纤维素/聚乳酸复合材料的结构与性能

以机械球磨法预处理纸浆纤维素纤维,研究球磨对纤维素形貌和结构的影响;以纤维素颗粒为填料,通过熔融加工方法,制备出可完全再生且可完全降解的聚乳酸(PLA)复合材料,对复合材料的形貌、结构和性能进行了表征测试。结果表明,作为干法工艺,机械球磨可以简便地制备微晶纤维素(MCC)。加入纤维素颗粒以后,复合材料的冲击强度显著增加(最高达70.7%),断面出现韧性断裂特征;PLA的玻璃化转变温度和冷结晶温度升高,最大分解速率温度降低约15℃,热稳定性略有下降。     

3D打印聚合物纳米复合材料的研究进展

相对于传统制造方法如挤出成型、模压成型等,3D打印技术不仅能够快速成型结构复杂且精细的产品,而且还可以根据不同功能、性能需求选择不同材料进行快速制造.凭借这一优势,3D打印越来越受到人们的重视,越来越多的3D打印产品被应用到人们的生活、学习和工作中.在众多3D打印材料中,聚合物材料(如热固性和热塑性聚合物等)的占比大、应用广,大到房屋内饰、小到微/纳米电子设备都可以通过3D打印聚合物材料来实现.然而,相比于传统方法制造的聚合物材料,3D打印聚合物材料强度低、打印层之间界面结合差,所以目前3D打印聚合物材料主要用于模型和非结构材料.为提高3D打印聚合物材料的强度,纳米材料(如纤维素纳米晶)常被用作增强体与聚合物材料混合打印,以此制备高强、多功能的3D打印纳米复合材料.纤维素纳米晶来源广泛、价格低廉、可再生、强度高,是一种十分理想的天然纳米增强材料.因此,近年来纤维素纳米晶在3D打印聚合物纳米复合材料中的应用受到广泛关注.除研究纳米材料对3D打印聚合物材料性能的影响外,研究者们还从纳米材料改性和新型纳米材料的研发等方面不断进行尝试,在提高3D打印聚合物纳米复合材料强度的同时赋予其更多的功能性,并取得了丰硕的成果.此外,借助光固化3D打印和聚合物熔融沉积成型两项基本原理相近、成型机理不同的3D打印技术,研究者们从打印纳米复合材料的结构、性能及功能出发,分别研究不同打印技术实现材料"结构-性能-功能"的可能性和可行性,为3D打印聚合物纳米复合材料的拓展应用提供了可靠依据.本文在简述3D打印技术的基础上,重点阐述常用于热固性和热塑性聚合物3D打印技术的基本原理和特点;着重分析两项不同3D打印技术在聚合物纳米复合材料领域的应用情况,总结3D打印聚合物纳米复合材料的性能特征和应用范围,以期为3D打印纳米复合材料的广泛应用奠定基础.     

基于熔融沉积3D打印聚乳酸基复合材料的研究进展

目的 半结晶性聚乳酸(PLA)因透明性好、力学性能优异、能生物降解等优点,在加工领域表现出适用范围广等特性,因此对PLA基复合材料在3D打印技术中的研究应用及最新进展状况进行总结,以期提供借鉴与参考。方法 以熔融沉积成型(FDM)、PLA基体为主线,在查阅近年中外文献基础上,分别从PLA结构性能、3D打印成型工艺、PLA基复合材料改性等方面进行了探讨,着重分析工艺参数的技术优化,以及复合材料的结构改性最新研究进展。结果 FDM制备PLA基复合材料的研究取得了丰硕的成果,在3D打印行业中表现优异,潜力巨大,商品化程度越来越高。结论 低廉、高效、可定制的3D打印受到国内外科研工作者广泛关注与青睐,随着新技术的不断探索和突破,以及纳米材质和新型聚合物材料等新型材质应用,使3D打印在成型加工技术上占据绝对优势。     

