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1 .— . Session 1626 Polymer Dissolution Experiment for Chemical Engineering Laboratory

Zhihua Cao, Suphan Kovenklioglu, Dilhan M. Kalyon, Rahmi Yazici Stevens Institute of Technology

Introduction

Polymer dissolution is increasingly becoming important in pharmaceutical applications such as controlled release, polymer fractionation, microlithography and in the recovery and recycle of energetic materials where the polymeric binder which encapsulates other components of the energetic material must first be dissolved. Polymer dissolution rates can also be fairly accurately described by semi-empirical film models which chemical engineers extensively use in describing rate processes where the flOW is typically turbulent. The experiments can be easily performed in a three hour laboratory period by using a glass bottle with a magnetic stimer or by using an autoclave stirred with an impeller. The glass bottle offers the unique advantage of being able to monitor the dissolution process with a camera where one can observe how the changes in flow dynamics affect the rate of dissolution.

Experimental System

Schematics of the experimental set-up is shown in Figure 1. The glass (pyrex) bottle in which the dissolution experiments are to be carried out is heated electrically to control the temperature. The polymeric binder can be shaped into a sphere and suspended in the glass bottle at the end of a hooked wire. The solvent is heated to the desired temperature in the autoclave pressurized by an inert gas and transferred to the glass bottle. Agitation is achieved with a magnetic stirrer. Samples are to be collected at regular time intervals and analyzed by infrared spectroscopy using an FTIR. Collection of samples is done by opening the valve on the same line which is used for transferring the solvent under pressure into the glass bottle.

The polymeric binder is BAMO/AMMO ( 12% BAMO) thermoplastic elastomer which is obtained from the polymerization of BAMO (3,3-bis (azidomethyl)oxetane) and AMMO (3-azidomethyl-3 -methyloxetane) monomers. This binder is available from Thiokol Corporation. BAMO is a crystalline homopolymer forming the hard block and AMMO is an amorphous homopolymer forming the soft block of the energetic thermoplastic elastomer. THF and ethyl acetate are both effective solvents for the BAMO/AMMO polymer. However, the characteristic azide peak of 2100 cm-’ for this polymer is masked if ethyl acetate is used as the solvent. Hence if the IR technique is to be used to determine the binder concentration, it is necessary to use THF. We would like the students to use FTIR to gain experience with this increasingly important analytical tool. Refractive index measurements can also be used both with ethyl acetate and THF as solvents, however, these measurements are not accurate at low binder concentrations. If the dissolved binder is not recovered, it is important to work at low binder concentrations due to the high cost of the binder. ----

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Cao, Z., & Kovenklioglu, S., & Yazici, R., & Kalyon, D. M. (1996, June), Polymer Dissolution Experiment For Chemical Engineering Laboratory Paper presented at 1996 Annual Conference, Washington, District of Columbia. 10.18260/1-2--6239