聚乳酸/改性刨花板木粉木塑复合材料的力学性能研究

采用氢氧化钠(NaOH)、过氧化氢（H2O2）、异氰酸酯(IPDI)等不同改性剂对刨花板木粉进行化学改性处理,将改性后的刨花板木粉（PBF）与聚乳酸(PLA)基体通过熔融挤出共混,制备出PLA/PBF 木塑复合材料,研究了刨花板木粉改性处理方法和含量对木塑复合材料力学性能的影响。结果表明,刨花板木粉经NaOH+H2O2或NaOH+IPDI处理后,能显著改善木粉与基体间的界面相容性,提高木塑复合材料的力学性能;经NaOH+H2O2处理后,PBF含量为20 %（质量分数,下同）的PLA /PBF木塑复合材料的弯曲强度相比于未处理的增加了21.63 %,达到118.5 MPa;拉伸强度增加了19.53 %,达到101.0 MPa;采用NaOH+H2O2改性处理的、PBF含量为20 %的PLA/PBF木塑复合材料具有更好的力学性能。     

巯基丙酸保护的纳米银制备及热分解行为研究

以双官能团配体巯基丙酸(MPA)为保护剂, 通过配体置换法和液相化学还原法制备得到纳米银.考察了双官能团配体对纳米银的制备及热分解的影响.配体置换法制备的纳米银粒径为50 nm左右,化学还原法制备的纳米银粒径为10 nm左右.元素分析结果和X射线光电子能谱表明MPA通过S原子与Ag原子形成共价键,同时通过烷基链之间的氢键作用及范德华力形成多层保护剂保护的纳米银.将纳米银在200 ℃下烧结并对烧结产物进行表征,结果表明加热使得C-S键断裂,Ag/MPA热分解形成硫化银.     

埃洛石增强聚乳酸复合材料的力学性能及热稳定性能研究

通过共混的方法制备了聚乳酸（PLA）和埃洛石（HNT）复合材料,并研究了HNT添加量对PLA/HNT复合材料的力学性能、热性能及微观形貌的影响。结果表明,HNT对PLA具有显著的增强效果,PLA/HNT复合材料的力学性能有很大的提高,且在HNT用量为8 %时达到最佳的力学性能;但是,HNT的加入使PLA/HNT复合材料的断裂伸长率和冲击强度均有所下降;此外,HNT的加入提高了复合材料的相对结晶度和熔融温度,同时PLA/HNT复合材料的热稳定性也得到了较大的提高;PLA/HNT复合材料的断面形貌显示,复合材料的断面形貌逐渐从粗糙变得平整,复合材料从韧性断裂逐渐转变为脆性断裂。     

木粉增强木质素／环氧树脂复合材料的制备与力学性能

将玉米秸秆酶解木质素和双酚A环氧树脂共混,利用低相对分子质量聚酰胺作为同化剂,采用热压工艺制备了一种木粉增强的交联型木质素,环氧树脂复合材料,研究了热压温度、热压压力以及木粉的加入对复合材料力学性能的影响。研究结果表明,随着热压温度和热压压力的增加,木粉增强木质素,环氧树脂复合材料的弯曲强度和冲击强度均先升高而后降低,在120℃热压温度、8MPa热压压力下复合材料的力学性能达到最佳。随着木粉含量的增加,复合材料的弯曲强度和冲击强度均升高;木粉的粒径也对复合材料的力学性能有较大影响;综合考虑复合材料的力学性能,优选加入40—80目的木粉,木粉的含量为20％。     

Functional Hyaluronic Acid-Polylactic Acid/Silver Nanoparticles Core-Sheath Nanofiber Membranes for Prevention of Post-Operative Tendon Adhesion

