Role of strain induced crystallization and oxidative crosslinking in fracture properties of rubbers

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. a b s t r a c tTensile properties and crack propagation properties, especially critical strain energy release rate in mode I, G IC , have been used to investigate fracture properties of elastomers and their relationships with microstructure. These investigations were mainly based on a series of comparisons: first, the behaviour of polychloroprene rubber (CR), undergoing stress hardening due to strain induced crystallization (SIC) and oxidative crosslinking (OCL) was compared with that of chlorinated polyethylene (CPE), which undergoes SIC but not OCL, and with a polyurethane based on hydroxyl terminated polybutadiene (PU) which undergoes OCL but not SIC. Comparisons were also made on CR between fracture behaviour at ambient temperature, where SIC occurs and at 100 C where there is no SIC. Finally, oxidative crosslinking was used to vary in a continuous way the crosslink density in CR and PU, in order to evaluate the role of crosslinking in fracture behaviour. The results reveal the strong contribution of SIC to fracture strength. Crosslinking, even at low conversion, inhibits SIC which explains the sharp decrease of CR toughness in the early period of exposure to oxidation. When SIC has disappeared, it is possible to appreciate the effect of crosslinking on fracture behaviour. This effect, as evaluated from the density of deformation energy at rupture in tension or from G IC value, is almost negligible while the sample modulus increases regularly as a consequence of crosslinking. It appears that the toughness remains almost constant because it is under the influence of two contradictory phenomena: the negative effect of a reduction of ultimate elongation and the positive effect of a modulus increase. Such behaviour can be explained in terms of heterogeneous distribution of the lengths of elastically active chains. After long exposure, the sample behaviour becomes brittle, very high modulus values indicate that the samples approach, presumably in a heterogeneous way, the glassy state.

New developments in fracture of rubbers: Predictive tools and influence of thermal aging

“…CR is a polychloroprene rubber also vulcanized with sulfur compounds, whose exact chemical composition and thermal aging behavior were reported by Le Gac et al (2014) .…”

A large‐strain intrinsic default‐based fracture criterion for polymers: assessment in biaxial loading and application to ageing

“…Assuming that the average molar mass M c is the main indicator of the degradation evolution because of ageing, a master curve giving its evolution as a function of a reduced exposure time ta T was obtained by using the time–temperature equivalence principle: where , B and C are constants which values are 600 g.mol −1 , 1100 g.mol −1 and 9.5 × 10 −4 hour −1 , respectively.For the CR material, the data are issued from the work of Le Gac et al and were used to check the validity of the criterion. Only data for one temperature (100 °C) were available.…”

“…Evolution of the stretch at break as a function of the ageing time for the polychloroprene rubber material; symbol: experiments and line: criterion. [Colour figure can be viewed at wileyonlinelibrary.com]…”

Evaluation of metronidazole‐loaded poly(3‐hydroxybutyrate) membranes to potential application in periodontitis treatment

“…Regarding the membranes mechanical properties, if metronidazole is delivered to the media, less metronidazole would remain within the samples. Considering that metronidazole was a physical partial impairment to polymer chains packing, its delivery would allow strain‐induced crystallization, leading to slightly higher fracture strength and secant modulus after immersion …”

“…Considering that metronidazole was a physical partial impairment to polymer chains packing, its delivery would allow strain-induced crystallization, leading to slightly higher fracture strength and secant modulus after immersion. 36…”