聚氨酯弹性体分子结构对阻尼及力学性能的影响

为获得深水环境用减振降噪聚氨酯弹性体(PUE),选择甲苯二异氰酸酯(TDI)、聚丙二醇2000(PPG2000)和三乙醇胺(TEA)为原材料浇注制备了PUE,探究硬段含量、R值和合成方法对PUE阻尼性能和压缩模量的影响。结果表明：随着硬段含量的增加，PUE的tanδ峰值减小，压缩模量增强；随着R值的增加，T_g增大，压缩模量先增大后降低，R=2时达到峰值。预聚体法和一步法对合成出PUE的tanδ的影响较小，但预聚体法合成PUE的压缩模量明显优于一步法。增加分子链刚度、氢键化程度和硬段微区分布均匀程度可以有效提升PUE的压缩模量，但会导致阻尼性能下降。     

一种硅氧烷杂化聚氨酯弹性体的制备及动态力学性能

用4,4′-二苯基甲烷二异氰酸酯(MDI)、聚四氢呋喃醚二醇和γ-氨丙基三乙氧基硅烷(KH550)为主要原料,制备出新型硅氧烷杂化聚氨酯弹性体。通过红外光谱,动态力学分析,原子力显微镜等研究了产物的结构及性能。结果表明,不同于传统二胺或二醇扩链的聚氨酯弹性体硬段晶区的片层结构,硅氧烷杂化聚氨酯弹性体硬段区为三维网络状结构,受力时不易破碎和滑移,其软段玻璃化转变温度较4,4′-二氨基二苯甲烷(MDA)扩链型弹性体向低温方向移动9℃,具有更完整的相分离程度和更低的力学损耗。     

硬段结构对3,3-双(叠氮甲基)环氧丁烷-四氢呋喃共聚醚弹性体力学性能的影响EI北大核心CSCD

以3,3-双(叠氮甲基)环氧丁烷-四氢呋喃共聚醚(PBT)为软段,不同异氰酸酯和扩链剂为硬段,以一步法合成了不同硬段结构的聚氨酯弹性体。采用广角X射线衍射对其结构进行表征,表明刚性扩链剂(SR)制备的弹性体衍射峰强度比柔性扩链剂(DEG)制备的弹性体强,表明其硬段排列较规整。进一步采用常温拉伸、高温蠕变和低温动态力学分析等手段对其进行了不同温度的力学性能测试,结果显示SR扩链后弹性体拉伸强度达到5.36 MPa,较DEG扩链弹性体的2.29 MPa有很大提高,初始分解温度前者(208℃)也高于后者(198℃),高温蠕变量也从90.1%降到39.7%;与扩链剂相比,异氰酸酯结构对力学性能的影响较小,由包含对称结构的甲苯二异氰酸酯(TDI)固化的弹性体拉伸强度(5.36 MPa)比4,4’-二苯基甲烷二异氰酸酯(MDI)固化的弹性体(3.16 MPa)高,低温和高温性能相差不大。     

硬段结构对3,3-双(叠氮甲基)环氧丁烷-四氢呋喃共聚醚弹性体力学性能的影响

以3,3-双(叠氮甲基)环氧丁烷-四氢呋喃共聚醚(PBT)为软段,不同异氰酸酯和扩链剂为硬段,以一步法合成了不同硬段结构的聚氨酯弹性体。采用广角X射线衍射对其结构进行表征,表明刚性扩链剂(SR)制备的弹性体衍射峰强度比柔性扩链剂(DEG)制备的弹性体强,表明其硬段排列较规整。进一步采用常温拉伸、高温蠕变和低温动态力学分析等手段对其进行了不同温度的力学性能测试,结果显示SR扩链后弹性体拉伸强度达到5.36 MPa,较DEG扩链弹性体的2.29 MPa有很大提高,初始分解温度前者(208℃)也高于后者(198℃),高温蠕变量也从90.1%降到39.7%;与扩链剂相比,异氰酸酯结构对力学性能的影响较小,由包含对称结构的甲苯二异氰酸酯(TDI)固化的弹性体拉伸强度(5.36 MPa)比4,4’-二苯基甲烷二异氰酸酯(MDI)固化的弹性体(3.16 MPa)高,低温和高温性能相差不大。     

