应用于3D打印的聚乳酸/淀粉复合材料的制备及表征

将聚乳酸/淀粉进行充分混合,熔融物料用于制备复合材料。测试了复合材料的力学性能参数、吸水率及SEM电镜扫描等,考察了增溶剂MAPP的添加对复合材料性能的影响。实验结果表明,提高复合材料中淀粉的比例,其力学性能会下降,吸水率增大;复合材料断层面的脆性断裂特征表明,添加MAPP能明显优化复合材料的力学性能。     

改性淀粉/聚乳酸复合材料的制备与性能表征

采用接枝共聚-共混法制备了丙烯酸接枝淀粉/聚乳酸复合材料。通过拉伸强度测试、红外光谱、X射线衍射以及扫描电镜等对共混物进行分析,研究了复合材料的力学性能、结晶性、吸水性以及降解性能。结果表明,相对于未改性的淀粉/聚乳酸材料,经过接枝丙烯酸的淀粉/聚乳酸复合材料拉伸强度提高,结晶度减小,吸水性增加。SEM分析表明,经丙烯酸接枝改性后的淀粉与聚乳酸之间的相容性有较大提高,降解速率变缓。     

甘油对聚乳酸／淀粉复合材料机械性能的影响

聚乳酸是一种生物降解高分子材料,具有良好的透明性、良好的机械性能和易于加工的优点,但是比较昂贵,为了降低成本,加人廉价的其他材料,制得复合材料是一种可选择的方式.淀粉来源广泛,而且价格低廉,是一种天然的可降解高分子,因此将聚乳酸和淀粉进行共混制的复合材料能够有效的降低成本.但是聚乳酸/淀粉复合材料的韧性比较差,这限制了它的应用.在聚乳酸和淀粉80:20(质量比)的情况下,我们向复合材料中加入甘油,改善复合材料的韧性.分别加入0%、8%、16%、24%和32%的甘油,我们采用熔融共混的方法制备了聚乳酸/淀粉复合材料.通过力学性能测试和SEM等分析,研究了在不同甘油含量的情况下,复合材料力学性能.通过研究发现,随着甘油含量的增加,复合材料力学性能先上升后下降,当甘油加入量为8%(淀粉质量)时,性能最好.SEM分析表明,甘油的加入能够改善聚乳酸/淀粉复合材料的相容性.     

短亚麻纤维/聚乳酸复合材料制备与性能研究

采用双螺杆挤出机制备出一系列短亚麻纤维/聚乳酸复合材料,通过力学性能测试、SEM和DSC等方法研究了短亚麻纤维用量、偶联剂种类对短亚麻纤维/聚乳酸复合材料力学性能、结晶性能、流变性能和耐热性能的影响。结果表明:短亚麻纤维用量达到4.62%时,亚麻纤维/聚乳酸复合材料力学性能达到最佳;随短亚麻纤维用量的增加亚,麻纤维/聚乳酸复合材料流动性降低而,结晶度和耐热性有所提高。     

淀粉/聚乙烯醇/蒙脱土复合材料的制备及性能研究

采用熔融挤出法制备了淀粉/聚乙烯醇/蒙脱土三元复合材料。通过对力学测试、DSC、SEM、维卡软化点的分析,研究了PVA和酸酐的含量对材料的力学性能、热性能、吸水率的影响,并讨论了蒙脱土的加入对体系性能的影响。研究发现,适量的顺丁烯二酸酐能够降低淀粉分子链间的氢键作用,并促使其晶区的破坏,从而改善淀粉的加工性能、力学性能以及耐水性,当加入2.5%顺丁烯二酸酐时,材料的拉伸强度提高了60.54%;随着PVA含量的增加,体系力学性能增强,吸水率降低。蒙脱土的加入改善了其加工性能,并有效地提高了材料的力学性能、耐水性以及热稳定性。SEM显示,复合材料各组分之间的相容性较好,淀粉得到良好的塑化。     

