成核剂对聚丁烯结晶行为及力学性能的影响

考察了3种不同种类的成核剂对PB(聚丁烯)性能的影响,重点分析了其中2种成核剂对PB力学性能和结晶性能的影响。结果表明:随着成核剂用量的增加,PB的拉伸强度、弯曲强度和Shore D硬度总体呈现先升高再降低的趋势,而冲击强度首先呈现明显的下降,而后逐渐保持稳定;成核剂的加入明显提高了PB的结晶温度和结晶度,加快了结晶速率及晶型转变速率。     

β晶型成核剂对聚丙烯结晶行为和力学性能的影响

以2,6-苯二甲酸环己酰胺（TMB-5）为β晶型成核剂,采用熔融共混的方法制备β晶改性聚丙烯. 利用示差扫描量热仪、偏光显微镜、拉伸实验机以及冲击试验机对改性聚丙烯的微观结构、热性能、结晶性能、力学性能进行研究. 实验结果表明,在聚丙烯中添加β晶型成核剂进行改性后,由于成核剂在体系中起到了异相成核的作用,聚丙烯中部分晶型由α晶型向β晶型转变,改性聚丙烯的结晶温度向高温方向移动,且聚丙烯球晶尺寸明显减小,球晶之间无明显的边界. 随着β晶型成核剂含量的增加,改性聚丙烯的拉伸强度、弯曲强度和弯曲模量呈现先降后升的趋势,而其断裂伸长率和冲击强度呈先升后降的趋势,并且当β晶型成核剂含量为0.4份时,改性聚丙烯的拉伸强度、弯曲强度和弯曲模量为最小值,断裂伸长率和冲击强度达到最大值.     

增塑聚乳酸结晶形态与机理研究

通过分子量为400的聚乙二醇(PEG400)对聚乳酸(PLA)进行增塑,采用PLM、DSC、SALS以及力学性能测试的方法对聚乳酸和增塑聚乳酸进行了一系列结构和性能的研究.DSC分析表明:PEG400可以有效地降低PLA的玻璃化转变温度(Tg),说明增塑的PLA分子链活动性得到增强.PLM与SALS的结果表明PEG400显著提高了PLA的结晶能力和分子链的活动性.单轴拉伸结果表明:随着PEG400用量的增加,弹性模量和屈服强度都明显减小,而断裂伸长率却逐渐增加.说明PEG400加入达到了增塑的目的.     

成核剂对生物降解聚乳酸结晶行为的影响

采用DSC和POM对聚乳酸及聚乳酸／成核剂体系的结晶行为进行了研究。结果表明,一定温度范围下,等温结晶后的各样品在熔融时,均出现两个熔融峰。含滑石粉的样品出现两个熔融峰所需温度要比其它样品所需温度约低10℃。3种成核剂都有利于提高聚乳酸的结晶速度和结晶度,其中滑石粉的效果最显著。在125℃时滑石粉的加入使得t1／2从7．78min缩短到3．33min,tmax从7．84min缩短到3．18min;相同保温时间时（130℃,10min）,结晶度约提高了19％。而戍核剂对改变聚乳酸等温结晶过程的成核机理和生长方式无明显影响。     

PLLA／PEG共混物结晶行为研究

利用L桘丙交酯为原料开环聚合制备了左旋聚乳酸（PLLA ）,并利用傅里叶红外变换光谱仪（FTIR）表征其结构．利用偏光显微镜（PLM ）、差示扫描量热仪（DSC）以及X桘射线衍射仪（XRD）考察了PLLA、聚乙二醇（PEG）以及 PLLA/PEG 共混物的结晶行为．DSC结果表明,PL L A的结晶行为发生在升温过程,结晶峰温度为98℃,其熔融峰温度为157℃．对于PLLA/PEG共混物,当PLLA∶PEG为5∶5时两者都发生了结晶行为．利用偏光显微镜观察此共混物的结晶形貌发现,PL L A和PEG分别于95℃和35℃发生了分步结晶．     

高效β成核剂对聚丙烯结晶性能的影响

采用熔融共混法制备了全同聚丙烯(PP)与成核剂NE共混物,用差示扫描量热仪、偏光显微镜、数位冲击试验机和X射线衍射仪考查了成核剂NE对PP冲击性能及结晶的影响。结果表明,成核剂NE是一种有效的抗冲击β成核剂,在0.5‰(质量分数)用量有着最高的冲击强度,冲击强度可提升2.8倍。可作为一种棒状异相成核点,明显提高结晶温度,加快整体结晶速度,细化球晶。     

