Silicone-Based Additives for Thermoplastic Resins Providing Improved Mechanical, Processing and Fire Properties R. Buch, W. Page and D.

Silicone-Based Additives for Thermoplastic Resins Providing Improved Mechanical, Processing and Fire Properties R. Buch, W. Page and D. Romenesko Dow Corning Corporation Midland, Michigan

Silicone-Based Additives for Thermoplastic Resins Providing Improved Mechanical, Processing and Fire Properties

R. Buch, W. Page and D. Romenesko Silicone-Based Additives for Thermoplastic Resins Providing Improved Mechanical, Processing and Fire Properties R. Buch, W. Page and D. Romenesko Dow Corning Corporation Midland, Michigan 48686 USA I. Introduction All plastics burn. Commodity resins, such as unmodified polyolefins, burn quite readily. Engineering resins are sometimes more difficult to ignite because of their inherent high-temperature features, but they also will burn. Fire-retarded materials often take longer to ignite, but they burn as well. In a fire, toxic gases often create as much hazard as the fire itself. Some statistics indicate more people die from carbon monoxide and smoke inhalation than from burns. Getting away from the flame is often possible, but the carbon monoxide and smoke generated can be difficult to avoid. In fact, carbon monoxide has an affinity for blood hemoglobin over 2 times that of oxygen and cannot be easily displaced by oxygen or carbon dioxide. In recognition of its potential effects, the U.S. standard for CO in the work place has been set at only 35 parts per million (ppm). 1 Because all plastics burn, additives that minimize their burning character have become a large business. Flame-retardant (FR) additives used in plastics include inorganic hydrates, intumescents (char formers), halogen compounds (often with metal oxide synergists), phosphorus compounds, and amino compounds. 2 A large number of products in many markets require flame retardants. Plastics manufacturers offer a wide range of materials to meet these needs. Typical applications are automotive, electronics, appliances, packaging, high-rise building construction, wire and cable, and transportation including mass transit, trains, airplanes, and ships. Consideration of a material for a particular application depends on how well the material meets the required physical properties and how cost effective it is. But while physical properties may determine whether a material is initially considered, its fire-retardant properties can determine its ultimate selection. In fact, fire-retardant properties are often the dominant feature demanded by the customer for use in critical enclosed areas where people concentrate and thus could have difficulty exiting in the event of a fire. However, physical properties such as impact strength and mechanical properties such as tensile and flex modulus are very critical to the function of the material in these applications. Manufacturers and compounders will not blindly sacrifice processability and performance; there must be a balance with fire properties. II. General Requirements for Fire Retarding Additives Over the years, many fire testing methods have been developed that specifically address the flammability of plastic materials. The American Society for Testing and Materials (ASTM) Committee D9, E5, D2 and others have developed standard methods that help characterize the burn properties of plastic materials. The ASTM book on Fire Test Standards details many such tests. 3 Underwriters Laboratories developed one of the most widely used fire tests, UL 94. 4-1 -