木质素/木粉/聚乳酸复合材料的制备及其性能

利用熔融共混的方法,以聚乳酸(PLA)为基材,填充木质素和木粉对其力学性能进行增强,通过控制木质素和木粉的比例制备了5种不同的木质素/木粉/聚乳酸复合材料。通过FTIR、XRD、TGA、SEM等测试方法研究了木质素含量、木粉含量对复合材料界面相容性、热性能、力学性能以及吸水率的影响。结果表明:以70%PLA作为基体,木质素与木粉以7∶3的质量比例填充30%到PLA中,此时复合材料的界面相容性较好,综合力学性能优异,其中拉伸强度和弯曲强度分别达到最高,为65. 59和5 916. 04 MPa,弯曲模量为124. 53 MPa;饱和吸水率表现出较好的吸水性能,为5. 72%。该研究结果对木质素/木粉/PLA复合体系的研究与应用具有一定的参考作用。     

马来酸酐接枝共聚物增容聚乳酸/改性淀粉复合材料的制备与性能研究

采用熔融共混方法制备聚乳酸/改性淀粉复合材料。研究了不同含量的马来酸酐接枝共聚物对聚乳酸/改性淀粉复合材料力学性能的影响,并且采用差示扫描量热(DSC)仪和扫描电子显微镜(SEM)对复合材料的微观结构进行分析。结果表明,马来酸酐接枝共聚物的加入改善了聚乳酸与淀粉的相容性,提高了复合材料的力学性能,添加量为0.5份时复合材料的拉伸强度提高了61.6%,断裂伸长率提高了53.1%,弯曲强度提高了104.7%,同时还能提高复合材料的热变形温度和耐水性;改性淀粉与聚乳酸两相紧密连接。     

聚乳酸/DMSO增塑淀粉复合材料的制备与表征

采用聚乳酸分别和纯淀粉及二甲基亚砜(DMSO)塑化淀粉进行共混制备了淀粉/聚乳酸复合材料,通过力学性能测试,DSC测试,TG分析及SEM观察发现淀粉含量增加,材料力学性能降低,而经DMSO塑化淀粉共混物虽然其拉伸强度等力学性能降低,但冲击强度和弯曲应变均提高,且复合材料结晶度有较大提高,DMSO质量分数为3%时,复合材料的冷结晶温度降低9.4℃,熔融温度降低2.2℃。纯淀粉和聚乳酸共混复合材料呈现明显的两相结构,加入DMSO之后,界面黏结加强,呈现均相特征。     

交联对聚乳酸/淀粉/纳米二氧化硅复合材料力学性能的影响

采用熔融共混方法制备聚乳酸/淀粉/纳米二氧化硅复合材料,研究了交联对聚乳酸/淀粉/纳米二氧化硅复合材料力学性能的影响,并且采用扫描电子显微镜(SEM)对复合材料的微观形貌进行分析,结果表明:交联能提升淀粉/聚乳酸的界面相容性,并能提高其力学性能,聚乳酸/淀粉/纳米二氧化硅的重量比例为70/20/10时,引发剂及交联剂添加量分别为0.1 phr及0.3 phr时,复合材料的拉伸强度及断裂伸长率分别提高为21.49 MPa及216.74%。     

橡实淀粉/聚乳酸复合材料的制备与结构性能研究

采用熔融挤出法制备了橡实淀粉 (AS)/聚乳酸 (PLA)二元复合材料。通过对复合材料力学性能、吸水性、熔融指数 (MIR)、扫描电镜 (SEM)、动态机械热分析 (DMA)和热稳定性 (TG)的测试,研究了橡实淀粉含量对复合材料的力学性能、疏水性能和热性能的影响。研究表明,随着AS加入量的增加,复合材料的刚性逐渐增强,在AS质量分散50%的情况下,拉伸强度仍达47.19 MPa。熔融流动性能、拉伸和弯曲强度则略微有所下降,其玻璃化转变温度略向高温偏移,保持在57 ℃。制备的复合材料具有优异的疏水性能,即使在AS加入量高达50%的情况下,接触角可达63.26°,吸水率仅为2.68%。     

