聚苯硫醚/纳米二氧化硅复合材料的非等温结晶动力学及动态力学性能

用DSC法研究了聚苯硫醚（PPS）及其纳米SiO2复合材料的非等温结晶动力学,分析了结晶峰值温度Tp以及结晶起始温度T0等参数,并采用莫志深方程研究了复合材料的非等温结晶动力学。结果表明,莫志深方程能够较好地描述复合材料的非等温结晶动力学,纳米SiO2在PPS基体中起异相成核作用,而使得纳米复合材料的结晶速率明显快于纯聚合物的结晶速率。动态力学分析研究结果表明,纳米SiO2的加入提高了PPS的储能模量,Tg向高温方向移动,说明纳米SiO2与PPS之间存在着较强的相互作用。     

表面复合纳米SiO_2和碳纳米管玻璃纤维增强尼龙6的结构与性能

利用静电相互作用在玻璃纤维(GF)表面分别复合纳米二氧化硅(SiO2)和多壁碳纳米管(MWNTs),制备了GF-SiO2、GF-MWNTs复合增强体,并通过转矩流变仪制备了尼龙6(PA6)/GF-SiO2和尼龙6(PA6)/GF-MWNTs复合材料.利用扫描电子显微镜(SEM),示差扫描量热仪(DSC),热机械分析仪(DMA)等手段研究了复合材料的微观结构、热学及力学性能.结果表明,静电复合的方法可以使纳米二氧化硅(nano-SiO2)、多壁碳纳米管(MWNTs)在GF表面达到均匀吸附,复合增强体能加快尼龙6的结晶速度,并使材料的玻璃化温度、动态模量、拉伸强度、结晶温度等明显提高,其中GF-MWNTs对复合材料性能的提高最明显,拉伸强度提升了21%,模量提高了28%.     

纳米SiO2对火焰喷涂聚酰胺12涂层非等温结晶与熔融行为的影响

采用火焰喷涂法制备了聚酰胺12/纳米SiO2(PA12/nano-SiO2)复合涂层,利用差示扫描量热法(DSC)对复合涂层的非等温结晶过程、熔融行为进行了分析.结果表明:纳米SiO2粒子的加入不仅能提高复合涂层的结晶度和结晶温度,而且使复合涂层的熔融峰温度高于纯PA12涂层,说明纳米SiO2粒子具有明显的成核剂作用,它能诱导聚酰胺大分子结晶,提高其结晶能力、结晶速率、结晶的完善程度及结晶度,并能改善涂层的力学、耐老化及耐摩擦磨损性能.     

聚乳酸/氧化锌柱撑皂石纳米复合材料制备与性能及结构表征

通过微波水解法制备了ZnO柱撑皂石,并以其为加工助剂制备了聚乳酸(PLA)/ZnO柱撑皂石纳米复合材料.通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、对ZnO柱撑皂石及PLA/ZnO柱撑皂石纳米复合材料的结构进行了表征,并对其力学性能和热稳定性能进行了测试.微观结构分析表明,ZnO柱撑皂石呈现剥离状,并均匀分散在PLA基质中.力学性能研究表明0.3%ZnO柱撑皂石的加入有助于改善PLA复合材料的断裂伸长率.SEM分析表明PLA复合材料的断面发生明显改变,表现良好韧性;DSC结果显示纳米ZnO柱撑皂石可以降低复合材料的玻璃化转变温度、结晶温度,有助于提高PLA复合材料的结晶度,与XRD分析相吻合;热重分析表明ZnO柱撑皂石可以提高PLA复合材料的热稳定性.测试结果表明,ZnO柱撑皂石在PLA基质中起到了异相成核的作用,促进了PLA基质的结晶.     

