改性处理对汉麻秆粉/聚乳酸复合材料性能的影响

为了增加汉麻秆粉的利用率,减少成本,以可降解性聚乳酸(PLA)及汉麻秆粉(HP)制备HP/PLA生物降解复合材料。为了解决HP质量分数为50%时汉麻秆粉/聚乳酸复合材料(50-HP/PLA)的性能降低的问题,采用硅烷偶联剂(KH550)、钛酸酯偶联剂(TC201)、邻苯二甲酸二辛酯(DOP)、苯乙烯-丁二烯-苯乙烯(SBS)对50-HP/PLA改性,研究不同改性剂对50-HP/PLA的吸水性能、拉伸性能、弯曲性能以及热稳定性能的影响。结果表明：与未改性的复合材料相比,改性后的50-HP/PLA拉伸弯曲强度均提高,SBS的添加使得50-HP/PLA的拉伸强度、断裂伸长率分别提高了41.47%和18.44%,其纯SBS的添加使得复合材料性能优于SBS+DOP;在KH550处理后的50-HP/PLA弯曲强度和弯曲模量达到最大,分别提高了61.2%和17.2%,其KH550改性效果优于TC201;经过改性剂处理后50-HP/PLA的吸水性均降低,且热稳定性均提高。改性后的50-HP/PLA的吸水性和力学性能均达到相关国家标准及行业标准的要求。     

壳聚糖/纳米纤维素/石墨烯改性纳米TiO2复合膜光催化降解性能

以氧化石墨烯改性纳米二氧化钛为光催化活性成分,通过流延成型法制备了壳聚糖/纳米纤维素/石墨烯改性纳米TiO₂光催化复合膜。利用热重分析仪(TG)、傅里叶红外光谱仪(FTIR)和扫描电子显微镜(SEM)对复合膜的结构进行表征。研究了壳聚糖/纳米纤维素/改性纳米TiO₂复合膜的力学性能,对比了复合膜对亚甲基蓝及甲基橙的光催化降解性能。结果表明,改性纳米TiO₂的添加提高了壳聚糖复合膜的力学性能及耐热性能。改性纳米TiO₂质量分数为4%的复合膜抗拉强度最大,达到43 MPa。改性纳米TiO₂质量分数为2%的复合膜断裂伸长率最大为13.6%。在模拟溶液质量浓度为20 mg/L时,改性纳米TiO₂质量分数为2%的复合膜对亚甲基蓝降解率最大,为51.7%。改性纳米TiO₂质量分数为4%的复合膜对甲基橙降解率最大,为42.2%。模拟溶液初始浓度愈高,则复合膜对亚甲基蓝及甲基橙降解率均降低。     

PLA/nano-TiO_2复合膜的制备及性能研究

采用流延成膜法,通过向聚乳酸(PLA)体系中添加无机抗菌剂纳米二氧化钛(nano-TiO_2)共混制备得到PLA/nano-TiO_2复合膜。为研究nano-TiO_2的含量对PLA膜的性能的影响,测定了纯PLA膜及不同质量分数的PLA/nano-TiO_2复合膜的密度、色度、溶解率、力学性能、抗菌性能、水蒸气透过量等性能指标,并通过傅里叶红外光谱分析了其官能团变化,对比研究其实际应用价值。结果表明,由于nano-TiO_2的加入,复合膜的密度、溶解率、拉伸强度均有一定降低,但色度、抗菌性能、水蒸气透过量及断裂伸长率都呈明显升高趋势。当nano-TiO_2质量分数为1%时,透湿性最低为纯PLA膜的(132.1±10.0)%。PLA/3%nano-TiO_2复合膜的抗菌性最佳,其对大肠杆菌和金黄色葡萄球菌的抑菌圈直径大小分别是(4.86±0.50)mm和(5.98±0.77)mm。PLA/2%nano-TiO_2复合膜的色度达到最大值7.52±1.05,是纯PLA膜的(306.5±30.8)%。PLA/4%nano-TiO_2复合膜有最高的断裂伸长率为(62.7±5.70)%。综合来看,PLA/2%nano-TiO_2复合膜具有最佳的性能参数。将PLA与nano-TiO_2复合,可以明显改善PLA膜的各方面性能,使其更有望用于食品包装领域。     

不同偶联剂对HDPE/Nano-ZnO复合膜性能的影响

通过熔融共混和热压法制备了高密度聚乙烯/纳米氧化锌(HDPE/nano-ZnO)复合膜,考察了偶联剂对HDPE/nano-ZnO复合膜性能的影响。采用电子万能试验机测试了复合膜的力学性能,通过平板计数法测定了复合膜的抗菌性。结果表明:偶联剂KH560改性HDPE/nano-ZnO复合膜的力学性能较高;HDPE/nano-ZnO复合膜对大肠杆菌和金黄色葡萄球菌均具有非常强的抗菌性,且抗菌性受nano-ZnO用量和偶联剂类型的影响;改性nano-ZnO用量低于0.5%时,HDPE/nano-ZnO复合膜抗菌性强弱顺序为:KH560改性KH550改性未改性;nano-ZnO用量超过0.5%时,未改性与改性nano-ZnO制得复合膜的抗菌性能较接近,其抗菌率均约为100%。Nano-ZnO用量和偶联剂类型对HDPE/nano-ZnO复合膜的力学性能和抗菌性均有影响。     

