Forming & fabricating with Acrylic. ***CEMENTING ACRYLIC Part 1*** A Tenecor® Explainer

Acrylic pieces may be joined three ways:

1) mechanical means such as bolts or screws
2) thermal means such as welding
3) chemical methods such as cementing

For our purposes, I will focus on the third method, cementing. There is a great amount of misinformation regarding this topic. The information I am presenting is from knowledgeable sources including manufacturers of acrylic and manufacturers of cements. I then use our extensive fabrication experience and apply this information to real world scenarios.

It's easy, but it is not easy. Cementing acrylic is pretty easy as long as proper techniques are followed. When there are deviations from proper technique the two most common problems to appear are bubbling in the joints poor joint strength. Low joint strength may be due to a number of causes including improper fit of parts, inadequate mixing of the cement or excessive clamping pressures. The best way to avoid these problems is to follow the techniques I will share with you and to take your time.

The importance of edge and joint preparation. Preparation of the edges and joints is very important when cementing acrylic sheet. The parts must fit accurately. The parts should also fit without force. Proper preparation of edges will reduce or eliminate internal stresses which cause crazing on contact with solvent. Edges should also never be polished as this tends to round the surfaces. To further prevent crazing, avoid flame polishing.

The three primary acrylic cements (Yes, there are other options beyond Weldon 3)

Acrylic cements can be placed into three broad categories:

1) Solvent cements
2) Thickened cements
3) Polymerizable cements

Solvent Cements. The most common and well-known cements are the solvent cements. Common brand names are Weldon 3 an 4. A less common formulation is Weldon 16, a fast setting medium bodied formula. I will discuss all of these and their applications in a future post. For now, I want to create the framework for discussing them.

Thickened Cements. Thickened solvent cement is made by adding clean acrylic chips or acrylic molding resin to a solvent cement such as Weldon 3 to produce a syrupy cement that can be applied like glue. Thickened solvent cement produces an inferior joint compared to straight solvent cement in the areas of strength and appearance. Thickened cements should only be used to minimize puddling or to join two poorly fitting pieces. Avoid using thickened cements in large areas as the drying time can be very long and joint quality exceptionably poor.

Polymerizable cements. Polymerizable cements are those in which a catalyst is added to an already thick monomer/polymer syrup. The catalyst promotes rapid hardening (polymerization) and care and planning is required in its application. Weldon 40 is a polymerizable cement of this type. It is suitable for cementing all types of acrylic sheet. Polymerizable cements are the gold standard in fabricating larger aquariums. Not Weldon 3. Not Weldon 4. Or 16.

My next articles will discuss each of these three cements and their applications in greater detail. All the best.
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