Polymer composition for biomedical application

 

(57) Abstract:

Described polymer compound for biomedical application containing thermoplastic polymer is a polyamide or propylene, biocompatible powder filler - hydroxyapatite and carbon fiber filler, and as a modifier use polyacrylic acid and polyvinylpyrrolidone in the following ratio, wt.h.: thermoplastic polymer 85-45, hydroxyapatite 10-35, carbon fibrous filler 5-35, polyacrylic acid of 0.002-0.2, polyvinylpyrrolidone 0,04-0,25. The material obtained from the composition has a strength 700-1200 MPa, a hardness of up to 120 MPa and regional contact angle from 16 to 40o. table 4.

The invention relates to the field of composite polymeric materials for biomedical application, containing, along with a polymeric binder and biocompatible filler - hydroxyapatite, such polymers like polyacrylic acid and polyvinylpyrrolidone, or more precisely to the polymer composite implants used as prostheses for hip replacement surgery.

The most effective offer materials may be used in the field of bone orthopedics and Chol operating technology - for the manufacture of biocompatible plates and cortical prostheses bearing skeletal bones, experiencing high mechanical loads.

Known composite material for surgical implants, obtained from a polymer composition consisting of a polymeric binder (polyethylene), filler - hydroxyapatite and oriented high modulus polyethylene fibers (Ward, Ian Macmillan; Ladizesky, Hugo Noe // Compacted biomaterials // pat. GB 96-800 960115).

Known also similar to the above composition (N. H. Ladizesky, E. M. Pirhonen, D. B. Appleyard, I. M. Ward, W. Bonfield // Fibre reinforcement of ceramic/polymer composites for a major load-bearing bone Substitute material. Composites Science and Technology 58 (1998), 419-434), consisting of layers of oriented continuous polyethylene fibers, hydroxyapatite and polyethylene.

The disadvantages of the known materials obtained from these compositions is that both material obtained by extrusion, as they may not be processed by casting under pressure, anisotropic materials and their physical and mechanical properties differ drastically in normal and Tangenziale direction relative to the fiber.

In addition, they have low hardness (about 20 MPa) and high wetting angle ( 50-70o), which is much >/P>Also known composite material for implants (Okuno Masaki, Shikinami transformer-coupled amplifier // Osteosynthetic material, composited implant and process for preparing the same. Pat. EP0795336, A4) obtained from the composition in which the binder used polyethylene, polypropylene, polylactic, and as fillers hydroxyapatite and bioactive glass. This material has a high biocompatibility and mechanical strength compared with the counterparts. However, this material has an insufficient level of interaction between polymer and filler (hydroxyapatite) in the intermediate layer (the interface). In this regard remain relatively low hardness (up to 4 kg/mm2) and bending strength (30 MPa).

Known composite material for surgical implants, selected as a prototype as the most similar in composition and purpose (S. Deb, M. Wang, K. E. Tanner, W. Bonfield // Hydroxyapatite-polyethylene composites: effect of grafting and surface treatment of hydroxyapatite. Journal of materials science: materials in medicine 7 (1996) 191-193).

The composition of the prototype consists of polyethylene, crosslinked with benzoyl peroxide in the amount of 70 C. H. and hydroxyapatite in the amount of 20-40 C. H. Advanced to increase strength it contains properties: liquid Smoot who passed from this composition, have the strength to 27 MPa and hardness to 30.0 MPa, wetting angle is 65-75o. Production samples of this composition is only possible method of compression molding. The disadvantages of this composition are: inability to obtain products more technological molding, high (65-75o) wetting angle, low hardness (30 MPa), which complicates the use of osteoprotegerin that require higher physical and mechanical properties and better wettability of the implant.

The objective of this invention to provide a polymeric composition for biomedical application, able to be cast for a structural material having biocompatibility, radiolucency, increased strength, hardness, allowing it to be used as a mounting fixture in the bone orthopedics, oral and maxillofacial surgery.

This object is achieved in that the polymer compound for biomedical application containing thermoplastic polymer, biocompatible powdered hydroxyapatite filler and modifier further comprises a carbon fibrous filler, as a thermoplastic is comfort polyacrylic acid and polyvinylpyrrolidone in the following ratio of components, wt.h.:

Thermoplastic polymer - 85-45

Hydroxyapatite - 10-35

Carbon fibrous filler - 5-35

Polyacrylic acid of 0.002 to 0.2

Polyvinylpyrrolidone - 0,04-0,25

The essence of the invention lies in the fact that the composition additionally contains carbon fibrous filler, as thermoplastic polymer used is a polymer selected from the group of polyamide, polypropylene, and as a modifier use polyacrylic acid and polyvinylpyrrolidone.

The proposed polymer composition can be recycled as injection molding methods, and other (pressing, extrusion) to obtain stable properties of the structural material.

The properties of the components that comprise the proposed material, widely known as they are used in various industries, including in medicine.

