AU2014202395A1 - A flexible tubing material and method of forming the material - Google Patents

Abstract

A flexible tubing material includes a radiation crosslinked blend of a first elastomeric polymer including a styrenic thermoplastic elastomer, an ethylene vinyl acetate elastomer, a polylefin elastomer with a second elastomeric polymer including a polyolefin elastomer, a diene elastomer, or combination thereof, with the proviso that the first elastomeric polymer and the second elastomeric polymer are different. In an enbodiment, a method of making a material includes providing the first elastomeric polymer, providing the second elastomeric polymer, blending the first elastomeric polymer and the second elastomeric polymer, extruding or injection molding the blend, and crosslinking the blend with radiation.

Description

AUSTRALIA PA TENTS ACT 1990 REGULATION 3.2 Name of Applicant: SAI NT-GOBAIN PER FORMANCE PLASTICS CORPORA TION Actual Inventor/s: Sridhar K. Siddhamalli, Zhizhong Liu, Mark W. Simon, Charles S. Golut, Heidi Sardinha, Wayne F., Garver, Mark F. Colton, Robert L. Vells, Gerald L Stadt, Michael J. Tzivanis, William Risen and Nathan KIettlinger Address fotr Service: E, F. WELLINGTON & CO., Patent and Trade Mark Attorneys, 312 St. Kilda Road, Melboumne, Southbank, Victoria, 3006, Invention Title: "A FLEXIBLE TUBING MATERIAL AND METHOD OF FORMING THE MATERIAL" Details of Associated Provisional Applications Nos: The bfllowing statement is a full description of this invention including the best method of perfonning it known to us, 5 RELATED APPLICATIONS This application is a 'divisional' application derived from Australian Patent Application No. 2010343054 (PCT/US2010/062430: WO201 1/090756), claiming priority of US Application No. 61/290731, the entire text of which are hereby incorporated herein by reference. FIELD OF THE DISCLOSURE This disclosure, in general relates to a flexible tubing material and. methods ofmaking the aforementioned material BACKGROUND ART Currently, flexible medical tubing is used to transport any variety of liquids daring 5 medical procedures. A flexible polyvinyl chloride (PV is a typical material used for medical tubing due to their nhernt flexibility and translucency. Unfortunately, polyvinyl chloride tubing has significant amounts of low-molecular weight chemicals that can be leached into the human body during medical treatments Furthe, disposal of PVC-based wasted by incineration causes environmental issues due to the release of toxic gases Alternative materials to flexible PVC have been adopted to make flexible medical tubing. Polymers that may be desired typically include those that are flexible, transparent, and appropriate for certain applications. Unfortunately, these polymers may not have all the physical or mechanical properties desired for flexible medical tubing applications. Further, many of these poy mers do not perform. well tnder steam sterilization due to severe softening at teiperatures 25 higher than about 10{ 0 C. As a result. manufacturers are often left to choose the physical and mechanical properties they desire without an option as to whether it can be steam sterilized. As such, an improved polymeric material that can be steam sterilized is desired.

DSCLOSU RE OF INVENTION In a particular embodinent, a flexible tubing material includes a radiation crosslinked blend of a) a first elastoneric polymer including a styrenie thermoplastic elastoner an ethylene vinyl acetate elastoner, a polyolefin elastomer, or combination thereof and b) a second 5 elastomeric polymer including a polyolefin elastomer, a diene elastomer. or combination thereof, with the proviso that the first elastomeric polymer and the second elastoneric polymer are different. In another exemplary embodimenta method of making a material includes providing a first elastomeric polymer including a styrenic thermoplastic elastomer, an ethylene vinyl acetate Selastomer, a polyolefin elastomer or combinations thereof; providing a second elastonieric polymer including a polyolefin elastomer, a diene elastomer, or combination thereof with the proviso that the first elastomeric polymer and the second elastomeric polymer are different; blending the first elasomeric polyner and the second elastomeric polymer; extruding or injection molding. the blend; and crosslinking the blend with radiation. 5 BRIEF DESCRIPTION OF TH E DRAWINGS the present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. FIG. I includes physical properties of exemplary blends of styrenic thermoplasde elastonier and a diene elastomer before crossAinking. 20 FIG 2 inches physical properties of exemplary blends of styrenic thermiopastic elastomer and a diene elastomer after cross-linking. FIG. 3 includes a graphical illustration of Dynamic Mechanical Analysis (DMA) results for exemplary blends of styrenic thermoplastic elastomer and a diene elastomer with and without e-beam cross-linking treatment, 5 FIG 4 includes physical properties of exemplary blends of styrenic thermoplastic elastomer and a diene elastomer tubing before c-beam cross-linking treatment FIG. 5 includes physical properties of exemplary blends of styrenic thermoplastic elastomer and a dine elastomer tubing after e-beam cross-linking treatment, -3- FIG. 6 includes a graphical illustration of Dynamic Mechanical Analysis (DNIA) results for exemplary blends of styrenic thermoplastic elastomer and a diene elastomer with and without e-beam cross-linking treatment. FIG. 7 includes a graphical liistration of Dynamic Mechanical Analysis (DMA) results for an exemplary bnd of a terpolyrner of ethylene, propylene and a diene monomer (EPDM) and ethylene methyl ac rylatc (EMA) with and without c-beam crosslinking treatment FIG. 8 includes a graphical illustration Of tear testing results for exemplary blends of polyolein elastomer and diene elastomer with and without c-beam crosslinking treatment FIG 9 includes a graphical illustration of Dynamic Mechanical Analysis (DMA)results for an exemplary blend of a polyoleln elastomer and a diene elastomer with and without e-beam cross-linking treatment, FIG. 10 includes a graphical illustration ofgel content testing results for exemplary blends of polyolefin elastomer and dicn.c elastomer with beam cross-linking treatment, FIG I1 includes physical properties of eenplary blends of thermoplastic clastomers and onomer elastomers before cross-linking The ise of the same reference symbols in different drawings indicates similar or identical items. DESCRU ION OF THE PREFERRED EMBODIMENT(S) In a particular embodiment a flexible tuing material includes a blend ofa first 0 elastomeric polymer with a second elastomeric polymer. Typically, the first elastomeric polymer is a styrenic thermoplastic elastomer, an ethylene vinyl acetate elastomer, a polyolefin elastomer or combination thereof Typicaly the second elastomeric polymer is a polyolefin elastomer, a diene elastomner, or combination thereof The tiexible tubing materials includes the first elastomeric polymer and the second elastomeric polymer with the proviso that the first elastomeric polymer and the second elastomeric polymer are different. I a particular embodiment, the first elastomeric polymer and the second elastomeric polymer are not both polyolefin elastomers. The blend of the first elastomeric polymer with the seconId elastomer advantageously provides a material that can be radiation crossinked. In an example, radiation -4crosslinking includes gamna radiation and c-beam radiation. Further, the radiation crossi.nked material can be sterilized, Typically, the styrenic thermoplastic elastomer is a stvrene based block copolymers such as styrene -butadiene, styreneisoprene blends thereof, mixtures thereof and the like. In an embodiment, any stvrenic thermoplastic elastomer is envisioned, Exemplary styrenic thermoplastic elastomers include block styrenic block copolymers (SBC) such as styrene butadiene-styrene (5B) styrene soprenestyrene (S1), styrene-ethylene butylene-styrene (SEBS), styrene-ethylene propylene-styrene (SEPS), styrene.-ethyiene-ethylene-butadiene styrene (SF EB), styrene-ethyicne-ethylene-propy lenestyrene (SEEPS), styrene-isoprene 3 butadiene-styrene (SI BS), or combinations thereof Commercial examples include sone grades of KratonlM and Hybrari resins. In an embodimentthe styrenic thermoplastic elastomer contains at least one free olefinic double bond, i.e. an unsaturated double bond. For instance, the presence of the free olefinic double bond in the polymer provides molecular sites that will crosslink under radiation Exemplary styrenic polymers with unsaturated double bonds include styrenie-isoprene-butadiene-styrene (S1B5styrene-isoprene-styrene (SS), stwrene-butadiene~ styrene (SBS1 and the like. In an embodiment, the styrenic thermoplastic elastomer is saturated, i.e. does not contain any free olefinic double bonds. Typically, the styrenic thermoplastic elastomer has a molecular number of at least about 15.000 Mn, such as at least about 25,000 Mn. In an embodiment. the styrenic thermoplastic 3 elastonmer is present at an amount of at least 10% by weight such as at least about 20% by weight, or even at least about 30% by weight of the total weight of the blend Typicalythe level of the styrenic thermoplastic elastoner present in the blend may be optimized based on the final properties desie Typically. the ethylene vinyl acetate elastomer is an amorphous polar polymer 5 "Amorphous" as used herein refers to a polymer that is substantially non-crystalline, ixe with no crystalline melting point The amount of vinyl acetate found in the ethylene viy acetate polymer determines the crystallinity of the polymer. In particular the higher the percentage of vinyl acetate in the EVA copolymer. the more the crystalline regularity of the ethylene chain is disturbed or destroyed. Crystallization is progressively hindered and is substantially absent with 0 an EVA copolymer containing about 50%vinyl acetate, rendering an amorphous polymer in an embodiment, the ethylene viny-i acetate of the present disclosure has a vinyl acetaite content of greater than about 50% by weight of the total weight of the ethylene vinyl acetate. For instance.

