Fabrication of Triblock Elastomer Foams and Gelation Studies for Oil Spill Remediation

Polymeric foamed materials are among the most widely utilized technologies for oil spill accidents and releases of oil-contaminated wastewater oil due to their porosity to absorb and separate oil/water effectively. However, a major limitation of traditional polymeric foams is their reliance on an ad/absorption mechanism as the sole method of oil capture, leading to potential oil leakage once their saturation point is exceeded. Tri-block polymer styrene-ethylene-butylene-styrene (SEBS) is a fascinating absorbent material that can bypass this limitation by both capturing oil and providing a sealing mechanism via gelation to prevent oil leakage due to its unique chemical structure. SEBS foams are produced via simultaneous crosslinking and foaming that results in an impressive expansion ratio of up to 15.2 with over 93% porosity. Most importantly, the SEBS foams show great potential as oil absorbents in spill remediation, demonstrating rapid and efficient oil absorption coupled with superhydrophobic properties. Moreover, the unique interaction between the oil and SEBS enables the formation of a physical gel, acting as an effective barrier against oil leakage. These findings indicate the potential for commercializing SEBS foam as a viable option for geotextiles to mitigate oil spill concerns from infrastructures.

Study on Chain Extension Blending Modification and Foaming Behavior of Thermoplastic Polyamide Elastomer

In order to improve the melt foaming properties of thermoplastic polyamide elastomers and reduce the shrinkage rate of foamed materials, acid anhydride chain extenders SMA (styrene maleic anhydride copolymer) are used in this paper to in situ reactive blending thermoplastic polyamide elastomers (TPAE) and polyamide 6 (PA6). The rheological and crystalline properties of the modified samples were characterized by a rotational rheometer and differential scanning calorimeter, and the melt batch foaming experiment with CO₂ as the foaming agent was carried out. The results showed that the melting enthalpy of modified TPAE reduced with the addition of content of PA6, which implied that the crystallinity of the hard phase of the system was depressed. Nevertheless, the reduction of crystallinity was beneficial to improve the penetration of gas and reduce the effect of the pressure difference inside and outside the cell on foam shrinkage. Additionally, the microcross-linked structure formed with the increase of PA6 content enhanced the storage modulus of modified TPAE, which could accelerate recovery of strain. The foaming temperature zone and recovery performance of all modified TPAE samples were significantly improved. The overall shrinkage rate was reduced to less than 10%, the maximum expansion ratio could reach 11-13 times with a more complete and uniform cell structure, and the resilience was improved by about 12%.

SEBS as an Effective Nucleating Agent for Polystyrene Foams

Different percentages of an elastomeric phase of styrene-ethylene-butylene-styrene (SEBS) were added to a polystyrene (PS) matrix to evaluate its nucleating effect in PS foams. It has been demonstrated that a minimum quantity of SEBS produces a high nucleation effect on the cellular materials that are produced. In particular, the results show that by adding 2% of SEBS, it is possible to reduce the cell size by 10 times while maintaining the density and open cell content of the foamed materials. The influence of this polymeric phase on the glass transition temperature (Tg) and the shear and extensional rheological properties has been studied to understand the foaming behavior. The results indicate a slight increase in the Tg and a decrease of the shear viscosity, extensional viscosity, and strain hardening coefficient as the percentage of SEBS increases. Consequently, an increase in the density and a deterioration of the cellular structure is detected for SEBS amounts higher than 3%.

Production and characterization of thermoplastic elastomer foams based on the styrene–ethylene–butylene–styrene (SEBS) rubber and thermoplastic material

Thermoplastic elastomer foams based on styrene–ethylene–butylene–styrene (SEBS)/polypropylene (PP) were produced by using different processing techniques such as extrusion and injection molding to achieve optimized mechanical and thermal properties in terms of strength, elongation, and damping capability. Foaming is a method of introducing gas-filled cells into the material and it is considered an effective way to meet the requirements for higher impact resistance with low density and relatively low hardness. In this study, microspheres were used as a foaming agent and were introduced to the system by using an injection molding machine. They were used in different percentages and ranged from 1 and 3%. They decrease the density of the product thereby lowering the weight and cost. Besides improving damping abilities and decreasing the density, inorganic fillers such as talc, silica, and calcium carbonate were used to increase the mechanical strength, and their effectivity was also investigated. It was observed that a higher amount of foaming agent lowered the density by creating voids in the blend, as expected. The introduction of fillers increases the mechanical properties; however, the density had a negative effect even in the presence of foaming agents. About 3% density reduction can be achieved in the presence of talc and a foaming agent whereas the other fillers had an opposite effect on the density. Accordingly, the impact resistance was affected negatively because of the stiffness of the filler materials, and the highest Izod impact value was 50.2 kJ/m2. The elastic modulus values for foamed samples and filled with CaCO3, talc, and silica were 808, 681, and 552 MPa respectively. Combining foaming and thermoplastic elastomers (TPEs) offers a wide variety of possibilities to new and existing applications. In addition to low hardness and density, foaming provides better damping ability thanks to its morphological structure.

