聚氨酯预聚体改性聚乳酸/木粉复合材料的制备及表征

通过共混挤出法制备聚氨酯预聚体(PUP)改性的聚乳酸/木粉(PLA/WF)复合材料,并对复合材料进行力学性能测试、动态热机械分析、接触角测量以及断面扫描电镜分析。力学性能分析表明:当PUP用量(以PLA和WF的质量计)为20%时,复合材料断裂弯曲应变和冲击强度分别为5.78%和18.3 k J/m2,较未改性的复合材料分别提高了209%和123%,PUP显示出较好的增韧效果。动态热机械分析表明:随着PUP用量的增加,复合材料中PUP相和PLA相的玻璃化转变温度均有所下降,并且储能模量显著降低,材料韧性得到改善。PUP的加入可显著提高复合材料对水的接触角,材料疏水性能得到改善。当PUP用量为25%时,接触角达83.7°,较未增韧复合材料接触角(66.6°)提高25.7%。拉伸断面的扫描电镜分析表明:添加PUP的复合材料断面有更多的木粉被拉出且空穴变多,断面更为不平整,呈现韧性断裂的特征。     

黄麻纤维织物增强乙烯酯复合材料的制备与力学性能

织物增强聚合物(TRP)因其具有优异的机械性能而被广泛应用于汽车、建筑等领域。传统TRP材料通常以玻璃纤维、碳纤维作为增强体,由于成本高及不可降解等问题限制了发展和应用。本研究采用可生物降解的天然黄麻纤维为增强体,以乙烯酯为基体树脂,采用模压工艺制备双层黄麻织物增强乙烯酯树脂复合材料。考察经纱和纬纱的取向对复合材料密度、孔隙率及力学性能的影响。通过调整黄麻织物的纱线角度(0°,30°,45°,60°和90°),研究经纬纱角度对复合材料性能的影响,采用的模压成型工艺是80℃、7 MPa条件下压制2.5 h。为了考察模压温度的影响,将纱线角度为60°的试样在40℃的低温条件下(其余条件不变)压制成型。结果表明:与纯乙烯酯相比,黄麻纤维具有一定的增强作用,复合材料的弯曲强度和冲击强度分别提高24.77%和39.83%,拉伸性能降低30.52%。扫描电子显微镜结果显示,复合材料力学强度的提高与纱线间的孔隙分布有关。在研究范围内,经纬纱定向对复合材料的冲击强度影响比较显著。低温(40℃)条件下,制备的定向角为60°时的黄麻纤维增强乙烯基酯复合材料的各项力学性能达到最佳。     

CaCO<Subscript>3</Subscript> in situ treated bamboo pulp fiber reinforced composites obtained by vacuum-assisted resin infusion

The aim of this study is to investigate the properties of CaCO₃ in situ treated bamboo pulp fiber (BPF) composites that have been filled with epoxy resin by means of vacuum-assisted resin infusion (VARI). Un-treated and treated BPF were processed at a pressure of 0.24 MPa into BPF preforms. VARI was used to infuse epoxy resin through the BPF preforms to make BPF composites. The flexural properties, impact property, and thermal properties of the BPF composites were analyzed. CaCO₃ with the loading of 30 wt% affects the performance of the composites. The flexural strength did not decrease and modulus of the treated BPF composites increased by 9.38%, while the impact strength decreased by 50.98%, compared to the control sample. Dynamic mechanical analysis revealed the maximum elastic moduli of the treated specimens increased by 1.19 times in the temperature range of ?20 to 120 °C. The thermal decomposition temperature of the composites was influenced by the effect of the crystal field and size effect of CaCO₃.     

白僵菌和绿僵菌林间感染星天牛成虫试验

应用白僵菌和绿僵菌的菌条,在林间通过星天牛成虫在木麻黄树干的菌条上自由爬行接触的方法,对星天牛成虫进行感染试验。结果表明:林间星天牛成虫接触白僵菌和绿僵菌菌条13 d后,死亡率达100%(对照组死亡率仅为16.7%),致死中时(LT50)分别为6.77 d和5.93 d;感染白僵菌和绿僵菌菌条的天牛成虫存活期分别为7.9 d(3～13 d)和7.1 d(3～13d),极显著低于对照的26.1 d(8～43 d)。说明利用白僵菌和绿僵菌菌条林间防治星天牛成虫效果显著,可进一步推广应用。     

MA-SEBS对木纤维/聚丙烯复合材料冲击断裂行为的影响(英文)