the ethylene vinyl acetate has a vinyl acetate content of greater than about 60% by Veight to about 80% by eight of the total weight of the ethylene vinyl acetate, such as about 60% by weight to about 70% by weight of the total eight of the ethylene vinyl acetate. Further, the glass transition temperature, Tg, is typically low for the amorphous polymer. i e, less than about 5 (C. In an embodiment, the glass transitionemperature for amorphous ethylene vinyl acetate is less than about O 0 C, such as less than about 1*C or even less than about -25C. In an embodiment, the ethylene vinyl acetate has a number average molecular weight i) of about 70000 to about 90,000, such as about 80,000 to about 85,000. The ethylene vinyl acetate may have a weight average molecular weight (Mw) of about 250,000 to about 400,000, such as about 3 280,000 to about 350,000. in an embodimentthe ethylene vinyl acetate has a poly dispersity index (Mw/n) of about 3.0 to about 5.0. such as about 3.5 to about 4.0. In an embodiment, the ethylene vinyl acetate has a desirable melt flow index (M ) such as about I to about 7, such as about 1.5 to about 6, at a testing parameter of 190:C/21;1N Generallthe mel viscosity at 200"C with a 100 1/s shear rate may be up to about 600 Pa.s, such as about 400 Pa.s to about 500 5 Pa.s. With a 1000 /s shear rate, the melt viscosity may be up to about 300 Pa.s, such as about 100 Pa s to about 200 Pa.s. In an embodimen, the solution viscosity is up to about 2000 mPass, such as about 200 mPa.s to I 500 niPans at a 15% concentration in toluene or up to about 501000 mPa.s, such as about 7000 niPa.s to 305000 mPa~s at a 30% concentration in toluene A commercially available EVA is ElvaQ" available from DuPont. 0 In an exemplary embodiment, the elastomeric ethylene vinyl acetate polymer has a desirable shore A hardness, such as about 30 to about 40. In contrast, a crystallie polar polymer, such as crystalline EVA typically has a shore A hardness of more than 40. Typically, amorphous ethylene vinyl acetate is synthesized by solution polymerization at a pressure of about 200 bar to about 1000 bar and a temperature of about 5'C to about 120'C' in 25 an embodiment, the amorphous ethylene vinyl acetate may be synthesized by emulsion polynerizatioi conducted at about 1 bar to about 00 bar pressure and temperature of30470C In contrast. crystalline ethylene vinyl acetate is prepared by mass polymerizationaat a pressure of about 1000 bar to about 3000 bar at a temperature of about 15(Y-C to about 350C. In an example. the blend includes the ethylene vinyl acetate present at a range of about 1% 30 by weight to about 99% by weight of the total weight of the polymeric blend in an embodiment, the ethylene vinyl acetate is present at greater than at least about 5% by weight of the total -6weight of the poly metric blend, such as greater than about least about 15% by weight of the total w eght of the polymerc blend. In a particular embodiment. the ethylene vinyl acetate is present at greater than about least about 10" by weight of the total weight of the polymeric blend, such as a range of about 1O by wight to about 90% by weight of the total weight of the polymerie 5 blend, or even a range of about 25) by w eight to about 80% by weight of the total weight of the polymeric blend. Typically, the level of the ethylene vinyl acetate present in the blend may be optimized based on the final properties desired. In a particular embodimentthe blend includes a polyolefin elastomer Any polyolefin elastomer is envisioned, A typical polyolefin may include a homopolymner, a copolymer, a o terpolymer an alloy, or any combination thereof formed Emm a monomer such as ethylene, propylene. butene, pentene, methyl pentene. hexene, octane, or any combination thereof In an embodiment, the polyolefin elastomer may be copolymers of ethylene with propylene or alpha olefns or copolymers of polypropylenewith ethylene or alpha-olefins made by metalocene or non-metallocene polymerization processes. Comrercia polyolefin examples include 5 Affinity' Engage Flexomer i, VersifytInfus Exact, Vistamaxx Softeli and Tafiner Notio produced by Dow, ExxonMobil, LiondelBaseil and Mitsui. In an embodimientthe polyolefin elastomer nay include copolynmers of ethylene with polar viny monomers such as acetate (EVA) acrylic acid (EAA), methyl acrylate{EMA), methyl methacrylate (E MMA) ethy acry late (EEA) and butyl acrylate (EBA). Exemplary suppliers of 0 these ethylene copolymer resins include DuPont Dow Chenical. Mitusi and Arkema etc, In another embodiment, the polyolefin elastomer can be a terpolynier of ethylene, maleic anhydride and acrylates such as LotaderM made by Arkema and EvalloyF produced by DuPont In yet another embodimentthe polyolefin elastomer can be an ionomer of ethylene and acrylicacid or miethacrylic acid such as Surlyn made by DuPont, In an embodiment, the polyalefin is a 25 reactor g eniopiastic polyolefin elastomer, such as P6E2A-005B3 available from Flint Hills Resources. in an enbodment, the polyolefn elastoiners should have fexural mnodulus lower than 200 MIa. Typical, the polyolen elastomer is present an an mouni of at least 10% by weight, such as at least about 20% by weight, or even at least about 30% by weight of the total w eight of the blend i'ypicallv, the level of th-,e pol-yolefin elastomer present, in th blend may he 30 optimized based on the final properties desired In an embodiment, the blend may include a diene elastomer. Any appropriate diene elastomer is envisioned. For instance, the diene elastomer may be polybutadiene arid polyISoprene or their copolymers; it can also he a terpolymer of ethylene, propylene and a diene monomer (EPDMN}. In an embodiment, the diene elastomer may be synthesized by an means envisioned. For instance, the diene elastomer is synthesized by metallocene or non-metallocene polymerization processes. In an exemplary embodiment, the EPDM is reaction product of dienes such as DCPD (dicyclopentadienen ENBI (ethylidene norbornene) and VNB (vinyl norborne). Exemplar EPDM resins are available from ExxonMobil Cherical as istalon? and Dow Chemical as Nordel and other suppliers. In an embodiment, the diene elastomer is present at an amount of at least 10% by weigh such as at least about 20% by weight, or even at least about 30% by weight of the total weight of the blend. Typically, the level of the diene I elastomer present in the blend may be optimized based on the final properties desired, To crosslink the blends by irradiation of c-beam o gamma rays, reactive sites are needed in the blends For instance, in the embodiment when the styrenic thermoplastic elastomer contains at least one free olefNic double ond, the free olefnic double bond inthe polymer provides molecular sites that will crosslink under radiation. In an embodimentif saturated 5 resins are used to make the blends, small amount of radiation sensitizers or crosslnking promoters may be added to assure suffiDient crossiinking and prevent degradation of the materials caused by chain scission during exposure to radiation. Any reasonable radiation sensitizer may be envisioned Exemplary radiation sensitizers are typically multiftunctional monomers such as: diethylene glycol dimtharylae (Driethyloproane D trimetharcylate (M iA), dipenta crit-hritoarylate(DEA) tetramethyoo methane tetraacrylate (TM MT-iA, triallyI cyanurate ([AC), to iene diisocyanattc (TIhexamethylene diisocyanate (HMDI), m-phenyene dimaleimide, the like, and any combination thereofl When