阅读说明：本技术 医用管以及用于制造其的组合物和方法 (Medical tubes and compositions and methods for making the same ) 是由 D·杜波伊斯 A·巴塔查里亚 于 2019-09-10 设计创作，主要内容包括：本发明公开了一种医用管,其包含式A-B-A、(A-B-A)<Sub>n</Sub>X或(A-B)<Sub>n</Sub>X的氢化的苯乙烯嵌段共聚物,其中n为2-30的整数,X为偶联剂的残基；在氢化之前,每个A嵌段为真峰分子量为5-15kg/mol的单烯基芳烃均聚物嵌段,每个B嵌段为真峰分子量为30-200kg/mol的受控分布的共聚物嵌段；所述氢化的苯乙烯嵌段共聚物具有按中间嵌段的总重量计为35-50wt％的中间嵌段聚(单烯基芳烃)含量,和使其可用于制备具有抗扭结性的医用管的物理性能。(The invention discloses a medical tube, which comprises a formula A-B-A, (A-B-A) n X or (A-B) n A hydrogenated styrenic block copolymer of X, wherein n is an integer from 2 to 30 and X is the residue of a coupling agent; before hydrogenation, each A block is a mono alkenyl arene homopolymer block with a true peak molecular weight of 5-15kg/mol, and each B block is a controlled distribution copolymer block with a true peak molecular weight of 30-200 kg/mol; the hydrogenated styrenic block copolymer has a midblock poly (monoalkenylarene) content of 35 to 50 wt%, based on the total weight of the midblock, and physical properties that make it useful for preparing medical tubing having kink resistance.)

1. A medical tube comprises formula A-B-A, (A-B-A)_nX、(A-B)_nA hydrogenated styrenic block copolymer of X or a mixture thereof, wherein n is an integer from 2 to 30 and X is the residue of a coupling agent;

wherein, prior to hydrogenation, each A block is a mono alkenyl arene homopolymer block having a true peak molecular weight of 5 to 15kg/mol, each B block has a true peak molecular weight of 30 to 200kg/mol and is a controlled distribution copolymer block of at least one conjugated diene and at least one mono alkenyl arene, the styrene block copolymer having X has a coupling efficiency of 30 to 95%, and a mid-block mono alkenyl arene block index of 3 to 15%, wherein the mono alkenyl arene block index is the proportion of mono alkenyl arene units in a block B having two ortho mono alkenyl arenes in the polymer chain; and

after hydrogenation, 0-10% of the arene double bonds are reduced and at least 90% of the conjugated diene double bonds are reduced;

wherein the hydrogenated styrenic block copolymer has a midblock poly (mono alkenyl arene) content of 35 to 50 weight percent, based on the total weight of the midblock; and

the hydrogenated styrenic block copolymer has: a melt flow ratio of 1.0 to 10.0, as determined according to ASTM D-1238 at 230 ℃ and under a load of 2.16 kg; a Shore A hardness of 60-80, as determined according to ASTM D-2240; a DMA peak tan delta temperature at 1Hz of 0 to 40 ℃ as determined according to ASTM D-4065; and an order-disorder transition temperature of 200 ℃ to 300 ℃.

2. The medical tube as claimed in claim 1, wherein the hydrogenated styrene block copolymer has a mid-block vinyl content of 30 to 90 mol%.

3. The medical tube as claimed in claim 1, wherein the hydrogenated styrene block copolymer has a tensile strength of 10-30 MPa.

4. The medical tube as claimed in claim 1, wherein the hydrogenated styrene block copolymer has a rate of change of elastic modulus (Δ G) at a temperature of 0-40 ℃_0℃-40℃) From-9 to-25 MPa/DEG C, measured according to ASTM 1640-99.

5. The medical tube as claimed in claim 1, wherein the hydrogenated styrene block copolymer has an elongation of 500-1000%.

6. The medical tube of claim 1, wherein the hydrogenated styrenic block copolymer has a total poly (mono alkenyl arene) content of 50 to 70 weight percent.

7. The medical tube according to claim 1, having an apparent kink diameter of 30-40mm, wherein the inner and outer diameter of the tube is 5 and 7mm, respectively.

8. The medical tube according to claim 1, having an apparent kink diameter of 20-30mm, wherein the inner and outer diameter of the tube is 3 and 4mm, respectively.

9. The medical tube as claimed in claim 1, wherein the ratio of the apparent kink diameter to the inner diameter of the tube is 6-10, or 4-8, or 15-30.

