Effect Of Foaming Temperature Research Articles

Extrusion Foaming of Poly (lactic acid)/Soy Protein Concentrate Blends

AbstractPoly(lactic acid) (PLA) and soy protein concentrate (SPC) were compounded using poly(2‐ethyl‐2‐oxazoline) as compatibilizer by twin‐screw extrusion, and the resulting blends were foamed by a chemical blowing agent (CBA) using the same extruder. Effects of foaming temperature and CBA content on cell density and foam density were investigated. Polymeric methylene diphenyl diisocyanate (pMDI) as a co‐compatibilizer was added prior to foaming extrusion and its effects on foam morphology and properties were also studied. The results showed that cell density and foam density were greatly influenced by foaming temperature and CBA content. Using the strong interfacial modifier pMDI in PLA/SPC blends resulted in high‐cell density and low‐foam density when CBA concentration was low. magnified image

Preparation of Foam Glass Composite from Iron Ore Tailing

Foam glass composite with good capabilities was prepared from iron ore tailings as the main material by two steps. The phase composition and microstructure were determined by X-ray diffraction and scanning electron microscopy. The effects of foaming temperature and sintering temperature on sample capabilities were studied by determining sample bulk density and compression strength. The results show that the main phase of basis glass powder is amorphous mineral. The foam glass composite with enclosed circle pore mainly concludes Ca[(Fe,Mg)][SiO3]2 and amorphous glass. The diameter size of pore is wide and distributes evenly. The foam glass composite, whose compression strength is 62.25MPa, and bulk density is 2.056 g/cm3, has fine complex capabilities. With the increase of foaming temperature the sample pore diameter size raises, while bulk density and compression strength reduces. The bulk density and compression strength all diminish firstly and raise subsequently with the sintering temperature increasing. The optima temperature parameters are foaming temperature of 900~950 and sinter temperature of 1100 .

Correlation between the acoustic and dynamic mechanical properties of natural rubber foam: Effect of foaming temperature

Acoustic absorbing foam materials are produced from dry natural rubber (NR) with the addition of sodium bicarbonate as a blowing agent. The acoustical efficiencies of NR foams were studied, and the results show a significant influence of the viscoelastic and damping properties of the base matrix. Both of these properties are governed by the average cell size, relative density, crosslink density and number of cells per unit volume. The lowest foaming temperature, 140 °C, yielded the NR foam (NR 140) with the highest relative density, crosslink density, smallest average cell size and greatest number of cells per unit volume. Consequently, these foam cell characteristics resulted in a superior sound absorption coefficient and a high storage modulus, which indicates that the NR 140 foam exhibits a better elastic behavior. On the other hand, the NR foam that expanded at 160 °C (NR 160) exhibited great potential for insulating sound and possessed good damping properties, which was characterized by its high transmission loss and tan δ values.

Foaming characteristics of Al–Si–Mg (LM25) alloy prepared by liquid metal processing

LM25 (Al–Si–Mg) foams were made by melt processing route using Al foam scrap turnings as thickening agent in place of aluminium powder or Ca metal. The effects of foaming temperature and excess Mg content on melt expansion and cell structure were studied. The selection of foaming temperature significantly influenced foam decay. While severe collapse occurred at 670°C, foam decay is hardly observed at 640°C. Moreover, presence of excess Mg (3 wt-%) in this alloy enhanced collapse at 670°C, presumably due to its surface tension lowering effect. Despite foam collapse, a well defined and uniform cell size could be obtained at 670°C as compared to the foams obtained at 640°C. Uniaxial compression tests showed serrated plateau stress–strain behaviour with extensive localised but non-catastrophic damage leading to progressive breaking away of foam pieces. Overall, these experiments showed the potential to manufacture good quality LM25 foam using inexpensive Al foam turnings.

