Towards novel super‐elastic foams based on isoperene rubber: Preparation and characterization

Abstract

A novel and conventional closed cell polyisoprene rubber (IR) foams were produced by a single step limited-expansion and two step unlimited-expansion foaming process, respectively. The effect of 3 to 12 part per hundred rubber (phr) of azodicarbonamide (ADC) foaming agent on their structure and properties of developed novel foams were studied. In developed novel foams, the density was strangely independent of ADC content; however, the cell sizes conversely related to ADC content and it decreased by 60% (555-330 μm) and the internal cell pressure build up from 1 to 3.7 atm, which was related to pressure-free foaming method. The both reasons of compressed gas trapped inside cells and constant density not only caused unique enhancement in novel foams mechanical properties as hardness and modulus but also improved their dynamic properties as hysteresis and elasticity. Results of conventional IR foams showed that, their foam density as well as dynamic and mechanical properties sharply decreased with increasing ADC content from 3 to 12 phr. For clear expression, in samples with 12 phr of ADC, novel developed foams have more foam density (180%), more hardness (240%), more modulus (290%), and smaller cell size (75%) than conventional foams.Finally, novel developed foams were super-elastic material with no hysteresis and no plastic deformation while conventional foams had 40% hysteresis and 10% plastic deformation under the same compression conditions. K E Y W O R D S cellular morphology, mechanical properties, polyisoprene rubber, polymer foam, super-elastic materials

Chemistry, Processing, Properties, and Applications of Rubber Foams

“…For a CFA, the compound (matrix mixed with the foaming agent) is placed in a mold and compressed (electrically heated compression molding press) at a fixed temperature and pressure for a specific time. Mold opening releases the pressure and cooled down to room temperature to fix the cell structure [ 219 ].…”

Evaluation of azodicarbonamide (ADC) on density, expansion ratio and closed cell properties of natural rubber foam

“…Thus, the full vulcanization process results in high density, leading to small amounts of cells and lower foam expansion (higher foam density). Based on research reported by Vahidifar, 2020 [15], that more homogeneous structure consisting of smaller cells has a higher density foam.…”

Real 3D Structure-Based Finite Element Simulation of Elastomer Foams: Effect of the Foaming Agent Content

“…In both processes, the parameters including temperature and intracellular pressure play critically important roles during foaming, directly affecting the final properties of the foam. The processing methodology for rubber foams can be found in our previous works. − …”

“…In addition, the FA type and content are of great importance in controlling the intracellular pressure and local temperature profile of the rubber foams, where the latter is dependent on the endothermic or exothermic decomposition of a chemical blowing agent. The other important factor which should be considered in the temperature profile is the heat of reaction associated with the chemical reactions involved in the rubber curing step. ,, Najib et al employed 4–12 phr of sodium bicarbonate as an endothermic chemical FA in natural rubber (NR). They reported that the incorporation of a higher FA concentration decreased the foam density (257–239 kg/cm 3 ) and cell size while increasing the cell density and homogeneity of the foam structure .…”

“…The preparation and characterization of NR foams were reported in our group’s previous work. − ,, Our recent study, pioneer research on using real three-dimensional (3D) morphology to simulate closed-cell rubber foams, focused on the simulation and experimental measurements of NR foams having different foam densities. The NR foams were prepared from the same formulation but had different relative foam densities (0.3–0.5).…”