Nonlinear viscoelasticity and stress‐softening behavior of chloroprene rubber reinforced by multiwalled carbon nanotubes

The viscoelasticity and stress-softening behavior of chloroprene rubber (CR) filled with multiwalled carbon nanotubes (MWCNT) and carboxylated multiwalled carbon nanotubes (MWCNT-COOH) were studied using a Rubber Process Analyzer 2000 (RPA2000). In the strain sweep measurements, it is found that CR/MWCNT and CR/MWCNT-COOH compounds have different behavior on storage modulus (G′). With increasing strain, G′ of CR/MWCNT (100/8) compound decreases at strain less than 2°, while G′ of CR/MWCNT-COOH (100/8) compound stays at constant, indicating that MWCNT-COOH has stronger filler–filler network and filler–rubber interactions as compared to MWCNT in CR matrix. CR/MWCNT (MWCNT-COOH) vulcanizates have higher G′ but lower loss modulus (G″) than the corresponding uncured compounds. Repeated strain sweep scans were carried out to study the stress-softening behavior of CR compounds. A stress-softening effect of the filled CR compounds is observed and becomes more pronounced with increasing loading of MWCNT or MWCNT-COOH. The correlation between the Payne effect and stress-softening effect of CR/MWCNT (MWCNT-COOH) vulcanizates is also studied. It is found that the difference of the storage moduli at 0.1° and 10° strain amplitudes and the difference of storage moduli of first and second strain sweeps at 0.1° strain amplitude show a positive linear correlation. POLYM. COMPOS., 35:2194–2202, 2014. © 2014 Society of Plastics Engineers