Patent Publication Number: US-2003232941-A1

Title: Polysiloxane(amide-ureide) anti-ice coating and associated method for producing same

Description:
FIELD OF THE INVENTION  
       [0001] This invention relates to a polymeric coating which inhibits the adhesion of ice to the surface of an object. The invention further relates to the composition and method of making a polysiloxane(amide-ureide) which provides a durable, long-lasting, anti-ice coating when applied to a substrate.  
       BACKGROUND OF THE INVENTION  
       [0002] The everyday buildup of ice upon the surfaces of mechanical, physical, and natural objects is a familiar annoyance, and quite often a safety hazard. The slick layers of ice that form on highways, driveways, and walkways make transportation difficult. The masses of ice that accumulate within or upon industrial, agricultural, or other mechanical equipment make operation of the equipment difficult or impossible. And, the weight of ice that weighs upon power lines, buildings, and signs often causes damage to those structures.  
       [0003] Buildup of ice upon the wings and components of an aircraft is of particular concern. The lift generated by the wings, and thus the ability of the aircraft to become and remain airborne, is dependent on the shape of the wings. Even a small accumulation of ice upon the surface of the wings can have a huge aerodynamic effect and can dramatically reduce the ability of the wings to lift the aircraft into the air. Further, ice buildup along control surfaces of the aircraft can impede the movement of those surfaces and prevent proper control of the aircraft.  
       [0004] There are a large variety of techniques used to control the buildup of ice upon the wings and other surfaces of aircraft. For instance, the aircraft may be de-iced before takeoff by application of a chemical spray which melts the ice from the wings. Such deicing sprays are often toxic and harmful to the environment. The ritual of deicing is well known to airline passengers traveling through cold environments.  
       [0005] Another method of de-icing aircraft includes providing flexible pneumatic coverings along the leading edges of the wings, and supplying bursts of air or fluid to the wing through the flexible coverings to break away any overlying ice. Similarly, bleeding air from the aircraft engine and routing the heated air to the surface of the wing heats the wing and melts the ice. Finally, ice may be removed from the wing by providing high-current pulses of electricity to a solenoid disposed within the wing which causes the wing to vibrate, fracturing any accumulated ice.  
       [0006] Although the previously mentioned methods of ice removal are generally effective, they require the continuous supply of air, chemicals, or electrical power in order to rid the wing of its burden. It would be preferred, of course, to prevent the accumulation of ice in the first place, but past attempts to develop practical passive methods of ice prevention have failed.  
       [0007] One would expect that known non-stick coatings would be able to prevent ice from adhering to the surfaces which they coat. In fact, aluminum surfaces coated with a Teflon™ material exhibit a zero break force between the ice and the Teflon™ coating. However, upon repeated freezing, the favorable properties exhibited by Teflon™ and similar coatings degrade, resulting in a coating with little or no anti-icing capacity.  
       [0008] What is needed is a durable surface coating, with long lasting anti-icing properties. What is further needed is a surface coating that may be easily applied to the surface of an aircraft under a variety of environmental conditions.  
       SUMMARY OF THE INVENTION  
       [0009] The invention is a polysiloxane(amide-ureide) coating capable of inhibiting the accumulation of ice upon the surface of a substrate and a process of producing the polysiloxane(amide-ureide). The polysiloxane(amide-ureide) forms a durable, long lasting, anti-ice coating when employed upon a substrate. When coated upon a substrate, the polysiloxane(amide-ureide) coating disrupts between the ice and the coated substrate, as well as the hydrogen bonding in the ice crystal, thereby diminishing the ability of the ice to adhere to the surface. Moreover, when ice does form, the coating disrupts the hydrogen bonding between the ice and the coated surface, thereby diminishing the ability of the ice to adhere to the surface.  
       [0010] The polysiloxane(amide-ureide) has the general formula:  
                 
