The term 'Laminated plywood' means different things to different people. The two most common ways to think about it are listed below.
1. Lamination can be defined as a process in which a number of sheets are heat-pressed and glued together to form a permanent bond. In the case of plywood, slices of wood (veneers) are placed over one another and bonded together using hot-press machines and adhesives. So plywood itself can be thought of as being laminated plywood.
2. Decorative laminate sheets (also called laminates) are glued over plywood to form a protective and decorative surface (e.g. Sunmica, Formica and other brands). Hence a plywood that has been finished by adding a decorative laminate surface can also be termed as 'Laminated plywood'.
This is an exhaustive article that discusses both of the above points and talks about several aspects of plywood, decorative laminates, and furniture, along the way.
Ok. So let's begin with the first point.
Plywood is made from thin slices of wood that are bonded together. These individual slices are called wood veneers and they are made by peeling the timber logs obtained from trees. Most of the veneers are manufactured using a rotary-cutting process. Rotary-cut means that the logs of wood are mounted on a machine, and are rotated along their longitudinal axis while a cutter peels of layers from the log.
The individual wood veneers thus obtained are then placed over one another to form layers. Each individual layer is also called a ply. Adhesives such as Phenol formaldehyde or Urea formaldehyde are then applied over each of these plies, and these layers are together sent into a hot-press machine to be laminated together under high pressure.
The machine presses and bonds all the plies firmly with each other, and this is how the so-called 'laminated plywood' is manufactured. The ready product is then sanded, marked and given finishing touches and finally shipped to the chain of distributors and dealers who eventually sell it to end customers.
Now, coming to the second point of 'decorative laminated plywood'.
The most common procedure in the making of customized laminated plywood furniture for our homes, shops, and offices, is that customers with the help of carpenters, buy plywood and decorative laminate sheets separately.
It's the carpenters job to know which kind of plywood will best suit the customer's requirements. Accordingly the correct quality, grade of plywood, sheet size and thickness has to be decided upon.
There is a wide variety of plywood available in the markets, ranging from commercial internal grade to external grade to Marine plywood. Other varieties such as Flexible plywood may also be required. Read this article to get more info about the various types of plywood.
And here are some general thumb rules for selecting plywood.
Using the right kind of plywood for every piece of furniture and decor, helps to increase the durability and saves on costs. e.g. For kitchen furniture such as kitchen cabinets, most carpenters will recommend External BWR grade waterproof ply, and for most other cases Commercial MR (moisture-resistant) grade ply is usually good enough.
Read this article for more information about the best types of plywood for furniture in India.
Selecting the decorative laminate
Deciding on the laminate surface (colour, design and texture) is a choice that the customer has to make, based on his/her likes and dislikes. Similar to the plywood market in India, the decorative laminate market in India also has a very large unorganized sector where locally made brands of laminates jostle for space with the products made by the reputed laminate companies of the country. Local goods are cheaper but may not be of the desired quality.
The general rule of thumb for selecting laminates for your plywood furniture, is that the thicker the laminate is, the stronger and better it will be. In addition to this laminates should be fairly scratch-resistant and waterproof. Fantastic looking designs and attractive colours are of no use, if the laminate cannot withstand wear and tear.
These high pressure decorative laminates (HPL) are basically a combination of paper and plastic. For making decorative laminates, a brown craft paper soaked and saturated in phenolic resins (which is plastic resin) is bonded together under high pressure and temperature, with another decorative paper soaked in a transparent melamine resin. The resins make the paper hard and brittle, while the pattern printed on the decorative paper gives the laminate its beautiful colours and design.
After that its upto Worksmanship
Once all the materials are purchased, the carpentry skills of the carpenters comes into play. The carpenters will cut the plywood and laminate sheets to required shapes and sizes, and glue the laminate over the plywood using standard wood glues. (The most commonly used adhesive in India for this purpose is Fevicol). After some more joinery work, the furniture is ready.
As a side-note, the laminate choice should be made wisely, because once the laminated plywood furniture is ready for use, it is very difficult and cumbersome to remove and change the laminate surface.
Here's an article about how carpenters remove laminate from plywood.
Prelaminated plywood sheets
The cost, time, and effort that is required to manually glue decorative laminates over plywood, can be avoided by the use of prelaminated plywood sheets which are nowadays manufactured by many of the major plywood companies. The process is the same, however instead of carpenters doing the job, companies do it much faster using their pressing machines.
Having said that, I have yet to come across any pre-laminated plywood sheets at any of the various plywood and laminate shops in Mumbai that I have visited so far. And while the product does have its plus points, I don't think that its really sells much. The major disadvantage of prelaminated plywood, is that the choice of colours and designs that the end customer has, gets drastically reduced.
Consider that decorative Laminates these days are manufactured in literally hundreds of unique designs, which include a wide range of colour shades, and artistic and geometric design patterns. There are high gloss laminates as well as those that have a textured surface that feels different to the touch than the regular plain ones.
This wide choice gets hampered in the case of prelaminated plywood, since the customers have to select only from the locally available ones, and since plywood sheets are quite bulky and take up a lot of space, there is a limit to how many such boards local dealers can stock in their shops.
Prelaminated particle boards are not the same as laminated plywood.
There has been an ever-increasing trend of buying trendy looking readymade furniture from shops. Most of this kind of furniture is made from prelaminated particle boards, or from prelaminated MDF (Medium density fibreboards). Customers should be aware that these are not a type of plywood.
Particle boards are much cheaper than plywood sheets, but the downside is they are not even half as strong, and the furniture built using these boards does not have a very long life. Again the choice in such a case, depends on customer's needs. There are people who want their furniture to last for generations, and there are people who have to think about and fulfill their short-term needs.
Here's a more detailed article about prelaminated particle boards vs. plywood