碱处理对剑麻纤维增强聚乳酸可降解复合材料性能的影响

以剑麻纤维(SF)和聚乳酸(PLA)为原料,通过注塑成型工艺制备了剑麻纤维增强聚乳酸可降解复合材料。研究了连续碱处理剑麻纤维(CASF)和未改性处理剑麻纤维(USF)在不同含量时对复合材料力学性能、吸水性及可降解性能的影响。结果表明:剑麻纤维的质量分数会显著影响复合材料的力学性能、吸水性和降解性能。相较于未改性处理剑麻纤维(USF),碱处理剑麻纤维(CASF)可以进一步提高复合材料的力学性能,降低复合材料的吸水率,延缓剑麻纤维增强可降解树脂基复合材料的降解速率,且酶降解法相较于土埋法降解能够显著加快复合材料的降解速率。当剑麻纤维含量为20%时,CASF/PLA复合材料的拉伸强度、弯曲强度和弯曲模量相较于纯PLA和USF/PLA分别提高了32.71%、10.08%;19.63%、12.11%;97.33%、12.40%;其冲击强度相较于纯PLA提高了71.19%。     

改性剑麻纤维增强聚乳酸复合材料热性能研究

依据丙交酯配位开环反应原理,在剑麻纤维表面接枝上聚乳酸分子支链进行表面改性,并与未处理、碱处理表面改性对比,研究了表面改性方法对剑麻纤维热性能的影响。使用熔体共混模压成型工艺制备了改性剑麻纤维增强聚乳酸复合材料,并研究了不同表面改性方法对复合材料热性能的影响。结果表明,剑麻纤维的加入使得复合材料的热稳定性略有降低,其中碱处理略高于未处理,而接枝处理降幅最大。同时,纤维的加入有利于复合材料异相成核,提高结晶度,其中以接枝剑麻纤维的促进作用最为突出。     

热处理剑麻/PLA复合材料的制备与力学性能研究

采用真空干燥箱对剑麻纤维进行预处理,并与聚乳酸(PLA)复合制备了剑麻纤维含量为50%的全降解环保型复合材料。研究了真空条件下剑麻纤维热处理温度、热处理时间对剑麻纤维成分、结构和复合材料性能的影响,并通过红外光谱和扫描电镜分析其作用机理。结果表明:在真空条件下,热处理使剑麻结构发生变化,半纤维素降解,改善了界面结合能力,且适宜的热处理温度、热处理时间有利于复合材料力学性能的提高。     

聚乳酸/剑麻复合材料流变性能表征

利用转矩流变仪测量流变特性的方法,表征了不同剑麻纤维含量下,聚乳酸(PLA)/剑麻复合材料的流变性能,并测量实验后纤维的长度和宽度、PLA分子量,分析剑麻纤维含量和转速对复合材料体系中纤维长度的影响,以及PLA降解情况。结果表明,复合材料的非牛顿指数在纤维含量为10%左右出现峰值,并进一步随含量的增加而减小。复合体系中,刚性剑麻纤维受到来自于转子、聚合物和纤维之间的作用力,纤维被剪短,长径比减小;聚乳酸会受到转速和纤维含量的影响发生降解,这些因素都会影响PLA/剑麻复合材料的流变性能。     

聚乳酸/芦苇纤维复合材料降解性能研究

采用熔融共混法制备了不同比例的聚乳酸/芦苇纤维（PLA/RF）共混物,并通过吹塑制备了相对应的薄膜。研究了在蛋白酶K的作用下不同RF含量的PLA/RF薄膜的生物降解性能,同时用差示扫描量热法（DSC）和扫描电子显微镜（SEM）测定了样品降解过程中的结晶行为以及表面形貌变化。结果表明,RF对PLA的酶解降解有促进作用,随着RF含量的增加PLA/RF复合材料的酶解速率提升,其中含有30 %（质量分数,下同）芦苇纤维的PLA/RF薄膜的降解速率最大,16天内可降解81.11 %。研究还表明,加入芦苇纤维可以降低PLA的结晶度,从而影响降解速度。     

