Impact of thermal oxidation on mechanical behavior of polydicylopentadiene: Case of non-diffusion limited oxidation

Abstract

Impact of thermal oxidation on mechanical behavior of polydicyclopentadiene (pDCPD) is studied in this paper. Thermal oxidation is performed over a wide range of ageing temperature, from 20 C to 120 C using 60 mm thin films in order to avoid heterogeneous degradation through sample thickness. After several ageing durations, chemical changes were monitored using Fourier-transform infrared spectroscopy (FTIR) and network modification (e.g. glass transition, Tg) was measured using dynamic mechanical analysis (DMA). In addition, tensile tests and fracture tests, based on the essential work of fracture (EWF) concept, were used to study how oxidation affects some mechanical properties of pDCPD. During oxidation polydicyclopentadiene undergoes crosslinking due to the presence of double bonds that leads to a large increase in T g (from 150 to 225 C) as well as an increase in rubbery modulus. This increase in T g results in an increase in maximal stress that can be described using the Kambour relationship. In parallel, an embrittlement of the polymer is observed here with a decrease in both essential and non-essential work of fracture. Finally, it appears that the accelerating effect of ageing temperature can be described using an Arrhenius equation with an activation energy close to 65 kJ/mol for carbonyl formation, maximal stress changes and decrease in fracture energy.

Thermal oxidation of poly(dicyclopentadiene) - Effect of phenolic and hindered amine stabilizers

“…Let us recall that, according to previous works in PDCPD [12] or other polyolefins [16], the end of induction period (in terms of carbonyl build-up) corresponds to the loss of mechanical toughness (for example a drop in elongation at break), in other words to end-of-life (NB: a more thorough investigation will be presented in Ref. [17]). For better illustrating the effect of stabilizer concentration, the changes of oxidation rate and lifetime with concentration of stabilizers are summarized in Fig.…”

Enhanced thermo-oxidative stability of polydicyclopentadiene containing covalently bound nitroxide groups

“…As shown in a previous study [19] , determination of fracture properties in PDCPD can be achieved using DENT (double edge notched specimen) samples through the Essential Work of Fracture specially to understand the decrease in strain at break.…”

“…However, the effectiveness of such low-molar mass additive is limited by incompatibility [16] and migration out polymer matrix [17][18] . Despite the presence of BHT, PDCPD undergoes oxidation that favors crosslinking leading to a large increase in glass transition temperature ( T g ) together with an increase in rubbery modulus and maximal stress [19] and, as a consequence, an embrittlement of the polymer. Use of the hindered amine light stabilizer (HALS) stabilizer Tinuvin 123 or Chimassorb 2020 instead of BHT allows to improve the protection performance especially when lowering the ageing temperature [20] .…”

“…a decrease in elongation at break as well as an increase in maximal stress and finally a complete embrittlement for PDCPD-BHT (after 120 h at 60 °C). The most interesting point here is the fact that even after 408 h at 60 °C, P(DCPD-NB-TEMPO) is not brittle whereas PDCPD-BHT is brittle after 120 h. These results confirm improvement of the PDCPD durability already observed by FT-IR spectroscopy and mass changes using nitroxide radical-containing norbornene both as stabilizer and comonomer.As shown in a previous study[19] , determination of fracture properties in PDCPD can be achieved using DENT (double edge notched specimen) samples through the Essential Work of Fracture specially to understand the decrease in strain at break.At the unaged state, the energy necessary to propagate a crack in P(DCPD-NB-TEMPO) is lower than for PDCPD-BHT . Here again, this behaviour could be due to a lower crosslink density in the…”

Thermal aging of acrylic-urethane network: Kinetic modeling and end-of-life criteria combined with mechanical properties

“…For evaluating the resistance to crack propagation, the Essential Work of Fracture (EWF) method [11,12] should be the first choice, which analyzes the fracture properties of notched specimens. As one of the alternative options, it is sometimes evaluated from the area under the stress-strain curve [13] of the classical tensile test, a routine procedure for characterizing mechanical properties in the polymer degradation field [4,14,15].…”