Effect of unsaturated chain end‐group on thermal oxidative behavior of polypropylene

Abstract

In order to clarify the influences of unsaturated chain end-groups on the oxidative degradation of isotactic polypropylene (iPP), values of activation energy ( E) for the oxidative degradation reactions of Zieglercatalyzed iPP (ZiPP) and metallocene-catalyzed iPP (MiPP) having similar tacticity were evaluated by the temperature dependence of the oxidation induction time as determined by thermogravimetric analysis over the range 130-145 • C. The correlation between the content of unsaturated chain end-groups and the change of E was also studied. The results obtained indicated that the unsaturated chain end-groups strongly influenced the rate of iPP degradation. Moreover, on addition of oligomer-like MiPP having unsaturated chain end-groups, the E value of ZiPP became lower, suggesting that iPP having unsaturated chain end-groups served as an infectious agent of the degradation.

Degradation behavior of polymer blend of isotactic polypropylenes with and without unsaturated chain end group

“…In our previous works [13,19], we have reported that TGA measurement is a useful method of studying the rate of thermal oxidative degradation. The weight change curves obtained by TGA are shown in figure 3.…”

“…In order to evaluate the degradation rate, in several samples, the durations of the induction period (t di ) were determined using the weight change curves obtained from the measurements at several constant temperatures (130, 135, 140 and 145 • C). The t di has been defined as the time (second) at the intersection of the tangent at the inflection point with the plateau line of the induction period [13,19]. The apparent activation energy ( E) was calculated from the Arrhenius plot of ln t di versus the reciprocal of temperature.…”

“…The lower iPP (MiPP) contained a number of unsaturated chain end groups [13]. In this work, the polymerization was performed under a propylene pressure of the 5 kgf cm −2 with an Al/Zr molar ratio of 3000 at 50…”

“…We have reported that unsaturated chain end groups influence the rate of iPP degradation [13]. Considering the higher resonance stability of the allyl radical, the unsaturated chain end group is expected to function as an initiator of degradation.…”

Physico-mechanical characterization and biodegradability behavior of polypropylene/poly(L-lactide) polymer blends

“…A number of efforts have been done to study the degradation behavior of PP and increase the same through various means [10][11][12][13][14][15]. It can be achieved if somehow PP is degraded to low-molecular-weight compounds so that microbes can easily attack the polymer surface [16].…”