Blend Foams Research Articles

Producing Microporous PMMA with Supercritical CO<sub>2</sub> and the Research on its Properties

The research on microcellular polymer foam (MPF) is significant in plastic processing industry. In this study, polymethyl methacrylate (PMMA) was considered to be the foam matrix via a preliminary experiment. It is because that compared with other polymers, it is easier to swell and plasticize with supercritical CO2 (SCCO2). Moreover, its absorbability in SCCO2 is much higher. The above research provides guidance for the preparation of microcellular polymer blend foams. In order to study the foam process and the optimum experimental conditions, the average cellular sizes were measured by controlling the saturation pressure, temperature and the soak time on the basis of the orthogonal experiment. The microporous structure was observed by scanning electron microscope (SEM). Then the optimum amount of nano-fillers was achieved by solution and melt blending. In addition, the mechanical properties of MPF were measured to explore the change in foaming. The obtained results would provide better insight to planners and operators in the field of chemical engineering to handle the uncertainties effectively.

Preparation of radiation crosslinked foams from low‐density polyethylene/ethylene‐vinyl acetate (LDPE/EVA) copolymer blend with a supercritical carbon dioxide approach

AbstractLow‐density polyethylene/ethylene‐vinyl acetate copolymer (LDPE/EVA) blend foams were prepared by a combination of radiation and supercritical carbon dioxide (ScCO2) approach. The radiation effects on LDPE/EVA foams in different ratios were investigated in detail. For the LDPE/EVA blend in a w/w ratio of 70/30, the cell size decreased and the cell density increased with an increase of absorbed dose. The optimal dose and EVA content for the foaming of LDPE/EVA blend in ScCO2 was found to be 50 kGy and 30%, respectively. It was also found that the radiation crosslinked LDPE/EVA blends had a wider foaming temperature range than uncrosslinked samples. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation and foaming extrusion behavior of polylactide acid/polybutylene succinate/montmorillonoid nanocomposite

Polylactic acid (PLA)/polybutylene succinate (PBS) and the PLA/PBS/montmorillonite (MMT) composites were prepared by melt extrusion. The morphology structure, mechanical, thermal, and dynamic rheological properties of the composites were characterized, as well as foaming extrusion behavior of the composites was also studied. The results showed that MMT particles were intercalated into the PLA/PBS matrix forming an ‘intercalation’ structure. The toughness of PLA could be improved by blending with PBS. The comprehensive evaluation of mechanical properties of PLA/PBS was further improved by adding MMT. MMT could play the role of heterogeneous nucleation to improve the crystallization effect of PLA/PBS composite. The melt strength of PLA could be significantly increased by the synergies of MMT and PBS. Meanwhile, MMT could act as a compatibilizer to enhance the interfacial interaction between PLA and PBS. The synergies of PBS and MMT effectively reduced the density of PLA blend foam products, and increased their cell density, uniformity of cell size, and shape distribution.

Characterization of Polyvinyl acetate/Epoxy Blend Foam

Synthesis of polyvinyl acetate-epoxy blend by mixing of 40% PVA to Epoxy by weight and foaming by high rate of air were furthermore carried out to achieve light weight blend foam. It was found that; 5KGy irradiation dose by using Gamma irradiation was enough to attain finally compatiblization. Mechanical properties were studied using hardness tester, while surface morphology was studied as well by measuring scan electron microscope (SEM). Immersing the foam to serial dilution of different acids, alkalis and salts solution for different times was performed. Thermal behavior was discussed by measuring thermal gravimetric analysis (TGA). Investigation of electrical conductivity (Dc) for the soaked foam showed that; conductivity of acids up taken foam is more than alkali while salts is the least. Electrical conductivity of the acids soaked foam were arranged by the following: H3PO4 > H2SO4 > HCl > Citric acid, while alkalis soaked foam was as the following manner: KOH > NaOH >LiOH > Glycerin. Maximum electrical conductivity (9.63 x 10-2 Simon/cm) was achieved by 2N of H3PO4. Heating of glycerin soaked foam raise the electrical conductivity to 8.8 x10-3 Simon/cm. While electrical conductivity of salts solutions swelled foam were as the following: CaCl2 > KCl > NaCl.

Trapping of Alpha Particles and Radon using Epoxy/Poly Vinyl Acetate Blend Foam

Intelligent foam has been achieved by blending epoxy and poly vinyl acetate (PVA) with different ratios, foaming with nitrogen gas was further performed. It was found 25 Kilo gray irradiation electron beam obtained from accelerator was enough for compatibility and modified mechanical behavior. Water uptake to 50% was maintained over night and release was completed after 6 days at 20°C. Thermal behavior testing revealed heat resistance up to 200°C. Structure characterization was determined by FTIR spectroscopy while mechanical investigation was applied using hardness tester. The Foam blend was used to trap alpha particles emitted by 239Pu and 241Am. Alpha counts were continuously recorded while water uptake was carried out until count cut off. Medium decontamination from radon was tracked via water uptaken foam using 773 ppm 226Ra source until count cut. Durability of foam was measured by ten times repeatable water uptakes alpha particles and radon cut off showed no significant difference. Radon associated lead and bismuth were determined in the foam using SSNTD CR39 and a streamer detector and assured by using EDX which proved sorption of radon by specified foam.

