L-丙交酯/ε-己内酯配比对共聚物微结构和性能的影响

辛酸亚锡催化下开环聚合制备不同物质的量比L-丙交酯/ε-己内酯(LLA/CL)共聚物。核磁共振(1H和13C-NMR)结果表明,共聚物组成与投料比基本一致,聚合过程中酯交换反应导致序列结构重新分布,二级酯交换系数(TII[CLC])随CL用量增加而增大。共聚物组成明显影响单元序列长度,各序列长度随相应单体投料量增加而增大,CL投料比≤50%的平均序列长度(LLL和LC)与相应的无规序列长度(LRC和LRLL)较接近,共聚物趋于无规分布。差示扫描量热(DSC)和广角X射线衍射(WAXD)表明共聚物是结晶态聚合物,结晶性与单元序列长度密切相关。共聚物组成显著影响其力学性能,随CL物质的量分数增加,且≤35%时表现出屈服形变的特点,具有热塑性弹性体的特征。     

L-丙交酯-乙交酯-ε-己内酯共聚物模压工艺的正交设计

以L-丙交酯、乙交酯和ε-己内酯为原料开环聚合合成三元共聚物PLLGC。通过正交试验设计研究了预热温度、模压压力、模压温度、模压时间等因素对PLLGC模压材料性能的影响,确定了PLLGC材料最佳的模压工艺。研究了不同因素对PLLGC模压材料的拉伸强度、密度、模压后分子量及分子量分布的影响,通过极差分析结果表明,PLLGC三元共聚物的最佳模压工艺条件:预热温度为150℃,模压压力为8 MPa,模压温度为100℃,模压时间为10 min。     

ε-己内酯与DL-丙交酯共聚物的体外降解性能研究

系统研究了ε-己内酯与DL-丙交酯共聚物(PCDLA)在磷酸盐缓冲液(PH=7.4,37℃)中的降解性能。用失重率、分子量、热学性能等指标对降解性能进行评价,并对PCDLA8020薄膜表面形貌采用扫描电镜(SEM)进行了观察。研究表明:随着PCDLA共聚物组分中DL-丙交酯含量的增加,降解速度明显增快,这为PCDLA共聚物的进一步应用提供了指导意义。     

聚己内酯/聚乙二醇/聚丙交酯两亲性共聚物纳米胶束的制备与表征

合成了两亲性聚己内酯-乙二醇-丙交酯(PCELA)三嵌段共聚物,采用沉淀法制备了粒径范围在40～120nm的PCELA纳米胶束.以芘为探针,利用荧光探针技术、动态光散射(DLS)、透射电镜(TEM)研究了PCELA在水中的行为.结果表明,临界胶束浓度(CMC)随着PCL-PLA/PEO的比率增大而增大,胶束粒径受到PCL-PLA/PEO比率和PCELA共聚物分子量的影响,胶束为具有核/壳结构的规则纳米球体.     

形状记忆聚乳酸/乙烯-乙烯醇共聚物的制备及性能

以辛酸亚锡(Sn(Oct)2)作为催化剂,采用熔融共混法制备了不同反应时间的聚乳酸(PLA)和乙烯-乙烯醇共聚物(EVOH)的共混物,通过扫描电镜、核磁共振、差示扫描量热、热重分析、动态力学分析、力学测试等研究了在不同反应时间下,Sn(Oct)2对PLA/EVOH共混物的结构和性能的影响。结果表明,Sn(Oct)2能促使PLA和EVOH之间发生酯交换反应,形成的共混物具有形状记忆效应,且随反应时间延长,反应程度逐渐增加,共混物逐渐失去结晶能力,材料的热稳定性降低;同时PLA和EVOH的相容性得到改善;另外共混物的形状记忆效应随反应程度增加而不断提高,形变回复率最高达100%。     