10. The medical tube of claim 1 having a haze of less than 3% as measured using astm d 1003.

11. The medical tube of claim 1, further comprising up to 50 wt% of a polyolefin.

12. The medical tube as claimed in claim 11, which has a ratio I (14)/I (15) of diffraction peak intensity [ I (14) ] at a scattering angle (2 θ) of 14 ° to diffraction peak intensity [ I (15) ] at a scattering angle (2 θ) of 15 ° in wide-angle X-ray diffraction of 1.4 or more.

13. The medical tube as claimed in claim 1, which has a viscosity coefficient of 0.45-0.65, measured at 25 ℃ and 50% relative humidity.

14. The medical tube of claim 1, having a peel force of 15-100N to separate a solvent-submerged medical tube from a plastic connector, wherein the plastic connector comprises a polyolefin, polyester, polycarbonate, polyvinyl chloride, polyetherketone, ABS, polystyrene, polyamide, polyimide, polyoxymethylene, polyacrylate, polyurethane, or polysulfone.

15. A medical tube consisting essentially of the formula A-B-A, (A-B-A)_nX、(A-B)_nX or a mixture thereof, wherein n is an integer from 2 to 30 and X is the residue of a coupling agent;

wherein, prior to hydrogenation, each A block is a monoalkenyl arene homopolymer block having a true peak molecular weight of 5 to 15kg/mol, each B block has a true peak molecular weight of 30 to 200kg/mol and is a controlled distribution copolymer block of at least one conjugated diene and at least one monoalkenyl arene, the styrene block copolymer having X has a coupling efficiency of 30 to 95%, and a mid-block monoalkenyl arene block index of 3 to 15%, wherein the monoalkenyl arene block index is the proportion of monoalkenyl arene units in a block B having two ortho-monoalkenyl arenes in the polymer chain; and

after hydrogenation, 0-10% of the aromatic double bonds are reduced and at least 90% of the conjugated diene double bonds are reduced;

wherein the hydrogenated styrenic block copolymer has a midblock poly (mono alkenyl arene) content of 35 to 50 weight percent based on the total weight of the midblock; and

the hydrogenated styrenic block copolymer has: a melt flow ratio of 1.0 to 10.0, as determined according to ASTM D-1238 at 230 ℃ and under a load of 2.16 kg; a Shore A hardness of 60-80, as determined according to ASTM D-2240; a DMA peak tan delta temperature at 1Hz of 0 to 40 ℃ as determined according to ASTM D-4065; and an order-disorder transition temperature of 200 ℃ to 300 ℃.

Technical Field

The present invention relates to medical tubing and compositions and methods for making the same.

Background

Hydrogenated styrene block copolymers have been widely used as an alternative material to vulcanized rubbers or vinyl chloride monomer-based resins for the production of various molded articles, including medical articles. The polyolefin-based resin is compounded with the hydrogenated styrene block copolymer to provide a polymer composition which is also used as a more effective substitute for the vinyl chloride monomer-based resin in applications such as food contact, household appliances and medical tubes. Medical tube applications, where the tube is in direct contact with blood, have strict regulatory limits as they must be tested by extractable and leachable substances according to pharmacopoeial protocols.

There is a continuing need for higher quality medical tubing and polymer compositions thereof that not only address the above-mentioned disadvantages, but also have other desirable characteristics, such as good transparency, flexibility and mechanical properties.

Summary of The Invention

In one aspect, the invention relates to medical tubing comprising the formula A-B-A, (A-B-A)_nX、(A-B)_nX or a mixture thereof, wherein n is an integer from 2 to 30 and X is the residue of a coupling agent for the styrenic block copolymer having X. Prior to hydrogenation, each A block is a monoalkenyl arene homopolymer block with a true peak molecular weight of 5-15kg/mol, and each B block has a true peak molecular weight of 30-200 kg/mol. The B block is a controlled distribution copolymer block of at least one conjugated diene and at least one mono alkenyl arene. The coupling efficiency of the styrene block copolymer with X is 30-95%. A mid block monoalkenyl arene block index of 3 to 15 percent, where the monoalkenyl arene block index is the proportion of monoalkenyl arene units in a block B having two vicinal monoalkenyl arenes in the polymer chain. After hydrogenation, 0 to 10% of the arene double bonds are reduced, at least 90% of the conjugated diene double bonds are reduced, and the midblock poly (mono alkenyl arene) content of the hydrogenated styrenic block copolymer is 35 to 70 weight percent based on the total weight of the midblock. The hydrogenated styrenic block copolymer has a melt flow ratio of 1.0 to 10.0, as determined according to ASTM D-1238 at 230 ℃ under a load of 2.16 kg; a Shore A hardness of 60-80, as determined according to ASTM D-2240; a DMA peak tan delta temperature at 1Hz of from 0 to 40 ℃ as determined according to ASTM D-4065; and the order-disorder transition temperature is 200-300 ℃.