Silicone-Based Additives for Thermoplastic Resins Providing Improved Mechanical, Processing and Fire Properties Jurgen Troitzsch s handbook on plastics flammability discusses many aspects of fire testing of plastics. 5 Many additives are designed to reduce the fire time to less than 1 seconds in the UL 94 Flammability of Plastic Materials test to help a formulation earn a V- classification. This classification is currently required for many applications. Heat release rate is becoming recognized as an important parameter to be used to determine the hazard created when a material burns. Tewarson, Smith and Babrauskas have developed equipment to measure this property. 6 A commercially available measuring device for bench-top heat release measurements is the cone calorimeter. Well documented in ASTM E 1354-92 and ISO 566-1992, this device has proved valuable in understanding the effects of plastic additives, including their effect on heat release rate and the evolution of gaseous fire products such as carbon monoxide, carbon dioxide, and smoke. The cone calorimeter was developed at the National Institute of Standards and Technology (NIST, formerly National Bureau of Standards) of the United States Department of Commerce. A key developer, Vytenis Babrauskas, has published an excellent summary paper titled Heat Release Rate: The Single Most Important Variable in Fire Hazard. 7 Other papers and books provide a good discussion of heat release rate and calorimeters. 6, 8 III. Dow Corning Development Efforts In the early 197s, Dow Corning entered the less flammable liquid-insulated transformer market by developing a silicone fluid replacement for PCBcontaining askarel liquids in transformers. More recently, the company began a silicone additives project with the major goal of improving some fire performance properties of plastics without negatively affecting processing and molding characteristics. Other goals were to minimize the negative impact on mechanical properties such as impact resistance, tensile strength, and modulus often caused by some of the current commercial FR additives. Another goal of the project was to identify any other benefits of siliconecontaining additives. As a result of this program, silicone-based powders (DOW CORNING RM 4-781 and RM 4-751 Resin Modifiers) are now under development. These powders have been shown to significantly reduce the rate of heat release and the evolution rates of smoke and carbon monoxide of burning plastics such as polystyrene, polypropylene, polyethylene, polycarbonate, and others. These fire properties were measured on the cone calorimeter (ASTM E1354-92). DOW CORNING RM 4-781 and RM 4-751 Resin Modifiers, added to thermoplastic resins identified in this paper at levels typically of 1 to 5%, reduced the peak rate of heat release, evolution rate of toxic carbon monoxide, and evolution rate of smoke, as measured by the cone calorimeter. Significantly, these improved fire properties were often obtained without the need for halogen-containing fire retardants, which are a growing issue in Europe and, more recently, in the United States. These silicone additives also markedly reduce the peak rate of heat release and the peak evolution rate of carbon monoxide and smoke when used with other conventional FR additives, including halogenated compounds, phosphorus compounds, and water-evolving inorganics such as Mg(OH) 2. If UL 94 results are required, DOW CORNING silicone powders can sometimes be used synergistically with conventional FR additives. In several cases, the silicone powders improved formulations with respect to mechanical properties and processing of FR plastics. Details are provided in later sections of this paper. IV. Resin Compounding Procedures Used in This Study Extrusion Each resin requires different compounding procedures based on its properties. Resin manufacturer s recommendations are helpful in determining parameters and processes. DOW CORNING RM 4-781 Resin Modifier was formulated following manufacturers recommendations in a model based on STYRON 685D polystyrene (Dow Chemical). The DOW CORNING RM 4-781 Resin Modifier and polystyrene pellets were compounded by extrusion in a Haake System 9 TW1 extruder at the temperatures identified in Table I. TABLE I. Target Extruder Parameters Extruder Parameter Target Feed Zone 1 Temperature 18 C (256 F) Mixing Zone 2 Temperature 2 C (392 F) Mixing Zone 3 Temperature 2 C (392 F) Exit Die Zone 4 Temperature 2 C (392 F) Feed Metering None Extruder rpm 5 The extruder is a counter-rotating intermeshing twin screw extruder with each screw having a diameter of 19.77 mm (front) and 31.1 mm (rear) and a length of 331 mm. Either conveying or intensive mix screws are acceptable. Residence time is approximately 75 seconds. - 2 -