可生物降解高分子纳米微粒的制备及表征

以合成的聚己内酯（ＰＣＬ）、聚丙交酯（ＰＬＬＡ） 们的共聚物（ＰＣＬＬＡ）为材料,通过沉淀法制备了ＰＣＬ、ＰＬＬＡ、ＰＣＬＬＡ纳米微粒。透射电子显微镜和激光粒度仪分析表明,获得了纳米微粒具有较小的尺寸和粒径分布。同时还研究了水相温度、聚合物的分子量以及聚合物材料本身性质对纳米微粒粒径大小和分布的影响。     

PLLA-r-PCL无规共聚物的结构调控及热学性能、力学性能和气体阻隔性能

文中制备出不同组分比的PLLA-r-PCL无规共聚物薄膜,研究了其热学性能、力学性能和气体阻隔性能,探讨气体阻隔性能与共聚物结构之间的关系。通过红外光谱仪和差示扫描量热仪测试了材料的结晶性能。研究表明,随着PCL组分的增加,材料的结晶度呈降低趋势,薄膜材料几乎完全处于无定形态。采用拉力试验机对薄膜的力学性能进行测定,相较于纯PLLA,PLLA-r-PCL30的断裂伸长率达到了611%,为PLLA的70倍。同时,采用压差法透气仪对薄膜的透气性能进行了全面的分析,相较于纯PLLA,在40℃时,PLLA-r-PCL30的CO_2和O_2透过系数分别提高了801%和523%;在5℃时,PLLA-r-PCL30的CO_2/O_2的透过比(α(CO_2/O_2))达到7.0,提高了115%;此外,20℃时PLLA-r-PCL30的H_2O蒸汽透过率提高了354%。     

水蒸气辅助法制备LA-GA共聚物蜂窝状多孔膜

以D，L-丙交酯(LA)-乙交酯(GA)共聚物为膜材质，在高湿度气氛环境中使用溶液浇铸的方法在固体基板上制得具有蜂窝状孔结构的聚合物膜．发现不同组成比的LA—GA共聚物的亲水性对形成蜂窝状结构具有关键的影响，同时这种蜂窝状结构可以通过改变成膜条件加以有效控制．     

聚L-乳酸/聚ε-己内酯嵌段共聚物的形状记忆效应

采用两步法合成聚L-乳酸/聚ε-己内酯(PCLA)嵌段共聚物,并通过红外光谱(FTIR)和凝胶渗透色谱(GPC)方法加以表征.采用差示扫描量热分析(DSC)、X射线衍射分析(XRD)和拉伸试验对PCLA嵌段共聚物的微观结构和形状记忆效应进行了系统的研究.研究结果表明PCLA嵌段共聚物中聚L-乳酸(PLLA)和聚ε-已内酯(PCL)链段可以单独结晶,共聚物中存在PLLA和PCL两种结晶相.同时,PCLA嵌段共聚物具有优异的形状记忆效应,其中PLLA结晶相作为物理交联点,PCL链段及PLLA无定型相作为可逆相.在变形量为200%时,获得最大的形状恢复率超过90%,恢复力接近4MPa.     

变形对 Cu-Al-Mn记忆合金相变滞后的影响

为了研究CuAlMn形状记忆合金的相变滞后效应,以Cu-Al10.61-Mn6.95(ω（B）/%）合金（A合金）与Cu-Al11.05-Mn6.81-Zn0.21(ω（B）/%）合金（B合金）为研究对象,应用电阻法测定其相变点,并利用X射线衍射谱标定其结构。结果表明,A合金主要由18R马氏体构成,B合金主要由9R马氏体构成,而9R马氏体结构的合金相变滞后温度远大于18R马氏体结构的合金。为了进一步研究变形对相变滞后温度的影响,对B合金进行了拉伸变形试验。研究发现,通过增大预变形量可以有效地提高滞后宽度。     

Peculiarities of the deformation of alloys with the shape memory effect in nonsteady cyclic loading

Strength of Materials -     

Intrinsic two-way shape memory effect in a Ni-Mn-Sn metamagnetic shape memory microwire