Effect of Foaming Temperature on Pore Morphology of Al/AlN Composite Foam Fabricated by Melt Foaming Method

Al foams whose matrix contains dispersed AlN particles (Al/AlN composite foams) were prepared by a melt foaming method, and the effect of foaming temperature on the pore morphology of the prepared foams was investigated. First, Al/AlN composites were prepared by non-compressive infiltration of Al powder compacts with molten Al alloy in nitrogen atmosphere. Next, the prepared composites were melted by induction heating and foamed at various temperatures using TiH2 powders as blowing agents. The porosity of prepared Al/AlN composite foams slightly decreases with increasing foaming temperature, and the pore morphology of the foam becomes homogeneous simultaneously. When the foaming temperature is 1123 K, homogeneous pores are formed in all over the ingot. This pore homogeneity is probably achieved by the stabilization of the foaming behavior due to the formation of Al3Ti particles in the melt and dispersion of AlN particles.

Foaming experiments on LM25 alloy reinforced with SiC particulates

Al–Si–Mg/SiC P foams were prepared by melt processing route with TiH 2 as the blowing agent. The effects of foaming temperature (640 and 670 °C), SiC P size (12 and 21 μm), and volume % (5–20) on liquid foam expansion and subsequent collapse were studied. Irrespective of the particle size, significant collapse was observed in the liquid foam at 670 °C. At the lower foaming temperature of 640 °C, the liquid foam collapse was low to moderate, with finer and higher (15/20%) contents of SiC p resulting in low collapse and the best overall quality. Preferential segregation of particles to gas/metal interface, postulated by earlier investigators, was not observed in the present case. The presence of SiC within the cell walls induced brittleness, and created irrecoverable damage during the initial phase of compressive deformation. The compressive strength of the foams was lower than theoretical predictions. Minor defects such as porosity, present within the cell walls, might be responsible in lowering of the compressive strength.

Fabrication of Al-3.7 Pct Si-0.18 Pct Mg Foam Strengthened by AlN Particle Dispersion and its Compressive Properties

Al-3.7 pct Si-0.18 pct Mg foams strengthened by AlN particle dispersion were prepared by a melt foaming method, and the effect of foaming temperature on the foaming behavior was investigated. Al-3.7 pct Si-0.18 pct Mg alloy containing AlN particles was prepared by noncompressive infiltration of Al powder compacts with molten Al alloy in nitrogen atmosphere, and it was foamed at different foaming temperatures ranging from 1023 to 1173 K. The porosity of prepared foam decreases and the pore structure becomes homogeneous with increasing foaming temperature. When the foaming temperature is higher than 1123 K, homogeneous pores are formed in the prepared ingot without using oxide particles and metallic calcium granules, which are usually used for stabilizing a foaming process. This stabilization of the foaming at high temperatures is possibly caused by Al3Ti intermetallic compounds formed at high temperature and AlN particles. Compression tests for the prepared foams revealed that the absorbed energy per unit mass of prepared Al-3.7 pct Si-0.18 pct Mg foam is higher than those of aluminum foams strengthened by alloying or dispersion of reinforcements. It is remarkable that the oscillation in stress, which usually appears in strengthened aluminum foams, does not appear in the plateau stress region of the present Al-3.7 pct Si-0.18 pct Mg foam. The homogeneity in cell walls and pore morphology due to the stabilization of pore formation and growth by AlN and Al3Ti particles is a possible cause of this smooth plateau stress region.

Effect of foaming temperature and rubber grades on properties of natural rubber foams

AbstractFoaming temperature and grade of dry natural rubber were varied to evaluate their effects on the morphology and mechanical properties of natural rubber (NR) foams. Three different grades of NR were used; namely ENR‐25, SMR‐L, and SMR‐10. NR foams from these grades were produced at three different foaming temperatures, i.e. 140, 150, and 160°C. The study was carried out using formulated compositions containing sodium bicarbonate as the chemical blowing agent and were expanded using conventional compression molding technique via a heat transfer foaming process. The NR foams were characterized with respect to their relative foam density, density of crosslinking, cell size, compression stress, and compression set. Increase in foaming temperature resulted in lower relative density and larger cell size. It was also discovered that the crosslink density slightly decrease with increasing foaming temperature. For mechanical properties, the highest foam density resulted in the highest compression stress. Compression stress at 50% strain increased with increasing foaming temperature and ENR‐25 foam has the highest compression stress among the produced foams. The results showed that the morphology, physical, and mechanical properties of the rubber foams can be controlled closely by the foaming temperature and rubber grades. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Preparation and characterization of natural rubber foams: Effects of foaming temperature and carbon black content