乳酸原位聚合改性纳米纤维素的制备及应用

乳酸原位聚合改性纳米纤维,并和聚乳酸制备复合材料。先由64%硫酸水解微晶纤维素(MCC)制备纳米纤维素(NCC),再乳酸原位聚合接枝纳米纤维素得到改性后纳米纤维素(g-NCC),最后将g-NCC按0%~5%质量比与聚乳酸(PLA)共混,制成复合材料g-NCC/PLA。透射电子显微镜观察得到棒状纳米纤维素长度为100~200nm,直径为10~25nm,傅里叶变换红外光谱和核磁共振谱证明乳酸均聚物已接枝到纳米纤维素,复合材料性能分析表明g-NCC与PLA相容性比未改性NCC与PLA相容性好,g-NCC含量为2%时,复合材料拉伸强度可达到45 MPa,比纯PLA提高85%,结晶度提高10%。     

粘胶纤维与Lyocell纤维增强聚乳酸复合材料的性能比较

以聚乳酸(PLA)为基体,分别采用粘胶纤维与Lyocell纤维这2种典型的再生纤维素纤维为增强纤维,通过熔融共混和注塑成型制备了再生纤维素纤维/PLA复合材料,并对这2种复合材料的性能进行了比较研究。结果表明,采用粘胶纤维或Lyocell纤维增强均可有效提高PLA复合材料的结晶度、力学性能和维卡软化温度。粘胶纤维的锯齿形截面有利于其与PLA基体的结合,因此粘胶纤维/PLA复合材料具有略高的冲击强度及拉伸强度。Lyocell纤维增强更有利于复合材料结晶度的提高,使得Lyocell/PLA复合材料具有更高的弹性模量和维卡软化温度。     

熔融沉积打印微纳米生物质填料增强聚乳酸基复合材料的研究进展

熔融沉积成型(Fused deposition modeling,FDM)因其制造成本低廉和工艺简易等特点成为现今增材制造(Additive manufacturing,AM)技术中应用最广泛的一种类型,而聚乳酸(Polylactic acid,PLA)也因其良好的可生物降解性和生物相容性成为FDM线材的主要原料。但是,PLA较差的脆性、韧性及热稳定性等缺点严重限制了其打印产品在市场上的应用。因此,在PLA线材中加入某种或多种填料是解决其自身缺点的重要措施。其中,生物质填料是一种比较理想的选择,在PLA中加入生物质填料不仅可以有效克服基材的性能缺陷,而且产品具有良好的可生物降解性和环境友好性。本文综述了近几年来FDM打印生物质填料增强PLA复合材料的研究进展,阐释不同尺度结构(由微米尺寸到纳米尺寸)的生物质增强填料(如木粉、天然纤维、纳米纤维素)对PLA基复合材料的性能影响,并分析和总结复合材料的性能改善原因及其界面相容机制,最后对FDM打印PLA基复合材料的未来发展进行了展望。     

韧皮纤维的层级结构及其力学行为研究进展

韧皮纤维是一种重要的非木质植物纤维,具有较好的力学性能和环境友好性,被广泛用于增强复合材料。在韧皮纤维细胞壁中,螺旋结构的纤维素被半纤维素、果胶、木质素等无定形基质聚合物包裹。随着纤维素微纤丝角度变化,形成了多薄层/壁层的细胞壁结构。这种不同层级细胞壁的组装构筑,对于韧皮纤维力学性能的产生与力学行为的表现均具有重要影响。本文总结了以麻为代表的韧皮纤维在组织层级、细胞层级、细胞壁层级及分子层级的结构特点;重点分析了不同微观尺度的构造特征对单轴拉伸过程中纤维力学行为的影响;最后对韧皮纤维层级结构与力学行为研究存在的问题及未来发展方向提出了建议和展望,以期为韧皮纤维的利用及多尺度仿生结构的构建提供新思路。     

