Characterization of structure and properties of polymer films made from blends of polyethylene with poly(4-methyl-1-pent
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Andrzej Pawlak
Polish Academy of Science, Department of Polymer Physics, Centre of Molecular and Macromecular Studies, Łód´z 90-363, Poland
Roman Wrzalik Biophysics and Molecular Physics Department, University of Silesia, Chorzów 41-500, Poland (Received 17 June 2016; accepted 21 November 2016)
The main aim of this research was investigation of the processing-structure-property relationship for polymer blends. The paper presents the results of tests on the structure, basic physical and porous properties of polymer films blend of low density polyethylene (LDPE) with poly(4methyl-1-pentene) (PMP). Studies utilizing LDPE/PMP blends were undertaken to investigate a three-stage process: melt-extrusion/annealing/uniaxial-stretching (MEAUS), and a two-stage process: melt-extrusion/uniaxial and biaxial stretching (MEUS and MEUBS), used to produce porous films. The permeability and porosity results coupled with small-angle x-ray scattering data provide a direct connection between changes in microstructure to the observed changes in gas transport properties.
I. INTRODUCTION
In recent years there has been much commercial interest in the development of polymer blends from large volume commodity plastics. Polyolefin blends have been studied to improve the processability and properties such as mechanical properties, heat stability and permeability, or gas-barrier of the homopolymers involved. Permeability of gas through polymer blends has been the subject of numerous investigations.1–5 Gas separation membranes prepared by blending are of great interest because a useful combination of the advantage of each polymer into a new product can be achieved and a continuous range of performance can be expected by controlling blend composition, the microstructure and the macrostructure. The ability to control the type of microstructure, the degree of molecules orientation, and porosity in blends of semicrystalline polymers is essential for the development of polymeric materials whose gas permeability can be controlled through changes in membrane processing conditions. Physical properties of polymer blends mostly depend on the degree of crystallinity and on the orientation distribution of the crystalline volume portion.6–8 Preferred molecular orientation is one of the advantageous results of the plastic deformation of polymeric materials.9–13 Plastic deformation of crystalline and amorphous phases in most semicrystalline polymers is often Contributing Editor: Sarah Morgan a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.471
accompanied by the cavitation.13–17 A cavitation phenomenon, meaning the formation of numerous voids (cavities), happens in many semicrystalline polymers deformed at temperatures above their glass transition.17–19 It is known that cavities develop when a polymer is stretched (uniaxially or biaxially) and that the local three-dimensional tensile stress is necessary for voiding.13–17 Many studies have been carried out to explain the mechanism of plastic deformation of semicrystall
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