used, the radiation sensitizer may be present at about (15% to about30%by weight of the total weight of the blend. In an embodiment a crossinking promoter may be used to provide reactive sites to crosslink the blends by irradiation Any reasonablerosslinkingpromoter may be envisioned. Exemplary crosslinking promoters include pdymers with unsaturated double bonds in the molecular chains such as polyisoprene, polybutadiene, EPDM., SISABS, the like, and any combination thereof in a particular embodiment, the unsaturated double bonds of the 30 crosslinking promoters will crosslink by c-beam or gamma rays. Typically, the crossinking promoter may be present at greater than about 5.0% by weight of the total weight of the blend. -8- Inm an an oil may be used in the blend Any suitable oil may be envisioned In a particular embodiment the oil is mineral oil that is either paraffinic or naphthenic or a mixture of paraffmic or naphthenic with zero aromatic content. For instance, a mineral oil may be used at an amount of about 0% by weight to about 70% by weight of the total weight of the blend. In an embodiment, the blends are substantially oil-free "Substantially oil-free" as used herein refers to a blend that includes nineIral oil present at less than about 0 1% bg weight of the total weight of the blend, For instance the styreniC thermoplastic elastoners may be melt processible without the addition of an extending oil or plastiCizer. In an embodiment, the ethylene vinyl acetate elastomers may be melt processible without the addition of an extending ) oil or plasticizer. in an exemplary embodiment, the blend further includes any additive envisioned such as a lubricant, a filer, a plasticizer, an antioxidant, or ainy combination thereof Exemplary lubricants inchide silicone oil, waxes slip aids, antiblock agents, and the like. Exemplary lubricants further include silicone grafted polyolefm polyethylene or polypropylene waxes, Oleic acid amide, erucamide, stearate, fhtty acid esters, and the like. Typical, the lubricant may be present at less than about 2.0% bv weight of the total weight of the blend. In an embodiment, the lubricant may' be present at less than about 05% by weight of the totalweight of the blend. Exemplary annioxidants include phenolic. hindered amine an tioxidants. Exemplary fillers include calcium carbonate, talc, radio-opaque fillers such as barium sulfate, bismuth oxychloride, any ) combinations thereof and the like. Exemplary plasticizers include any known plasticizers such as mineral oils and the like. Typically, an additive may be present at an amount of not greater than about 50% by weight of the total weight of the blend, such as not greater than abouti40% by weight of the total weight of the blend, or even not greater than about 30% by weight of the total weight of the bient. Alternatively, the blend may be free of lubricants fillers phisticeersand 5 antioxidants, The components of the blend of the fist elastomeric polymer with the second elastomeric polymer ma' lie melt processed by any known method to form the blend. In an embodiment, the tirst elastomeric polymer with the second elastomeric polymer may be melt processed by dry blending or compounding. The dry blend may be in powder, granular, or pellet bnm The blend 0 can be made by a continuous twin-ciew compounding process or batch rented Banbury process. Pellets of these blends may then be fed nto a single screw extruder to make articles such as flexible tubing products. Blends can also be mixed in a single-screw extruder equipped with -9mixing elements and then extruded directly into articles such as tubing products, In a particular embodiment, the blend can be met processed by any method envisioned known in the art such as laminating, casting, molding, and the like, In an embodiment, the blend can be injection molded. in an embodiment, any article can be made out of the blends depending on specific S application needs The resulting articles are then irradiated using c-beam or gamma-rays in a batch process or a rol-to-roll process. i a particular embodiment, c-beam radiation includes an electron beam generated by a Van de GJraaff generator, an electron-accelerator. E-beam with energy of between about 0,5 Mev to about I0.0 Mev from an electron beam accelerator can be used to cmosslink the blend of the resulting article, Doseshbetweer about 10 Ky to about 200 a KGy (about I Mrad to about 20 Mrad) are typical, In an exemplary embodiment for crosslinking of the blend by gamma rays about I Mrad to about 10 Mrad of radiation from a Co source can be used. The polymeric blends advantageoeuly can withstand sterilization processes In an embodiment, the polymeric blend is sterilized by any method envisionedt For instance, the 5 p blend is sterilized after radiation crosslinking Exemplary sterilization methods inside stean ganuna, ethylene oxide, h-beam techniques. combiations thereof andthe like In a particular embodiment, the polymeric blend is steriized by steam sterilization. In an exemplary embodiment. the polymeric blend is beat-resistant to steam sterilization at temperatures up to about 1 21 C for a time of up to about 30 minutes. I an embodiment the f polyneri blend is heat resistant to perform steam sterilization at temperatures of up to about 135C fr a time of up to about 20 minutes. In an embodiment the polymeric blend may be formed into a single layer article a muli layer article, or can be laminated, coated or formed on a substrate. Miultilayer articles may include layers such as reinforcinglayers adhesive layers, barrier layers, chemically resistant 25 layers, metal layers, any combination thereofand the like, The blend can be formed into any useful shape such aslm, sheet tubing and the like. The polymeric blend may adhere or bond to other substrates including polyolefins (polypropylene (PP) polyethylene (PE), and the like) and styrenics(polystyrene (PS). acrylonitrile butadiene styrene (ABS), high impact polystyrene (IIPS), and the like) 30 In a particular embodiment, the polymeric, blend may be used to produce tubing and hoses, For instance, the polymeric blend can be used as tubing or hosing to produce low toxicity pump 10tubing, reinforced hosingchemicall resistant hosing, braided hosing, and low permeability hosing and tubing. For instance, tubing may be provided that has any useful diameter size for the particular application chosen. In an embodiment, the tubing may have an outside diameter (OD) of up to about 2.0 inches, such as about 0.25 inch, 050 inch. and 1 0 inch. Tubing of the 5 polyrmeric Mend advantageously exhibits desired propertes such as chemical stability and increased lifetime, For example. the tube may have a pump life greater than about 10 hours. such as greater than about 20 hours, or even greater as measured at 600RPM usn a standard pump head. The present embodiments Can produce low toxicity articles having desirable mechanical 0 properties. In a particular embodimentthe radiation crosslinked article fored is substantially free of plasticizers or other low-molecular weight extenders that can be leached into the fluids it transfers. "Substantially free" as used herein refers to a radiation crosslinked article having a total organic content (TOC) (measured in accordance to ISO 15705 and EPA 410.4) of less than about 100 ppm. 5 I embodimentthe resulting radiation crosslinked articles may have further desirable physical and mechanical properties. For instance, the radiation crosslinked articles are