Preparation And Studies On Damping Materials Of PDMS/PMA IPNs

In this paper, Interpenetrating Polymer Networks (IPN) based on Polysiloxane (PDMS) and Poly(methyl acrylate) (PMA) were prepared by using MA monomer and two types of PDMS, which viscosities were 3300Pa S and 7000Pa S respectively. PDMS was crosslmked by tetraethyl orthosilicate. IPN s structure, the reaction mechanism, thermal decomposition kinetics, the damping properties and the morphology of PDMS/PMA IPN were investigated by a series of modern testing technology.The vulcanization reaction of the IPN and PDMS was determined by the Fourier transform infrared (FT-IR). The mechanism of the vulcanization did't change, no chemical reaction between the MA and the PDMS appeared.Therrnogravimetric analysis at heating rates 5,10,15 and 20 C/min was used to study the decomposition kinetics of the PDMS/PMA IPN in NI and in Air by using TG and DTG, and the upper limit of the temperature was 700 C. It was found that IPN began to decomposite at 350 C. The process of the thermal degradation was multiple steps, the curve of the rate of thermal decomposition had two peaks, one of which lied between 400 C~420 C and the other lied between 500 C~540 C, the result corresponded to the components of IPN. At the same time, especially in Air two peaks turned little and became a continuous process at low heating rate (5 C/min). The residue was 15% in Air compared to 3% in N2, because PDMS turned into SiO2 of solid state in Air, but DS of gas state in Na. The first peak was analyzed by the Doyle equation, it found that the apparent decomposition reaction order was 1.0 both of in N2 and in Air. The decomposition activation energy was lower in N2 than of in Air, which was 147.405 kJ-mol-1 and 192.656kJ.mol-1, respectively. It demonstrated that O2 took part in the complicated reaction.IPN materials constituted useful damping properties near their glasstransition temperature (Tg), but damping property of IPN was more significant atroom temperature than at the glass transition temperature. Using the dynamic mechanical analyzer(DMA), PDMS/PMA IPN was investigated at temperature of 5 - 180 C. The initiator, the component ratio, the type of PDMS and the filler effected the damping properties. The result showed that the damping ability varied with the parameter and there was an optimal value. The excellent damping material in the papers was IPN, where tan man was 0.735, and the damping functional temperature ranged with tan 8 >0.3 was 46 C. The micro-morphology and structure of PDMS/PMA IPN were characterized by two kinds of SEM. It showed that PDMS was a continuous phase, where the PMA like micro-ball dispersed. The reason was that PMA was linear polymer and that the incompatibility of PDMS and PMA leaded microphase separation.Additional, XPS analyzed the three kinds of elements in surface and interior of IPN, the results indicated that the content of the elements C, Si and 0 were misdistribution and different in surface as well as in interior of IPN. The reason was the poor compatibility of PDMS and PMA, and found that amount of initiator and the reaction rate effected the distribution.