聚氨酯弹性体结构和性能的研究——Ⅰ.链延伸剂对聚醚氨酯动态力学性能的影响EI

以端羟基聚环氧丙烷(PPO,(?)=1000)和MDI及不同结构的小分子二醇(链延伸剂)用分步法合成了聚醚氨酯弹性体,乒对该弹性体的动态力学性能进行了测试(DDV-Ⅲ-EA)。结果表明:链延伸剂对聚氨酯弹性体的动态力学性能影响颇大,通过改变链延伸剂的结构来改变聚氨酯链中的硬段结构,会导致其硬段间作用(物理相互作用)发生很大改变。因而不同程度地拓宽其阻尼峰,选择适当结构的聚氯酯链延伸剂所合成的弹性体具有化良的阻尼性能,是一类极有前途的粘弹性阻尼材料。     

聚氨酯弹性体结构和性能的研究——Ⅰ.链延伸剂对聚醚氨酯动态力学性能的影响

以端羟基聚环氧丙烷(PPO,(?)=1000)和MDI及不同结构的小分子二醇(链延伸剂)用分步法合成了聚醚氨酯弹性体,乒对该弹性体的动态力学性能进行了测试(DDV-Ⅲ-EA)。结果表明:链延伸剂对聚氨酯弹性体的动态力学性能影响颇大,通过改变链延伸剂的结构来改变聚氨酯链中的硬段结构,会导致其硬段间作用(物理相互作用)发生很大改变。因而不同程度地拓宽其阻尼峰,选择适当结构的聚氯酯链延伸剂所合成的弹性体具有化良的阻尼性能,是一类极有前途的粘弹性阻尼材料。     

聚天冬氨酸酯聚脲的动态力学性质及结构形态的温度依赖性

运用动态力学分析(DMA)、原子力显微镜(AFM)和Fourier变换红外光谱(FT-IR)研究了聚天冬氨酸酯(PAE)聚脲的动态力学性质和结构形态的温度依赖性。研究表明,当固化温度由20℃升至80℃时,PAE聚脲的低温和高温储能模量(E′)以及硬段玻璃化转变温度(Tgh)逐渐提高,微相分离程度也逐渐增大;脲羰基的总氢键化程度由74.3%增至82.1%,而NH基氢键键长则由0.307nm减至0.303nm,硬段结构规整度提高,软段与硬段的相容性降低;借助AMF直观地观察到了PAE聚脲的微相分离结构,并证实了固化温度对微结构的影响。提高固化温度可以改善涂层的微观结构,从而提高涂层的动态力学性质。     

一种含能热塑性聚氨酯弹性体的性能

采用熔融二步法合成了以聚叠氮缩水甘油醚(GAP)为软段、以2,2-二叠氮甲基-1,3-丙二醇和二环已基甲烷二异氰酸酯(HMDI)为硬段的含能热塑性聚氨酯弹性体(ETPUE),通过红外光谱(FT-IR),差示扫描量热(DSC),动态力学性能测试(DMA)及力学性能测试对材料进行了结构和性能的表征.结果表明,所合成的不同硬...     

聚碳酸酯型聚氨酯脲弹性体的合成与表征

以聚碳酸酯二醇(PCDL),六亚甲基二异氰酸酯(HDI)为预聚原料,3,3′-二氯-4,4′-二氨基二苯甲烷(MOCA)为扩链剂,两步法合成了一系列不同硬段含量的聚氨酯脲(PUU)弹性体。采用傅里叶变换红外光谱仪(FTIR)、强力拉伸仪等测试手段对其结构特征和材料的力学性能以及耐水性能进行了研究。结果表明,随着硬段含量的增加,材料的拉伸强度先增大后减小最后又增大,而断裂伸长率和吸水率呈现相反的趋势,并以硬段含量47%为分界点。     

聚四氢呋喃醚二醇/聚氧化丙烯二醇共混聚醚聚氨酯弹性体的氢键作用

分别以聚四氢呋喃醚二醇(PTMG)、聚氧化丙烯二醇(PPG)及两者共混物PTMG/PPG作为软段,以2,4-甲苯二异氰酸酯(TDI-100)和扩链剂3,3'-二氯-4,4'-二氨基二苯甲烷(MOCA)作为硬段,采用预聚体法,制备了5种PTMG/PPG不同配比的浇注型聚氨酯弹性体。通过红外分析、差示扫描量热分析、动态力学热分析着重研究了PTMG/PPG不同配比对聚氨酯弹性体氢键的影响。结果表明,随着PPG型预聚体在混合预聚体中的含量增加,聚氨酯中羰基区总氢键度及脲羰基氢键度变化不大,氨酯羰基氢键度呈现先增加后减小的趋势;氨酯羰基氢键解离活化能变大,氢键趋于完善;硬段相长程有序结构熔融焓减小,脲羰基氢键完善程度下降。     