flexible., kink-esistant and appear transparent or at least translucent. In particular, the resting radiation crossliniked articles have desirable flexibility, substantial clarity or translucency desirable glss transition temperaturesdesirable low temperature performance, and chemical resistance to oils o and alcohols. For instance, the radiation crosslinked articles of the first elastomeric polymer with the second elastomeric polymer may advantageously produce low durometer articles. For example. a radiation crossiinked article having a Shore Aduroeer of between about 40 and about 90 haviiig desirable mechanical properties may be formed. Such properties are indicative of a flexiblec material 25 In addition to desirable hardnessthe radiation crosshnked articles have advantageous physical properties, such as desirable ultimate elongation and. low compression set at elevated temperatures. Ultimate elongation is determined using an Instron instrument in accordice with ASTM D-412 testing methods. For example, the radiation crosslinked articles may exhibit an ultimate elongation of at least about 400%. such as at least about 500%, such as at least about 30 600%, or even at least about 700%. In an embodiment the compression set in accordance with ASTM D 395 measured at about 1I C of the radiation crosslinked articles is less than about 50%. Applications for the polymeric blend are maerous In particularthe nontoxic nature of the polymeric blend makes the material useful for any a ppication where toxicity is undesired, 5 For instance, the polymeric blend has potential for FDAU, SP, and other regulatory approvals. in an exemplary embodiment, the polymeric blend may be used in applications such as industrial, medical, health care, biopharmaceutica drinking water, food & beverage., laboratory, and the like. In an embodiment, the polymeric blend may also be safely disposed as it generates substantially no toxic gases when incinerated and leaches no plasticizers into the D enviromnent if land filled. EXAM PLE S EXAMPLE 1. Blend of styrenic thermoplastic elastomer and a polyolefin Kraton D210-9 is tested for mechanical and physical properties. In general terms, Kraton 12109 is a mel compounded inaterial of styrenC TPE resin, polyolefin, and mineral oil obtained 5 from Sonnebon, Petrolia PA. Kraton D2109 is injection molded at a flat profile of about 400F into plaques for Shore A hardness, tensile and high temperature compression set testing. It is also directly extruded into 03 outsider diameter (OD) Xt 0.25"nner diameter (ID) tubing. Processability is good as there are no problems with tube dimensions and temperature window. t is silky to touch (as opposed to being "grabby" as is the case with C-lex) and has a "silicone o feelI. The tube noticeably displayed signs of resilience and elasticty The plaques and tubing coils are irradiated w th -beamn at 2 different dosage rates of about 6.8 MRad and about 136 MRad corresponding to 4 and 8 passes each of about 1 . MRad. The irradiated plaques are then tested for hardness. tensile and compression set as measured by ASNTM D-3 95, The resutts are tabulated in Tables I and 2 Santoprene obtained from Advanced Elastomer Systems is used as 5 comparison tubing with three grades tested (hr compression set, Table I Properties Unexposed E-beam Exposed Kraton D2109 4 Passes i Passes --------------------- - -------- ----------------- ------- --------------------------- Shore A Hardness 49 50 52 Break Strength, psi5 75 870 1045 Ultimate Eongation % 970 735 120C Compression Set 32,8 17,8 IL5 Table 2 Santoprene Grade 120*C Compression Set ---- - ---- - - . -------------------- 828164 212 8281-65 279 -8281---75- - ---- ~------- -- -------- - --------- 8281-75 30-2 --------------- ------------ -- ---- L - --------- ~--- ---- J The ebeam erosslinked tube can be heat sealed, although at a higher temperature setting than normal with standard C-Flex. owe-ve, heat setting tp ure h to be increased from 160*C for standard C-Flex tube to about 1 S4C to heat seal the radianon crosslinked Kraton D2109 tube, The irradiated Kratoi 12109 product exhibits higher break strength, lower elonugation at break and dramatically Improved high temperature (12f*C) compression set that excels Santoprere's performance, The irradiated Kraton )D2109 compound yields a hardness of about SA about 1000 psi of break strength, about 735% ultimate elongation and compression set of about 12% at about 1200C. K on 1)109 pump tubing (0.25 x O8inches irradiated for up to 8 passes of eleam for effecting crosslinking is subjected to peristaltic pump test at 600 RPM using a standard head. The irradiated tubing is also tested for pump life at 600 RPM using an EZ load head. For the sake of comparison, clear R70-374 C-Flex size 17 tubing is also tested on EZ load. As can be seen from results in Table 3 below, XL-CFlex (Kraton D2.109) is pumped on the standard head for about 50 hours before failure. Surprisingly, the same tubing pumped for about 1000 hours on EZ load before failure. In comparison, clear C-Flex R70-374 is pumped foi about 10 hours both on standard and EZ load heads before failure, indicating that the design of the pump head is -13inconsequential Also, the spallaion. behavior of R70-374 is visually worse than irradiated Kraton D2109 (XL-CFlex) that shows minimal spallation (as visually observed during the pump test) I Table 3 Pump Life (hours) C Flex d Z XL-Clex (Kraton D2109) translucent ) 51000 R70-374 (clear) 10 10 R70-001 (opaque C-P pump tubing) 50 Not tested AdvantaRlex (milky but translucent) 0O Not tested EXAMPLE 2, Bilends of EPD\M wih Saturated Styrenie Block. Copolymers (SBC) To make flexible tubingblends of diene elastomers and styrenic thermoplastic -elastomer with hardness ranging from Shore A of about 40 to about 90 can be used. Diene elastomers and 5tyTniC thernmoplastic elastomers used to demonstrate the concept of making croshnkable blends by ionizing radiation are listed in Table 4, Four styrenic thermoplastic elastomers of diflorent chemistries and physical properties are chosen. Kraton C 1643M and Kraton MD 6945 are resins produced by Kraton Polymers and are based onchemistry of polystyrene-- block poly(etbylen e-butyiene)iock.polstyrene (SEBSF Hybrar 7125 has a chemical structure of polystyreneblockpoly(ethylene-co-propylene)-block-polystyrene steps) , while I-ybrar 7311 has a chemical structure of polystyrene-block-poly[cthylne-co-ethyleneo-propyene}}block polystyrene (SEEPS), The Hlybrar resins are supplied by Kuraray Co. Ltd, Kurashiki, Japan. EPDM is chosen to maihe crosslinka blends. In an embodiment, EPDM resins made by the metallocene polymerization technology can be used in order to use common thermoplastic extrusion techniques to make tubing out of the blends. Unlike EPDM rubberswhich are completely amorphous and thus are in bale form at room temperature. the metallocene EPDM resins can be produced in pellet forrn due to some degree of crystallinity (typically in the range - 14of about 5% to about 20% as measured by DSC at I 0 mndexisting in this type of materials. Nordel IP 4725 provided by Dow Chemical is the metallocene EPDM resin selected to make crosslinkable blends in this Example. Nordel 1P4725 resin is in transparent pellet form and is reported by the producer to have about 12% crystallinity Table 4: Styrenic thertoplastic elastomer and EPDM ramw materials -- - - -- - - - - - - - - - - - - ----------------......................... 