蒽系列成核剂对聚丙烯性能的影响

利用蒽为基础原料,自制了蒽系列的三种聚丙烯成核剂:9,10-二氢蒽-9,10-桥-α,β-马来酸酐（AMH）、9,10-二氢蒽-9,10-桥-α,β-马来酰肼（AMHD）、9,10-二氢蒽-9,10-桥-α,β-N-甘氨酸基马来酰胺（AGMA）。利用热重分析（TGA）分别考察了三者的热稳定性,采用X 射线衍射分析( XRD) 和偏光显微镜( PLM) 对其所改性等规聚丙烯（iPP）的结晶形态进行了表征,用差示扫描量热法( DSC) 研究了其结晶行为,并测试了力学性能。结果表明,AMHD和AGMA均可增强聚丙烯α晶型成核,而AMH则可诱导β-iPP的生成;该三种成核剂都有效提高了聚丙烯的结晶温度（Tc）和结晶度,其中iPP/AMHD的结晶度（Xc）提高了3.75%;同时改善了iPP的力学性能,与纯iPP试样相比,iPP/AMH抗冲击强度提高了5.60 kJ/m2,iPP/AMHD拉伸强度提高了18.02%,iPP/AGMA的弯曲强度达到53.22 MPa。     

β成核剂改性iPP的熔融结晶行为与力学性能研究

采用3种β成核剂(NT-A,NT-B和NT-C)制备了β晶等规聚丙烯(β-iPP)样品,应用差示扫描量热仪(DSC)分析、偏光显微镜(POM)观察和力学性能测试研究了β-iPP的熔融、结晶行为和力学性能。结果表明:加入β成核剂后,诱导iPP由α晶向β晶转变,结晶温度提高,球晶明显细化。3种β成核剂的成核效率和改性样品的缺口冲击强度顺序为NT-C>NT-B>NT-A,添加NT-C质量分数0.050%时,样品的最大缺口冲击强度可达纯iPP的3.7倍。     

新型α-成核剂的制备及其对聚丙烯性能的影响

利用蒽、马来酸酐和水合肼为原料,制备了一种新型聚丙烯（PP）α-晶型成核剂（AMHD）。利用热重分析考察了该成核剂的热稳定性,采用X射线衍射分析、偏光显微镜和差示扫描量热法对该成核剂对等规聚丙烯（iPP）的结晶形态和结晶行为的影响进行了研究,并测试了其力学性能和维卡软化点。结果表明,成核剂AMHD有效提高了iPP的结晶温度（Tc）和结晶度（Xc）,其中Xc提高至50 ％;同时改善了iPP的力学性能和耐热性能,与纯iPP试样相比,iPP/AMHD的简支梁缺口冲击强度、拉伸强度和弯曲强度分别提高了1.27倍、18.02 ％和10.76％。     

β成核剂对抗冲聚丙烯共聚物的结晶和力学性能研究

分别用α晶型成核剂和β晶型成核剂对抗冲聚丙烯共聚物（iPP）的结晶和力学性能进行研究,并用偏光显微镜（POM）、广角X射线衍射仪（WAXD）和差示扫描量热仪（DSC）对其进行了详细的表征。结果表明,α和β成核剂使iPP的起始结晶温度（ton）提高15.3℃和12.7℃,结晶峰温度（tp）提高17℃和13.7℃,结晶速率加快。两种成核剂都能使球晶细化,使结晶更加均匀化、规整化,从而使结晶度增加。α成核剂（TMA-3）使iPP的拉伸强度、冲击强度和断裂伸长率分别提高到23.43MPa、22.27kJ/m2和788%;β成核剂因主要是改变球晶的形态,形成与α球晶完全不同的β晶型,使iPP的拉伸强度、冲击强度和断裂伸长率的提高比α成核剂显著,分别达到24MPa、32.81kJ/m2和861%。     

酰胺类β晶型成核剂对PP结晶性影响

研究了新型酰胺类β成核剂对聚丙烯（PP）结晶性能的影响。用差示扫描量热计（DSC）和X射线衍射仪（XRD）对其结晶形态进行了表征，DSC研究表明，该成核剂的加入可以诱导PP中α晶向口晶转变；X射线衍射研究发现，当成核剂加入质量分数为0．3％时，β晶型的相对含量可达到87%，与DSC的研究结果一致。考察了冷却速率对结晶温度和结晶峰温度的影响，结果表明该成核剂的加入使PP结晶向高温方向偏移，结晶速度加快。     

