Polyurethane-PMMA SINs

S. C. Kim, D. Klempner, K. C. Frisch, and H. L. Frisch, Polyurethane Interpenetrating Polymer Networks. 4. Volume Resistivity Behavior of Polyurethane-poly(methyl methacrylate) Interpenetrating Polymer Networks, Macromolecules 10(6), 1191 (1977). Volume resistivity behavior of SINs. PU/PMMA SINs. 

H. Mizumachi and Y. Ogata, One-Step Synthesis of Viscoelastic Properties of Interpenetrating Polymer Networks Comprised of Polyurethane and Poly(methylmethacrylate), Nippon Setchaku Kyokai Shi 12(1) (1976). PU/PMMA SINs. 

In view of these promising results, SINs based on polyurethane (PU) and PMMA were prepared by... 

For simultaneous interpenetrating networks (SINs), two independent, non-interfering reactions are required. Thus, a chain and a step polymerization have been the method of choice for many such polymerizations. Typical examples have involved PS and polyurethanes [Hourston and Schafer, 1996 Mishra et ai, 1995], and PMMA. A key factor in the kinetics of such polymerizations is to keep the system above the glass transition temperature of both components. If the glass transition of either the polymer network I or polymer network II rich phase vitrifies, the polymerization in that phase may slow dramatically. 

Fig. 6.3 The metastable phase diagram for the polyurethane-poly(methyl methacrylate) SIN at 60 °C. The PMMA gels at and above the plane Gi- U -PU. The intersection of the PMMA gelation plane and the surface along the curve A represents the condition of simultaneous phase separation and PMMA gelation... 

The gelation plane of the polyurethane is illustrated in Fig. 6.4 see G2-MMA-PMMA. For completeness, the gelation plane Gj of the PMMA from Fig. 6.3 is also shown. The gelation plane G2 occurred after about 67 % conversion of the PU. The intersection of the two planes, G1-G2, illustrates the line of simultaneous gelation of the two polymers. Reactions passing to one side or the other of this line will have one polymer or the other gelling first. It must be noted that the line G1-G2 also intersects the line A-B of Fig. 6.3, not shown. The intersection of these two curves expresses the presence of a triple critical point, where both polymers simultaneously gel and phase separate. While this triple critical point represents the ideal SIN synthesis condition, it would not, in general, produce the best physical or mechanical properties. 

K. Kircher and R. Pieper, Polyurethane-Polymethyl methacrylate Copolymers, Kunststoffe 68(3), 141 (1978). SINs of PU and PMMA are described. Moldings were prepared. Swellability flexural strength, impact strength, and surface hardness were determined. 

---