β-成核剂对废旧聚丙烯/无机填料复合材料的 结晶性能影响研究

随着聚丙烯(PP)在包装领域的广泛使用,废旧聚丙烯(RPP)的产生量逐年递增。使用取代芳酰胺型β-成核剂(TMB-5)成核RPP/无机填料复合材料,采用差示扫描量热法(DSC)和广角X射线衍射法(WAXD)对比研究TMB-5对不同RPP/无机填料复合材料结晶行为和熔融特性的影响。研究结果表明:实验选用的工业级无机填料并未明显影响RPP的结晶行为和结晶晶型,而TMB-5不仅显著提高了RPP/无机填料复合材料的结晶温度,而且诱导形成大量β-晶。通过制备高β-晶含量的RPP/无机填料复合材料,能够实现无机填料增强和β-晶增韧作用的协同化,最终获得力学性能达到PP新料水平的填充RPP复合材料。     

庚二酸处理硅灰石填充改性聚丙烯

采用庚二酸对硅灰石进行表面处理,研究了复合材料的力学和结晶性能。DSC和WAXD结果表明,庚二酸处理的比未处理硅灰石有更强的诱发聚丙烯β晶的能力。偏光显微镜观察表明,庚二酸处理硅灰石大大减小了β晶的粒径,改善了硅灰石与聚丙烯的相容性。     

增容剂和稀土β成核剂对聚丙烯/硫酸钙晶须复合材料的影响

研究了增容剂聚丙烯接枝马来酸酐(PP-g-MAH)和稀土β成核剂对聚丙烯/硫酸钙晶须复合材料的结晶行为、熔融行为和力学性能的影响。实验结果表明,硫酸钙晶须具有一定的诱导β-晶型的异相成核作用,使聚丙烯结晶温度提高和结晶速率增加。PP-g-MAH提高了结晶温度和晶须的成核能力,降低了β-晶型的含量,不利于β-晶型的生成,并改善了树脂与晶须的界面性能,提高了拉伸强度和冲击性能。稀土β成核剂具有很强的诱导形成β-晶型的异相成核效应,有效地提高了复合材料的冲击性能。     

聚丙烯/镁盐晶须复合材料的形态结构与性能研究

采用哈克单螺杆挤出机制备了聚丙烯/镁盐晶须复合材料,着重研究了增容剂聚丙烯接枝马来酸酐(PP-g-MAH)对复合材料的晶体结构与球晶形态、结晶和熔融行为、热稳定性以及力学性能的影响。研究表明镁盐晶须具有明显的诱导β-晶型的异相成核作用,使聚丙烯结晶温度大幅度提高,球晶尺寸细化。增容剂的加入改善了树脂与晶须的界面性能,界面粘结作用明显增强,提高了拉伸强度和冲击性能,并进一步提高了结晶温度和晶须的成核能力,但降低了β-晶型的含量,不利于β-晶型的生成。     

N,N′-二苯基丁二酰胺诱导生成β晶型等规聚丙烯

研究了酰胺化合物——N,N′-二苯基丁二酰胺(DPS)的用量和结晶温度对聚丙烯中β晶型含量和结晶度的影响。发现DPS是聚丙烯的高效β成核剂,随着DPS含量的增加,聚丙烯中β晶型含量不断增多。等温结晶试验表明,添加0.2%DPS的聚丙烯样品在结晶温度为120℃时生成最大含量β晶型,此时β晶型的相对含量达到89.06%。     

庚二酸／硬脂酸钙双组分成核剂对β晶型等规聚丙烯生成的影响

研究了在120 ℃等温结晶30 min的条件下,庚二酸/硬脂酸钙组成比对等规聚丙烯中β晶型含量的影响,发现在0.15%(质量分数)庚二酸用量下,随着硬脂酸钙用量的增加,β晶型含量不断增大,硬脂酸钙用量在0.35%(质量分数)以上时,才能生成较高纯度的β晶型聚丙烯,说明iPP和双组分成核剂熔体混合时,庚二酸和硬脂酸钙可能"就地"发生化学反应,生成高效β晶型成核剂--庚二酸钙.还研究了在0.15%庚二酸/0.5%硬脂酸钙固定组成比下,等温结晶温度(100 ℃～140 ℃)对iPP中β晶型含量的影响,发现在130 ℃～140 ℃之间发生β→α晶型转变.     

