Three important regions could be identified in Fig. 1: i)
3400–3420 cm−1 attributed to OH stretching; ii) 1715–1737 cm−1
due to C=O stretching; and iii) 797–881 cm−1, assigned to=C–H
bending from trans 1,4-isomer and epoxide rings (873 cm−1). Peaks
assigned to OH and C=O groups were also observed, which arise
from products of degradation, such as alcohols, carboxylic acid,
hydroperoxide, aldehyde, ketone, ether or ester, some of which
appear owing to oxidation of polyisoprene [26]. In addition to the
main characteristic bands of the epoxide ring at 870 and 1250 cm−1
(Fig. 1), other bands of ring-opened structures were observed,
probably due to a chain-scission parallel mechanism caused by the temperature [27–29]. The most outstanding among them was the OH
stretching vibration in the 3200–3500 cm−1 region [30–33]