Architect and designers are increasingly designing furniture, reception desks and kitchens with curved panels or doors. These curved designs look stunning in the right situation, but unfortunately the designers don’t think about how to bond the veneer or laminate on to the cores to make up these pieces of furniture. This is where we can help out.
Curved doors and panels can be made up of a series of laminations of thin plywood, or flexi plywood which is designed specifically for this application. The laminate or veneer is then bonded to the face of the panel. A variety of different methods are used to hold the laminations in place whilst the cure takes place including using a vacuum press, creating a jig system with a male and female former or, in the case of using a contact adhesive, laminating directly to the core and using a pressure roller to strengthen the bond.
The most common adhesives used for curved laminations are UF (urea formaldehyde) resins, PVA’s or contact adhesives. Each of these adhesives will work in the right situation, but there are considerations you need to think about when making the choice.
UF RESINS FOR CURVED BONDING
Our preferred recommendation is to use UF (urea formaldehyde) resins as they provide a strong and brittle bond which will hinder the lamination from trying to bend back to its original flat shape. PVA’s tend to be more flexible and as a result will tend to bend more. UF resin systems, including Cascamite/One Shot, are applied with a roller and then allowed to cure whilst the lamination is held in place.
The most effective way of holding the lamination in place is to use a vacuum bag press. With this system, the lamination is positioned around a former, inserted into a large plastic bag, and then the air is expelled with a vacuum pump, which tightens the lamination around the former and held in position whilst the cure takes place. Simple and relatively inexpensive vacuum bag press systems are easily sourced which are particularly good for the smaller user. Larger industrial vacuum presses are available for high volume production, which sometimes have heat facility helping to cure the adhesive quicker.
Alternatively, a male/female jig system can be manufactured to form the lamination around whilst the cure takes place.
We have a couple of systems available – Prefere 4152 with a range of powder hardeners and Prefere 4114 with a range of liquid hardeners. One Shot Adhesive (commonly known as Cascamite) can also be successful and our product is Aerolite UP4145.
PVA ADHESIVES FOR CURVED BONDING
As mentioned above, PVA is not our first choice for laminating and bonding curved doors or panels. PVA adhesives tend to be more flexible than UF Resins so can have a tendency to move. However, we recognise that PVA is easier to use and some can make this work quite successfully but we would recommend that the bond is allowed to fully cure and that a PVA which has good creep resistance is used.
Curved laminations using PVA adhesives can be made up in the same way as UF resins, i.e. using a vacuum press or forming jig.
We have two PVA adhesives which have high creep resistance – Aro-Bond® 533 and Aro-Bond® 535. Aro-Bond® 535 is a lower viscosity version of Aro-Bond® 533 and is more suited to larger panels.
CONTACT ADHESIVES FOR CURVED WORKS
Not every curved panel bonding application suits using a UF Resin or PVA, particularly if the lamination bonding has to be done on site, or on a large piece of furniture. This is where contact adhesives come into play and can be used successfully.
A contact adhesive is an adhesive which is coated on both substrates to be bonded, allowed to dry to a tack free state, and then the substrates are offered up to each other for the cure to take place. A pressure roller is applied to the face veneer or laminate to strengthen the bond and remove any bubbles or imperfections.
Contact adhesives can be used with high pressure laminates or backed veneer and give a very good bond. It is important to note that contact adhesives should not be used on unbacked veneer because they will not resist the veneer movement, resulting in cracking and delamination. It also important to note that there is very little chance of movement once the substrates are offered up to each other.
Products suitable for this application are Aro-Bond 693® which is a hand applied version, or Aro-Bond® 680 which is a spray applied version.
If you would like to discuss these options in more detail, please contact us on 0117 971 1364 or email us on firstname.lastname@example.org.