Light Diffuser heat resistant?

The white grating we use a lot for egg tubs that's meant to diffuse light from a flourescent bulb - how much heat can this tolerate? Could I put a 45 watt halogen heat bulb fixture on one or would it melt through?

What type of plastic is it...?

"Various melting points of different types of plastic:

The melting point of HDPE (High Density Polyethelyne) is about 130 ºC
The melting point of LDPE (Low Density Polyethelyne) is about 110 ºC
The melting point of PET (Polyethylene terphthalate) is about 250—260 ºC
The melting point of PP (Polypropylene) is about 160—170 ºC
The melting point of PS (Polystyrene) is about 70—115 ºC
The melting point of PVC (Polyvinyl Chloride) is about 75—90 ºC"