In this study, we prepared core-sheath nanofiber membranes (CSNFMs) with silver nanoparticles (Ag NPs) embedding in the polylactic acid (PLA) nanofiber sheath and hyaluronic acid (HA) in the nanofiber core. The PLA/Ag NPs sheath provides mechanical support as well as anti-bacterial and anti-inflammatory properties. The controlled release of HA from the core could exert anti-adhesion effects to promote tendon sliding while reducing fibroblast attachment. From the microfibrous structural nature of CSNFMs, they function as barrier membranes to reduce fibroblast penetration without hampering nutrient transports to prevent post-operative peritendinous adhesion. As the anti-adhesion efficacy will depend on release rate of HA from the core as well as Ag NP from the sheath, we fabricated CSNFMs of comparable fiber diameter, but with thick (Tk) or thin (Tn) sheath. Similar CSNFMs with thick (Tk⁺) and thin (Tn⁺) sheath but with embedded Ag NPs in the sheath were also prepared. The physico-chemical properties of the barrier membranes were characterized in details, together with their biological response including cell penetration, cell attachment and proliferation, and cytotoxicity. Peritendinous anti-adhesion models in rabbits were used to test the efficacy of CSNFMs as anti-adhesion barriers, from gross observation, histology, and biomechanical tests. Overall, the CSNFM with thin-sheath and Ag NPs (Tn⁺) shows antibacterial activity with low cytotoxicity, prevents fibroblast penetration, and exerts the highest efficacy in reducing fibroblast attachment in vitro. From in vivo studies, the Tn⁺ membrane also shows significant improvement in preventing peritendinous adhesions as well as anti-inflammatory efficacy, compared with Tk and Tn CSNFMs and a commercial adhesion barrier film (SurgiWrap^®) made from PLA.     

聚乳酸/竹粉复合材料的改性及性能研究

采用甲基丙烯酸缩水甘油酯接枝乙烯辛烯共聚物（POE?GMA）作为相容剂,TPW604作为润滑剂,利用XSS?300转矩流变仪熔融制备聚乳酸（PLA）/竹粉（BF）复合材料。通过热失重、拉伸、冲击 、扫描电子显微镜、旋转流变等方法研究BF、POE?GMA、TPW604添加量对PLA/BF复合材料性能的影响。结果表明,当BF添加量为35 %、POE?GMA添加量为10 %、TPW604添加量为1 %时,复合材料的相容性和流动性均显著提升,复合材料的力学性能达到最优。     

几种增塑剂增塑聚乳酸的性能研究

用聚乙二醇（PEG）、邻苯二甲酸二辛酯（DOP）、柠檬酸三丁酯（TBC）、亚磷酸三苯酯（TPPi）、癸二酸二丁酯（DBS）分别与聚乳酸（PLA）熔融共混，通过试样拉伸性能测试和DSC分析，研究这几种增塑剂对PLA拉伸性能和热性能的作用。结果表明，在这几种增塑剂中，TPPi和DBS增塑效果最好，能显著降低PLA玻璃化转变温度和熔融温度，提高PLA断裂伸长率和结晶度。     

Modified Industrial Three-Dimensional Polylactic Acid Scaffold Cell Chip Promotes the Proliferation and Differentiation of Human Neural Stem Cells

In this study, we fabricated a three-dimensional (3D) scaffold using industrial polylactic acid (PLA), which promoted the proliferation and differentiation of human neural stem cells. An industrial PLA 3D scaffold (IPTS) cell chip with a square-shaped pattern was fabricated via computer-aided design and printed using a fused deposition modeling technique. To improve cell adhesion and cell differentiation, we coated the IPTS cell chip with gold nanoparticles (Au-NPs), nerve growth factor (NGF) protein, an NGF peptide fragment, and sonic hedgehog (SHH) protein. The proliferation of F3.Olig2 neural stem cells was increased in the IPTS cell chips coated with Au-NPs and NGF peptide fragments when compared with that of the cells cultured on non-coated IPTS cell chips. Cells cultured on the IPTS-SHH cell chip also showed high expression of motor neuron cell-specific markers, such as HB9 and TUJ-1. Therefore, we suggest that the newly engineered industrial PLA scaffold is an innovative tool for cell proliferation and motor neuron differentiation.     