 
       [0011] wherein  
       [0012] R 1  and R 2  are independently selected from the group consisting of C 1  to C 6  alkyls and aryls;  
       [0013] R 3  and R 4  are independently selected from the group consisting of hydrogen;  
       [0014] C 1  to C 6  alkyls; aryls; C 3  to C 6  cycloaliphatics; and C 3  to C 6  heterocycles;  
       [0015] A 1  and A 2  are independently selected from the group consisting of hydrogen;  
       [0016] C 1  to C 6  alkyls; aryls; C 7  to C 12  alkylaryls; C 3  to C 6  cycloaliphatics; and C 3  to C 6  heterocycles; and are preferably methyl;  
       [0017] wherein the alkyls may be linear or branched, saturated or unsaturated, halogenated or non-halogenated; aryls may be halogenated or non-halogenated; cycloaliphatics may be saturated or unsaturated, halogenated or non-halogenated; heterocycles may be saturated or unsaturated, halogenated or non-halogenated; and alkylaryls may be linear or branched, saturated or unsaturated, halogenated or non-halogenated;  
       [0018] x is a number from 1 to 10000, preferably between about 200 and 2000; and, Y is selected from a dicarboxyl component and a non-linear diisocyanate component.  
       [0019] A preferred polysiloxane(amide-ureide) is represented by the formula:  
                 
 
       [0020] wherein each of R 1 , R 2 , A 1 , A 2 , R 3 , R4, and x are as defined above, and Z is a dicarboxyl and CYAN is a non-linear diisocyanate.  
       [0021] The polysiloxane(amide-ureide) is formed by reacting a diamine-terminated polysiloxane, a halide substituted dicarboxylic acid, and a diisocyanate. The beginning diamine-terminated polysiloxane has the general formula:  
                 
 
       [0022] wherein R 1 ,R 2 , R 3 , R 4 , A 1 , A 2 , and x are as defined above.  
       [0023] The halide substituted dicarboxylic acid is a low molecular weight dicarboxlic acid wherein the hydroxyl from each carboxylic acid component has been replaced with a halide constituent, typically chloride. At least a portion of the substituted dicarboxylic acids are preferably selected from fumaryl, succinyl, phthalyl, terephthalyl and maleyl halides, and more preferably fumaryl chlorides and maleyl chlorides.  
       [0024] To prepare the preferred polymer, the amine-terminated polysiloxane is first reacted with a dicarboxylic halide to form a polyamide intermediate. After formation of the polyamide, the polyamide is reacted with a non-linear diisocyanate to form the polysiloxane(amide-ureide) of formula (Ib). Use of fumaryl halides, phthaloyl halides, and maleyl halides as the dicarboxylic acid halides and use of the non-linear diisocyanate result in a polysiloxane(amide-ureide) with a decidedly non-linear orientation. Thus, the resulting polymer (Ib) contains functional amide groups, functional urea groups, and is amorphous rather than crystalline in nature, due to the non-linear orientation of the polymer molecules. Each of the amide functionality, the urea functionality, and the non-linearity of the polymer improve the polymer&#39;s strength or anti-icing properties. Furthermore, the amide/urea moieties create crystallinity within the polymer via intermolecular hydrogen bonding which, in conjunction with the amorphous nature of the polysiloxane and the non-linearity of the diacid or diisocyanate, create a toughened polymer with enhanced physical properties.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0025] The present invention now will be described more fully with reference to various embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.  
       [0026] The invention is an improved surface coating which inhibits the ability of ice to form upon a coated surface. The surface coating is particularly effective when applied to aluminum, steel, titanium, glass, ceramic, and carbon composite surfaces and may be particularly useful for inhibiting the formation of ice upon the flight surfaces of aircraft or space vehicles. The coating also forms an effective ice inhibitor when used on a wide variety of substrate materials other than the preferred aluminum, titanium or carbon composite.  
       [0027] The polysiloxane(amide-ureide) has the general formula:  
                 