6 i- .... ------------ MR 100% Tensle Hardress! Materials Grade g/10m n Modulus Strength Shore A 230 C MPa MPa Kraton G 1643M 18 52 IS U Kraton MD6945 4 308 12 8 10 SBC Res n Hybrar 725 4 17 132 Hybrar 7311 2 41 0.6 9 .3 EPDM orde 4725 NA 17 4 To make siall batches ot t blends, the polyme components are mixed in a abender mixer at different ratios at about 200*C and about 60 rpm for about 5 mino The resting mixtures arc used to mold about 1mm thick slabs in a Carver hot press. Dog-bone testing specimens are cut out of the slabs for tensile test. FIG. 1 lists the mechanical and optical properties of blends before crosslinking. it can be seen that transparent blends result for the EPDMiKraton MD6945 and EPDM/Hybrar 7311 systems at all mixing levels, while translucent J blends are obtained for blends of EPDM(Kraton 01643 and EPDM/Hybrar 7125. Hardness of these blends ranges from Shore A of about 40 to about 70, which is within the desired range Or flexible thermoplastic elastomer tubes. The elongation of the resulting bleids is usually higher than about 1000%" The modulus of the blends goes generally between the two extremes of raw resins and the tensile strength of the blends is higher than those for the raw resins. To crosslink the blends. molded slabs are sent to E-BEAM Services Inc. in Lebaron, Ohio for crosslinking treatment. 10 samples fromnLhei EPDMiKraton MD6945 and EPDMI / Hybrar 7311 series are exposed to about 6.8 Mrad (4 passes x L Mrad / pass) e-beam of about 10 MeV. After c--beam treatment, no samples show any changes in clarity or yellowing due to degradation. 15- Gel content tests are conducted by soaking a crosshnked sample in boiling hexane for about 12 hrs and then measuring percentage of remaining solid content in the saniple About 40% to about 70% by weight gel con ient of the total weight of tie blend is measured fr the c-beam treated blends of EPDM/Kraton MD6945 and EPDM /HRybrar 7311 depending on their compositions. For untreated EPDM/styreni c thermoplastic elastomer samples 0% gel content is found (completely dissolved), By comparing physical properties for crosslinked samples in FIG. 2 and results of corresponding un-crosshnked samples in FIG.I, no significant changes are found in the e-beam treated blends in. terms of hardness and modulus, slight increase in tensile modulus is found after e-beam treatment, while elongation of the crosslinked samples is seen to decrease by about 10% to about 20%, To check the influence of e-beam exposuto heat resistance of the blends. dynamic mechanical analysis (DMA) is performed in the temperature range of about -SOC to about 200*C This test can determine the glass transition temperature, melting point of a thermoplastic by following changes in viscoelastic behavior of a miaterialhvith temperature. In atypical DMA test, the storage modulus measures how stiff anid elastic the material is, the loss modulus indicates how fluid-like andvscous the material is and the loss tangent is the ratio ofloss modilus to storage modulus. For a polymer material to exhibit some heatresistance so that no deformation occurs under its own weight when exposed to elevated temperatures, the storage modulus of the material is typically at least above about 1 MPaI, while the loss tangent vale is typicallv lower than about 0.25 MPa, Using these criteria, the maximn temperature that a thermoplastic elastomer material can be exposed to for short time. such as a steam sterilization process, carn be estimated. FIG 3 shows the change of storage modulus and loss tangentvith temperature for the blend of 50/50 Nordel IP4725/EPDM. Without croAsslinking by c-beam, storage modulus of the blend shows a sharp drop above about 1u00, u stein a melting and S fow behavior. Storage modulus fails below about I MPa at about 95*C and loss tangent rises above about 0.25 at about 82*C. therefore the maximum short-term exposure temperature for this blend will be around SOtC After crosslinking by about6.8 Mrad e-beam, the storage modulus of the 50/50 Nordel lP4725/EPDM blend displays a plateau from about 70tC and about 2004C. It does not fa)l below about I MPa until about 160tC The loss tangent is not below about 0.25 0 MPa even at about 195"C. Therefore, this erosslinked blend is suitable for steam sterilization processes at both about 12 ItC and about 1 35'C. - 16- EXAMPLE 3. Tubing Made of EPDM/styrenic thcrnoplastic elastomer bends; To make flexible tubing of the blends, mixtures of 50/50 Kraton G3 1643MN1ordel IP45 with or Without lubricating additives is compounded through a o-rotating twin-screw extruder and cooled by a water bath and cut into pellets. The resulting pellets are later fed into a single 5 screw extruder, which is equipped with a tubing die. A regular 3-zone screw is used for the tubing extrusion. The temperature profile is set at about 280, about 320F and about 400F -for three segments of the extruder. The adapter and die temperatures are set at about 405'F and about 4154F, respectively The polymer met flowingout of the die is discharged into a submerging water tank for cooling, where the extrudate is frozen into a tubing shape, internal air pressure, screw speed and pulling rate are combined to control the tubing dimensions and wall thickness Translucent and flexible tubing with dimensions of 0,25" fbr ID and 0,375" for (D is obtained through the above coipoundnig and extrusion procedures When an extruder with mixing screw sections is available, the twin screw compounding process can be omitted. Flexible tubing can be extruded from the blends by feeding dry Wiends of these resins directly 5 into the extruder due to relatively high coipatibility between EPDM and styreie the elastomers. Tubing formulations and resulting tubing properties without c-beam crosslinking treatment are shown in FIG. 4. As low surface friction usually helps with pumping life in peristaltic pumping applications, three lubricants are evaluated at about 1% by weight addition level of the o total weight of the bMend. A 50% by weight silicone oil (vinyl terminated polydimethyl siloxane) master batch in EVA carrier resin is obtained from Dow Coring Lubotene REF4006 is a silicone grafted low density polyethylene (LDPE) resin obtained from Optatch Corporation Aipacet i02468 is a master batch of Eruamide in LDPE supplied by Ampacet Corporation. At about L.0% by weight addition level of thetotal weight of the blendall three lubricants show no Z5 significant effects on the kink resistnce, which is measured by MBR (minimum bending radius), clarity and mechanical properties of the tube. Lubricants do increase pumping life of the tubing when. these tubes are used as the pumping segment in the standard head of a Masterfex peristalic pump. The pumping tests are run at a speed of about 400 rpm in this study, Without lubricant, the tubing could only operate about 2 hours due to wearing caused failures. By adding 30 about 1 0% by weight of lubricant, pumping life of the tubing is extended up to about 6-11 hrs. - 17 - The tubes extruded from blends of 50/50 Kraton G I 643MiNordel IP45 are also crosslinked by about 6.8. Mrads e-beam treatment FIG, 5 lists properties of the tubes after e beam crsslinking. Compared to the corresponding results in FIG 4. it is clear that the c-beam crosslinking process do not affect clarity, kink resistance. hardness and tensile mechanical 5 properties. However, a very significant improvement can be seen n pumping life of the t bing. The unlubricated tubing raises pump life from about 2 hIrs to about 24 hirs,. while the lubricated tubes improve their pump lives from about 6. 