Supercritical CO₂Foaming of Lightweight Polyolefin Elastomer/trans-Polyoctylene Rubber Composite Foams with Extra-Soft and Anti-Shrinkage Performance

Abstract

Lightweight polyolefin elastomer (POE) foams are of great interest in numerous fields. However, POE is difficult to foaming and obtaining the ideal cellular structures before cross-linking. Herein, low-molecular-weight trans-polyoctylene rubber (TOR) with lots of double bonds and low molecular weight was introduced into the POE matrix to improve their vulcanizing and foaming process. Then, a series of lightweight POE/TOR composite foams with adjustable cellular structures and outstanding performance were prepared by supercritical CO 2 foaming. It was worth noting that the gel content and foaming temperature windows were greatly improved under the action of TOR, and a record-breaking density as low as 0.036 g/cm 3 for POE-based composite foams was harvested. In addition, the as-prepared elastomer foams exhibited rapid shrinkage but slow recovery feature due to the diffusivity difference of gas and cross-linking nature of materials, and its recovery ratio could reach 91.3%. More interestingly, the conversion law of the corresponding density change between hard and soft materials was discovered, and extra-soft POE-based composite foams (like Shore C below 10) were obtained, which could be twisted, folded, compressed, stretched, bent, and rolled with ease. Furthermore, the residual strain and hysteresis loss ratio of as-prepared elastomer foams were as low as 1.56 and 12.95%, respectively. These distinct advantages together with the green foaming process make the composite elastomer foams very promising toward high-performance flexible cellular polymeric materials.

Customized Multimodal Cellular Elastomer Foams through Presetting Cells before CO2 Foaming

“…The as-prepared OBC and POBC foams were named as “FOBC- m - z ” and “FPOBC y - t - m - z ” in which “m” is foaming temperature and “z” is foaming pressure. The N 2 -assistant recovery technology was used to facilitate the recovery of the foams. , After 72 h, the foams were used for the following characterization.…”

“…On the one hand, elastomer foams prepared through physical foaming develop later than plastic foams . On another hand, compared with thermoplastic polymers, the foaming of elastomers is more sophisticated due to the high relaxation of molecular chains, low modulus, and low crystallization ability, which will lead to shrinkage after foaming. − With the commercial success of thermoplastic polyurethane (TPU) foams, researchers have paid increased attention to the foaming mechanism, foaming behavior, and performance of elastomer foams. ,− Based on the aforementioned strategies, the introduction of bimodal structures inside elastomers has been proven feasible, and positive results have been obtained. ,, For example, TPU/PDMS foams with bimodal cell structures prepared by Tan et al exhibited outstanding compression properties and sound insulation. Huang et al fabricated a microporous segregated network structure by solution-compression molding two types of TPU, in which the interface was well combined and bimodal cell structure was observed.…”

Preparation of Superelastic, Durable, and Lightweight Composite Foams Based on Multiple Cross-Linked Network Regulated Structures

“…This is a good improvement for the elasticity and recyclability of the EVA foam. However, no matter the polymeric fillers such as rubber introduced in the chemical foaming process or the inorganic fillers or modified fillers introduced in the physical foaming process, there is a lack of effective interactions between the nonpolar rubber and the plastic and a lack of effective chemical reactions to achieve fine regulation of the cell structure . Since the rubber molecular chain is the main binder, the current research on ENA composite foams with rubber as the filler focuses on the effect of different rubber contents on the properties of the composites, mainly on the mechanical and resilience properties.…”

Shrink-Resistant Poly(butylene adipate-co-terephthalate) Foam Reinforced with Crystalline Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Particles

“…In recent years, numerous efforts have been dedicated to improving the dimensional stability of polymer foam, including utilizing mixed gas as blowing agents, , chain extension, , and polymer blending. − For instance, Xu et al employed N 2 and CO 2 as blowing agents for the production of TPEE foams, resulting in a stable ER of 17 and a shrinkage ratio below 20% . However, using mixed gas foaming has difficulties in controlling the gas concentration during the process.…”