Influence of alkaline treatment and acetone extraction of natural rubber matrix on properties of carbon black filled natural rubber vulcanizates. (September 2020)

• Record Type: Journal Article
• Authors: Nun-anan, Phattarawadee; Wisunthorn, Suwaluk; Pichaiyut, Skulrat; Vennemann, Norbert; Kummerlöwe, Claudia; Nakason, Charoen
• Is Part Of: Polymer testing. Volume 89(2020)
• Publication Date: 2020-09
• Subjects: Alkaline treatment -- Acetone extraction -- Natural rubber vulcanizates -- Carbon black -- Network structures; Polymers -- Testing -- Periodicals; Polymères -- Tests -- Périodiques; 620.1920287
• DOI: 10.1016/j.polymertesting.2020.106623
• Languages: English
• ISSNs: 0142-9418

Abstract

Abstract: In this study, air dried sheet (ADS) showed higher molecular weight, proteins, lipids and more gel content than the low protein natural rubber (LPNR) from alkaline treatment or acetone-extracted natural rubber (AENR). After removal of proteins and lipids, LPNR and AENR had shorter scorch and cure times among the rubber compounds observed. This is due to higher content of free fatty acids, glycerides and sodium salts of fatty acid that might act as cure activators with sulfur curing. Furthermore, a finer dispersion of CB was found in ADS, due to chemical interactions of CB with proteins and lipids at terminal ends of NR molecules. Also, high molecular weight and gel in ADS could induce a higher reinforcing index ( α ) resulting to superior mechanical, dynamic, thermo-mechanical, hardness and crosslink density. In contrast, CB agglomerates occurred in LPNR and AENR with low molecular weight and reduced proteins and lipids, causing inferior mechanical, dynamic, thermo-mechanical, along with loss of stiffness and crosslink density. Highlights: Alkaline treatment and acetone extraction caused reduction of M ‾ w, protein, lipid and gel contents in NR. After removal of proteins and lipids, LPNR and AENR had shorter scorch and cure times. ADS compound had finer dispersion of CB due to chemical interactions with terminals of NR molecules. Proteins and lipids play important role in vulcanization and properties of CB-filled NR vulcanizates.