Identification
Features & Benefits
Applications & Uses
FICEL® liquids and pellets can be dispersed faster than equivalent powder blowing agents. This can lead to a significant reduction in the blending times and costs required to achieve uniform dispersion of the blowing agent throughout the polymer. The use of FICEL® pellets may eliminate the need for additional agents (e.g. paraffinic oil) to incorporate low concentrations of powder blowing agents. It also reduces the incidence of "screw slippage" when high levels of powder blowing agent and processing agent are used.
The superior quality and performance of FICEL® blowing agents has been proven by many years of commercial use in a wide variety of very demanding applications. The density of extrusions and plastisols can be reduced by more than 50%, which can significantly reduce the unit costs of production.
Addition levels of these products will vary according to the density of the foam required and the gas yield of the particular blowing agent. The gas yield of the blowing agent is a function of the amount of active blowing agent in the product (activators and carriers generally do not produce gas), and the type of blowing agent. A typical non-filled rubber has a specific gravity of 1.2 g/cc. To reduce the density of 100 g of this polymer by 50% (a sp gr of 0.6 g/cc) 100 ml of gas must be captured in the polymer melt. To calculate a starting-point level of the Parts of CBA/part of Polymer needed, use the formula:
Parts of CBA = [1/desired foam sp gr - 1/polymer sp gr] / gas yield of CBA
Example: 0.00325 g of azodicarbonamide (gas yield 220 cc/g) reduces the density of 1 g of rubber (sp gr 1.2) to a density of 0.6 g/cc. (For conversion to English units 1.0 g/cc = 62.4 pcf, pounds per cubic foot.)
The melt strength of the polymer and formulation play a critical role in determining the amount of gas that can be contained by the melt without rupturing the foam cells. Various blowing agent types produce different gases (for example nitrogen from azodicarbonamide), and in turn the different gases are more or less soluble in a particular polymer melt. It is desired that the solubility of the gas be such that it does not migrate rapidly through the melt to escape at the surface. Thus the density achieved depends on how much gas is delivered by the chemical blowing agent, as well as how much of that gas is retained in the polymer melt, this is generally referred to as the gas containment limit (GCL). This property value is dependant on the melt strength of the cell wall.
FICEL® products can be used at processing temperatures of 325 to 380 °F depending upon the product and processing equipment. The addition levels of these products will vary according to the density of the foam required and is typically:
0.25 % for powders, to 1.5 % for pellets
FICEL® pellets can be dispersed easily by tumble blending with the PVC pellet compound on standard equipment and adding the blend to the machine hopper for the processing, or volumetric or gravimetric feeders can be used. The FICEL® liquids can be directly metered into the extruder by positive displacement pump.
