Microscopic Structure

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Microscopic structure

Chemical and physical structure of polymers

In addition to the macroscopic structure of polymer material systems, the microscopic structure of the polymers, polymer blends or polymer composites involved is of great importance with regard to their influence on the material properties [1, 2]. The microscopic structure of polymers is made up of the chemical (molecular) and the physical (supermolecular) structure (see figure).

Bild:

Relationship between microscopic structure, influencing conditions and mechanical properties of polymers [1–4]

The chemical structure includes the molecular weight, the molecular weight distribution, the degree of branching (using the example of polyethylene) and the tacticity (using the example of polybutene-1) as well as the constitution of the macromolecules. The physical structure includes the mixing ratio in the case of a polymer blend, the phase structure, i.e. the presence of a homogeneous or heterogeneous or co-continuous phase(s) (see also: phase boundary surface), the size of the particles dispersed in the matrix in the case of a matrix-particle structure (heterogeneous phase structure), the degree of crystallinity and the shape of the super-molecular structure that forms, as well as the orientation of the crystalline phase [1, 2].

Microscopic structure of a PE-LD/iPB-1 blend system

The physical structure is significantly influenced by the chemical structure and the manufacturing and processing conditions. If, for example, the microscopic structure of a peel film blend system made of linear polyethylene and isotactic polybutene-1 (PE-LD/iPB-1 peel film blend system) is considered, the iPB-1 concentration in said peel film blend system is usually up to 20 wt.-%. Within this mixing ratio, the mixing of PE-LD and iPB-1 in the melt state leads to the formation of a matrix–particle structure, as PE-LD and iPB-1 are incompatible [5–7]. The incompatibility results from the given chemical structure of the two blend components. Thus, the blend components PE-LD and iPB-1 crystallise separately and form a corresponding supermolecular structure.

Further information on the relationship between the manufacturing conditions of the supermolecular structure and the mechanical properties of the peel film blend system is given in [8] or in the explanation of the following terms:

• T-peel test
• Fixed-arm peel test
• peel properties of peel systems
• peel force–elongation diagram
• peel angle

See also

• Micromechanics & nanomechanics
• Phase boundary surface
• Plastics
• Polymers & structure

References

[1]	Michler, G. H. (Ed.): Kunststoff-Mikromechanik. Morphologie, Deformations- und Bruchmechanismen. Carl Hanser, Munich Vienna (1992), (ISBN 3-446-17068-5; see AMK-Library under F 1)
[2]	Michler, G. H.: Atlas of Polymer Structures. Morphology, Deformation and Fracture Structures. Carl Hanser, Munich (2016) (ISBN 978-1-56990-557-9; E-Book ISBN 978-1-56990-558-6; see AMK-Library under F 14)
[3]	Wunderlich, B. (Ed.): Macromolecular Physics. Vol. 1: Crystal Structure, Morphology, Defects. Academic Press Inc., New York (2005) (ISBN 978-0-12-765601-4)
[4]	Patel, R. M., Butler, T. I., Walton, K. L., Knight, G. W.: Investigation of Processing-structure-properties Relationships in Polyethylene Blown Films. Polymer Engineering and Science 34 (1994) 1506–1514; https://doi.org/10.1002/pen.760341911
[5]	Rist, H.: Leicht und ruckfrei aufreißen. Neue Verpackung 4 (2005) 182–184
[6]	Stober, P., Rist, H.: Leicht und gefahrlos öffnen. Kunststoffe 6 (2004) 66–69
[7]	Hwo, C. C.: Polybutylene Blends as Easy Open Seal Coats for Flexible Packaging and Lidding. Journal of Plastic Film and Sheeting 3 (1987) 245–260
[8]	Nase, M.: Zusammenhang zwischen Herstellungsbedingungen, übermolekularer Struktur und Eigenschaften von Peelfolien. Shaker 2010 (ISBN 978-3-8322-9099-3; see AMK-Library under B 1-17)