遇水崩解型聚苯乙烯崩解机理及性能

采用原位共混聚合的方法将反相乳液聚合得到的交联聚丙烯酸钠吸水树脂微粒混入聚苯乙烯材料中,得到聚苯乙烯/聚丙烯酸钠共混物(PS/PAANa),共混物遇水后会崩解成含水凝胶的聚苯乙烯粉末,并失去机械强度。用扫描电镜观察材料水崩解前后的微观结构,并研究了材料的崩解机理。测试了材料的力学强度和水崩解产物的吸水性能。结果表明:此材料的崩解机理为在分散剂Span-80的作用下,吸水树脂吸水后膨胀导致基体聚苯乙烯出现银纹并扩展为裂缝,裂缝继续扩展,最终导致基体崩解为粒径0.05～0.2mm的粉末;PS与PAANa原位共混后,力学强度提高;共混物的崩解产物吸水倍率可达26倍。     

PA-6/UHMWP/EHDPE-g-MAH共混合金的形态结构与性能的研究

通过SEM观察和机械性能测试,研究了PA 6 UHMWPE HDPE g MAH共混合金的形态结构和性能。结果表明:加入HDPE g MAH可有效地改善共混物的相容性,增强两相界面间的粘结强度,降低分散相尺寸;同时还改善了共混物的机械性能,降低了熔体流动速率,提高了常温和低温冲击强度,降低了吸水率。     

Mechanical properties of poly(lactic acid) and wheat starch blends with methylenediphenyl diisocyanate

Poly(lactic acid) (PLA) and wheat starch are biodegradable polymers derived from renewable sources. A previous study showed that thermally blending starch and PLA in the presence of methylenediphenyl diisocyanate (MDI) enhanced the mechanical properties of the blends. In this work, blends of PLA with various levels of wheat starch and MDI were hot mixed at 180°C then hot‐pressure molded at 175°C to form test specimens. The blends were characterized for mechanical properties, fracture microstructure, and water absorption. Pure PLA had a tensile strength of 62.7 MPa and elongation of 6.5%. The blend with 45% wheat starch and 0.5 wt % MDI gave the highest tensile strength of about 68 MPa with about 5.1% elongation. The blend with 20% starch and 0.5 wt % MDI had the lowest tensile strength of about 58 MPa with about 5.6% elongation. Dynamic mechanical analysis showed that storage modulus increased and tan δ decreased as starch level increased, but almost leveled off when starch level reached 45% or higher. Water absorption of the blends increased significantly with starch content. Yet the blend, if water proofed on its surface, has potential for short‐term disposable applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1257–1262, 2002; DOI 10.1002/app.10457     

Enhanced performance of urea–glyoxal polymer with oxidized cassava starch as wood adhesive

To eliminate the hazard of formaldehyde from wood-based products to human and environment, formaldehyde was replaced by glyoxal to produce wood adhesive. Urea–glyoxal (UG) resin was environmental friendly, while its bonding strength was very poor, especially its water resistance. The object of this work was to improve the mechanical properties of UG resin by oxidized cassava starch addition. Hence, the urea–glyoxal (UG) resin was synthesized and the oxidized cassava starch was added through mechanical mixing. The bonding strength, structure distributions, and the morphology features of the cured UG resin system were investigated by producing a three-layer plywood, FTIR, and SEM analysis. The results of dry and wet shear strength of plywood indicated that there was a positive effect of oxidized cassava starch on bonding strength of a three-layer plywood, and when the oxidized cassava starch content was increased to 45%, the dry strength could reach 1.21 MPa, and the wet strength was 0.72 MPa. The FTIR results showed that chemical reaction between UG resin and oxidized cassava starch was beneficial to the branched structure formation and higher cohesion strength of UG resin. Meanwhile, the tightness structure of enhanced UG resin system was observed by SEM analysis as well. These improved properties were contributed to water resistance improvement of UG resin.

     

Properties of extrusion cast sheets of blends of natural and aliphatic polyesters

