Plant based hair products

I am a Cosmetologist, and I am formulating hair products for the health-conscious person concerned with the ingredients in their hair products. I am looking for someone to do extensive research and write an article on their findings. Would you please explain why plant-based hair products are better, why sodium hydroxide is added to mostly all shampoos on the market today? Also include why companies use harsh chemicals in these porducts. Why do you not want to purchase hair care products with harsh chemicals? Explain and provide stat as well as links to your findings.