Recent Trends of Foaming in Polymer Processing: A Review

Abstract

Polymer foams have low density, good heat insulation, good sound insulation effects, high specific strength, and high corrosion resistance, and are widely used in civil and industrial applications. In this paper, the classification of polymer foams, principles of the foaming process, types of blowing agents, and raw materials of polymer foams are reviewed. The research progress of various foaming methods and the current problems and possible solutions are discussed in detail.

Closed Cell Rigid Polyurethane Foams Based on Low Functionality Polyols: Research of Dimensional Stability and Standardised Performance Properties

“…Table 2 shows that the compositions use different water/Solkane 365 mfc ratios for these blowing agents, i.e., 2.1/20, 2.4/25, 2.0/15, 2.5/29, 3.0/25, and 3.5/18. A review of the literature has shown that the apparent density of the product decreases with increasing blowing agent content [37,38], but with 30 kg/m 3 foams, the apparent density decreases with decreasing content of the Solkane 365 mfc in water/Solkane 365 mfc compositions of 3.0/25 and 3.5/18. A similar trend is observed in foams with an apparent density of 40 kg/m 3 .…”

Cellulose Acetate and Supercritical Carbon Dioxide: Membranes, Nanoparticles, Microparticles and Nanostructured Filaments

“…• the spray drying process is characterized by variations in particle shape and particle size distribution, high process temperatures, and high drying speeds that normally do not allow the encapsulation of temperature-sensitive bioactive substances [6]; • the electrospinning process is characterized by the use of organic solvents that can be toxic, difficulty in obtaining 3-D structures as well as sufficient size of pores needed for biomedical applications and suitable mechanical behavior; moreover, the process depends on a high number of variables and their combination (humidity, temperatures, collector distance, high voltage, etc.) [7]; • the chemical foaming process is simple, but high mold manufacturing precision is required (the mold cost is high), and a second clamping pressure device is needed during high-pressure foaming process [8]; • the gel drying process is characterized by a high cost of the raw materials (the chemicals) and there is often a large volume shrinkage and cracking during the drying step (the removing of the "organics" can cause the collapse of the structure due to their surface tension); moreover, long processing times can be necessary [9]; • the phase inversion process is characterized by the use of organic solvents and necessity of post-treatments on the generated material, low versatility (once the system polymersolvent-nonsolvent is selected, only one kind of morphology is possible), long processing times (from several hours to days), etc. [5].…”

Reduction of time‐releasing ammonia from polymer foam using low acidic polymers

“…The polymer foams can be found in the everywhere such as in products of building materials, automotive interiors, shoes, wallpaper, and mats. [ 1–4 ] The chemical blowing agents that decompose into gases making air bubbles in the polymer matrix are widely used in the foaming process, because the chemical blowing agents reduce the weight of solid foams in addition to improve the electrical and sound insulation properties. Among various organic and inorganic chemical blowing agents, the azodicarbonamide (ADCA) is the most widely used one because of the cheap price and good flame retardant besides the high volume of gas generation in the foaming process.…”

“…Among various organic and inorganic chemical blowing agents, the azodicarbonamide (ADCA) is the most widely used one because of the cheap price and good flame retardant besides the high volume of gas generation in the foaming process. [ 2–5 ] During the foaming process developing the cell structures inside the polymer matrix, the ADCA is decomposed into nitrogen, carbon monoxide, carbon dioxide, water, and ammonia (NH 3 ) (Figure 1). [ 6–7 ] However, it is known that the polymer foams release various gases including ammonia gas for a long‐time depending on the environmental conditions, in which the gases directly occur from the foam itself or leak from the pores developed during the foaming process.…”