Epitaxial- and Transcrystallization of Multilayer iPP/HDPE Film by a Partial Heating Process

Origin of Epitaxial Cold Crystallization of Poly(l-lactic acid) on Highly Oriented Polyethylene Substrate

“…The appearance of sharp and well-defined reflection spots of PLLA superimposed on the electron diffraction pattern of the PE substrate reveals an oriented crystallization of PLLA on the PE substrate; i.e., the PLLA grows from amorphous state epitaxially on the PE substrate. As mentioned in the Introduction, the PLLA can crystallize in three different modifications (α, β, and γ forms) depending on the preparation conditions. − The reflection spots of the PLLA appeared in the electron diffraction pattern have all been accounted for by an orthorhombic unit cell with axes a = 1.06 nm, b = 0.61 nm, and c = 2.88 nm as proposed by De Santis and Kovacs in 1968 . This means that the PLLA crystallized on the PE substrate in its α-form.…”

“…The special orientation can cause synergistic effect on property modification. − Therefore, there are a vast body of literatures that describe the epitaxial crystallization of polymers on different substrates. Great progress in understanding the mechanism of polymer epitaxy at a molecular level has already been achieved. , It should be pointed out that most of the studies on polymer epitaxy focus mainly on the resultant mutual orientation relationship and its origin via atomic force microscopy, X-ray diffraction, and transmission electron microscopy combined with electron diffraction. , When the polymer chains start to orient on the ordered substrate was, however, not concerned so much up to date. In our previous work, we found that the chain orientation of polycaprolactone (PCL) on the surface of highly oriented PE film starts already in the melt or supercooled melt, which initiates the oriented overgrowth of PCL on PE substrate during cooling and results in a parallel chain alignment of both polymers .…”

Oriented structure of PP/LLDPE multilayer and blends films

“…11. For an epitaxial nucleation, LLDPE crystal orientation develops along MD-TD plane but also possibly along ND [27], in which case it would be transcrystalline morphology. From the figure, neither cross-hatched epitaxial crystalline structure nor transcrystalline layers are observed in the thickness direction for the LLDPE lamellae.…”