Binder Extraction Research Articles

Evaluation of reclaimed asphalt pavement binder stiffness without extraction and recovery

A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement (RAP) binder was developed. In the testing procedure, the Superpave™ Bending Beam Rheometer (BBR) with special modifications and binder blending charts by Asphalt Institute were utilized. Modifications involved the development of a new kind of sample mold and different testing parameters were made to BBR testing procedure to capture the rheological properties of bitumen mortars produced by mixing fresh binder with fine RAP materials or RAP aggregate. The stiffness relationship between binder and bitumen mortar was established based on the BBR test results. The blended binder stiffness in bitumen RAP mortar was estimated from the RAP mortar stiffness based on the binder-mortar relationship. And finally, the RAP binder stiffness was estimated from the blended binder and fresh binder stiffness based on the blending charts by Asphalt Institute. The results indicate that the new procedure can capture the rheological properties of bitumen mortar and can be used to estimate the low temperature stiffness of RAP binder without binder extraction and/or any chemical treatments.

Debinding Process of a Starch-Based Binder in Metal Injection Moulding

In this study, a combination of starch, glycerol, linear low density polyethylene (LLDPE) and other additives was utilized as the binder composition. The effect of different parameters such as thickness, temperature and time on debinding process of green parts was investigated. Discs of different thicknesses consisting of 2, 2.7 and 3 mm were submitted to the water bath in order to obtain curves of time versus remaining mass of binder. Moreover, the injected tensile bar test specimens was utilized to observe specially the effect of temperature on rate of binder extraction from the green parts. The experiments were conducted at three sets of temperatures including 70, 80 and 90°C. The rate of binder removing considerably increased by decreasing the thickness of the discs. On the other hand, proportion of removed binder in injected tensile bar specimens increased in higher temperatures. The debinding process was successfully performed on injected tensile bars and the components did not suffer from any cracks and swellings. Moreover, the results show that more than 80% of the binder system can be extracted in 6 hours, which is in the acceptable time range. The investigation confirms that from the viewpoint of debinding, starch has a good potential as a binder component in MIM process.

Impact of RAP on the Volumetric, Stiffness, Strength, and Low-Temperature Properties of HMA

The increasing cost of virgin asphalt and aggregate has increased the interest in using higher percentages of recycled asphalt pavement (RAP) in hot mix asphalt (HMA) mixtures. The purpose of this research project was to gain a better understanding of how the addition of RAP affects interaction among the aged and virgin binders and the overall properties of HMA. The effects of the addition of RAP were evaluated on a macroscopic scale by comparing the volumetric properties, dynamic modulus, and strength parameters of a series of specimens containing different percentages of RAP from two different sources. Also, the viscoelastic properties of the blended or rejuvenated binder in the recycled mix were back-calculated from the macroscopic properties of the mix using the Hirsch model. Studies have shown that this back-calculation method offers advantages like elimination of the need for extraction of blended binder, the ability to use indirect tension test specimens, and the use of a mechanistic based approach. The back-calculated viscoelastic properties were subsequently used to determine the low-temperature performance grade of the binder in the recycled mix. This research project showed that the percentage of RAP affects the properties of the mixture with respect to mixture volumetrics, dynamic modulus, and strength.

Development of Eco-Debinding Process Using Supercritical Extraction of Low Molecular Organic Binders in Ceramic Bodies with Nano-Sized Capillary Structure

Eco-debinding process using supercritical extraction of low molecular organic binders in nano-porous ceramic bodies was examined. The debinding properties related to structural changes during supercritical extraction and conventional solvent extraction were also compared. The debinding rate of supercritical extraction was significantly enhanced compared to the debinding rate of solvent extraction because of the high diffusivity of the supercritical carbon dioxide for the low molecular weight wax binder in the molded bodies with nano-sized pore structure, although both debinding rates showed same a square root of time dependence. The extraction rates with morphological changes varied depending on the degree of saturation at the end of debinding stages. Both the debinding methods experienced morphological changes with a debinding front separating the pendular state region from the undebinded region with fluid state in low molecular paraffin wax based powder compacts during extraction. The capillary structural changes in the green bodies caused severe defects during extraction and degraded the physical properties. In spite of the abrupt changes of the capillary structure, the debinding defect was significantly alleviated for the supercritical debinded ceramic bodies, compared to the solvent extracted bodies.

