The effect of molecular structure of polypropylene on stretchability for biaxially oriented film

Tamura, Shinichi; Kuramoto, Itaru; Kanai, Toshitaka

doi:10.1002/pen.22180

Cited by 15 publications

(11 citation statements)

References 18 publications

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“…[3,13] The existence of large spherulites in a sheet makes the stretchability worsen. [3,13] The existence of large spherulites in a sheet makes the stretchability worsen.…”

Section: Light Scattering (Ls)mentioning

confidence: 99%

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The evaluation of stretchability and its applications for biaxially oriented polypropylene film

et al. 2017

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In recent years, plastic film is essential in our daily lives. Among them, polypropylene has good physical properties, for example, tensile strength, impact strength, and transparency. Recently, it was found that the stretchability of polypropylene (PP) is improved by blending a small amount of low modulus polypropylene (LMPP) which is a low tacticity polypropylene. The purpose of this research was to investigate the effect of blending LMPP, which has different characteristic of resin such as tacticity and molecular weight, on PP and to study the mechanism of the structure formation in a biaxial stretching process. The blending of LMPP to PP reduces the spherulite size and increases the thickness of the amorphous phase in the lamella without changing the thickness of the crystal phase, namely the melting temperature. LMPP blends also reduced the yield stress during the stretching process and increased the stress buildup ratio. For these reasons, it improved film thickness uniformity of biaxially stretched film and reduced film break during the high production line. Furthermore, as the stretchable temperature window was widened to the low-temperature side, the thickness uniformity was improved in the wide stretchable temperature. As a result, improving the stretchability and the film thickness uniformity of PP were achieved by blending LMPP to PP. K E Y W O R D Sbiaxial stretching, crystallinity, low modulus PP, stretchable temperature width, tacticity

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“…[3,13] The existence of large spherulites in a sheet makes the stretchability worsen. [3,13] The existence of large spherulites in a sheet makes the stretchability worsen.…”

Section: Light Scattering (Ls)mentioning

confidence: 99%

“…The spherulite size of the sheet sample was measured by light scattering. [3,13] The existence of large spherulites in a sheet makes the stretchability worsen. He-Ne laser (wavelength λ = 632.8 nm) was used as a light source.…”

Section: Light Scattering (Ls)mentioning

confidence: 99%

The evaluation of stretchability and its applications for biaxially oriented polypropylene film

et al. 2017

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“…In addition to the various researches on the stretchability of the BOPP films, the formation of crater‐like surface roughness of BOPP films was also reported with the connection of crystal system. The β crystal has a lower density of 921 kg/m and melting temperature of 148°C compared to those of α crystal of 936 kg/m and 164°C, respectively.…”

Section: Introductionmentioning

confidence: 98%

Control of well‐defined crater structures on the surface of biaxially oriented polypropylene film by adding nucleators

Tamura¹,

Kanai

2013

J of Applied Polymer Sci

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While it is common to add anti-blocking agents to biaxially oriented polypropylene (BOPP) films for general use in order to prevent blocking against each other, the technology of crater-like film surface roughness formed on the BOPP films without any additives is well known in the industrial BOPP film areas. Numerous studies have been reported on the crater-like film surface roughness on the BOPP films since the 1980s, but its formation mechanism and the controlling method of the crater-like film surface roughness are yet to be clarified. In our previous reports, we presented a new hypothesis of crater formation mechanism from a new point of view on sheet morphology and crater shape on the BOPP film surface. It was strongly influenced by the crystal grain shape in the surface layer of PP sheet. In this report, it was clarified that a nucleator has a big influence on the formation of the crystal grains in the surface layer of PP sheets and on the formation of craters. In addition, craters did not form on the BOPP films stretched from the sheet of which the skin layer with crystal grain was shaved, even though b crystal still remained. It was clarified that the crystal grain is trans-crystal from the observation using TEM. Therefore, it is concluded that the existence of b crystals in the surface layer of PP sheets is not essential in order to produce craters on BOPP films, but trans-crystals are necessary to form the craters.

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“…Through improving the thickness homogeneity, less material has to be used for films with a specified thickness, leading to lower process costs and a reduced environmental impact. In addition, it is evident that a higher thickness accuracy enables higher maximum stretching ratios, resulting in thinner films which still maintain the specified mechanical properties. For some applications, for example in capacitors, the thickness distribution of the capacitor film plays an important role for the whole function of the component …”

Section: Introductionmentioning

confidence: 99%

“…Besides the stretching parameters, the molecular structure of the polymer has an important influence on the thickness homogeneity of biaxial stretched films as well. Tamura et al investigated the relation between the stretching force and the resulting thickness homogeneity of BOPP with a table stretcher . Polypropylenes with different tacticity and molecular weight distribution (MWD) were used.…”

Section: Introductionmentioning

confidence: 99%

Binary and Ternary Blends of Polypropylene Types – Influence on the Homogeneity of Biaxial‐Oriented Films

Schubert

Kaschta

Seidl

et al. 2016

Macromolecular Symposia

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Summary Biaxial‐oriented polypropylene (BOPP) is one of the most used materials for industrial films and food packaging. In terms of environmental and economic issues, the reduction of the film thickness, increasing the homogeneity, enhancing the process efficiency and stability are in the focus of this work. A systematic investigation on the biaxial stretching process is presented in this study. Therefore, two commercial linear polypropylenes with different molar masses and a commercial long‐chain‐branched polypropylene were used to obtain binary and ternary blends to adjust the elongation behavior on the molecular level. The blending was carried out using a cast film process on a twin‐screw extruder. The cast films obtained, were investigated before and after biaxial stretching. The thickness distribution of the films, were used as a measure of the film homogeneity, before and after the film stretching process. It turns out that casting and biaxial stretching are competing steps with respect to the film homogeneity. The casting step is dominated by the extrusion behavior of the blends. With increasing amount of the long‐chain branched material extrusion flow instabilities appear leading to an irregular surface and to a poor film homogeneity. Contrarily, long‐chain branches promote a more homogeneous deformation during the biaxial stretching inducing strain hardening which leads to a self‐healing effect and thus to an improved film homogeneity. The homogeneity of the final stretched film depends on both, casting and stretching. Therefore, a desirable polymer blend recipe with a medium amount of long‐chain branches is revealed for the stretched film.

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The effect of molecular structure of polypropylene on stretchability for biaxially oriented film

Cited by 15 publications

References 18 publications

The evaluation of stretchability and its applications for biaxially oriented polypropylene film

The evaluation of stretchability and its applications for biaxially oriented polypropylene film

Control of well‐defined crater structures on the surface of biaxially oriented polypropylene film by adding nucleators

Binary and Ternary Blends of Polypropylene Types – Influence on the Homogeneity of Biaxial‐Oriented Films

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