The principle of foaming of rubber and its influencing factors

Update:15-02-2019
Summary:

The rubber foam is produced by solid rubber foaming. Th […]

The rubber foam is produced by solid rubber foaming. The principle is to add a foaming agent or a co-blowing agent to the selected rubber compound. At the vulcanization temperature, the foaming agent decomposes to release the gas, and is surrounded by the rubber to form a cell. 'Expand the compound to form a sponge. The main factors that determine and affect the cell structure are: the amount of gas generated by the blowing agent, the diffusion rate of the gas in the rubber, the viscosity of the rubber and the vulcanization rate. The most critical of these is the amount of gas generated by the blowing agent and the rate at which the gas is produced. Matches the vulcanization rate of the compound.
The amount of gas and the rate of decomposition of the foaming agent
The amount of gas generated by the blowing agent refers to the volume of the gas released by the complete decomposition of the blowing agent per unit mass in a standard state, and the unit is mL/g. The decomposition rate of the blowing agent refers to the amount of gas released by a certain amount of blowing agent per unit time at a certain temperature. Since the polymer itself does not change the decomposition mechanism of the blowing agent, the amount of gas generated by the blowing agent can be measured in the polymer. Usually, the foaming agent is placed in a certain temperature of inert dispersing agent (such as DOP or mineral oil), 'heating for a period of time' to collect the released gas' drawing gas volume (converted to the volume under standard conditions) as a function of heating time (Figure 6-1), the decomposition rate of the blowing agent at this temperature can be obtained from the slope of the curve, and the total volume of the gas after the decomposition is divided by the mass of the blowing agent to obtain the amount of gas generated by the blowing agent. Different types of foaming agents, different particle sizes, 'temperature difference', the decomposition speed is different. Under normal circumstances, the decomposition agent with low decomposition temperature has a high decomposition rate; for the same foaming agent, the particle size is small, the temperature is high, and the decomposition speed is fast. The gas generation amount and decomposition speed of the foaming agent affect the size and structure of the cell, the gas generation amount is large, the decomposition speed is fast, the formed cells are large, and the probability of opening is large.

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