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coatings » coatings.mst.edu » v10i1 » newsletter v10i2
Volume 10 issue 2

What’s Happening at Missouri S&T:
(formerly UMR)

Short Course Dates

We will be offering "Basic Composition of Coatings"  March 25-29, 2013 (Spring 2013). The Basic Composition course is intended for new personnel in the coatings profession. It targets the components of coatings (resin, pigments, extenders, solvents and additives), testing and specifications, general formulation and manufacturing methods. Basic Composition is primarily a lecture course with several laboratory demonstrations.

We will be offering "Introduction to Paint Formulation"  May 6-10, 2013(Spring 2013) . This course is intended to give the person a fundamental knowledge of how to approach a starting formulation and troubleshoot it. This course involves both lecture and laboratory work.

We will be offering "Introduction to Coatings Composition and Specifications" July 17-19, 2013 (Summer 2013), course designed for the new coatings person in areas such as sales, marketing or production. The course was initiated by a number of raw material companies and distributors requesting a course with this format. This course is not as heavily technical as is our “Basic Composition of Coatings" and “Introduction to Paint Formulation" courses. The ?Introduction to Coatings Composition and Specifications" course is a two and a half day course which will discuss the types of coatings, the basic composition of coatings and the tests and specifications used by the industry. This course will allow the participant to gain the fundamentals needed to work in this industry and to communicate more clearly.

For more information see our web site at http://coatings.mst.edu and to register contact Catherine Hancock at cemv26@mst.edu or coatings@mst.edu or call 573-341-4419. **These courses are held on the Rolla Campus**

 


Technical Insights on coatings Science

General Fire Retarding Methods

Cassie Hancock, Graduate Research Assistant

Missouri S&T Coatings Institute,  Department of Chemistry

 In 2010 Residential fires alone resulted in 2555 casualties and over 6.5 billion dollars in damage. 1 A vast majority of materials including natural and artificial compounds, synthetic polymers, and inorganic compounds, including some with metals can enter into oxidation reactions. Oxidation reactions are exothermic, can occur very quickly, and are capable of self-sustaining. Due to performance requirements, cost and technology, flammable materials are not going to become obsolete anytime soon.  The need for polymers for both industrial and household use is continuously growing, but concurrently the fire safety requirements of these polymers are becoming stricter.  Consequently, the need for developing new, fire safe materials and providing existing materials with protection is on the rise.

The combustion process can be divided into space zones, each having its specific physicochemical processes: 2

  1. zone of the starting material
  2. heating zone
  3. zone of chemical transformations in the condensed phase
  4. preflame zone
  5. high temperature reaction zone in the flame
  6. zone of evolution of gaseous combustion products

To improve fire resistance any of the combustion zones can be targeted.

The least effective but simplest method to improve fire resistance is to reduce the amount of flammable compounds in the material.  Inert fillers such as glass fibers can be used to reduced the fraction of the flammable component in the material, but may in turn offer an adverse effect such as flame propagation, residual combustion time or decrease the self-ignition temperature.2

Fire-retardant agents are another method to enhance material fire resistance. Halogen-containing organic compounds are common fire retardants.3 The effectiveness of retardation increases in the order: F < Cl < Br < I.  Halogen retardants work in the gas phase of the combustion process. The combustion process is a free radical mechanism that is interrupted by the halogen-containing additive. The exothermic reaction is stopped, the system cools down, and the supply of flammable gases is reduced and eventually completely suppressed.4 Phosphorus compounds are also common fire retardants. The retardant can cause a layer of carbon to form on the surface of the polymer through the dehydrating action of the additive, generating double bonds in the polymer, and thus forming carbonaceous layer by cyclizing and cross-linking.4 Therefore, phosphorous based flame retardants act primarily upon the condensed phase zone by ‘coking’ the flame. Similar to phosphorus based flame-retardants, inorganic compounds form a hard protective coating during a fire. Intumescent coatings swell as a result of heat exposure, increasing in volume and decreasing in density. Upon heating of compounds like aluminum and magnesium hydroxide and salt hydrates, they decompose with a high endothermic effect, evolving inert gases such as CO2 and water.3  There are other elements used for flame retardants such as nitrogen. The ultimate goal would be to have a fire retardant or mixture of fire retardants that decompose at a lower temperature than the polymer.  Microencapsulated fire retardants are usually 50-200 microns in size. They are polymer shells filled with a liquid fire-retarding agent. Fire retardants with a relatively low boiling point of 100-200°C (carbon tetrachloride, dibromotetrafluoroethane) lower the capsule breakdown point. By the time the capsule breaks down due to the heat, the liquid is overheated and micro-explodes, sending the polymer away from the flame zone. Another method for fire retardation is nanoparticles.  Presently, carbon nanoparticles and nanosilicates are the most frequently used.3 The thermostability and structure of the polymer matrix is not compromised by these nanoparticles, however, when heated the particles can act as coke nucleation centers. The surface of the particles can be functionalized with organic flame-retardants.2

Along with the flame-retardants considered above, other factors that effect flammability can be controlled, such as polymer composition.  There are a multitude of approaches that can be considered when formulating a fire resistant material. Not only should the additive or polymer modification be considered, but also the location of the retardation of the material must be taken into account. Tragedies such as the destruction of the World Trade Center on September 11, 2001, emphasize the importance of ensuring the maximum fireproofing capabilities for the structural integrity of steel-based buildings. If the structural members of the building had sufficient intumescent coating , it may not have prevented the collapse of the structure but would have allowed more time for evacuation.  The use of intumescent coatings can allow the fuel to be consumed without sufficient heating of the support members to weaken the beams.

References

  1. U.S. Fire Administration Fire Estimates   http://www.usfa.fema.gov/statistics/estimates/index.shtm
  2. Berlin, A.A., Soros. Obraz. Zh., 1996, no. 9, pp. 57–63.
  3. Barbot’ko, S.L., Russian Journal of General Chemistry, 2011, Vol. 81, No. 5. pp. 1068-1074
  4. Tesoro, G.C.  Journal of Polymer Science: Macromolecular Reviews, Vol 13, 283-353, 1978

 

 

 


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