红麻粉/聚丙烯复合材料性能研究

以聚丙烯(PP)为基体,选用两种红麻粉[包括红麻韧皮粉(KB)、红麻芯秆粉(KS)]分别作为填料,采用双螺杆挤出共混造粒及模压成型方法制备红麻粉/聚丙烯复合材料,测试了复合材料的力学性能并观察其微观结构,分析了KB与KS的含量对复合材料的力学性能的影响,以及采用硅烷偶联剂进行改性处理对红麻粉与聚丙烯基体之间的相容性的影响。结果表明:随着红麻粉含量的增加,复合材料的拉伸性能逐渐下降,弯曲强度则逐渐增加;当红麻粉质量分数达到20%时,KB/PP和KS/PP两种复合材料的弯曲强度都出现最大值,分别为41.33、39.29 MPa;红麻粉质量分数由5%增加到25%,复合材料的拉伸模量和弯曲模量不断增加,冲击强度则出现下降;采用硅烷偶联剂进行改性处理可以有效地改善红麻粉与聚丙烯基体之间的相容性。     

Nanocomposite Edible Films from Mango Puree Reinforced with Cellulose Nanofibers

ABSTRACT:  Cellulose nanoreinforcements have been used to improve mechanical and barrier properties of biopolymers, whose performance is usually poor when compared to those of synthetic polymers. Nanocomposite edible films have been developed by adding cellulose nanofibers (CNF) in different concentrations (up to 36 g/100 g) as nanoreinforcement to mango puree based edible films. The effect of CNF was studied in terms of tensile properties, water vapor permeability, and glass transition temperature ( T _g) of the nanocomposite films. CNF were effective in increasing tensile strength, and its effect on Young's modulus was even more noticeable, especially at higher concentrations, suggesting the formation of a fibrillar network within the matrix. The addition of CNF was also effective to improve water vapor barrier of the films. Its influence on T _g was small but significant. The study demonstrated that the properties of mango puree edible films can be significantly improved through CNF reinforcement.     

酸解淀粉/PBAT复合膜的制备及其性能研究

为了提高淀粉基复合膜的力学性能和阻水性能,以酸解淀粉和聚己二酸-对苯二甲酸丁二醇酯（PBAT）为主要成膜基材,通过挤出吹塑法制备了酸解淀粉/PBAT复合膜,研究了淀粉/PBAT比例对复合膜结构、力学性能和阻隔性能等的影响。结果表明,随着PBAT含量的增加,淀粉/PBAT共混物的流动性增强,模量与复合黏度降低,淀粉与PBAT之间的氢键作用减弱。添加PBAT可显著提高淀粉膜的力学性能和阻隔性能,复合膜纵向最大拉伸强度和断裂伸长率分别为7.86 MPa和532.67%,最低水蒸气和氧气透过系数分别为3.74×10?11 g?m?1?s?1?Pa?1和5.77×10?15 cm2?s?1?Pa?1。     

PLA/PBAT/CNTs-COOH防静电包装材料的制备与性能研究

可降解防静电包装材料在保留传统防静电材料性能的前提下,可完全生物降解,符合环保要求。为了制备具有优异力学和导电性能的可生物降解防静电包装材料,本研究先对碳纳米管(CNTs)进行羧基化,然后通过熔融共混法制备PLA/PBAT/CNTs-COOH复合材料。采用傅立叶变换红外光谱仪(FTIR)和差示扫描量热仪(DSC)对制备的复合材料的链结构和热性能进行表征,并且通过万能材料试验机、数字冲击试验机和多功能数据采集仪研究了复合材料的力学和导电性能。结果表明:将CNTs-COOH引入PLA/PBAT体系中,可在不降低拉伸强度的同时,有效提高冲击强度,降低表面电阻率,CNTs-COOH的最佳添加量为1wt%~1.5wt%。该PLA/PBAT/CNTs-COOH复合材料可用于静电敏感产品的防静电包装。     

表面改性处理对涤纶织物/聚氯乙烯复合材料界面性能的影响

为制备含磷无卤阻燃聚丙烯腈纤维,利用KOH 水溶液对丙烯腈（AH） 醋酸乙烯酯（VAc）无规共聚物（P（AN?co?VAc））纤维中的VAc单元进行选择性水解,再与O,O?二乙基磷酰氯进行磷酰化反应制得阻燃聚丙烯腈纤维。采用傅里叶变换红外光谱、差示扫描量热和热重分析法对阻燃纤维结构及热性能进行表征,利用扫描电子显微镜对阻燃聚丙烯腈纤维的炭残渣进行分析。结果表明：随水溶液pH值的升高,聚丙烯腈纤维中VAc单元迅速水解;聚丙烯腈纤维中VAc单元的存在使共聚纤维环化放热分解峰值温度增大,当VAc单元的质量分数为30%时,可达287℃,而阻燃聚丙烯腈纤维的该温度高达340℃;阻燃聚丙烯腈纤维在800℃ 时的炭残渣量高达48%以上,远高于共聚合聚丙烯腈纤维４１％的残炭量,具有良好的成炭性。     