Pressure Distribution and Defect Formation in Green Ceramic Bodies During Supercritical Extraction of Binder

Supercritical extraction (SCE) with carbon dioxide at 10–40 MPa and 55°–90°C has been used to remove binder from multilayer green ceramic bodies. Defects such as cracking and delamination were occasionally observed in the green bodies following the extraction process, and these defects were attributed to pressure gradients that arise during isothermal depressurization from conditions of SCE. A model based on flow in porous media was developed to describe the temporal and spatial distribution of pressure within the green body during depressurization. The model incorporates both nonideal pressure–volume–temperature behavior and nonconstant viscosity of the supercritical fluid. The effects of the body size and gas‐phase permeability on the pressure within the green body were examined.

吸着剤を用いた超臨界二酸化炭素脱脂法のＭＩＭプロセスへの適用

Commercial MIM processes use thermal debinding and solvent debinding; the former requires a long debinding time, while the latter involves the use of toxic solvents. We have been investigating the application of supercritical CO2 extraction method to debinding process, which promises to overcome these drawbacks. For actual application of this process, we need to overcome two problems. The first one is that the process requires the high-cost pressure vessels, and the second one is low solubility of binders in supercritical CO2. In the process developed by Takishima and others, the latter problem is resolved by using of activated carbon as an adsorbent; this method is efficient and fast but introduces the additional problem that used activated carbon becomes waste. Here we propose the use of a liquid solvent as an adsorbent. This method allows easier treating of the adsorbent and higher binder extraction. The dissolved binder can be re-extracted from the adsorbent by distillation. Moreover, the extraction pressure can be decreased with using this method, and the cost for the pressure vessel can be reduced.

Effect of Aggregate Degradation on Volumetric Properties of Georgia's Hot-Mix Asphalt

Various degrees of degradation of aggregate particles can occur in hot-mix asphalt (HMA) production during the mixing and compaction process. This breakdown may significantly increase the dust fraction of the aggregate gradation relative to that of laboratory specimens. This increased dust fraction could cause a loss of voids in the mineral aggregate (VMA) and air voids. After evaluation of 22 variations of HMA mixtures during production and construction, it was determined that aggregate degradation did result from plant mixing and field compaction activities. Aggregate degradation varied somewhat with respect to where the mixture was sampled within the production and construction processes. Aggregate degradation resulting from binder extraction that uses the ignition method, relative to the solvent extraction method, was also examined. Mixture volumetric properties (i.e., air voids and VMA) were significantly affected by aggregate degradation. On the basis of this study, before a volumetrics specification for mixture acceptance is investigated for future implementation in Georgia, a change in the Georgia Department of Transportation's mix design specification is recommended. The minimum VMA values for Superpave® mix design should be increased by 1% for all dense-graded mixes to compensate for the amount of aggregate degradation and loss of VMA during HMA production and construction. It is believed that this research-based policy change for mix design will better maintain the balance between proper durability and rut resistance of asphalt pavements in Georgia.

Debinding of injected parts using an abnormal glow discharge

Results of binder removal of injected PM components using plasma technology are presented. The samples were injected with 55.18 vol.% of iron powder, 23.57 vol.% of paraffin and 21.25 vol.%. of polypropylene and treated in hydrogen and argon discharges at a pressure of 400 Pa (3 Torr), varying temperature and treatment times. The discharge was generated by a pulsed power source in a confined anode–cathode geometry. The outer electrode consisted of the cathode and was heated by the bombardment of ions accelerated in the cathode region. The sample was placed on an inner holder and heated by thermal radiation. Three different configurations of electrodes were used in order to evaluate the influence of electron bombardment on the sample surface, the interaction of the reactive species generated in the discharge with the binder and thermal effects on the dissociation of the organic molecules. Samples were characterized by mass loss and energy dispersive X-ray (EDX) analysis. The results show that the electron bombardment added to the interaction of reactive species on the sample surface significantly activated the binder removal. By using a laboratory scale plasma reactor, it was shown that the binder extraction and pre-sintering cycle could be performed in a single thermal cycle lasting approximately 200 min.

Defect Formation during Supercritical Extraction of Binder from Green Ceramic Components

Supercritical extraction in carbon dioxide has been used to remove binder consisting of 60 wt% poly(vinyl butyral) and 40 wt% dioctyl phthalate from multilayer ceramic capacitors containing barium titanate as the dielectric. The amount of binder removed increases as both the temperature and pressure of the supercritical fluid increases; a maximum of ∼50% of the binder can be removed using carbon dioxide in 3 h at 75°C and 40 MPa. During depressurization from the supercritical state, defects such as fracture and delamination were occasionally observed in the green body. The occurrence of defects is related to the rate of depressurization, the permeability of the body, and the green strength of the body. The origin of the defects is discussed, and ways to mitigate them are presented.

