Role of Chemical Functionality in the Adhesion of Aluminum and Isotactic Polypropylene
- 25 February 2021
- journal article
- research article
- Published by American Chemical Society (ACS) in ACS Applied Materials & Interfaces
- Vol. 13 (9), 11497-11506
- https://doi.org/10.1021/acsami.0c22988
Abstract
In the direct melt bonding of isotactic polypropylene (iPP) to aluminum (Al), the blending of a small amount of maleic anhydride-grafted PP (PPgMA) with iPP was found to induce a dramatic improvement of the strength of adhesion. The effect of blending PPgMA was, however, limited, maximizing at ∼20 wt % PPgMA. Incorporation of larger amounts of PPgMA reduced the strength of adhesion. We studied the mechanism of adhesion between Al and iPP by incorporating chemical functionality to the polymer side. The fracture surfaces produced by peeling off the interfaces were investigated by replicating the surface topographic features on a platinum thin film and analyzing them by scanning transmission electron microscopy (STEM) as well as by reconstructing three-dimensional (3D) surface structures with STEM tomography. The replica-STEM technique enabled us to visualize PP surface crystalline lamellar structures and their deformation upon the failure in 3D. We found that polymer/metal interfaces produced surface features in the failure that were similar to those associated with failure of entanglement-based polymer/polymer adhesion via chain pullout. A fractography study by replica-STEM suggested that the formation of a low-molecular-weight layer with low crystallinity at the interfacial region was responsible for the improvement of adhesion. The adhesion strength depended on the toughness of the “soft layer” and did not depend on the chemical bonding between PPgMA and Al. The interfacial chemical reaction between MA and the Al surface yielded PP with a grafted carboxylic acid (−COOH) group, which may have been excluded from the PP crystalline lamellae. We concluded that chemical bonding was not the primary reason for the improvement of adhesion, but it was necessary to induce the segregation of PPgMA in the interfacial region and the formation of the soft layer.Funding Information
- Japan Science and Technology Agency (JPMJMI18A2)
This publication has 40 references indexed in Scilit:
- In Situ Study of Buried Interfacial Bonding Mechanisms of Carboxylic Polymers on Zn SurfacesThe Journal of Physical Chemistry C, 2013
- The characterization of the interfacial interaction between polymeric methylene diphenyl diisocyanate and aluminum: a ToF‐SIMS and XPS studySurface and Interface Analysis, 2010
- Directly Probing Molecular Ordering at the Buried Polymer/Metal InterfaceMacromolecules, 2009
- Examination of the interface of a model adhesive joint by surface analysis: a study by XPS and ToF‐SIMSSurface and Interface Analysis, 2009
- Cover Picture: Macromol. Chem. Phys. 7/2005Macromolecular Chemistry and Physics, 2005
- Correlation of molecular conformation with adhesion at AlOx∕poly (ethylene terephthalate) interface studied by sum-frequency generation spectroscopyApplied Physics Letters, 2004
- Miscibility and crystallization in crystalline/crystalline blends of poly(butylene succinate)/poly(ethylene oxide)Polymer, 2003
- Adhesion between Immiscible Polymers Correlated with Interfacial EntanglementsMacromolecules, 2003
- Mechanical Properties of Homopolymer Interfaces: Transition from Simple Pullout To Crazing with Increasing Interfacial WidthMacromolecules, 1999
- Direct Correlation between Interfacial Width and Adhesion in Glassy PolymersMacromolecules, 1998