1 hrs to the rame of about 1 3-39 brs. Furthermore, significant improvement in heat resistance of the tubes can be achieved through the c-beam crosslinking treatment. As lustrated by the DMA results in FIG. 6, the unlubricated 3 tubing of 50WO Kraton C 164M/Nordel P45 can only withstand short exposure to about 80*C, while the c-bem crosslinked tube can be used at about , 30*C for short term. Therefore this crosslinked blend is suitable for steam sterilization processes at both about 121 QC for a time of up to about 30 minutes and about 135"C for a time of up to about 20 minutes. EXAMPLE 4: Blends of polyolefin elastomers and diene elastomers 5 The following blends of polymers are mixed in different ratios at about 200*C to 23Y4C using a Brabender mixer. The resulting mixtures are molded into 2mm thick slabs and dog bone tCestig specimens are cut out of the slabs for tensile and ear testing in accordance with ASTM 638 and ASTM 624, respectively. Table S Sample Storage modulus Storge modulus Tg at Tan Deha (MPa) at .70*C (NPa) at 100C carve (C) .................-- - - ---- -- ......... - - - -------------- - ---- EPDM /EMA 1987 0489 -19.67 EPDM/EMA . 1808 1317 17 50 4 e beam passes EPDM/EM A 1796 1.633 -16.69 S beam passes EPDMIEMA 1735 1505 612 18 Dynamic mechanical analysis of the EPDMJEMA blend wth and without e-beam irradiation can be seen in FG,7 6, S MRad (4 passes) of e-beam irradiation sufficiently crosslinks the EPDMG/fMA blend, For instance, the EPM.A/EMA blend that has notbeen e beam irradiated is clearly not crosslinked as evidenced by the dramatic drop in storage modulus s as the temperature increases. Further, 6.8 Mrad (4 passes) of e-beam irradiation is sufficient to create a blend with heat resistanceat temperatures greater than I 00*C and in particular, steam sterilization processes at both about 121 C for a time of up about 30 minutes and about 13500C for a time of up to about 20 minutes. Four samples are chosen to be extruded into tubing 0,5625 inches OD X 0,375 inches [D D for evaluation. The formulation and properties before and after c-beam treatment can be seen in Tables 6 7, and 8. Table 6 Materi Grade Amount H urdness (Shore A) E! ax 360 100 75 Polvolefin resin Versify 2400 100 g 68 Affinity EG8200 100 g 70 Engage 8 180 100 g 63 EPDM Nordel IP4725 100 g 60 Table 7. Properties before c-beam treatment Material Shore A Yon n- 00%" 300% Tensile Elongation hardness modulus I Modulus Moduls Strength (%) (MPa (MPa) (MPa) (Ml a) IPDMIEivax 77 113 2J 15 1048 EPDM/Versify 62 7.0 1 0,8 1 39 1255 E M/Affinity 66 6.5 .20 134 1232 EPDM Engage 64 5.3 18 1 159 1244 19 Table 8, Properties afler cbeam treatment Material Shore A Young 100% 300% Tensile Elongation hardness modulus Modulus Modulus Strength (%) (MPa) (NIMP) (MPa) (MPa) t ~ ~ ~ ~ ~ ~ ~ .... ....... "..........-.----_ _ . ........ _ EPIDMEl vax 76 121 30 1.7 190 81 MNrif 60 6.9 1.7 09 111 982 EPDM/Affinity 67 6.8 20 1 15 J081 EPDMEngage 64 53 1.8 1-0 1,56 99 As seen in Tibles 5-8, the crosslinking of the blends provides materials with advantageous properties Aer e amrn irradiation, the material remains flexible. The materials exhibit a 5 negligible change in Young modulus, 100% Modulus, 300% Modulus. and tensile strength after e-beam treatment. A er e-beam treatment. the material shows a slight decrease in Elongation which indicates no chain scission of the material. Tear testing can be seen in FIG, 8. FIG. 9 is an illustration of the dynamic mechanical analysis (DMA) of a blend of EPDM/Affinity. The graphs show that there are no negligible a change in properties from 4 to 8 e-bam passes. As seen in FG. 9, 6.8 Mrad (4 passes) of e beam irradiation is sufficient to create a blend with hea esistance at temperatures greater than 100Ci and in particular, steam sterilization processes at both about 121"C for a ume of up to about 30 minutes and about 135"C for a time of up to about 20 minutes. Gel content testing as described above is pertbrmed on the materials of Tables 5, As seen 15 in FIG. 10, the gel content testing illustrates that there are no significant changes in the cross-link density between 4 and 8 c-beam passes. EXAMPLE 5- Bends of thermoplastic elastmers and ionomers. The following blends of polymers are mixed in different ratios at temperatures ranging from about 300"F to about 400" using a Brabenider mixer. The blends are compression molded 20 at a flat profile of about 375"F into plaques for Shore A hardness. Young modulus (E), 100% Modulus elongation (E-I 00%). elongation (c), tensile strength and tear strength testing. Shore A hardness ranges from about 50 to about 85, indicative of a soft. flexible material. -20 - Two samples are chosen to be extruded into tubing 0385 inches OD X 0,255 inches ID for pump life evaluation, before and after e-beam treatment; Processability is good as there are no problems with tube dimensions and temperature window. Pump lifb is tested at 600 RPM using an EZ load II pump head. Results can be seen in Table 9, Table 9. Pumpie of styrenic thermoplastic elastomer/iononer blend Material Average Pump fe (hours) Suriy 8320/SEBS G1643 (5050 blend) 1.90 Surlvn 8320/SBS G1643 (50:50 blend) 4,83 4 pass E-beam Survn 8320/SEBS G 645 (50:50 blend) 4. 20 Survn 8320iSEBS G1645 (50:50 blend) 4.83 4 pass E-beam As seen in Table 9. irradiation of the tubes increases the pumap life of both blends. Note that not all of the activities described above in the general description or the examples are required, that a pation of a specific activity may not be required, and that one or C more further activities may be performed in addition to those described Still further, the order in which activities are listed are not necessarily the order in which they are performed. in the foregoing specification the concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can e iade without departing from the scope of the invention as set forth in the S claims below. Accordingly, the specification and figures are to be regarded. in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of invention. As used herein, the terms "comprises," conpri sing," "includes? "including,"'has." "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For 0 example, a process, method, article, or apparatus that comprises a list of features is not 21 necessarily united only to those features but rnay include other features not expressly listed or inherent to such process. method, article. or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inchusive-or and not to an exclusie-or. For example, a condition A or B3 is satisfied by any one of the followin: A is true (or present) and B is fadse (or not present), A 5 is false (or not present) and .13 is true (or present),,and both A and B are true (Or present). Also, the use of "a" or "an" are employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant othenvise. 0 Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments; However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronotniced are not to be construed as a critical, required, or essential feature of any or all the claims. 5 After reading the specification, skilled artisans will appreciate that certain features are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely various features that are. for brevity described in the context ofa sigle embodient, may also be provided separately or in any subeombination. Further, references to values stated in ranges include each and every value .D within that range. -22

