Lab Lessons—Wise Words From the Bench with Mukund Bhuta

Jul 1, 2011 | Contact Author | By: Katie Anderson (Schaefer), Cosmetics & Toiletries magazine
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Title: Lab Lessons—Wise Words From the Bench with Mukund Bhuta
aerosolsx propellantx VOCx alcoholx
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Keywords: aerosols | propellant | VOC | alcohol

Abstract: Ease of application has made aerosols one of the most demanded product forms in personal care and many innovative launches in this form, including dry shampoos, sunless tanners and sunscreens, among others, have been seen in recent years. Technologies continue to advance this product category, and Mukund “Mac” Bhuta, who has nearly 50 years of experience with aerosols, is responsible for a number of them.

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K Anderson, Lab Lessons—Wise Words From the Bench with Mukund Bhuta, Cosm & Toil 126(7) 526

Editor’s note: While formulating skills are built from a strong chemistry background, they are refined by years of experience. “Lab Lessons” features interviews with veteran members of the industry to share practical advice from the lessons they have learned.

Ease of application has made aerosols one of the most demanded product forms in personal care and many innovative launches in this form, including dry shampoos, sunless tanners and sunscreens, among others, have been seen in recent years. Technologies continue to advance this product category, and Mukund “Mac” Bhuta, who has nearly 50 years of experience with aerosols, is responsible for a number of them.

Bhuta began his career in 1962 at Pennwalt Corp., a major fluorocarbons manufacturer. As a chemist there, he worked to adapt aerosol products such as hair sprays, shave foams, industrial formulas and more with fluorocarbon propellants—and was quickly introduced to the ins and outs of the application. Bhuta was charged with selecting the correct valves, actuators, can materials and internal varnishes, and testing the finished products for compatibility, functionality, flammability, weight loss, etc. In the years following, he moved on to positions at Wyeth Pharmaceutical, Phillips Petroleum and L’Oréal USA, and each position taught him invaluable lessons he continues to pass on as an aerosols consultant.

C&T: How did you first become involved with aerosols?

When I started at Pennwalt, I knew nothing about aerosols and it took a few months to catch on. At that time (1957–1965), aerosols were becoming popular in the United States and Europe, so I was excited to learn about them from Allen Reed, my supervisor then. A valve system for an aerosol can had previously been developed (1931/1933) to dispense insecticide for soldiers in the Pacific during World War II to prevent mosquito bites [and potential malaria].

C&T: What is one of the main lessons you have learned while creating aerosols?

Always test the end product for compatibility, functionality and weight loss before launch. Compatibility tests look into interactions between the formulation and packaging materials such as aluminum and tin cans. These tests also indicate if the formulation is incompatible with the propellant selected, with tell-tale signs including separation and changes in pH, color and odor. Functionality studies check the can and valve system for issues such as clogging and problems with spraying. Weight loss studies determine the [spray-ability of] the product; if weight loss is high, the product will not spray because the propellant has leaked.

C&T: What challenges are faced by the aerosols industry?

The price of petroleum products is rising—costing more than alcohol products—so manufacturers prefer to develop water-based aerosol products. [However,] creating a water-based aerosol formulation can be difficult. Chemists interested in water-based formulas therefore seek information on propellant selection, can lining, handling, valve selection, etc.

In addition, regulations on aerosols are becoming more strict because chemicals such as alcohol and new propellants have been found to affect global warming; in fact, in Europe, manufacturers have stopped using such propellant systems altogether. The US Environmental Protection Agency (EPA) is also trying to cut down on the use of man-made chemicals such as alcohol in aerosol cans. Any man-made chemical is an organic compound, and all organic compounds are volatile (i.e., alcohol). Currently, the EPA recommends formulating with only 55% volatile organic compounds (VOCs) in hair sprays, but the agency is considering reducing this number to 40%.

C&T: How does higher water content and lower alcohol content impact hair spray formulas?

When one uses too much water in the formula, the spray is wet—and consumers do not want wet hair when they use hair spray. This can be controlled by selecting the right combination of valve stem and opening system, the right actuator opening, or by inserting a vapor tap opening in the body of the valve.

C&T: What personal care products are difficult to put into aerosol form?

Powdered aerosol formulations can be challenging because the powder [i.e., talc] is not soluble in the propellant or any solvent, and the propellant is cold—its boiling point is less than zero. So when the propellant is put into the powder, the formulation cakes at the bottom of the can. Then when it is sprayed, the powder gets stuck in the opening of the valve and clogs. One therefore must use the right combination of propellant and anti-caking agents, which can be determined by the compatibility study.

C&T: What other components are important for the creation of an aerosol?

The internal varnish or the coating/lining of the can is important. Coating prevents the formulation from attacking the metal. Chemists must conduct complete compatibility studies (60 days at 45°C) to determine which lining should be used, and each and every lining should be tested; [one should not depend on the results from just one lining]. Both testing and experience can help chemists in choosing the correct one.

C&T: What was one of your biggest mistakes when working with aerosols?

When testing aerosols, one must put the can in a hot water bath to increase the propellant vapor pressure of the finished product to determine whether the can is crimped properly, the valve system is not damaged during gassing, etc. As the propellant vapor pressure increases, the temperature inside the can increases. I once tried to pick up a can bare-handed and it blew up in my hand; I had to get 40 stitches. While the can was defective, I should have followed safety protocol and used tongs.

C&T: What else have you learned in terms of aerosol safety?

Liquefied petroleum gas propellants are flammable, so a test is used to determine how flammable they are and subsequently, which [caution] label to print on the can. If there is no flame, [no caution label is required] whereas flame size determines a “combustible”, “flammable” or “extremely flammable” label. I once was performing this test and forgot to put a mask on my face. It backfired and burned my eyebrows and hair.

C&T: What aerosol-specific regulation do you see broken most often?

The US Department of Transportation mandates that every aerosol can be passed through a water bath to achieve 130°F inside the can. If the crimp [sealing the can] is not closed properly or the can is defective, bubbles form in the water bath. The water used for this test then becomes waste water and must be destroyed with the proper waste management authorities rather than dumped into the sewer. Some companies bypass the water bath because it costs money to dispose of the waste water. Also, some use less water for the test, which is a problem because the can must be immersed. Finally, some companies do not use the right dwelling time; 2–2-½ min is necessary to achieve the right temperature.

C&T: What innovation do you see on the horizon for aerosol formulations?

Interest has grown in bag-on-valve systems due to VOC regulations. This innovation involves a bag made from four different layers of polyethylene terephthalate attached to a valve. A simple hair spray is placed in the bag while the propellant is placed around the bag in the can. This way, the propellant never contacts the hair spray and it is not sprayed from the product. The pressure increases outside of the bag, releasing the contained product.

C&T: Besides your consulting work, what are some of your hobbies?

I like reading about new aerosol developments and writing internationl safety procedures for aerosols. I also travel and give seminars about aerosol safety.

C&T: What do you find novel about aerosols?

Aerosols are convenient, and we are spoiled human beings. The aerosol industry is challenged every few years but the industry continues to come up with answers. Aerosols are here to stay.