Another aspect of the present invention is directed to medical tubing consisting essentially of the hydrogenated styrenic block copolymer described above.

Yet another aspect of the present invention is directed to a medical tube consisting essentially of the formula A-B-A, (A-B-A)_nX、(A-B)_nX or mixtures thereof, wherein n is an integer from 2 to 30 and X is for benzene having XA residue of a coupling agent of an ethylene block copolymer. Prior to hydrogenation, each A block is a styrene homopolymer block with a true peak molecular weight of 5-15kg/mol, and each B block has a true peak molecular weight of 30-50 kg/mol. The B block is a controlled distribution copolymer block of styrene and at least one conjugated diene selected from 1, 3-butadiene, isoprene and mixtures thereof. The coupling efficiency of the styrene block copolymer with X is 80-95%. A mid block monoalkenyl arene block index of 3 to 15 percent, where the monoalkenyl arene block index is the proportion of monoalkenyl arene units in a block B having two vicinal monoalkenyl arenes in the polymer chain. After hydrogenation, 0 to 10% of the arene double bonds are reduced, at least 90% of the conjugated diene double bonds are reduced, and the hydrogenated styrenic block copolymer has a midblock poly (mono alkenyl arene) content of 35 to 50 weight percent, based on the total weight of the midblock. The hydrogenated styrenic block copolymer has a melt flow ratio of 1.0 to 10.0, as determined according to ASTM D-1238 at 230 ℃ under a load of 2.16 kg; a Shore A hardness of 60-80, as determined according to ASTM D-2240; a DMA peak tan delta temperature at 1Hz of from 0 to 40 ℃ as determined according to ASTM D-4065; and the order-disorder transition temperature is 200-300 ℃.

The following terms are used in the specification and have the following meanings:

the "apparent kink diameter" is the diameter of the semicircular portion of the flexible tube when it is bent to the point where the tube begins to kink.

"midblock styrene blockiness" refers to the proportion of styrene units in the midblock of a polymer having two styrene units as the nearest ortho positions on the polymer chain. The styrene blockiness can be determined by 1H NMR spectroscopy using the method described in U.S. patent No. 7244785B2.

"controlled distribution" refers to a molecular structure having the following attributes: (1) terminal regions adjacent to monoalkenyl arene homopolymer ("a") blocks that are rich in (i.e., have greater than an average amount of) conjugated diene units; (2) one or more regions not adjacent to a chain a blocks that are rich in (i.e., have greater than an average amount of) mono alkenyl arene units; and (3) a monolithic structure with a lower blockiness. The term "enriched" is defined as greater than the average amount, preferably greater than 5% of the average amount.

By "polyolefin-free" is meant that no polyolefin is intentionally added. In one embodiment, the term means that less than 0.5 wt% of polyolefin is present.

The present invention provides a medical tube comprising a hydrogenated styrenic block copolymer that has high clarity, good kink resistance, and a suitable combination of other physical properties. In another embodiment, the present invention provides a medical tube consisting essentially of a styrenic block copolymer, e.g., without the addition of a polyolefin. Hydrogenated SBC can be used to make medical tubing.

Hydrogenated Styrene Block Copolymer (SBC) component: hydrogenated SBC has the structure ABA, (ABA)_nX、(AB)_nX or a mixture thereof, wherein n is an integer from 2 to 30 and X is the residue of a coupling agent for the styrenic block copolymer having X. The A blocks are monoalkenyl arene homopolymer blocks with a true peak molecular weight preferably ranging from 5 to 15kg/mol prior to hydrogenation; each B block is a controlled distribution copolymer block of at least one conjugated diene and at least one mono alkenyl arene and has a true peak molecular weight of 30 to 200 kg/mol. Further, the mid-block mono alkenyl arene block index is preferably 5 to 10%. After hydrogenation, the hydrogenated SBC has a midblock poly (monoalkenylarene) content of 35 to 50% by weight of the total midblock. In some embodiments, the coupling efficiency is 30-95%.

