聚丙烯／聚乙烯共混物高取向薄膜的形态结构研究

在等规聚丙烯(iPP)与高密度聚乙烯(HDPE)共混物的熔体拉伸薄膜中,两组份均以高取向的片晶形式存在,片晶生长方向垂直于拉伸方向。当iPP含量小于20％时,无明显的iPP相区存在;在iPP含量为40—60％时,两组份各自形成继续相,而在iPP含量大于70％时,HDPE以分散相存在。iPP的加入,使HDPE的片晶宽度减小,同时影响其结构的对称性,即由纯HDPE的非对称近单晶结构变为对称的纤维结构。 在制膜温度较高(135—140℃),HDPE含量较低(小于30％)时,HDPE在iPP上附生结晶。两种片晶的c轴成45°—50°交角,附生结晶的接触面为HDPE的(100)和iPP的(010)。     

左旋聚乳酸/聚(ε-己内酯)共混物在取向聚乙烯基底上的附生结晶行为

利用电子显微镜结合电子衍射研究了左旋聚乳酸/聚(ε-己内酯)(PLLA/PCL)共混物在取向聚乙烯(PE)基底上的结晶行为.纯PLLA在取向PE基底上能够附生结晶,主要形成分子链相互垂直的片晶结构.PCL在PE基质上也能发生附生结晶,导致两者分子链平行.PLLA/PCL共混物在取向PE基底上结晶的形态结构依赖于共混组成.在PLLA含量大于95 wt%时,PCL不影响PLLA与PE的附生结晶行为.当PCL含量增加至10 wt%时,PLLA在PE上的附生结晶行为受到了一定程度的影响.当PCL含量超过40 wt%时,PLLA在PE上的附生结晶被抑制,取而代之是PCL在PE取向基质上附生结晶,产生两者分子链平行的取向片晶.另外,在PLLA含量在50 wt%~30 wt%之间时,体系产生明显的微相分离,微相分离并不影响PCL与PE的附生结晶,在PCL的富集区仍然发生平行链附生结晶,而PLLA的富集区结构变得模糊.当PLLA含量少于20 wt%时,微相分离不明显,少量PLLA应该分散在PCL片晶间的非晶区.     

热处理对HDPE／iPP共混物中附生结晶的影响

木工作用透射电子显微术研究不同热处理温度对HDPE/iPP共混物溶液浇铸薄膜中附生结晶的影响。经热处理的共混物薄膜HDPE片晶尺寸明显增加,但其长轴仍与iPP成约50°夹角。电子衍射和暗场的实验结果及样品倾斜技术的利用证明了在iPP的两种结构区域中HDPE均在iPP上异相附生生长,两者的接触面为iPP的(010)和HDPE的(100)。在194℃热处理20min,然后自然冷却的HDPE/iPP共混物薄膜中的HDPE仍然在iPP上附生生长。     

聚己内酯和聚氧化乙烯共混体系中的两类片晶相间堆砌

对聚(ε-己内酯)(PCL)/聚氧化乙烯(PEO)共混物的相差显微镜、广角X-射线衍射(WAXD)、小角X-射线散射(SAXS)及示差扫描量热计(DSC)等的研究表明,只有当共混物中PCL(或PEO)的含量低于20％时,两组份是相容的.当PCL含量低于20％时,在共混物中形成了PEO片晶和PCL片晶相间堆砌的结晶形态,当PEO含量不超过20％时,PEO则完全以非晶形式混入PCL的非晶区,同时阻碍了PCL的结晶.可见在结晶过程中,相容的两组份对共混体系形态结构的影响却不尽相同.     

聚丙烯／氯化聚乙烯共混物的形态结构

用透射电子显微镜方法研究了聚丙烯（ｉＰＰ）和氯化聚乙烯（ＣＰＥ）共混物溶液浇铸膜的形态结构．共混物中ＣＰＥ含量≤７０％时不妨碍ｉＰＰ球晶两种结构（交叉结构和条状结构）区域的生成．在ＣＰＥ含量≥８０％时，分散相ｉＰＰ形成近乎直角（８０°）交叉的稀疏的片晶网络．在共混物的全组成范围内，ＣＰＥ结晶在ｉＰＰ片晶上附生生长，二者结晶Ｃ轴的交角为５０°     

聚丙烯／氯化聚乙烯共混物的形态结构

 用透射电子显微镜方法研究了聚丙烯（ｉＰＰ）和氯化聚乙烯（ＣＰＥ）共混物溶液浇铸膜的形态结构．共混物中ＣＰＥ含量≤７０％时不妨碍ｉＰＰ球晶两种结构（交叉结构和条状结构）区域的生成．在ＣＰＥ含量≥８０％时，分散相ｉＰＰ形成近乎直角（８０°）交叉的稀疏的片晶网络．在共混物的全组成范围内，ＣＰＥ结晶在ｉＰＰ片晶上附生生长，二者结晶Ｃ轴的交角为５０°     

