用于3D打印的微晶纤维素/聚乳酸复合材料制备与性能研究

以微晶纤维素（MCC）为增强材料、聚乳酸（PLA）为基体,通过高温熔融共混、挤出、拉丝等流程,制备适用于熔融沉积成型（FDM）3D打印技术的MCC/PLA复合材料,并通过FDM型3D打印机打印出成品。讨论了MCC添加量对该复合材料的力学性能、热性能、微观结构以及3D打印性能的影响。研究结果表明,随着MCC添加量的增加,复合材料的力学性能呈现先增高后下降的变化趋势,当MCC添加量为3%时,其拉伸强度和弯曲强度达到最高,分别为54.55 MPa和64.25 MPa。红外分析证实了微晶纤维素与聚乳酸在熔融时发生了接枝共聚反应。热性能分析表明,添加少量MCC,可以提高复合材料的热稳定性和PLA的结晶度。MCC添加量为3%的MCC/PLA复合材料其力学性能、打印性能和外观达到最佳,可应用于FDM型3D打印技术。     

3D打印工艺对木粉/聚乳酸材料性能的影响

采用熔融沉积法(FDM)3D打印工艺制作木粉(WF)与聚乳酸(PLA)质量比为3：100的WF/PLA复合材料,研究了打印工艺参数对WF/PLA复合材料力学性能的影响,确定了最佳打印工艺条件,然后,在最佳条件下,打印WF与PLA质量比为11：100的WF/PLA复合材料,并且,将该材料的性能与FDM 3D打印PLA试样进行了对比。结果表明,当打印层厚度为0.1 mm、打印温度为220℃、打印速度为50 mm/s、填充密度为100%、沉积角度为0时,WF/PLA复合材料的力学性能最佳。在该工艺条件下,WF与PLA质量比为11：100的WF/PLA复合材料的拉伸强度、拉伸模量、弯曲强度、弯曲模量和冲击强度分别为纯PLA的89.61%、97.56%、82.86%、92.40%和95.04%,与纯PLA相比,复合材料的表面润湿性能较好,吸水率显著增大。     

PLA/nano-SiO_2/HA三元复合生物材料的力学及体外降解性能研究

采用3D打印技术制作聚乳酸/纳米二氧化硅/羟基磷灰石(PLA/nano-SiO_2/HA)三元复合生物材料,研究了复合材料的力学性能及其在磷酸盐缓冲溶液中的体外降解性能。结果表明:当nano-SiO_2含量为PLA/HA复合材料质量的2%时,三元复合生物材料的综合力学性能最好,其拉伸和弯曲强度分别是85.62 MPa、126.66 MPa。随着体外降解时间的延长,三元复合生物材料的拉伸及弯曲强度将下降,但即使如此,经历12周的体外降解试验后,所有强度保持率均在80%左右,且在降解试验过程中,降解液的pH值基本维持在7.35左右,说明PLA/nano-SiO_2/HA三元复合生物材料在缓冲溶液中具有足够高的强度,且对环境影响较小,有望应用于一些组织工程中。     

连续玻璃纤维增强PLA复合材料3D打印技术研究

以聚乳酸(PLA)为基体,连续玻璃纤维为增强体,采用熔融浸渍工艺制备连续玻璃纤维预浸丝,将制得的预浸丝作为3D打印耗材用于熔融沉积(FDM)的3D技术来制备连续玻璃纤维增强PLA复合材料试样,并研究了打印温度、层厚和打印速度对复合材料力学性能的影响。结果表明,当打印层厚为0. 5 mm,打印温度为230℃,打印速度为2 mm/s时,连续玻璃纤维增强PLA复合材料的弯曲性能最佳,弯曲强度和弯曲模量分别为327. 84 MPa和20. 293 GPa。综合考虑复合材料的力学性能、表面质量和尺寸稳定性,连续玻璃纤维增强PLA复合材料的最佳打印层厚为0. 5 mm,适宜的打印温度范围为200~220℃,打印速度范围为2~4 mm/s。     

用于FDM的PLA共混改性

采用酰胺成核剂(NT–C)和聚乙二醇(PEG2000)对聚乳酸(PLA)进行熔融共混改性,制备了用于3D打印的PLA/NT–C/PEG2000共混物,并在200℃的温度下通过熔融沉积成型(FDM)工艺制备了共混物FDM打印件。研究了NT–C的用量对PLA/NT–C打印件结晶性能的影响,并在此基础上研究了PEG2000用量对共混物流变性能、共混物打印件的结晶性能和力学性能的影响。差示扫描量热分析表明NT–C可在一定程度上提高PLA/NT–C打印件的结晶度,一定用量的PEG2000的添加进一步提高了共混物打印件的结晶性能,当NT–C和PEG2000的质量分数分别为2%和5%时,打印件的结晶度达到17.1%,相比PLA提高了12倍;流变性能测试表明PEG2000提高了共混物的熔体流动速率,降低了共混物储能模量和损耗模量对温度的依赖性,扩宽了PLA在FDM工艺中的成型温度;力学性能测试表明PEG2000显著提高了PLA/NT–C/PEG2000共混物的缺口冲击强度,降低了打印中断丝的几率,FDM打印件弯曲和拉伸强度相比于PLA也有显著提高,当NT–C和PEG2000的质量分数分别为2%和5%时,打印件的弯曲和拉伸强度分别达到了注塑件的80%和70%以上,扩宽了PLA在FDM中应用。     