Effects of Coir Fiber and Maleic Anhydride Modification on the Properties of Thermoplastic Starch/PLA Composite Laminates

Coir fiber reinforced composite laminates made of poly(lactic acid) (PLA) with a thermoplastic starch (TPS) were fabricated. Modified thermoplastic starch (MTPS) was prepared by reactive blending of TPS with maleic anhydride (MA). The effect of coir fibers was of our main interest. The tensile properties, water absorption, and morphological properties of the fabricated composite laminates were investigated. The composite laminates between PLA and starch TPS were prepared using coir fiber as reinforcing core, and the physical, mechanical, and morphological properties were studied. The results suggested that the optimum fiber contents for maximum tensile strength for TPS/PLA and MTPS/PLA composites were 20 and 30 wt%, respectively. Using MA for chemical modification of TPS for PLA composites could reduce the PLA content of about 10 wt%, and improve the tensile about 20%. The volume swelling for the MTPS/PLA composites was much lower than that for the TPS/PLA composites, and the swelling reduced with increasing coir fiber content. Based on compressive strength, the pallets produced using MTPS/PLA composites showed a high potential to replace the commercial urea-formaldehyde/PLA composites. It clearly appeared that MA modification to TPS not only improve the mechanical properties of fiber reinforced PLA composites, but also made the PLA composites bio-degrade more quickly.     

电泳沉积碳纳米管和氧化石墨烯修饰碳纤维表面的研究进展

针对碳纤维表面极性官能团少,化学活性低,与基体间的界面结合强度弱等问题,综述了国内外关于电泳沉积碳纳米管和氧化石墨烯修饰碳纤维提高其复合材料力学性能的最新研究进展。阐述了在不同的电泳沉积工艺下,分别在碳纤维表面引入碳纳米管和氧化石墨烯,对修饰碳纤维表面及其复合材料力学性能的影响。总结了影响电泳沉积修饰碳纤维效果的因素,并提出了相应的建议。展望了电泳沉积修饰碳纤维表面的研究发展方向,指出对碳纤维、碳纳米管和氧化石墨烯进行预处理,添加辅助工艺的电泳沉积设备制造将会成为未来的重要研究方向。     

生物可降解聚己二酸-对苯二甲酸丁二醇酯纤维的制备及其环境降解性能

为研究生物可降解聚己二酸-对苯二甲酸丁二醇酯(PBAT)的可纺性及纤维降解性能,采用熔融纺丝-牵伸二步法制得生物可降解PBAT纤维,研究了纺丝温度、牵伸倍数对PBAT纤维结晶度、回潮率、力学性能的影响,对比分析了PBAT纤维在不同环境下的降解性能.结果 表明:PBAT的最佳纺丝温度为260℃,且随着牵伸倍数的增加,PB...     

紫外照射下聚己二酸/对苯二甲酸丁二醇酯/纳米复合膜的性能和纳米成分的迁移

为探究紫外光（ultraviolet,UV）照射对聚己二酸/对苯二甲酸丁二酯（poly (butyleneadipate-co-terephthalate),PBAT）的影响,本实验研究了PBAT/纳米ZnO和PBAT/纳米TiO2复合膜的性能及纳米成分在UV照射前后向3 g/100 mL乙酸溶液迁移的情况,并通过衰减全反射傅里叶变换红外光谱、场发射扫描电子显微镜、X射线衍射表征并分析变化原因。结果表明,未经UV照射时,两种纳米颗粒的加入对复合膜阻隔性的影响较小,纳米ZnO使复合膜的拉伸强度下降22.88%～40.99%,断裂伸长率下降至纯PBAT的86.07%～90.98%,最大迁移量为11.82 mg/kg。纳米TiO2的加入对复合膜的拉伸强度影响较小,断裂伸长率下降至纯PBAT的73.48%～87.18%,未检测到其迁出（方法检出限为0.009 mg/kg）。随UV照射时间延长,复合膜的断裂伸长率和拉伸强度均逐渐降低,但相同照射时间下,PBAT/纳米ZnO力学性能的下降程度低于纯PBAT和PBAT/纳米TiO2。在UV照射2 d后,复合膜的透氧系数显著增大（P＜0.05）,透湿系数变化较小;纳米ZnO的最大迁移量为16.66 mg/kg,而仍未检测到纳米TiO2迁出;且复合膜酯键断裂,结晶度降低,表面变得粗糙,产生破裂的孔洞。综上,UV照射破坏了PBAT纳米复合膜的结构,使其性能降低,纳米ZnO可在一定程度上抑制复合膜力学性能的下降,但其迁移量会逐渐增加。     

