The Application of Amine - Quinone Polymers in High Density Recording Media for Improved Corrosion Protection
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"TheUniversity of Alabama, Department of Metallurgical "TheUniversity of Alabama, Department of Chemistry
and Materials Engineering
Tuscaloosa, AL 35487 ABSTRACT High density, metal particle recording media consists of micron-sized iron particles in a polyurethane based polymer binder. In order to improve the corrosion resistance of the particles, two new amine-quinone (AQ) polymers, AQPU15 and AQPU100, have been investigated. Electrochemical impedance spectroscopy (EIS) was used to evaluate the corrosion behavior of iron substrates coated with two different thicknesses of each polymer. Results showed that the AQ polymers provide better protection compared with commercial polyurethane. The nature of the interaction at the polymer/metal interface has been investigated by FTIR-RA and XPS, which indicate that bonding probably occurs through the n system of the AQ functional group and the nitrogen of the soft segment, and through the quinone carbonyl functional group. INTRODUCTION The ability to record data on flexible magnetic media is principally responsible for the widespread, relatively inexpensive use of recorded sound and video images.' The media typically consists of two layers of materials, a relatively thin top layer (- 2 to 4 jim) consisting of magnetic particles in a polymer binder painted on a substrate (-10 gim thick), usually polyethylene terepthalate (PET).' Current research for increasing the storage capacity per unit volume of the tape has emphasized two approaches: (a) development of smaller particles with higher magnetization and (b) the use of thinner substrates. Metal (iron) particles are desirable over other particulate materials (e.g., yFe20 3) due to higher saturation magnetization (M,) and coercivity (He) but they are also more susceptible to corrosion.3' 4 In addition, as particle size decreases, the impact of corrosion is magnified, since even a tiny amount of corrosion can cause loss of data. Amine Quinone (AQ) polymers are a candidate material for use in metal particle tape binders due to their improved corrosion protection. In this study, the corrosion protection properties of two different AQ polymers namely, AQPU15 and AQPU100 have been examined by Electrochemical Impedance Spectroscopy (EIS). Reflectance-FTIR and XPS experiments on iron substrates coated with AQPU100 polymer and a model monomer (AQM I4A) have also been performed to determine the nature of the interaction at the polymer/metal interface.
439 Mat. Res. Soc. Symp. Proc. Vol. 517 c 1998 Materials Research Society
EXPERIMENTAL
EIS The polymer formulation and preparation is provided elsewhere.5 The structures of the AQPU 100 polymer, and the AQMI4A model monomer are shown in Figure 1. 0
CH3
CH -II N_ CH3 CH3
I .
II0 0
CH 2
1 NH
o
CH3
N 2
0
CH
0 2H
Hj [H
d-0
R0
3
Figure 1: AQM14A monomer and AQPU15 polymer. The difference between AQPUIOO and AQPU15 is the amount of AQMI. AQPU 100 contains 1% AQM 1 and AQPU 15 contains 40% AQM 1. The iron substrates (5 x 5 x 0.16 cm) used in this study were prepared by pol
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