取向长剑麻纤维增强聚乳酸层压复合材料力学性能的研究

通过溶液浸渍法制备剑麻纤维预浸渍料,然后通过热压成型的方法制备了纤维含量(质量分数)分别为10%、20%、30%和40%的取向长剑麻纤维增强聚乳酸层压复合材料,同时制备了随机取向的短剑麻纤维增强聚乳酸复合材料。研究了不同的纤维含量对取向长剑麻纤维增强聚乳酸层压复合材料力学性能的影响。结果表明,当纤维含量为40%时,复合材料的力学性能最好。其拉伸强度、弯曲强度以及冲击强度比纯聚乳酸分别提高了1.90、1.29以及15.69倍,比短纤维剑麻纤维增强聚乳酸分别提高了4.47、2.27以及10.73倍,达到了164.76、202.88 MPa以及36.72 k J/m~2。     

二恶唑啉改性剑麻纤维增强聚乳酸复合材料的制备及性能研究

以二恶唑啉(BO)为扩链剂,通过反应加工的方法对剑麻纤维进行界面改性,然后通过热压成型的方法制备了在不同的BO含量下,纤维质量分数分别为10%、20%、30%和40%的短剑麻纤维增强聚乳酸复合材料。研究了BO含量和剑麻纤维含量对短剑麻纤维增强聚乳酸复合材料力学性能的影响。研究结果表明,当纤维质量分数为30%、BO质量分数为1.0%时,所制备的复合材料力学性能最佳。其拉伸强度、弯曲强度以及冲击强度分别为66.76、117.09 MPa和4.61 kJ/m~2,比同样质量分数下,未加BO时剑麻纤维增强聚乳酸复合材料分别提高了34.4%、23.3%和19.1%。     

剑麻纤维/玄武岩纤维混杂增强聚乳酸复合材料的力学性能研究

混杂纤维增强复合材料由于可以综合利用各种纤维的优点,极大地提高复合材料的性能,拓展复合材料的适用范围。采用剑麻纤维和玄武岩纤维混杂增强聚乳酸制备复合材料,研究了纤维含量和铺层顺序对混杂纤维复合材料力学性能的影响。结果表明,剑麻纤维作为芯层、玄武岩纤维作为表层时混杂复合材料具有较好力学性能。当纤维质量分数为40%时,其拉伸强度和冲击强度比纯聚乳酸分别提高了2.83倍、41.47倍,达到了267.29 MPa和183.46k J/m~2;纤维含量为30%时,其弯曲强度比纯聚乳酸提高4.07倍,达到354.16 MPa。     

SBS/PS/剑麻纤维复合材料的制备及性能研究

通过熔融共混的方法制备了丁苯热塑性弹性体/聚苯乙烯/剑麻纤维(SBS/PS/SF)复合材料。采用SBS/PS=70/30的配比,通过改变剑麻纤维用量,研究SBS/PS/SF复合材料的力学性能、热性能及熔体流动速率。结果表明:随着剑麻纤维用量的增加,SBS/PS/SF复合材料的弹性模量和弯曲强度都有所增加;熔体流动速率呈减小趋势;拉伸强度、断裂应变、屈服应变和冲击强度先上升后下降;SBS/PS/SF复合材料的维卡软化点随着剑麻纤维的加入也有着不同程度的下降。     

剑麻预处理对热塑性淀粉复合材料力学性能及降解性能的影响

采用碱、蒸汽爆破等对剑麻纤维进行预处理,考察了不同预处理方法对剑麻纤维增强热塑性淀粉力学性能及降解性能的影响。结果表明:碱处理能够提高复合材料的力学性能,延长材料降解周期,是制备剑麻纤维增强热塑性淀粉复合材料有效的预处理方法;剑麻纤维增强热塑性淀粉的机理是甘油在淀粉及剑麻纤维之间起到桥梁作用,提高了热塑性淀粉与剑麻纤维的界面结合力,从而提高了复合材料的力学性能。     