玻璃纤维对聚乳酸力学性能的影响

采用熔融复合和模压成型工艺,分别制备玻璃纤维(GF)增强聚乳酸(PLA)复合材料及其经KH550表面改性的复合材料。通过扫描电镜观察和力学性能测试,系统研究玻璃纤维和KH550的用量对玻璃纤维改性聚乳酸复合材料的微观形貌、冲击、弯曲和拉伸强度的影响。结果表明含KH550的复合材料中玻璃纤维表面被聚乳酸基质包覆。当聚乳酸与玻璃纤维质量比为7∶3时,复合材料的冲击、弯曲和拉伸强度达到最大,分别为17.33 kJ/m2、96.23 kPa和75.24 kPa。与纯PLA的相比,分别增加8.31%、20.2%和25.4%。当复合体系中添加一定量(1.2%)KH550,体系的这些性能有所改善,分别达到18.52 kJ/m2、110.34 kPa和77.59 kPa。     

改性凹凸棒土的制备及其对聚乳酸材料的性能影响

采用硅烷偶联剂KH-550对凹凸棒土进行表面改性,制得改性凹凸棒土。以聚乳酸(PLA)为基体,通过熔融共混制备了改性凹凸棒土/PLA纳米复合材料。研究和对比了改性凹凸棒土的添加量对纳米复合材料性能的影响。结果表明:KH-550改善了凹凸棒土的亲油性,但未改变其晶型结构。将改性凹凸棒土粒子加到PLA中能有效提高体系的力学性能和耐热性能,在添加量为10%时,拉伸强度达到最优值92.75 MPa。     

聚乳酸/玉米秸秆粉复合材料的制备与性能研究

以聚乳酸(PLA)和玉米秸秆粉为主要原料,采用溶液浇铸法制备了PLA/玉米秸秆粉复合材料,研究了原料配比、偶联剂类型和用量对PLA/玉米秸秆粉复合材料的化学结构、界面相容性、热稳定性、力学性能和吸水性能的影响。结果表明,复合材料的力学性能随玉米秸秆粉的加入先增后降,当玉米秸秆粉的加入量为20%(质量分数,下同)时,复合材料的性能最佳;硅烷偶联剂(KH550)或钛酸酯的加入明显改善了玉米秸秆粉与PLA的相容性,有助于玉米秸秆粉与PLA的键合,提升了复合材料的力学性能和热稳定性、降低了吸水性能;当KH550的加入量为1.5%或钛酸酯的加入量为3%时,复合材料的综合性能分别达到最佳,且钛酸酯的作用效果明显优于KH550。     

稻壳二氧化硅/环氧树脂纳米复合材料机械性能研究

将稻壳用10%的盐酸处理后在600℃焚烧得到纯度为99.3%的SiO_2,将SiO_2用偶联剂γ-氨丙基三乙氧基硅烷(KH550)改性后与环氧树脂(EP)复合,探讨了SiO_2质量分数在0～5%范围内复合材料的力学性能.研究结果显示:经硅烷偶联剂KH550改性后稻壳SiO_2粒子为无定形态,尺寸在30～50 nm且能显著提高环氧树脂的力学性能.当稻壳SiO_2质量分数为3%时,材料的拉伸性能以及弯曲性能的提高率最大,拉伸强度、拉伸模量、弯曲模量和弯曲强度的提高率分别为27.25%、6.54%、61.7%和24.56%.SEM研究结果显示:复合材料中SiO_2与基体树脂之间有较好的相容性.     

偶联剂对PLA/PBAT/WF复合材料3D打印性能的影响

以聚乳酸（PLA）和聚己二酸/对苯二甲酸丁二酯（PBAT）为基体,杨木粉（WF）为填充增强材料,使用混炼机熔融共混制备PLA/PBAT/WF复合材料,采用熔融沉积成型（FDM）技术制备标准实验试样,通过扫描电子显微镜、红外光谱分析、旋转流变测试以及力学试验等方法,研究不同含量的硅烷偶联剂KH550对PLA/PBAT共混物以及PLA/PBAT/WF的相容性、流变性及力学性能的影响。结果表明,在偶联剂用量为3 %（质量分数,下同）时,拉伸强度提高了136 %;偶联剂KH550与 PLA和PBAT共价键偶联生成接枝聚合物,二者相容性得到提高;同时偶联剂与WF表面羟基发生缩聚反应有效的改善了其与PLA/PBAT的基体相容性,PLA/PBAT/WF复合材料的FDM的制件力学性能得到较大提升;复合材料的黏度随偶联剂含量的增加呈下降的趋势,含量为3 %时线材的综合打印性能及制品质量最佳。     

PLA/MCC复合材料的制备及其性能

以水稻秸秆经碱解、酸解得到的微晶纤维素(MCC)作为聚乳酸(PLA)的改性材料,通过溶液共混、流延成膜制备了PLA/MCC复合膜,采用傅里叶变换红外光谱仪、差示扫描量热仪、扫描电子显微镜等对其性能进行了表征。结果表明:水稻秸秆中木质素、半纤维素等杂质大部分被有效除去,当NaOH质量分数为5%时,去除率最大,MCC成功制备;当MCC质量分数为8.3%时,可以最大程度改善PLA/MCC复合膜的拉伸性能,MCC与PLA结合最好,而MCC的加入会使复合膜的热稳定性有所降低。     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.