熔融沉积成形锰锌铁氧体/聚乳酸复合材料的力学和吸波性能

3D打印技术在快速制造复杂形状零件方面获得了越来越多的关注。将锰锌铁氧体(MZF)作为增强体填充到聚乳酸(PLA)中，通过球磨混合和熔融挤出法制备出MZF/PLA复合线材，利用熔融沉积成形(FDM)制备出MZF/PLA复合材料。采用XRD、 SEM和矢量网络分析仪对不同复合比例的MZF/PLA复合材料的微观形貌、力学性能和电磁性能进行表征，并计算不同厚度的反射损耗，研究MZF的含量对复合材料吸波性能的影响。结果表明：当MZF含量为10wt%时，MZF/PLA复合材料的拉伸强度相比纯PLA提升了17.6%，随着MZF含量的提升，复合材料的吸波性能随之增强。当MZF的含量达到50wt%，在12.7 GHz处，厚度为7.4 mm时反射率达到最小值-55.3 dB，在厚度为7.9 mm时，有效吸波频带宽为4.5 GHz。因此，基于FDM制备的3D打印MZF/PLA复合材料具有良好的吸波性能和承载能力，是一种非常有前途的3D打印微波吸收材料。     

聚乳酸/聚乙二醇/羟基磷灰石多孔骨支架的3D打印制备及其生物相容性

聚乳酸(PLA)是一种应用广泛的生物高分子材料,但在应用过程中存在韧性、亲水性、生物活性差等缺点。用聚乙二醇(PEG)和羟基磷灰石(HA)对PLA进行改性。通过熔融共混制备不同质量比的PLA/PEG/HA复合3D打印线材,并通过分析PLA/PEG/HA线材的力学性能、结晶性能、热性能、流变性能等,筛选更适合熔融沉积成型(FDM)的3D打印成型线材,进而利用3D打印制备精度高的力学性能试样及生物相容性好、细胞可增殖和分化的生物多孔支架。结果表明:PEG的添加提高了PLA的韧性,降低了PLA的熔点。HA的添加则提高PLA/PEG/HA复合材料的弹性模量和冷结晶温度,同时HA也可以改善复合材料的加工性能。SEM与荧光标记结果表明多孔支架与细胞具有良好的生物相容性。生物支架对体外细胞的成功培养,为进一步发掘生物多孔支架在动物体内、生物医学及定制化应用方面提供了潜在可能。     

多孔再生纤维素/聚乳酸复合材料的制备与性能

通过简易、绿色环保的方法,将纤维素用NaOH/尿素体系进行溶解、再生、冷冻干燥获得再生纤维素(RC)多孔材料,再浸渍聚乳酸(PLA)获得多孔RC/PLA复合材料。该复合材料具有与多孔RC材料相同的开孔结构,超轻,高孔隙率等特性。随PLA的引入,多孔复合材料的三维纤维网络结构向密实片层结构转变,缺陷结构逐渐完善,其压缩强度大幅度提高。RC/PLA的压缩强度和模量相比于RC分别提高了369.8%和633.6%。     

Additive manufacturing of CNTs/PLA composites and the correlation between microstructure and functional properties

Owing to the facile,low cost,rapid,personalization characters,3D printing method has been one of the most attractive additive manufacturing processes in medicine,airplane,packaging and printing areas.In this work,a series of carbon nanotubes/polylactic acid(CNTs/PLA) composites were prepared through the combination of molten co-extrusion and 3D printing processes.The orientation and dispersion of CNTs in PLA matrix were investigated to explore the impact of 3D printing process on the morphology of CNTs/PLA composites via transmission electron microscopy,field emission scanning electron microscopy and Raman spectroscopy.X-ray diffractometer,differential scanning calorimetry,and thermal gravity analysis were employed to study the crystal structure and thermal properties of the composites.In addition,the electrical conductivity of the prepared specimen revealed that the orientation of CNTs in PLA might enhance the conductivity of the composite.It was found that 3D printing process was beneficial to increasing the purity of CNTs,electrical conductivity and mechanical properties of CNTs/PLA composites.     

