This Small Business Innovation Research Phase I project will investigate mesoporous silicate nanoparticles specifically functionalized to act as char-forming fire retardants (FR) for structural plastics. The particles provide substantial improvements over conventional FR agents that are environmentally undesirable (e.g., halogenated hydrocarbons), cost intensive (e.g., molybdenum oxide), toxic (e.g., antimony oxide), cosmetically unattractive (e.g., red phosphorus) or that compromise mechanical properties (e.g., aluminum trihydrate and organoclays). The project provides an understanding of the factors that regulate the catalytic function of the mesophases in forming char, including the compositions of the framework walls, the framework pore structure and pore size distribution, the fundamental size and shape of the nanoparticles and the loading level of the particles in the polymer matrix. The char-forming properties of the mesophases are manifested as a reduction in the peak heat release rate (PHHR) and a longer time to reach PHHR, as determined by cone calorimetry. Unlike other FR agents, mesoporous silicates nanoparticles provide added value by enhancing the mechanical properties of the final composite at low loadings (< 10 wt%). The combination of FR protection, improved mechanical performance, and particle dispersability without the need for organic surface modifiers presage a paradigm shift in polymer additives technology.
The broader impact/commercial potential of this project is the development and commercialization of nanoparticles that enhance the properties of structural polymeric materials. The proposed commercialization effort focuses on FR additives for plenum-rated wire and cable applications and high density flexible circuit boards. The global insulated wire and cable market is worth more than $100 billion with plenum-rated cable accounting for approximately 20% of that market. This segment is expected to see global growth of 5% CAGR as new construction demand accelerates. The volume of polymer used for wire and cable insulation in the US in 2008 is estimated to be ~100,000 tons. Thermoplastics constitute the largest market share with polyolefins (polyethylene) representing 41% of the total. The worldwide flexible circuit board market exceeds $7.4 billion and is expected to grow at an annual rate of 13.5%, reaching $16.4 billion in 2014. The current global annual demand for flexible circuits is ~ 39,000 tons. Our nanoparticles are the only materials known to simultaneously provide improved fire retardation, weight reduction, and decreased permeability while enhancing mechanical properties. This combination of properties for polyethylene and polyimide polymers provides a competitive advantage capable of producing $300 million in revenues by 2014.
Most polymers are flammable. To mitigate the risks associated with polymer flammability, national and international regulations, such as UL 94, The Standard for Flammability of Plastic Materials for Parts in Devices and Appliances, have been developed which specify that when plastics do burn, they do so in a controlled manner. To meet the dictates of these standards, flame retardants (FR, FR agents) are added to polymers in order to inhibit the initiation and/or spread of fire. To match polymer properties and processing requirements, a broad range of materials is used as FR agents, including a large number of halogenated materials, such as decaBDE. These materials are particularly effective FR agents, however, their use is being actively phased out (driven by regulatory changes and strong efforts by environmental groups, NGOs, OEMs, etc.) due to toxicity concerns. For example, the USA EPA announced the ‘decaBDE Phase-Out Initiative’ to eliminate the production, importation, and sale of decaBDE by 2013. Thus, the market has indicated a strong need for FR agents that meet the following criteria: efficient flame retardation; cost-efficiency; minimal impact to the mechanical and aesthetic properties of products; nonhazardous during production; minimal human and environmental toxicity; minimal leaching during product lifetime; minimal formation of hazardous substances during decomposition/incineration; and recyclability. The mesoporous silicate materials developed with NSF funding (NSF Award Numbers IIP-0822808 entitled "Automotive Nanocomposites" and IIP-1013281 entitled "Mesoporous Nanoparticle Flame Retardants") achieve this objective. This study found that when compounded with commodity plastics, Silapore™ particles (InPore Technologies’ trade-name for its mesoporous silicate materials) at low concentrations (less than 10% by weight) improve flame retardation of plastic materials. They also improve the strength of the plastics, which is something that other FR additives cannot claim. This means that plastic parts can be designed to have thinner walls, use less material, and ultimately cost less. The specific objectives of the NSF sponsored research were to chemically engineer mesoporous silicate particles so that they function as flame retardants for thermoset and thermoplastic plastics. Our project achieved these objectives: Our Phase I study included a glassy epoxy with physical properties suited for use in the electronics industry, two grades of polypropylene with different melt flow indices (based on customer interest), an electrical grade polyethylene, and a wire/cable grade of polyvinyl chloride. Testing showed that Silapore-polymer composites demonstrated a reduction is heat release rate (fire intensity) for all materials tested. Concomitant with the reduction in heat release rate was a near universal improvement in mechanical properties, which supports our value proposition to customers: improved flame retardancy with mechanical performance. In combination with other FR agents, low loadings of Silapore particles, typically 5-10 wt%, work synergistically with the other agents to provide improved flame retardation. In accord with industry best practices, Silapore particles used in combination with other FR agents are likely to meet the UL FR standard of V0 while providing the end-user additional benefits, such as improved mechanical properties, as compared to parts with just traditional FR agents.
