Study on Properties of Natural Rubber Coagulated by Microwave Radiation
|Keywords||Natural rubber Microwave radiation Solidification Structure Performance|
Microwave has a strong penetration of the illuminated object, microwave radiation, the illuminated object absorbs energy to produce thermal effects (ie dielectric loss) into the sky deep heating effect of molecular dipole interaction. As an efficient, clean energy, microwave radiation has been applied to the study of natural rubber (NR) drying and the vulcanization of rubber, etc.. Microwave radiation applied to the NR solidification using a microwave high-frequency radiation in the protective layer of the rubber latex protein denaturation heated rapid heating of water molecules to thermal motion of latex micelles significantly accelerate, to overcome the biasing force of the micelles protective layer the colloidal reunion solidification. By microwave radiation NR conditions, as well as three different solidification methods (microwave radiation coagulation, acid coagulation and natural microbial coagulation) degradation of the performance of NR raw rubber vulcanizates structure and properties of vulcanized rubber hot, new glue The technology provides research-based. First, the effects of microwave radiation solidification NR process conditions. NR latex theory the penetration depth of calculation and complete solidification time (tc) by microwave radiation visits found that microwave radiation solidification process, the influence of the shape and size of the container will be generated for solidification effect, wherein the contained latex depth rather than the quality affect t. The decisive factors. The process conditions on the the microwave radiation solidification of NR vulcanizates strength, the test within optimum solidification conditions: 30% of the fresh latex concentration, microwave radiation temperature of 90 ° C, the unit volume of microwave radiation intensity 38.89KW / m3, latex depth of 12mm, microwave irradiation time 12min. Secondly, the study of three different solidification method obtained NR (i.e. microwave radiation solidification NR (NR-m), and acetic acid solidification NR (NR-a) (?) Mouth NATURAL microbial coagulation NR (NR-n)) in the raw rubber structure and properties of the different aspects. The results showed that: (1) the physicochemical properties of the NR-m impurity content, ash content, a high nitrogen content than NR-a and NR-n NR-m plasticity initial value (P0) and a Mooney viscosity between NR-a and NR-n, and plasticity retention index (PRI) was the highest, with microwave radiation solidification retained to NR in most non-plastic material; (2) compared the three infrared spectra found NR-m NH stretching vibration peak appears near 3315cm-1, the amine absorption bands appear at 1618cm-1 and 1073cm-1 near obvious protein absorption infrared spectra of the NR-m peak; molecular weight of (3) NR-m Mn, Mw and Mz than NR-n and NR-a small, but its molecular weight distribution breadth index greater. Furthermore, three different solidification method on the structure and properties of NR vulcanizates. Found that: (1) in terms of physical and mechanical properties, before aging, the tensile strength of the three vulcanizates were 23.6Mpa (NR-m) 20.1Mpa (NR-A), 24.5MPa (NR-N), NR- m vulcanizates modulus, elongation at break and tear strength than NR-a; after aging, the tensile strength retention ratio of the NR-m NR-a low, but higher than the NR-n. (2) comparison of the IR spectra before and after aging of the three vulcanizates found NR-m and NR-a vulcanized rubber prior to aging in the 1539 cm-1 having a significant absorption peak (corresponding to the zinc stearate, and NR protein amide II band), and after aging, weakened, NR-m and NR-a vulcanized rubber in the proteins involved in the oxidation reaction of the vulcanized rubber, thereby effectively preventing the degradation of the rubber molecule chains, which also partially explain why the NR- m NR-a mechanical properties after aging than the NR-n high. (3) In the aspect of the vulcanization characteristics, the NR-m sulfide induced time ts, scorch time t10, and the vulcanization time t90 than many short NR-a, and NR-n NR-m, maximum torque MH torque increase the large rate VM and the cure rate index VC is high, indicating that the vulcanization rate of NR-m faster than NR-a and NR-n. (4) the vulcanization kinetics study shows that the NR-m and NR-n, the vulcanization rate constant k is greater than of NR-a. (5) using the NMR method to test the three kinds of the crosslink density of the vulcanized rubber, the results showed that the NR-m, and NR NR-m and NR-n of vulcanized rubber crosslink density than the NR-a higher aging after 24h vulcanizate cross I-a density increases, which is related to the quality of vulcanized rubber network chain portion and after aging is reduced, the free end of an increase. Finally, using thermal analysis (TA) of the thermal degradation behavior of the three vulcanized rubber in a nitrogen atmosphere, and by the Achar law and Coats-Redfern's method is obtained the three vulcanizates thermal degradation reaction followed by the degradation mechanism functions and average The apparent activation energy Ea, frequency factor A kinetic parameters. The results showed that: three vulcanizates thermal degradation in a nitrogen atmosphere for one-step reaction, following the chemical reaction control mechanism, the thermal degradation of the NR-m vulcanizates average activation energy was 179.0 ~ 193.0 KJ · mmol-1, NR-a vulcanizate thermal degradation of the average activation energy of 172.8-181.3 KJ-mol-1, NR-n vulcanizates average activation energy for the thermal degradation of 162.0-162.6 KJ mol-1, NR-m vulcanizates than the NR-a and NR- n vulcanizates high thermal stability.