Yes, it’s important to keep PLA products out of intense sunlight areas of warehouses (in or out of the packaging cartons). PLA has a relatively low glass transition temperature (typically between 44 and 63 °C). This is the temperature at which the molecular bonding starts to “relax” – don’t panic… it’s not melting, just relaxing. If the temperature increases it will move to a melting phase. PLA’s melt temperature is between 157 – 170 °C. This varies dependent on the thickness of the material and if it is bonded on cardboard (like coffee cups).
Note that CPLA is used to make our coffee lids and cutlery (CPLA is a harder and more brittle version of PLA). This has a higher melt temperature of 200 °C.
The most at risk PLA products are clear cups, clear lids and straws as these are thin walled PLA products. These are designed for serving cold drinks and are safe for use (all have SGS food certs). However, they are at most risk if stored in high temperature environments. Even things like a hot car in the summer could cause parts to soften and deform.