一种新型聚丙烯成核剂的合成及表征

以邻苯二甲酸和异丙醇铝为原料,合成了新型的邻苯二甲酸羟基铝盐类聚丙烯成核剂(OXA)。利用热重分析、X射线衍射仪、差示扫描量热仪和偏光显微镜分别考察了成核剂的热稳定性及其对等规聚丙烯（iPP）的晶型、结晶行为和结晶形态的影响,同时,还考查了成核剂对iPP力学性能的影响。结果表明,OXA是一种有效的聚丙烯α晶型成核剂,当添加量为0.3 %（质量分数,下同）时,iPP的结晶温度可提高13.26 ℃,结晶度由纯iPP的52.49 %提高到58.37 %,同时可显著细化iPP球晶;也明显提高了iPP的拉伸和弯曲强度,拉伸强度由36.18 MPa提高为43.41 MPa,弯曲强度由46.19 MPa提高至50.89 MPa。     

蒽系列成核剂的合成及对聚丙烯性能的影响

利用蒽为基础原料,自制了蒽系列的3种聚丙烯成核剂:9,10-二氢蒽-9,10-桥-α,β-马来酸酐(AMH)、9,10-二氢蒽-9,10-桥-α,β-马来酰肼(AMHD)、9,10-二氢蒽-9,10-桥-α,β-N-甘氨酸基马来酰胺(AGMA)。利用热重分析(TGA)分别考察了三者的热稳定性,采用X射线衍射分析(XRD)和偏光显微镜(PLM)对其所改性等规聚丙烯(iPP)的结晶形态进行了表征,用差示扫描量热法(DSC)研究了其结晶行为,并测试了其力学性能。结果表明,AMHD和AGMA均可增强聚丙烯α晶型成核,而AMH则可诱导β-iPP的生成;3种成核剂都有效提高了聚丙烯的结晶温度(Tc)和结晶度,其中,iPP/AMHD的结晶度(Xc)提高了3.75%;同时改善了iPP的力学性能,与纯iPP试样相比,iPP/AMH抗冲击强度提高了5.60 kJ/m2,iPP/AMHD拉伸强度提高了18.02%,iPP/AGMA的弯曲强度达到53.22 MPa。     

α成核剂和β成核剂对高流动性聚丙烯结晶行为的影响

研究了α成核剂和β成核剂对高流动性聚丙烯(PP)结晶行为的影响,采用偏光显微镜、差示扫描量热法和广角X衍射对其微观结构和结晶形态进行了表征。结果表明:α成核剂的加入细化球晶而不改变结晶形态;β成核剂的加入改变球晶的形态,使部分α晶型向β晶型转变;两种成核剂的加入使高流动性PP的结晶速率加快结、晶过程的成核方式和生长机理发生改变,结晶活化能降低。     

增压对聚丙烯/多壁碳纳米管复合材料结晶行为的影响

利用广角X射线衍射仪和差示扫描热仪研究了不同增压速率、不同增压温度下等规聚丙烯/多壁碳纳米管（iPP/MWCNTs）复合材料的结晶行为。结果表明，慢速增压条件下（1 MPa/s），增压温度较低时有利于α-iPP的生成，增压温度越高越有利于γ-iPP的生成，且慢速增压条件下MWCNTs对iPP的结晶具有诱导作用，制备的γ-iPP较稳定，在升温过程中不会发生熔融重结晶现象；快速增压条件下（200 MPa/s），较低的增压温度就能够制备出纯的γ-iPP，但MWCNTs的存在使iPP的熔体黏度增大，阻碍分子链运动，不利于晶体生长，形成的γ晶结构完善性较差，在升温过程中会发生熔融重结晶，增压温度较高时，快速增压能够制备出亚稳态中间相iPP。对比发现，增压速率和熔体记忆效应的协同作用共同决定了复合材料中iPP的结晶结构，慢速增压条件下熔体记忆效应对iPP的结晶结构影响较大，增压速率升高后，熔体记忆效应对其结晶行为的影响减弱。     

熔体挤出-拉伸iPP薄膜的结晶行为和性能

通过挤出-拉伸法分别制备了iPP和β成核剂改性iPP薄膜,研究了β成核剂和拉伸速率对薄膜结晶行为和力学性能的影响。采用二维广角X射线衍射、二维小角X射线散射、差示扫描量热法、扫描电镜(SEM)和拉伸试验对薄膜微观结构和力学性能进行了相关分析测试。结果表明:β成核剂的加入使得iPP薄膜中的晶型发生改变;当β成核剂质量分数为0.2%且拉伸速率为30cm/min时,薄膜内部β晶发生明显支化现象,并且在其内部至少形成了三种不同形貌的β晶;试样的断裂伸长率和韧性均增大;随着拉伸速率的增加,试样中β晶含量减小。     

Atomic force microscopy study of the lamellar growth of isotactic polypropylene

The growth behaviors of cross-hatched and lath-like lamellae of α-form spherulites and flat-on lamellae of β-form pherulites of isotactic polypropylene were studied with a high-temperature atomic force microscopy in situ and in real time. The growth rates of crystal lamellae in types I, II and mixed α-form spherulites and in β-form spherulites, as well as the spatial frequency of tangential branching, were measured. The frequency of tangential branching increases with decreasing crystallization temperature, while the growth rates of leading radial and tangential lamellae are approximately the same at a given temperature. Observations of as-crystallized materials demonstrated that the spacing and length of transverse lamellae is sufficient to differentiate among spherulite types. Height measurements in the melt near the growth surface indicate roles of molecular transport in the crystallization process.     