In some embodiments, the true peak molecular weight of the A block is from 5 to 15 kg/mol. In some embodiments, the true peak molecular weight of the B block is from 30 to 200kg/mol, or from 30 to 150kg/mol, or from 80 to 150 kg/mol. In one embodiment, the midblock monoalkenyl arene block index is from 3 to 15%. In other embodiments, the hydrogenated SBC has a midblock poly (monoalkenylarene) content of 35 to 65 weight percent, 40 to 65 weight percent, or 40 to 60 weight percent. In some embodiments, the SBC has a midblock vinyl content of 30 to 90 mol%, 50 to 70 mol%, or 30 to 40 mol%, or 35 to 40 mol%, prior to hydrogenation. In some embodiments, the total molecular weight of the hydrogenated SBC is from 60 to 200kg/mol, or from 80 to 120 kg/mol. In other embodiments, the total poly (mono alkenyl arene) content of the total block copolymer after hydrogenation is from 40 to 80 weight percent, or from 50 to 70 weight percent, or from 60 to 70 weight percent.

Hydrogenated SBCs can be prepared by methods known in the art. It is generally prepared by contacting the monomer or monomers with an organic alkali metal compound in a suitable solvent at a temperature of from-150 ℃ to 300 ℃, preferably from 0 ℃ to 100 ℃. The hydrogenation of the pendant vinyl groups and the intra-chain double bonds present in the block copolymer chain is carried out under conditions such that at least 90 mol%, at least 95 mol% or at least 98 mol% of the vinyl groups are reduced and 0 to 10 mol% of the aromatic double bonds are reduced. Suitable catalysts based on nickel, cobalt or titanium are used in the hydrogenation step.

Suitable monoalkenyl arene compounds suitable for use in preparing the a and B blocks include those having from 8 to 20 carbon atoms and include styrene, o-methylstyrene, p-tert-butylstyrene, 2, 4-dimethylstyrene, α -methylstyrene, vinylnaphthalene, vinyltoluene and vinylxylene, or mixtures thereof.

Suitable conjugated dienes include those having from 4 to 8 carbon atoms, such as 1, 3-butadiene, isoprene, 2, 3-dimethyl-1, 3-butadiene, 1, 3-pentadiene and 1, 3-hexadiene. Mixtures of such dienes may also be used. In one embodiment, the conjugated diene is 1, 3-butadiene. In another embodiment, the conjugated diene is a mixture of 1, 3-butadiene and isoprene.

Optional Components: the polymer composition with the hydrogenated SBC may be prepared by further including one or more optional additives such as: a tackifier resin, an inorganic filler, a lubricant, an oil, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an antioxidant, a colorant, an antistatic agent, a flame retardant, a water repellent agent, a hydrophilicity imparting agent, an electrical conductivity imparting agent, a thermal conductivity imparting agent, an electromagnetic wave shielding property imparting agent, a translucency adjusting agent, a fluorescent agent, a slip property imparting agent, a transparency imparting agent, an anti-blocking agent, a metal deactivator, and an antibacterial agent, as long as they do not adversely affect the intended use. In one embodiment, the polymer composition may further comprise a diagnostic agent,such as a color changing or chromogenic additive, which can serve as a visual indicator of the physical integrity of an article made from the composition.

In one embodiment, the polymer composition may be used as is without blending with another polymer, such as a polyolefin. For example, the polypropylene may be blended in small amounts, in one embodiment up to 0.5 wt%, in another embodiment up to 5 wt%, and in yet another embodiment up to 10 wt%. In another embodiment, the polymer composition may be blended with one or more other polymers, such as polyolefins, polyorganosiloxanes, polyesters, polyvinyl chlorides, polycarbonates, polyestercarbonates, polyvinylidene fluorides, and the like. Examples of polyolefins include polyethylene, polypropylene and polybutylene. In some embodiments, the polymer composition may be blended with up to 50 wt%, or up to 40 wt%, or up to 30 wt%, or up to 20 wt% of a polyolefin. In one embodiment, the polyolefin is polypropylene.

Performance of hydrogenated SBC' s: in some embodiments, the hydrogenated SBC has a melt flow ratio of 1.0 to 10.0, 2.0 to 8.0, 4.0 to 8.0, or 4.0 to 6.0 when determined according to ASTM D-1238 at 230 ℃ and 2.16kg load.

In some embodiments, the hydrogenated SBC has a shore a hardness of 60 to 80, or 60 to 70, or 70 to 80, as determined according to ASTM D-2240.

In some embodiments, the hydrogenated SBC has a DMA peak tan delta temperature of from 10 to 40 ℃, or from 10 to 20 ℃, or from 20 to 30 ℃, or from 30 to 40 ℃ as determined according to ASTM D-4065.