β-成核剂对聚丙烯/木粉复合材料结晶与力学性能的影响

通过挤出成型法制备聚丙烯/木粉复合材料(PP/WF),添加一种镧系稀土金属络合物(WBG)成核剂诱导PP/WF复合材料中等规聚丙烯(iPP)形成β晶型。以差示扫描量热和X射线衍射为表征方法,分析成核剂对PP/WF结晶行为的作用,进而研究其对力学性能的影响。结果表明,WBG成核剂能有效地诱导PP/WF产生β-iPP结晶,当WBG的添加量为m(WBG)/m(PP)=0.3/100时其产生的β晶相对含量达到78.75%,β-iPP的相对含量还与PP/WF的冷却速率密切相关;添加WBG提高了复合材料中iPP的结晶温度;WBG成核剂能显著改善复合材料的冲击韧性,但对弯曲和拉伸性能略有不利影响。     

硅灰石填充β-聚丙烯基复合材料的增强增韧

为了获得高韧性硅灰石填充β-聚丙烯基（W/β-PP）复合材料,采用负载庚二酸钙的硅灰石（β-W）填充聚丙烯（PP）制备。研究了W/β-PP复合材料中β-W的β-成核作用,并对比了硅灰石和β-W填充PP基复合材料的力学性能。结果表明:硅灰石填充聚丙烯（W/PP）复合材料主要形成α-晶,而β-W对PP结晶具有强的β-成核作用;W/PP复合材料的缺口冲击强度低于β-聚丙烯（β-PP）,硅灰石与PP的β-晶之间存在协同增韧作用,导致W/β-PP复合材料的缺口冲击强度高于β-PP;随着β-W含量的增加,W/β-PP复合材料的缺口冲击强度先增大后减小,在其质量分数为5%时达到最大值;同时硅灰石的增强作用可以提高β-PP的刚性。      

聚丙烯/硫酸钙晶须复合材料非等温结晶动力学及熔融行为

采用差示扫描量热仪研究了增容剂和稀土β成核剂对聚丙烯/硫酸钙晶须复合材料非等温结晶动力学及熔融行为的影响。动力学分析表明,莫志深方法能很好地描述聚丙烯非等温结晶动力学,达到相同的结晶度,复合材料所需要的冷却速率要小于纯基体。结晶形态和熔融行为均依赖于复合材料的组成和降温冷却速率。硫酸钙晶须具有一定的β成核作用,聚丙烯接枝马来酸酐(PP-g-MAH)的加入不利于β晶型的生成。     

硅烷偶联剂处理对 SF/PP结构和性能的影响

采用熔融共混和注塑成型的方法制备了硅烷偶联剂处理的剑麻短纤维(SF)增强聚丙烯(PP)的复合材料,研究了SF表面偶联剂处理对复合材料的晶形结构、微观结构、热性能及力学性能的影响.结果表明硅烷处理削弱了SF在PP结晶过程中的异相成核作用,降低了SF/PP复合材料中PP相的结晶度、结晶温度和结晶速率;提高了复合材料中β-晶型PP的相对含量;增强了SF/PP的界面键合,显著提高了复合材料的冲击强度.     

iPP/EBR合金的结晶和相形态

通过偏光显微镜(POM)、动态力学分析(DMA)、差示扫描量热(DSC)和扫描电镜(SEM)对等规聚丙烯/聚乙丁烯(iPP/EBR)合金的结晶和相形态进行了研究。结果表明,iPP和EBR在合金中是分别结晶的,组分EBR嵌入了iPP球晶;当EBR含量小于50%(质量分数,下同)时,合金中本体相iPP和分散相EBR处于相分离状态;而当EBR含量达到50%后,合金中还有EBR/iPP共存相。文中还提出了合金的相结构模型。     

Preparation and β-crystallization of zeolite filled isotactic polypropylene composites

In order to prepare the zeolite filled β-iPP composites, zeolite supported by calcium pimelate as β-nucleator (β-zeolite) was prepared by the interaction between calcified zeolite and pimelic acid. The effects of Ca(Ac)₂ solution concentration in the prepared calcified zeolite process and pimelic acid content on β-nucleating ability of β-zeolite were investigated and the crystallization and melting characteristic of zeolite, calcified zeolite and β-zeolite filled iPP composites were compared. DSC and WXAD analysis indicated that the zeolite and calcified zeolite have α-nucleation and the prepared β-zeolite has high β-nucleating ability for iPP crystallization. The β-nucleating ability of prepared β-zeolite is dependent of Ca(Ac)₂ solution concentration and pimelic acid content. The prepared β-zeolite content has little influence on the crystallization and melting characteristic and the β-phase content of the filled iPP composites. The zeolite filled β-iPP composites with high β-phase content can be easily obtained by adding β-zeolite into the iPP matrix.     