R. Buch, W. Page and D. Romenesko Injection Molding for STYRON 685D Polystyrene Using the following parameters, the chopped, formulated polystyrene from the extruder was injection molded using a BOY 15S injection molding machine. TABLE II. Target Molding Parameters Molding Parameter Target Drying Time With Vacuum None Mixing Zone 3 Temperature 24 C (4 F) Mixing Zone 2 Temperature 24 C (464 F) Nozzle Zone 1 Dial Setting 52 Mold Temperature Zone 1, Zone 2 43 C (11 F) Injection Pressure 18 psi (12.41 mpa) Screw Discharge Set Point 2. Mold Clamp Pressure 43 psi (29.65 mpa) Screw rpm 25 Shot Size Dial 36 The BOY machine mold makes small plastic tensile bars and an impact test bar. The impact test bar measures 1 /2 5 1 /8 inches (12 127 3 millimeters). For consistency, the top half of the bar was used. A notch was cut in the bar, and it was tested for impact according to ASTM D 256, Izod Impact. V. DOW CORING RM 4-781 Resin Modifier in STYRON 685D Polystyrene Improvements in Processing, Peak Heat Release Rate and Evolution Rate of Carbon Monoxide and Smoke for STYRON 685D Polystyrene Polystyrene is a difficult material to formulate for fire retardance. It depolymerizes to styrene monomer, a very flammable material. To understand the effect of various types of silicones on fire properties of silicone-modified polystyrene, we used the cone calorimeter. A viscous high-molecular-weight silicone fluid (2 Fluid from Dow Corning, 6, cst), a very high-molecular-weight silicone gum, gum-andsilicone resins, and DOW CORNING RM 4-781 Resin Heat Release Rate, kw/m 2 7 6 5 4 3 2 1 Qext = 3 kw/m 2 1% Polystyrene 99% Polystyrene, 1% DOW CORNING RM 4-781 97% Polystyrene, 3% DOW CORNING RM 4-781 6 12 18 24 3 36 42 48 54 6 Time, seconds Figure 1. Heat Release Rate of Polystyrene Modified With DOW CORNING RM 4-781 Resin Modifier Modifier (a methacrylate-functional silicone powder) were evaluated. For fire testing on the cone calorimeter, the impact test bar was cut to 4 inches (11 millimeters). Eight bars were placed side by side in an aluminum holder, placed in the cone calorimeter, and tested. The dimensions of the sample were 4 4 1 /8 inches. Results are summarized in Table III. The following theory was the basis for the tests: silica or resin having more RSiO 3/2 should provide more peak heat release rate reduction to the burning polystyrene than fluids or gums because silica acts as a barrier to incoming radiation. This theory is supported in Table III, which shows that as the amount of SiO 2 in the polystyrene increases, peak heat release and peak evolution rate of carbon monoxide and smoke are reduced. Addition levels of 15% proved excessive. Figure 1 shows that DOW CORNING RM 4-781 Resin Modifier added to this polystyrene at the rate of only 3% reduced heat release to 37% of that for unmodified polystyrene. Since DOW CORNING RM 4-781 Resin Modifier reduced the peak heat release rate for this polystyrene, it follows that the formation rate of carbon monoxide and smoke, two other potentially deadly components of a fire, may also be reduced. Figures 2 and 3 TABLE III. STYRON 685D Polystyrene Model Cone Calorimeter Data (Qext = 3 kw/m 2 ) % Peak Heat Release % CO % Smoke Sample, all in Polystyrene vs. Control vs. Control vs. Control Polystyrene Control 1 1 1 15% 2 Fluid (6, cs) 86 78 94 15% Silicone Gum 68 5 87 1% gum, 5% Silicone Resin 51 4 57 15% DOW CORNING RM 4-781 Resin Modifier 3 21 35-3 -