马来酸酐接枝苯乙烯-乙烯-丁烯-苯乙烯(MA-SEBS)用作聚丙烯/木纤维复合体系的界面相容剂及冲击改性剂,来提高其界面粘接及冲击强度。研究了MA-SEBS含量对PP/WF复合材料冲击断裂行为的影响,当MA-SEBS含量达到8%时,冲击性能达到了最大值,进一步增加到10%并未提高其断裂韧性,但动态热机械分析(DMA)表明复合材料刚性的提高,这归因于PP/WF界面的改善,当MA-SEBS超过8%,聚丙烯与木纤维分子间的相互作用增强。扫描电子显微镜(SEM)分析了样品的断裂表面,表明木纤维与聚丙烯表面强烈的界面粘结。图5表1参11。     

聚合物基/稻壳粉复合材料的表面改性研究

使用JC2000A型接触角测量仪测试并研究了蒸馏水和甘油两种液体在稻壳粉填充聚乙烯(PE)、聚丙烯(PP)、聚氯乙烯(PVC)复合材料表面的接触角.研究表明:通过酸碱处理可明显改变接触角及其随时间变化的规律;其中效果最好的是以水作为探测液时,经酸处理后的PE/稻壳粉复合材料.通过方差分析得知表面改性处理方式对接触角有相当显著的影响.     

木纤维PP/PE共混物复合材料的流变和力学性能(英文)

For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.     

Toughening wood/polypropylene composites with polyethylene octene elastomer （POE）

Introduction Wood-Plastic Composite (WPC), due to its high stiffness, low density, low cost, environment friendly characteristics such as recyclablity and biodegradability, is gaining more and more interests, both in research and application. However, one…     

Effect of maleic anhydride grafted styrene-ethylene-butylene-styrene （MA-SEBS） on impact fracture behavior of polypropylene / wood fiber composites

MA-SEBS as compatibilizer and impact modifier was incorporated into Polypropylene/Wood Fiber （PP/WF） to enhance interface adhesion and impact strength of the composite. The effect of MA-SEBS content on the impact fracture behavior of PP/WF composites was studied. The impact properties of composites with 8% MA-SEBS reached the maximum value. And further increasing of MA-SEBS content to 10% did not improve the fracture toughness, but improved the stiffness of composites by DMA analysis. This was attributed to the improved PP/WF adhesion. As the MA-SEBS content is more than 8%, the molecule interaction of PP and WF was expected to much stronger than lower MA-SEBS. Scanning electron microscopy （SEM） was performed to analyze the impact fracture surface and showed a stronger affinity for the wood surfaces.     

Comparison of water absorption and mechanical properties of wood–plastic composites made from polypropylene and polylactic acid

Abstract

This study focuses on the water absorption and mechanical properties of composites made from softwood sawdust and plastics, such as virgin and recycled polypropylene and polylactic acid (PLA). The composites were processed by extrusion, and their properties were investigated by a water immersion test, mechanical tests and a cyclic test for moisture resistance. Scanning electron microscopy was used to study the morphology of the fracture surfaces of the composites. The composites made with recycled polypropylene had the lowest water absorption and thickness swelling of the studied composites. The PLA composites made with heat-treated sawdust showed the highest flexural strength. Of the polypropylene based composites, virgin polypropylene resulted in composites with higher flexural strength. The Charpy impact strength of the composites was found to have an inverse trend compared to flexural strength. Cyclic treatment of the studied composites resulted in 20–60% loss of flexural strength, depending on type of composite.     

纳米CaCO3对木纤维增强生物可降解复合材料力学性能的影响

为探索纳米CaCO₃对增强生物可降解复合材料力学性能的影响,采用混炼、注射成型工艺制备纳米CaCO₃改性木纤维/聚乳酸复合材料,研究了纳米粒子添加量（1wt%,2wt%,3wt%,4wt%）及粒子预处理（偶联剂,硬脂酸,偶联剂-硬脂酸）对材料拉伸性能与冲击性能的影响。随着CaCO₃添加量增加,复合材料力学强度先增大后减小,质量分数2%时材料拉伸强度和冲击强度分别提高8%与20%,粒子的增韧效果明显。预处理不仅能增强木纤维与聚乳酸的结合,也提高了纳米粒子分散性,增强材料整体力学性能。纳米粒子在聚合物基体中的分散性及其与聚合物界面结合是影响材料性能的关键。     