乙烯含量对无规共聚聚丙烯晶型及性能影响的研究

通过差示扫描量热分析、X射线衍射分析以及力学性能测试等方法,研究了不同乙烯含量的无规共聚聚丙烯（PPR）体系中,在添加定量β成核剂的条件下,乙烯含量对PPR结晶行为及热学、力学性能的影响。结果表明,PPR的熔点和结晶温度都随其乙烯含量的减少而升高;乙烯含量较少的体系,有利于β晶的形成;体系中β晶含量的提高,会使样品热变形温度提高,且冲击性能显著增强;乙烯含量的提高,增大了PPR β结晶的调控难度;实验室自制β成核剂,可使乙烯含量为0.25 %~5.1 %（质量分数,下同）的PPR中的β晶含量达到80 %以上。     

Effects of crystallization temperature on the polymorphic behavior of syndiotactic polystyrene

The influence of crystallization temperature on formation of the α- and β-form crystals of syndiotactic polystyrene (sPS) was investigated by X-ray diffraction and non-isothermal differential scanning calorimetry analysis. For sPS samples without any thermal history, the crystallization temperature must be the intrinsic factor controlling the formation the α and β-form crystals. Being crystallized at different cooling rate from the melt, sPS forms the β-form crystal until the temperature cooled down to about 230 °C, and α-form crystal can only be obtained when the temperature was below about 230 °C.     

Melting and crystallization behavior of poly(trimethylene 2,6-naphthalate)

The melting and crystallization behavior of poly(trimethylene 2,6-naphthalate) (PTN) are investigated by using the conventional DSC, the temperature-modulated DSC (TMDSC), wide angle X-ray diffraction (WAXD) and polarized light microscopy. It is observed that PTN has two polymorphs (α- and β-form) depending upon the crystallization temperature. The α-form crystals develop at the crystallization temperature below 140 °C while β-form crystals develop above 160 °C. Both α- and β-form crystals coexist in the samples crystallized isothermally at the temperature between 140 and 160 °C. When complex multiple melting peaks of PTN are analyzed using the conventional DSC, TMDSC and WAXD, it is found that those arise from the combined mechanism of the existence of different crystal structures, the dual lamellar population, and melting-recrystallization-remelting. The equilibrium melting temperatures of PTN α- and β-form crystals determined by the Hoffman-Weeks method are 197 and 223 °C, respectively. When the spherulitic growth kinetics is analyzed using the Lauritzen-Hoffmann theory of secondary crystallization, the transition temperature of melt crystallization between regime II and III for the β-form crystals is observed at 178 °C. Another transition is observed at 154 °C, where the crystal transformation from α- to β-form occurs.     

相对分子质量对β晶型等规聚丙烯性能的影响

利用熔体流动速率来反映等规聚丙烯(IPP)的相对分子质量,在添加自制β成核剂的条件下通过力学性能测试、差示扫描量热仪以及X射线衍射仪研究了相对分子质量对β晶型等规聚丙烯(β-PP)热行为、晶型组成和力学性能的影响。结果表明,加入β晶型成核剂后,IPP结晶温度、热变形温度均增加10℃左右,β晶型相对含量增加至60%～70%;相对分子质量较高的β-PP冲击强度提高一倍以上,相对分子质量较低的β-PP冲击性能改善有限;β-PP的弯曲模量和弯曲强度均下降,相对分子质量越低降低幅度越大。     

Thermal analysis, X-ray and electron diffraction studies on crystalline phase transitions in solvent-treated poly(hexamethylene terephthalate)

The crystal polymorphism, transformation, and morphologies in chloroform solvent-cast poly(hexamethylene terephthalate) (PHT) were examined by using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and temperature in situ transmission electron microscopy (TEM). Solvent-induced crystallization of PHT at room temperature yielded an initial crystal of γ-form, as confirmed by WAXD. Upon DSC scanning, the original γ-form in PHT exhibited three endothermic peaks, whose origins and association were carefully analyzed. The first peak, much smaller than the other two, is in the temperature range of ca. 100-120 °C. It was found that the solvent-induced γ-form was transformed to β-form at 125 °C via a solid-to-solid transformation mechanism. In addition, WAXD showed that γ- and β-forms co-existed in the temperature range of 100-125 °C. These mixed crystal forms were further identified using TEM, and the selected-area electron diffraction (ED) patterns revealed that both γ- and β-form crystals co-existed and were packed within the same spherulite. Solid-solid transformation from the solvent-induced γ-form to β-form in PHT upon heat scanning was presented with evidence and discussed.     