 
       [0028] wherein  
       [0029] R 1  and R 2  are independently selected from the group consisting of C 1  to C 6  alkyls and aryls;  
       [0030] R 3  and R 4  are independently selected from the group consisting of hydrogen; C 1  to C 6  alkyls; aryls; C 3  to C 6  cycloaliphatics; and C 3  to C 6  heterocycles;  
       [0031] A 1  and A 2  are independently selected from the group consisting of hydrogen; C 1  to C 6  alkyls; aryls; C 7  to C 12  alkylaryls; C 3  to C 6  cycloaliphatics; and C 3  to C 6  heterocycles; and are preferably methyl;  
       [0032] wherein the alkyls may be linear or branched, saturated or unsaturated, halogenated or non-halogenated; aryls may be halogenated or non-halogenated; cycloaliphatics may be saturated or unsaturated, halogenated or non-halogenated; heterocycles may be saturated or unsaturated, halogenated or non-halogenated; and alkylaryls may be linear or branched, saturated or unsaturated, halogenated or non-halogenated;  
       [0033] x is a number from 1 to 10000, preferably between about 200 and 2000; and, Y is selected from a dicarboxyl component and a non-linear diisocyanate component.  
       [0034] The polysiloxane(amide-ureide) is formed by reacting a diamine-terminated polysiloxane, a halide substituted dicarboxylic acid, and a diisocyanate.  
       [0035] A preferred coating is comprised of a polysiloxane(amide-ureide) polymer having the general formula:  
                 
 
       [0036] wherein each of R 1 , R 2 , A 1 , A 2 , R 3 , R4, and x are as defined above, and Z is a dicarboxyl and CYAN is a non-linear diisocyanate.  
       [0037] The preferred polysiloxane(amide-ureide) is created by first reacting a high molecular weight diamine-terminated polysiloxane as shown below in structure (II) with a halide substituted dicarboxylic acid, examples of which are shown as structures (IV), to form a polyamide intermediate, shown below as structure (III). The polyamide intermediate (III) is then reacted with a non-linear diisocyanate shown as structure (V) to form the polysiloxane(amide-ureide) (Ib). Each of the reactants and each of the process steps are described in greater detail below.  
       [0038] The beginning diamine-terminated polysiloxane has the general formula:  
                 
 
       [0039] wherein R 1 ,R 2 , R 3 , R 4 , A 1 , A 2 , and x are as defined above. If any of the R 1 ,R 2 , R 3 , R 4 , A 1 , A 2  groups are aryl, then those aryl groups are preferably phenyl. A 1  and A 2  need not be regularly repeating patterns of hydrogen, alkyl, alkylaryl, or aryl groups. For instance, the polysiloxane (II) may have a wide variety of randomly dispersed A 1  and A 2  groups throughout the length of the polysiloxane.  
       [0040] Although the number of repeat units, x, in the polysiloxane (II) may be as low as one, the average is generally between about 200 and 10,000, and is preferably between about 200 and 2000. The polysiloxane may be linear or branched. When branched, the A 1  or A 2  groups are a site of branching. Branching is one method of obtaining a crosslinked end-product.  
       [0041] Polysiloxanes such as those of structure (II) are commercially available from United Chemical Technologies, Inc. in Bristol, Pa., and also from Dow Chemical Co., Midland, Mich. The preferred polysiloxanes are linear, though branched polysiloxanes may also be used.  
       [0042] A halide substituted dicarboxylic acid (“diacid halide”) is reacted with the polysiloxane (II) to form the intermediate polyamide (III):  
                 
 
       [0043] The halide substituted dicarboxylic acid used in the reaction is a low molecular weight dicarboxylic acid wherein the hydroxyl group from each carboxylic acid component has been replaced with a halide constituent. The dicarboxylic acid is either an aliphatic or aromatic compound with halogen substituted carboxylic acid endgroups. Preferred aliphatic dicarboxylic acid components have less than ten carbons, with examples of the diacid halides including but not limited to malonyl halides, succinyl halides, glutaryl halides, adipyl halides, sebacyl halides, maleyl halides, and fumaryl halides. Examples of aromatic substituted dicarboxylic acids include terephthalic acid or phthalic acid. Polyfunctional substituted dicarboxylic acids may be used with the invention to promote crosslinking.  
       [0044] Examples of commercially available aliphatic substituted dicarboxylic acid components are fumaryl chloride, succinyl chloride, and maleyl chloride, each available from Aldrich™ of Milwaukee, Wis.  
       [0045] Preferably, at least a portion of the substituted dicarboxylic acids, Z, used to form the polysiloxane(amide-ureide) (IIb) are selected from fumaryl halides and maleyl halides. The fumaryl and maleyl halides are cis and trans variations of one another having the following formulas:  
                 