PLA/木质纤维复合材料的制备及性能

目的研究PLA/木质纤维复合材料的制备工艺过程,分析PLA纤维含量对复合材料力学性能的影响,确定最优配比,以获得一种可应用于包装中的新型环保复合材料。方法将不同质量配比的PLA纤维及木质纤维按照造纸的工艺进行抄造,获得湿纸胚后再进行热压处理,获得需要的复合材料。对PLA纤维在复合材料中的分散性以及复合材料的力学性能进行表征与测试。结果分散性试验表明,PLA纤维能够与木质纤维均匀混合;当PLA纤维的质量分数为10%时,复合材料的性能较好。力学测试表明,复合材料的拉伸强度最大可达到42.79 MPa,耐折次数可达到1015次。结论 PLA/木质纤维复合材料可采用造纸的方法进行制备,且力学性能较好,能在包装领域内有较为广泛的应用,同时也为可降解纤维的研究应用提供了一种新思路。     

3D magnetic printing of bio-inspired composites with tunable mechanical properties

In the natural composites, the reinforcement particles are subtly organized into complex structures in matrix, and its various microstructures endow the biomaterials with a variety of excellent mechanical behaviors. Among the various reinforcement building blocks used in biomaterials, short fibers are the most ubiquitous reinforcement elements. Unfortunately, because of the limitation of fabrication technique, replication of these fiber-reinforced biological composites can be extremely difficult in practice. In this paper, we developed a fiber assembly 3D printing process, which can manipulate the orientation of fibers during 3D printing procedure. Benefiting from this technology, the reinforcement particles were manipulated remotely and the arrangement of reinforcement particles with higher degree of freedom was achieved. Subsequently, based on the herringbone-modified helicoidal architecture of mantis shrimp, the bio-inspired composites with various microstructures were reconstructed by 3D magnetic printing. In addition, the influence of microstructure type and parameters of bio-inspired composites on the properties of composites was studied systematically, and the quantitative relationship between microstructure and properties of the composites was established. The results show that the impact resistance and compression resistance of the composites can be significantly improved by the simple internal microstructures design, and the regression model established in this article can be used for accurate prediction of composites properties and the reliability is higher. In a word, this study opens a new route for the design of composites with unusual features.     

Additive manufacturing of mechanical testing samples based on virgin poly (lactic acid) (PLA) and PLA/wood fibre composites

3D printing in additive manufacturing is considered as one of key technologies to the future high-precision manufacturing in order to benefit diverse industries in building construction, product development, biomedical innovation, etc. The increasing applications of 3D printed components depend primarily on their significant merits of reduced weight, minimum used materials, high precision and shorter production time. Furthermore, it is very crucial that such 3D printed components can maintain the same or even better material performance and product quality as those achieved by conventional manufacturing methods. This study successfully fabricated 3D printed mechanical testing samples of PLA and PLA/wood fibre composites. 3D printing parameters including infill density, layer height and the number of shells were investigated via design of experiments (DoE), among which the number of shells was determined as the most significant factor for maximising tensile strengths of PLA samples. Further, DoE work evaluated the effect of material type (i.e., neat PLA and PLA/wood fibres) and the number of shells on tensile, flexural and impact strengths of material samples. It is suggested that material type is the only predominant factor for maximising all mechanical strengths, which however are consistently lower for PLA/wood fibre composites when compared with those of neat PLA. Increasing the number of shells, on the other hand, has been found to improve almost all strength levels and decrease infill cavities. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0211-3     

Surface modification and adhesion mechanisms in woodfiber-polypropylene composites

The interfacial adhesion between wood fiber and thermoplastic matrix polymer plays an important role in determining the performance of wood-polymer composites. The objectives of this research were to elucidate the interaction between the anhydride groups of maleated polypropylene (MAPP) and hydroxyl groups of wood fiber, and to clarify the mechanisms responsible for the interfacial adhesion between wood fiber and polypropylene matrix. The modification techniques used were bulk treatment in a thermokinetic reactive processor and solution coating in xylene. FT-IR was used to identify the nature of bonds between wood fiber and MAPP. IGC and wood veneer pull-out test was used to estimate the interfacial adhesion. Mechanical properties of injection molded woodfiber-polypropylene composites were also determined and compared with the results of esterification reaction and interfacial adhesion tests. Confocal Microscopy was employed to observe the morphology at the wood fiber-polypropylene interface, and the dispersion and orientation of wood fiber in the polypropylene matrix, respectively. The effectiveness of MAPP to improve the mechanical properties (particularly the tensile strength) of the composites was attributed to the compatibilization effect which is accomplished by reducing the total wood fiber surface free energy, improving the polymer matrix impregnation, improving fiber dispersion, improving fiber orientation, and enhancing the interfacial adhesion through mechanical interlocking. There was no conclusive evidence of the effects of ester links on the mechanical properties of the composites.     

