POLYOLEFINES MECHANICAL RECYCLING CONSIDERING THE CARBONYL VARIATION DURING THE FIRST LIFE (II) A degradation mathematical model based on the dependence of the carbonyl index by the degradation time to measure the polyolefins degradability was proposed. The mathematical model was verified with good results with own and literature degradation data. It was demonstrated that the three aging parameters of the mathematical model that can be calculated by fitted method, reflect the degradation behaviour of primary and secondary polyolefins and can be used for quantitative estimation of the polyolefins degradability. The possibility of using the mathematical model for estimation the opportunity of using the mechanical recycling as recycling method is the practical importance of the obtained results. There is also, a mathematical demonstration of the reason for which the polymers can not be infinitely recycled as other materials like metals, glass e.g.