Maintenance-Free Park Signs

Thursday, December 22, 2011

Getting to know what your sign is made from!

As a custom fabricator of recycled plastic signs, Park-Signs.net get a lot of questions about the material we use. Naturally so, it is a relatively new material system which is gaining popularity because of its maintenance-free properties.  So how does one take recycled plastic like milk jugs and turn it into an engraved plastic sign? Well here is a little insight into the manufacturing process.
Various Color Combinations for HDPE sheeting.



RAW MATERIAL
To give you a better understanding of the process, I will first start by providing you with some information on the materials involved in making the HDPE Sheets. 

There are two material streams that are utilized when making HDPE plastic sheeting which are then used in the manufacturing of our customer signs. There is virgin plastic which is just another term for a plastic that does not contain any recycled content. You could think of it as first generation plastic. This typically comes in pellet form and is white to off white in color. This type of HDPE is used in lighter colors and in whites because, often the recycled plastic contains other materials that do not get sorted out when they were processed at the recycling center. These contaminants can cause discoloration and be seen pretty easily in light colors. The other material stream is post consumer (milk jugs, plastic bottles, hula hoops) and  or post industrial recycled content. The best source for this application is milk jugs and plastic bottle because of the pigmentless colors. Fellow recyclers would be familiar with it indication as a #2 plastic.  

Of course there is a number of other additives that provide the product with some of it great attributes. The most important of these might be the UV Stabilizers. This additive does two things. One, it helps prevent the Sun's UV rays from breaking down and deteriorating the plastic. Two, it prevents those same UV rays from fading or bleaching out the plastic pigments. 

THE PROCESS
In order to manufacture the three layered plastic sheeting, companies use a process referred to as extrusion. And if you have ever seen someone make sausage, it is a similar concept. I know, not quite the industrial example you might have been looking for but I think it gets the point across. Or the Play-Doh machine where you would stuff the Play-Doh in one end and squeeze it out the other into whatever shape you had attached to the end where it comes out.  So hopefully that painted the right picture. Again, a little elementary but the point is illustrated. 

This particular extrusion process in called co-extrusion because involves two separate extruders that work at the same time. As you can tell from the picture at the top of this entry, there are three different layers of plastic, which come together in the plastic's molten state to produce a plastic that can never delaminate, which is a huge plus when it comes to the durability of the product. Before these plastics are made into sheet form they are fed in pellet form, into the extruder's hoppers that funnel the plastic, along with any additives into the core of the extruder, or the barrel. This is where the magic happens....or the melting. Inside of the barrel a screw is housed which produces heat by rotating and causing friction and moves the plastic down stream and eventually out of the extruder. There are also additional heaters outside of the barrel which aide in helping melt the plastic to its optimal temperature. Once the plastic has been homogeneously mixed together, distributing color and additives evenly, it continues it's trip from the hot to cold side. 

When passing from the hot (barrel & screw) to the cold (cooling tanks) it goes through one very important part of the process.  This is where the molten plastic gets its shape.  The molten plastic passes through a die which is formed to shape whatever specific dimension the sheet will be extruded in.  Typically in this industry to yield to a four foot width.  It is a continuous flow of the newly formed plastic until it meets it's specified length further down the conveyor belt and is cut.  The material is then left flat and cooled until ready for storage and eventually shipment.

That is a very technical description of how the plastic sheets we utilize are made.  In the future we will focus on other characteristics that make this such a great product to use for any signage application.  We will also focus on some interesting field results.  Hopefully sharing with you some success stories!

Til next time friends!

Dave