| Natural Rubber(NR)is a kind of natural renewable resources,which are applied in tire industry,medical and health industry and other areas.In the process of producing natural rubber,the method and technology of latex solidification has a great influence on the properties of natural rubber.And the methods of natural rubber coagulation include microbial coagulation and natural coagulation,acid coagulation,inorganic salt coagulation and other coagulation methods.At present,the most commonly used coagulation process in our country is acid coagulation which has some disadvantages,such as high energy consumption,serious environmental pollution,and so on.In the experiment of this paper,the thickening agent isooctyl alcohol,stearic acid and hydroxypropyl methyl cellulose(HPMC)was blend with fresh latex,and then mixed with acetic acid to gain the preparation auxiliary normal natural rubber(NR-f);By changing the method of solidification process,the latex with auxiliary coagulate agent was added into acetic acid gaining the rapid solidification of natural rubber(NR-q).Found by observing the phenomenon of fresh latex coagulation,NR-q solidification rate significantly faster than the solidification rate of acetic acid coagulation(NR-a),and colloidal particles soft hard moderate,besides acetic acid can be repeated use.It is found that the dry rubber content plays a important role in coagulation time.And the higher content of dry rubber,the shorter the time of solidification.The data indicate that with isooctyl alcohol,stearic acid and hydroxypropyl methyl cellulose as auxiliary solidifier preparation NR-q has the feasibility.This paper analyze the stability and form of the fresh latex by the methods of Melvin laser particle size and Zeta potential analyzer,scanning electron microscopy(SEM).The detection of concreting particle size shows that by using of thickening treatment of fresh latex,the average size of particle increased from 299.7 nm to 299.7 nm.The potentiometric analysis of Zeta shows that the isoelectric point icreased from 3.16 to 3.16.SEM analysis shows that in the fresh latex rubber with auxiliary treatment,the latex particle assembled,and even demulsification appeared.All these data indicates that the stability of the fresh latex rubber with auxiliary treatment has been reduced.In the FTIR spectra of NR-f and NR-q,N-H of stretching vibration absorption enhanced.It shows that the rapid solidification of latex,the loss of protein is less.And Mw of NR-f increased from 6.07 X 105 to 7.33 × 105 and Mw of NR-q from 6.07 × 105 to 7.53 X 105,while molecular weight of NR-f decreased from 2.96 to 2.85 and of NR-q of NR-q from 2.96 to 2.86.From the tests of nitrogen content,the nitrogen content of the latex was increased with its rapid solidification.The results of the analysis showed that the nitrogen content increased from 0.33%to 0.45%,which was consistent with the results of FTIR,which indicated that the protein content of NR-q was higher.In the final of this paper,the physical and mechanical properties of natural rubber were analyzed by the microcomputer control universal testing machine.The results showed that the vulcanization time t90 and scorch time t10 of NR-f and NR-q increased,and cross-linking density of NR-f and NR-q increased,the tensile strength of NR-f increased from 18.0MPa to 20.5MPa and the tensile strength of NR-q from 18.0MPa to 19.1 MPa,the tear strength of NR-f increased from 28KN m-1to 34.5KN'm-1 and the tear strength of NR-q from 28KN'm-1to 33.8KN'm-1.All the data tell that mechanical properties increase while the vulcanization properties is decreasing.And analysis of Rubber processing analyzer(RPA)indicates that the mixing rubber loss factor(tan?)of NR-f and NR-q reduced,and elastic modulus(G ')augmented.It means that the processability of NR-f and NR-q is lower.Thermogravimetric analysis(TG)showed that the maximum degradation rate of NR-q was 378?,while NR-f and NR-q were increased by 6?.It manifests that the thermal stability of NR-f and NR-q is better. |
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