Effect of Wood Flour Content on the Thermal,Mechanical and Dielectric Properties of Poly(vinyl chloride)

Several composite formulations of poly(vinyl chloride)/olive wood flour (PVC/WF) were manufactured by dry‐blending PVC, wood flour, plasticizer and other processing additives in a high‐intensity mixer. The dry‐blended compounds were calendered into film samples (T = 180°C, calendered time = 8 min). The films obtained are cut into normalized samples for thermal, mechanical, and dielectric characterization. The results obtained show that stress as well as strain at break decrease sharply as the wood flour content increases. On the other hand, this filler content has little influence on the glass transition temperature. It decreases the temperature of decomposition setting and retards the PVC thermal decomposition. It increases permittivity as well as dielectric losses. The thermal stability, as measured by thermogravimetry (TGA) and differential scanning calorimetry (DSC) methods, is good enough to permit processing of these types of PVC compounds using conventional processing techniques and temperatures under 210°C.     

星型聚氨酯增韧改性聚乳酸3D打印线材

以聚醚三元醇为星型结构单体,采用本体预聚法合成具有可加工性的星型聚氨酯(SPUR),将其用于聚乳酸(PLA)的增韧改性,制备高韧性PLA/SPUR共混材料的3D打印线材,并采用熔融沉积成型(FDM)技术制备高韧性3D打印制品。结构表征及性能测试结果表明,当聚醚三元醇含量为3%时,合成的SPUR3分子量最高、综合性能最佳,将其与PLA进行共混,可显著提升PLA的断裂伸长率和冲击强度。当SPUR3含量为10%时,断裂伸长率最大,达336%,是PLA断裂伸长率的37.7倍;当SPUR3含量为30%时,共混物的冲击强度达到52.368 kJ/m2,是PLA冲击强度的31.8倍。SPUR3的混入还提高了PLA的结晶温度,降低了其储能模量和玻璃化转变温度,通过控制SPUR3的含量可以调控共混物的韧性和强度。所制备的打印线材表面均比较光滑,均能通过FDM工艺正常打印成产品。     

Curing Characteristics and Mechanical Properties of Oil Palm Wood Flour Reinforced Epoxidized Natural Rubber Composites

Abstract

The paper reports on the curing characteristics and mechanical properties of oil palm wood flour (OPWF) reinforced epoxidized natural rubber (ENR) composites. Three sizes of OPWF at different filler loadings were compounded with a two roll mill. The cure (t ₉₀) and scorch times of all filler size decrease with increasing OPWF loading. Increasing OPWF loading in ENR compound resulted in reduction of tensile strength and elongation at break but increased tensile modulus, tear strength and hardness. The composites filled with smaller OPWF size showed higher tensile strength, tensile modulus and tear strength. Scanning electron microscope (SEM) micrographs showed that at lower filler loading the fracture of composites occurred mainly due to the breakage of fibre with minimum pull-out of fibres from the matrix. However as the filler loading is increased, the fibre pull-out became very prominent due to the lack of adhesion between fibre and rubber matrix.     

Infusion of SiC Nanoparticles Into SC‐15 Epoxy: An Investigation of Thermal and Mechanical Response

Summary: In the present investigation we have developed a novel technique to synthesize nanocomposite materials consisting of SC‐15 epoxy resin and silicon carbide (β‐SiC) nanoparticles. A high intensity ultrasonic liquid processor was used to obtain a homogeneous molecular mixture of epoxy resin and β‐SiC nanoparticles. In this study, we have prepared three different samples containing 0.5, 1, and 1.5% of β‐SiC nanoparticles by weight of the epoxy resin. In parallel, control samples were also made following identical procedures without the infusion of nanoparticles. Test samples were characterized by TGA, DSC and three‐point bend flexural tests to evaluate thermal and mechanical properties. The results indicate that 1 wt.‐% loading derives the maximum improvement in both thermal and mechanical properties when compared to the neat system. The dispersion of nanoparticles and morphological changes were studied by field emission scanning electron microscopy (FE‐SEM) and high resolution transmission electron microscopy (TEM). These results demonstrate that the nanoparticles are spherical in shape (≈30 nm sizes) and are uniformly dispersed over the entire volume of the resin.

FE‐SEM micrograph of the plasma etched 1 wt.‐% SiC‐epoxy system.     

