while this invention may be embodied in many forms , there are described in detail herein specific embodiments of the invention . this description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated . turning now to the figures , fig1 is a longitudinal cross - sectional view illustrating an embodiment of a balloon catheter assembly 10 . balloon catheter assembly is illustrative of a representative otw angioplasty balloon catheter . such balloon catheters are discussed , for example , in commonly assigned u . s . pat . nos . 6 , 113 , 579 , 6 , 517 , 515 , 6 , 514 , 228 , each of which is incorporated by reference herein in its entirety . in this embodiment , catheter 10 has an elongate shaft assembly 20 and an expandable balloon member 30 disposed at the distal end thereof . the shaft assembly 20 includes an inner tube 24 and an outer tube 22 . outer tube 22 is coaxially disposed about inner tube 24 to define an annular inflation lumen 26 . manifold assembly 28 is conventional . any portion of catheter assembly 10 can be formed from the compositions disclosed herein including inner tube 24 , outer tube 22 and expandable balloon 30 . in one embodiment , balloon 30 is formed from the compositions disclosed herein . fig2 is a perspective view of an expandable dilatation balloon 30 according to the invention . balloon 30 has body portion 32 , cone portions 34 and waist portions 36 . balloon 30 is formed from a polymer material that comprises functional groups that undergo hydrolysis in the presence of moisture under the right conditions . for example , balloon 30 is formed from a polymer material comprising ester , amide or acid anhydride functional groups . balloon 30 may be formed from polyamides such as nylon 12 available from degussa - hüls ag , north america ( national headquarters in düsseldorf , germany ) under the tradename of vestamid ® l2101f ( nylon 12 is available from a variety of polymer manufacturers ), nylon 6 and nylon 66 ; polyesters such as polyethylene terephthalate or polybutylene terephthalate ; polyether - polyesters such as those sold under the tradename of hytrel ® from dupont in wilmington , deleware and those sold under the tradename of arnitel ® available from dsm engineering plastics in birmingham , mich . ; poly ( ether - block - amide ) copolymers available from arkema under the tradename of pebax ® including pebax ® 6333 , pebax ® 7033 and pebax ® 7233 , polyester polyurethanes , polycarbonates , polyester carbonates , polyesteramides , polycaprolactones , polylactic acid , polyglycolide , polylactide - go - glycolide , naturally occurring polysaccharides , and mixtures thereof . this list is intended for illustrative purposes only and not as a limitation on the scope of the present invention . because these polymers undergo hydrolysis in the presence of moisture , they are susceptible during the melt extrusion process to a reduction in the size of the polymer chain as a result of the hydrolysis . it is therefore desirable to add a moisture scavenger to the polymer composition during the extrusion process that will rapidly react with water before the water molecules can attack the functional groups of the polymer chain and prevent molecular weight reduction in the balloon tubing . for example , either a monomeric carbodiimide or a polymeric carbodiimide can be added to the polymer composition during the melt extrusion process . these carbodiimides may be aliphatic , cycloaliphatic or aromatic in nature . suitably , the carbodiimides are aliphatic or cycloaliphatic carbodiimides , and most suitably the carbodiimide is aliphatic wherein r and r ′ are monovalent , r ′ may be the same as or different than r and may be independently aromatic , aliphatic , or cycloaliphatic , and may substituted with functional groups . r and r ′, for example , may be independently c 1 - c 20 alkyl or c 3 - c 10 cycloalkyl or c 1 - c 20 alkenyl group , and may be cyclic or branched , or may contain a c 8 - c 16 aromatic ring , and may be substituted with functional groups . examples of functional groups include , but are not limited to , cyanato and isocyanato , halo , amido , carboxamido , amino , imido , imino , silyl , etc . these lists are intended for illustrative purposes only and not as a limitation on the scope of the present invention . specifically , r and r ′ may be independently c 6 h 12 , ( ch 2 ) n w wherein n is 1 - 3 , and w may be ch 3 , nh 2 , nco , for example . specific examples of monomeric carbodiimides useful herein include , but are not limited to , n , n ′- dicyclohexylcarbodiimide ( dcc ), n , n ′- diisopropylcarbodiimide or 1 - ethyl - 3 -( 3 - dimethylaminopropyl ) carbodiimide ( edc , edac or edci ), n , n ′- diphenylcarbodiimide , n , n ′- di - 2 , 6 - diisopropylphenylcarbodiimide , etc . see , for example , u . s . patent publication no . 2009 / 0176938 , the entire content of which is incorporated by reference herein in its entirety . this list is intended for illustrative purposes only , and not as a limitation on the scope of the present invention . commercially available monomeric carbodiimides include those sold by rhein chemie in mannheim , germany under the tradename of stabaxol ®. one specific example of a monomeric carbodiimide is stabaxol ® i ( bis - 2 , 6 - diisopropylphenylcarbodiimide ). wherein r is monovalent r ′ is divalent , n is 2 to 50 , suitably 2 to 45 , more suitably 2 to 20 and preferably 5 to 20 . r may be , for example , c 1 - c 20 alkyl or c 3 - c 10 cycloalkyl or c 1 - c 20 alkenyl group , and may be cyclic or branched , or may contain a c 8 - c 16 aromatic ring , and may be substituted with functional groups . r ′ may be a divalent group corresponding to any for the foregoing , e . g ., c 1 - c 20 alkylene , c 3 - c 10 cycloalkylene , etc . examples of functional groups include , but are not