| The skim rubber latex is the by-product of natural rubber latex concentrate. Skim rubber was recycled by the process which was to remove ammonia, add sulfuric acid to manufacture skim rubber. This technology leads to the poor quality of skim rubber, difficult treatment of wastewater and so on. Now the skim rubber latex is recycled by membrane separation technique for the purpose of solidification by acetic acid instead of sulfuric in this paper, which can not only improve the quality of skim rubber but also decrease the cost of wastewater treatment.Microfiltration membrane with bidirectional flow process was used to recycle the skim rubber latex. This paper studies the impact on transmembrane pressure, switch frequency and cross-flow velocity in order to optimize technological parameters. While transmembrane pressure, switch frequency and cross-flow velocity were0.6MPa,5min/every time and3m/s respectively, dry rubber content of skim rubber latex after concentration was improved from5%to18%from the experiment result.The skim rubber latex after concentration was studied with mechanical property, aging resistance, viscoelastic behavior and thermal-oxidative stability and was analyzed the difference in performance with compare of skim rubber which was solidificated by sulfuric acid(NR-s). From the experimental outcome:(1)the tensile strength,300stretching stress and500strething stress of the skim rubber recycled by membrane(NR-m) is27.49MPa,4.52MPa and15.20MPa which was elevated about9.35%,16.59%and35.72%in comparison with NR-s, but it’s elongation at break is632%which was decreased10.23%.(2)The viscoelastic behavior of NR-m is better. Rheological index of NR-m is0.2758and is relatively high compared with that of NR-s which is0.2862.(3)Microfiltration membrane with bidirectional flow process is helpful to improve the behavior of aging resistance. The maximum and minimum of the differential value of loss factor of NR-m is0.0780and0.0265, which is lower than that of NR-s.(4) The thermal-oxidative degradation process of NR-m is three steps reaction, and the activation energy of NR-m is191.22KJ-mol-1, which is higher than that of NR-s which is173.52KJ’·mol-1.In the aging process the compare of chain structure and glass-transition temperature with different aging time is studied and analyzed. From the experimental results:(1)A large quantity of hydroxy in the molecular chains are generated and double bonds are pyrolyzed or oxidation and the number of methyl and methylene is reduced in the process of aging.(2)With the prolonging of aging time, glass-transition temperature changes from-61.37℃to-59.85℃, which shows that the change of the structure has great influence in glass-transition temperature of NR-m.The influence factors of the thermal stability and pyrolysis mechanism was studied. The results show that (1)the thermal-oxidative stability decreases gradually in the process of aging, which indicates that aging has great impact on the thermal stability.(2)With the upgrading of heating rate, the value of weight loss rate peak of NR-m is heightened from0.86to1.12℃/min, and correspondingly temperature is promoted from366.3to376.6℃.(3)The different atmosphere change the decomposition process of NR-m.The reaction under nitrogen atmosphere is one step,however, that under air atmosphere is three steps and the decomposition is more complete.(4)The pyrolysis product includes monomer and cyclic dimer mainly. The reactions of tadical transfer, disproportion, rearrangement and so on was generated in the process of pyrolysis. |
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