改性油茶壳粉增强聚乳酸3D打印材料性能研究

以废弃油茶壳（COS）为原料,经过碱和硅烷偶联剂处理后,制得改性COS。将改性COS与聚乳酸（PLA）经熔融共混挤出、拉丝,制备适用于熔融沉积成型（FDM）的改性COS/聚乳酸（PLA）3D打印材料,对其力学性能、热学性能、打印性能等进行探讨。结果表明：采用碱和硅烷偶联剂改性COS,可以显著提高COS的初始热分解温度,也提高改性COS/PLA 3D打印材料的热稳定性。当改性COS的质量分数为3%,改性COS/PLA 3D打印材料的弯曲强度和拉伸强度最大分别为66.97 MPa和53.57 MPa,相比纯PLA分别提高15.19%和12.05%,而且聚合物的结晶度提高15.6%。通过FDM 3D打印技术成功制备了个性化艺术品,打印效果良好。     

PLA/改性MMT复合材料的性能

以十六烷基三甲基溴化铵(CTAB)为改性剂对蒙脱土(MMT)进行改性,将其填充到聚乳酸(PLA)中,采用熔融插层法制备了PLA/改性MMT复合材料,并研究了复合材料的性能。结果表明:添加MMT可提高复合材料的阻燃性能和耐热性能;添加未改性MMT降低了复合材料的力学性能,当其用量为9 phr时,复合材料的拉伸强度从42.1 MPa降至38.6 MPa,断裂拉伸应变从4.5%降至2.2%,冲击强度从15.2 kJ/m~2降至8.6 kJ/m~2;添加适量(3~5 phr)改性MMT可提高复合材料的力学性能,当其用量为5 phr时,复合材料的拉伸强度和断裂拉伸应变均达最大值,分别为47.2 MPa和10.6%,当其用量为3 phr时,复合材料的冲击强度达最大值,为25.2 kJ/m~2。     

纳米SiO_2包覆微晶纤维素对PLA/PBS复合材料性能的影响

以纳米二氧化硅(nano-SiO_2)表面包覆的微晶纤维素(MCC)为填料,采用熔融共混的方法制备了聚乳酸/聚丁二酸丁二醇酯(PLA/PBS)复合材料。运用扫描电子显微镜、热重分析仪、差示扫描量热仪、动态热力学分析仪等方法研究了nano-SiO_2对PLA/PBS/MCC复合材料的力学性能、热稳定性以及结晶行为的影响。结果表明,nano-SiO_2包覆在MCC表面后与PLA/PBS熔融共混提高了nano-SiO_2在聚合物材料中的分散性,改善了MCC与树脂基体的相容性;添加5%(质量分数,下同)MCC的PLA/PBS/MCC复合材料,与同样添加量的PLA/PBS/nano-SiO_2-MCC复合材料相比,其储能模量、冲击强度以及结晶度分别提高了13.04%、11.70%、71.92%。     

PLA/PHBV共混3D打印线材的制备及性能研究

采用熔融共混法制备了聚乳酸/聚(3-羟基丁酸-co-3-羟基戊酸酯)(PLA/PHBV)共混物,用熔融沉积成型(FDM)技术制备了三维(3D)打印标准测试样条,研究了PLA/PHBV质量比对PLA/PHBV共混物及3D打印线材性能的影响。结果表明,PLA/PHBV共混材料是完全不相容的体系,随着PHBV含量的增加,PLA/PHBV共混物以及3D打印制品的拉伸强度下降,但断裂伸长率有所提高;弯曲强度及冲击强度均先上升后下降;注塑样品的拉伸强度最大可达43.31 MPa,断裂伸长率可达5.37%;3D打印制品的拉伸强度最大可达49.16 MPa,断裂伸长率可达7.41%;PLA/PHBV共混物以及3D打印制品淬断断面呈现典型的"海岛"分布,PHBV相均匀的分散在PLA基中;随着PHBV含量的增加,注塑样条的断面逐渐变得粗糙,打印制品层与层之间空隙减小,填充率上升,黏结性能提高。     

豌豆秸秆粉增强聚乳酸基3D打印材料性能

以聚乳酸(PLA)和不同粒度豌豆秸秆粉(PSP)为原料,利用FDM-3D打印工艺制备了PSP/PLA复合材料。研究了纯PLA及PSP/PLA的密度、力学性能、表面润湿性能及不同温度下的吸水率。结果表明,相比于纯PLA,轻质PSP的添加使得复合材料的密度减小并保持在1. 04 g/cm~3附近; 120目PSP/PLA复合材料的拉伸和弯曲性能最优,拉伸强度和拉伸模量分别是纯PLA打印试样的86. 95%和90. 70%,弯曲性能与纯PLA打印材料相当,弯曲强度与纯PLA打印试样相比仅相差0. 53%;随着PSP粒度的减小,3D打印复合材料的表面接触角逐渐减小,当PSP粒度为200目时,接触角降低至84. 93°,疏水性减弱而亲水性增强;复合材料吸水率高于纯PLA,且比纯PLA更易受温度影响,120目PSP/PLA吸水率最低。     

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.     

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.     

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.     

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.