成核剂对LLDPE薄膜的结晶、透明及阻隔性能的影响

采用复配成核剂（TJSH）及山梨糖醇类成核剂（TM3）,分别与线性低密度聚乙烯（LLDPE）熔融共混吹塑制膜．借助偏光显微镜（PM）和差示扫描量热仪（DSC）,研究了LLDPE／成核剂的结晶性能与光学性能和阻隔性能的关系．结果表明：TJSH成核剂的加入提高了LLDPE的结晶度,使晶体结构细化,球晶尺寸明显减小、均匀细密,因而导致膜的雾度显著降低,阻隔性增加．     

PLA/CAB绿色复合材料相容性及结晶行为研究

通过溶液浇注法制备复合材料聚乳酸(PLA)/醋酸丁酸纤维素酯(CAB),采用差示扫描量热仪(DSC)测量了复合材料不同组分的玻璃化温度(Tg),采用偏光显微镜(PLM)观察不同组分在熔融状态下的形态及等温结晶形态。结果表明,PLA与CAB是不相容的,并且CAB对PLA的形核有显著的抑制作用。     

纤维状β成核剂对聚丙烯非等温结晶动力学的影响

明晰纤维状β成核剂作用下聚丙烯(PP)的非等温结晶过程,对提升PP的力学性能至关重要。本文通过控制自组装β成核剂TMB-5为点状和纤维状形态,对比研究纤维状TMB-5对PP非等温结晶动力学的影响。结果表明:实验条件下,TMB-5不仅可使PP择优形成β晶,还可促进PP在高温成核,提高PP的结晶速率;不同于点状形态,纤维状TMB-5诱导PP冷却结晶时,α晶易在β晶生长前端异相成核,打断初始晶体的生长,使PP表现出非典型的3段生长模式和相对更慢的结晶过程。     

聚乙二醇结晶及其低温能量储存行为研究

本文系统地研究了重均分子量（ＭＷ）为４００－２００００的聚乙二醇的结晶性能，并对其低温能量储存功能进行了探讨，结果表明，聚乙二醇是一种性能优良的低温热能储存材料     

Effect of nucleating agent on the crystallization of tailings glass ceramics prepared by one-time sintering

Glass ceramics was made by the one-time sintering method using the main raw material of iron tailings. On the basis of quaternary system of CaO-MgO-Al₂O₃-SiO₂, using DTA, XRD and SEM, the effects of different nucleating agents and mixing amounts as well as heat treatment on the crystallization of tailings glass ceramics were studied. The experimental results show that, nucleating agent and heat treatment are two necessary conditions for one-time sintering preparation of tailings glass ceramics namely, only adding nucleating agent or experiencing heat treatment, the quaternary system can not crystallize. The composite nucleating agent consisting of Cr₂O₃ and TiO₂ can further lead to the crystallization of the CaO-MgO-Al₂O₃-SiO₂ quaternary system at the lower temperature, with the major phase of diopside. In the range of mass content, 0%–4%, crystal intensity and crystal content grow. But when mass content is more than 4%, the crystal size will become coarser and the crystal distribution will be less regular. Different heat treatment regimes do not change the composition of the crystalline major phase in the glass ceramics crystallization of CaO-MgO-Al₂O₃-SiO₂ system. In the range of 30–60 minutes, with the extension of nucleation and crystallization, crystallization degree enhanced, but if the holding time surpasses 60 minutes, the crystallization is worse. Funded by The National Key Technology R & D Program of China for the 11^th Five-Year Plan(2006BAJ04A04)     

成核添加剂对低温相变蓄冷材料过冷度的影响研究

实验研究了成核剂对低温相变材料过冷度的影响.以冷藏工业中常用的-6~-7℃为目标相变温度,NaCl,KCl,NH4Cl三种盐溶液为实验对象.首先查找相图确定了它们在目标相变温度发生相变时的浓度,然后以此浓度为对象,进行了成核剂添加实验.结果表明添加0.02%硅藻土的10%NH4Cl溶液,添加0.1%CuS的12%KCl溶液和添加1%硼砂的12%KCl溶液,以及添加0.02%硅藻土的10%NaCl溶液和添加1%硼砂的10%NaCl溶液可以较好降低过冷度.实验还发现,在连续实验中KCl溶液较易出现环状结冰,环状结冰的相变时间比普通结冰方式要长近一个小时.     