In some embodiments, the hydrogenated SBC has an order-disorder temperature (ODT) of 200-.

In some embodiments, the hydrogenated SBC has a tensile strength of 10 to 30MPa, or 10 to 20MPa, or 7.5 to 15.0 MPa.

Hydrogenated SBCs have a relatively stable hardness over a wide range of application temperatures. In some embodiments, the hydrogenated SBC has a rate of change of elastic modulus (Δ G), as determined in accordance with ASTM 1640-99, over a temperature range of 0-40 ℃₀℃_-40DEG C) of9 to-25 MPa/deg.C, or-12 to-22 MPa/deg.C, or-15 to-20 MPa/deg.C. In another embodiment, the polymer composition has a rate of change of elastic modulus (Δ G) in the range of 20 to 40 ℃₂₀℃_-40DEG C) from-9 to-25 MPa/DEG C.

In some embodiments, the hydrogenated SBC has an elongation of 500-.

Hydrogenated SBCs may have a combination of two or more properties falling within the various ranges described above. In some embodiments, the hydrogenated SBC has a melt flow ratio of 1.0 to 10.0, as determined according to ASTM D-1238 at 230 ℃ and 2.16kg load; a Shore A hardness of 60-80, as determined according to ASTM D-2240; a DMA peak tan delta temperature at 1Hz of from 10 to 40 ℃ as determined according to ASTM D-4065; and the order-disorder transition temperature is 200-300 ℃. In another embodiment, the polymer composition has a melt flow ratio of 4.0 to 8.0, a Shore A hardness of 70 to 80, a DMA peak tan delta temperature at 1Hz of 15 to 30 ℃, and an order-disorder transition temperature of 200 ℃ to 250 ℃.

Use of a composition: the various physical properties described above make hydrogenated SBCs valuable for making various articles, such as medical tubing, having high clarity and other desirable properties. In addition to medical tubing, hydrogenated SBCs can be used to make a variety of other articles, particularly articles used in the medical field. Thus, it can be used for producing multi-lumen tubes, multi-layer tubes, etc. Medical tubing may also be part of other products used in the medical field such as IV bags and catheters, such as those used for infusion, blood transfusion, peritoneal dialysis, and catheter interventions, such as intravascular catheters and balloon catheters. Other medical articles include blood bags, synthetic vascular prostheses, vascular circuits, syringes, hemodialyzers, blood cell separators, extracorporeal membrane oxygenation, dressing materials, and medical devices in contact with bodily fluids, particularly blood.

The composition for manufacturing the article can be prepared by mixing the components as described above using a device such as a henschel mixer, a V-type mixer, a ribbon mixer, a single-screw or twin-screw extruder, a kneader, or the like. The resulting resin composition may be pelletized. The tube may be prepared by methods known in the art. For example, the resin composition is fed into an extruder, melted and forced through a die to form a tube shape, and cooled with water or air. There is no particular limitation on the size, shape or cross-sectional dimension of the pipe prepared from the resin composition. In some embodiments, the tube has an outer diameter of 1 to 60mm or 1 to 20mm or 1 to 10 mm. The inner diameter of the tube is 1-50mm or 1-25mm or 1-10 mm. In some embodiments, the tube has a thickness of 0.1 to 20mm or 0.5 to 10mm or 1 to 5 mm.

Medical tube applications: in some embodiments, medical tubes made from the mixture exhibit an X-ray diffraction pattern with a peak intensity at a scattering angle (2 θ) of 14 [ I (14) ]]Intensity of diffraction Peak at Scattering Angle (2 θ) of 15 [ I (15) ]]Is 1.4 or more. The I (14)/I (15) ratio gives a measure of the amount of crystalline polypropylene present in the medical tube.

In some embodiments, medical tubes prepared using hydrogenated SBC exhibit low surface tack. The tackiness of the polymer surface is due to the nature of the polymer composition. When the outer surfaces of the medical tube contact each other, the viscosity thereof decreases due to the lower surface viscosity. This makes the use of such tubes easier. Surface tack can be determined by the "tack coefficient" according to the procedure described in Express Polymer letters, Vol 5, No.11(2011), 1009-1016. In some embodiments, the medical tube has a viscosity coefficient of 0.45 to 0.65, as measured at 25 ℃ and 50% relative humidity.