Preparation and properties of L‐lactide‐grafted sisal fiber–reinforced poly(lactic acid) composites

Pretreatment of the sisal fiber (SF) grafting with L‐lactide (LA) monomer via a ring‐opening polymerization catalyzed by a Sn(II)‐based catalyst was performed to improve the interfacial adhesion between SF and poly (lactic acid) (PLA). Biocomposites from LA‐grafted SF (SF‐g‐LA) and PLA were prepared by compression molding with fiber weight fraction of 10, 20, 30, and 40%, and then were investigated in contrast with alkali‐treated sisal fiber (ASF) reinforced PLA composites and untreated SF reinforced PLA composites. PLA composites reinforced by half‐and‐half SF‐g‐LA/untreated SF (half SF‐g‐LA) were prepared and studied as well, considering the disadvantages of SF‐g‐LA. The results showed that both the tensile properties and flexural properties of the SF‐g‐LA reinforced PLA composites were improved noticeably as the introduction of SF‐g‐LA, compared with pure PLA, untreated SF reinforced PLA composites and ASF reinforced PLA composites. The mechanical properties of the half SF‐g‐LA reinforced PLA composites were not worse, even better in some aspects, than the SF‐g‐LA reinforced PLA composites. Fourier transform infrared analysis and differential scanning calorimetry analysis exhibited that both the chemical composition and crystal structure of the SFs changed after LA grafting. In addition, the fracture surface morphology of the composites was studied by scanning electron microscopy. The morphological studies demonstrated that a better adhesion between LA‐grafted SF and PLA matrix was achieved. POLYM. COMPOS., 37:802–809, 2016. © 2014 Society of Plastics Engineers     

Effect of initial fiber length on the rheological properties of sisal fiber/polylactic acid composites

The rheological properties of sisal fiber (SF)/polylactic acid (PLA) composites of different SF content and initial fiber length were evaluated using a torque rheometer. Since the SF configuration directly affected the rheological properties of the composites, the length and width of SFs in the final composites were measured. The effect of fiber content, angular velocity, and initial fiber length on the fiber aspect ratio (length to width ratio) and composite rheological properties were analyzed. Initial fiber length significantly affects the rheological properties of SF/PLA composites at low SF content, while fiber content predominantly affects rheological properties at high SF content, and rheological parameters are similar for the composites of different initial fiber length. The average shear stress and mixing temperature are affected by feeding speed for composites of very high SF content. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

蒸汽爆破预处理PLA/剑麻复合材料的性能研究

对剑麻纤维(SF)进行蒸汽爆破预处理,并与可生物降解材料聚乳酸(PLA)经模压成型制备降解复合材料,研究了混炼温度、SF含量及蒸汽爆破预处理对复合材料力学性能的影响,并通过X射线光电子能谱(XPS)和扫描电子显微镜(SEM)分析了其作用机理.结果表明,蒸汽爆破预处理可提高SF纤维素的含量,增大纤维的比表面积,使复合材料...     

Degradation of wheat straw/polylactic acid composites with and without sodium alginate in natural soil and the effects on soil microorganisms

In order to improve the degradability of polylactic acid (PLA) composites and screen PLA degradation microorganisms. Sodium alginate was added into the wheat straw/PLA composites, and both composites (with/without sodium alginate) were buried in natural soil for 100 consecutive days subsequently. Weight loss and characterization of the PLA composites, carbon and nitrogen content in soil and microbial community composition were detected after degradation, with the result that the degradability of the PLA composites was greatly improved after the addition of sodium alginate. The weight loss of PLA composites with sodium alginate was 8.5%, which was 1.81 times that of PLA composites without sodium alginate. Sodium alginate and/or wheat straw in the PLA composites took the lead in the beginning course of the degradation. The added sodium alginate serves the purpose of making it easier to degrade the crystallization zone of the PLA composites. Bionectriaceae in the soil shoots up in the number after degradation, signifying its potential to be part of the microorganism family serving to degrade PLA composites. The results would help reveal the degradation mechanism of PLA composites and provide support for the screening of PLA composites degradation microorganisms.     

