Page 103 - Handbook of Adhesion Promoters

96 Polymer Modification to Improve Adhesion

Figure 6.2. The proposed scheme of the maleic anhydride/ethylene copolymerization. [Adapted, by permission,
from Manakhov, A; Michlícek, M; Necas, D; Polcák, J; Makhneva, E; Eliáš, M; Zajícková, L, Surf. Coat.
Technol., 295, 37-45, 2016.]

A thin poly(ethylene-alt-maleic anhydride) layer, having a thickness of around
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10 nm, was applied on the aluminum substrate prior to the epoxy coating. This resulted
in the formation of a cured, mixed poly(ethylene-alt-maleic anhydride)/epoxy interphasial
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region between coating and substrate. The poly(ethylene-alt-maleic anhydride)-based
o
system resulted in a very good initial adhesion and durability in presence of water at 40 C
for the epoxy coating but was not able to withstand 40°C 5% acetic acid and showed
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severe corrosion underneath the epoxy coating.
The enhanced interfacial adhesion (between polypropylene and bioflour filler), and
mechanical and thermal stability of the maleic anhydride-grafted PP-treated composites
strongly depended on the amount of maleic anhydride graft and the maleic anhydride-
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grafted PP molecular weight. The morphological properties of the maleic anhydride-
grafted PP-treated composites showed strong bonding and traces of pulled-out fragments
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of the matrix.
A combination of bis-(triethoxysilylpropyl)tetrasulfidesilane and maleic anhydride-
grafted polypropylene was chosen for surface pretreatment of the aluminum sheet to
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improve adhesion to epoxy. The silane and the anhydride participated in the curing reac-
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tions of the epoxy/polyamide system. Immersion of coating in boiling water for 80 h and
in NaCl water solution at 50°C for 180 h had little effect on silane-anhydride treated alu-
minum but did affect samples treated by either silane or maleic anhydride-grafted polypro-
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pylene alone.
The effect of styrene/maleic anhydride used as compatibilizer on the mechanical and
dynamic mechanical properties of blends composed of polyamide-6 and poly(butylene
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terephthalate) was studied. The increase in the amount of the compatibilizer led to a
more efficient dispersion of the PBT phase in PA-6/PBT blends and improvement of
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mechanical performance of the blend.
This method of adhesion improvement is very popular in practical applications as
illustrated by a large number of publications on the improvement of interfacial adhesion
between adhering product and substrate, adhesion of particulates to the matrix, and
improved compatibility of blend components. A sample of a cross-section of these publi-
cations is presented above.

6.4 MODIFICATION BY EPOXY GROUP
Bisphenol A type methacrylate, glycidyl methacrylate, acrylic acid, and a trifunctional
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monomer were cured by ultraviolet and thermal methods. Glycidyl methacrylate was
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used to insert the epoxy ring. Epoxy (meth)acrylates based on diglycidyl ether bisphenol
are commonly used because they allow for facile tuning of the adhesion, hardness and