Preparation of microcellular polypropylene/polystyrene blend foams with tunable cell structure

AbstractBy using supercritical carbon dioxide (sc‐CO2) as the physical foaming agent, microcellular foaming was carried out in a batch process from a wide range of immiscible polypropylene/polystyrene (PP/PS) blends with 10–70 wt% PS. The blends were prepared via melt processing in a twin‐screw extruder. The cell structure, cell size, and cell density of foamed PP/PS blends were investigated and explained by combining the blend phase morphology and morphological parameters with the foaming principle. It was demonstrated that all PP/PS blends exhibit much dramatically improved foamability than the PP, and significantly decreased cell size and obviously increased cell density than the PS. Moreover, the cell structure can be tunable via changing the blend composition. Foamed PP/PS blends with up to 30 wt% PS exhibit a closed‐cell structure. Among them, foamed PP/PS 90:10 and 80:20 blends have very small mean cell diameter (0.4 and 0.7 µm) and high cell density (8.3 × 1011 and 6.4 × 1011 cells/cm3). Both of blends exhibit nonuniform cell structure, in which most of small cells spread as “a string of beads.” Foamed PP/PS 70:30 blend shows the most uniform cell structure. Increase in the PS content to 50 wt% and especially 70 wt% transforms it to an irregular open‐cell structure. The cell structure of foamed PP/PS blends is strongly related to the blend phase morphology and the solubility of CO2 in PP more than that in PS, which makes the PP serve as a CO2 reservoir. Copyright © 2009 John Wiley & Sons, Ltd.

Fabrication of Fine-celled PP/Ground Tire Rubber Powder Composites Using Supercritical Carbon Dioxide

PP/Ground Rubber Tire (GRT) powder microcellular blend foams were prepared by supercritical carbon dioxide. The effects of blend composition like the content of GRT and maleic anhydride-grafted polypropylene (PP-g-MA) on crystallinity, solubility, diffusivity, morphology and mechanical properties of PP/GRT microcellular composites were studied. The results showed that the PP/GRT composite foams with a unique bimodal (large and small) cellular structure, in which the large-cells embrace a GRT powder. Depending on the composition, generally, the higher content of GRT results in the smaller cell sizes, higher cell densities and relative densities, whereas the 20 wt% GRT composite shows the lowest relative density. The mechanical properties of the microcellular PP/GRT composite foams are directly related to the blend composition and the processing conditions. The PP-g-MA/GRT (50/50) produced microcellular foams with a very fine and uniform cell structure, lower relative densities and improved mechanical properties.

Batch Foam Processing of Polypropylene/Polydimethylsiloxane Blends

Batch foaming processes were employed to prepare plastic foams from polypropylene (PP)/polydimethylsiloxane (PDMS) blends. Various amounts of PDMS were added to a PP matrix, and the resulting blends were batch foamed at different saturation pressures using carbon dioxide (CO2) as the blowing agent. Ultimately, the blend foams exhibited better cell morphologies and higher cell densities in comparison with those prepared from PP alone. The increased solubility of CO2 in PDMS made it as a CO2 reservoir to induce more nucleation. When the PDMS content exceeded a certain level, however, it exerted a negative influence on cell density. Moreover, as the saturation pressure was raised, the cell density of the blend foams increased significantly. It was also noted that the addition of PDMS to the PP matrix generated some very small cells in the larger cell walls.

Preparation, characterization, and foaming behavior of poly(lactic acid)/poly(butylene adipate‐co‐butylene terephthalate) blend

AbstractIn resent years, poly(lactic acid) (PLA) foams have been studied to replace traditional polymer foams in packaging field. Unfortunately, the foaming rate of PLA is low due to its low viscosity and elasticity. To overcome these shortcomings, a biodegradable polyester, poly(butylene adipate‐co‐terephthalate) (PBAT) was blended with PLA to improve melt properties of PLA. Additionally, maleic anhydride (MAH) and 2,5‐dimethyl‐2,5‐di‐(tert‐butylperoxy)hexane (L101) were added to improve the compatibility of PLA with PBAT. The blends were extruded into foams using a twin‐screw extruder. The properties of extrudates were characterized by FTIR, DSC, ARES Rheometer, and SEM. The results show that complex viscosity of PLA/PBAT blend increases by nearly 100% compared with pure PLA. Meanwhile, cell structure of foamed PLA/PBAT blend is much larger and the distribution of cells is more homogenous. The foaming rate of PLA/PBAT blend foams is raised by nearly 50% than that of pure PLA foams. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Nanoscale Cellular Foams from a Poly(propylene)‐Rubber Blend