二价芳基杂环磷酸盐/月桂酸钠对聚丙烯性能的协同效应

以芳基杂环磷酸盐(AHPS)作为成核剂主体,月桂酸钠(NaL)为配体,研究该类复配体诱导等规聚丙烯(iPP)成核的协效作用,通过偏光显微观察、差示扫描量热分析、力学性能测试、光学性能测试以及耐热性能表征等手段,研究成核剂复配前后对复合材料球晶结构、结晶行为以及力学性能、光学性能、耐热性的影响。结果表明,NaL对iPP的成核作用较差,对球晶尺寸的细化不明显,平均尺寸为246μm,与纯iPP在球晶尺度在同一数量级,结晶温度提高仅为2.61℃,成核有效性低于10%,对复合材料力学性能、光学性能及耐热性的改善非常有限;AHPS对iPP的成核作用达到中等水平,晶体尺寸比纯iPP减小了1个数量级,平均尺寸为40μm,结晶温度平均提高7.26℃,成核有效性提高23.0%,力学性能、光学性能及耐热性同样达到中等水平;NaL与AHPS复配后使iPP的球晶尺度迅速减小,结晶峰值温度可提高20℃以上,成核有效性高达60%以上,拉伸强度、弯曲强度、弯曲模量平均分别提高14.8%、33.8%、38.7%,雾度值平均下降50.4%,透光率平均增加6.94%,热变形温度平均升高40.7%。NaL和AHPS之间表现出极强的协效成核作用。     

β-Crystal in the iPP melt encapsulated by transcrystallinity and spherulites: effect of molecular weight

The crystallization in isotactic polypropylene (iPP) melt inclusions, encapsulated by transcrystallinity and spherulites, was investigated by polarized light microscope. Generally, owing to the proceeding of crystallization in melt inclusions, a negative pressure will be built up. Up to a critical value, the negative pressure is released by the formation of cavitation in melt. Unexpectedly, β-crystals with different morphologies emerge at different locations in the melt inclusions. For low molecular weight iPP, only smaller β-crystals around bubbles are discernable. Turn to higher molecular weight iPP, apart from the smaller β-crystals, fan-shaped ones can be developed under suitable conditions (e.g., lower than 131 °C) at the growth front of spherulites and transcrystallinity. Considering the characteristics of molecular weight and morphology, it is proposed that β-crystals are induced by different mechanisms. That is, smaller β-crystals are resulted from the stress caused by the appearance of bubbles while the fan-shaped ones are derived due to the temperature gradient during the release of negative pressure.     

Isotactic polypropylene/polyisobutylene blends: morphology-structure-mechanical properties relationships

Morphological observations by optical and scanning electron microscopy, wide (WAXS) and small (SAXS) angle X-ray scattering, differential scanning calorimetry (DSC) and mechanical tests have been performed on sheet specimens of isotactic polypropylene (iPP)/polyisobutylene (PIB) blends obtained under different crystallization conditions. Two kinds of morphologies have been observed, particularly at high crystallization temperatureT _c, on thin sections of the same sheets: a spherulitic one in the centre and a row-like structure on the edges. The size of the spherulites, as well as the thickness of the row-like regions, decreases with diminishingT _c, and seemsto be independent of the amount of rubber. The adhesion among the spherulites and between the spherulites and the row-like regions seems to become poorer with higherT _c. The rubber particles seem to be evenly dispersed into the iPP matrix for samples quenched at low temperatures, whereas for samples isothermally crystallized (at highT _c) their concentration seems to be slightly higher at the border of the spherulites than in the centre. The overall crystallinity measured by DSC and by WAXS is an increasing function ofT _c and decreases with increasing amount of PIB. The index of iPP phase, quite low indeed (max 3%), drops with loweringT _c and with enhancing PIB percentage. The long spacingL for a given quenching temperatureT _q is independent of PIB content, whereas for isothermally crystallized samples at low undercooling varies differently according toT _c. The lamellar thicknessL _c is always a decreasing function of rubber content. Stress-strain analysis shows a more and more brittle behaviour both with increasingT _c (beyondT _c=122° C all the specimens are very brittle irrespective of PIB amount) and PIB amount in accordance with the morphological observations. Some tentative hypotheses have been made to explain the observed behaviour.     

