Characterization of an amorphous surface layer on blown polyolefin film

Chang, Amy; Chum, S. P.; Hiltner, A.; Baer, E.

doi:10.1002/app.11282

Cited by 5 publications

(1 citation statement)

References 15 publications

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“…Segregation of highly mobile low molecular weight chains to the surface is well‐known. In LLDPE blown film, segregation takes the form of an amorphous surface layer 1, 2. Metallocene‐catalyzed copolymers possess homogeneous comonomer distribution and narrower molecular weight distribution.…”

Section: Introductionmentioning

confidence: 99%

Modifying adhesion of linear low‐density polyethylene to polypropylene by blending with a homogeneous ethylene copolymer

Poon

Chum

Hiltner

et al. 2004

J of Applied Polymer Sci

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Adhesion of a Ziegler-Natta catalyzed ethylene copolymer (ZNPE) to polypropylene (PP) was studied by measuring the delamination toughness G of coextruded microlayers by using the T-peel test. Low values of G compared to a homogeneous copolymer with approximately the same short chain branch (SCB) content were attributed to an amorphous interfacial layer of low molecular weight, highly branched ZNPE fractions. Blending ZNPE with a homogeneous metallocene catalyzed copolymer (mPE) increased G. In this regard, mPE with higher SCB content was more effective than mPE with slightly lower SCB content. The ZNPE interface was mimicked by microlayering ZNPE and ZNPE blends with polystyrene from which the ZNPE layers were easily separated without damage to the surface. Examination with atomic force microscopy revealed a soft coating about 8 nm thick on the surface of the ZNPE layer. Blending with mPE reduced or eliminated the amorphous interfacial layer. It was proposed that mPE increased miscibility of low molecular weight, highly branched fractions of ZNPE and prevented their segregation at the interface. After blending with mPE eliminated the interfacial layer, G increased to a value comparable to that of a homogeneous copolymer with about the same SCB content as ZNPE bulk chains. The increase in G was attributed to epitaxial crystallization of the ethylene copolymer in the absence of an amorphous interfacial layer.

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Section: Introductionmentioning

confidence: 99%

Modifying adhesion of linear low‐density polyethylene to polypropylene by blending with a homogeneous ethylene copolymer

Poon

Chum

Hiltner

et al. 2004

J of Applied Polymer Sci

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Physicochemical principles of spinning of natural fibroin fibres and ways of using them in chemical fibre technology. Part 2. Structure and properties of natural fibroin fibres. Use of principles of biomimetics in developing chemical fibre technologies

Perepelkin

2007

Fibre Chem

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Natural silk fibres and cobweb silk fibres, like chemical fibres and filaments, have an amorphous-crystalline fibrillar structure [20-23, 36, 37] with a 50-60% degree of crystallinity (the lower figures are x-ray diffraction data and the higher figures are data from IR spectroscopy).The basic properties of natural silk filaments are as follows [15-19, 22, 23]: Density, g/cm 3 1.32-1.36 Linear density, tex <0.5 Strength, cN/tex 25-35 Elongation at break, % 18-25 Moisture content in standard conditions, % 10-13 The cross section of the fibres after spinning and boil-off is schematically shown in Fig. 13.The generalized results of studies [38,39] of the properties of natural silk from silkworms of different species, which correspondingly consists of fibroin of different amino acid composition, are reported in Table 6. The mechanical properties of the different types of natural silk with the relative content of amino acids with short side substituents (SC) that form oriented segments of the structure with regular packing of the macromolecules and the remaining amino acids with long side substituents (LC) in amorphous sections of the structure are compared. The higher the content of amino acids with short side substituents with respect to the number of amino acids with long side substituents (the latter impede formation of oriented, regularly packed regions), the higher the strength of the silk thread.The properties of cobweb thread vary in a wide range as a function of their purpose. Some information is reported in Table 7 in comparison to data for other kinds of fibres and threads [40].The fibroin for formation of the core (bearing) threads of web silk contains a significant proportion of amino acids with small side substituents. As a result, the threads formed have a highly ordered, oriented structure and high strength. For some spiders, the mechanical properties of the bearing thread attained can be within the following values: breaking stress of 2000-2500 MPa, elongation at break under 30%. This corresponds to a high value of the work of deformation before break, necessary for absorbing kinetic energy when the spider falls and then hangs on the newly formed thread. This combination of strength and deformation characteristics in chemical fibres has not yet been attained [36]: the strength of high-strength aliphatic St. Petersburg State University of Technology and Design.

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