AbstractPlastic foams with nano/micro‐scale cellular structures were prepared from poly(propylene)/thermoplastic polystyrene elastomer (PP/TPS) systems, specifically the copolymer blends PP/hydrogenated polystyrene‐block‐polybutadiene‐block‐polystyrene rubber and PP/hydrogenated polystyrene‐block‐polyisoprene‐block‐polystyrene. These PP/TPS systems have the unique characteristic that the elastomer domain can be highly dispersed and oriented in the machine direction by changing the draw‐down ratio in the extrusion process. A temperature‐quench batch physical foaming method was used to foam these two systems with CO2. The cell size and location were highly controlled in the dispersed elastomer domains by exploiting the differences in CO2 solubility, diffusivity, and viscoelasticity between the elastomer domains and the PP matrix. The average cell diameter of the PP/TPS blend foams was controlled to be 200–400 nm on the finest level by manipulating the PP/rubber ratio, the draw‐down ratio of extrusion and the foaming temperature. Furthermore, the cellular structure could be highly oriented in one direction by using the highly‐oriented elastomer domains in the polymer blend morphology as a template for foaming.magnified image

Foaming behavior of polypropylene/polystyrene blends enhanced by improved interfacial compatibility

AbstractA series of polypropylene (PP)/polystyrene (PS) blends were prepared by solvent blending with PS‐grafted PP copolymers (PP‐g‐PS) having different PS graft chain length as compatibilizers. The interfacial compatibility was significantly improved with increasing PS graft chain length until the interface was saturated at PS graft chain length being 3.29 × 103 g/mol. The blends were foamed by using pressure‐quenching process and supercritical CO2 as the blowing agent. The cell preferentially formed at compatibilized interface because of low energy barrier for nucleation. Combining with the increased interfacial area, the compatibilized interface lead to the foams with increased cell density compared to the uncompatibilized one. The increase in interfacial compatibility also decreased the escape of gas, held more gas for cell growth, and facilitated the increase in expansion ratio of PP/PS blend foams. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1641–1651, 2008

Control of Bubble Size and Location in Nano‐/Microscale Cellular Poly(propylene)/Rubber Blend Foams

AbstractPlastic foam with nano‐/micro‐scale cellular structures was prepared from a poly(propylene) (PP)/propylene‐ethylene copolymer (PER) blend by controlling bubble nucleation sites and bubble growth in disperse PER domains. Batch foaming experiments using a CO2 pressure quench method were conducted at room temperature. The bubble size and location were highly controlled in disperse PER domains by exploiting the differences in CO2 solubility and viscoelasticity between the PER domains and the PP matrix. The average cell diameter of PP/PER blend foams can be controlled within 0.5–2 µm by the PP/PER ratio, depressurization rate, and foaming temperature.magnified image

Effects of local strain rate and micro-porous morphology on tensile mechanical properties in PP/EPR blend syntactic foams

This study characterizes the effects of local strain rate and micro-porous shape on the tensile mechanical properties at the intermediate and high strain rates in the thermoplastic polymer syntactic foams. Four types of syntactic polypropylene (PP)/ethylene propylene rubber (EPR) blend foams are developed with respect to the micro-porous morphologies. Tensile tests are conducted at the nominal strain rates from 0.3 to 100 s −1. Finite element (FE) models are constructed based on the morphological pictures. The corresponding tensile test simulation is conducted on the microstructural FE models to estimate the local strain rate and investigate the relation between the micro-porous morphology and the local strain rate. It is found that the local strain-rate distribution gets broader in the spherical-shape porous foams than the elliptical-shape porous foams. The strain-rate dependencies of the apparent elastic modulus and the yield stress of the syntactic foams are mainly caused by the matrix material's properties. The magnitude of the yield stress is dependent on the micro-porous shape although that of the apparent elastic modulus is not influenced by the porous morphology. When the local strain rate is taken into account, the yield stress can be predicted by the simple rule of mixture in the spherical shape of the syntactic foams.