尼龙6/SiO_2纳米复合材料的制备及其力学性能和热稳定性

以表面含有氨基的可反应性纳米SiO2(RNS-A)和表面含有烷基碳链的可分散性纳米SiO2(DNS-3)作为填料,利用原位聚合法制备了尼龙6/SiO2纳米复合材料(相应的复合材料分别简记为RPA和DP3);采用透射电子显微镜观察了复合材料中纳米SiO2的表面形貌,并利用热失重分析仪测定了复合材料的热稳定性,进而考察了纳米SiO2表面功能基团对尼龙6力学性能和热稳定性的影响.结果显示,纳米SiO2能够很好地分散在尼龙6基体中,并使尼龙6的热分解温度提高10℃左右.与此同时,RPA的最大拉伸强度和冲击强度较纯尼龙6的分别提高34.5%和12.5%,DP3的最大拉伸强度和冲击强度分别提高18.2%和45.7%.这表明两种纳米SiO2均可以有效地提高尼龙6的力学性能和热稳定性;可以推测,纳米SiO2的增强效应与其在尼龙6基体材料中的分散和界面作用有关.     

静电纺丝制备SiO2短纤维对聚丙烯冲击性能的影响

采用静电纺丝技术, 结合正硅酸乙酯(TEOS)的溶胶-凝胶反应制备出了直径为500 nm的SiO2短纤维(n-SF). 纤维经过硅烷偶联剂KH570表面处理后, 与聚丙烯(PP)通过螺杆混合制得复合材料. 通过SEM观察, KH570处理过的SiO2短纤维(n-MSF)在PP基体中分散均匀, 界面结合良好. DSC和XRD测试结果表明, n-SF和n-MSF的加入均可提高PP的结晶速率, 同时改变PP中β晶含量, 进而影响冲击强度; 冲击实验结果表明, n-MSF添加量为3%(质量分数)时, 复合材料冲击性能比纯PP提高了40.3%.     

聚丁二酸丁二酯/纳米高岭土共混体系结晶及力学性能研究

用熔融共混法制备聚丁二酸丁二酯(PBS)/纳米高岭土(nano kaolin)复合降解材料,利用FTIR、DSC、万能拉力机和SEM对其微观结构、结晶、力学性能及分散性进行研究.FTIR光谱分析结果表明,改性剂与nano kaolin发生了化学键合作用;DSC结果表明,在PBS中加入nano kaolin,提高了结晶起...     

聚氨酯弹性体/蒙脱土纳米复合材料的合成与性能

采用聚氨酯本体预聚法 ,利用原位插层聚合合成了聚氨酯 蒙脱土纳米复合材料 .通过X 射线衍射(XRD)和Molau实验研究了蒙脱土在复合材料中的分散情况 .红外分析 (IR)表明随着蒙脱土含量的增加 ,复合材料羰基氢键减少 .动态力学分析 (DMA)以及差热分析 (DSC)结果说明随着蒙脱土含量的增加 ,材料的玻璃化温度降低 .聚氨酯纳米复合材料的拉伸强度和断裂伸长率同时提高 ,表现出较好的力学性能 .     

LLDPE/纳米SiO_2复合材料的力学性能和光学性能研究

采用熔融共混方法制备了LLDPE 纳米SiO2 复合材料 ,并对该体系的力学性能和光学性能进行了系统研究 .结果表明 ,随着纳米SiO2 的加入 ,复合材料的弹性模量显著提高 ,冲击强度与拉伸强度呈峰形变化 ,且均在SiO2 含量为 3phr左右达到最大值 .加入少量的纳米SiO2 后 ,复合材料薄膜对长波红外线 (7～ 1 1 μm)的吸收能力较LLDPE膜有了显著提高 ,透光率略有下降但雾度提高 ,透光质量得到改善 .同时表明 ,纳米SiO2 的表面处理方法对膜的光学性能有显著影响     

C(膜)/Si(SiO2 )(纳米微粒)/C(膜)热处理的形态及结构分析

用直流辉光溅射+真空镀膜法制备了一种新型结构的硅基纳米发光材料- C(膜)/Si(SiO2)(纳米微粒)/C(膜)夹层膜,并对其进行了退火处理.用TEM、 SEM、 XRD和XPS对其进行了形态结构分析.TEM观察表明: Si(SiO2)纳米微粒基本呈球形,粒径在30 nm左右.SEM观察表明: 夹层膜样品总厚度约为50 μm,膜表面比较平整、致密.400℃退火后,样品表面变得凹凸不平,出现孔状结构; 650℃退火后,样品表面最平整、致密且颗粒均匀.XRD分析表明:制备出的夹层膜主要由SiO2和Si组成,在C原子的还原作用和氧气的氧化作用的共同作用下, SiO2和Si的含量随加热温度的升高而呈现交替变化: 400℃时, C的还原作用占主导地位, SiO2几乎全部被还原成了Si,此时Si含量最高; 400～650℃时,氧化作用占主导地位, Si又被氧化成SiO2, Si含量降低, SiO2含量逐渐上升,在650℃达到最高.XPS分析表明: 在加热过程中, C原子逐渐扩散进入Si(SiO2)微粒层,在650℃与Si反应生成了新的SiC.     

