Acrylic Sheets

Most Acrylic are chosen for many application because of a unique combination of properties: crystal clarity, good surface hardness, chemical resistance and excellent mechanical stability.
We can begin acrylic products with methyl methacrylate monomer because it’s the primary raw material, which is usually produced by a two-step process:
Acetone + Hydrogen cyanide –> Acetone cyanohydrin (1)
Acetone cyanohydrin + Methanol / other alcohols –> methacrylate ester (2)
As long as I knew that the casting process is most frequently used to produce acrylic sheet, which can be made by cell casting or by continuous casting. Cell casting is a batch process in which catalyzed monomer by peroxide(that is redox reaction) is heated between two pieces of polished glass held together by spring clips to respond to the contraction of the acrylic material during cure. For continuous casting, they are made between polished stainless moving belts. Each procedure has its advantadge and both afford products of good quality. Cell casting has better optical quality and smoother surface because of the casting medium used, and the other side if we use the continuous casting process then sheets will more uniform thickness.
We usually wouldn’t get the nice sheet if we used the monomer to fill in the cell. Therefore, before the monomers are filled in the cell of glass plates, we must make a prepolymerize syrups. That is monomer which catalyzed where the condition temperature usually at 170oF to 190oF. The prepolymerized syrup sometime is need to keep cool for reactive grade, so that is still depending on the grade of methyl methacrylate(MMA). After that, we can mix the syrup with colorant then filled in the cell and waiting for 30-60 minutes to remove all entrapped air which might cause air bubles in the final product. Next, it is heated in the water bath/moved into an oven or combine there.
How long it will be cured? It cured depend on the amounts of catalyzer and temperature of continue process. If we would like curing process more faster than normal, please added the catalyzer much more. But, we also need to control the hardness quality, because if the sheet is too hard then it would be very britle. How ever, free monomer in the final product is still needed.
For continuous casting, we also need to increasing the viscosity of monomer which depends on the method used for introducing the polymer mixture to the casting machine. The other step for continuous casting almost the same with cell casting.

Plastic? Polymer? Macromolecule?

Polymers are macromolecules, but we can’t say that is also opposite. For example: Enzymes are macromolecules, but there not polymers. International Union of Pure and Applied Chemistry(IUPAC) defined a polymer as a substance made of large molecules that is characterized by the multiple repetition of one or more species of atoms or group of atoms (called monomers or constitutional units) linked to each other covalently in amounts sufficient to provide a set of properties that don’t vary markedly with the addition or removal of one or a few of the constitutional units.
And we can say that plastic are a special group of polymers with characteristics that differentiate them from fiber, rubber, adhesives and other materials that are also polymers. The same type of polymer may belong to more than one group, depending on its molecular weight and how it is processed. The main characteristic of plastics is their ability, while solid in the finished state to be made to flow and be moulded using controlled heat and pressure at relatively low temperatures compared to glass and metals. They are also materials capable of being deformed continually without rupture by a stress which exceeds a yields value during the processing. You can easily shape plastic into the desired form by increasing the temperature and pressure to soften it and mold it into a new shape on cooling condition.
Perhaps in the past, we didn’t know that plastics can be divided 2 categories. First, called as thermoset, can be shaped only once because they form irreversible covalent bonds between chains during the setting process and consequently will no longer melt and flow. Example thermoset is vulcanized rubber. They have relative high chemical resistance and excellent mechanical properties. The other one is thermoplastics. Thermoplastics are able to repeatedly undergo this shape changing treatment. As follow are various kind of familiar plastics who we knew :
1. Polystyrene
– Acrylonitrile Butadiene Styrene
(ABS, those have some types are Pollac 757, Kibisan, Arbelac)
– GPPS, High Impact Polystyrene(HIPS)
2. Polyolefin
Those are Polypropylene(PP), Polyethylene(PE), High Density Polyethylene(HDPE),
Low Density Polyethylene(LDPE), Low Low Density Polyethylene(LLDPE),
Polyethylene Therephtalate(PET)
3. Polyvinyl Chloride(PVC)

Now, You know “What is plastics?”

How many hour in weathering tester equals a year of outdoor exposure ?

Yeach, that was the most frequently asked question expecially by sales person or our customer. That is a simple question, but not easy to explain.Why? Because, we can’t find a number or something which multiplied by weathering tester exposure hours to compute years of the outdoor exposure.
The biggest problem is too many variables and so complexity of outdoor exposure situations. All those difficulties appear because of amount of variables as follow :
1. The geographical latitude/altitude of exposure site
2. Local geographical features such as wind factor
3. Random year to year variations in the weather/seasonal
and also about the variables in the accelerated tester such as operating temperature and the cycle time, artificial lamp which used
So, that is impossible if we have compare between indoor and outdoor testing. Wheathering data is comparative data, not absolute data. We need to compared between the standard and the batch. So, we know which one the best for our customer.
However the best way to test the weatherability is testing outdoor exposure where the product will be used. If the product will be used to export market and you don’t have any collegous, at least you can do the testing in your local only. But, through the accelerated weathering tester at least we can do the service more faster to our customer or as the quicker testing.
Good luck sales man for your customer. If you have any question, I willing to open. By………….