Rheological and cure properties of reactive blending product of maleated natural rubber and cassava starch
การวัดสมบัติการไหลและสมบัติการวัลคาไนซ์ของพอลิเมอร์เบลนด์ของยางธรรมชาติมาลีเอต และแป้งมันสำปะหลัง

Charoen Nakason, Asst. Prof., D. of Rubber Tech. and Polymer Sci., F. of Sci. and Tech., PSU.
Azizon Kaesaman, D. of Rubber Tech. and Polymer Sci., F. of Sci. and Tech., PSU.
Somluck Homsin, B.Sc. Student in Rubber Tech., PSU.
Suda Kiatkamjonwong, D. of Photographic Sci. and Printing Tech., F. of Sci., Chulalongkorn U., Bangkok
Corresponding e-mail : ncharoen@bunga.pn.psu.ac.th

Grant : Thailand Research Fund
Presented : IMT-GT UNINET Conference 2000 on Land Development and Sustainable Bio Resource, 10-12 October, Medan, Indonesia, p. 94
Key words : maleated natural rubber, cassava starch, rheological properties, cure properties

Graft copolymer of maleic anhydride and natural rubber or maleated natural rubber (MNR) was prepared in a molten state using internal mixer at 135oC. The products were then used as a blending composition and a compatibiliser for blending of natural rubber (5TR 5L) and cassava starch. The melt rheological behaviour in terms of Mooney viscosity, apparent shear stress and shear viscosity at 100,sup>oC were measured. The results found that pure MNR gave the lower apparent shear stress, shear viscosity than those of the blends with cassava starch. The rheological data of the MNR blends in-creased with increasing quantity of cassava starch. The highest values was observed for the blend of MNR. The rheological values, at the same level of cassava starch, were as follows : MNR > STR 5L with MNR as the compatibilisers > STR 5L compounds. Furthermore, rheological properties increased with increasing the levels of compatibiliser (MNR). The trends of rheological results were describes in terms of intermolecular interaction between the polar groups in the natural rubber and cassava starch molecules. Each rubber blend was later compounded and cure characteristics were studied. Pure MNR compounds exhibited long delayed onset of vulcanisation, approximately 10 minute. The retardation was described in terms of the higher chemical reactivity of accelerator (MBT) toward the anhydrides presence in the compound. Therefore, the accelerator lost the ability to perform a function as an ac-celerator. The retardation was not observe for the compound with the cassava starch. The cure curve for all of MNR were not in equilibrium at the maximum torque, while the pure STR 5L compound gave a cure curve with the maximum torque and a slight reversion. The cure curve for the compound with MNR as the compatibiliser was a combination of the cure curves of MNR and STR 5L. That is, the curve was in equilibrium at the maximum torque and short delayed action.
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