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Materials Studio Products Used:
Amorphous Cell
COMPASS
Discover

Company:
General Electric - CRD

In Silico Determination of the Cohesive Properties of the Polyether Imide Ultem®

Scientists at General Electric-CRD, NY, USA, and Accelrys Inc. have used Accelrys' Materials Studio to determine the cohesive properties of the polyether imide, Ultem™.

Dr J. Stein, General Electric-CRD, comments, "The calculations were undertaken in order to develop silicone adhesive formulations which could be used to bond Ultem to plastics and metals. Understanding the cohesive properties of the Ultem allowed the team to understand the fundamental interactions governing adhesion of Ultem to modified silicones".

Ultem is a polyether imide that, like many engineering plastics, has cohesive properties that are difficult to obtain experimentally. Molecular modeling provides useful higher quality information than can be obtained by other methods.

Researchers at General Electric-CRD and Accelrys Inc. have used Accelrys' Materials Studio to determine the cohesive properties of Ultem and related molecules. Simulations were performed using Discover with periodic cells built with Amorphous Cell. Forces were calculated using COMPASS. Small molecular fragments (N-phenylphthalimide, 2,2-diphenylpropane, and diphenylether) of the repeat units were studied and oligomers up to 4-mer were simulated. The results were combined to estimate the properties of the polymer.

The simulations revealed the solubility parameter of Ultem to be ca. 22.0 MPa1/2. Interfacial interactions between Ultem and a number of low molecular liquids (iso-amyl acetate, n-amyl acetate, toluene, benzyl acetate, and ethylene glycol) were also evaluated with the aim of identifing functional groups that may favorably interact with the polymer for adhesive applications. The simulated results were in good agreement with results calculated from solubility parameters. Most importantly, all calculations were fully compatible with experimental results.

Dr J. Stein, General Electric-CRD, comments, "The calculations were undertaken in order to develop silicone adhesive formulations which could be used to bond Ultem to plastics and metals. Understanding the cohesive properties of the Ultem allowed the team to understand the fundamental interactions governing adhesion of Ultem to modified silicones".

Reference

  1. B. E. Eichinger, D. Rigby, and J. Stein, Polymer, 43, 599-607, 2002.