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EPDM mixing methods: Mixing binary ethylene propylene rubber is not difficult; it can be done using an open mill or an internal mixer. Mixing can be carried out using conventional methods or the reverse mixing method. Peroxides are added on the open mill at temperatures below 100°C. 1,1-Di-tert-butylperoxy-3,3,5-trimethylcyclohexane requires addition at temperatures below 80°C. Peroxides with a slow vulcanization rate, such as diisopropyl peroxide, can be added directly to the internal mixer. Mixing method for binary EPDM in a banbury mixer: Order of addition, Name, Mixing time, min, Roll gap, mm, Number of cuts 1 Raw rubber 1 0.6–0.8 As appropriate 2 Magnesium oxide 1 0.6–0.8 As appropriate 3 Add 1/2 amount of high-wear-resistant furnace black 4 0.6–0.8 As appropriate 4 Add another 1/2 amount of high-wear-resistant furnace black 1.5 0.6–0.8 As appropriate 5 Diisopropyl peroxide 3 0.6–0.8 As appropriate 6 Sulfur 3 0.6–0.8 As appropriate 7 Thinning agent 4–6 0.2–0.5 Pass through without rolling 10 times 8 Cutting the mixture into pieces 1 1.5–1.6 Total 32–34 EPDM mixing methods: The ISO mixing methods include Method A and Method B. Method A is an open mixing method ； Method B is mixing in a internal mixer, adding a vulcanization system in a open mill, and slitting the material. The methods used in ASATM to test the mixing processes of EPDM include the internal mixer method, the mini internal mixer method, and the open mill method. (1) Internal mixer mixing method: This method is based on ISO 4097—1980 (E) and ASTM D3568—81a. Mixing conditions: 150°C, 77 rpm. First stage of mixing: Sequence of adding ingredients – ① Raw rubber, zinc oxide, carbon black, oil, and stearic acid, for 0.5 minutes; ② Mix under pressure for 2.5 minutes; ③ Clean the mix, for 0.5 minutes; ④ Remove the mixture once the temperature reaches 150°C or after 5 minutes have passed. Thin passing on a open mill: The removed rubber mixture is immediately passed through a laboratory open mill with a roll spacing of 2.5 mm and roll temperatures of 50±5°C, three times. The weight of the batch is checked to ensure that the deviation from the theoretical value is no more than 0.5%; otherwise, the batch is discarded. After thin passing, the masterbatch should be allowed to rest for at least 30 minutes or until it reaches room temperature. Second stage of mixing: In the second stage of mixing using an open mill, sulfur and accelerators are added to the masterbatch that has been left to rest, on open mills with roll temperatures of 50±5°C and a roll spacing of 1.5 mm. After these ingredients are fully incorporated into the rubber mixture, the knives on each side are used three times to remove the mixture from the mill, after which the roll spacing is adjusted to 0.8 mm. The mixture is then passed through the mill six times before being cut into samples, which are prepared according to the specified methods. For the second stage of mixing using an internal mixer, the speed is 77 rpm and the temperature is 40±5°C. In this mixer, 1/2 of the masterbatch, accelerators, sulfur, and 1/2 of the masterbatch are added together. The rubber compound continues to be mixed until the temperature reaches 110°C or the total mixing time reaches 2 minutes; at that point the compound can be removed. After checking the weight of the batch again, specimens are prepared using the specified method (either on a open mill or an internal mixer). The order in which the ingredients are added is as follows: (2) Mixing method using an open mill – When mixing with an open mill, it is important to adjust the roll spacing so that a proper layer of rubber remains on the rolls as much as possible (or a continuous layer of rubber covering the rolls). Additionally, zinc oxide, carbon black, stearic acid, and oil should be mixed together before mixing begins. Kneading method for EPDM rubber in a kneader: Addition sequence, roller distance in mm, roller temperature in °C, time per ISO/ASTM standard in minutes. ISO ASTM ISO ASTM: 1, 2–1, 2–2; 3, 4, 5. Add raw rubber so that it covers the front roller. Use a scraper to apply 1/2 of the mixture evenly onto the roller; add zinc oxide, carbon black, and stearic acid mixture as well. Cut the material on each side once (up to 3/4 of the roller’s length), then add the remaining 1/2 of the mixture. After all the material has been added, cut each side three times – make sure there is no free carbon black on the surface of the piled rubber or the roller before making further cuts. Apply accelerators and sulfur evenly onto the roller; cut each side three times, allowing 15 seconds between each cut. Allow the rubber compound to settle, then pass it through the roller 6 times. Check and record the weight of the batch; the difference from the theoretical value should not exceed 0.5%, otherwise re-knead it. Values: 0.7, 0.7, 1.3, 1.8, 1.8, 0.8, 0.8, 0.8, 1.2, 1.2, 1.2, 0.8. Roller distance: 35±5, 35±5, 35±5, 35±5, 35±5, 35±5; temperature: 23±5, 23±5, 23±5, 23±5, 23±5, 23±5. Number of cuts: 1, 13, 3, 2, 2. Last edited by QXZ-1966 on 2009-2-26 at 15:28