剪切对iPP/PEcO共混物结晶行为的影响

对剪切场作用下的全同聚丙烯/弹性体乙烯-辛烯共聚物(iPP/PEcO)的共混物结晶行为进行研究, 结果表明, 剪切使得iPP球晶密度增加, 微晶和片晶均发生取向, 且片晶取向明显; 片晶取向度随共混物中PEcO含量的增加而增大, 而微晶取向度随PEcO含量的增加而减小; 强剪切诱导出现纤维状结晶形态. 利用同步辐射(SAXS)技术对共混物在剪切场下的等温结晶行为进行研究, 结果表明, 随结晶的进行长周期呈现先减少而后固定的趋势; 高剪切速率缩短了结晶诱导时间, 加快了共混物中结晶部分的结晶动力学过程.     

聚丙烯/高密度聚乙烯高取向共混物的附生结晶

<正> 最近,聚合物之间的附生结晶引起人们的极大兴趣和关注。附生结晶是一种结晶物质在另一种结晶物质上的取向生长,二者之间有特殊的作用。这种附生作用对结晶聚合物共混体系的形态结构和性能有极为重要的影响。本工作以电子显微镜方法研究熔体拉伸直接导致等规聚丙烯(iPP)和高密度聚乙烯(HDPE)共混物附生结晶。     

高密度聚乙烯/丁基橡胶共混体系形态与性能的研究

高密度聚乙烯(HDPE)与丁基橡胶(IIR)共混后,耐环境应力开裂性(ESCR)和抗冲击强度得到了提高。当IIR含量小于50％时,共混物中HDPE的晶格、结晶度、熔点保持未变。随IIR含量的增加,进入HDPE片晶间无定形区域的IIR量增加。少量IIR链段沿HDPE片晶厚度方向把一些片晶连接起来,共混物的抗冲击强度和ESCR因而获得显著提高。     

HDPE/iPP共混物中的附生结晶

本文用透射电子显微术、电子衍射和重金属投影等方法研究了溶液浇铸的HDPE/iPP共混物超薄膜中奇特的结晶形态,这种奇特的结晶形态是由于HDPE在iPP上异相附生生长造成的,二者的接触面为(010)_(ipp)和(100)_(HDPE),链轴间的夹角为iPP单斜角的一半(约50°),HDPE在iPP的两种结构(十字交叉结构和单晶型结构)区域中的生长方式有很大差别,依据结构分析提出两种片晶附生生长模型。     

Insight into understanding the evolution of the epitaxy crystallization in isotactic polypropylene and polyethylene blends

In this article, epitaxial structures have been successfully obtained in the isotactic polypropylene (iPP)/polyethylene (PE) blends by an accessible injection molding methods. By studying a series of iPP/PE blends, the evolution of the epitaxial growth of PE lamellae on the oriented iPP lamellae has been detailedly discussed via wide‐angle X‐ray diffraction, small‐angle X‐ray scattering, scanning electron microscopy and differential scanning calorimetry. Unexpectedly, the exactly epitaxial angles between peculiarly arranged PE lamellae and oriented PP lamellae are all larger than the classical epitaxy theory value of 50°, and it even increases gradually with increasing PP content. It is inferred that the special crystallization of PE is the consequence of joint construction of the oriented PP crystals and the continuous intense shear field provided by pressure vibration injection molding. The epitaxial structures play a positive role in the interfacial connection between two components; thus, the mechanical properties of the blends are improved. This work provides an insight understanding on the formation mechanism of the epitaxy crystallization under shear field. Copyright © 2017 John Wiley & Sons, Ltd.     

Epitaxial crystallization and oriented structure of linear low‐density polyethylene/isotactic polypropylene blends obtained via dynamic packing injection molding

In this work, as a part of a long‐term project aimed at controlling of crystal structure and phase morphology for a injection molded product, we investigated the oriented structure and possible epitaxial growth of polyolefin blend (low‐density polyethylene (LLDPE)/isotatic polypropylene (iPP)), achieved by dynamic packing injection molding, which introduced strong oscillatory shear on the gradually‐cooled melt during the packing process. The crystalline and oriented structures of the prepared blends with different compositions were estimated in detail through 2D X‐ray diffraction, calorimetry, and optical microscopy. As iPP was the dominant phase (its content was more than 50 wt%), our results indicated that it could be highly oriented in the blends. In such case, it was interesting to find that LLDPE epitaxially crystallized on the oriented iPP through a crystallographic matching between (100)_LLDPE and (010)_iPP, resulting in an inclination of LLDPE chains, about 50° to the iPP chain axis. On the other hand, as iPP was the minor phase, iPP was less oriented and no epitaxial growth between iPP and LLDPE was observed; even LLDPE remained oriented. The composition‐dependent epitaxial growth of LLDPE on oriented iPP could be understood as due to: (1) the effect of crystallization sequence, it was found that iPP always crystallized before LLDPE for all compositions; (2) the dependence of oriented iPP structure on the blend composition; (3) the “mutual nucleation” between LLDPE and iPP due to their partial miscibility. Copyright © 2009 John Wiley & Sons, Ltd.     

