Chapter 23
Cross-Poly(vinyl methyl ether)-Inter-CrossPolystyrene Interpenetrating Polymer Networks Loss Modulus and Damping Behavior 1
2
3
3,4
J. J. Fay , C. J.Murphy ,D. A.Thomas ,and L H. Sperling 1
3
Department of Chemistry; Department of Material Science and Engineering; and Department of Chemical Engineering, Lehigh University, Bethlehem, PA 18015 Department of Chemistry, East Stroudsburg University, East Stroudsburg, PA 18301 4
2
Cross-poly(vinyl methyl ether)-inter-cross– polystyrene, PVME/PS, IPNs and their corresponding blends were synthesized and characterized by dynamic mechanical spectroscopy, differential scanning calorimetry, and other methods. Midrange compositions of the IPNs were observed to be phase separated at room temperature. The microheterogeneous phase separation in the IPNs appears to be dependent on composition and the degree of crosslinking. DSC shows that the IPNs have broader glass transitions than the corresponding miscible polymer blends, which suggests decreased m i s c i b i l i t y in the IPNs. The development of a group contribution anaylsis to predict the integral of the linear loss modulus-temperature curves, the loss area, LA, is reviewed and u t i l i z e d to compare with the LA's obtained for the PVME/PS IPNs and blends. The LA's for the IPNs were found to be equal to the blends, independent of the exact extent of phase separation, and following the group contribution analysis to a good approximation. Polymers are u s e f u l sound and v i b r a t i o n damping m a t e r i a l s near t h e i r g l a s s t r a n s i t i o n temperature, T (1,2). The onset o f coordinated chain molecular motion i n the T r e g i o n permits the conversion o f v i b r a t i o n a l energy i n t o heat, thereby reducing t r a n s m i t t e d noise and v i b r a t i o n . Homopolymers and random copolymers c o n s t i t u t e useful damping m a t e r i a l s over a 20-30°C temperature range near g
g
0097-6156/90/0424-0415S06.00/0 © 1990 American Chemical Society
416
SOUND AND VIBRATION DAMPING WITH POLYMERS
T , corresponding t o about three decades o f frequency. C o i n c i d e n t a l l y , the a c o u s t i c spectrum spans a frequency range o f 20 t o 20,000 Hz, which i s a l s o t h r e e decades o f frequency. Immiscible polymer blends and g r a f t s , which are phase separated, e x h i b i t g l a s s t r a n s i t i o n s corresponding t o the t r a n s i t i o n s o f the i n d i v i d u a l components and do not damp e f f e c t i v e l y o u t s i d e these regions (3-5). With p a r t i a l l y m i s c i b l e systems, i n c r e a s e d mixing o f the components broadens the damping range. Comparatively, interp e n e t r a t i n g polymer networks, IPNs, which are d e f i n e d as a combination o f two polymers i n network form, have been shown t o e x h i b i t damping over much broader ranges o f temperature and frequency due t o microheterogeneous morphologies (6,7). F i g u r e 1 i l l u s t r a t e s t y p i c a l modulus and t a n