Effect of Wood Fibers on the Rheological and Mechanical Properties of Polystyrene/Wood Composites

The effects of wood fibers on the rheological and mechanical properties of polystyrene/wood (PS/wood) composites were investigated. The composites with different ratios of PS and wood were prepared by means of internal mixer and, additionally, two different sizes of the wood particles were used, such as ～100 and ～600 µm. The rheological properties were studied using capillary rheometer, apparent shear rate, apparent shear stress, apparent viscosity, power law index, and flow activation energy at a constant shear stress were determined. The rheological results showed that the shear stress–shear rate variations obeyed a power law equation, and the composites exhibited shear thinning. The flow activation energy of the composites increased with the addition of wood particles. Mechanical results showed that stress at break of the composites was higher than that of pure PS, whereas the strain at break and impact strength of the composites were lower than that of PS. In addition, the mechanical properties of the present composites were improved when the small size of wood particles were incorporated.     

3D打印凹凸棒土改性光敏树脂制备及力学性能

采用硅烷偶联剂KH550接枝改性凹凸棒土,通过超声分散和3D打印技术进一步制备了有机凹凸棒土/光敏树脂复合物。采用傅里叶变换红外光谱对改性前后的凹凸棒土结构进行了表征;通过拉伸强度和冲击强度试验对复合光敏树脂的力学性能进行了研究;采用扫描电镜观察了复合树脂冲击断面的形貌和改性凹凸棒土在树脂中的分散情况。结果表明:改性凹凸棒土的加入有助于光敏树脂韧性的提高,当添加质量分数3%时,复合光敏树脂的冲击强度最佳。     

生物质纤维和改性木质素对聚乳酸结晶性能的影响

采用改性木质素(MZS)作为成核剂,生物质纤维(BF)作为增强剂,通过双螺杆挤出机制备了生物降解的聚乳酸(PLA)/BF/MZS材料。采用差式扫量热仪(DSC)、电子万能试验机和扫描电子显微镜(SEM)分析了BF和MZS对PLA材料性能的影响。结果表明,BF和MZS有效提高了PLA的结晶能力和力学性能。当BF和MZS的含量分别为15%和1%时,PLA材料结晶度提高至67.1%,在50℃/min降温速率下仍具有较高的结晶能力。105℃等温结晶时,15%BF和1%MZS的PLA材料半结晶时间降低至9.0 s,比纯PLA缩短了72.2%。当PLA含有3%BF和1%MZS时,拉伸强度和冲击强度分别为70.1 MPa和7.4 kJ/m^2,比纯PLA分别提高了7.8%和10.4%,根据SEM显示,当BF含量为3%时,在PLA材料中分布较均匀。     

壳聚糖-银纳米微粒表面修饰木纤维的制备及抗菌性能研究

以液相还原法制备了壳聚糖-银纳米微粒（CS-Ag NPs）,并通过γ-巯丙基三甲氧基硅烷作为硅烷偶联剂将其修饰到木纤维表面,获得了具有抗菌性能的CS-Ag NPs表面修饰木纤维。采用透射电子显微镜研究了CS-Ag NPs的形貌;以傅里叶变换红外光谱、扫描电子显微镜、热重分析仪等分析手段对CS-Ag NPs表面修饰的木纤维进行了结构形貌以及热稳定性的分析,并讨论了其吸水性能。结果表明表面修饰后的木纤维接枝率为3.06%,具有高热稳定性及低吸水性。通过琼脂板计数法测试了CS-Ag NPs表面修饰前后的木纤维对耐甲氧西林金黄色葡萄球菌、革兰氏阳性菌金黄色葡萄球菌、蜡状芽庖杆菌以及革兰氏阴性菌大肠埃希氏菌的抗菌效果,结果显示表面修饰后的木纤维对实验菌种的抑菌率都在99.0%以上。此外,还研究了未处理、PVP-Ag NPs以及CS-Ag NPs表面处理的木纤维板的抗菌性能,结果表明,在湿热环境下,CS-Ag NPs表面处理的木纤维板到第8天时仍没有霉菌长出,而未处理的木纤维板和传统抗菌剂银纳米微粒处理的木纤维板到第5天时就开始长霉菌,由此可以看出表面修饰CS-Ag NPs的木纤维板具有更好的抗菌效果。     

