Acrylic is an extremely versatile material which is used in a wide range of environments. Acrylic sheeting is available in a huge range of variations, including; clear, coloured, mirrored, frosted and even with a brushed aluminium effect.
Extruded acrylic and cast acrylic are the two main types of sheet acrylic you will come across. Although they may initially look similar, the two have quite different properties and one is also much more expensive than the other.
It is important to be aware of the differences between the two so you can pick the type most suitable for your needs.
Extruded and cast acrylic sheets differ mainly in their thermal and chemical properties which are caused by the manufacturing process. There are also several other differences as outlined below which you may wish to consider when choosing acrylic sheet for your home DIY project.
Key differences you should be aware of when working with acrylic sheets:
Due to the way the sheets are made cast acrylic tend to have slight variations in the thickness of the sheet whereas extruded sheets are much more uniform, with next to no variation. This makes extruded acrylic ideal for vacuum forming or situations where more detailed precise shapes are needed.
Cast acrylic has an isotropic response to temperature meaning there is a maximum shrinkage of 2% in all directions. It may be important to note that acrylic expands and contracts at a much greater rate than glass. Extruded acrylic, on the other hand, shows differences in shrinkage depending on the thickness and direction of extrusion.
Benefits of Extruded sheets
Benefits of Cast acrylic sheets
Both types of acrylic benefit from being durable and long lasting, showing excellent resistance to natural aging. Most manufactures will guarantee against noticeable yellowing for approximately 10 years.
Often it may not be made obvious which type of acrylic you are buying, especially online. Cast acrylic can be as much as double the price of extruded acrylic so if nothing is mentioned and it seems cheap, the chances are it is extruded acrylic.
Thermoforming is the process of heating huge plastic sheets into a very high temperature and cooling them in the required format. Vacuum forming is a sub process or a type of thermoforming where vacuum is applied in between the molds and the plastic to create various shapes. Thermoforming has several advantages and disadvantages compared to the other plastic molding methods like injection molding. In addition to vacuum forming, several other methods like drape forming, twin sheet forming and pressure forming can be incorporated along with thermoforming to produce different kind of products. Several types of plastic can be molded in the method.
Disadvantages of thermoforming
1. Thermoforming is quite costly. Compared to other methods like injection molding, this method can cost up to 50% more.
2. Large plastic sheets are used in the method. They have to be fed into the rollers again and again. This leads to lots of extrusion.
3. The plastic street is stretched in the under pressure in this method. Hence the products formed using thermoforming break at a certain temperature.
4. Thermoforming uses more plastic than other methods. Nearly 10 to 20% more plastic is used to make any product in this method. This adds to cost and creates extensive wastage too.
5. Vacuum forming process done along with thermoforming does not give the required shapes sometimes. The whole process has to be repeated which is expensive as well as time-consuming.
Advantages of thermoforming
There are several advantages in using this method in spite of all these disadvantages.
1. Thermoforming is the only method in which huge plastic sheets can be molded into huge objects. All other methods are used for making small objects only.
2. Though the process is costly, the tools required for the trade or quite cheap. Injection molding machinery is nearly 33% costlier than the Thermoforming machinery tools.
3. Several different products can be prepared in the thermoforming machines. Only certain products can be prepared in other machines. Nearly all types of plastic can be used for the plastic. Other methods use only specific plastic for production.
4. Skilled labor to operate the thermoforming machineries are available in abundant. But, laborers capable of operating machineries of injection molding or vacuum forming are quite less.
5. Superior quality products using more plastic are formed in the method. Hence, they are more durable than the objects created through other local methods.
There are many more advantages in the method. Though costly and a bit time-consuming thermoformed products are preferred by most of the packaging industries due to their high quality.