Universal Strain Energy-Mediated Dynamic Porosity in Physically Networked Elastomers and Their Applications

Mechanical and physical properties of porous polymers are highly dependent on the arrangement of their internal pores, which once synthesized are widely considered static. However, here we introduce an unconventional dynamic porosity strategy in physically networked elastomer polymers, irrespective of their chemistry. This strategy allows for an omnidirectional and reversible reconfiguration of porosity in response to applied mechanical deformations, even at ambient conditions. In particular, the normal contact pressure between human fingers (just 0.62 MPa) applied on thin elastomer films results in a permanent reversion of the pores to a denser and more solid state. The porous-to-solid transition leads to a 3 order of magnitude reduction in pore density and up to a 22% relative volumetric shrinkage of the films, resulting in an opaque-to-transparent transition (OTT) that acts as a visual indication of porosity state (porous vs nonporous). It is shown that the pore reversion pressure onset is dependent on the average pore-to-pore distance that is controllable through process-specific parameters. Furthermore, the porosity transition is reversible for multiple cycles when the through-plane compression activation is coupled with an in-plane stretch (ε = 700%). A strain energy-mediated thermodynamic model is successfully implemented to confirm the effects of mechanical deformations on pore reversion and generation. Finally, applications of the newfound dynamic porosity concept are exploited for pressure indication, on-demand modulation of materials' mechanical and thermal characteristics, and flexible photomasks.

Microcellular morphology evolution of polystyrene/thermoplastic polyurethane blends in the presence of supercritical CO2

In this article, a facile melt blending and solid batch foaming approach was proposed to prepare microcellular polystyrene/thermoplastic polyurethane (PS/TPU) blending foams with supercritical carbon dioxide (CO2). Compared with those of pure PS and pure TPU, an interesting phenomenon about the enhanced complex viscosity and storage modulus, as well as decreased loss factor of PS/TPU blends, was found. The solubility of CO2 in the PS/TPU blends was enhanced, owing to the CO2 solubilization effects of TPU. An interesting bimodal cell structure (BCS) was observed in the PS/TPU blending foams with the TPU content of 10, 15, and 20%. Consequently, a significant conclusion could be speculated that the generation of BCS in the PS/TPU blending system depended on not only the viscosity and morphology of the polymer blends but also the solubility and diffusivity of the CO2 as well as the type of cell nucleation. The thermal insulation property of PS foam was improved by the introduction of TPU.

Microstructure Development and Its Influence on the Properties of Styrene-Ethylene-Butylene-Styrene/Polystyrene Blends

The present work is a novel attempt to understand the microstructure of styrene-ethylene-butylene-styrene (SEBS)/polystyrene (PS) blends not only through morphological studies, but also thermal, mechanical and rheological characterizations. SEBS/PS blends containing 10, 30 and 50 wt % PS were processed in a micro-compounder and characterized. Scanning electron microscopy (SEM) studies, with selective staining of the PS phase, revealed the presence of PS as nanometer-sized domains, as well as phase-separated micrometer-sized aggregates. Blends with 30 and 50 wt % PS exhibited a fibrillar microstructure, obeying Hirsch's model of short fiber composites. A remarkable increase in glass transition temperature indicated a strong interaction of the fibrils with SEBS. All blends showed two modes of relaxation corresponding to the two phases. A single mode of relaxation of the PS phase has been attributed to combined effects of the partial miscibility of the added PS, along with the interaction of the fibrils with SEBS. The long relaxation time of the elastomeric phase indicated the tendency of these materials to undergo time-dependent shrinkage in secondary processing operations. An increase in PS content resulted in the lowering of the shear viscosity and energy requirement for mixing, indicating the ease of processing.

Investigations on Blending and Foaming Behavior of Styrene-Ethylene-Butylene-Styrene/Polystyrene Blends

The interplay of screw speed and residence time during polymer blend extrusion profoundly influences blend properties. Herein, blends of styrene-ethylene-butylene-styrene (SEBS) and polystyrene (PS) containing 30% by weight PS were prepared at a constant feed rate but different screw speeds (50, 100, 200 and 300 min−1). The blend produced at 100 min−1 (B100) possessed a finer morphology, better mechanical and rheological properties, attributed to suitability of residence time and viscosity ratio. When batch foamed with carbon dioxide at 110°C and 100°C, all blends produced stable foams. B100 foams exhibited higher volume expansion ratio (VE) due to higher complex viscosity and storage modulus. When foaming was conducted at 35°C, all foams shrank. B100 foams possessed higher cell density, lower VE and showed faster shrinkage due to increased nucleation and hindered expansion by the finely dispersed stiff PS aggregates during selective foaming of the elastomeric phase.

Fine dispersion morphology of polystyrene/poly(ethylene terephthalate glycol) blending generation for controlled foaming behavior

Polystyrene/poly(ethylene terephthalate glycol) (PS/PETG) blends with different PETG contents were prepared using a Haake internal mixer at 190 °C.

Dynamic rheology and foaming behaviour of styrene–ethylene–butylene–styrene/ polystyrene blends

Styrene–ethylene–butylene–styrene and its blends containing 10, 30 and 50 wt% polystyrene were subjected to batch foaming using physical blowing agent carbon dioxide. At higher foaming temperatures (80–110℃), complex viscosity ( η*) and storage modulus ( E′) were found to control the volume expansion ratio and the shrinkage of foams. For a given composition, optimal volume expansion was achieved at temperatures close to the glass transition temperature ( T g) of the polystyrene phase of that composition, indicating the presence of a complex viscosity window favourable for the foaming process. Blends with 30% and 50% polystyrene content possessed higher values of E′ and η*, and produced stable foams having higher volume expansion ratio, when foamed within their respective η* windows. At a much lower foaming temperature (35℃), polystyrene was found to have a nucleating effect. However, irrespective of rheological properties, all foams showed prominent shrinkage. A higher polystyrene content resulted in a lower volume expansion ratio, as well as shrinkage over a shorter period of time and a greater extent of shrinkage in the same time span. This can be attributed to the selective foaming of the ethylene–butylene phase, hindered by the stiff polystyrene aggregates.