Performance properties of microcrystalline cellulose as a reinforcing agent in wood plastic composites

Polypropylene (PP)/microcrystalline cellulose (MCC)/wood flour composites were prepared containing polypropylene-graft-maleic anhydride (PP-g-MA) as compatibilizer. The mechanical, morphological and thermal properties were investigated. The weight ratio of the cellulosic materials to polymer matrix was 40:60 (w:w). The obtained results showed that tensile, flexural and impact strengths of the composites were significantly enhanced with addition of MCC, as compared with pure PP and composites without MCC. The effect of MCC on impact was minimal compared to the effects of PP-g-MA content. Scanning electron microscopy has shown that the composite, with compatibilizer, promotes better fiber–matrix interaction. In all cases, the degradation temperatures shifted to higher values after addition of PP-g-MA. The maximum improvement on the thermal stability of the composites was achieved when 5% PP-g-MA was used. However, the increase in MCC content substantially reduced the thermal stability. This work showed that MCC along with wood flour could be effectively used as reinforcing agent in thermoplastic matrix.     

DHDOPO接枝改性多壁碳纳米管及其对聚乳酸性能的影响

首先将多壁碳纳米管(p-MWCNTs)用混合浓酸氧化成羧基化MWCNTs(MWCNTs-COOH),然后与氯化亚砜(SOCl_2)反应得酰氯化MWCNTs(MWCNTs-COCl);将9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)与二乙醇胺(DEA)反应制备DOPO的衍生物DHDOPO;再将DHDOPO与MWCNTs-COCl进行接枝反应得表面功能化的MWCNTs(MWCNTs-COO-DH);最后经熔融共混法制备聚乳酸(PLA)/MWCNTs-COO-DH复合材料。用核磁共振氢谱和透射电子显微镜表征MWCNTs-COO-DH的结构和微观形貌;用电子万能试验机、扫描电子显微镜、微型燃烧量热计等测定PLA/MWCNTs-COO-DH复合材料的力学性能、冲击断面形貌、燃烧性能及残炭层形貌。结果表明,实验成功合成了目标产物DHDOPO,并将其接枝到MWCNTs表面形成了典型核-壳结构的MWCNTs-COO-DH;适量的MWCNTs-COO-DH可均匀分散在PLA基体中形成良好的界面结合;质量分数为0.1%的MWCNTs-COO-DH可显著提高PLA的力学性能,并能降低其可燃性和火灾危险性。     

PLA/PBS荧光复合材料的制备及性能研究

目的 聚乳酸(PLA)具有良好的加工性能和生物相容性,通过加入耐热性能好的聚丁二酸丁二醇酯(PBS)可改善其力学性能和热力学性能,再加入365 nm长波荧光粉和色母粒制得的复合材料使其获得荧光防伪性能与色彩性能。方法 以聚乳酸为基体,利用双螺杆挤出机将PLA、PBS、荧光粉、普通色母熔融共混后挤出,得到含不同比例PBS的PLA/PBS共混材料,含不同比例荧光粉的PLA/PBS荧光复合材料,以及含不同比例色母的彩色PLA/PBS荧光复合材料,并对复合材料进行力学性能分析、热力学性能分析、红外分析、色彩性能分析、微观形貌分析等。结果 通过实验得出,当PLA/PBS质量比为6/4、荧光粉质量分数为5%、色母质量分数为0.5%时综合性能最佳。结论 制备了有色PLA/PBS荧光复合材料,赋予复合材料防伪的荧光性能和美观性,并且得到热力学性能有所改善的环境友好型复合材料,拓宽了PLA在3D打印领域和现代工业领域的应用。