And the result?
It’s FoodSaver Vacuum Sealing plastic boxes.
http://www.foodsaver.co.uk/accessories/foodsaver-set-of-3-lunch-and-leftover-vacuum-sealing-lunchboxes/T020-00024-IUK.html
I don’t understand how this had happened, if it could resist heat, why melted?
The grease/oil in the food super heated, microwaves work by heating
Iiquids.
Just a precision, this happened after the dish washer, not the microwave.
I kind of agree with JMat. Most so called microwaved food only is good enough to withstand boiling water temperature. However, I have melted microwavable container resulting a small fire/smoke.
Wow! That!
Interesting. As for my case, I thought micro-wave is hotter than the dish washer. But it doesn’t seem so in this case.
Ah, I see. It happened after the dishwasher, you said. I wonder … do you think it may has more to do with the dishwasher detergent? Dishwasher detergent is known to be more aggressive compared to typical hand dishwasher liquid. I cannot imagine a machine dish washer able to heat up much higher than boiling water. So, if your plastic lunchboxes are safe up to boiling water, then the only thing I can see is chemical issue, not temperature.
Good to know. I think it wasn’t the first time I put the box in the washing machine, but the difference was, the box was quite oily and dirty this time.
Another possibility could it be the dryer in the dishwasher?
Written on the box, you can read, dishwasher safe on the top rack.
Anyway, no plastic boxes in the dishwasher from now on.
Was it on the top rack?
Their FAQ says dish washer top rack only and microwave safe for re-heating only, not for cooking
I couldn’t be 100% sure, but I think so. I just used it to reheat in microwave, I remembered it was alright after eating, but I was too lazy to wash it because it was oily. When it came out after washing, at first I thought the machine didn’t clean it correctly, but then I see the “stain” was etched into the plastic.
My machine’s hot cycle is 167ºF / 75ºC.
Yeah, it’s the dry cycle that superheats the oils on the plastic the wash cycle didn’t get clean. Tomato sauce does the same thing.
My trick is to add a little Dawn soap and water, pop the lid back on and give it a good shake and let it sit in the sink for a while. Then a quick wipe down with dishcloth before putting it in the dishwasher. It’s not too much of a pain if you’re using Dawn anyway.
And you should be. 
I think the drying cycle is what damages plastics. I never use the heat cycle on my dishwasher. I live in southern AZ and currently the humidity inside the house is 2%. Residual heat from the wash cycle for a while, then crack the door open and it dries no problem. Sometimes plastic containers get warped anyway, but they’re not designated for reuse, mainly I clean them up to put in the recycle bin. I don’t want insects moving into my garage.
But I digress. I think it’s the heat drying cycle that ruins stuff in the dishwasher.