Effect of phosphorus–nitrogen compound on flame retardancy and mechanical properties of polylactic acid

A phosphorus-nitrogen flame retardant (PN) was synthesized by using cytosine and diphenylphosphinic chloride. The flame retardancy and thermal stability of polylactic acid (PLA)/PN composites were investigated by the UL-94 vertical burning test, limited oxygen index (LOI), cone calorimeter test, and thermogravimetric analysis. The PN performs efficiently on improving the flame retardancy of PLA. The PLA composite achieves the UL-94 V-0 rating and its LOI increases to 30.4 vol% by adding 0.5 wt% PN. The flame retardant mechanism analysis showed that PN catalyzes the degradation of PLA to improve the flame retardancy by melting-away mode. Meanwhile PN reduces the release of flammable gasses during thermal degradation of PLA by promoting the transesterification of PLA, which is helpful for extinguishing flame. Moreover, triglycidyl isocyanurate (TGIC) was used as a micro-crosslinking agent to reduce the loss of mechanical properties of PLA/PN composites caused by degradation. Adding 0.1 wt% TGIC and 1.0 wt% PN into PLA, the tensile strength and elongation at break of PLA/PN are increased to the same level as that of PLA. Therefore, PLA with excellent comprehensive performance can be obtained.     

Reinforcing effect of nanocrystalline cellulose and office waste paper fibers on mechanical and thermal properties of poly (lactic acid) composites

Nanocrystalline cellulose (NCC) was prepared from office waste paper (OWP) by sulfuric acid hydrolysis method in this paper and it was used to prepare a series of poly (lactic acid) PLA/NCC composites by using a dissolution method in solvent N, N-dimethylformamide solution. The results indicated that with the addition of only 3 wt% NCC, the composites exhibited outstanding mechanical property. The tensile, bending and impact properties of the PLA/3NCC composite were improved by 8.2%, 13.1%, and 35.9% than those of pure PLA, respectively. On this basis, office waste paper fibers (OWF) were also used as a physical blended filler to enhance PLA/NCC composites to reduce the preparation cost of PLA composites and the perfect PLA/NCC/OWF sample was easily manufactured by melting–blending and injection molding. According to the crystallization and melting performance table, both NCC and OWF can act as nucleating agent to promote the crystallization properties on composites, while the blends did not have positive effect on thermal stability. Furthermore, the water absorption and degradation properties of PLA composites were also studied. This work not only provided a novel idea for the utilization of office waste paper but also successfully produced environment friendly composites with favorable mechanical properties and crystallization performance.     

聚乳酸/聚丙烯/淀粉复合材料的制备及性能研究

采用模压成型制备了聚乳酸(PLA)/聚丙烯(PP)和PLA/PP/淀粉两种复合材料。主要研究了复合材料的热性能、力学性能和降解性能。结果表明:对于PLA/PP复合材料而言,复合材料的熔融温度先增加后降低,结晶度随PLA的含量增加而变大,而且出现了结晶双峰。力学性能相较与纯PLA,断裂伸长率明显提高,拉伸强度有所下降,最大下降28.02 MPa。降解性能随PLA增加而增强。而对于PLA/PP/淀粉复合材料,熔融温度变为先降低后增加的趋势,复合材料的玻璃化温度也减小,材料的可塑性得到提高;在PLA/PP比例相同条件下,PLA的结晶度有明显提高,PLA的结晶峰强度增加。对于力学性能,淀粉的加入,明显降低了其拉伸强度和断裂伸长率,PLA与PP质量比为3/7时,表现出硬而韧的特性,材料具有单向拉伸,不会立即脆断。对于材料降解性能,淀粉的存在对复合材料的降解能力得到明显的提高,当PLA与PP质量比为3/7时,材料的降解率最高为14.78%,是PLA/PP复合材料最大降解率的4.3倍,并且材料上出现了黄褐色斑点。     