多臂型端酯基聚叠氮缩水甘油醚的合成与表征

分别以丙三醇、季戊四醇为起始剂,四氯化锡为催化剂,环氧氯丙烷阳离子经开环聚合得到两种不同多臂型端羟基聚环氧氯丙烷(PECH-OH),其端羟基经酯化改性、氯甲基侧基的氯被叠氮基取代,得到两种不同多臂型GAPE。对多臂型GAPE进行傅里叶红外光谱(FT-IR)、凝胶色谱(GPC)、热失重(TG)和差示扫描量热(DSC)表征。结果表明,GAPE-3和GAPE-4的分子量分别是890和1260,玻璃化转变温度分别是-55.2℃和-53.9℃,GAPE的热分解过程为叠氮基热分解和聚醚主链热分解两个相对独立的阶段。     

环氧树脂与氰酸酯共固化产物性能的研究

用DSC,介电和动态力学等分析方法研究了组成对乙酰丙酮过渡金属络合物催化促进的环氧树脂与氰酸酯共固化反应体系反应动力学参数,固化产物力学、电气和耐热性能以及玻璃化转变温度的影响。结果表明,随着共固化反应体系中氰酸酯含量的增加,其表观反应活化能和频率熵因子均随之升高;在相同的固化条件下,共固化产物中三嗪环结构含量增加,聚醚结构减少,玻璃化转变温度升高,耐热性能、介电性能提高。      

Influence of polyols on properties of bio-based polyurethanes

Polyurethane elastomers from cardanol-based polyol, polypropylene glycol (PPG-1200 and PPG-2000) and isophorone diisocyanate were prepared in the form of thin sheets. The sorption, mechanical and thermal properties were studied. The solubility parameter and molecular weight between crosslinks of polyurethane samples were calculated from swelling experiments. The swelling study of polyurethanes revealed that the sorption is found to decrease with an increase in chain length of PPG. The stress?Cstrain data showed that the elastomers obtained using PPG-1200 gave the best mechanical properties. The thermal degradation of all the three elastomers starts almost at 270 $^{\boldsymbol\circ}$ C, regardless of the PPG chain length. The value of activation energy of degradation calculated using the Broido method was in the range of 40?C70?kJ/mol.     

微量磷(P)对等原子比NiAl的微观组织与力学性能的影响

研究了微量P对挤压态等原子比NiAl的微观组织与高温力学性能的影响.结果表明:微量P的添加对NiAl的晶格常数有一定的影响,P偏聚于NiAl晶界处;并对其高温延伸率有重要影响.P偏聚于晶界阻碍了合金变形过程中的动态回复和再结晶,加剧了晶界处孔洞的形成,造成了NiAl-P合金与二元NiAl合金高温力学性能的显著差异,主要表现在:应力-应变曲线经历了较长的加工硬化阶段;最大延伸率明显下降;变形激活能升高,应变速率敏感指数下降.NiAl-P合金的高温变形机制为变形过程中位错的滑移与攀移共同作用.     

Impact of aging conditions on mechanical properties of thermoplastic polyurethane

In this study, impact of environmental aging conditions on the mechanical properties of thermoplastic polyurethane (TPU) was investigated. Especially, effect of temperature on water diffusion has been studied. Water-sorption experiments, tensile test and dynamic mechanical thermal analysis (DMTA) were performed after immersion in distilled water at different temperatures (25, 70 and 90 °C). The sorption process was analyzed by gravimetric measurements at different temperatures. Also, diffusion coefficients of solvent molecules in the TPU samples were identified. Therefore the activation energy and the mixing enthalpy were deduced. The aging impact on some mechanical properties of this material has been investigated after various aging cycles. Degradation of mechanical properties was observed. In fact, elastic modulus and stress at 200% of strain were decreased. It was also shown that such degradation largely depends on both aging temperature and aging immersion duration. The storage modulus (E′) was also affected by the hygrothermal (HT) environment. The modification of mechanical properties seems to be well correlated to structural observations obtained from scanning electron microscopy (SEM) photographs. Finally, through thermal aging experiments, it was deduced that the combination of temperature with water seems to be a major factor of TPU degradation.     