Silicone-Based Additives for Thermoplastic Resins Providing Improved Mechanical, Processing and Fire Properties Raw CO Analyzer Data.54.3.2.1 Qext = 3 kw/m 2 1% Polystyrene 95% Polystyrene, 5% DOW CORNING RM 4-781 Resin Modifier 1 2 3 4 5 6 Time, seconds graphically indicate the reduced levels of each. Addition of 5% DOW CORNING RM 4-781 Resin Modifier reduced carbon monoxide by 83% and smoke by 74%. Further evaluation has shown that additive levels of 3% or more resulted in the same reductions of the peak heat release rate and the peak evolution rate of carbon monoxide and smoke for polystyrene. The expectation was that specially formulated powdered silicone materials may provide similar results with some other plastics. It was also expected that these materials would potentially improve impact strength and processing of highly filled plastics. The remainder of the paper will show examples of other plastics and synergy with other FR materials. Figure 2. Carbon Monoxide Release Rate of Polystyrene Modified with DOW CORNING RM 4-781 Resin Modifier.1 x Extinction.54.3.2.1 Qext = 3 kw/m 2 1% Polystyrene 95% Polystyrene, 5% DOW CORNING RM 4-781 Resin Modifier 1 2 3 4 5 6 Time, seconds Figure 3. Smoke Extinction Rate of Polystyrene Modified With DOW CORNING RM 4-781 Resin Modifier VI. Effect of Halogenated Flame Retardants (DECHLORANE Plus) in High Impact Polystyrene (STYRON 438 HIPS) With DOW CORNING RM 4-781 Resin Modifier Sometimes, flame retardants, while slowing ignition, cause smoke and carbon monoxide yield rates to rise significantly. Tests were conducted to determine if DOW CORNING RM 4-781 Resin Modifier has an improved effect of reducing carbon monoxide and smoke of a plastic that uses a conventional flame retardant. DECHLORANE PLUS (Oxychem), a cyclic 65.1% chlorinated hydrocarbon, was used. Addition of DOW CORNING RM 4-781 Resin Modifier was expected to improve the peak heat release rate and the peak evolution rate of smoke and carbon monoxide of DECHLORANE Plus-modified STYRON 438 HIPS. The formulations used in this study are described in Table IV. Heat release rate data are shown in Figure 4. Note that addition of only 1% DOW CORNING RM 4-781 Resin Modifier reduced the heat release rate TABLE IV. Modified STYRON 438 HIPS using DECHLORANE PLUS and DOW CORNING RM 4-781 Resin Modifier Formulation A: Formulation B: Formulation C: Formulation D: HIPS DECHLORANE 1% DOW CORNING 2% DOW CORNING Control PLUS RM 4-781 RM 4-781 (%) (%) (%) (%) HIPS 1 78 77 76 DECHLORANE PLUS. 18 18 18 Sb 2O 3. 4 4 4 DOW CORNING RM 4-781.. 1. 2. Izod Impact (notched), ft-lb/inch 1.38.668.787.79 UL 94, 1 /8 inch HB HB V-1 V- 1 /16 inch HB V2 V-1 V-2-4 -

R. Buch, W. Page and D. Romenesko Heat Release Rate, kw/m 2 4 3 2 1 Qext = 3 kw/m 2 78% HIPS, 18% DECHLORANE PLUS, 4% Antimony Control Control + 1 or 2% DOW CORNING RM 4-781 Resin Modifier Modifier did improve the UL 94 results. These results support the possibility of a synergy between the silicone resin modifier and DECHLORANE PLUS. At many conferences, Oxychem has reported UL 94 data using another silicone material, General Electric s SFR 1. 9 Peak heat release rate reduction and reduction in the evolution rate of carbon monoxide and smoke in the Dow Corning study compliment Oxychem s data. 6 12 18 24 3 36 42 48 54 6 Time, seconds Figure 4. Heat Release Rate of HIPS Modified with DECHLORANE PLUS and DOW CORNING RM 4-781 Resin Modifier significantly. Halogenated flame retardants can sometimes increase both smoke and carbon monoxide yield rate because of less-efficient combustion, the primary mechanism for halogenated FR materials. Table V summarizes the fire properties of siliconemodified HIPS with DECHLORANE PLUS based on the formulations (A through D) in Table IV. The data in Table V indicate that HIPS burned and that DECHLORANE PLUS reduced the burn rate. However, the peak evolution rate of carbon monoxide and smoke increased dramatically. Addition of only 1% DOW CORNING RM 4-781 Resin Modifier dramatically reduced smoke and CO evolution rate to approximately