 
       [0046] The incorporation of the fumaryl halide and the maleyl halide act to limit the degree of freedom of the polyamide (III) produced by the reaction of the diamine polysiloxane (II) and the dicarboxylic acid (IV). When reacted, the amine groups of the diamine polysiloxanes (II) displace the halides and bond with the carboxyl carbon of the fumaryl halides or maleyl halides. Once bonded, the unsaturated carbon linkage prevents the resulting polyamide (III) from rearranging into a stable spatial orientation, and is particularly useful in preventing the polyamide (III) from taking on a linear or near-linear orientation.  
       [0047] The degree of linearity of the polyamide (III), and therefore of the resulting polysiloxane(amide-ureide) (Ib) is determined by the relative amounts of fumaryl halide and maleyl halide in relation to saturated halide substituted dicarboxylic acids (IV) used in the formation of the polyamide. The addition of saturated acid halides, such as succinyl chloride, allow the polyamide (III) to rotate and orient about the succinyl saturated carbon-carbon bond, thus allowing the polyamide (III) and resulting polysiloxane(amide-ureide) (Ib) to orient in a near-linear orientation. Saturated acid halides such as succinyl, malonyl or other saturated acid halides may be used in conjunction with the unsaturated acid halides to create a polyamide (III) having a combination of crystalline and amorphous regions in order to control the toughness of the resultant polysiloxane(amide-ureide) (Ib).  
       [0048] The polysiloxane(amide-ureide) (Ib) shows improved anti-icing properties when formed into an amorphous structure with some small amount of crystallinity for enhanced toughness. Maleyl or fumaryl halide cause the structure of the polymer to be non-linear about the carbon-carbon double bonds in the maleyl and fumaryl entities. The combined maleyl and fumaryl, or other unsaturated diacid halide, content is therefore preferably greater than 50 mol % of the dicarboxylic acid halide used in preparation of the polysiloxane(amide-ureide) (Ib). It is more preferable that the unsaturated diacid halides comprise between about 75% and 99% of the diacid halides. The disorientation caused by the fumaryl halide and maleyl halide give the resulting polysiloxane(amide-ureide) an amorphous structure, but the introduction of a saturated diacid halide helps to increase the toughness of the polymer compared with linear polymers having amide or ureide moieties. The non-linear orientation of the polymer makes the polysiloxane(amide-ureide) less brittle than polyureides produced with linear diisocyanates such as methylene diphenyl diisocyanate. Being less brittle, the polysiloxane(amide-ureide) is more durable than industrially available polyureides, and is able to resist the environment associated with ice formation without being damaged.  
       [0049] The formation of the polyamide intermediate (III) takes place by reacting an excess of the diamine polysiloxane (II) with a given amount of dicarboxylic acid halide (IV), preferably in a molar ratio of about 2:1. The reaction is generally performed in a solvent such as methylene chloride, tetrahydrofuran, toluene or methylethyl ketone. The amine-terminated polysiloxane (II) is added to the diacid halide (IV) in the presence of an acid acceptor such as triethylamine, at elevated temperature, for instance 50° C. As such, the average resulting polyamide intermediate (III) has amine endgroups:  
                 
 
       [0050] After formation of the polyamide intermediate (III), the polyamide intermediate is reacted with a non-linear diisocyanate (V) to form the polysiloxane(amide-ureide) (Ib). The non-linear diisocyanates generally have the structure of:  
                 