木粉/聚丙烯木塑复合泡沫材料吸能特性

采用模压法制备木粉/聚丙烯复合泡沫材料,并对不同木粉含量的泡沫材料进行静态压缩、循环压缩、压缩蠕变、动态热机械分析的测试,探讨了不同木粉含量的木粉/聚丙烯复合泡沫材料的能量吸收效果。结果表明: 随着木粉含量的增加,木粉/聚丙烯木塑复合泡沫材料的能量吸收量、能量吸收效率参数、松弛率、循环损耗量、动态力学性能等均呈先升后降的趋势,在木粉质量比为30%时泡沫材料吸能性能达到最佳。     

颗粒Al_2O_3增强环氧树脂复合材料的微波固化动力学及性能

利用Avrami法研究了Al_2O_3颗粒及其添加量对E51/DDS体系的微波固化表观活化能的影响,采用差示扫描量热、动态力学分析、力学性能测试和扫描电子显微镜等试验手段对产物的热性能、力学性能及微观形态进行研究。结果表明,Al_2O_3颗粒增强E51/二氨基二苯砜(DDS)体系可以显著降低其微波固化的反应活化能,其中相比于未添加的体系,添加量达到40%时,其微波固化活化能降低了19.3%;加入Al_2O_3颗粒可以提高体系的玻璃化转变温度,增加幅度与添加量正相关;且体系的损耗模量随着添加量的增加而降低。拉伸和弯曲模量随着Al_2O_3添加量的增加而增加,而拉伸和弯曲强度则呈现先增加后减小的趋势。断面分析表明Al_2O_3颗粒的存在阻止了微裂纹的扩展,消耗更多的能量,提高了浇注体的力学性能。     

间苯二酚缩水甘油醚/间苯二甲胺体系的热机械性能和固化动力学

利用热分析技术对具有高温快速固化性能的间苯二酚缩水甘油醚/间苯二甲胺体系的热机械性能和表观固化反应动力学进行了研究。热机械性能分析(DMA和TMA)结果表明,间苯二酚缩水甘油醚/间苯二甲胺固化产物的玻璃化转变温度为83℃,室温下储能模量为2600 MPa,玻璃态热膨胀系数(α1)为54.9×10-6℃-1,橡胶态的线性热膨胀系数(α2)为177.9×10-6℃-1。通过恒温和非恒温模式差示扫描量热(DSC)测试得到体系的表观反应活化能为62.7 kJ/mol,由此估算出固化反应在160℃时仅需数秒即可完成。     

Investigation of in situ prepared polypropylene/clay nanocomposites properties and comparing to melt blending method

The morphological, physical and mechanical properties of polypropylene/clay nanocomposites (PPCNs) were prepared by in situ polymerization are investigated. Non-modified scmectite type clay (e.g. bentonite) was used to prepare bi-supported Ziegler–Natta catalyst of TiCl₄/Mg(OEt)₂/clay. Exfoliated PPCNs were obtained by in situ intercalative polymerization of propylene using produced bi-supported catalyst. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) micrograph were used to assess the clay morphology and dispersion of clay. The crystalline structures of PPCNs were characterized by differential scanning calorimetry (DSC). The mechanical properties of PPCNs were studied by tensile and impact tests. thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis DMTA were used to characterize the thermal and dynamic mechanical properties, respectively. The thermo-mechanical properties of prepared nanocomposites were considerably improved by introducing small amount of clay, which indicated that the clay most be significantly intercalated or exfoliated in the prepared nanocomposite preparation process. In addition, morphology and some of the mechanical and thermal properties of in situ PPCNs were compared with those of PPCNs prepared by melt blending method in this study and some presented reported results in literatures.     

Mechanical characterization by dynamical tensile loading of 2017 aluminium alloy joints welded by diffusion bonding

The mechanical properties of diffusion-welded joints of 2017 aluminium-copper alloys have been studied under dynamic loading with the help of a Hopkinson bar linear assembly. With the aim of comparing with previous results obtained under static loading, the strength, failure elongation and failure energy were evaluated in the welding temperature range from 475 to 600 °C. Measurements of the above mechanical properties were also performed on treated specimens which were base-material specimens subjected to the same thermal cycle as the welded samples. It was found that for a welding temperature above 525 °C the strength of the welded joints could reach values of the same order of magnitude as those of the treated samples. In contrast, the failure elongation and failure energy remained clearly lower, whatever the welding temperature was. For a given value of the welding pressure, the welding temperature dependence rate of the dynamic strength was shown to be increased with increasing welding time. With regard to the failure elongation or the relatively weak influence of the welding pressure on the joint strength, the spread in the experimental results (probably arising from the brittle nature of the sample failure mode) does not allow a clear conclusion. In spite of this restriction, it can be concluded that differences in the mechanical properties of the diffusion-welded joints could be evidenced by dynamic loading tests, even if no significant differences could be observed under static loading.