the level of STRYON 438 HIPS without any additive. Further, the peak rate of heat release was dramatically reduced. Fire properties are often measured by UL 94 and limited oxygen index (LOI) testing. These tests are basically Bunsen burner type tests of fire properties. Modification of polystyrene with DOW CORNING RM 4-781 Resin Modifier had no effect on the UL 94 results, possibly due to the depolymerization mechanism creating styrene monomer. However, in Dow Corning s HIPS/DECHLORANE PLUS study, modification with DOW CORNING RM 4-781 Resin VII. Polyphenylene Ether Modified With DOW CORNING RM 4-751 Resin Modifier Dow Corning has also developed another powder product that has been shown to improve mechanical and heat release rate properties, specifically in the materials evaluated in this study. An important feature of DOW CORNING RM 4-751 Resin Modifier is that it is formulated to improve impact strength and processability of certain engineering plastics. DOW CORNING RM 4-751 is another resin modifier in Dow Corning s family of powdered plastic additives designed with epoxy functionality and intended to react with phenol functional engineering resins or resins capable of reacting with epoxy functional materials. For example, for processability, polyphenylene ether (PPE) engineering resins must be blended with polystyrene, which lowers the operating temperature of the blend. NORYL brand (General Electric) PPE blends combine PPE and HIPS. With Dow Corning s new powder technology, polystyrene can be eliminated from the blend system, and improved fire and other mechanical properties can be obtained. The PPE used in these formulations was Mitsubishi HPX-1L. UL 94 and LOI are widely used as flammability tests. These two tests run on polyphenylene ether blends provided the results shown in Table VI. LOI is the percent of oxygen in an oxygen/nitrogen mixture that will sustain burning. It is a test of extinguishment, not ignition. A change of 3% oxygen is often considered significant. Results of these tests appear to show a tradeoff between impact properties and fire properties. The 15% silicone-modified sample, Table V. Cone Calorimeter Data of Formulations in Table IV for STYRON 438 HIPS with DECHLORANE PLUS Modified With DOW CORNING RM 4-781 Resin Modifier % Heat Release Rate % Carbon Monoxide Rate % Smoke Rate DECHLORANE DECHLORANE DECHLORANE Material PLUS vs. Control PLUS vs. Control PLUS vs. Control HIPS Control (Formulation A) 2 77.6 67 DECHLORANE PLUS (Formulation B) 1 1 1 DOW CORNING RM 4-781 at 1% (Formulation C) 3.5 7 56 DOW CORNING RM 4-781 at 2% (Formulation D) 3.1 69 55-5 -

Silicone-Based Additives for Thermoplastic Resins Providing Improved Mechanical, Processing and Fire Properties TABLE VI. Flammablity Test Results on HPX-1L Polyphenylene Ether Blends Formulation UL 94 Vertical Burn Test 1 /8 inch Limited Oxygen Index LOI NORYL 731 PPE/HIPS Control Complete Burn-Vertical HB 25.6% Oxygen 85% PPE, 15% DOW CORNING RM 4-751 V-1 25.3% Oxygen 95% PPE, 5% DOW CORNING RM 4-751 V- 26.4% Oxygen 99% PPE, 1% DOW CORNING RM 4-751 V- 29.3% Oxygen Table VII. PPE Blends Improved Impact, Softening Temperature, and Fire Retardance Properties TMA 1 % Peak Heat % Peak % Peak Notched Izod Impact Softening Temp. Release vs. CO vs. Smoke vs. Impact Modifier in PPE ft-lb/inch (J/m) C ( F) Control 2 Control 2 Control 2 NORYL 731 PPE/PS Control 2.5-3. (133-161) 135 (275) 1 1 1 85% PPE, 15% DOW CORNING RM 4-751 7.9-8.6 (423-46) 195 (383) 33 3 29 95% PPE, 5% DOW CORNING RM 4-751 1.85-2.74 (99-147) NA 33 3 21 99% PPE, 1% DOW CORNING RM 4-751 1.-1.4 (54-75) 21 (394) 33 26 21 1 Thermal mechanical analysis. 