 
       [0051] where X is an aliphatic or aromatic moiety and the two isocyanate groups are bound to the X moiety so as to be positioned in a non-linear relationship with respect to one another. The amine endgroups of the polyamide (III) react with the isocyanate endgroups of the non-linear diisocyanates (V) to form urea linkages.  
       [0052] The diisocyanates (V) are reacted in a solvent bath with the polyamide intermediate (III). The reaction preferably occurs directly after reacting the polysiloxane (II) with the diacid halide (IV) within the same solvent bath, but at room temperature, rather than 50° C.  
       [0053] As with the non-linear dicarboxylic acids, the purpose of utilizing a non-linear diisocyanate is to give the resulting polysiloxane(amide-ureide) an overall non-linear orientation, which results in a polymer that is more amorphous and less crystalline. Non-linear aliphatic or aromatic diisocyanates may be used, with ortho or meta oriented aromatic diisocyanates being preferred.  
       [0054] The functionality of the diisocyanates is gained from the dual isocyanate groups being located in a non-linear relationship around an aliphatic or aromatic carbon structure. Polyisocyanates, i.e., those compounds having three or more isocyanate groups, may be used for enhanced crosslinking of the resulting polysiloxane(amide-ureide) (Ib). Otherwise, the diisocyanates may be substituted or unsubstituted with groups such as alkyl, alkoxy, halogen, benzyl, allyl, unsubstituted or substituted aryl, alkenyl, alkinyl, amide, or combinations thereof.  
       [0055] Examples of acceptable diisocyanates include 1,5-naphthalene diisocyanate, 4,4-diphenyl-methane diisocyanate, tetra-alkyl-diphenyl methane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, butane-1,4-diisocyanate, hexamethylene 1,6-diisocyanate, 2,2,4-trimethyl-hexamethylene 1,6-diisocyanate, 2,4,4-trimethyl-hexamethylene 1,6-diisocyanate, tridinediisocyanate, cyclohexane-1,4-diisocyanate, xylilene diisocyanate, dicyclohexyl-methane-4,4′-diisocyanate, methyl-cyclohexane diisocyanate, 1,4-tetramethylene diisocyanate, hexamethylene diisocyanate, 1,3-trimethylene diisocyanate, metaxylene diisocyanate, decamethylene 1,10-diisocyanate, cyclohexylene 1,2- diisocyanate, cyclohexylene 1,4-diisocyanate, 1-methyl cyclohexane 2,4-diisocyanate, 2,4-toluene diisocyanate, hexamethylene-1,6-diisocyanate, heptamethylene-1,7-diisocyanate, 1,3-cyclopentene diisocyanate, and 1,3-cyclohexane diisocyanate, most of which are commercially available from Aldrich™ of Milwaukee, Wis.  
       [0056] The polysiloxane(amide-ureide) resulting from the combination of the polyamide (III) and diisocyanate (V) has the general formula:  
                 
 
       [0057] with R 1 , R 2 , R 3 , R 4 , A 1 , A 2 , x as defined above, and wherein Z represents a dicarboxylic acid group; and CYAN represents a diisocyanate group.  
       [0058] The preferred embodiment (Ib) may be generalized into the structure:  
                 
