Technical Notes

The Powder Liquid Acrylic System

The powder is a fine acrylic bead, a spherical particle, which is usually made as a clear bead. The powder  is made by polymerizing a monomer  in a heated reactor, which converts the monomer into the polymer bead. The process is called suspension polymerization.When a single monomer is polymerized, for example ethyl methacrylate, the bead produced is called poly ethyl methacrylate , PEMA, and is a bead which is often called fast-setting in the nail industry due to the fact it absorbs the ethyl methacrylate liquid quickly and gels quickly, limiting the working time possible.When 2 monomers are polymerized in the reactor, such as ethyl and methyl methacrylates, a copolymer bead is produced which now is a mixture of 2 polymers within the bead itself. These are known as medium set or traditional set copolymers and offer more sculpting time.The beads themselves are made with variations. The particle size of the beads can be adjusted, as well as the composition, ie the ratio of the monomers inside. The affect of lowering particle size can be a more rapid adsorption of the liquid and reduced working time  since the overall surface area is increased over the bead surfaces. Clarity can be improved also. Larger particles can exhibit longer working times and that may also be required.The beads can be treated to make them more free flowing, or several additives can be used to enhance properties.The beads are made clear, and the colour is added using ball mills and blending equipment. When the bead is made, a catalyst is also used in the reactor, which ends up inside the bead as residual peroxide The main activator is Benzoyl Peroxide  (BPO)  and this  can also be added later to the surface of the bead.There are also systems which do not use amine /peroxide as the catalyst system, and EE produces these types as well as light curable powder/liquid systems.  

How it reacts and polymerises

The powder is mixed with a liquid, the liquid being based upon ethyl methacrylate which was used to make the beads in the reactor.  The liquid contains an initiator called DMPT, a chemical which reacts with the BPO in the beads, and causes the BPO to break down and produce free radicals which then go on to make the liquid monomer polymerize into cured polymer. The liquid first absorbs into the powder bead, and swells the bead, the chemicals begin to mix and the chemical reaction begins. As the reaction occurs, a great deal of heat is given off, the reaction is said to be exothermic. In the liquid, there are other chemicals which affect the nature of the final cured polymer ( the finished nail )Cross linkers are used which, when polymerized ,make a tougher, more resistant polymer. These chemicals cross link the polymer chains and make the material more resistant to breakage and less permeable .The liquids also contain inhibitors to stop the liquid hardening on its own, UV absorbers to maintain a non yellow solution and other additives to enhance the colour or vitality of the cured polymer ( nail )  The level of DMPT can also be adjusted to speed the cure time.  

Variations and troubleshooting

When the liquid and powder are cold, the absorption and reaction of the chemicals is slower. The cure time will be lengthened, and more time is needed for the complete penetration of the powder by the liquid. The powder and liquid can be brought to room temperature to eliminate this. When the term crystallization is used, the term usually refers to the incomplete wetting of polymer beads, where monomer has evaporated before the powder has been fully solvated and polymerized. If a powder looks clumpy and not free flowing, it could be due to the polymer being over dry or in fact containing too much moisture. Flow treatments are often used which include adding silica or other ingredients to the beads to break down static charges on the beads which make things look agglomerated. If too much liquid is used in the mix ratio, the result is more shrinkage, slower cure and a diluted colour, with an increased possibility of lifting. 

 

Bonding

The nail plate needs to be very clean,dry and free of oil. The primer is the material which causes the chemical bond between the nail plate and cured polymer. EE has several solutions for this. Adhesive molecules  chemically bond to the keratin in the nail plate and acrylic groups then chemically bond to the primer below.Esschem Europe also has liquid formulations  which incorporate the primer for the so called “primerless” liquid systems  

 

The UV Gel System

UV Gel, unlike the acrylic powder/ liquid system, does not require another chemical to enable it to work, it does however require UV light. Gel is part of the acrylic family. The liquid in the acrylic system has single units of monomer, gel has chains which are called Oligomers. Oligomers are not long enough to be called Polymers. When gel is put under UV light, the polymerisation process begins. Much in the same way as with acrylic, the process is exothermic, ie, a chemical reaction that gives off heat. With gels, the exothermic reaction can be stronger, much more than with acrylic, as the chemistry in powder liquid manufacture is more controlled. The UV light causes Oligomers to link and it is this movement which causes the exothermic reaction.

Variations and troubleshooting

Gels peel or lift ; Use of too much bonder/ primer, use this product very sparingly. Insufficient filing of sides, free- edge and nail to get rid of shine prior to application, the whole nail should be shine free before application of any product. Gel on the cuticle or surrounding skin will also cause lifting

Cracking ; Sidewalls not reinforced, Gel applied too thinly, especially on stress areas.

Bubbles ; Overworked gel. In clear gel especially, sculpting the gel can cause bubbling.

Gel will not harden ; Your UV lamp bulbs could be  old or dirty. Replace bulbs every 6-9 months depending on use. White or heavy pigmented colours can take longer to cure. Also, if you are using forms remember to cure the underside of the free-edge when removing the form.