Thespesia populnea Reinforced Cashew Nut Husk Tannin-Based Polyurethane Composites

Polyurethane composites were prepared by reinforcing raw and silane treated Thespesia populnea fibers in random orientations at different fiber length and loadings with polyurethane. The matrix phase is bio- polyurethane (PU1 and PU2), prepared from tannin extracted from Cashewnut husk with Hexamethylene diisocyanate in the absence and presence of extender. Surface modification was carried out with vinyltriethyl silane as coupling agent. Tensile, compression and moisture absorption properties of the composites were evaluated and fiber properties analysed. Results showed that composites had better mechanical properties compared to the non reinforced matrix. Composites from PU1 had better mechanical properties compared to that of PU2. Tensile and compression strength decreased with increase in fiber content in the matrix. PU1 based composites had less moisture absorption than PU2 based composites and the amount of absorption increased with increase in fiber length. The paper suggests that Thespesia populnea fibers have immense scope as reinforcement in the composite industry.     

Nanocellulose Reinforced Chitosan Composite Films as Affected by Nanofiller Loading and Plasticizer Content

ABSTRACT: Chitosan is a biopolymer obtained by N-deacetylation of chitin, produced from shellfish waste, which may be employed to elaborate edible films or coatings to enhance shelf life of food products. This study was conducted to evaluate the effect of different concentrations of nanofiller (cellulose nanofibers, CNF) and plasticizer (glycerol) on tensile properties (tensile strength—TS, elongation at break—EB, and Young's modulus—YM), water vapor permeability (WVP), and glass transition temperature (T_g) of chitosan edible films, and to establish a formulation to optimize their properties. The experiment was conducted according to a central composite design, with 2 variables: CNF (0 to 20 g/100 g) and glycerol (0 to 30 g/100 g) concentrations in the film (on a dry basis), which was produced by the so-called casting technique. Most responses (except by EB) were favored by high CNF concentrations and low glycerol contents. The optimization was based on maximizing TS, YM, and T_g, and decreasing WVP, while maintaining a minimum acceptable EB of 10%. The optimum conditions were defined as: glycerol concentration, 18 g/100 g; and CNF concentration, 15 g/100 g. AFM imaging of films suggested good dispersion of the CNF and good CNF-matrix interactions, which explains the good performance of the nanocomposite films. Practical Application: Chitosan is a biodegradable polymer which may be used to elaborate edible films or coatings to enhance shelf life of foods. This study demonstrates how cellulose nanofibers (CNF) can improve the mechanical and water vapor barrier properties of chitosan films. A nanocomposite film with 15% CNF and plasticized with 18% glycerol was comparable to some synthetic polymers in terms of strength and stiffness, but with poorer elongation and water vapor barrier, indicating that they can be used for applications that do not require high flexibility and/or water vapor barrier. The more important advantage of such films when compared to synthetic polymer films is their environmentally friendly properties.     

Influence of chemical modification of wood on the crystallisation of polypropylene

The mechanical properties of wood/polypropylene composites depend strongly on interfacial adhesion between components. However, the application of chemical modification to improve compatibility can influence the supermolecular structure of polypropylene matrix. The experimental material comprised two most common Polish timber species pine wood (Pinus silvestris L.) as a softwood species and beech wood (Fagus silvatica L.) as a hardwood species. The size of wood sawdust ranged from 0.5 to 1.0 mm. Three different types of wood/PP mixture were prepared: (1) PP – untreated wood, (2) PP – NaOH treated wood and (3) PP – esterified wood with maleic anhydride. In this work, the kinetic parameters of crystallization of PP by differential scanning calorimetry were investigated. It is interesting that crystallisation of PP depends on the kind of wood. The chemical treatment of wood caused changes of crystal conversion and half crystallisation time of polypropylene matrix.     

