纳米纤维素的表面修饰及对聚乳酸膜的力学性能和阻隔性能的影响

本实验通过化学水解法从农林废弃物油茶果壳中提取出油茶果壳纳米纤维素（cellulose nanocrystals, CNC）,经丁酸酐表面修饰获得丁酸酯化纳米纤维素（butyrated cellulose nanocrystals, BCNC）后,通过溶液浇铸法制备得到了BCNC/聚乳酸（PLA）复合材料,研究了CNC改性后的形貌及性能变化,以及BCNC对PLA力学性能、阻隔性能及透光率的影响。研究结果表明,经改性后,纳米纤维素的团聚现象得到改善并能稳定的分散在非极性有机溶剂中。在PLA复合材料中,BCNC对PLA有增强增韧的效果,添加5 wt%的BCNC时,PLA膜的拉伸强度提升了30.1%。添加5 wt%的BCNC,PLA复合膜的水蒸气透过率和氧气透过率分别下降了60.0%和35.0%,且仍具有较高的透光率。由于BCNC在基体中有更好的分散性和界面结合,对提升PLA力学性能和阻隔性能的效果均优于CNC。     

改性纳米纤维素/聚乳酸复合材料的制备及性能

通过化学酸水解法从农林废弃物油茶果壳中提取出纳米纤维素(CNC),并利用丁酸酐对CNC进行表面修饰,获得了丁酸酯化纳米纤维素(BCNC),再通过溶液浇铸法制备了BCNC/聚乳酸(PLA)复合材料。研究了CNC改性前后的形貌、性能变化以及BCNC对PLA膜力学性能、阻隔性能和透光率的影响。结果表明,经改性后,纳米纤维素的团聚现象得到改善并能稳定分散在非极性有机溶剂中。与纯PLA膜相比,当BCNC质量分数为5%时,PLA膜的拉伸强度提升了30.1%,水蒸气透过率和氧气透过率分别下降了60.0%和35.0%,且膜的透光率保持在60%以上。     

酰胺化纳米晶纤维素提高乙烯-醋酸乙烯酯共聚物薄膜阻透性的研究

合成了三种酰胺化纳米晶纤维素,并采用溶液共混成膜法制备了酰胺化纳米晶纤维素（CNC）/乙烯醋酸乙烯醋共聚物(EVA)复合膜材料。通过紫外-可见分光光度计、电子万能试验机和透湿仪研究了酰胺化CNC/ EVA复合膜的光学性能、力学性能以及水蒸气阻隔性,并通过原子力显微镜研究热压处理的EVA复合膜的表面形貌。结果表明,添加三种不同碳链的酰胺化CNC都使 EVA膜的透光率有所降低,当添加量为5 %时,EVA膜透光率仍高达90%。一定程度的热压能够让酰胺化纳米晶纤维素在EVA基体中分散更均匀,使EVA复合膜的透光率提高了2%～3%;随着纳米晶纤维素含量的逐渐增加,三种酰胺化CNC/EVA膜的拉伸强度均逐渐增强,透湿率（WVTR值）均减小;酰胺化CNC含量相同时, 十六胺改性的纳米晶纤维素(CNC-N16)/EVA复合膜的力学性能和水蒸气阻隔效果优于相应的十二胺和正辛胺。     

油茶果壳中纳米纤维素的分离与成膜性能

以茶籽油生产过程中的废弃物——油茶果壳为研究对象,首先采用亚硫酸盐预蒸煮实现纤维素、半纤维素和木素、茶皂素等组分的分离,然后经硫酸热水解得到油茶果壳纳米纤维素(CNC),最后压滤制得高强度透明薄膜。利用SEM、TEM、XRD、TG、UV-vis、电子万能试验机对纳米纤维素及其薄膜进行了结构表征与热学性能、光学性能、力学性能测试。结果表明,从油茶果壳中提取分离得到的纳米纤维素呈棒状,直径为6~10nm,长度为300~500 nm,属于纤维素Ⅰ型,结晶度为68%,热分解温度为230℃;压滤制备得到的纳米纤维素薄膜厚度为0.03 mm时,在600~800 nm波段处透光率为76%~81%,拉伸强度为75.6 MPa,可用于制备高强度的透明食品薄膜包装材料。     

