Apparently it's a mortal sin to not use a heat protection spray on your hair before using a hair dryer, curling wand or hair straightener. According to www.cosmopolitan.com.au these sprays are multi-purpose:

• They provide a physical barrier for your hair like sunscreen does for your skin
• They moisturise
• They make your hair dry faster

You can read the full article here. They also have product recommendations to suit student budgets.