Pengaruh Penambahan Senyawa Merkaptan Pada Karet Alam (Hevea Brasiliensis) Dalam Fasa Padat
Situmorang, Juli Romaito
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Natural rubber had increasing viscosity while in transportation process and storage. This natural phenomenon called hardening, storage hardening, the process that happen in storage caused by cross bonding reaction in poly isoprene molecular chain with the aldehide that condense in non rubber substances or in rubber polymer chain. This symptom give disadvantages for consumer in processing rubber based products. To overcome this problem, the addition of rubber viscosity stabilizer could block the form of cross bonding on rubber molecular chain Stabilized viscosity rubber demand by the consumers because with the stabilized viscosity the premastication process is unnecessary, this process consumed 33-35% of the total energy needed to make rubber compound. Processing without the premastication will increase almost twice of the capacity in compound mixing. Besides it will also increase the consistency in compund mixing and viscosity of the rubber compound. The effect will reduce the scrap amount in processing rubber based product. The purpose of this research is to learn the effect of rubber viscosity stabilizer addition to the rubber stability with the variation of Cureo TS addition dosage, extruder temperature and time variation. The Cureo dosages that were used are 0%, 5%, 10%, and 15%. The main research designated to find the effect of Cureo TS addition on temperature addition (100oC, 120oC, 140oC) and time (3 minute, 4 minute, 5 minute) to the rubber stability. The test that done were chemical characteristics includes Po (Early Plasticity) and Pa (End Plasticity); PRI (Plasticity Retention Indeks); dan ASHT (Accelerated Strorage Haredening Test). The phisical characteristics test wit the Mooney viscosity test. Until now there no riset about the addition of Cureo TS as a stabilizer in rubber. The decision on using Cureo TS as stabilizer because it can react with the carbonyl group whether with the aldehide or keton. Reaction between merkaptan with the carbonyl group happen in two steps. The early product of the reaction is the hemi merkaptal or hemi merkaptol will react with the merkaptan group,either it is spontaneously or using catalyst to produce merkaptal or merkaptol. Rubber particle in latex contain aldehid group that bound to the cis-poly isoprene chain of rubber. The aldehid group in rubber expected to reacted with the merkaptan group that ussually added to rubber as peptizer. The aldehid group will react with merkaptan and form hemi merkaptal. Hemi merkaptal will react with merkaptan and form merkaptal. In the making of stabilized viscosity rubber, merkaptan usually contained in peptizer with the trade name Cureo TS. If in the rubber processing peptizer used as softener than the indirect use of peptizer could make the rubber stabile because the tiol group will blockade the aldehid group to form tioacetal, so there will be no gel forming. This will cause the rubber viscosity no increasing while in storage so the rubber becomes stabile. From the data it was found that from all treatment the Po number between 43 until 53. While the Po number for control are between 46.5 until 53. This number show that the Po number decrease compare with the control. The decreasing of Po number happens on 140oC, with the Cureo TS dosage of 15% and in 5 minute. The number show that the higher the temperature and the longer the time that was used to mixed Cureo TS with rubber that the rubber stability will be decreasing. The PRI number shows the selisih between rubber plasticity before and after the hardening as the effect of accelerated storage. From the result in general could be seen that the PRI number is between 40-50. This condition shows that there is an effect of the addition of Cureo TS on rubber stability. The numbers show that the rubber was more stable than before. From all the data show that there was a decreasing of ASHT, the optimal number of ASHT was eight, and most of the rubber that already sprayed with Cureo TS had ASHT number under eight. According to Refrizon (2003), if there is a sample that has increasing number of ASHT for eight unit or less (equal with the increasing of VR for 9-12 unit), will be said that the rubber viscosity is stabile. That number show that the rubber sprayed with Cureo TS was increase it’s viscosity stability. Based on the time variation could be seen that the good ASHT number is on five minutes. In the five minutes the number that obtain from the variation dosage 0%=8.00, 5%= 7.00, 10%=4.50, and 15% = 5.00. The ASHT number that obtain in the five minutes time with the variation Cureo TS dosage 0%, 5%, 10%, and 15% is decreasing. The longer the time needed to homogenize rubber on extruder than the more perfect the reaction that happen in the extrusion process between Cureo TS and rubber.