Claims (21)

1. A flexible tubing material comprising a radiation crosslinked blend of: a) a first elastomeric polymer including a styrenic thermoplastic elastomer, an ethylene vinl acetate elastomer, a polyolefin elstomer, or combination thereof; and b) a second elastomeric polymer including a polyolefin elastomer, a diene elastomner, or combinationhereof with the proviso that the first elastoneric polymer and the second elastomeric polymer are different. 2, The flexible tubing material of Claim I. wherein the styrenic thermoplastic elastomer includes styrene-btadiene-styrene (SB[S), styrene- isoprene- styrene (SI5),styrene-ethylene butylene-styrene (SEBS), styrene-ethylene propylene-styrene (SEPSstreneethylene-ethylene badiene-styrene (SEEBS),styrene-ethylene-ethy lene-propylene-styrene (SEEPS), styrene isoprene-bhutadiene SIBS or combinations thereof.

3. The flexible tubing material of claim 2, herein the styrenic thermoplastic elastomner includes at least one free olefimic double bond.

4. The flexible tubing material of any one of claims I wherein the polyolefin elastomner includes polyethylenecopolymers of ethylene with propylene, copolymers of ethylene with alpha-olefins, copolymers of ethylene with polar vinyl monomers, terpolymers of ethylene. maleic anh-vdride, and acrylates, ionomers of ethylene and acrylic acid, ionomers of ethylene and methacrylic acid, or combinations thereof