Effect of Carboxylic Acid Nucleating Agent on Crystallization and Mechanical Properties of PLA/PBS Blends

Poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends were prepared using a carboxylic acid salt as nucleating agent (NA). The effect of NA on the crystallization kinetics of PLA and PLA/PBS blend was investigated using a differential scanning calorimeter, a polarized optical microscope and a wideangle X-ray diffractometer. The crystallization rate of PLA component in PLA/PBS blends is increased effectively by NA through fast nucleation and growth rate of PLA α'-form crystal, which is confirmed by isothermal crystallization behavior of PLA/PBA/NA composites. The isothermal crystallization results also show that the incorporation of NA induces heterogeneous nucleation mechanism in PLA component. The increased number of crystal nuclei hinders the increase of average grain size of PLA component in composites but contributes to a higher crystallinity of both PLA and PBS components in PLA/PBS blends. Finally, the mechanical properties and dynamic mechanical properties of PLA/PBS/NA composites are improved because of the increased crystallinity, which are superior to that of PLA/PBS blend.     

尼龙66/SiO_2纳米微粒复合材料的结晶行为

采用双螺杆熔融共混法制备了尼龙66/S iO2纳米微粒复合材料,用X射线衍射法和示差扫描量热法比较了干态和湿态两种制备条件下复合材料的结晶行为;并用修正的Avram i方程的Jeziorny法研究了纳米复合材料的非等温结晶动力学行为.     

MISCIBILITY, CRYSTALLIZATION AND MECHANICAL PROPERTIES OF PPC/PBS BLENDS

In this paper,melt blends of poly(propylene carbonate)(PPC)with poly(butylene succinate)(PBS)were characterized by dynamic mechanical analysis(DMA),differential scanning calorimetry(DSC),tensile testing,wide-angle X-ray diffraction(WAXD),polarized optical microscopy and thermogravimetric analysis(TGA).The results indicated that the glass transition temperature of PPC in the 90/10 PPC/PBS blend was decreased by about 11K comparing with that of pure PPC.The presence of 10% PBS was partially miscible with PPC.The 90/10 PPC/PBS blend had better impact ==========and tensile strength than those of the other PPC/PBS blends.The glass transition temperature of PPC in the 80/20,70/30,and 60/40 PPC/PBS blends was improved by about 4.9 K,4.2 K,and 13 K comparing with that of pure PPC,respectively;which indicated the immiscibility between PPC and PBS.The DSC results indicated that the crystallization of PBS became more difficult when the PPC content increased.The matrix of PPC hindered the crystallization process of PBS.While the content of PBS was above 20%,significant crystallization-induced phase separation was observed by polarized optical microscopy. It was found from the WAXD analysis that the crystal structure of PBS did not change,and the degree of crystallinity increased with increasing PBS content in the PPC/PBS blends.     

Preparation and physicochemical properties of hydroxyapatite/polyurethane nanocomposites

In this study, nanohydroxyapatite/polyurethane （nHA/PU） composites with various contents of methoxy- poly（ethylene glycol） modified nHA （0 wt%, 10 wt%, 20 wt% and 30 wt%） were prepared by solution blending process. The physicochemical properties of the composite membranes were investigated by Fourier transform infrared spectroscopy （FTIR）, X-ray diffraction （XRD）, Transmission electronic microscopy （TEM）, Differential scanning calorimetry （DSC）, Thermo gravimetric analysis （TGA） and tensile tests. TEM photos of the nanocomposites showed that the nHA was uniformly dispersed in the polymer matrix. The membrane with 10 wt% nHA showed the highest tensile strength which was about 75% higher than that of the pure PU membrane. However, the tensile strength decreased when high content （above 20 wt%） fillers were added, which was still higher than that of pure PU. TGA measurements suggested that the thermal stability of the membranes was improved owing to nHA fillers. XRD and DSC results illustrated that the crystallinity of PU soft segments decreased with the increasing content of nanoparticles in the composites.     

