Ante Agić

Thermal Degradation of Polyurethane Elastomers: Determination of Kinetic Parameters:

The objective of this study is determining the kinetic parameters of thermal degradation of polyurethane elastomers before and after UV irradiation. To determine the kinetic parameters of elastomeric polyurethane (PUR) decomposition the Freeman-Carroll method of calculation is applied. The effect of soft segment and hard segment type, soft segment molecular weight and hard segment content on the kinetic parameters of the degradation process were measured. Polyurethane elastomers were obtained from poly(oxytetramethylene) glycol, PTMO, of 1000 and 2000 molecular weight and polycaprolactone glycol of 1250 molecular weight (PCL), 4,40diphenylmethan diisocyanate (MDI) and 4,40-dicyclohexylmethane diisocyanate (H12MDI) and 1,4-butanediol as chain extender. The activation energy values obtained for PUR elastomers based on polyester soft segment were higher than those based on polyether soft segment.The PUR elastomers based on aromatic type of diisocyanate have lower activation energy values than those based on cycloaliphatic type of diisocyanate.

Kinetic Parameters Estimation for Thermal Degradation of Polyurethane Elastomers

In this work, thermogravimetric analysis is used to determine the kinetic parameters of thermal degradation of polyurethane (PU) elastomers, based on poly(ether polyol) soft segment and aromatic-type diisocyanates. To determine the kinetic parameters of PU thermal decomposition, a nonlinear regression procedure is applied. Parameter estimation is obtained by minimizing the weighted quadratic output error functional with the modified Nelder-Mead simplex search algorithm. The confidence region of pre-exponential factor-activation energy are established both for the first and second steps of degradation. The effect of the soft segment molecular weight and hard segment content on the activation energy of the degradation process has been studied.

Multiscale Modeling Electrospun Nanofiber Structures

The carbon nanotube (CNT) structure is a promising building block for future nanocomposite structures. Mechanical properties of the electrospun butadiene elastomer reinforced with CNT are analyzed by multiscale method. Effective properties of the fiber at microscale determined by homogenization procedure using modified shear-lag model, while on the macro scale effective properties for the point-bonded stochastic fibrous network determined by volume homogenization procedure using multilevel finite element. Random fibrous network was generated according experimentally determined stochastic quantificators. Influence of CNT reinforcement on elastic modulus of electrospun sheet on macroscopic level is determined.