BS ISO 2303:2019 pdf download – Isoprene rubber (IR) — Non-oil-extended, solution- polymerized types — Evaluation procedures

BS ISO 2303:2019 pdf download – Isoprene rubber (IR) — Non-oil-extended, solution- polymerized types — Evaluation procedures
6.2.3 Laboratory internal mixer (LIM) mixing procedure
6.2.3.1 General
For a LIM having a nominal mixing capacity of 65 cm 3 to about 2 000 cm 3 , the batch mass shall be equal to the nominal mixer capacity, in cubic centimetres, multiplied by the compound density. The LIM conditions shall be the same for each batch mixed during the preparation of a series of identical mixes. At the beginning of each series of test mixes, a machine-conditioning batch shall be mixed using the same formulation as the mixes under test. The LIM shall be allowed to cool down to 60 °C between the end of one test batch and the start of the next. Temperature control settings shall not be altered during the mixing of a series of test batches.
6.2.3.2 Single-stage mixing procedure
The mixing technique shall be such as to obtain a good dispersion of all the ingredients. The final temperature of the batch discharged after mixing shall not exceed 120 °C. If necessary, adjust the batch mass, head temperature and/or rotor speed so that this condition is met. NOTE 1 Compounding materials other than rubber, carbon black and oil can be added to LIM batches more precisely and with greater ease if they are previously blended together in the proportions required by the formulation. Such blends can be made using a mortar and pestle, by mixing for 10 min in a biconical blender with the intensifier bar turning, or by mixing in a blender for five 3 s periods and scraping the inside of the blender to dislodge materials stuck to the sides after each 3 s mix. A Waring blender 1) has been found suitable for this method. Caution: if mixed longer than 3 s, the stearic acid might melt and prevent good dispersion. NOTE 2 An example of a mixing procedure for a LIM is as follows:
a) Load the rubber, lower the ram and allow the rubber to be masticated. 1,0 1,0
b) Raise the ram and add the pre-blended zinc oxide, sulfur, stearic acid and TBBS, taking care to avoid any loss. Then add the carbon black, sweep the orifice and lower the ram. 1,0 2,0
c) Allow the batch to mix. 7,0 9,0
d) Turn off the motor, raise the ram, remove the mixing chamber and discharge the batch. Record the maximum batch temperature.
e) After discharging the mixed batch, pass it through a mill set at 70 °C ± 5 °C once at a 0,5 mm mill opening, and then twice at a 0,3 mm mill opening.
f) Sheet the batch to an approximate thickness of 6 mm and check-weigh the batch (see ISO 2393). If the mass of the batch differs from the theoretical value by more than − + 1 5 0 5 , , %, discard the batch and re-mix.
g) Remove sufficient material from the batch for evaluating the vulcanization characteristics in accordance with ISO 6502-1 or ISO 6502-2. Condition this material for 2 h to 24 h, if possible at a standard temperature and humidity as defined in ISO 23529, before testing.
h) Sheet the batch to approximately 2,2 mm for preparing test slabs or to the appropriate thickness for preparing ISO ring test pieces in accordance with ISO 37.
i) Condition the batch for 2 h to 24 h prior to vulcanizing, if possible at a standard temperature and humidity as defined in ISO 23529.
6.2.3.3 Two-stage mixing including mill for final mixing procedure
6.2.3.3.1 General
The LIM shall be allowed to cool down to 60 °C between the end of one test batch and the start of the next.
6.2.3.3.2 Stage 1 — Initial mixing stage
The mixing technique shall be such as to obtain a good dispersion of all the ingredients.
The final temperature of the batch discharged after mixing shall be between 150 °C and 170 °C. If necessary, adjust the batch mass, head temperature and/or rotor speed so that this condition is met.BS ISO 2303 pdf download.