of the plant fiber reinforced composites. The quality and laccase can catalyze the properties of free radicals produced by the phenolic hydroxyl groups in the molecular structure of the lignin, and lead to the grafting of the exogenous functional monomers (laurate gallate, eighteen amine) onto the lignin on the surface of jute fiber, and the hydrophobic modification of jute fibers can be realized, and a new and highly efficient heterogeneous system is established. A modified method of functional modification of hemp fiber based on laccase catalysis was used, and the hydrophobically modified jute fiber was used to enhance the preparation of non polar polypropylene (PP) resin. The hydrophobic surface of hemp fibers under the heterogeneous system of three groups of hemp fiber, enzyme functional molecules (hydrophobic monomers) was studied. The relationship between the interfacial structural characteristics and mechanical properties of the hemp / resin composites, the relationship between the interfacial properties and the surface properties of the hemp / resin composites, the interfacial compatibility between the hemp fibers and the resin in the linen reinforced composites, and the bonding strength of the interface and the whole properties of the composites are improved. The main contents and conclusions are as follows: first, The effect of laccase treatment on lignin content, chemical structure and performance of jute fiber in jute fiber was studied under the heterogeneous phase system. After laccase treatment, only a few lignin (about 4% of total lignin) were degraded in the reaction solution, and most lignin was retained on the fiber, and the molecular weight was increased and the molecular weight was increased. The distribution of the seed quantity is broadened, and the lignin is oxidized by laccase, the content of phenol hydroxyl and methoxy in the molecular structure is reduced, the content of carbonyl group is increased, the proportion of beta -O-4 and beta - beta bond between the structural units is reduced, the structure of beta -5 and beta -1 is increased, and the lignin concentration of the jute fiber surface (intercellular layer) is higher than that of the fiber body, which is beneficial to wood based on wood. Laccase laccase catalyzes the surface modification of the fiber. The phenol hydroxyl content of the lignin on the jute fabric is reduced and the ether bond group increases. The surface hydrophobicity of the fabric is increased slightly, the untreated static water contact angle is 98.7 degrees, the wetting time is 22 s to 109.2 degrees of the contact angle of laccase treatment, and the wetting time of water droplets is 79.4 s; the lignin is urging in laccase. The reversible reaction of early degradation and later polymerization under the action of chemical reaction makes the convex lignin on the surface of jute fiber displaced and reorganized on the surface of the fiber, and the lignin is attached to the surface more closely. The surface of jute fiber becomes more smooth, smooth and orderly. The tensile fracture strength of the jute fabric is caused by the crosslinking polymerization of the lignin in the fiber. In addition, the latitudes increase by 4.9%, the meridian increase of 2.6%, and the smoothness of the fiber surface, the tensile strength of the fibers in the yarn is reduced, the elongation at break of the fabric is increased, the latitude is increased by 173%, and then 151.7%. is added to the lignin and laccase catalyzed lignin and the phenol hydroxyl group of lauryl gallate. The properties of crosslinking coupling caused by free radicals were formed, and the hydrophobic exogenous monomers of the molecular structure, DG, were grafted onto the surface of jute fabric under the catalysis of inhomogeneous laccase. First, the qualitative characterization was carried out by means of ATR-IR, XPS, SEM, AFM and so on. Secondly, weighing method and saponification were used. The DG reaction of the laccase catalyzed grafting of jute fabric was quantitatively characterized by back titration. The grafting rate of the monomer was 4.16%, the graft efficiency was 49%, the content of DG on the grafted jute fabric obtained by saponification back titration was 3.19%, and the best reaction condition of the laccase catalyzed grafting of jute fabric to DG was the buffer solution P H 3 and the laccase dosage 1 U/m L The monomer dosage is 5 m M, the reaction temperature is 50 C and the reaction time is 4 h, and the surface hydrophobicity of jute fabric is improved by enzymatic grafting of lauryl gallate, the surface hydrophobicity of the jute fabric is improved, the untreated static water contact angle is 29.8 degrees, the wetting time of water droplet is 3.6 s to the grafting modification contact angle 111.5 degrees, and the wetting time is more than 30 min., then the use of jute fabric is studied. The properties of the crosslinking coupling of lignin and laccase catalyzed oxidation of lignin to form free radicals to induce the crosslinking of primary amine compounds, the hydrophobic exogenous monomer - eighteen amine (OA) in the molecular structure was grafted onto the lignin on the surface of jute fabric under the catalysis of inhomogeneous system laccase. First, ATR-IR, XPS, SEM and other testing methods Secondly, the lignin in jute fabric was extracted by grafting laccase catalyzed by laccase to carry out MALDI-TOF MS, 1H-NMR, 13C-NMR, HSQC-NMR and other molecular structures. It was proved that under the catalysis of laccase, the primary amine monomers were grafted onto the lignin structural unit of jute fabric with covalent bonds. The Kjeldahl method was used to quantitatively characterize the OA reaction of the laccase catalyzed grafting of jute fabric. The monomer grafting rate was 0.712% and the graft efficiency was 10.571%. Because the primary amine monomer itself could not be polymerized by laccase, the coupling reaction with lignin free radicals could only be grafted onto the lignin molecule or the wood material surface. The body can be reclaimed and reused, and the self polymerization of the phenolic monomers will inevitably occur under the catalysis of laccase, which reduces the utilization of the monomer. Therefore, the primary amine monomers have more economic advantages than the phenolic monomers in the practical application. After the grafting of eighteen amine, the surface water thinability of jute fabric is improved and the untreated advance contact angle is 43.5. The wetting time of water droplet was 4 s to 112.5 degree of static contact angle of graft modification, 116.4 degree of advance contact angle, 42.7 degree back contact angle and 1110 s wetting time, and the grafting of monomer and reaction time during the reaction process of laccase were optimized, and the grafting of OA on jute fabric with the increase of monomer concentration was found. The grafting efficiency of the monomer gradually decreased, but the grafting efficiency of jute fabric and the grafting efficiency of the monomer increased gradually with the reaction time. The contact angle and wetting time of jute fabric showed a different growth trend, and the wetting time increased with the increase of monomer concentration or reaction time with the increase of the reaction time. Gradually, the contact angle increased rapidly after the grafting of the fabric, but with the increase of the monomer concentration or the reaction time. Finally, the jute jute fabric modified by laccase was used to enhance the PP resin composite. The mechanical properties of the jute and PP composites treated only by laccase were improved and compared with the control samples. Tensile fracture strength increased by 4.5%, tensile modulus increased by 18.2%, shear fracture strength increased by 14.7%, shear modulus increased by 32.6%, but elongation at break decreased by 2.9%, elongation at shear elongation decreased in 12.8%. dynamic thermal mechanical properties, the storage modulus of composite material increased and the melting temperature of matrix resin increased slightly. The tensile strength of DG grafted hydrophobically hydrophobic jute fabric /PP composite is 58.3% higher than that of untreated sample, and the fracture surface is more regular and regular. The fiber and resin are broken at the same time, showing good interfacial adhesion; the tensile strength and Young's modulus of the OA graft hydrophobic jute fabric /PP composite are higher than those of the untreated samples. 82% and 22.2%, when the composite is stretched, the strength of the reinforced fiber and the resin matrix is broken, the fracture surface is more flat, and the energy storage modulus and loss modulus of the composites are improved, indicating that the interfacial compatibility of the modified jute fabric and the PP resin is improved, and the adhesion strength of the interface is enhanced.

【学位授予单位】：江南大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TS102.223;TS195.6

【参考文献】