5. The flexible tubing material of any one of claims 1-4, wherein the polyolefin elastomer has a flexural modulus lower than about 200MPa.

6. The flexible tubing material of any one of claims 1-5. wherein the diene elastomer is ethylene propylene dine monomier (EPDM).

7. The flexible tubing material of any one ofelaims 1-6, comprising a lubricant present at less than about 1.0% by weight of the total weight of the blend. - 23- 8, The flexible tubing material of claim 7, wherein [Le hibricant is present at less than about 0, 1% by weight of the total weight of the blend.

9. The flexible tubing material ofany one of claims 1-8 further comprising a inneral oil present at about 0% by weight to about 700% by weight of the total weight of the blend.

10. The flexible toting material of any one of claims l1-9, further comprising a radiation sensitizer, a crosslinking promoters. or combinations thereof

11. The flexible tubing material of clain 10, wherein the radiation sensitizer is present at about 0:5% by weight to about 3 0% by weight of the total weight of the blend,

12. The flexible tubing material of claim 10, wherein the crosslinking promoter is present at greater than about 5.0% by weight of the total weight of the blend.

13. The flexible tubing material of any one of claims 1-12, wherein the radiation crosslinked blend has a shore A durometer of about 40 to about 90.

14. The flexible tubing material of any one of claims 143, wherein radiation crosslink includes gamna radiation, e-beam radiation, or combination thereof

15. The flexible tubing material of any one of claims 1-14, wherein the radiation crosslinked blend is heat resistant to steam sterilization temperatures of atleast about 121'C,

16. The flexible tubing material of claim 5 wherein the radiation crossinked blend is heat resistant to steam sterilization temperatures of at least about 1 35* 17, The flexible tubing material of any one of claims 1-16. wherein the radiation crosslinked blend is formed into asingly layer tube or a multi-layer tube.

18. The flexible tubing material of any one of claims 1-17, haviiigsubstantial transparency, -24 - 19, The flexible tubing material of am one of claims 118, wherein the radiation crosslinked blend has a pump life of greater than about 50 hours as measured at 60ORPM using a standard head, 20 The flexible tubing material of any one of clims 1 19, wherein the radiation crosslinked blend has a total organic content (TOC) of less than about 1,00 pp.

21. A method of making a material comprising: providing a fist elastomeric polymer including a styrenic thermoplastic elastomer, an ethylene vinyl acetate elastomer, a polyolefin elastomer, or combinations thereof; providing a second elastomeric polymer including a polyolefin elastomer, a dine elastomer, or combination thereof, with the proviso that the first elastomeric polymer and the second elastomeric polymer are different; blending the first elastomeric polymer and the second elastomeric polymer; extouding or injection dlding the bld;and erosslinking the blend with radiation.

22. The method of chaim 21, wherein strenic thermoplastic elastomer includes styrene-butadi enestyrene (SBS), styrene-isoprene-styrene (SIS), styrene-ethylene butylene styrene (SEBSt styrene-ethylene propylene-styrene (SEPS),styrenesethylene-ethylene butadiene-styrene (SEEBS) styrene-ethyleneethylene-propy I ene styrene (SEEPS), styrene isoprene-butadiene sibsS), or combinations thereof

23. The method of claim 22, wherein the styrenic thermoplastic elastomer includes at least one fire olefinic double bond.

24. The method of any one of claims 21235 wherein the polyolefin elastomer includes polypropylene, polyethylene. copolymers of ethylene with propylene, copolymers of ethylene vith alpha-olefins terpolymers of ethylene, propylene, and a diene monomer copolymers of ethylene with polar vinyl monomers, terpolymers of ethylene; malcic anhydride, and arylates, imnomers of ethylene and acrylic acid, ionomers oftethylene and methacryhe acid, or conbinations thereof -25- 25 The method of any one of claims 21-24, wherein the polyolefi. elastomer has a flexurai modulus lower than about 200MPa. 26 The method of any one of claims 21-25,wherein the diene elastomer is ethylene propylene diene monomer (EPDM) 27, The method of anv one of claims 21-26, wherein the blend further includes a lubricant of less than about 10% by weight of the total weight of the blend. 28 The method of claim 27, wherein the lubricant is less than about 1% by weight of the total wei ght of the blend. 29, The method of any one of claims 21-28, further comprising a mineral oil present at about 0% by weight to about 70.0% by weight of the total weight of the blend, 30, The method of any one of claims 21 -29 further comprising a radiation sensitizer, a crosslinking promoter, or combinations thereof 3 The method of claim 30, wherein the radiation sensitizer is present at about 05% by weight to about 3.0% by weight of the total weight of the blend.

32. The method of laim 30, wherein the crosslinking promoter is present at greater than about 5.0% by weight of the total weight of the blend 33 The method of any one of claims 21-32. wherein extruding or injection molding the blend includes extruding or injection molding the blend into a singly layer tube or a multi-layer tube. 34 The method of any one of claims 21-33, wherein crosslinking the blend is by gamma radiation, c-beam radiation, or combination thereof 35; The method of any one of claims 21,34, further comprising the step of sterilizing the radiation-crosslinked blend. - 26- Z6.The metnhod orflaim 3s where the radiation crossnked lend is sterilized by steam sterilization at a temperature of at least Ta 21 .

37. The eo~d of clam 36, wherein the bliaoeoslne end is sterd ized by steam sterilization at a temperature of at least about 135'C, -27-