滑石粉对PET结晶及力学性能的影响

采用差示扫描量热仪和万能电子拉伸试验机等研究了滑石粉作为成核剂对聚对苯二甲酸乙二醇酯(PET)结晶性能和力学性能的影响.结果表明,滑石粉可以使PET的各项性能有较大幅度的提高.当滑石粉的添加量为5%(质量分数)时,材料的综合性能最佳,其中半结晶时间缩短47.0%,拉伸强度提高22.2%,弯曲强度提高57.8%,冲击强度提高36.6%.     

TiO2和Cr2O3作晶核剂制取粉煤灰微晶玻璃晶化行为的研究

研究了以TiO2和Cr2O3为晶核剂制取粉煤灰微晶玻璃的晶化行为,运用DTA、XRD、SEM等测试方法,观察了制品中的晶相种类、含量和微晶体发育形貌,分析了基础玻璃的化学组成、热处理方法和晶核剂对晶化行为的影响.研究表明:利用粉煤灰可以生产透辉石为主晶相的微晶玻璃,粉煤灰掺量可达40%以上.晶核剂种类和基础玻璃的化学组成对析晶行为和晶相种类有重要影响,熔制工艺和热处理方法也会影响析晶行为,本研究的玻璃基础组成有利于透辉石晶体的生成.     

聚乙二醇凝胶的制备及其溶胀性能研究

以丙烯酰氯和聚乙二醇（PEG）为原料,合成了聚乙二醇大分子单体,用过硫酸铵为引发剂,N,N亚甲基双丙烯酰胺为交联剂,采用溶液聚合法制备聚乙二醇交联凝胶。探讨了单体分子量、温度、交联剂等因素对PEG凝胶溶胀性能的影响,结果表明：当温度为45℃,单体分子量为20000,交联剂浓度为0.2wt%时,凝胶的溶胀程度最大。此外,差式扫描量热仪（DSC）的结果显示,聚乙二醇在交联网络中不能结晶。     

Effects of Silane Coupling Agent on Microstructure and Mechanical Properties of EPDM/Carbonyl Iron Microwave Absorbing Patch

The effects of types and amounts of silane coupling agent on mechanical properties of vuleanized rubber microwave absorbing patch （VRMAP） were studied. The mechanisms of silane coupling agent＇s effects on mechanical properties of rubber microwave absorbing patch （ RMAP ） and microvave absorbing patch＇s （MAP＇s） mierostrueture were also discussed by using SEM and FT-IR. The experimental results show that the tensile strength of RMAP could be increased through adding the filler of carbonyl iron powder （CIP） modified by silane coupling agent. RMAP fiUed with CIP, which was treated by silane coupling agent KH550, possessed a high tensile strength of 11.5 MPa, which was 448% more than that of MAP whose filler wus not modified by any coupling agent. It was found that the optimal amount of KH550 was 1.0 phr to 100.0 phr carbonyl iron powder. The effects of different modifying techniques on RMAP＇s mechanical properties were also inrestigated. It is indieated that MAP whose filler is modified by the wet process has the highest tensile strength, but it is not the optimal modiifying technique due to complieated wet process. On the contrary, the dry process was very simple, and VRMAP possessed fairly high mechanical properties, therefore, it was the perfect modifying process.     

Influence of nucleating agent on the formation of C4A3S

The reference test methods are carried out parallelly, by means of chemical analysis, X-ray diffraction, differential scanning calorimetry-thermogravimetry, scanning electron microscopy and polarized optical microscope to study the formation of C4A3S in the presence and absence of nucleating agent. The results show that nucleating agent with high calcium and low heat consumption as tricalcium silicate (C3S) promotes the formation of C4A3S and increases desulfurization degree obviously. During calcining raw meals doped with C3S, the grain sizes of C4A3S are larger compared with that without C3S. And at the same calcining level, the mass loss and the heat consumption belonged to CaCO3 decomposition is reduced.     

LLDPE/LDPE共混体系的研究

研究了碱性二氧化钛（ＴｉＯ２）加入低密聚乙烯（ＬＤＰＥ）和线性低密聚乙烯（ＬＬＤＰＥ）的共混体系时共混高聚物性能的变化。采用差示扫描量热法（ＤＳＣ）的测试结果表明：将ＴｉＯ２加入ＬＤＰＥ／ＬＬＤＰＥ的共混体系,共混高聚物结晶时,ＴｉＯ２可作为结晶核影响ＬＬＤＰＥ和ＬＤＰＥ的结晶;ＴｉＯ２的碱性可以与高聚物中酸性的季碳原子作用。两种原因的共同作用使总的结晶潜热降低,而ＬＤＰＥ的结晶较没有加入ＴｉＯ２又更完善。