冷等离子体和2D树脂基防护剂对毛竹材的防护效果

采用滑动弧冷等离子体对竹条和圆竹筒进行处理,并将处理后的样品进行复合型防护药剂加压浸渍处理。采用质量增加率、平衡含水率、湿胀率以及竹条和竹筒的抗压强度等指标来考察防护药剂处理后对竹材性能的影响,并观察竹条和圆竹筒防护处理后的发霉情况。实验结果表明,竹条和圆竹筒表面在加压条件下对二羟甲基二羟乙基乙烯脲(2D树脂)+戊唑醇与丙环唑(PT)+碘代丙炔基氨基甲酸丁酯(IPBC)复合型树脂防护剂的渗透性和附着性得以提升,表现为竹条和圆竹筒经滑动弧冷等离子体和防护药剂加压浸渍处理后质量增加率提高,而平衡含水率和湿胀率下降。对竹条和圆竹筒的质量增加率、平衡含水率、湿胀率和抗压强度产生积极影响的顺序为:冷等离子体处理+加压浸渍防护药剂>加压浸渍防护药剂>未经任何处理的竹条和圆竹筒。此外,竹节的多少也对竹材的质量增加率、平衡含水率和湿胀率产生影响,影响顺序为:无节>单节>双节。处理后,竹条和圆竹筒具有优异的防霉特性,存放半年后,圆竹筒仍能保持原来的物理特征,竹条和圆竹筒表面和端部均无发霉、腐朽和开裂现象。     

竹粉／聚丙烯塑料复合材料转矩流变特性研究

利用转矩流变仪研究了竹粉／聚丙烯塑料复合材料的转矩流变行为。使用正交试验设计分析了竹粉含量、马来酸酐添加量以及转矩转速3因素对复合材料转矩流变行为的影响。试验结果表明，竹粉／聚丙烯塑料复合材料是一种假塑性流体即剪切变稀流体。在给定的试验条件下，3种因素对复合材料转矩流变行为的影响中，竹粉含量的影响最显著，其余的2因素的影响则不显著。     

二次正交旋转试验对麦秸塑料复合材料冲击强度影响

选用农作物秸秆-麦秸粉和热塑性塑料-高密度聚乙烯（HDPE）为原料，添加马来酸酐接枝聚乙烯（MAPE）为改性剂，利用单双螺杆挤出机组，采用熔融挤出方式制备麦秸塑料复合材料。在其它条件固定的情况下，研究双螺杆挤出机温度、转速和麦秸粉含量等因素对麦秸塑料复合材料冲击强度的影响，设计二次正交旋转回归组合试验方案对双螺杆挤出工艺进行优化。麦秸塑料复合材料的冲击强度与双螺杆挤出机的温度和转速以及原料中麦秸粉添加比例存在一定的相关性，通过试验建立了麦秸塑料复合材料冲击强度（y）对双螺杆挤出机温度（x1）、转速（x2）、麦秸粉比例（x3）三个试验因素之间的正交回归模型方程：y=17．98106—0．82505x1^2-0．94349x2^2-1．00182x3^2；；从模型推知，当温度为160℃、双螺杆转速为30rpm和麦秸粉用量为60％时，冲击强度达到最大值17．98kJ／m2，实验验证结果与模型值相符。研究结果对提高麦秸塑料复合材料冲击强度和优化工艺参数具有重要的指导意义和应用价值。     

Effect of organoclay platelets on the mechanical properties of wood–plastic composites formulated with virgin and recycled polypropylene

Abstract

This study investigated the effects of organoclay platelet contents (0, 3 and 5 wt%) and polypropylene type (virgin and recycled) on the mechanical properties of polypropylene/wood flour composites. Composite samples were made by melt compounding and consequent injection moulding. The tensile, flexural and impact properties of resultant composites were determined. X-ray diffraction (XRD) analysis of composites with 3 and 5% nanoclay content was also conducted. The results indicated that tensile and flexural properties of the composites increased with the addition of nanoclay particles up to 3 wt% and decreased thereafter. The impact strength of the composites, however, decreased with the incorporation of nanoclay. The mechanical properties of the recycled polypropylene-based nanocomposites were statistically comparable with those based on virgin polypropylene. XRD analysis revealed that the degree of intercalation in the nanocomposites containing 3% nanoclay was higher than in those containing 5%. Based on these results, it can be concluded that recycled polypropylene could be used instead of virgin polypropylene in the production of value-added products with no significant adverse effects on the mechanical properties.     

