Effect of the pressure drop rate on cell nucleation in continuous processing of microcellular polymers

Abstract

Microllular plastics are cellular polymers characterized by cell densities greater than 109 cells/cm3 and cells smaller than 10 μm. One of the critical steps in the continuous production of microcellular plastics is the promotion of high cell nucleation rates in a flowing polymer matrix. These high nucleation rates can be achieved by first forming a polymer/gas solution followed by rapidly decreasing the solubility of gas in the polymer. Since, in the processing range of interest, the gas solubility in the polymer decreases as the pressure decreases, a rapid pressure drop element, consisting of a nozzle, has been employed as a continuous microcellular nucleation device. In this paper, the effects of the pressure drop rate on the nucleation of cells and the cell density are discussed. The experimental results indicate that both the magnitude and the cell density are discussed. The experimental results indicate that both the magnitude and the rate of pressure drop play a strong role in microcellular processing. The pressure phenomenon affects the thermodynamic instability induced in the polymer/gas solution and the competition between cell nucleation and growth.

Architecture and properties of anisotropic polymer composite scaffolds for bone tissue engineering

“…On the contrary, an increased viscosity will limit pore growth and favour closed pores, therefore decreasing porosity, specific surface, and increasing pore wall thickness. Pore size is related to two main factors [44]. First there is competition between the gas diffusing out of the skin, which is therefore lost for pore growth, and the gas diffusing into nucleated pores.…”

Polymer–Clay Nanocomposite Foams Prepared Using Carbon Dioxide

“…Recently developed microcellular foams provide improved mechanical properties over conventional foams, [3] but they require stringent processing conditions (e.g., very high pressure and pressure drop rate, and processing temperature close to the glass transition temperature). [4,5] This limits the operating window for extrusion and the attainable size of foam products. Addition of a small amount of clay nanoparticles into polymer matrices provides significant improvement in a wide variety of properties.…”

Development of an extrusion system for producing fine‐celled HDPE/wood‐fiber composite foams using CO2 as a blowing agent

“…43 CO 2 has been used to produce fine-celled and microcellular plastics. [44][45][46][47][48][49] However, a PBA has not been used for plastic/WF composite foaming.…”