2 By Dow Corning cone calorimeter. formulated for high impact strength, has significantly improved UL 94 results compared to NORYL 731. Samples with lower levels of silicone showed improved results for both LOI and UL 94. These data provide a significant incentive for those customers interested in non-halogen-containing flame retardants. Table VII summarizes impact and some fire features of DOW CORNING RM 4-751 Resin Modifiertreated HPX-1L polyphenylene ethers. The notched Izod impact results are shown in Figure 5. Note the significant increase in impact strength at 15% addition of DOW CORNING RM 4-751 Resin Modifier. Other physical properties are important to the decision to use flame retardants. One such physical property is dynamic mechanical properties over a wide temperature range. Figure 6 shows the flex modulus versus temperature of polyphenylene ether blends used in the previously discussed tests. Note the wider temperature range of DOW CORNING RM 4-751- modified HPX-1L PPE. This range occurs because polystyrene is removed and replaced by much smaller amounts of silicone, resulting in higher Tg. The change is significant because, until now, PPE has been reported to be very difficult to process without polystyrene. Also note that the ultimate flex modulus of NORYL 731 is nearly identical to the 1% DOW CORNING RM 4-751-modified PPE over the temperature range until the Tg of NORYL 731 is reached. The flex modulus of NORYL 731 then drastically falls, while the siliconemodified PPE remains relatively flat. Dynamic mechanical properties (flex modulus) of other polymers such as polycarbonate and polypropylene are not significantly affected by addition of 1 to 5% DOW CORNING RM Resin Modifiers over a wide temperature range. With the success of these evaluations, it seems appropriate to look at other plastic materials. Table VIII Notched Izod Impact, ft-lbs/inch of notch 1 8 6 4 2 Synergy at 15% Reference 9835-116-119 1 2 3 4 DOW CORNING RM 4-751 Resin Modifier in PPE, percent Figure 5. Impact Modification of PPE Using DOW CORNING RM 4-751 Resin Modifier - 6 -

R. Buch, W. Page and D. Romenesko E 1, GPa 3. 2.8 2.6 2.4 2.2 2. 1.8 1.6 1.4 1.2 1..8.6.4.2 NORYL 731 15% DOW CORNING RM 4-751 Resin Modifier High Impact PPE Amplitude (p-p) =.2 mm 1% DOW CORNING RM 4-751 Resin Modifier, 99% PPE Easy Processing -75-5 -25 25 5 75 1 125 15 175 2 225 Temperature, C The addition of DOW CORNING RM 4-781 Resin Modifier to polypropylene with 2% Mg(OH) 2 improved the already significant improvement in heat release rate. Similar results occur for carbon monoxide yield rate. However, the major issue of Mg(OH) 2-modified polymers is reduced impact strength. Table IX summarizes impact and cone calorimetry results. Note that the addition of a small amount of silicone powder to polypropylene filled with 2% or 3% Mg(OH) 2 nearly doubled impact strength back to the level of unmodified polypropylene. In the special case of 5% PP and 5% Mg(OH) 2, there was also a dramatic increase in impact strength. Figure 6. DOW CORNING RM 4-751 Silicone Impact Modified PPE Flex Modulus vs. Temperature 1 Qext = 3 kw/m 2 1% Polypropylene 8 summarizes the evaluations of polycarbonate, polypropylene, EVA, and various blends of these materials. VIII. Synergy With Nonhalogen Magnesium Hydroxide in Polypropylene Using ESCORENE 112 polypropylene as an example, formulations were produced at various levels of Morton International VERSAMAG Mg(OH) 2 and evaluated for impact strength as well as heat release rate via the cone calorimeter. The goal was to evaluate these for synergistic performance regarding fire and mechanical properties. Figure 7 illustrates the effect of Mg(OH) 2 and DOW CORNING RM 4-781 Resin Modifier regarding heat release rate. Heat Release Rate, kw/m 2 6 4 2 75% PP, 25% Mg(OH) 2 75% PP, 2% Mg(OH) 2, 5% DOW CORNING RM 4-781 65% PP, 35% Mg(OH) 2 with and without RM 4-781 2 4 6 8 Time, seconds Figure 7. Heat Release Rate of Modified Polypropylene Mg(OH) 2 and Silicone-Modified Mg(OH) 2 TABLE VIII. Cone Calorimeter Data for Silicone-Modified Plastics (Qext = 3 kw/m 2 ) % Heat Release % Carbon Monoxide % Smoke Material Rate vs. Control Rate vs. Control Rate vs. Control Polycarbonate (Dow Chemical) 1 1 1 99% PC, 1% DOW CORNING RM 4-781 57.17 4.86 38.39 95% PC, 5% DOW CORNING RM 4-781 4.38 23.26 44.34 Polypropylene (Exxon) 1 1 1 99% PP, 1% DOW CORNING RM 4-781 1. 89.6 85.48 95% PP, 5% DOW CORNING RM 4-781 55.4 39.6 77.4 92% PP, 8% DOW CORNING RM 4-781 53.5 31.8 67.7 EVA 2% VA 1% (Exxon) 1 1 1 99% EVA, 1% DOW CORNING RM 4-781 66 51 77.3 97% EVA, 3% DOW CORNING RM 4-781 54 44.9 72.7 95% EVA, 5% DOW CORNING RM 4-781 49 42.8 72.7-7 -

