Hello again all you plastic pellet fanatics! In this month's blog post we will discuss some of the major plastic pellet properties to consider when designing and fabricating a weighted blanket. While we do not have the time or space to consider all factors, this will summarize many of the more common concerns of customers.
I suppose one of the chief concerns we hear when making weighted blankets is the cost of the pellets. These little babies are not cheap, and so careful consideration of cost factors is essential. You may be wondering why we lumped bulk density with cost considerations? The answer lies in a property we call "yield". Yield in this case is defined as the cost of the pellets per square foot of a blanket when it is finished. From previous blog posts you know that the difference between the weight per cup (or bulk density) of different pellet types can be extreme. For example, the bulk density of our clear virgin pellets is approx. 5-5.5 oz/cup. Our white heavy pellets weigh in at a whopping 11 oz/cup! The is about twice as heavy per cup!!! On top of this, the white heavy pellets are less expensive due to the additive which makes the pellets so heavy. As a result, the yield is much better using the heavy white pellets. Another way of looking at this is to think about the number of pellets needed to get the same weight into the blankets. Due to the large difference in bulk density, we only need about 1/2 the number and volume of pellets when using the white heavy pellets. This is the reason they are so cost effective.
Another key consideration when choosing a filler for blankets is the desired thickness or volume of the blanket. Due to the heavy nature of the white pellets, the end product will be less bulky vs. the clear virgin pellets. If you are considering a blanket designed more for the winter months, you might consider using the clear virgin pellets to get a thicker blanket with a little more insulating power. For summer use, you might consider our heavy white pellet. For all around use, you might consider mixing the two products! Remember, the heavier the pellets in terms of bulk density (oz/cup) the thinner will be the blanket.
While we are on the subject of thickness and volume we might as well talk about the "softness" factor as well. Plastic or poly pellets come in different densities. As we discussed in our blog post "How much do I need?", density can be described as how close the molecules are packed together or how tightly they are packed. The closer or tighter they are packed, the harder the pellet and the higher the density in most cases. Therefore, if you want to use a softer plastic or poly pellet you will want a lower density product. The trade off is that you will need to use more of them to get the same weight as the lower density usually means a lower bulk density (weight per cup) and a bulkier blanket. The "feel" and texture of the blanket will change with the density and bulk density of the plastic or poly pellets.
Some of our customers ask us about the durability of the pellet types. The context of the questions range from washing and drying of the blankets with the pellets all the way to stability with normal or excessive wear and tear. Suffice it to say that while all pellets are not the same, we do not sell a product which we believe will fall apart in a blanket with normal wear and tear. Also, all of our pellets will stand up to washing and drying unless otherwise stated in the pellet descriptions. Having said this, it is clear that our clear virgin pellets are more durable than the heavy white pellets, which are softer and easier to crush or fragment. This is due to the heavy additive in the heavy pellets. This is also the reason you will find some slight dusting with the heavy pellets. Some of our customer rinse the heavy pellets before using them in order to remove this residue.
Once again, we do not sell anything that is offensive or objectionable when it comes to the old sniffer! Having said this, it is also clear that all polymer (plastic) based products have some sort of odor. Due to the lack of additives in our clear virgin product, these pellets are almost free of any odor from residual monomers (see previous blog posts). Our heavy white pellets have a more detectable odor, albeit minor. It is also important to note that any odor will dissipate over time. Most cannot detect an odor after the blankets are assembled. Also, due to the softer nature of the white pellets, they are more stable and hence a little cleaner than the white heavy pellets.
Please be careful that you do not choose a pellet cut which we call a "strand" cut for your blankets. The reason for this is that these pellets are cylindrical in form and have some sharp edges where the strands have been cut into the small pellets. These sharp edges can have a "cutting" effect on the blanket and create holes with frequent use. For this reason, we only use pellets with smooth geometry either in some sort of spherical or oval geometry. Our clear virgin pellets are generally described as being spherical and our heavy pellets are generally donut shaped with the hole filled in! Remember, NO SHARP EDGES PLEASE!
These are just a few off the more common pellet considerations when making a weighted blanket. There are many more. Call us with any questions as our phone line is willing and waiting!!! Most of all....HAVE FUN!