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Chinese Journal of Tropical Crops ›› 2022, Vol. 43 ›› Issue (12): 2545-2553.DOI: 10.3969/j.issn.1000-2561.2022.12.017

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Influence of Screw Extrusion Expansion Drying on Structure and Properties of Natural Rubber

CHEN Guojing1,2, WANG Bingbing2, LUO Ting3, LI Gaorong2, ZHANG Fuquan2, LIAO Jianhe1,*(), LIAO Lusheng2,*()   

  1. 1. School of Materials Science and Engineering, Hainan University, Haikou, Hainan 570288, China
    2. Agricultural Products Processing Research Institute, Chinese Academy of Tropical Agricultural Sciences / Hainan Provincial Key Laboratory of Natural Rubber Processing, Zhanjiang, Guangdong 524001, China
    3. Guangdong Guangken Rubber Group Co., Ltd., Guangzhou, Guangdong 510507, China
  • Received:2022-01-06 Revised:2022-03-23 Online:2022-12-25 Published:2023-01-12
  • Contact: LIAO Jianhe,LIAO Lusheng


Natural rubber is mainly dried by hot air. However, natural rubber is a poor conductor of heat and has strong self-adhesion, which leads to low drying efficiency, sticky rubber and entrapment in hot air drying, and adversely affects the performance of the product. Screw extrusion expansion drying process, a new drying method, has been widely used in the synthetic rubber industry due to the high drying efficiency, high automation level and stable process. And the drying process also has a good application prospect in the production of natural rubber (NR). In this paper, the structure of NR prepared by traditional hot air drying and screw extrusion expansion drying (respectively denoted as NT and NCT) was compared, and the performance characteristics of NCT were analyzed to explore the feasibility of screw extrusion expansion drying process in the production and processing of natural rubber. For raw rubber, the screw extrusion expansion drying process could reduce the thermo-oxidative degradation of the NR molecular chain during the drying process because of its low drying temperature and short drying time, so NCT had higher initial plastic value, Mooney viscosity and gel content than NT. The screw extrusion drying process had little effect on the non-rubber components, so the change range of the non-rubber components such as protein and volatiles was low. For the pure compound vulcanizate, NT exhibited a faster cure rate than NT. The contribution of the internal network structure of the vulcanizate was fitted using the Mooney-Rivlin equation. The effective crosslink density and the number of chemical crosslink networks after NCT vulcanization were relatively low. The conventional mechanical properties such as tensile strength, tear strength and modulus of NCT were lower than those of NT, and NCT exhibited higher fatigue temperature rise and higher degree of creep during dynamic loading. For carbon black vulcanizate, the conventional mechanical properties of NCT and NT were not significantly different., this may be due to the faster vulcanization rate of vulcanization accelerator N-tert-butylbenzothiazole-2-sulphenamide. However, NCT had longer fatigue life and better dynamic fatigue properties, which means the screw extrusion drying process could improve the dispersion of carbon black.

Key words: natural rubber, screw extrusion expansion, drying, network structure

CLC Number: