Acrylic Embedment
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Acrylic embedment is a process of encapsulating various objects into
lucite Poly(methyl methacrylate) (PMMA) belongs to a group of materials called engineering plastics. It is a transparent thermoplastic. PMMA is also known as acrylic, acrylic glass, as well as by the trade names and brands Crylux, Plexiglas, Acrylite, ...
(
cast acrylic Cast Acrylic is a form of poly(methyl methacrylate) (PMMA). It is formed by casting the monomer, methyl methacrylate Methyl methacrylate (MMA) is an organic compound with the formula CH2=C(CH3)COOCH3. This colorless liquid, the methyl este ...
). The process is used for preserving specimens, encapsulating electronics, and making decorative items such as trophies ( deal toys) and jewelry.


History

In the early 1940s, Armand G. Winfield was interested in preserving biological and geological specimens. He developed a method for embedding such specimens in clear acrylic plastic, and by 1945, his process was used to mass-produce objects embedded in acrylic. In addition to preserving specimens, Winfield’s work included encapsulating electronics in acrylic and the production of acrylic jewelry.


Process


Pouring

The process starts with two basic ingredients, an
acrylic resin 186 px, Polyhydroxyethylmethacrylate is a typical acrylate resin. An acrylic resin is a thermoplastic or thermosetting plastic substance typically derived from acrylic acid, methacrylic acid and acrylate monomers such as butyl acrylate and or me ...
powder
polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
and clear liquid
monomer In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification Mo ...
. The polymer and monomer are mixed together in specific proportions. The result is a thick, opaque liquid. The mixture is hand poured into molds and allowed to partially harden. Objects to be embedded are then hand placed into the acrylic layer. Another layer is poured over the embedded object and the acrylic is again allowed to harden. During this stage, the liquid acrylic is an opaque, milky white. It is very difficult to center objects on multiple levels when the objects below cannot be clearly seen. Because these embedded objects are placed by hand, no two acrylic embedments are ever exactly alike.


Curing

After the acrylic has hardened, the molds are placed into an oven. There, heat cures and pressure (exceeding 12 atmospheres) compresses the air bubbles to completely harden the embedment. This curing process may take up to seven hours. After cooling, the acrylic embedments are removed from the molds and the sizing process begins. All acrylic parts are cast oversized to allow for shrinkage, which varies from part to part. Three steps are taken to size the embedments.


Sanding

The parts are ground down to size by hand on large industrial
sander A sander is a power tool used to smooth surfaces by abrasion with sandpaper. Sanders have a means to attach the sandpaper and a mechanism to move it rapidly contained within a housing with means to hand-hold it or fix it to a workbench. Woodwo ...
s. A coarse grit belt is used first, followed by a medium grit belt. A final sanding with a fine grit belt makes it easier to polish the sanded acrylic. Variations occur in this sizing process since it is all done by hand.


Polishing

Polishing is the next step in the process. It is mostly done by hand. This brings out the luster and high gloss of the acrylic not previously seen during production. A rough buffing is administered to remove all sanding lines. A final polishing then brings out the bright crystal-like finish. The production of the acrylic embedment is completed.


Inspection

The final phase now begins. Each embedment is carefully hand wiped and visually inspected. If flaws or any other defects are detected, the part is returned for additional finishing or rejected for recycling. After passing through inspection, each part is individually bagged and boxed. This entire procedure makes the result more expensive but because of its glossy look an acrylic embedment is very much in demand.


See also

Because of the high amount of technical knowledge required, the total number of manufacturers remains small. These include:
Engraving, Awards & GiftsElectron Microscopy Sciences
an
USAcrylic Awards
More information can be found here
Engravers Journal
an
USAcrylic Awards.


References

{{Reflist Plastics applications