Structure, physical properties, and flame retardancy of POE/NR/EG blend foams: Effect of crosslinking

Abstract

<jats:p>Elastomeric foams were produced by melt-mixing of polyethylene-octene elastomer (POE), natural rubber (NR), and expandable graphite (EG) in an internal mixer. The blend was later foamed by compression-molding method. EG was used as a filler to enhance flame retardancy of the blend foams. Dicumyl peroxide (DCP) was used as curative to crosslink the blend foams. The influence of DCP content (0.5, 0.7, 0.9, and 1.0 part(s) by weight, pbw) on rheological properties, structure, density, mechanical properties, thermal conductivity, and flame retardancy of the POE/NR/EG blend foams was investigated. The rheological analysis showed that the melt strength/viscosity of the POE/NR/EG blend foams increased with more DCP addition due to promoted crosslinking in the blend foams. The cellular structural observation by SEM technique revealed that the POE/NR/EG blend foams had close-cell structure. Increasing DCP content, the blend foams had smaller cell and narrower cell size distribution. The degree of porosity, however, was highest for the foamed blends added with 0.7 pbw DCP, which brought about the lowest thermal conductivity. Furthermore, it was found that the density, tensile strength, elastomeric recovery, and compressive strength increased with increasing content of DCP, but the elongation at break decreased. The POE/NR/EG blend foams reached the horizontal burning level of HF-1, and their oxygen index increased in accordance with an increase of DCP content. The results indicated that an appropriate use of DCP was critical for the crosslinked POE/NR/EG blend foams with optimum cellular structure, providing the best improvement in thermal insulation properties and good flame retardancy. </jats:p>

Microbubble technology for natural rubber latex foam production: The use of various gas-filled microbubbles

“…Generally, the performance of polymeric foams can be evaluated by many structural parameters such as cell size, cell size distribution, and cell density. 13 Figure 2 shows macroscopic cross-section views, SEM images, and cell size distribution of the NRLFs produced from air (AF), nitrogen (NF), and argon (ArF). The cross-section photographs demonstrated clearly a uniform distribution of cell size for all the bubbled foams.…”

“…The finer cells led to the higher density of the foam. This is because a rubber foam with small cell sizes offers thicker cell walls 13,20,21 and higher number of cells per unit volume, and thus more rubber matrix per unit volume. Figure 3(b) demonstrates that all foams offered the compression set values within the standard (less than 6%); 4.52, 3.83, and 2.99% for the AF, NF, and ArF, respectively.…”