Real time in situ X-ray diffraction studies on the melting memory effect in the crystallization of β-isotactic polypropylene

The melting memory effect during the crystallization and heating of semi-crystalline polymers was clearly demonstrated using β-isotactic polypropylene (β-iPP). Differential scanning calorimetry and real-time in situ X-ray diffraction using a synchrotron radiation source were employed to investigate the role of the newly formed α-form crystals via phase transformation from the metastable β-form during the melting process, and to elucidate the memory effect of these new α-form crystals during the crystallization process. The evolution of the memory effect in β-iPP during the crystallization and melting processes is ideally based on the existence of locally ordered α-form in the melt. We monitored the role of this local order by preparing the melt state using a range of hold temperatures and hold times. It was found that the final melt temperature and hold time greatly affect the crystallization behavior during cooling and the phase transformation behavior during heating. Lower hold temperatures and shorter hold times lead to samples rich in α-modification, whereas longer hold times generate samples rich in β-modification during crystallization. At higher hold temperatures even a short hold time is sufficient to destroy the local order in the melt, and the resulting sample exhibits more β-modification. The results are explained on the basis of the existence of local order in the amorphous melt along with external nucleating agent during the crystallization process.     

The crystallization characterization of bulk syndiotactic polystyrene sample: immediate evidence from IR spectroscopy

The crystallization characterization of bulk syndiothactic polystyrene (s-PS) sample is thoroughly studied using the Fourier transform infrared spectroscopy (FTIR). The WAXD is further used to identify the s-PS crystal formation to confirm the specific absorbance in FTIR spectra. Both melt and cold-crystallization behavior are quantitatively determined using FTIR spectra ranging from 870 to 820 cm⁻¹ at 264 °C. Fitting curves to IR spectra provides direct evidence of bulk s-PS crystallization behavior in quantification. The melt-crystallization process yields the β-form only; while the cold-crystallization process yields both the α and the β-form crystal in bulk s-PS sample. The β-form crystal is generated from the phase-transformation of the α-form crystal by cold-crystallization process, the α-form crystal is the initial phase. The activity energy of the α-form formation is lower that that of the β-form, suggesting that the α-form crystal is kinetically favorable while the β-form crystal is thermodynamically favorable.     

Structure, morphology and non-isothermal crystallization behavior of polypropylene catalloys

The structure, morphology and non-isothermal crystallization behavior of polypropylene catalloys (PP-cats) as well as pure polypropylene were investigated via differential scanning calorimeter (DSC), wide angle X-ray diffraction (WAXD) and real-time hot-stage optical microscopy (OM). The results reveal that the crystalline structures of PP-cats change with variations of the crystallization conditions and composition. The crystalline phase might consist of α-PP, β-PP and PE crystals. The content of β-PP increases with the increase of EP copolymer content and the cooling rate. At lower cooling rates, the morphologies of all non-isothermal crystallized PP-cats show spherulitic structure, and the decrease of crystal perfection and the increase of nucleation density of PP-cats system could be evidently observed. Considering the compositions of PP-cats, these indicated that the interactions between propylene homopolymer and the ethylene-propylene copolymers (both random and block ones) are in favor of the enhancement of the nucleation ability of α-form as well as β-form. In comparison with pure PP, the overall crystallization rates of the PP-cats increase dramatically, while the growth rates of the spherulites in all PP-cats decrease distinctly under the given cooling conditions. These experimental results were explained on the basis of diluting effect and obstructing effect on the mobility of PP chains in the ethylene-propylene copolymer.     

β晶相聚丙烯纺丝工艺的研究

本文研究了三种不同β晶成核剂的聚丙烯切片的纺丝工艺条件与初生纤维中结晶结构的关系。研究表明,制得的初生纤维中的β晶含量主要取决于含β成核剂聚丙烯的结晶速率和纺丝成形中的冷却速率。含β成核剂E3B聚丙烯的结晶速率最大,纺制的初生纤维β晶含量最高;纺丝成形中的冷却速率愈高,初生纤维中的β晶含量愈低;在一定的温度范围内,纺丝温度对初生纤维中β晶相对含量影响甚微;纺丝冷却条件和纤维束的集束状况对β晶含量有明显的影响;β晶的晶粒尺寸与β晶含量相对应,而初生纤维中的结晶度多在55％左右,受纺丝工艺参数的影响甚小。