海藻酸钠/CNC/山梨酸钾复合膜的制备及性能研究

以海藻酸钠为基材,纤维素纳米晶(CNC)为增强增韧剂,以山梨酸钾为防腐保鲜剂,采用流延法制备海藻酸钠/CNC/山梨酸钾复合膜。研究CNC、山梨酸钾的加入对海藻酸钠膜光学性能、力学性能、水蒸气阻隔性能等的影响。结果表明：随着CNC含量的增加,复合膜的透光率先增加后降低;添加山梨酸钾后,复合膜的透光率逐渐下降。CNC的加入使复合膜的拉伸强度和断裂伸长率均先提高后降低,水蒸气阻隔性能先降低后升高。随着山梨酸钾的添加,复合膜的拉伸强度逐渐降低,断裂伸长率先降低后增加,水蒸气阻隔性能先升高后降低。当CNC含量为5%、山梨酸钾含量为3%,复合膜的拉伸强度为120.78 MPa,断裂伸长率为4.38%,水蒸气透过系数为7.62×10^-13 g·cm/(cm²·s·Pa),与纯海藻酸钠膜相比,分别提高了21.66%、27.33%和17.59%,复合膜综合性能最佳。     

PLA协同纳米CaCO3增韧PP的研究

通过熔融共混制得聚丙烯/聚乳酸/纳米碳酸钙（PP/PLA/CaCO3）复合材料,考察了PLA和纳米CaCO3对复合材料力学性能、热性能、流变性能与结晶形态的影响及其作用机理。结果表明,复合材料中形成连续空间网络结构的PLA有助于改善PP的性能,PLA含量为20 %（质量分数,下同）时复合材料综合力学性能最佳;与纯PP相比,加入PLA后的复合材料拉伸强度和冲击强度分别提高5.1 %和54.4 %,断裂伸长率降低62.5 %;纳米CaCO3通过“滚珠增韧”和“异相成核”作用明显改善复合材料力学性能,纳米CaCO3含量15 %时产生的晶粒细化作用效果最为显著,复合材料综合力学性能达到最佳,拉伸强度、断裂伸长率和冲击强度分别比未添加CaCO3时提升了15.2 %、2.7 %和5.6 %。     

聚乳酸/纤维素纳米晶复合材料的制备与性能研究

研究了添加表面活性剂十二烷基三甲基氯化铵(DTAC)前后,纤维素纳米晶(CNC)在水体系中的分散,并采用溶液浇注法制备了聚乳酸(PLA)/CNC纳米复合材料。结果表明,有效减少了DTAC处理后的CNC(mCNC) 的团聚现象,PLA与mCNC间的相容性增强,并通过氢键产生较强的界面相互作用;mCNC能促进PLA的异相成核,提高复合材料的结晶度;mCNC的含量为2 %（质量分数,下同）时,PLA的拉伸强度提高了70.7 %,但断裂伸长率有所下降。     

聚乳酸基纤维素纳米晶体抗菌包装材料的制备及其性能研究

为改善聚乳酸(PLA)膜的力学性能、阻隔性能和抑菌性能,通过溶液浇铸法制备纤维素纳米晶体(CNC)和槐糖脂(SL)掺杂的PLA复合抗菌膜,探究SL含量(10%)不变时,CNC的含量对PLA/SL/CNC的力学性能、亲疏水性、水蒸气阻隔性和抑菌性能的影响。结果表明:PLA复合膜具有较好的透光性。CNC含量为8%时,CNC与PLA相容性较差。相比纯PLA,PLA/SL/CNC(6%)的拉伸强度高达68.6 MPa,提高93.8%;PLA/SL/CNC(6%)的韧性为36.5×10⁸J/m³,增加46%。PLA/SL/CNC(6%)水接触角为86°,具有疏水性。PLA/SL/CNC(6%)的水蒸气透过系数为2.4(g·cm)/(Pa·s·cm²),与纯PLA相比降低36.8%。PLA/SL/CNC(6%)与利斯特氏菌和金黄色葡萄球菌共培养24h,菌落数分别为0.8 lgCFU/mL和0.4 lgCFU/mL,具有较好的抑菌效果。     