The influence of the foaming temperature and carbon black content on the cure behavior and mechanical properties of natural rubber foams was investigated at five temperature zones by 5 °C interval and different feeding ratios of the carbon black. The physical properties of the foamed NRs were then measured as a function of the foaming temperature and carbon black content, respectively. The optimal temperature for vulcanization and foaming of NRs in this study was considered to be 165 °C where density of the foamed NR is lower than that at other four temperature zones. The thickness of each of the struts formed within the rubber matrix decreased with the increasing foaming temperature, while it increased with the increasing carbon black content, supporting the density characteristics. The tensile properties of the foamed NRs such as tensile strength, tear strength and modulus gradually increased with the increasing and carbon black content, while elongation at break decreased.

A new technique for foaming submicron size poly(methyl methacrylate) particles

AbstractAbout 0.7–2 μm diameter poly (methyl methacrylate) (PMMA) foamed particles were prepared via thermally induced phase separation (TIPS) from a PMMA/ethanol mixture and vacuum dried. It was found that ethanol, known to be a poor solvent to PMMA, could dissolve PMMA when the temperature was over 60°C. The solubility of PMMA (Mw = 15,000 and Mw = 120,000) in ethanol was measured and was found to increase as the temperature increased. PMMA particles on the scale of submicron and single micron diameter could be precipitated from the PMMA/ethanol solution by temperature quenching. Then, since the precipitated particles contained a certain amount of ethanol, the precipitated particles could be foamed using the ethanol as a foaming agent in a vacuum drying process. Vacuum drying at temperatures slightly below the glass transition temperature of the polymer could make the particles foam. The effects of foaming temperature and the molecular weight of the polymer on the size of foamed particles were investigated. The experimental results showed that the vapor pressure and the molecular weight of the polymer are key factors determining the expandability of the micro particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Preparation and characterization of biodegradable foams from calcium carbonate reinforced poly(propylene carbonate) composites

AbstractBiodegradable foams were successfully prepared from calcium carbonate reinforced poly(propylene carbonate) (PPC/CaCO3) composites using chemical foaming agents. The incorporation of inexpensive CaCO3 into PPC provided a practical way to produce completely biodegradable and cost‐competitive composite foams with densities ranging from 0.05 to 0.93 g/cm3. The effects of foaming temperature, foaming time and CaCO3 content on the fraction void, cell structure and compression property of the composite foams were investigated. We found that the fraction void was strongly dependent on the foaming conditions. Morphological examination of PPC/CaCO3 composite foams revealed that the average cell size increased with increasing both the foaming temperature and the foaming time, whereas the cell density decreased with these increases. Nevertheless, the CaCO3 content showed opposite changing tendency for the average cell size and the cell density because of the heterogeneous nucleation. Finally the introduction of CaCO3 enhanced the compressive strength of the composite foams dramatically, which was associated with well‐developed cell morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5240–5247, 2006

Effect of reactant ratio and temperature on the characteristics of phenol–formaldehyde foams

AbstractThis study presents experimental results on the preparation and characteristics of high‐density phenol–formaldehyde foams and compares their characteristics with the available patent literature. An extrapolation of the data has been used to identify the relevant process parameters used for the preparation of lower‐density foams. The effect of catalyst combination and phenol formaldehyde molar ratio on the ease of foaming and its ultimate strength has been investigated. A total solids refractive index correlation has been developed for following the reaction. The effect of foaming temperature on the density and strength of the foam was also studied.