Effect of solvent debinding variables on the shape maintenance of green molded bodies

In order to study the effect of solvent extraction debinding variables on the shape maintenance of green molded bodies, powder compression molded bodies (the feed) were debound in various organic solvents such as n-hexane, n-heptane and isooctane at various extraction temperatures ranging from 30 to 60°C. The solvent to feed ratio of dilution was studied in the range of 7:1 to 15:1 by weight. Finally the effect of extraction time on the amount of binder extracted and diffusion coefficient of paraffin wax was studied in the range of 1 to 5 h. Thermo gravimetric analysis (TGA) was used to confirm the extraction of the major binder and stearic acid constituents completely from the binder mixture. Scanning electron microscopy (SEM) was used to see the pores in the green bodies created after solvent extraction process which allowing the degraded products (minor binder) to diffuse to the surface easily.

Influence of Powder Geometry on Powder Injection Molding Process Parameters

Powder injection molding (PIM) is an alternative route to produce components from metallic powder that have been growing in last 10 years. The process may be divided in five basic steps, that is powder-binder mixing, mixture injection, binder extraction and sinterization. The greatest advantage of the metallic powder processing is that it surmounts difficulties from conventional powder metallurgy regarding feasibility of tridimensional shapes and density homogeneity. Powder selected to PIM process must provide a high powder packing and sinterability, which is necessary to obtain adequate final density levels. In this way, spherical powders not higher than 20 pm are usually used. In the present work, the possibility of using non-spherical powders for PIM was investigated. To provide basis for comparisons, spherical and non-spherical powders were tested. Powder influence was analyzed concerning viscosity behavior.

Extraction of binders from green ceramic bodies by supercritical fluid: influence of the porosity

Organic additives can be extracted from extruded or injection-moulded ceramic parts by using supercritical fluids leading to defect free green parts in a short time. A model previously defined, that predicts kinetics of extraction of solid binder molecules by solubilization and diffusion of solubilized species has been modified with a corrective term taking into account the capillary migration of a liquid organic phase according to the microstructure (pore size distribution, tortuosity) of the green sample and to the characteristics of the liquid phase (viscosity, surface tension). An analytical expression of this corrective term is proposed, for a paraffin binder and for three alkanes which are representative of its molecular distribution. The corrective term is related to the length scale over which the liquid binder flow occurs and to its linear velocity. The modified model allows the prediction of the kinetics of extraction of a given paraffin binder, by using the effective diffusion coefficient of the binder, determined with large pore size green samples and a capillary factor, calculated from binder and microstructure characteristics of the green part.

The use of co-solvents in supercritical debinding of ceramics

Abstract Extraction of organic binders (paraffin waxes) from injected green ceramic parts, by using supercritical fluids, has proven to be very efficient (short time of extraction, no defects in the green part). The extraction is more rapid when the binder is in the liquid state due to capillary migration but the capillary pressure could damage the ceramic green body because of development of internal stresses. In turn, extraction of the binder in solid state avoid formation of defects but the kinetics of extraction by solubilisation in supercritical carbon dioxide is reduced. An organic co-solvent can be added to supercritical CO 2 in order to increase the solid paraffin molecules solubility. Polar and non polar organic co-solvents were tested and their efficiency on the solubility of the paraffin molecules were compared. The influence of the length of the chains and of the number of side groups of co-solvent molecules were examined. The extraction was also performed by adding mixed co-solvent molecules. Mixtures of polar and non polar co-solvents were introduced in supercritical CO 2 . Improved extraction by a factor 5 was obtained with n-hexadecane molecule as co-solvent, which represents a good compromise between destruction of the paraffin binder molecular cohesion, which requires, on one hand, large molecules, and mobility, which requires, on the other hand, small molecules.

粉末プロセスにおける制御と製品の評価 超臨界二酸化炭素に溶解度を有する分散剤を用いたＭＩＭプロセス

We have studied improvement of debinding process, especially binder extraction method, which is bottle-neck for MIM process. The binder can be extracted by using supercritical carbon dioxide. This extraction method in the MIM process is proved to reduce the debinding time, compared with thermal method. In this study, we report excellent results: the mechanical and physical properties by using, myristic acid and palmitic acid, as dispersing agents, which are dissolved in supecritical carbon dioxide, compared with stearic acid.

