A relationship between cross-link concentration and physical properties in natural rubber latex films at different calcium carbonate loadings

• Main Authors: Ab Rahim, Ruhida, Hassan, Aziz, Yusof, Nurul Hayati
• Format: Article
• Published: Springer 2022
• Subjects: QD Chemistry
• Online Access: http://eprints.um.edu.my/40915/

The present work is to investigate the influence of CaCO3 in NR latex films on cross-link concentrations and to study the relationship between cross-link concentrations and CaCO3 loadings. NR latex films were prepared from 10 pphr until 40 pphr CaCO3 loadings before evaluating the cross-link concentration by the Flory-Rehner equation and the samples were analysed by measuring the percentage of combined sulphur. The percentage of the total combined and free sulphur contents was analysed by an Automatic Analyser. The interaction between CaCO3 and rubber particles was observed through FTIR analysis. The surface morphology of NR latex films was examined by a Field-emission Scanning Electron Microscope (FESEM) and the tensile strength of NR latex film was evaluated. The results showed that an increase in CaCO3 loading resulted in decreasing cross-link concentration. The percentage of combined sulphur for unaged samples ranged from 18 to 37% was lower than for aged samples, ranging from 33 to 43%. It was also understood that the excess of CaCO3 agglomerated in NR latex films suppressed the cross-link concentrations and vulcanisation degree. Interestingly, the suppression did not affect the tensile strength due to the presence of CaCO3 as a semi-reinforcing filler. The FTIR spectroscopy confirmed the interaction between CaCO3 and rubber particles that could remain good tensile strength of NR latex films. Through the FESEM micrographs, the CaCO3 started to agglomerate at 35 pphr CaCO3 loading with a crack observed on the surface of NR latex film at 40 pphr CaCO3 loadings.