Back in the late 19th and early 20th century, local governments and car manufacturers experimented with a lot of different materials for number plates, ranging from porcelain to metal and even pressed soybeans. However, after numerous trials and errors, both the public and private sector eventually settled on acrylic to manufacture number plates.
Acrylic is a synthetic resin manufactured from the derivatives of acrylic acid (CH2=CHCO2H), which is typically found in the rumen fluid of sheep and marine algae. Chemists have known of the process to create acrylic since the middle of the 19th century. However, its practical application was only discovered in the early 20th century following ground breaking research by chemical company Rohm and Haas (known today as Dow Chemical) under the supervision of its founder, Dr Otto Röhm. By mid-20th century, stable forms of polymers derived from acrylic esters became cost-effective to manufacturer, and it was quickly latched on by car manufacturers.
Acrylic polymers are highly versatile, and can morph into various compounds when combined with other chemicals. The resulting compounds are usually durable, flexible and heat resistant. They can also be made transparent without any loss of tensile strength. As a result, over the last half century, acrylic has been used in a wide range of industries, ranging from aeronautics (windows) and submarines (periscopes and port windows) to construction (windows and skylights).
Acrylic has multiple properties which makes it perfect for number plates. These properties include:
Acrylic fares exceptionally well even under extreme weather. It will not crack or become compressed even under rapidly changing temperatures. It won’t blink an eye (if it has one) even if it was exposed to sunlight after being drenched by rain on a daily basis.
Acrylic is capable of reflecting low levels of light from a wide spectrum. As such, the reading visibility (even for infrared ANPR camera) remains high even under low lighting conditions.
Despite its tensile strength and lightness, acrylic is quite easy to shape and mould. With the application of just a little heat, acrylic can be shaped into various sizes. This reduces manufacturing cost, as well as packaging and delivery costs.