Fabrication of high-aspect-ratio ceramic microstructures by injection molding with the altered lost mold technique

A fabrication process for complex ceramic microstructures was proposed that combines a lost mold technique and ceramic injection molding. Two key points in this process were studied. First, the solubility of several engineering plastics in various organic solvents was tested to find appropriate combinations of mold material and solvent for dissolving molds. Secondly, the binder extraction rate and the strength of a green body during debinding were investigated. Experimental results indicate that acrylonitrile-butadiene styrene and acetone are the best combinations selected for this lost mold technique. We also propose that using gasoline as the debinding solvent and performing the debinding at room temperature will give a good time-saving effect and avoid toppling the microstructure if paraffin wax, stearic acid, and polyethylene were selected to compound the binder system. This process has been successfully applied to fabricate several ceramic microstructures, such as an integrated punch.

Thermal processing of multilayer PLZT actuators

Cofired multilayer actuators (MLAs) can suffer from reliability problems due to internal cracking, resulting from imperfections formed during binder extraction or sintering. Thermal processing methodology was developed to optimize manufacturing output of defect-free multilayer actuators. Rate-controlled thermogravimetry (RCT), in which furnace power is adjusted to maintain a constant specimen weight loss rates, was used for organic binder burnout in MLAs. The effectiveness of the various thermal schedules in eliminating MLA damage was determined through image analysis of depth profiles, ground perpendicular to the layers. The damage resulting from RCT schedules were compared to those produced using conventional temperature-controlled thermogravimetry (TCT). Specimens heat-treated with mass loss rates of 0.003 to 0.03 wt%/min showed fewer microstructural defects than all evaluated TCT schedules. Under RCT, furnace power was adjusted to mitigate the effects of rapid burnout of the multicomponent binder, which surged at specific temperature ranges. The effect of introducing a modified atmosphere of MLAs was also investigated using thermogravimetry in conjunction with mass spectrometry.

Supercritical extraction of binder containing poly(vinyl butyral) and dioctyl phthalate from barium titanate–platinum multilayer ceramic capacitors

Supercritical extraction using carbon dioxide was examined for the removal of binder from multilayer ceramic capacitors. The binder contained poly(vinyl butyral) (PVB) and dioctyl phthalate (DOP), and the dielectric and metal electrode materials were barium titanate and platinum, respectively. At 40 MPa of carbon dioxide at 95 °C, approximately 55 wt % of the binder could be removed, and this was mainly the dioctyl phthalate component. The use of entrainers such as 2-propanol, methyl isobutyl ketone, and n-hexane was seen to have negligible effect on the degree of binder removal. The dielectric constant, loss tangent, and breakdown voltage of devices processed by supercritical extraction were similar as compared to devices processed by thermal oxidation alone. Although it was not possible to extract all of the binder with supercritical carbon dioxide, removal of the DOP fraction increases the pore space in the body by a factor of two. Transport model calculations indicate this partial removal of binder mitigates the buildup of pressure in the subsequent thermal processing step and can reduce the processing time for thermal removal of the remaining binder by a factor of 25.

Alternative Solvent for Reducing Health and Environmental Hazards in Extracting Asphalt: An Evaluation

Trichloroethylene is a solvent currently used by the Florida Department of Transportation (FDOT) and many state highway agencies for separation of asphalt binders from asphalt paving mixtures in their quality control programs. However, it has been proved that trichloroethylene contributes to ozone depletion, and it is also known to be a carcinogen. The goal of the present study was to determine whether a more environmentally sound and less hazardous solvent could be used for this purpose. The solvent investigated is an n-propyl bromide with the trade name EnSolv. Preliminary studies show that it is safer than many other solvents available today. The study was performed to determine whether EnSolv could be a substitute for trichloroethylene without changing current testing methods. The tests performed included the asphalt solubility test, extraction and recovery of asphalt binders from mixtures, and penetration and viscosity tests with the recovered binders. The results of the study showed that EnSolv could be a suitable replacement for trichloroethylene. In addition, EnSolv could also be recycled and reused in the extraction and recovery procedures.

Binder extraction from green multilayer ceramics using a weight loss rate-controlled thermogravimetric analyzer

A weight loss rate-controlled organic extraction furnace was built and demonstrated using a multilayer green ceramic. Multirate weight loss schedules as well as automated atmosphere control and detection were demonstrated. The low thermal mass furnace showed good tracking with 300 °C heating and cooling rates. This furnace, coupled with appropriate PID control constants, facilitated feedback control which could extract organics rapidly without self-ignition to uncontrolled combustion. Controlled organic burnout was demonstrated at weight loss rates up to 0.5%/min in air. Damage-free multilayers were observed using a burnout rate requiring 150 min for extraction, rather than the days commonly associated with this task when using conventional furnaces.

Extraction of Binders with Supercritical Carbon Dioxide

Extraction of Binders with Supercritical Carbon Dioxide