 
       [0059] wherein R 1 , R 2 , R 3 , R 4 , A 1 , A 2 , x and Y are as defined above, by using the above described reactants and the above described reaction conditions, but by changing the order of reaction of components from the preferred embodiment.  
       [0060] For instance, alternatively, a polysiloxane (II) and a diisocyanate (V) may be reacted with a diacid halide in a common solvent solution such that the molar ratios of the reactants are 2:1 (polysiloxane:diisocyanate) and 2:1 (combination of polysiloxane and diisocyanate : diacid halide). The reaction results in amine-terminated products. The amine-terminated products are reacted with a diacid halide to form a random copolymer(amide-ureide).  
       [0061] In another embodiment, it is possible to create block copolymers of the polysiloxane(amide-ureide). To create the block copolymer, a first amine-terminated polysiloxane (II) is reacted with a diacid halide (IV), preferably in a molar ratio of 2:1 (polysiloxane:diacid halide) to form a first product. Separately, a second amine-terminated polysiloxane (II) is reacted with a diisocyanate (V), preferably in a molar ratio of 2:1 (polysiloxane:diisocyanate) to form a second product. The two products (each amine-terminated) are then reacted with diacid halide to result in a block copolymer(amide-ureide).  
       [0062] The invented polysiloxane(amide-ureide)s have several functional aspects which combine to make the polysiloxane(amide-ureide)s superior, durable, and long lasting anti-icing agents which can be used on a wide variety of surfaces.  
       [0063] It has been found that the urea groups of the polysiloxane(amide-ureide)s act to disrupt the hydrogen bonding between molecules of water, which inhibits the formation of ice and also greatly diminishes the adhesion of ice to the polysiloxane(amide-ureide)s when the polysiloxane(amide-ureide)s are used as a coating layer upon a substrate. So, the polysiloxane(amide-ureide)s anti-icing agent acts first to inhibit the formation of ice, and secondly to inhibit the ability of ice to adhere to a coated surface. The polysiloxane portion of the polymer chain is hydrophobic, hence water does not readily sheet out, but tends to bead up. The urea moiety, in weakening the hydrogen bonding of the water molecule causes the resultant ice to have a weak structure which prevents water from forming a strong ice crystal layer upon a coating of the polysiloxane(amide-ureide)s, thus allowing it to be easily broken away from the coating.  
       [0064] The polysiloxane(amide-ureide) may be applied as a continuous coating upon a wide variety of surfaces, particularly metal surfaces such as aluminum or titanium. Because the coating is continuous, water cannot penetrate the coating. It is believed that the penetration of water into sintered coatings, such as Teflon™, result in the gradual degradation in icephobic properties of such sintered coatings. There is no such related degradation in the invented polysiloxane(amide-ureide).  
       [0065] Thus, the polysiloxane(amide-ureide) has anti-icing properties not previously found in polyamides. It has degradation resistance not previously found in polyureides. And, it has physical toughness and durability not previously found in polyamides or polyureides.  
       [0066] The polysiloxane(amide-ureide) may be applied to a substrate in a number of ways. For instance, it may be applied to substrate surfaces by simply spraying the polymer composition upon a substrate. As one component spray, a solution of the polysiloxane(amide-ureide) in methylene chloride/toluene mixture (1:1 ratio) is sprayed onto a substrate to be coated. After the solvent is evaporated off, a uniform film of polymer is left behind.  
       [0067] As a two component system, the amine-terminated polyamide intermediate (III) is dissolved in the methylene chloride/toluene mixture and in another mixture of methylene chloride/toluene is dissolved the stoichiometric amount of diisocyanate (V). The two mixtures are combined in a common spray nozzle and mixed while being sprayed onto a dry substrate under inert atmosphere conditions to form a polysiloxane(amide-ureide) coating on the substrate.  
       [0068] Alternatively, the polysiloxane(amide-ureide) may be dissolved in a solvent, such as methylene chloride at a concentration of about 50 percent solids and sprayed onto the substrate. The solvent, being low boiling, evaporates rapidly and a film of polysiloxane(amide-ureide) is left behind.  
       [0069] Alternatively, the polyamide intermediate (m) is mixed with a methylene chloride solution of a polyisocyanate (V) at a mixing nozzle of a spray gun and ejected onto the substrate. This process results in a crosslinked polymer, which cures within a few minutes to a firm crosslinked film.  
       [0070] In a one component spray, the polysiloxane(amide-ureide) is capable of being handled or walked upon as soon as the solvent has all evaporated. Use of a heat source, such as hot air or infrared lamps, will accelerate the solvent removal. In the two component system, the polysiloxane(amide-ureide) forms almost as soon as the two parts are mixed and sprayed onto the substrate. Again use of hot air or heat lamps will facilitate solvent removal to leave behind a useable film.  
       [0071] The polysiloxane(amide-ureide) is hydrophobic and tends to displace any moisture upon surfaces when applied, therefore the polysiloxane(amide-ureide) may be applied successfully to wet or damp surfaces. The polymer can be applied anywhere between about minus 40° F. and about 250° F., and the polymer coating is stable to about 350° F. The coating may be applied in a single layer having any desired thickness, eliminating the need for multi-coat applications.  
       [0072] The polysiloxane(amide-ureide) is particularly useful for application to aluminum or titanium surfaces and provides a coating which may be used to prevent ice formation upon the flight surfaces of an aircraft. The usefulness of the polysiloxane(amide-ureide) is not limited to metal surfaces, however. The polysiloxane(amide-ureide) finds use as a coating on any of a wide variety of substrates such as steel and carbon composites, and even wood or asphalt, a number of which may be applications unrelated to aircraft. 
     