Effect of microwave plasma treatment on surface wettability of common teak wood

The improvement of wood surface wettability can clearly improve bonding properties, as well as enhance physical and mechanical properties of wood composites. In our investigation, the microwave plasma (MWP) technique was adopted to treat the surface of common teak. The treatment effect was evaluated by measuring the contact angles of liquids and calculating the free surface energy. The results show that the modification effect improved when the sample was located 120 mm from the resonance cavity, rather than at 80 mm. A MWP treatment over a short span of time is useful to lower the contact angles and improve the surface wettability considerably. The range of decreasing contact angles, tested by water, could reach 74% at a distance of 120 mm. __________ Translated from Journal of Northeast Forestry University, 2007, 35(12): 31–33 [译自: 东北林业大学学报]     

The properties of flax fiber reinforced wood flour/high density polyethylene composites

Flax fiber(FF) was used to reinforce wood flour/high density polyethylene composites(WF/PE).WF/PE particles were uniformly mixed with FF via high-speed mixing and then extruded with a single screw extruder to prepare FF reinforced WF/PE composites(FF/WF/PE).Mechanical testing,dynamic mechanical analysis,scanning electron microscopy(SEM),creep measurement and Torque rheology were used to characterize the resulting composites.The results indicate that the mechanical performance of the composites could be remarkably improved by adding a limited amount of FF.The flexural strength and modulus increased by 14.6 and 51.4%,respectively(FF content of 9 wt%),while the unnotched impact strength could be increased by 26.5%(FF content of12 wt%).The creep resistance and toughness of thecomposite was markedly improved without changing the plastic content of the composite material.     

Using flower strips to promote green lacewings to control cabbage insect pests

Habitat management improves biological control by increasing the abundance and fitness of natural enemies through the provision of floral resources along field edges or between crops. Among the natural enemies reliant on flower resources, green lacewings often stand out due to their abundance, predation capacity and polyphagy. We evaluated the impact of tailored flower strips on the enhancement of natural enemies, especially green lacewings, in three organic cabbage (Brassica oleracea) farms in Southern Sweden. Insects were sampled from the flower strips, and cabbage pests and predators were visually recorded in the crop. In a laboratory assay, the pollen feeding preferences of Chrysoperla carnea (Stephens, 1836) were evaluated in a dual-choice test. The pollen consumed by the Chrysopidae was extracted from laboratory and field specimens, then quantified and identified. Flower strips were found to attract predators and parasitoids, whose abundance increased as flowers bloomed. Cabbage plants next to the flower strips showed lower pest infestation as compared to cabbage plant control, although no significant differences were observed in the number of predators. Chrysopidae used flower strips as feeding, reproduction and shelter sites and mainly consumed pollen from Phacelia tanacetifolia Benth. Under laboratory conditions, C. carnea showed a preference for P. tanacetifolia and Coriandrum sativum L. pollen over Borago officinalis L. and Fagopyrum esculentum Moench. We show that tailored flower strips could be an efficient tool for enhancing beneficial arthropods and should be considered in integrated pest management for cabbage crops.

     

麦秸/聚乙烯复合材料的研究

以麦秸粉和高密度聚乙烯为主要原料,采用挤出成型方式制备生物质/塑料复合材料的试验结果表明,随着麦秸粉用量的增加,所制成复合材料的弯曲强度、冲击强度、抗拉强度呈下降趋势;麦秸粉粒度为-40 60目时,上述各指标达到最大值;随着MAPE用量的增加,复合材料的弯曲强度和抗拉强度增大,但对冲击强度影响较小.     

The effect of hyperbranched polymer lubricant as a compatibilizer on the structure and properties of lignin/polypropylene composites

Abstract

In this work, the lignin/polypropylene (PP) composites were prepared by lignin and PP using hyperbranched polymer lubricant (HBPL) as a compatibilizer, which was synthesized by oleic acid and amino-terminated hyperbranch (HBP-NH₂) polymer in toluene solvent. The impact and flexural strength of the resulting composites were investigated. Experimental results indicated that the impact strength and flexural strength of lignin/PP composites modified with HBPL are 52.3% and 63.6% higher than that of untreated systems, respectively. HBPL treatment could also significantly improve the melt flow rate (MFR) of the lignin/PP composites. Meanwhile, the storage modulus (E′) of adding the HBPL was slightly higher than that of the uncompatibilized system. In addition, scanning electron microscope images showed that the dispersion of the lignin added with HBPL in the polymer matrix was improved. It can be inferred that the lignin and PP matrix interfacial bonding was strengthened.