My wife prepares lunch for me every morning. After eating it on my desk, I typically wash the lunchbox and utensils in the company's kitchen. I have noticed that it is very difficult to remove the oiliness from the plastic containers (think Tupperware, but also harder plastics that look like polycarbonate): I need to rub the detergent-soaked sponge extensively and rinse with very hot water, several times. This does not happen with glasses, porcelain dishes or metal utensils like forks.
In other words, all the plastic containers I have come in contact with seem to be quite lipophilic.
Is this because edible oils and plastic are chemically "similar" (i.e., both contain long-ish chains of hydrocarbons), or is there another reason that I am missing?