An intrinsic two-way shape memory effect with a fully recoverable strain of 1.0% was achieved in an as-prepared Ni_(50)Mn_(37.5)Sn_(12.5) metamagnetic shape memory microwire fabricated by Taylor-Ulitovsky method. This two-way shape memory effect is mainly owing to the internal stress caused by the retained martensite in austenite matrix, as revealed by transmission electron microscopy observations and highenergy X-ray diffraction experiments. After superelastic training for 30 loading/unloading cycles at room temperature, the amount of retained martensite increased and the recoverable strain of two-way shape memory effect increased significantly to 2.2%. Furthermore, a giant recoverable strain of 11.2% was attained under a bias stress of 300 MPa in the trained microwire. These properties confer this microwire great potential for micro-actuation applications.     

Transformation behaviour and one-way shape memory effect in Fe-Mn-Si shape memory alloys

Humboldt-Fellow, on leave from Centro Atomico Bariloche, 8400 Bariloche, and CRUB, Universidad National del Comahue, Argentina.     

Repeatable temperature memory effect of TiNi shape memory alloys

An incomplete transformation cycle induces a kinetic stop in the following complete transformation cycle in TiNi shape memory alloys. The kinetic stop can be regarded as a memory of the previous interruption temperature. This memory was generally believed to be a one-time phenomenon. Herein, we show that the temperature memory effect is actually a long-lasting phenomenon. Experimental results show that a repeatable temperature memory effect can be introduced into a TiNi alloy by a deformation lager than 12%. Deformation induced dislocations are considered a main factor to the persistence of the memory. The memory becomes more distinct with increasing numbers of the incomplete thermal cycle, but the memory becomes less distinct with increasing numbers of subsequent complete transformation cycling.     

TiNiCu形状记忆合金双向记忆效应研究

研究了热机械训练温度及定型处理温度对TiNiCu形状记忆合金弹簧双向记忆效应的影响。研究结果表明:在纯马氏体状态进行训练时,双向记忆恢复率随训练次数的增加而增加,并在一定的训练次数后达到饱和;在纯奥氏体状态进行训练,双向记忆恢复率随训练次数迅速增加到某一最大值后随训练次数的增加而减小;在马氏体和奥氏体混合相进行训练时,双向记忆恢复率随训练次数先增加而后减小。经过400～550℃×1h/AC定型处理及热机械训练后最大形状记忆恢复率随定型处理温度升高先增大然后减小。由于马氏体再取向时引入的位错有利于双向记忆效应,热诱发和应力诱发的马氏体变体数量不同,引起了在不同状态训练诱发的双向记忆效应随训练次数变化的差异。     

Burst character of thermoelastic shape memory deformation in ferromagnetic Ni-Fe-Ga-Co alloy

The shape memory deformation in single crystals of Ni₄₉Fe₂₇Ga₁₈Co₆ alloy under uniaxial compression conditions has been studied. It was found that samples in the martensite state deformed in the [110] and [100] directions exhibit strongly anisotropic properties. Despite virtually equal residual strain and the work of deformation in the two cases, the subsequent behavior of samples during shape recovery on heating at a constant rate is principally different. In the former case, the shape memory deformation exhibits a burst character and takes place at a temperature that is significantly higher than the martensite transformation temperature in the initial (undeformed) crystal. In contrast, the shape recovery in the latter case proceeds smoothly at a temperature that is only slightly higher than the martensite transformation temperature in the initial crystal. Due to the burst character of shape memory deformation, the crystal standing on a solid base acquires a velocity above 20 m/s. The results are quantitatively analyzed in terms of the theory of diffuse phase transitions.     

A shape memory effect swashplate heat engine

A novel heat engine based on the shape memory effect (SME) of helical NiTi wire and utilising the swashplate geometry is described. Measurements of engine power cycled through 12°C and 80°C water baths were as high as 3 W/kg, which compare favourably with more complex SME heat engines designs.