Silicone-Based Additives for Thermoplastic Resins Providing Improved Mechanical, Processing and Fire Properties Table IX.Polypropylene Modified With DOW CORNING RM 4-781 Resin Modifier and Mg(OH) 2 : Heat Release Rate, Carbon Monoxide Evolution, and Impact Strength (Qext = 4 kw/m 2 ) Peak Heat Release Rate, Peak CO Evolution Rate, Notched Izod Impact, Material, Weight % % vs. Control % vs. Control ft-lb/inch Polypropylene EXCORENE 112 1 1.821 95% PP/5% RM 4-781 Resin Modifier 55.4 39.6.675 75% PP/25% Mg(OH) 2 Versamag UF 32.5 23.4.389 75% PP/2% Mg(OH) 2/5% RM 4-781 26.9 2..737 65% PP/35% Mg(OH) 2 19. 12.8.352 65% PP/3% Mg(OH) 2/5% RM 4-781 19. 15.2.822 5% PP/5% Mg(OH) 2 15. 9.4.711 5% PP/45% Mg(OH) 2/5% RM 4-781 15. 9. 1.29 Table X. Cone Calorimeter, Processing and Impact Properties of Polypropylene Modified With Ammonium Polyphosphate Flame Retardants, With and Without DOW CORNING 4-781 Resin Modifier Peak Heat Peak CO Peak Smoke Torque, Notche Izod Release Rate, Evolution Rate, Evolution Rate, % vs. Impact, Material, Weight % % vs. Control % vs. Control % vs. Control Control ft-lb/in Polypropylene ESCORENE 112 (Control) 1 1 1 N/A.821 99% PP, 1% DOW CORNING RM 4-781 1. 89.6 85.48 N/A N/A 95% PP, 5% DOW CORNING RM 4-781 55.4 39.6 77.4 N/A.675 7% PP, 3% EXOLITE 422 (Control) 62.5 51.1 87.4 1 1.348 69% PP, 3% EXOLITE 422, 1% RM 4-781 N/A N/A N/A 46.4 2.63 85% PP,15% EXOLITE 422 68.3 65.5 92.8 55.8 1.366 82% PP, 15% EXOLITE 422, 3% RM 4-781 48.7 61. 17. N/A 2.72 7% PP, 3% PHOS-CHEK P4 (Control) 68.1 56.9 9.8 1 3.388 8% PP, 15% PHOS-CHEK P4, 5% RM 4-781 37.5 47.4 86.7 64.2 2.681 1 Some buildup on screws by phosphorus FR additive 2 No buildup on screws 3 Major buildup on screws by phosphorus FR additive N/A Not Available or Not Applicable IX. DOW CORNING RM 4-781 Resin Modifier Synergy With Ammonium Polyphosphate In a similar manner, polypropylene was modified with typical levels of ammonium polyphosphate (APP). In these examples, cone calorimetry, processing in the form of torque reduction and impact strength were examined. An example of peak heat release rate reduction is illustrated in Figure 8 where DOW CORNING RM 4-781 Resin Modifier was added and APP was removed. Additional experiments dealing with processing improvements (torque reduction) were done. These experiments indicate that silicone improved processing by a significant reduction in the torque of compound extrusion. With the addition of only 1% DOW CORNING RM 4-781 Resin Modifier to a standard APP formulation, torque was reduced significantly. This is identified in the Torque, % vs. Control column in Table X. Note also that silicone powders minimized and in some instances eliminated screw buildup of the APP formulation on the extruder screws. Mechanical properties, as indicated by notched Izod impact strength, were improved as well. APP reduces impact strength significantly when added at 15-3%. With the addition of as little as 1% silicone powder, these impact results approached unmodified polypropylene. Table X summarizes cone calorimeter, processing and impact results of polypropylene modified with APP and silicone powders. - 8 -

