Archive for Use of glues and adhesives
Glues and adhesives
We’ve all experienced situations where a particular adhesive hasn’t worked as well as we’d hoped, and often we have no idea why. The following information will help you understand how certain adhesives work.
It’s an exciting science among adhesive manufacturers to try and make the ideal one-fits-all household adhesive but, to date, no one has succeeded. For this reason many manufacturers are now marketing adhesives in kits, in an attempt to cover all needs. One of these kits, which usually contains a white glue, a contact adhesive and an epoxy, might be all you ever need.
| There are basically two ways in which glues work. One is by mechanical bonding, when the glue seeps into the pores of a material and makes a mechanical bond. The second process is by chemical bonding, when the molecules in the glue combine with the molecules in the material. |
Porous materials like timber are best bonded mechanically and non-porous materials like glass or ceramics are best bonded chemically for maximum strength.
Flexibility of the glue is also an issue. Some glues dry rock hard and tend to crack if flexed. Others, such as those that join parts of a shoe, are able to flex after they have dried or cured.
Sometimes you might want a very temporary adhesive that won’t leave residual marks.
Some adhesives, such as cyanoacrylate glues (superglues) work instantly on skin, and many are toxic, so they should be treated with great care and kept out of the reach of children.
Artworks, valuable printed materials or photos should be mounted using only acid-free adhesives, to avoid damage over time.
The following chart will help you understand how glues and adhesives work. They can’t, however, take the place of thoroughly reading all the information and directions on a tube, bottle or can of glue or adhesive. Safety precautions on the container should also be adhered to.
See also, ‘Adhesive tapes’, in the Contents List of this website.
Glues, adhesives and mastics
| Adhesive | Uses | Features | Set time |
| PVA/white glue(polyvinyl acetate) | Porous materials such as wood, plywood, chipboard, cork, cardboard, fabric. The water content can tend to stretch and buckle paper or thin cardboard. Ideal for interior wood bonds and furniture. Needs clamping. | Water-based, easy clean-up. Carpenter’s version creates strong bond, but some are soluble if soaked in water. Coloured white but dries clear. Non-toxic version available for children. | 30 minutes.Relies on evaporation to form the bond. 12 hours to reach full strength. |
| Cyanoacrylate(instant superglues) | Plastic, rubber, metal, ceramic, glass, hardwood. A close fit between the materials is necessary to achieve a cure.Some materials, such as heat-resistant plastics, can’t be bonded with cyanoacrylate glues. An epoxy resin may be required to bond such materials. | Comes in a squeeze-tube. Toxic and should be handled with care. Moisture causes the necessary chemical reaction to occur, so applying a thin layer of water or even breathing on a very dry surface will create a strong bond.Most can be cleaned up or dissolved with acetone (nail polish remover) and, sometimes, hot water. | 1 to 4 minutes.Generates its own heat for fast curing. |
| Two-part epoxy glue | Most rigid materials. Bond is strong and waterproof. Clamps may be necessary if bond isn’t immediate (read instructions on can or tube). | Part A and Part B must be mixed prior to application. Forms a chemical bond.Read instructions for setting time to determine how much to mix for your particular project.Fills gaps well. Can be drilled, sanded or painted when set. | Varies from minutes to hours.Reaches full strength in up to 3 days. |
| Contact adhesive | Because this is a solution of synthetic rubber and solvent it is ideal for joining flexible materials such as fabric, paper, cardboard, laminates, leather and metal. | Both sides must be coated and allowed to dry. On contact the surfaces adhere immediately and there is little chance for adjustment. Plan methods to align both parts before initial application of the glue. | Immediate, and builds strength in a short time. |
| Hot melt | Low temperature melts (121 ºC) bond fabric, leather, wood and other delicate or flammable materials such as paper, lace, foil or foam.High temperature melts (193 ºC) bond ceramic, plastic, wood and metal.Dual temperature guns are available.Makes a strong bond. | Available as hot melt sticks, which must be fed through a heated glue gun. Generally clear, but available in a range of colours to match craft projects. Also available in fabric or tape form, which can be set by application of a hot iron to mend or patch fabrics. | On contact. |
| Paste/powdered glue | Used for wallpaper and thin paper. | Powder is mixed with water to reach desired consistency. Read instructions for best mixing method. | 30 minutes.Dries by evaporation. |
| Re-usable mastic ‘Blu Tack’ | A squidgy, rubbery substance that forms into small balls. Will flatten between a wall and object to be hung and form a relatively strong adhesive for light-weight objects.Once removed, some residue might remain. Roll a fresh ball and roll it over the residue. Its self-adhesive properties will lift the residue. | To hang a poster of your favourite hunk or babe, attach a small ball of mastic to the back of each corner. Attach each corner piece to the wall by pressing on the front of the poster … and you’ll have him looking adoringly at you all night. When you’re over him, just pull him off again. | Immediate with pressure. |
| Glue sticks | Generally used for paper, craft and school activities.Most will wash out of clothing. | They come in non-toxic form.Acid-free versions should be used for mounting artworks. They also come in low-tack form, which allows for repositioning or peeling with minimal damage. | On contact to 15 minutes. |
| Spray adhesives | Depending on how much tack they have and how quickly they dry, they can be used for different purposes.Some join a variety of surfaces permanently, including polyethylene sheet or carpet underlay, while others allow for temporary positioning of paper, fabrics or foam.Some may be used for lightweight home and business applications such as silk flower arrangements, scrapbooking and laminating paper.Extra strong spray adhesives can bond kitchen bench laminates or shelving. | The wide range available makes it essential to read all directions carefully.Care must also be taken to mask or avoid over-spray.Some spray adhesives are designed for very specialised applications, such as bonding vinyls, rubber and plastic products only. | Varies. |
| Caulking gun adhesives and mastics | You need only to visit a hardware shop to see the range of tall tubes available for application with a caulking gun. They are designed for large carpentry, roofing, metal or construction projects and have specific application criteria. Talk to your hardware merchant for details on each. | Sometimes specialist construction adhesives are available in small tubes, ideal for a small job where specific adhesion properties are required. | Varies. |
