Nylon & High Performance Polymers: Ring Opening Polymerization, Lab Reports of Chemistry

Download Nylon & High Performance Polymers: Ring Opening Polymerization and more Lab Reports Chemistry in PDF only on Docsity! Dr. Derek Patton Techniques PSC341L/720 Electronic Handout 2008 D.L. Patton Nylon 6: Ring Opening Polymerization Polyamides Nylon is the term commonly used to describe aliphatic polyamides. Common aliphatic polyamides such as Nylon 6, Nylon 6,6 and Nylon 6,10 exhibit high mechanical strength, toughness, and chemical resistance, and can be drawn to form high-strength fibers. These nylons are commonly used in fiber and textile applications as well as in injection molding applications requiring chemical resistance and tight tolerance. Aromatic polyamides (or aramids) form ultra-high strength, high temperature fibers 1 . Kevlar was developed at DuPont in 1965 by research scientists Stephanie L. Kwolek 2,3 and Herbert Blades 4,5 . Kevlar has a strength-to-weight ratio five times that of steel. In addition to its high strength, Kevlar exhibits properties useful for a wide range of high performance applications, including excellent chemical resistance, wear and friction resistance, dimensional stability, and flame retardancy. Applications include: personal protection: bullet proof vests, body armor, cut-resistant gloves, thermal and cut-resistant protective clothing, motorcycle apparel, and helmets; sports equipment: composites for tennis rackets, hockey sticks, cast and spin rods, scuba dry suits, and kayaks; ropes and cables: high strength ropes to moor Navy vessels and to secure Mars Pathfinder, fishing line, fiber optic and electro-mechanical cables; and high performance tires: aircraft, off- road, “run-flat” tires, and many more. Nomex fiber was also developed over thirty years ago by DuPont scientists 6 . Nomex exhibits excellent flame and thermal resistance, and is used in applications such as flame- retardant racing apparel, firefighter protective clothing and industrial protective clothing; insulating material for generators and transformers; flexible high-temperature hoses for automotive under-the-hood applications; and lightweight honeycomb composite structures used in aircraft and naval applications. Ring Opening Polymerization Polymerizations may be classified as condensation, vinyl, or ring opening polymerizations. Ring opening polymerizations differ from the other types in that there is no elimination of a small molecule, as in condensation, and there is no loss of multiple- bonding enthalpy, as in vinyl polymerization. Ring opening polymerization is the primary commercial route to produce inorganic polymers 7 . Dr. Derek Patton Techniques PSC341L/720 Electronic Handout 2008 D.L. Patton Many important classes of polymers may be accessed through a variety of ring-opening polymerzations via various mechanisms including anionic, cationic, metathesis, etc. Shown below are examples of cyclic monomers that undergo ring-opening polymerization reactions: O O CH3 HN O O O R Ethylene oxide Propylene oxide N-carboxyanhydrides Norbornene N P N P N P Cl Cl Cl Cl Cl Cl Phosphazenes O Si O Si O Si OSi Siloxanes O O Lactones NH O Lactams Driving force for ROP The thermodynamic consideration, or the relative stability of the cyclic monomer and resulting polymer, is the most important factor in determining whether a cyclic monomer will undergo ring-opening polymerization. This is illustrated by the graph of free energy (hypothetical) for the polymerization of cycloalkanes with various ring sizes to polyethylene. Polymerization is favored thermodynamically for all but the 6-membered ring. Thus, ring-opening polymerization of 6-membered rings is generally not observed. Of course, kinetic considerations must also be taken into account but are not discussed here. 8 3 4 5 6 7 8 -100 -80 -60 -40 -20 0 20 ∆∆ ∆∆ G ( k c a l/ m o l) Ring Size Polymerizability thus follows 3,4 > 8 > 5,7 for the above cyclic monomers which results from various ring strains:
3-4 atoms → bond angle strain
5,7 atoms → torsional strain
8 atoms → transannular strain