Causes of haze of low-density polyethylene blown films

Homopolymer of vinylidene fluoride and its copolymers containing hexafluoropropylene (HFP) were prepared from free radical solution polymerizations and spin-coated on the glass slides to fabricate thin film with a thickness of $ 1 lm. It was found that the surface morphology of fluorinated thin films was strongly dependent on the crystallinity of polymers. In addition, the surface morphology was the most important factor to determine the optical transmittance of glass coated with the fluoropolymer thin film. As decreasing the crystallinity of the polymer by introducing HFP with a bulky CF 3 moiety, the surface of thin film became flattened and the transmittance of visible light was increased by reducing scattering.

Section: Effect Of Crystallinity On Surface Morphology and Optical Trmentioning

confidence: 99%

Effect of crystallinity on surface morphology and light transmittance of poly(vinylidene fluoride‐co‐hexafluoropropylene) thin film

Lee

et al. 2009

“…10,12 The size and the organization of the crystalline structures control an important part of the optical properties. 21 If some crystalline structures exist on the visible light wavelength scale, important reflexions and dispersions occur, creating haze.…”

Section: Optical Properties Modificationsmentioning

confidence: 99%

Optimization of PE/Binder/PA extrusion blow‐molded films. I. Heat sealing ability improvement using PE/EVA blends

Poisson¹,

Hervais²,

Lacrampe³

et al. 2005

ABSTRACT:The optimization of three-layer films (PE/ binder/PA) manufactured by extrusion blow molding presents significant industrial challenges. The main issue consists in combining use properties (e.g., impermeability to water steam and oxygen, welding properties) with high mechanical, optical, and adhesion performances, while maintaining cost-effectiveness. This article shows that the introduction of EVA in the PE layer improves the heat sealing ability and optical properties without degradation of the mechanical and adhesion performances. In the most favorable case, this modification leads to a 40% reduction of the heat sealing time, the other performances remaining either identical or higher. This leads to cost reduction of this manufacturing step while improving the flexibility of the process (wider process temperature window). The properties modifications observed can be explained by microstructure modifications (crystallinity, orientation, and molecular mobility).

“…34 Assuming the additivity of the crystalline and amorphous contributions to the total birefringence in a semicrystalline polymer, Stein 35 proposed the following relationship for measurements above the glass transition temperature where distortion or glassy birefringence should not be present (10) In this case, f c and f am are the crystalline and amorphous orientation functions, respectively, ⌬°c or ⌬°a m are the intrinsic birefringence values for the perfectly oriented crystalline and amorphous phases, respectively, and c is the crystalline volume fraction. The form birefringence is ⌬ form and is due to the distortion of the electric field of the incident light wave at the phase boundary of geometrically anisotropic structure.…”

Section: Birefringencementioning

confidence: 99%

“…For example, H v SALS (horizontal polarizer and vertical analyzer) of an undeformed optically anisotropic spherulitic morphology typically yields a symmetric four-lobed pattern termed the "cloverleaf" pattern that possesses fourfold symmetry. 10 Such unoriented optically anisotropic spherulitic superstructures are not normal for flow-induced morphologies, but have been observed in the case of linear lowdensity PE blown (BUR Ͼ 1) and cast roll films where near fourfold symmetry of the H v SALS patterns were found in some instances. 11 For isotactic poly(1-butene) (PB-1) tubular extruded films, studied by Hashimoto and coworkers, 12 "butterfly-type" H v SALS patterns occurred, which stemmed from isolated sheaf-like structures.…”

Section: Introductionmentioning

confidence: 99%

Microporous membranes of polyoxymethylene from a melt‐extrusion process: (I) effects of resin variables and extrusion conditions

Johnson

Wilkes

2001

A two-part study utilizing polyoxymethylene (POM) was undertaken to investigate a three stage process (melt extrusion/annealing/uniaxial stretching) (MEAUS) employed to produce microporous films. In this first part, three POM resins (D, E, and F) were melt extruded into tubular films (blowup ratio; BUR ϭ 1), where resin D has a higher weight average molecular weight (M w ) than resin E, but both possess similar and relatively narrow molecular-weight distributions (MWD). In contrast, resin F is characterized by a distinctly broader MWD while its M w is slightly higher than resin D. Specific attention was focused upon the morphological and crystal orientation results as a function MWD and M w . A stacked lamellar morphology was obtained in each case from the melt extrusion; however, the type of stacked lamellar morphology, planar or twisted, and the orientation state was found to depend upon both the resin characteristics and the melt-extrusion conditions. Atomic force microscopy and wide-angle X-ray scattering were the main techniques utilized to study the meltextruded films while dynamic melt rheometry in conjunction with the Carreau-Yasuda model aided in differentiating the melt-flow behavior of the three resins. Small-angle light scattering (SALS) was also employed to characterize the morphological state.