Natural and synthetic polymers of various compositions were blended in a twin‐screw extruder. These blends were then sheeted into thin sheets with a coat hanger die attached to a single‐screw extruder. The natural content in the blend was varied between 5 and 50 wt %, and the mechanical and morphological properties of the blends were evaluated. At 50 wt % natural content, the tensile strength decreased to a third of that of the synthetic polymer. The use of a compatibilizer doubled the tensile strength for the 50 wt % natural content blend. The sheets displayed equal strengths in the machine and transverse direction. The tear strength decreased as the natural content increased, and the decrease was greater in the anhydride‐compatibilized blends than in the uncompatibilized blends. The blends displayed two distinct glass transitions, one for each component, indicating phase separation. The crystallinity of the blends decreased as the starch content increased. This result was confirmed by differential scanning calorimetry (DSC), which showed that the melting endotherm decreased as the starch content increased. Gel permeation chromatography (GPC) results showed that the peak position was at the same location irrespective of blend composition, indicating minimal degradation of starch moieties. The water absorption was diffusion controlled, with a sharp initial burst of water uptake. Scanning electron microscopy (SEM) showed melting of starch granules that formed a co‐continuous phase with the synthetic polyester. Increasing the natural content also increased the surface roughness of the sheets. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1545–1554, 2003     

Blending of poly(lactic acid) and starches containing varying amylose content

Four dry corn starches with different amylose content were blended at 185°C with poly(lactic acid) (PLA) at various starch:PLA ratios using a lab‐scale twin‐screw extruder. Starch with 30% moisture content also was blended with PLA at a 1:1 ratio. Each extrudate was ground and dried. The powder was mixed with about 7.5% plasticizer, and injection molded (175°C) into test tensile bars. These were characterized for morphology, mechanical properties, and water absorption. Starch performed as a filler in the PLA continuous matrix phase, but the PLA phase became discontinuous as starch content increased beyond 60%. Tensile strength and elongation of the blends decreased as starch content increased, but no significant difference was observed among the four starches at the same ratio of starch:PLA. The rate and extent of water absorption of starch/PLA blends increased with increasing starch. Blends made with high‐amylose starches had lower water absorption than the blends with normal and waxy corn starches. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3639–3646, 2003     

The morphology,rheological, and mechanical properties of wood flour/starch/poly(lactic acid) blends

An entirely biosourced blend composed of poly(lactic acid) (PLA), starch, and wood flour (WF) was prepared by a co‐extruder with glycerol as a plasticizer. The morphology, rheological properties, and mechanical properties of the WF/starch/PLA blends were comprehensively analyzed. The results showed that with the decrease of the starch/WF ratio, the morphology experienced a large transformation, and the compatibility of the blends was found to be superior to other blends, with a starch/wood flour ratio of 7/3. The dynamic mechanical thermal analysis (DMA) results demonstrated the incompatibility of the components in WF/starch/PLA blends. Following the decrease of the starch/WF ratio, the storage modulus (G″) and the complex viscosity (η*) of the blends increased. The mechanical strength first increased, and then decreased with the increase of the WF concentration. The water absorption results showed that the water resistance of the blends was reduced with the lower starch/WF ratio. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44743.     

Properties of blends of starch and synthetic polymers containing anhydride groups. II. Effect of amylopectin to amylose ratio in starch

Corn starch with different amylopectin to amylose ratios was blended with styrene maleic anhydride copolymer (SMA) and ethylene–propylene-g-maleic anhydride copolymer (EPMA). The starch had an amylose content of approximately 0, 50, and 70%. The concentration of starch in the blend was kept constant at 60% by weight. The samples were melt blended in a corotating twin screw extruder. Scanning electron micrographs showed that the amount of starch granules remaining in the samples varied with the torque. Optical micrograph showed that starch/EPMA blends formed a cocontinuous phase in all blends irrespective of starch variety. For starch/SMA blends, the starch granules remained dispersed in the SMA phase. The torque during blending, tensile strength, water absorption, storage and loss modulus, and data on biodegradability of the blends are presented. Tensile strength and water absorption correlated well with the torque generated during blending: the higher the torque, the lower the tensile strength and the higher the water absorption. The tensile strength of blends containing SMA decreased when the humidity increased. Fractured surfaces of starch/SMA blends exhibited brittle failure; for the ductile starch/EPMA blends, shear tearing appeared to be the major failure mechanism. For blends containing EPMA, the percentage elongation increased with increased humidity. Dynamic mechanical analysis of the blends showed two sharp peaks for tan δ vs. temperature plot for starch/EPMA plots, but showed a single peak for starch/SMA blends. Starch/EPMA blends had a higher percentage of water aborption that became constant after 20 days. Using the ASTM test method D5902, the starch content in the samples was found to degrade. © 1995 John Wiley & Sons, Inc.