R. Buch, W. Page and D. Romenesko Heat Release Rate, kw/m 2 14 12 1 8 6 4 2 Qext = 3 kw/m 2 X. Conclusions 1% Polypropylene 7% PP, 3% PHOS-CHEK P4 6 12 18 24 3 36 Time, seconds 8% PP, 15% P-C P4, 5% DOW CORNING RM 4-781 Figure 8. Heat Release Rate of Polypropylene- Modified PHOS-CHEK P4 vs. Silicone Synergy From this study, the following conclusions can be drawn when DOW CORNING RM 4-751 and RM 4-781 Resin Modifiers are used in the specific resins and formulations described in this paper: Improved fire-retardant properties such as reduced rate of heat release and reduced rate of carbon monoxide and smoke evolution in polyolefins, polycarbonate, polystyrene, PPE, etc. Synergy with conventional fire-retardant additives such as halogen or ammonium polyphosphate fire retardant products and water evolving fire retardant products such as magnesium hydroxide Reaction extrusion demonstrated with silicone resin modifiers in PPE and PPS Impact strength improvement for engineering resins such as PPE and PPS, and plastics modified with Mg(OH) 2 or ammonium polyphosphate Improved processing (torque reduction) for highly filled systems Improved processing (torque reduction) for hightemperature engineering resins Silicone powders with methylmethacrylate functionality (4-781) or epoxy functionality (4-751) appear to have improved compatibility with selected plastics Developmental quantities of these silicone resin modifiers are now available. We encourage you to evaluate DOW CORNING RM 4-751 and RM 4-781 Resin Modifiers in your formulations to confirm the above features. Patents have been applied for. XI. Acknowledgement The authors would like to thank Dow Corning college co-ops Kevin Lupton, Shawn McGinley, Doug Dewey, and Ken Flood; without their dedicated work, our program would not have progressed so rapidly. In addition, Paul Pretzer provided excellent support on the cone calorimeter. XII. References 1. The Condensed Chemical Dictionary, Ninth Edition; Van Nostrand Reinhold, discussion of carbon monoxide. 2. Camino, G., Costa, L., Luda di Cortemiglia, M. P.; Overview of Fire Retardant Mechanisms, Journal of Polymer Degradation and Stability, Vol. 33, 1991, pp. 131-154. 3. Fire Test Standards, Third Edition, ASTM, Philadelphia, 199. 4. Tests for Flammability of Plastic Materials for Parts in Devices and Appliances (UL 94), Underwriters Laboratories, Northbrook, IL. 5. International Plastics Flammability Handbook, Principles, Regulations, Testing and Approval, Jurgen Troitzsch, Hanser Publishers distributed by Macmillan Publishing, New York. 6. Babrauskas, V. and S. J. Grayson, Heat Release in Fires, Elseivier Science Publishers Ltd., 1992. 7. Babrauskas, V., and R. D. Peacock, Heat Release Rate: The Single Most Important Variable in Fire Hazard, Fire Safety Journal, Vol. 18, No. 3, 1992, pp. 255-272. 8. Hill, Mark and John Redfern, The Heat Is On, Laboratory Practice, Vol. 4, No. 9. 9. Markezich, Dr. R. L., Advantages of Chlorinated Flame Retardants II, Occidental Chemical Corp., Environmentally Friendly Fire Retardant Systems, an Intertech Conference, Cleveland Marriott Society Center, Sept. 22-23, 1992. 1. National Electrical Code 1993. Article 45-23; NFPA-7-9 -

Silicone-Based Additives for Thermoplastic Resins Providing Improved Mechanical, Processing and Fire Properties WE HELP YOU INVENT THE FUTURE. TM www.dowcorning.com LIMITED WARRANTY INFORMATION - PLEASE READ CAREFULLY The information contained herein is offered in good faith and is believed to be accurate. However, because conditions and methods of use of our products are beyond our control, this information should not be used in substitution for customer s tests to ensure that Dow Corning s products are safe, effective, and fully satisfactory for the intended end use. Suggestions of use shall not be taken as inducements to infringe any patent. Dow Corning s sole warranty is that the product will meet the Dow Corning sales specifications in effect at the time of shipment. Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted. DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY. DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES. Dow Corning is a registered trademark of Dow Corning Corporation. WE HELP YOU INVENT THE FUTURE is a trademark of Dow Corning Corporation. 21 Dow Corning Corporation. All rights reserved. Printed in USA FPH28162-2 Form No. 25-59A-1