Nanocellular Foams of PS/PMMA Polymer Blends

AbstractA nanocellular PS/PMMA polymer blend foam was prepared, where bubble nucleation was localized in the PMMA domains. The blend, which contains dispersed nanoscale PMMA islands, was prepared by polymerizing MMA monomers in a PS matrix to form highly dispersed PMMA domains in the PS matrix by diffusion mixing. The resulting blend was foamed with CO2 at room temperature. A higher depressurization rate at lower foaming temperature made the bubble diameter smaller and the bubble density larger, and a higher PS composition in the blend resulted in a larger bubble density. A void with 40–50 nm in average diameter and a pore density of 8.5 × 1014 cm−3 was obtained as for the finest nanocellular foams.magnified image

Preparation and properties of chitosan/poly(vinyl alcohol) blend foams for copper adsorption

AbstractA new form of polymer blend, macroporous chitosan/poly(vinyl alcohol) (PVA) foams made by a starch expansion process, exhibits the functionalities of chitosan while avoiding its poor mechanical properties and chemical instabilities. The appropriate conditions for foaming are discussed using both insoluble and water‐soluble chitosan. The chitosan/PVA foams demonstrated interconnected and open‐cell structures with large pore size from tens to hundreds of micrometers and high porosities from 73.6 to 84.3%. Glutaraldehyde was employed to improve the retention of chitosan and copper adsorption of the chitosan/PVA foams. While it increased the retention of chitosan and the adsorption capacities, glutaraldehyde decreased the pore size and porosity. The macroporous structure of the chitosan/PVA foams indicates extensive application prospects in terms of the considerable adsorption of heavy metal ions. Copyright © 2006 Society of Chemical Industry

Acoustics and Forming of Novel Polyolefin Blend Foams

Novel acoustical materials have been developed for sound absorption and insulation. The materials are macrocellular thermoplastic foams made from blends of polyethylene and polypropylene. The closed cell foams exhibit good acoustic performance over a broad frequency range and are especially effective at low frequencies. The foams are able to withstand high service temperature environments in industrial applications. Other advantages, relative to conventional acoustic media, include resilience, structural integrity, ease of fabrication, moisture resistance and recyclability. Techniques to improve the acoustical performance by profiling the foam with Helmholtz resonators and quarter wave attenuators are discussed. Forming is the shaping of thermoplastic foams by the application of heat and pressure. This process is used to make acoustic parts with the desired shape and size for space constrained applications such as appliance and automotive. This process can also be used to modify the skin quality and surface aesthetics of the foam. Studies were conducted in laboratory scale equipment to determine the process conditions for forming polyolefin foam and to evaluate the effect on cell structure, foam properties and acoustics. Techniques to preserve the acoustical performance of the foam during the forming process are reviewed.

Effect of addition of EVA on the technical properties of extruded foam profiles of low-density polyethylene/EVA blends

Some technical properties (static mechanical properties, dynamic mechanical properties, creep-recovery behavior, thermal expansion, and thermal conductivity) of low-density foams (50 kg/m3) made of blends of low-density polyethylene (LDPE) and the ethylene vinyl acetate copolymer (EVA) were studied as a function of the EVA proportion in the blends. These properties were compared with those of a foam made of a blend of EVA and ethylene propylene rubber (EPR). The knowledge of how the EVA proportion influences the behavior of these blend foam materials is a fundamental factor in order to obtain a wide range of polyolefin foams, with similar density, suitable for different applications. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1237–1244, 1998

Effect of addition of EVA on the technical properties of extruded foam profiles of low‐density polyethylene/EVA blends

Some technical properties (static mechanical properties, dynamic mechanical properties, creep-recovery behavior, thermal expansion, and thermal conductivity) of low-density foams (50 kg/m3) made of blends of low-density polyethylene (LDPE) and the ethylene vinyl acetate copolymer (EVA) were studied as a function of the EVA proportion in the blends. These properties were compared with those of a foam made of a blend of EVA and ethylene propylene rubber (EPR). The knowledge of how the EVA proportion influences the behavior of these blend foam materials is a fundamental factor in order to obtain a wide range of polyolefin foams, with similar density, suitable for different applications. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1237–1244, 1998

Biological recycling of plastics containing ester bonds

AbstractBiodegradable blend plastics such as polycaprolactone (PCL)‐conventional plastics blends, PCL‐polystyrene blend foams, PCL‐poly‐3‐hydroxybutyrate (PHB) blends, PCL‐raw cornstarch (CS) blends and PCL‐CaCO3 blends were developed. It was suggested that the thermophilic composting of biodegradable plastics containing PCL was one of powerful technologies for recycling of biodegradable plastics. Furthermore, we tried to get useful products from biodegradable plastics by microbial fermentation processes. Polypropylene (PP)‐CS blend and PCL‐CS blend plastics were aerobically converted into ethanol by Bacillus polymyxa. PHB and PP‐CS blend and PCL‐CS blend plastics were anaerobically converted into some organic acids and methane gas by mixed microbial cultures with a methanogenic bacterium.

A Study of Poly(vinyl Chloride) Blend Foams for the Insulation of Space Cryogenic Tanks-Preparation and Characterization

A Study of Poly(vinyl Chloride) Blend Foams for the Insulation of Space Cryogenic Tanks-Preparation and Characterization