Composites from Bast Fibres-Prospects and Potential in the Changing Market Environment

Abstract

Composite materials reinforced with natural fibres, such as flax, hemp, kenaf and jute, are gaining increasing importance in automotive, aerospace, packaging and other industrial applications due to their lighter weight, competitive specific strength and stiffness, improved energy recovery, carbon dioxide sequestration, ease and flexibility of manufacturing and environmental friendliness besides the benefit of the renewable resources of bast fibres. The market scenario for composite applications is changing due to the introduction of newer biodegradable polymers, such as PLA synthesized from corn, development of composite making techniques and new stringent environmental laws requiring improved recyclability or biodegradability for industrial applications where stress bearing capacities and micro-mechanical failures dictate serviceability. Bast fibre reinforced composites, made from biodegradable polymers, will have to compete with conventional composites in terms of their mechanical behaviour. Biocomposites, in which natural fibres, such as kenaf, jute, flax, hemp, sisal, corn stalk, bagasse or even grass are embedded in a biodegradable matrix, made as bioplastics from soybean, corn and sugar, have openedup new possibilities for applications in automotive and building products. Obviously, new approaches to research and development will be required to improve their mechanical properties, such as tensile, bending and impact resistance to match their performance and commercial competitiveness against petroleum based products. The research community has to look at the various possibilities of combining natural fibres, such as sisal, flax, hemp and jute with polymer matrices from non-renewable and renewable resources to develop cost effective biocomposites. This paper will review the newer products and techniques that can improve the properties of bast fibre based composites as well as potential structural and non-structural applications which can increase their market share.     

Preliminary study of the stiffness enhancement of wood–plastic composites using carbon nanofibers

Vapor-grown carbon nanofibers (CNFs) were compounded into polypropylene (PP) with southern pine wood flour (WF) by high shear melt blending to investigate the reinforcement effects of CNFs on the stiffness of conventional wood flour/plastic composites. CNF loadings of 1, 2 and 5 parts by weight per 100 parts of PP were employed with three WF levels (20, 40 and 60 parts). Maleated polypropylene (MAPP) was used as a coupling agent to improve WF to PP compatibility. The incorporation of CNFs significantly increased the modulus of elasticity of these nanocomposites with MAPP addition. The presence of 0.61 wt?% of CNF within a 36.6%WF/1.83%MAPP/61%PP composite exhibited a modulus (7590 MPa) that was 59% greater than its counterpart without CNF (36.8%WF/1.84%MAPP/61.4%PP) (4783 MPa) and 90% greater than pure PP. The origin of this enhancement is not yet understood.     

A new assessment on mechanical properties of jute fiber mat with egg shell powder/nanoclay-reinforced polyester matrix composites

ABSTRACT

Natural fiber polymer matrix composites occupy the major percentage in applications due to its ecofriendly and low-cost nature. This study investigates the mechanical properties of a polyester matrix nanocomposite reinforced by the NaOH-treated jute fabric mat (NJM) and untreated jute fabric mat (UJM). In addition, the effects of egg shell powder (ESP) and nanoclay (NC) to the above has also been studied. The matrices were prepared with different combinations of presence and absence of the ESP, NC, and both as well as different weight percentage using compression molding process. The mechanical and morphological properties of the composites were determined. The tensile strength, flexural strength, and impact strength of NJM with NC 1.5%wt and ESP 1.5%wt were found to be 29.28 MPa, 39.51 MPa and impact strength 3.03 J, respectively. This composition is superior to the other compositions. Morphological analysis of tensile fractured surface showed interfacial adhesion between UJM and NJM composites. NJM composites contained smaller amount of pullouts and the splits compared with the UJM composites, which hold up the better performance.     

亚麻分层纳米纤维素的制备及其增强热电复合材料性能

为从天然亚麻纤维中制备出分层纳米纤维素(即纤维素纳米纤维(CNF)与纤维素纳米晶(CNC)共存),并对其制备方法进行优化完善,提出将亚麻纤维在特定浓度的氢氧化钠溶液中碱化处理后,再进行四甲基哌啶氮氧化物(TEMPO)介导的三元氧化和机械处理的联合处理方法。然后将亚麻CNF与石墨烯复合制备CNF/石墨烯复合薄膜并研究亚麻CNF增强热电复合材料的性能。结果表明:碱化预处理使亚麻纤维直径变细,长度变短,半纤维素被脱除,是生成不同尺寸CNF的重要步骤;随着氢氧化钠用量在0~18%范围内的增加,所得CNF悬浮液的光透过率从3.7%增加到95.1%;CNF/石墨烯复合膜表现出最高功率因子,为8.0×10 ^-3 μW/(m·K ²),表明复合薄膜具有热电性能。     

Natural Fibers from Plantain Pseudostem (Musa Paradisiaca) for Use in Fiber-Reinforced Composites

