(185w) Thermo-Oxidative Aging Property of Polyurethane with Different Hindered Phenol Antioxidants

Abstract:

   Polyurethane
foam (PU) has been used to fill the gap among ballast in polyurethane
stabilized ballast. For polymeric material, degradation caused by heat and/or oxygen
is inevitable during usage, which leads to deterioration of the performances[1-3]. Hindered phenol antioxidant (AO) is used to improve the thermo-oxidative
aging property of PU materials. To the best of our knowledge, there has been no
public report on the study of the relationship between chemical structure of AO
and the anti-aging efficiency. In this work, six different antioxidants (Figure
1, b~g), which have different terminal structures, were incorporated into
polyurethane matrix. Their influence on thermo-oxidative aging property in PU
was evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis
(TGA).

   The
thermo-oxidative stability of PU and PU/AO hybrids was characterized by
oxidative induction time (OIT)[3]. As shown in Figure 1, with incorporation of AOs with carbonyl (AO-f
and AO-g), OIT value was about 53 min, which was much higher than pure PU. With
incorporation of AOs with methyl or ethyl, OIT value of PU hybrids was similar
as pure PU. It was indicated that the AOs with carbonyl have better performance
than the one with methyl. It was speculated that absorb electrons was
beneficial to inhibiting the generation of free radical. Thus the thermo-oxidative stability was improved. The mechanism will be
explored in our future work. 

Figure 1. Determination the OIT value of PU/AO hybrids
(DSC measurement, 210 ^oC)

  In order to
investigate the influence of different AOs on the thermal stability of PU,
isothermal TGA was performed to characterize the weight loss at 280 ¡ãC in air
atmosphere (Figure 2). The PU/AO-f volatilized (decomposed) at the slowest rate
compared with that of the pure PU and other PU hybrids. For example, the pure
PU sample lost 30 % of weight in a time as short as 24 min, while the PP/AO-f
sample took 50 min for the same weight loss as the AO-f were incorporated into
the PU matrix. The remaining weight at 50 min was 70.0%, 52.2%, 45.9% and 42.5%
for PU/AO-f, PU/AO-c, PU/AO-d and PU, respectively. The above results indicated
that AO-f had high efficiency in inhibiting
the generation of free radical, which was consistent with DSC results.

Figure 2. Isothermal TGA of PU/AO hybrids at 200 ¡ãC in
air atmosphere

References:

1.      Chattopadhyay, D. K.; Webster, D. C.,
Thermal stability and flame retardancy of polyurethanes. Progress in Polymer
Science 2009, 34 (10), 1068-1133.

2.      Gao, X. W.; Hu, G. J.; Qian, Z.
Z.; Ding, Y. F.; Zhang, S. M.; Wang, D. J.; Yang, M. S., Immobilization of
antioxidant on nanosilica and the antioxidative behavior in low density
polyethylene. Polymer 2007, 48 (25), 7309-7315.

3.      Gao, X.; Meng, X.; Wang, H.; Wen,
B.; Ding, Y.; Zhang, S.; Yang, M., Antioxidant behaviour of a
nanosilica-immobilized antioxidant in polypropylene. Polymer Degradation and
Stability 2008, 93 (8), 1467-1471.