Why do water droplets seem to stay on plastic tupperware more than other materials after you wash them?
In: Chemistry
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My assumption here is that you are referring to a dishwasher appliance. The dishwasher uses a heat dry cycle, but the plastic that the tuperware is made out of does not retain that heat as long (less mass) as ceramic dishes or metal pots and pans so the water that is on it does not evaporate as quickly. There may also be more factors involved, such as there is more water that sticks to the plastic after rinsing compared to metal or ceramic.
> After a dishwasher cycle, the plates and glasses are usually dry, whereas plastic boxes and cups remain wet. The difference is due to the different materials’ ability to absorb heat, also known as heat capacity.
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> Porcelain, glasses and cutlery have a much higher heat capacity than does plastic, while glasses, porcelain, and cutlery generally also consist of thicker materials than plastic, and can hence contain much more heat.
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> Plastic is also a relatively poor heat conductor and so the thermal energy is not passed effectively to the surface. Porcelain, stainless steel and glass are good at conducting heat, so they can make the last water evaporate from the surface.
https://scienceillustrated.com.au/blog/science/physics/why-doesnt-a-dishwasher-dry-plastic/
The answers about evaporation being slower on plastic are correct.
My only comment on this is that the stream cycle on dishwashers helps dry plastics because it reduces the size of the droplets so they will dry faster.
Tupperware also has a texture to it that may not allow water to run off like it would on a smooth ceramic/glass surface.
Everything in a dishwasher heats up to the same temperature. The plastic pieces require less energy to heat up to that temperature so they also release less energy as they cool down.
I think that this is due to surface roughness which makes it harder for water droplets to slide off them and down the drain. I believe that the continuous use of plastic tupperware induces scratches on its surface. Hundreds of thousands of scratches that accumulate over-time.
Imagine if you shrink into the granular level, small enough to stand on a plastic tupperware bowl like it’s a massive skate park. You have a skateboard and you’re skating down this bowl when it’s brand new! The floor is shiny and smooth, you just fly down the bowl from one side and fly up the bowl on another. Now imagine you go back to regular size, go about your days, use the tupperware with stainless steel forks, knives, spoons, and wash that bowl with a rough deep cleaning good ol’ sponge… the one that has a green rough Scotch-Brite on one end. You then shrink and go for another round of skating at your little tupperware made park. Imagine how slow will you go down the one side of the bowl, and how many times your skateboard wheels will get caught on the creeks and rough terrain the bowl has now become. That also is the case with water droplets.
In contrast, porcelain plates are harder to scratch, and skating down them after months of use wouldn’t be as rough as doing so on tupperware. Water droplets would still slide easily off of it and down the dish drying rack even after so much scotch Brite and silverware abuse.
This is an objective hypothesis. I’d test it. I’d bring two identical pieces of tupperware, use one and keep one as a reference sample. After a few months of using one of them, I’d then wash them both with just water and observe if/how they dry out differently.
**assumptions:**
1. you’re drying dishes in a dish rack and after washing them by hand
2. capillary and surface-induced forces by the lips and indentations found on the tuppwerware’s cover snap-on designs are negligent. As in, the little lip sticking out of the rim of the tupperware bowl doesn’t cause any water droplets to get stuck.
Does this make sense?
My 1997 dishwasher would dry everything completely. The newer more energy efficient dishwashers dont dry plastic because they are not as powerful and the other reasons stated in this thread.
I feel like these answers are incomplete. I would expect the tendency for water to bead on plastics (it is a petroleum product) has a greater impact than how hot the item itself is. If the water can never run off, it will always be wet.
This would explain why dryer addictives make things “dry” better.
The answer is “heat capacity” or the ability to store heat. Think of the following: you heat two things to a hot temperature in an oven: an iron pan and aluminum foil. Even though both have the same temperature, you can immediately touch the aluminum foil with your bare hands, whereas the iron pan could be used to cook a steak, so you shouldn’t touch it. This is because the pan has much higher heat capacity and thus can transmit a lot more energy from the same hot temperature than the aluminum foil. Now, the same happens e.g. with plastic containers and glas in a dishwasher: They get heated to the same temperature. Whereas glas can easily transmit enough energy to the water droplets on it to make it evaporate, and thus it is dry afterwards, the plastic cools down faster and doesn’t have enough energy to evaporate all water droplets.
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