Agricultural crops from plantain produce a significant amount of wastes and they are currently considered worthless. Accordingly, in this study, non-wood fibers from pseudostem of plantain plants were extracted through mechanical processing to be used as reinforcing material in polyester composites. Bio-based composites were obtained using a 4% wt. of lignocellulosic reinforcement and were prepared after the fibers underwent alkaline and acetylation treatments in order to enhance the compatibility of organic loads with the polyester matrix. The higher cellulose content of plantain fibers indicates that they can be used to reinforce composites with a polymeric matrix. The plantain fibers have bast fiber bundle of around 120 µm; single fibers of around 5 µm; and mesofibers with a diameter between 0.5 and 1 µm. The results showed that plantain fibers can be used as a filler material to obtain an alternative polymer composite. The flexural strength of composites (polyester with acetylated plantain fibers) was improved 28% when the properties are compared to control composite.     

聚丙烯和PBAT树脂共混薄膜对金针菇的贮藏保鲜效果

本研究选择具有耐化学性、耐热性、高强度机械性能和高耐磨加工性能的聚丙烯（PP）作为基材与具有较高的透湿性的生物可降解材料PBAT树脂进行共混,共混后选用改性效果最好的比例（PP80%/PBAT20%）制成PPT2共混薄膜,对金针菇进行PPT2真空包装和PPT2密封包装,通过对比无包装空白组、市场包装组、PPT2密封组和PPT2真空组后,发现无包装组在第3 d时出现萎蔫腐烂现象失去食用价值,市场包装组在18 d时可溶性固形物含量下降并在包装袋上出现结露和涨包现象失去食用价值,PPT2密封包装组由于前期对气氛控制不稳定,呼吸旺盛时可溶性固形物含量出现骤然上升的假象。PPT2真空包装组金针菇失重率、Vc含量变化、可溶性固形物含量下降的比较平缓,未出现涨包结露等现象,保存至27 d时才出现萎蔫腐烂现象失去食用价值,保鲜效果与其它三组相比较为优异。因此,PPT2共混薄膜结合真空包装能有效控制金针菇后生长引起的菌柄伸长现象,从而延长货架期。     

Effect of alkali treatment on mechanical properties of the green composites reinforced with milkweed fibers

Polymeric composites disadvantages in terms of high price and non-recoverability make them unsuitable for some applications. Otherwise, natural fibers would be degraded easily and their prices are much lower as compared with most of the commonly used synthetic fibers, especially in composite manufacturing. Hollow Milkweed fiber with non-crimped nature is a known natural fiber which could have high potential to be used as composites reinforcements due to its low-density property. Increasing demand for natural fiber-reinforced composites as well as unique characteristics of Milkweed fibers reveal the need to study the mechanical properties of such fiber-reinforced composites. In this study, milkweed fibers were initially fed to laboratory carding machine in order to be formed as a nonwoven layer which was then applied to a low-velocity needle-punching operation. Surface modifications were carried out on the needle-punched nonwovens using 5% NaOH at 50–60 °C and three different treating time levels (30, 60 and 90 min). The produced nonwovens were then treated in a mixture of boiling water and detergent for 1 h. For making composite parts, the modified nonwovens were impregnated in Ploy vinyl acetate (PVAc) resin using the hand-layup method. The alkali treatment effects regarding the process time period on mechanical properties of the natural-reinforced composites were investigated. The findings suggested significant affectability of the composites mechanical properties by varying the time of alkali treatment, NaOH concentration as well as the type of surface modification process which are all mainly resulted in improving the interaction between fibers and matrix phase.     

纤维素纳米纤维/纳米蒙脱土复合气凝胶制备及其结构与性能

针对纤维素纳米纤维(CNF)气凝胶易燃、强力低等问题,利用纳米蒙脱土(MMT)共混改性纤维素纳米纤维,基于冷冻干燥的方法制备阻燃隔热的CNF/MMT复合气凝胶。研究了MMT质量分数对CNF/MMT复合气凝胶形貌结构、压缩性能、热稳定性、热导率和阻燃性能的影响。结果表明:MMT的引入使气凝胶具有更加紧密的片层结构,气凝胶力学性能、热稳定性和阻燃性能得到改善;在MMT质量分数为50%时,CNF/MMT复合气凝胶的表观密度最大且仅为0.016 8 g/cm³,应变为10%的应力最大为12.45 kPa,应变为70%的应力最大为77.93 kPa,导热系数最大为 0.04 W/(m·K); 气凝胶中MMT质量分数不低于42.9%时,复合基气凝胶的极限氧指数得到明显提升。