Effects of carbon black-carbon nanotube complex fillers on the properties of isotactic polypropylene nanocomposites

In this study, the reinforcing effects of carbon black (CB) and carbon nanotube (CNT) complex fillers on the properties of isotactic polypropylene (iPP) nanocomposites were investigated using various methods. The surface of the CNTs was modified using a linear alkyl chain in order to create a homogeneous CNT dispersion in the iPP matrix. When the CB content that was incorporated in the iPP matrix increased, the thermal and mechanical properties of the iPP/CB nanocomposites were enhanced. Additionally these enhancements in the properties were similarly induced by introducing a small amount of alkylated CNTs (a-CNTs). In contrast, the CB/a-CNT complex filler was more effective for the iPP nanocomposites than the CB or a-CNT single filler in terms of the thermal stability and the electrical properties. However, the mechanical properties of the CB/a-CNT complex filler incorporated iPP nanocomposites were poorer than the only a-CNT incorporated iPP nanocomposites. Additionally, the complex filler did not overcome the nucleation behavior of the a-CNTs in the re-crystallization of iPP.     

Effect of pimelic acid on the crystallization, morphology and mechanical properties of polypropylene/wollastonite composites

The pimelic acid (PA) was used as a new surface modifier for wollastonite. The effects of PA treatment on the crystallization, morphology and mechanical properties of polypropylene/wollastonite composites were investigated. The Fourier transform infrared spectroscopy analysis revealed that the PA bonded to the wollastonite's surface and formed the calcium pimelate after reacting with the wollastonite. The results of wide angle X-ray diffraction, differential scanning calorimetry and polarized light microscopy proved that the PA treated wollastonite induced more β-crystalline form and decreased the spherulites sizes of polypropylene. The results of scanning electron microscopy showed that the PA treatment enhanced the interfacial adhesion between the filler and the matrix, indicating the improvement of the compatibility between polypropylene and wollastonite. The toughness of the composites was improved by the more ductile β-form spherulites. When 2.5 wt% of PA treated wollastonite was added, the Izod notched impact strength reached its maximum, a value of 17.33 kJ/m², which was 3.19 times greater than that of the blank polypropylene.     

Morphology, crystallization and melting behaviors of isotactic polypropylene/high density polyethylene blend: effect of the addition of short carbon fiber

The effect of vapor grown carbon fiber (VGCF) on the morphology, crystallization and melting behaviors of isotactic polypropylene (iPP)/high density polyethylene (HDPE) blend have been studied by means of Scanning Electron Microscopy (SEM) and Differential Scanning Calorimeter (DSC). It is found that the addition of VGCF results in a dramatic change in the morphology of iPP/HDPE blends. The crystallization peak temperature and melting point of iPP are not altered significantly by the blending. However, the degrees of crystallinity of iPP in the blends are reduced. Compared with the unfilled blends, the crystallization peak temperatures of iPP increase dramatically for the composites. The isothermal crystallization behavior of iPP is further investigated. The analysis of the crystallization half time shows that the crystallization rate of iPP is reduced by the presence of HDPE melt, and is enhanced by carbon fibers. For the unfilled blends in which iPP is the major component, the Avrami exponent closes to 3, independent of the HDPE content. However, for the composites, the Avrami exponent varies with the composition in a rather complex manner. An explanation based on heterogeneous and homogeneous nucleation is supposed. The sharp changes in the crystallization and melting behaviors for the composites containing 30–35wt% HDPE correspond to the sudden change in the morphology of the two phases. It is supported by the observation of SEM and the electrical measurement.     

Supermolecular structure of isotactic polypropylene

The crystalline structure, spherulitic crystallization and melting behaviour of isotactic polypropylene (iPP) is comprehensively reviewed, illustrated and discussed. It is demonstrated and summarized how the nucleation, development and growth of the different spherulites depend on the crystallization and melting conditions both in quiescent and sheared melt. Based on the results the microtexture development during real processing conditions is elucidated for selected examples. Several subjects of intense debate on the above topics are clarified using evidence from polarized optical micrography and differential scanning calorimetry.     

Crystallization behaviour and mechanical properties of polypropylene-based composites

The influence of glass fibres on the primary nucleation process, isothermal radial growth rate of spherulites and overall kinetic rate constant of isotactic polypropylene (iPP) has been examined. The polypropylene was also modified by means of acrylic acid (iPP^*) in order to improve the adhesion between the matrix and the fibres, and the relative properties were compared with those concerning the composites having as matrix plain MR Moreover the mechanical properties of injection-moulded composites containing iPP and iPP^* have been studied. These properties improved on increasing the fibre content. It was found that for the same glass-fibre content better values of the elongation at break and creep are observed in the case of reinforced polypropylenes having as matrix acrylic acid modified polypropylene.