聚磷酸铵对聚乳酸/麦秸秆复合材料阻燃和力学性能的影响

用聚磷酸铵(APP)对聚乳酸(PLA)/秸秆粉复合材料进行阻燃处理,对复合材料的阻燃性能、力学性能和热降解行为进行了分析。结果表明,APP添加量达到20份时,极限氧指数提高了33 %,成炭率提高了330 %,而且达到UL 94 V-0级,表现出显著的阻燃作用;APP的加入降低了复合材料的冲击性能,但能改善其刚性,对弯曲强度和密度影响不大;此外APP的添加还改变了复合材料的热降解行为,使其分解温度提前,稳定了PLA基体;材料燃烧后膨胀成多孔炭层,起到了隔热和阻氧的作用。     

HDPE-g-MAH增容HDPE/木粉复合材料的制备及加工设备的研究

使用HDPE-g-MAH做增容剂,通过双螺杆挤出机制备了HDPE/木粉复合材料,对HDPE-g-MAH进行量变实验,通过力学性能测试确定了最佳用量,并利用SEM对材料微观形貌进行了观察。在此基础上又采用单螺杆挤出机、开炼机和密炼机等不同的加工设备分别制备了木塑复合材料,对力学性能进行了对比表征。结果表明:HDPE-g-MAH的加入很好地改善了木塑复合材料的界面相容性、力学性能和木粉的分散性,HDPE-g-MAH的最佳用量为5份;而且只有使用剪切效果优良的双螺杆挤出机才能制备出性能优异的木塑复合材料。     

表面修饰银纳米颗粒的制备及摩擦学性能

以3-氨基-1,2,4-二噻唑-5-硫酮(ADTT)和均苯四甲酸酐为原料,在四氢呋喃溶液中,70℃下酰胺化反应合成了2,5-二(5-硫酮-1,2,4-二噻唑-3-甲酰胺基)-对苯二甲酸(BtdyTA),收率74%。以NaBH4为还原剂,在AgNO3水溶液中用液相化学还原法合成了表面修饰BtdyTA的银纳米颗粒,用透射电子显微镜(TEM)、傅里叶红外转换光谱仪(FTIR)和热分析仪(TG)对纳米颗粒的形貌、结构和热稳定性进行了表征,并在四球摩擦试验机上测试了表面修饰银纳米颗粒的抗摩减磨性能。结果表明,表面修饰的银纳米颗粒粒径分布均匀,平均粒径10nm左右,无团聚现象;在质量分数不大于5%时,可较好分散于液体石蜡等有机溶剂中,作为一种新的基础润滑油添加剂,可使摩擦系数减小32%,最小磨斑直径减小39%。     

Hyaluronic Acid Derivative Molecular Weight-Dependent Synthesis and Antimicrobial Effect of Hybrid Silver Nanoparticles

Silver nanoparticles (Ag NPs) appeared as promising antimicrobial candidates to face the development of antibiotic resistance. Although reported as toxic towards mammalian cells, their combination with biomolecules have shown reduced toxicity, while maintaining the antimicrobial function. Herein, hyaluronic acid (HA) with low (40 kDa), medium (200 and 600 kDa) and high (2 MDa) molecular weight (Mw) was modified with adipic acid dihydrazide (ADH) and used as reducing and capping agents to synthesise antimicrobial hybrid Ag NPs. The Mw of the polymer played a crucial role in the morphology, size and antibacterial activity of the Ag NPs. The 600 and 200 kDa HA-ADH-Ag NPs were able to reduce the Escherichia coli and Staphylococcus aureus concentration by more than 3 logs, while the 40 kDa NPs reached ~2 logs reduction. The 2 MDa HA-ADH failed to form homogenous NPs with strong bactericidal activity. A mechanistic study of the interaction with a model bacterial membrane using Langmuir isotherms confirmed the greater interaction between bacteria and higher Mw polymers and the effect of the NP’s morphology. The nanocomposites low toxicity to human skin cells was demonstrated in vitro, showing more than 90% cell viability after incubation with the NPs.