limited to , cyanato and isocyanato , halo , amido , carboxamido , amino , imido , imino , silyl , etc . these lists are intended for illustrative purposes only , and not as a limitation on the scope of the present invention . suitable polymeric carbodiimides useful herein include , for example , repeat units of n , n ′- dicyclohexylcarbodiimide , n , n ′- diisopropylcarbodiimide , 1 - ethyl - 3 -( 3 - dimethyl aminopropyl ) carbodiimide hydrochloride , n , n ′- diphenylcarbodiimide , n , n ′- di - 2 , 6 - diisopropylphenylcarbodiimide , 4 , 4 ′- dicyclohexylmethanecarbodiimide , tetramethylxylylenecarbodiimide ( aromatic carbodiimide ), n , n - dimethylphenylcarbodiimide , n , n ′- di - 2 , 6 - diisopropylphenylcarbodiimide , 2 , 2 ′, 6 , 6 ′- tetraisopropyl diphenyl carbodiimide ( aromatic carbodiimide ), aromatic homopolymer of 1 , 3 , 5 - triisopropyl - 2 , 4 - diisocyanatobenzene aromatic heteropolymer of 1 , 3 , 5 - triisopropyl - 2 , 4 - diisocyanatobenzene and 2 , 6 - diisopropyl phenyl isocyanate , or combinations thereof . see u . s . pat . nos . 5 , 130 , 360 , 5 , 859 , 166 , 7368493 , 7456137 , and u . s . patent publication nos . 2007 / 0278452 and 2009 / 0176938 , each of which is incorporated by reference herein in its entirety . specific examples of r ′ include , but are not limited to , divalent radicals derived from 2 , 6 - diisopropylbenzene , naphthalene , 3 , 5 - diethyltoluene , 4 , 4 ′- methylene - bis ( 2 , 6 - diethylenephenyl ), 4 , 4 ′- methylene - bis ( 2 - ethyle - 6 - methylphenyl ), 4 , 4 ′- methylene - bis ( 2 , 6 - diisopropylephenyl ), 4 , 4 ′- methylene - bis ( 2 - ethyl - 5 - methylcyclohexyl ), 2 , 4 , 6 - triisopropylephenyl , n - hexane , cyclohexane , dicyclohexylmethane , and methylcyclohexane , and the like . the stabaxol p series of carbodiimides available from rhein chemie in mannheim , germany are examples of commercially available aromatic polycarbodiimides . isocyanate termination of the polymer chain is one preferred embodiment from the standpoint of stability against hydrolysis under conditions of storage . see , for example , u . s . patent publication no . 2009 / 0318628 , the entire content of which is incorporated herein by reference wherein examples or diisocyanates for producing aliphatic , cycloaliphatic and aromatic carbodiimides include 1 , 5 - naphthalene diisocyanate , 4 , 4 ′- diphenylmethane diisocyanate , 4 , 4 ′- diphenyldimethylmethane diisocyanate , 1 , 3 - phenylenediisocyanate , 1 , 4 - phenylenediisocyanate , 2 , 4 - tolylenediisocyanate , 2 , 6 - tolylenediisocyanate , hexamethylene diisocyanate , cyclohexane - 1 , 4 - diisocyanate , xylylene diisocyanate , isophorone diisocyanate , dicyclohexylmethane - 4 , 4 ′- diisocyanate , methylcyclohexane diisocyanate , tetramethylxylylene diisocyanate , 3 , 3 ′, 5 , 5 ′- tetraisopropylbiphenyl - 4 , 4 ′- diisocyanate , and 1 , 3 , 5 - triisopropylbenzene - 2 , 4 - diisocyanate . mixtures of isocyanates may be employed as well . see u . s . patent publication no . 2008 / 0064826 the entire content of which is incorporated by reference herein . the carbodiimides useful herein react in the presence of water to produce urea the reaction of which is represented by the following general formula : the carbodiimide is useful in amounts of about 10 % by weight of the polymer composition or less , suitably about 0 . 1 % to about 10 %, more suitably about 0 . 5 % to about 5 % and most suitably about 1 % to about 2 % by weight of the polymer composition . both the monomeric and the polymeric forms help to prevent a decrease in the molecular chain size and consequently a decrease in molecular weight , and form a nanocomposite at the molecular level of the tubing and thus reinforce the polymer material . whether or not it is catheter tubing or a balloon which is being formed , the carbodiimide is added to the polymer in melt form such as during the extrusion process . the balloon may be formed using any suitable method known in the art . in some embodiments , the method suitably includes forming a tubular parison , stretching the tubular parison , placing the balloon parison in a balloon mold , and forming a balloon by radially expanding the tubular parison into the balloon mold . the balloon is then heat set . balloon forming with stretching and radial expansion is disclosed in u . s . pat . nos . 5 , 913 , 861 , 5 , 643 , 279 and 5 , 948 , 345 , and in commonly assigned u . s . pat . nos . 6 , 946 , 092 and 7 , 1010 , 597 , each of which is incorporated by reference herein in its entirety . the description provided herein is not to be limited in scope by the specific embodiments described which are intended as single illustrations of individual aspects of certain embodiments . the methods , compositions and devices described herein can comprise any feature described herein either alone or in combination with any other feature ( s ) described herein . indeed , various modifications , in addition to those shown and described herein , will become apparent to those skilled in the art from the foregoing description and accompanying drawings using no more than routine experimentation . such modifications and equivalents are intended to fall within the scope of the appended claims . all publications , patents and patent applications mentioned in this specification are herein incorporated by reference in their entirety into the specification to the same extent as if each individual publication , patent or patent application was specifically and individually indicated to be incorporated herein by reference . citation or discussion of a reference herein shall not be construed as an admission that such is prior art .
a medical device , the medical device formed at least in part from a melt blend of at least one polymer comprising hydrolysable groups and a carbodiimide .