Enhancing the durability of poly(lactic acid) composites by nucleated modification

Biodegradable poly(lactic acid) (PLA) composites were prepared using an innovative combination of wood fiber (WF) and 1,3,2,4‐bis(3,4‐dimethylobenzylideno)sorbitol (DMDBS). DMDBS acted as an effective nucleating agent, which improved the mechanical properties and slowed down the degradation of the WF/PLA composites. The enzymatic degradation of the composites was examined by immersing in proteinase K or cellulase buffer. The presence of DMDBS resulted in a 26.7% increase of the crystallinity compared to the WF/PLA composites. The increase in crystallinity enhanced the thermal stability and tensile strength of the WF/DMDBS/PLA composites by 8.5%. The durability of the WF/DMDBS/PLA composites after nucleated modification was enhanced after enzymolysis. After nucleated modification, the surface of the WF/PLA composites showed clear cracks due to degradation, while these appeared about 2 weeks later in the case of the WF/DMDBS/PLA composites. The results revealed that the introduction of cellulase degraded WF in the composites, which increased hydrolysis or enzymolysis sites. The combination of nucleated modification and enzyme buffer gave an expanded downstream application of WF/PLA composites in packaging and agricultural materials. © 2019 Society of Chemical Industry     

Crystallization,mechanical properties,and enzymatic degradation of biodegradable poly(ε‐caprolactone) composites with poly(lactic acid) fibers

Biodegradable polymer composites based on poly(ɛ‐caprolactone) (PCL) and poly(lactic acid) (PLA) fibers were prepared by melt compounding. The effects of PLA fibers on the crystallization, mechanical properties, and enzymatic degradation of PCL composites were investigated. The addition of PLA fibers enhanced the crystallization of PCL due to the heterogeneous nucleation effect of fibers. However, the final crystallinity of the PCL in the composites was little changed in the presence of PLA fibers. With the addition of PLA fibers, significant improvement in storage modulus (E′) of PCL in the composites was achieved. A significant increase in E′ was 173% for the composites as compared to that of the neat PCL at 20°C. With the increase in PLA fibers content, the PCL composites showed decreased elongation and strength at break; however, the tensile yield strength and modulus were increased significantly, indicating that PCL was obviously reinforced by adding PLA fibers. Although the PLA fibers retarded the enzymatic degradation of PCL, it was possible to be completely degraded without much degradation time for PCL blending with suitable amounts of PLA fibers. POLYM. COMPOS., 34:1745–1752, 2013. © 2013 Society of Plastics Engineers     

Preparation,characterization, and biodegradability of renewable resource‐based composites from recycled polylactide bioplastic and sisal fibers

The biodegradability, morphology, and mechanical thermal properties of composite materials composed of polylactide (PLA) and sisal fibers (SFs) were evaluated. Composites containing acrylic acid‐grafted PLA (PLA‐g‐AA/SF) exhibited noticeably superior mechanical properties because of greater compatibility between the two components. The dispersion of SF in the PLA‐g‐AA matrix was highly homogeneous as a result of ester formation and the consequent creation of branched and crosslinked macromolecules between the carboxyl groups of PLA‐g‐AA and hydroxyl groups in SF. Furthermore, with a lower melt temperature, the PLA‐g‐AA/SF composite is more readily processed than PLA/SF. Both composites were buried in soil to assess biodegradability. Both the PLA and the PLA‐g‐AA/SF composite films were eventually completely degraded, and severe disruption of film structure was observed after 6–10 weeks of incubation. Although the degree of weight loss after burial indicated that both materials were biodegradable even with high levels of SF, the higher water resistance of PLA‐g‐AA/SF films indicates that they were more biodegradable than those made of PLA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011