再生纤维素/壳聚糖/银纳米线抗菌复合膜制备及性能

以1-丁基-3甲基咪唑氯盐（[Bmim]Cl）为溶剂体系，通过微晶纤维素（MCC）溶解再生制备基膜，壳聚糖（CS）、银纳米线（AgNW）共混液包覆方法制备抗菌复合膜，通过FTIR、XRD、SEM和热重分析对复合膜的形貌和结构进行表征及对力学、光学、阻隔、抑菌等性能测试分析。结果表明，壳聚糖和银纳米线成功复合于纤维素基膜，与再生纤维素膜相比，当AgNW质量分数为0.5%时，复合膜的拉伸强度提升了12.2%，透光率保持在89.82%，氧气透过率下降了86.7%，且对大肠杆菌具有良好的抑制作用，制备出一种力学性能、光学性能、阻隔性能、抗菌性能优异的可降解纤维素/壳聚糖/银纳米线抗菌复合膜。     

油茶果壳对PE-HD力学性能的影响

以废弃油茶果壳和高密度聚乙烯(PE-HD)为原料,采用挤出成型工艺制备了PE-HD/油茶果壳复合材料。采用热重法测试了油茶果壳的热稳定性,研究了油茶果壳平均粒径、添加量及相容剂马来酸酐接枝聚乙烯(MAPE)添加量对复合材料力学性能的影响。结果表明,油茶果壳初始热解温度为211℃,热解残炭率达31.35%。随着油茶果壳平均粒径减小、油茶果壳和MAPE添加量增加,复合材料的拉伸、弯曲和缺口冲击强度均呈现先增大后减小的趋势。当油茶果壳平均粒径为380μm,添加量为40份,MAPE添加量为3份时,复合材料的力学性能最佳。     

Development and characterization of bionanocomposites based on poly(3‐hydroxybutyrate) and cellulose nanocrystals for packaging applications

Poly(3‐hydroxybutyrate) (PHB)‐based bionanocomposites were prepared using various percentages of cellulose nanocrystals (CNCs) by a solution casting method. CNCs were prepared from microcrystalline cellulose using sulfuric acid hydrolysis. The influence of CNCs on PHB properties was evaluated using differential scanning calorimetry, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetry and tensile testing. Vapor permeation and light transmission of the materials were also measured. Differential scanning calorimetric tests demonstrated that CNCs were effective PHB nucleation agents. Tensile strength and Young's modulus of PHB increased with increasing CNC concentration. Moreover, the PHB/CNC bionanocomposites exhibited reduced water vapor permeation compared to neat PHB and had better UV barrier properties than commodity polymers such as polypropylene. It was found that nanocomposites with 6 wt% of CNCs had the optimum balance among thermal, mechanical and barrier properties. © 2016 Society of Chemical Industry     

Exploring the impact of cellulose nanocrystals and annealing treatment on the interlayer bond strength of polylactic acid 3D printed composites

The extrusion-based 3D printing process offers advantages, such as high precision, low cost, high speed, simplicity, and the ability to deposit multiple materials simultaneously. However, using 3D printing composite materials with orthogonal anisotropy can limit the interlayer bonding strength of printed parts. In this study, the interlayer tensile strength of 3D-printed polylactic acid (PLA) was affected by adding 0.5 wt% cellulose nanocrystals (CNC) and 1.2 wt% di-cumyl peroxide (DCP) to PLA, and annealing at low temperature (373 K, 1 h). The effects of annealing and CNC were determined by mechanical testing, scanning electron microscopy, differential scanning calorimetry, expansion testing, rheological testing, and x-ray diffraction analysis. After annealing, the interlayer gap increased due to crystal shrinkage, leading to a 25.9% decrease in tensile strength. However, the addition of CNC and DCP significantly improved the flow properties of the sample, resulting in better interlayer bonding and a 52.7% increase in tensile strength.     

Graphene Nanoplatelets as Novel Reinforcement Filler in Poly(lactic acid)/Epoxidized Palm Oil Green Nanocomposites: Mechanical Properties

Graphene nanoplatelet (xGnP) was investigated as a novel reinforcement filler in mechanical properties for poly(lactic acid) (PLA)/epoxidized palm oil (EPO) blend. PLA/EPO/xGnP green nanocomposites were successfully prepared by melt blending method. PLA/EPO reinforced with xGnP resulted in an increase of up to 26.5% and 60.6% in the tensile strength and elongation at break of the nanocomposites respectively, compared to PLA/EPO blend. XRD pattern showed the presence of peak around 26.5° in PLA/EPO nanocomposites which corresponds to characteristic peak of graphene nanoplatelets. However, incorporation of xGnP has no effect on the flexural strength and modulus. Impact strength of PLA/5 wt% EPO improved by 73.6% with the presence of 0.5 wt% xGnP loading. Mechanical properties of PLA were greatly improved by the addition of a small amount of graphene nanoplatelets (<1 wt%).     