    
    
     EXAMPLES  
     Example 1  
     [0073] The reaction between a high molecular weight diamine-terminated polysiloxane, dissolved in methylene chloride, with a tertiary amine, e.g., triethylamine, as an acid acceptor, and fumaryl chloride in a molar ratio of 2:1 resulted in the formation of a diamine-terminated poly (siloxane diamide).  
     [0074] The tertiary amine hydrochloride was filtered off and the resultant diamide was reacted with toluene-2,4-diisocyanate in a 1:1 molar ratio of diamide to diisocyanate to form a polysiloxane(amide-ureide) with repeated trans structure about the double bond of the fumaryl moiety. The ratio of amine-terminated poly(siloxane amide) to isocyanate was dictated by the functionality of the isocyanate, i.e., a tri-isocyanate would require two moles of the poly(siloxane amide) to one mole of tri-isocyanate.  
     Example 2  
     [0075] Into a two liter, three-necked round bottom flask was added one mole of fumaryl chloride dissolved in 500 mils of methylene chloride. A dry, inert atmosphere was maintained by means of a drying tube and nitrogen purge. To this solution was added, slowly and with stirring, two moles of α, ω-diaminopolysiloxane, dissolved in 500 mils of methylene chloride and containing two moles of triethylamine as an acid acceptor. After the addition was completed, the mixture was heated to 50° C. for one hour and the amine hydrochloride was filtered off, leaving the amine-terminated fumaryl polyamide in solution. The one mole of polyamide was added to one mole of 2, 4-toluene diisocyanate dissolved in 100 mils of methylene chloride with a precaution of maintaining a dry, inert atmosphere. After allowing the reaction to proceed for 24 hours at room temperature, the methylene chloride solution of the polysiloxane(amide-ureide) was ready to be used as a coating material on the substrate needing ice protection.  
     Example 3  
     [0076] One mole of succinyl chloride, one mole of fumaryl chloride, and four moles of amine-terminated polydimethylsiloxane were reacted to yield polyamides with a trans amide component around the double bond of the fumaryl moiety and a linear amide component around the single bond of the succinyl moiety. Thus, the linearity of the polyamide may be adjusted prior to reaction with the diisocyanate by controlling the relative amounts of saturated and unsaturated acid halide, i.e. the relative amounts of fumaryl chloride versus succinyl chloride.  
     Example 4  
     [0077] Two moles of fumaryl chloride and one mole of propylamine-terminated polydimethylsiloxane were reacted. The product was reacted with two moles of butylamine-terminated polydimethylsiloxane. That product was then reacted with one mole of toluene-2,4-diisocyanate to result in a block copolymer polysiloxane(amide-ureide).  
     Example 5  
     [0078] Two moles of amine-terminated polydimethylsiloxane was reacted with one mole of fumaryl chloride to form a first product. One mole of toluene-2,4-diisocyanate was reacted with two moles of amine-terminated polydimethylsiloxane to form a second product. These products (each amine-terminated) were then reacted with two moles of fumaryl chloride to result in a block copolymer(amide-ureide).  
     [0079] Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.