Introduction to Reactive Extrusion

Andrew Hollcraft

Traditional Batch Polymerization• Continuous stirred tank reactor

• Loop reactor

• Solvent based [1]• Recovery (5-20 times the polymer weight)

• Large and expensive

Reactive Extrusion• Usually co-rotating twin screw [2]

• Polymer production [1]• Condensation• Ionic • Radical • Emulsion

• Polymer modification• Grafting and crosslinking• Chain extension and branching• Depolymerization – MW fine control • Vulcanization

• Viscosity management and multi staging [1, 2, 3]• Stepwise additions• Venting byproducts • Specialty polymers

• All kinds of other chemistry

Grafting• Copolymer and additive stability [1]

• Plasticizers– no migration• Polyolefins – low surface energy

• Polar side group• Improved blend physical properties• Wider range of alloys available with polyamides, polyesters, polystyrene…

• Typically• Peroxide initiator (masterbatched) • Maleic anhydride crosslinker

• Polybutylene succinate [4]• Biodegradable polyester thermoplastic• Comparable to polypropylene • Improved nanocomposite performance

• Polymerization modeling [5]• Initiation• Propagation• Termination

• Combination• Disproportionation

• Assumptions

• Auto acceleration – runaway • Side reactions• Viscosity

Modeling - Kinetics

Rheology Control• Elasticity of polypropylene [1] • Slow elastic recovery

• Elastic strain frozen during high throughput manufacturing• Due to high MWD tail

• Reduced processability (1965)

• Tertiary carbon• Chain scission readily occurs

• Series of patents in the 70’s• Result: Narrow MWD

• Ease of processing

Reactive ExtrusionPros• Specialty polymers and blends

• Multistaging• Simple design [2]• Safety - low volume [6]• Short residence time• No solvent

• Environmentally friendly • Less capital investment and overhead• Reduction in produced resin cost (~10%) [1, 7]

Cons [1,6]• Cannot handle

• Long reaction times• High heat evolution

• Residence time and distribution are key• Chemistry challenges

• Larger educational barrier to entry

References1. Xanthos, Marino. Reactive Extrusion: Principles and Practice. Munich: Hanser, 1992. Print.2. "REACTIVE EXTRUSION." Clextral. Web. <http://www.clextral.com/technologies-and-lines/technologies-

et-procedes/reactive-extrusion/>.3. "Reactive Processing." Fraunhofer. Web.

<http://www.ict.fraunhofer.de/en/comp/pe/ce/reactive_processing.html#tabpanel-2>.4. Phua, Y. J. "Reactive Processing of Maleic Anhydride-grafted Poly(butylene Succinate) and the

Compatibilizing Effect on Poly(butylene Succinate) Nanocomposites." Expresspolymlett Express Polymer Letters 7.4 (2013): 340-54. Web.

5. "POLYMERIZATION KINETICS." Penn State Polymer Physics Group. Web. <http://www.plmsc.psu.edu/~manias/MatSE443/chapter3.pdf>.

6. Brown, M. W. R. Reactive Processing of Polymers. Shawbury, Shrewsbury, Shropshire: Rapra Technology, 1994. Print.Cheremisinoff, Nicholas P. Advanced Polymer Processing Operations. Westwood, NJ, U.S.A.: Noyes Publications, 1998. Print.

7. "Reactive Extrusion." Coperion. Web. <http://www.coperion.com/en/compounding-extrusion/applications-products/reactive-extrusion/>.