Cold Mounting by Metallurgical Supplies
Cold Mounting - by Metallurgical Supplies a Metallography World Corporation
COLD MOUNTING SUPPLIES FOR SAMPLE PREPARATION
Cold Mounting systems are recommended for mounting specimens that are sensitive to high pressures and temperatures. Epoxy products provide good physical adherence, low shrinkage, and excellent infiltration into pores.
Epoxy Systems - Cold Mounting
Epoxy Systems - META-EPOVELOX SERIES
Epoxies have the lowest shrinkage of all cold-mounting resins. The hardened epoxy is duroplastic, and not affected by moderate heat or chemicals. Epoxy resins are suitable for mounting of all types of materials and are especially recommended for vacuum impregnation. The curing time is relatively long, but adhesion to most materials is excellent. They polymerize through a chemical reaction after being mixed in the correct proportions. Metallurgical Supplies' epoxy systems consist of two components: a resin and a curing agent/hardener. Properties such as low vapor pressure, transparency, excellent adhesion, low viscosity, and no shrinkage are all specific to epoxies. As the stoichiometric resin:hardener ratio is critical; both parts should be weighed to obtain the best mounting result. If it is only possible to measure the amount by volume, use syringes to measure the quantities of resin and curing agent/hardener.
Acrylic Systems - Cold Mounting
Glass Filled Acrylic Systems - Cold Mounting
Acrylic Systems Slow Cure - Cold Mounting
Acrylics are easy-to-use resins with short curing times, minimal shrinkage, and excellent mounting properties. They are well-suited for both serial mountings of irregularly shaped specimens and for routine work or single specimens. Acrylics are available with and without a mineral filler. The dye can be used if color coding is needed. When mixing acrylic resins, it is recommended to add powder to the liquid (hardener) – this will result in the most uniform resin mixture. - Castable acrylics are easy to use and are very robust. The main advantage of mounting with castable acrylics is the fast curing time. Depending upon the mixing ratio, castable acrylic mounts are typically ready to use within 8-15 minutes. Also unlike epoxy resins, the ratio of the various acrylic parts (powder to liquid) can be altered by up to 25% with no adverse effect to the final properties of the mount. This is because both the liquid and powder are acrylics with various additives and curing agents. By varying the ratio of the liquid to powder, the curing time and viscosity can be altered. The powder contains a catalyst that reacts with the liquid hardener to start the curing process. Fillers are added to increase hardness and to reduce shrinkage.
Features of Acrylics :
- Rapid mounting
- Very repeatable and consistent
- Moderate shrinkage
- Good hardness
- High odor
Polyester Systems - Cold Mounting
Polyesters are typically used when a very clear mount is required. Polyester resins are also useful for mounting parts for display. In this case, the part appears suspended in the plastic. The procedure for molding samples for display is to first determine the mixing ratio of the resin to hardener (catalyst). This ratio is variable depending upon the mass of the casting. For larger volumes, the amount of hardener needs to be reduced significantly. The procedure for suspending the sample in the mount is to pour an initial layer and allow it to pot or gel (do not let it fully cure). The object or specimen is then placed on the initial rubbery polyester layer and another layer of the liquid polyester is poured. Multiple layers can be poured in this fashion if required.
Optimized Chemistry for Excellent Results: Epoxy chemistry is a complex balance of many factors including shrinkage, cure time, viscosity and adherence. Each lab application requires a slightly different priority of these factors and our line of epoxies have been specially developed to provide the ideal product for your application.
Mounting specimens in a holding device is necessary when preparing irregular, small, very soft, porous, or fragile specimens, and in those cases where edge retention is required. Embedding is indispensable when multiple specimens are to be included in a single mount or when automatic equipment is to be used in the following preparation. In most cases, mounting follows sectioning, but in the handling of a great number of very small specimens, it may be advantageous to reverse this order. In general, the mounting procedure can be easily adapted to the special problem in question. The shape, size, and numbers, as well as the hardness, brittleness, porosity, and heat and pressure sensitivity of the specimens, have to be considered when mounting. Other considerations are: should a cross or a longitudinal section be prepared, is a controlled material removal required, is good edge retention needed, and should the preparation be carried out manually or with automatic equipment in specific sample holders. A suitable mounting media must meet several criteria: it must have good adhesion to the specimen, sufficient mechanical strength (hardness), and chemical resistance to etchants or solvents that are used during the preparation. For electrolytic polishing, scanning electron microscopy examination, or microprobe analysis, the mounting medium has to be electrically conductive. The mounting material should be easy to handle, economical, if necessary easy to remove, and it should not affect the specimens. For some investigations, a transparent mounting medium is more appropriate than an opaque material, and in cases where the specimens have to be analyzed with x-rays, a mounting material free of any interference reflexes should be selected. Because of these varied requirements, many different techniques were developed for the mounting and embedding of metallographic samples. They are summarized schematically in Fig. 1.2 and can be described as two basic types of mounting: clamping with a sample holder or clamp, and embedding the specimens in organic or inorganic materials.
Embedding or casting of plastic materials around the specimens is the most popular technique and can be divided into “cold” and “hot” mounting, depending on whether or not heat is needed for the polymerization process
Cold mounting (room-temperature curing) requires the mixing of two agents (a crude polymer and a catalyst); this mixture is then cast over the specimen within a mold, in which it reacts to form a solid part. A slightly higher pressure during curing improves the adhesion to the specimen. Special equipment is available to mount several samples simultaneously.
Hot Mounting (compression molding) requires a mounting press where the sample and the mounting compound can be heated and simultaneously compressed. Two essential types of mounting materials are available, thermosetting and thermoplastics. Both types are available as hot and cold mounting compounds, depending on whether the polymer reaction occurs with added heat or with the addition of a catalyst. The curing of thermosetting materials is irreversible, and they cannot be re-softened after curing; cured thermoplastic materials, however, can be re-melted again at elevated temperatures.
Mounting accessories many different clips, cups, pigments, and fillers are available to help simplify, improve, or customize a mounting process.
High-Quality Mounts: Mounting cups are available in multiple shapes and sizes to create high-quality mounts with easy removal.
Consistent Specimen Alignment: Support clips allow for precise placement of the specimen in the mount to ensure the area of interest is properly presented for grinding and polishing.
Unique Mounting Applications: A variety of colored pigments, fillers, and cement offer many options to customize the mounting process to meet any lab's needs.
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