In some embodiments, medical tubing made therefrom has kink resistance, i.e., it can be bent significantly without kinking. Kink performance is measured as the "apparent kink diameter". In some embodiments, medical tubing having an inner diameter and an outer diameter of 5mm and 7mm, respectively, has an apparent kink diameter of 30-40 mm. In another embodiment, the apparent kink diameter of the medical tube, with an inner diameter and an outer diameter of 3mm and 4mm respectively, is 20-30 mm. In yet another embodiment, the medical tube has a ratio of apparent kink diameter to tube inner diameter of 6 to 10, 7 to 9, 8 to 9, or 9 to 10. In yet another embodiment, the medical tube has a ratio of apparent kink diameter to tube outer diameter of 4 to 8, 5 to 7, 6 to 7, 7 to 8, or 9 to 10. In another embodiment, the medical tube has a ratio of apparent kink diameter to tube wall thickness of 15 to 30, 15 to 20, 20 to 25, or 25 to 30.

Medical tubing has good optical clarity, which makes it easy to see fluid level and fluid flow. In one embodiment, the medical tube has a haze of less than 5%, less than 4%, or less than 3% as determined using ASTM D1003. Due to the high transparency of the tube, blurring or clouding of the tube wall due to polymer degradation can be visually detected.

Medical tubing made with hydrogenated SBC can also be firmly bonded to other plastic materials using a range of solvents. In medical applications, plastic connectors are made from a variety of materials, such as polyolefins, polyesters, polycarbonates, polyvinyl chloride, polyether ketones, ABS, polystyrene, polyamides, polyimides, polyoxymethylene, polyacrylates, polyurethanes, or polysulfones. The connector is bonded to the medical tube using a solvent bond of solvents such as tetrahydrofuran, cyclohexanone, methyl ethyl ketone, and the like. If the medical tubing is not bonded to the connector as strongly, the connection may loosen, resulting in fluid leakage. The bond strength of the bond is determined by determining the peel strength of the medical tube from the connector. In some embodiments, medical tubing made from the hydrogenated SBC described above requires a peel force of 15-100N or at least 30N or at least 50N or at least 75N or less than 125N to separate the solvent-submerged medical tubing from the plastic connector.

The medical tube has a low tendency to spring back when coiled or bent. This feature makes it easier to store a roll of medical tubing.

Examples

The following illustrative examples are non-limiting.

Polymer molecular weight was determined by Gel Permeation Chromatography (GPC) according to ASTM 5296-11, using polystyrene calibration standards. Polymer samples were dissolved in THF and run on the appropriate column set using RI and UV detectors. The molecular weight values obtained were then converted to true molecular weights using the GPC conversion factor for total polystyrene content. The coupling efficiency was determined by GPC from the peak integral ratio of the styrene-diene diblock phase relative to the peak of the higher molecular weight coupling.

Proton NMR methods were used to determine total polystyrene content (PSC), vinyl content, and styrene block index. The styrene block index was determined using the method described in U.S. Pat. No. 7244785B2.

The glass transition temperature (Tg) of all polymer samples was determined by dynamic mechanical analysis using TA Instruments DMA Q800. Temperature sweep experiments were conducted at-80 ℃ to 120 ℃ where the storage modulus (G '), loss modulus (G') and loss factor (tan. delta.) were obtained as a function of temperature. All experiments were performed at a frequency of 1 Hz. The glass transition temperature is reported as the temperature at the peak of tan δ.

Testing to determine ODT (order-disorder transition) rheology was performed on a Bohlin rheometer from Malvern Instruments. Temperature sweep experiments were performed at two frequencies of 0.005Hz and 0.2Hz, where the complex viscosity was determined. ODT is reported as the temperature at which the composite viscosity of the polymer is the same at both frequencies.

The tubes were tested for kink resistance using the Instron method. The tube was initially bent and placed between two jaws spaced 100mm apart. The tube is then bent by downward movement of the crosshead. The distance (xmm) between the crossheads was measured when the tube was kinked. The apparent kink diameter is then given by (100-x) mm.

Mechanical properties were determined according to the tensile test method of ASTM D412 using a miniature D-die dog bone sample. The tests were carried out on an Instron 3366 equipped with a 1kN load cell. The gauge length of the sample was 25.4mm and the test was performed at a tensile rate of 254 mm/min.

The shore a hardness of all samples was determined using an automatic hardness tester. Three sheets of the same formulation having a thickness of 2mm were stacked and the hardness was measured at the four corners and the center. The hardness was recorded 10 seconds after the durometer tip was in contact with the material. The reported values are the average of five measured hardness values.