Yes, ASTM D570 is used to determine moisture/water absorption of a plastic. Typically, our suppliers provide both 24 hour and to saturation percentages by weight gain.
hello. I use LDPE recycle material but i always face issue with moisture. most of the time i dry them for 2 hours in 110°C then they become dried out but some of them won't dry. even they are same material LDPE. so what is the solution ? how can i make them dried
Hello and thank you for your question. Moisture absorption is typically expressed by % weight gain....but everyone wants to know what does this mean for dimensional increase. Unfortunately, there is no clear answer and perfect formula to calculate the dimensional growth from moisture. However, nylon is one of those materials that is susceptible to moisture with up to 7% increase in weight gain. There is a common estimate for nylon....the worst case percent change in dimension is equal to (% moisture uptake) x 0.3%. As an example, 5% moisture gain by weight (x 0.3%) equates to 1.5% dimensional increase. As mentioned, this is not perfect, but it can be used as a good worst case estimate.
How could a part that will absorb moisture and be out of spec even be useful? After removing it from the bag and installing it won't it just go out of spec in the machine? Where is 0% humidity a thing?
Hello Garrett. Believe it or not, this is very common with even the most highly engineered parts. We see designers sometimes specify tolerances very tight with polymers...often times probably tighter than they need to be. If the polymer specified is susceptible to moisture pick up, packaging is important in order to ensure the parts pass the customer's incoming inspection....or even to ensure that they fit upon installation. The parts should be packaged to avoid that moisture pick up while possibly sitting on the shelf for months or years. To your point, once installed if they are exposed to moisture, they may swell a bit (sometimes only a .001"...sometimes more) depending on the material and the environment. These are all things that need to be considered when engineering, specifying, and using plastics. Certainly can be challenging....but usually is nothing that cannot be overcome for most tolerance needs and applications. Thanks for your comment.
Great Video!! Incredibly helpful.
Thanks You
Great video, thank you
Glad you liked it!
can I use ASTM D570 to determine the moisture absorption? is it the same with water absorption?
Yes, ASTM D570 is used to determine moisture/water absorption of a plastic. Typically, our suppliers provide both 24 hour and to saturation percentages by weight gain.
hello. I use LDPE recycle material but i always face issue with moisture. most of the time i dry them for 2 hours in 110°C then they become dried out but some of them won't dry. even they are same material LDPE. so what is the solution ? how can i make them dried
Hello! I wonder if moisture is truly your issue. LDPE is known to have extremely low moisture absorption, typically
Hello help me solve this
let's consider plastic absorbs 2% of water. how to calculate the dimension of that plastic material after water absorption.
Hello and thank you for your question. Moisture absorption is typically expressed by % weight gain....but everyone wants to know what does this mean for dimensional increase. Unfortunately, there is no clear answer and perfect formula to calculate the dimensional growth from moisture. However, nylon is one of those materials that is susceptible to moisture with up to 7% increase in weight gain. There is a common estimate for nylon....the worst case percent change in dimension is equal to (% moisture uptake) x 0.3%. As an example, 5% moisture gain by weight (x 0.3%) equates to 1.5% dimensional increase. As mentioned, this is not perfect, but it can be used as a good worst case estimate.
How could a part that will absorb moisture and be out of spec even be useful? After removing it from the bag and installing it won't it just go out of spec in the machine? Where is 0% humidity a thing?
Hello Garrett. Believe it or not, this is very common with even the most highly engineered parts. We see designers sometimes specify tolerances very tight with polymers...often times probably tighter than they need to be. If the polymer specified is susceptible to moisture pick up, packaging is important in order to ensure the parts pass the customer's incoming inspection....or even to ensure that they fit upon installation. The parts should be packaged to avoid that moisture pick up while possibly sitting on the shelf for months or years. To your point, once installed if they are exposed to moisture, they may swell a bit (sometimes only a .001"...sometimes more) depending on the material and the environment. These are all things that need to be considered when engineering, specifying, and using plastics. Certainly can be challenging....but usually is nothing that cannot be overcome for most tolerance needs and applications. Thanks for your comment.