Non‐isothermal crystallization behavior of PLA/acetylated cellulose nanocrystal/silica nanocomposites

Poly(lactide) (PLA)/acetylated cellulose nanocrystals (ACN)/silica nanocomposites were prepared by solution casting. Surface modification of cellulose nanocrystal (CNC) was performed to prepare the ACN. The ACN and silica were expected to act as a mechanical reinforcement of PLA and a nucleation agent, respectively, to increase the crystallization rate. Introduction of acetyl groups on the surface of the cellulose nanocrystals was confirmed by Fourier transform infrared spectroscopy. A combined Avrami ? Ozawa analysis described the non‐isothermal crystallization effectively. The activation energy for the crystallization was calculated from the Kissinger and the Takhor equations. Spherulite growth behavior was observed by polarizing optical microscope and spherulite growth rate, the number of spherulite versus crystallization time have investigated. The development of PLA crystals and the thermal stability had a tendency to improve with increasing silica content. Increased tensile strength was observed due to the reinforcement effect of ACN and the morphology of the nanocomposites was investigated. © 2015 Society of Chemical Industry     

Composites made from a soybean oil biopolyurethane and cellulose nanocrystals

Cellulose nanocrystals (CNC) obtained by acidic hydrolysis from microcrystalline cellulose were dispersed in a biopolyurethane matrix to prepare composite films. The polyurethane was prepared from a hydroxylated soybean oil (SO‐OH) and a polymeric diphenyldiisocyanate (pMDI), using a organotin compound as the catalyst. The composite films contained different concentrations of nanocelullose, without any macroscopic aggregates in all cases. Thermal, tensile and dynamic mechanical properties of the films were determined for all the samples. In particular, it was observed that the glass transition temperature of the nanocomposites slightly increased with the concentration of the cellulose nanocrystals. The nanocomposite with 1 wt% of nanocellulose showed the highest tensile strength of the series. POLYM. ENG. SCI., 58:125–132, 2018. © 2017 Society of Plastics Engineers     

Melt processing of nanocomposites of cellulose nanocrystals with biobased thermoplastic polyurethane

Nanocomposites of thermoplastic polyurethane (TPU) with cellulose nanocrystals (CNC) without and with surface treatment are obtained by melt processing. Nanocomposites are obtained with nanofiller weight content near of the theoretical percolation threshold (3.9 wt%). Visual observation of CNC agglomerates is sufficient to prove the inefficiency of the mixing in systems with untreated CNC. The crystallization kinetics of the TPU changes with the addition of CNC and this is confirmed by differential scanning calorimetry analysis. Thermogravimetric analysis prove that the addition of CNC increases the thermal stability of the TPU. From the rheological analysis it is possible to verify the absence of percolation and an intermediate state of sol–gel transition in the nanocomposites. CNC/TPU nanocomposites with 5 wt% of treated CNC present better mechanical performance than de neat TPU and the other processed nanocomposites and display around 130% increase in Young's modulus while retaining significant values of toughness, tensile strength and elongation at break.     

Morphology and properties tuning of PLA/cellulose nanocrystals bio-nanocomposites by means of reactive functionalization and blending with PVAc

A novel method for the preparation of PLA bio-nanocomposites containing cellulose nanocrystals (CNCs) is reported. In order to enhance interfacial adhesion and dispersion of nanocrystals into PLA matrix, functionalization of PLA and CNCs by radical grafting of glycidyl methacrylate (GMA) and pre-dispersion of CNCs in poly (vinyl acetate) (PVAc) emulsion were applied. Morphologies, thermal and mechanical properties of nanocomposites for CNCs content of 1–6 wt.% were examined. Addition of functionalized components (PLA-GMA, CNC-GMA) and/or PVAc dispersed CNCs both improved the phase distribution of nanofiller and tensile properties, compared to the binary PLA/CNC nanocomposites. Thermal analyses demonstrated that glass transition, melting temperature and crystallinity of PLA were affected by the PVAc amount. Nanocomposites with PVAc dispersed CNCs exhibited higher thermal resistance than other composites. The filler effectiveness (CFE) was evaluated for all samples on the basis of storage modulus values: CNC-GMA and PVAc dispersed CNCs (3 wt. %) resulted the most effective fillers.