Wire & Cable Technology International - January/February 2008 - (Page 44)

New Magnesium Hydroxides Enabling Low-Smoke Cable Compounds by: Tong Chen and Alex Isarov J. M. Huber Corporation Huber Engineered Materials Division 251 Gordon Street Fairmount, GA 30139 USA www.huber.com dant wire and cable has been much limited compared to ATH, largely due to the higher cost of typical premium grades of MDH versus ATH has prompted continued industrial research and development, and as a result gradual commercial introduction of novel MDH materials suited for a range of wire characterized by a number of attractive performance attributes and features as listed below: • Unique particle size and size distribution combination allowing for optimized balance of compounding process and compound mechanical performance. heat and smoke production measured by cone calorimetry. • Improved MDH powder incorporation and dispersion into surface, resulting in enhanced overall compound property and performance. surface treatments. • Improved economics of using the novel MDH as compared to conventional premium grades. J. M. Huber Corporation has focused on developing these types of MDH products with continuing success in making available to FR cable compounders and cable producers a series of new MDH products with the above features. Vertex® 100 and Vertex 90 product lines recently commercialized by Huber are examples of such new synthetically characteristics of Vertex MDH products and their performance wire and cable compounds. From a Paper Presented at the 56th IWCS Conference™ in November 2007, www.iwcs.org With continuously rising industry-wide interest to favor the low-smoke and/or zero-halogen cable compositions, wire and cable producers are paying increased attention to the need for that are considered as environmentally friendly. The metal hydroxide family, which primarily consists of alumina trihydrate (ATH) and magnesium dihydroxide (MDH), has been among nature of being nontoxic and noncorrosive both during their use and throughout cable service life. Unlike other common functionality FR additive. One well-know performance trade-off of using the metal is the requirement for high loading levels of the hydroxide, typically ranging from 40% to 70% by weight in order to results in reduced material mechanical properties as well as creased processing viscosities. Such disadvantages associated with the metal hydroxides have from time to time outweighed especially when cable designs are geared toward lighter and more compact constructions while higher cable production throughput becoming more of an expectation than a desire. From a technical standpoint, ATH can be used in cable compounds that are made of certain thermoplastics such PVC Materials and Testing Magnesium hydroxide materials were investigated in EVA and PVC formulations representative of commercial wire and cable compounds. A description of magnesium hydroxide materials used in this study is presented in Table 1. The compounding was done on a Brabender lab mixer followed by sheeting out on a two-roll mill. The test specimens were compression molded. Unless otherwise noted, the EVA compounds described in this study were based on ethylene vinyl acetate co-polymer with 28% vinyl acetate content. Also study contained 70 phr of metal hydroxide and 45 phr of plastisizer (TOTM). All material testing was performed according to following ASTM procedures per the following: • ASTM E1354: Cone Calorimeter, 50 kW/m2. • ASTM E662 • ASTM D2863: Limiting Oxygen Index (LOI). • UL 94 vertical burn, 1/16" thickness. Several aluminum hydroxide materials were also used in this study. This historically high use of ATH is attributed in part to its wide availability and more importantly, to the lower cost of its use. Rising demands for better-performing FR wire and cable and for increased cable production rates have begun to thermal stability of beginning to decompose at around 220°C, or even at lower temperature when under mechanical shear. The thermal stability of ATH can limit compound processing and thus cable extrusion throughput even though ATH remains stable and intact under typical processing conditions for those thermoplastic polymers. In contrast to ATH, MDH offers a much higher thermal stability with its temperature of decomposition at around 340°C. This enables compounding and processing at higher temperatures than permitted for ATH, and thus can result in 44 Wire & Cable Technology International/January 2008 Results and Discussion Effect of Particle Size Characteristics on Fire Retardancy of Magnesium Hydroxide in EVA. Three grades of magnesium hydroxide (surface treated with vinylsilane) were used to http://www.huber.com http://www.iwcs.org

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Wire & Cable Technology International - January/February 2008 Editorial Wire & Cable Events Industry News Global Economy Drives Specialty Cable Demand Corporate News Change is Tough! Top Products of 2007 New Magnesium Hydroxides Enabling Low-Smoke Cable Compounds Straight From the Show - IWCS Conference™ A History of Long-Term Thinking Ensures a Pioneering Spirit Expediency of Roller Dies Application in Wire Drawing - Part 1 WireDrawing 101 Strain Rate Transforming Our Ideas Into Your Success Straight From The Show - Wire Southeast ASIA 2007 Capstans, Dancers, Accumulators Roundup Spotlight On Quality Control Pioneering Virtual Technology for Extrusion Electrically Heated Furnace Cuts Energy Costs/Reduces Carbon Footprint Machinery Accessories Materials Polymer Developments in the Cables Industry Wire & Connector Top Products of 2007 Just Load, Click and Print Superior Flame Resistance for Minimal Smoke, CO & Acid Gas High-Flex Round Cable Added to On-Line Design Tools Failed Bridge Cables Replaced With Smaller, Stronger Ones Advertisers Index Classified Advertising Internet Spotlight Editorial Index

Wire & Cable Technology International - January/February 2008

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