Foaming of polypropylene with supercritical carbon dioxide: An experimental and theoretical study on a new process

Abstract

A new process was used to foam polypropylene (PP) with batch foaming technique with supercritical carbon dioxide (scCO 2 ) as the blowing agent. Comparing with the conventional process, the new one takes less time to foam and the foaming temperature range is much broader, which is about 2.5 h and 55 C, respectively. An activation model was established on the basis of mass equilibrium, this model was combined with classical nucleation theory and S-L EOS model to explain foaming behaviors of PP and simulate the cell nucleation and cell diameter. A satisfactory agreement between calculated and experimental values was obtained.

Tuning High and Low Temperature Foaming Behavior of Linear and Long-Chain Branched Polypropylene via Partial and Complete Melting

“…Rather, existing studies have relied on melt strength or long-chain branching to generally describe their effects on foaming. Ding et al employed temperature protocols almost identical to those described in the present work to compare the foamability of PP in batch foaming using scCO 2 as the blowing agent [ 30 ]. While they also reported that a broader foaming window was obtained when foaming was initiated on a completely molten PP sample, a saturation time of 2.5 h—compared to 18 min in the present work—was used.…”

“…A common aspect shared by most existing batch foaming studies using scCO 2 is that foaming is initiated under conditions where the polymer is partially molten to determine the optimal foaming behavior, while practical foaming applications involve complete melting of thermoplastics for ease of processability under applied flow, such as in extrusion foaming and foam injection molding. Some batch foaming studies have attempted to explore the sole effect of temperature on foamability by saturating PP at elevated temperatures and cooling to lower temperatures for foaming [ 28 , 29 , 30 , 31 ]; however, gas saturation was performed over several hours, which realistically may lead to crystallization of the polymer matrix prior to foaming, given such prolonged durations. To bridge this gap in understanding the foamability of PP in its partially molten state versus fully amorphous state as a melt, the work presented here aims to investigate the effect of the saturation heating profile on the final foam structure and foaming window while completing gas saturation in the order of minutes.…”

Microcellular injection molding of polypropylene and glass fiber composites with supercritical nitrogen

“…23,24 Furthermore, blending supercritical fluid (SCF) in a polymer melt can effectively reduce the viscosity and glass transition temperature of the polymer melt, as well as the interfacial tension. 25,26 Using microcellular injection molding technology with SCFs, the cell morphology, surface quality and mechanical properties of molded parts can be controlled by the injection molding processing parameters such as blowing gas content, shot size, injection speed, melt and mold temperature, melt pressure, dwell time and so on. [27][28][29][30][31][32] Since the properties of molded polymer composites are affected by the processing conditions and the amount of reinforcement, a finer cell structure, a more uniform cell size distribution and a better reinforcement distribution and orientation can be achieved by controlling the foaming processing conditions.…”

Effects of Foaming Temperature on Super Light Particles of Polypropylene Prepared by Batch Method

“…Micro foam PP has the trend of replacing some other microcellular foams, such as micro foam PS. It is a kind of new environmental protection material, so it has great use value [6].…”