The Science of Sunscreens

making sunscreen with a three roll mill

Summer is already here. For many people, summer activities include spending long periods of time outdoors. Sunscreens and sunscreen cosmetics become hot sales!

There are two basic types of sunscreen lotions on the market, which are physical sunscreen (coat to the surface of skin to act as a barrier to ultraviolet rays) and chemical sunscreen ( penetrate the outermost layer of skin to absorb ultraviolet rays). Recently, people tend to choose nonchemical type sunscreens/ sunscreen cosmetics without addition of organic-based UV absorbents that could irritate their skin. The ideal and popular sunscreen would be a physical sunscreen using titanium dioxide or zinc oxide.

To make premium sunscreen, the key is uniform dispersion of titanium dioxide or zinc oxide particles. If the tiny particles are not thoroughly dispersed and form agglomerates in the cream, problems of whitening on the skin and insufficient UV screening protection will emerge. In industrial production of sunscreens, three roll mill plays an important role of giving sunscreen composition a homogenized texture. The three horizontally positioned rollers rotate in opposite directions at different speeds, pressing against each other and creating tremendous shear force in order to mix, refine, disperse, or homogenize viscous materials fed into the machine. The ingredients are distributed finely and evenly. The milled suncreeen exhibits better transparency and is more effective in blocking the harmful ultraviolet (UV) rays.

Concentration of
Sunscreens & SPF
Low
(SPF 2-5)
Moderate
(SPF 6-11)
High
(SPF 12-19)
Ultra High
(SPF >20)
Titanium Dioxide <4 % 8 % 12 % 20 %
Titanium Dioxide, Micronized 2 % 4 % 6 % 10 %
Zinc Oxide 5 % 10 % 15 % 25 %
Zinc Oxide, Micronized 3 % 7.5 % 12 % 20 %

Our lab staff came across an interesting sunscreen recipe on the internet and couldn't wait for the chance to try it out with our three roll mill. Here are the essential ingredients:

  • 8oz carrier. oil - jojoba, grapeseed, or almond are my preferences
  • 1oz emulsifing wax
  • Sunblocking agent - micronized zinc oxide or titanium dioxide.
  • Essential oils - coconut is classic

Here is our operation procedure:

  • Measure one ounce of wax into a microwave safe container.
  • Melt on high heat (approx 1 minute for me).
  • Add 8oz. oil, and blend well.
  • Add a few drops of essential oils for scent.
  • Add the wax/oil mixture to the powder.
  • Blend thoroughly.
making sunscreen with three roll mill

Learn more applications of three rolls mill: http://www.youtube.com/watch?v=imx_LWckkK4&feature=c4-overview&list=UUssJgtr2gEVI78_Ri1tkSAg