Thermosetting Resin Adhesive
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A thermosetting synthetic resin is one that on curing undergoes an irreversible chemical and physical change to become substantially infusible and insoluble. After curing the form of this resin or adhesive can't be back into the beginning. The term thermosetting is applied to the resin both before and after it is cured. It is not a good name because it implies only a relationship between temperature and curing.
Some thermosetting adhesive are condensation polymer and some are addition polymers. The important examples are urea-, melamine, phenol- and ressorsinol-formaldehyde adhesive, epoxy, polyisocyanate and polyester adhesives. They will be considered in that order.
Melamine Formaldehyde Adhesives
Beside of Urea Formaldehyde there are many other form compound from formaldehyde reaction such as Amine Formaldehyde or Melamine Formaldehyde. Although a number of amines condense with formaldehyde to produce resinous substances, reaction products from two only are of importance as adhesives, those from urea and those from melamine. The former, marketed many years earlier and used on a much larger scale, will be discussed firstUrea Formaldehyde Adhesive
A urea formaldehyde resin or glue (also commonly called a urea glue or a UF) is the condensation product of unsubtituted urea and formaldehyde. Thiourea is not included, resin from thiourea are of negligible importance as adhesive. Urea formaldehyde have chemical formula as C2H6N2O2General purpose of urea formaldehyde applied for wood glue such as on plywood, veneering and assembly gluing. The urea formaldehyde reaction in its relation to the preparation of an adhesive. The normal ration on reaction to form a glue use usually the molar ratio of 1U : 1.75 – 1.9 F, and rarely above 1 : 2 for the manufacture of wood particle board a somewhat lower is often used in order to keep the smell of formaldehyde to a minimum. A Rusian paper suggests the best molar ratio to be about 1:1.65, which is lower than that generally used except for making particle board, in the work referred to, a number of parameters were examined, unfortunately without relating them to the strength of glued joints.
In deciding the ratio of formaldehyde to urea, a compromise is sought between certain properties of the resin, a compromised that influence the method of manufacture of the resin solution. A high molecular ratio of formaldehyde to urea, for example exceeding two to one, result in a product having certain advantages as well as certain disadvantages. Among the advantages are increased stability in solution, and increased water-toleration or even infinite true solubility. Chief among the disadvantages is, firstly, a higher sensitivity to atmospheric moisture. In explaining this it should be understood that all uncured urea resins are to some extent hygroscopic; most powder resins have an equilibrium moisture content at between 60 % and 70 % RH, that is to say they neither absorb nor lose moisture at some relative humidity within these limits at a normal temperature.
Urea formaldehyde as Wood Glue
Urea formaldehyde as wood glue have characteristics such as low cost for huge application, low cure temperature, resistance to microorganism and also abrasion, Light color. But urea formaldehyde as wood glue have disadvantage like rapidly deteriorate if any hot solution is splash to this glue, easy to release formalin from their component. Another type of wood glue can use epoxy resin that more prefer by consumerist because have good characteristic like good gap filling, resistant to salt water, and heat resistant compare to urea formaldehyde as wood glue. So epoxy resin can stand longer in tropical climate which is often rain and make high humidity environment.Experience on Using Urea Formaldehyde.
Urea formaldehyde on resin form still don't have strong stick of two wood, this resin need a filler and hardener for gluing application. So for carpenter that is use this kind of resin usually will get a guide first from the vendor, even they don't learn on using this glue, they still have a good result after gluing their wood product. Urea formaldehyde also already sold in many material shop together with filler and hardener so you can use easily now.See form of Urea Formaldehyde Powder as result of experiment:
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| Urea Formaldehyde Powder |
Wood Glues Product
There are many wood glue are sold in the market, you can choose what is the best product as the experience of people. Wood glue also provide in many package, you can choose as you need.
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| wood glue |