Thermal properties of microcrystalline cellulose-filled PET–PTT blend polymer composites

Polymer composite materials were prepared from poly(ethylene terephthalate)–poly(trimethylene terephthalate) blends as the matrix and different microcrystalline cellulose (MCC) filler levels (0–40 wt%) using melt compounding followed by compression molding. The composites were analyzed using dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The DSC results indicated that there is no consistent or significant influence of the MCC addition on the glass transition (T _g), melting (T _m), and crystallization temperature of the composites. With increasing MCC content, dynamic mechanical properties improved because of the reinforcing effect of the MCC. The tan δ peak values from the DMTA were not significantly changed as the MCC content increased. TG indicated that the onset temperature of rapid thermal degradation decreased with increasing MCC content. It was also found that the thermal stability of the composites slightly decreased as the MCC content increased.     

Confinement effect of SiO2 framework on phase change of PEG in shape-stabilized PEG/SiO2 composites

PEG/SiO₂ shape-stabilized phase change materials with various mass fractions and molecular weights of PEG were prepared by the sol–gel method. Polyethylene glycol (PEG) and tetraethyl orthosilicate (TEOS) were chosen as the phase change substance and the silica framework precursor, respectively. The as-prepared samples were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) techniques. It is shown that the silica framework strongly confined the crystallization of PEG. The crystallinity and thermodynamic performance of the composites were undesirable for PEG with molecular weight of 1500 even when the PEG content reached 80 wt%. The crystallinity and thermodynamic performances of the PEG/SiO₂ composites first decline then improve with the increase of the PEG molecular weights, owing to the different confinement behaviors of the silica framework. Finally, we investigated the phase change mechanism of the PEG/SiO₂ composites under the different confinement of the silica framework.     

聚丁二酸丁二醇酯的自成核结晶行为

利用差示扫描量热仪(DSC)研究了自成核对聚丁二酸丁二醇酯(PBS)的结晶行为的影响. 研究结果表明, PBS的有效自成核温度处理区间为118～120 ℃. PBS经自成核处理后结晶温度提高, 可以在100~118 ℃温度区间内迅速结晶. 同时, 研究了自成核处理后样品在100～104 ℃范围内的等温结晶行为、动力学过程及熔融行为. 结果表明, 随着等温结晶温度的升高, 结晶速率变慢, 熔融曲线出现多重熔融峰. Hoffman-Weeks方程分析结果表明, 自成核处理对PBS的平衡熔点没有影响. Avrami等温结晶动力学方程适合分析自成核处理样品的等温结晶动力学过程, 获得其动力学参数K与n, 其中n值偏大的原因在于自成核的样品结晶生长点增多. 根据Arrhenius方程, 计算获得PBS自成核处理后等温结晶活化能为-286 kJ/mol.     

Nonisothermal crystallization and morphology of poly(butylene succinate)/layered double hydroxide nanocomposites

Biodegradable poly(butylene succinate) (PBS) and layered double hydroxide (LDH) nanocomposites were prepared via melt blending in a twin-screw extruder. The morphology and dispersion of LDH nanoparticles within PBS matrix were characterized by transmission electron microscopy (TEM), which showed that LDH nanoparticles were found to be well distributed at the nanometer level. The nonisothermal crystallization behavior of nanocomposites was extensively studied using differential scanning calorimetry (DSC) technique at various cooling rates. The crystallization rate of PBS was accelerated by the addition of LDH due to its heterogeneous nucleation effect; however, the crystallization mechanism and crystal structure of PBS remained almost unchanged. In kinetics analysis of nonisothermal crystallization, the Ozawa approach failed to describe the crystallization behavior of PBS/LDH nanocomposites, whereas both the modified Avrami model and the Mo method well represented the crystallization behavior of nanocomposites. The effective activation energy was estimated as a function of the relative degree of crystallinity using the isoconversional analysis. The subsequent melting behavior of PBS and PBS/LDH nanocomposites was observed to be dependent on the cooling rate. The POM showed that the small and less perfect crystals were formed in nanocomposites.