HDPE,LLDPE或LDPE高取向薄膜微结构的电子显微学研究

木工作用透射电子显微术及电子衍射技术研究3种PE(HDPE,LLDPE或LDPE)均聚物高取向薄膜的微结构。定量测定了它们的结晶尺寸。通过倾斜样品电子显微学研究确定了不同种PE纤维结构的对称性。     

Epitaxial behavior of HDPE on the boundary of highly oriented iPP substrates

The epitaxial crystallization behavior of high-density polyethylene on the boundary of highly oriented isotactic polypropylene (iPP) substrates has been investigated by means of atomic force microscopy (AFM) and transmission electron microscopy (TEM). The results obtained from AFM and TEM indicate that the epitaxial nucleation of HDPE on the highly oriented iPP substrates occurs earlier than that in the pure HDPE phase, i.e., homogeneous nucleation. Therefore the epitaxially grown HDPE lamellae can grow across the boundary of the iPP substrate into the HDPE spherulitic phase with the epitaxial orientation relationship remaining.     

Induced crystallization behavior of poly(ethylene adipate) by highly oriented polyethylene

The crystallization behavior of poly(ethylene adipate) (PEA) on highly oriented high-density polyethylene (PE) substrate both from solution and isotropic melt was studied by means of optical microscopy, differential scanning calorimetry, atomic force microscopy and electron diffraction. The results show that the PE influences the crystallization of PEA strongly, which results in an epitaxial growth of PEA with well ordered structure. At the boundary of the PE substrate, a transcrystalline PEA layer is observed. Fine structural observation illustrates that the PEA grows on the PE substrate in edge-on lamellae with fixed orientation. Electron diffraction demonstrates that the epitaxial organization of PEA on PE occurs with both polymer chains parallel, which leads to the (00l) PEA diffractions inclined ±23.5° to the chain direction of PE crystals. Combining the real space morphological observation and electron diffraction results, it is concluded that the epitaxial PEA edge-on lamellae are folded in the {00l} lattice planes.     

聚乙烯串晶在单轴拉伸形变过程中的微结构变化和机理

本文采用电子显微镜和小角Ｘ－射线散射（ＳＡＸＳ）技术研究了含有串晶结构（Ｓｈｉｓｈ—ｋｅｂａｂ）的高密度聚乙烯（ＨＤＰＥ）／超高分子量聚乙烯（ＵＨＭＷＰＥ）共混物高取向膜在单轴拉伸过程中的微结构变化．深入探讨了拉伸温度对聚乙烯在形变过程中微结构变化的影响．室温拉伸时，聚乙烯串晶结构主要发生了解结晶过程；高温（１１５℃）形变时，主要表现为折叠链片晶直接转变为伸展链纤维晶的应变诱导结晶过程．     

Growth stages in epitaxial crystallization of poly(γ-benzyl L-glutamate)

The electron microscope study of the isothermal epitaxial crystallization of PBLG on 001 cleavage surface of NaCl or KCl from 0.01% chloroform solution with various n-octane contents has shown that the epitaxial growth process could be divided in two stages. In the first stage a rapid growth of a lamellar layer 20–40 Å thick could be observed; the PBLG molecules in αhelix conformation are oriented along <110> substrate directions. The dimensions and perfectness of alignment of these lamellae along the <110> direction depends on the molecular weight of the PBLG. In the second stage of PBLG epitaxial crystallization the relatively slow thickening of some initial lamellae takes place and one can observe many types of secondary structures. With increasing thickness of the epitaxial structures and increasing molecular weight of the PBLG the degree of orientation in relation to <110> substrate direction diminishes. The two growth stages in PBLG epitaxial crystallization are related to different kinds of orienting and attracting forces of the alkali halide substrate.     

结晶性间同立构1,2-聚丁二烯的单晶结构

近十几年来 ,结晶性间同立构 1 ,2 -聚丁二烯引起人们的广泛关注 ,但绝大多数研究工作集中在聚合物的制备、物理性质和应用方面[1～ 3] ,对于其结晶行为和晶体结构则未见报道 .原因是间同立构 1 ,2 -聚丁二烯分子侧链含有大量的双键 ,在较高温度下很容易交联 ,特别是高间规度的聚合物 ,由于其熔融温度高 (>2 0 0℃ )则更易产生交联 ,这给结晶行为和结构研究带来很大困难 .结晶性间同立构 1 ,2 -聚丁二烯的晶体结构为平面锯齿链正交堆砌 ,Pacm空间群[4 ] .我们曾报道了结晶性间同立构 1 ,2 -聚丁二烯的合成和溶液浇铸膜的板条状结构[5] ,本…