As a binder of thermoplastic investigated:

polyamide-12 (PA-12) (paleodynamic) [-HN(CH2)11CO-]nthe density of 1.02 g/cm3, toplvl.- 180o;

polyamide-11 (PA-11) (poly-decanamide) [-HN(CH2)10CO-]nthe density of 1.02 g/cm3, topplvl.- 160-176oC.

All of these polymers were investigated by doctors biocompatibility and, judging by the materials of the articles are offered as implants of various types. Advantage of all the proposed binder is large compared with polyethylene for strength and hardness, which is determined by the chemical structure of the polymers.

Fillers developed material is hydroxyapatite and carbon fiber. Hydroxyapatite is widely used as a biocompatible filler implants, including the composition of the prototype. In the developed material was used hydroxyapatite in the form of a powder size of about 1 μm with a ratio of CA/P = 1,67.

To provide a higher mechanical strength without compromising biocompatibility in the human body was used carbon fiber brands Chis and UVIS. Fibres obtained by a high-temperature treatment (1500oC) polyacrylonitrile volcano (Chis) and hydrocellulose fiber (UVIS). Along with these advantages fibers have high physical and mechanical properties. Carbon fiber "UVIS" - modulus of elasticity - 100-120 GPA, a density of 1.6 g/cm3the strength of 1000-1500 MPa, 4.9 to 5 μm; carbon>/P>Modifier - polyvinylpyrrolidone is widely known as a component of ready-made forms of drugs and other types of products used in the human body. Himself polyvinylpyrrolidone is a thermoplastic with a low (60o(C) melting point, soluble in water and is safe when injected into the human body.

Polyacrylic acid is widely used as a component in the creation of acrylic phosphate ceramics. As the polymer electrolyte poly (acrylic acid is used for a variety of applications for biomedical application. According to its chemical structure polyacrylic acid is a polymer with a glass transition temperature of 160oC. thermal stability of poly (acrylic acid) (destruction >250oC) allows its use in developed compositions, because the most high temperature processing when using as the binder is polyamide-11 and polyamide-12 is 210-240oC. Thus, the essence of the invention is to create a new type of biomedical polymer structural material, namely "polymer Apatite-modified carbon material from the polymeric binder used, as compared with the properties of the prototype (table. 4).

The figures obtained properties depend on the entire amount of components used (see table). Thus, such factors as the hardness and tensile strength in bending, in addition to the usual effect of polymer and fillers depends on the used modifiers. Lowering the value of the wetting angle along with the impact modifiers depends on the optimal content overadapting part. The introduction of two modifiers, namely, polyacrylic acid and polyvinylpyrrolidone, allows to achieve a significant reduction in wetting angle and simultaneously improve the physico-mechanical parameters (table. 1, examples 1-6).

The data suggests that all components of the developed material is widely used in biomedical engineering, including inside the human body that determines the validity of the proposals for its use as an implant.

A specific example of obtaining materials and products to determine properties is given below.

The components of the composition 10 g of hydroxyapatite powder, 2.5 g of carbon fibers Chis, 0.1 g of polyvinylpyrrolidone and 0.002 g of polyacrylic acid is mixed in a porcelain mortar with 37.4 g Gran 2 mm, temperature 230oWith a total load of 20 kg

The resulting extrudate is cut into pellets with a length of 2 mm To prepare experienced products (bars HH mm) granules are placed in the loading chamber of the mold for injection molding, heated to 230oC. Then the mold is cooled to a temperature of 215oTo give a pressure of 60 per MPa and continue cooling. The samples are tested for strength in bending (technology=98 MPa) impact strength (A=43 Kj/m2), hardness (Hin=98 MPa). On the wide edge of the sample determine the wetting angle of water (KUS=41o).

As can be seen from the tables, the resulting material is markedly superior to the prototype in terms of strength, different types of the materials developed is at the level of 700-1200 MPa, while that of the prototype 250-300 MPa. The prototype has a much lower value of hardness (about 25-32 MPa), while the different types of developed material, this figure reaches 120 MPa. The proposed material has better wetting: wetting angle varies in different types of material from 16 to 40o, while the prototype is much higher, reaching 50o< / BR>
reduction - increases KUS.

Thus, on a number of key operating indicators developed material is markedly superior to the prototype.

The combination of the proposed material of high physical and mechanical performance required for operation of structural materials (bending strength, hardness, toughness), with low wetting angle with water, contributing to the good biocompatibility of the material, ensures its successful use as implants in craniofacial surgery for restoration of various parts of the skeleton, as well as for use in mounting and biocompatible radiolucent parts (screws, bolts, nuts, gaskets, washers) used in the operating technique.

Polymer composition for biomedical application containing a thermoplastic polymer, a biocompatible powder filler - hydroxyapatite and modifier, characterized in that it further comprises a carbon fibrous filler, as thermoplastic polymer used is a polymer selected from the group of polyamide, polypropylene, and as a modifier use polyacrylic acid and polyvinylpyrrolidone BR>
Carbon fibrous filler is 5 - 35

Polyacrylic acid of 0.002 to 0.2

Polyvinylpyrrolidone - 0,04 - 0,25

 

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