UHMWPE/SBA-15 nanocomposites synthesized by in situ polymerization

Different nanocomposites have been attained by in situ polymerization based on ultra-high molecular weight polyethylene (UHMWPE) and mesoporous SBA-15, this silica being used for immobilization of the FI catalyst bis [N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentafluoroanilinato] titanium (IV) dichloride and as filler as well. Two distinct approaches have been selected for supporting the FI catalyst on the SBA-15 prior polymerization. A study on polymerization activity of this catalyst has been performed under homogenous conditions and upon heterogenization. A study of the effect of presence of mesoporous particles and of the immobilization method is also carried out. Moreover, the thermal characterization, phase transitions and mechanical response of some pristine UHMWPEs and UHMWPE/SBA-15 materials have been carried out. Relationships with variations on molar mass, impregnation method of catalyst and final SBA-15 content have been established

The inlfuence of blood preparations on tribological properties of the UHMWPE/STOP CoCrMo alloy couple

An introduction of a new material for long-term implants, especially for endoprostheses, should be preceded with comprehensive research, including tribological tests. The in vitro operational tests of materials used for endoprostheses, which cannot be skipped, should be performed in conditions reflecting, as far as possible, those present in the implanted joint. This will allow a quite accurate description of the behaviour of the biomaterial tested in the aspect of its long-term life cycle in a living organism. So far, there has been no standard lubricating agent that should be used in this type of tests. The above problems are seldom discussed in the professional literature. The authors of this paper intend to present the influence of lubricating agents, including the animal and human blood plasma and the human blood serum, on the tribological characteristics of the polymer-metal friction couple. The results of the experiments made have revealed a different course of tribological characteristics of blood preparations compared to those of distilled water as well as changes in the values of the friction coefficient and wear intensity at various loads and sliding speeds. Human blood-based products are characterised with a larger spread and lower explicitness of results than other lubricating agents. It is disadvantageous in the case of applying a pure form of these products for tribological tests. The analyses carried out show imperfections of blood derivative preparations but, at the same time, they dictate the direction of searching for a liquid to be used in long-term tribological in-vitro tests

Deformation of new-generation polymers intended for medical implants in the light of a compression test

A comparison is made of plastic, elastic and total deformation of new grades of GUR 1020 and 1050 polymers used in medical implants. Polyethylene 1050 has been found to have higher resistance to permanent deformation and better elastic properties. It has been shown that radiation modification increases the resistance of the both grades of UHMWPE to plastic deformation

The application of microindentation for an assessment of radiation modification of UHMWPE from the aspect of reducing the effects of plastic deformation of polymer elements of endoprostheses

The paper includes an assessment of the effectiveness of radiation modification, through microindentation, of GUR 1020 and 1050 polyethylene used for elements of endoprostheses. The micromechanical characteristics obtained have shown that irradiation with electrons enhances the resistance to plastic deformation of the polymer types investigated and may lead to a significant increase in operational durability of endoprosthesis elements

Diagnozowanie metodą mikroindentacji i sklerometrii zmian właściwości po napromieniowaniu strumieniem elektronów polietylenu GUR 1050

W celu podwyższenia odporności polietylenu GUR 1050 na odkształcenie plastyczne i zużycie ścierne zastosowano modyfikację radiacyjną. Badania w zakresie naprężeń do 300 MPa wykazały wzrost odporności na deformację trwałą. Potwierdzono to testami mikroindentacyjnymi i sklerometrycznymi. Scratch test wykazał, że w całym zakresie odkształceń eksploatacyjnych występuje mniejsza skłonność do wykruszania materiału wyżłobionego niż do jego plastycznego wypiętrzania. Dominacja mikromechanizmu bruzdowania pozwala zachować niewielki spadek odporności na zużycie. Parametry mikrotestów mogą być wykorzystywane do diagnozowania i selekcji polimerów stosowanych w medycznych oraz technicznych węzłach tarcia

The influence of modification by deformation and electron irradiation on the enhancement of functional properties of GUR1020 and GUR1050 biopolymers

GUR1020 and GUR1050 polyethylenes, intended for the production of endoprosthesis cups, were subjected to forming by uniaxial compression (up to the value of plastic deformation ef = 0.2), and radiation cross-linking (by means of an electron beam). A slight orientation of the lamellar phase in the structure as well as strengthening – through the induced state of stresses – of morphological effects of radiation modification, and no texturing effect of the crystalline phase had been assumed for the applied sequence of polymer forming interactions (while maintaining a small deformation value ef). The aim of the applied method was a significant reduction in tribological wear of polymers, both the starting materials and ones modified exclusively by electron irradiation. An increase in hardness and elasticity modulus along with a radiation dose was found for both materials and the compared methods of forming. It was demonstrated that changes occur with varying intensity depending on the type of polymers, which are characterised by an almost two-fold difference between their molecular weight. The results of tribological tests showed an 11-fold increase of wear resistance (linear; tester T-01), compared to the unmodified material. Only a 2.5 to3 fold reduction in wear was found compared to the material subjected to electron irradiation

Evaluation of electron beam irradiation effectiveness in view of increasing wear resistance of GUR 1020 and GUR 1050 polyethylenes used for endoprosthesis cups

Radiation modification was conducted in order to increase the resistance of GUR 1020 and GUR 1050 polyethylenes to plastic deformation and abrasive wear. Electron irradiation of 26-156 kGy dose was applied. It was determined that the hardness and longitudinal elasticity module increase along with the increase in the dose of radiation. It was also found that GUR 1050 (of a molecular weight of 9.2•106 g / mol) is characterised by a 1.86 times greater resistance to permanent deformation. This indicates a close relationship between the properties of polymers and molecular weight, which for the GUR 1020 is 5•106 g/mol. This is corroborated by a lower value of tribological wear of GUR 1050 compared to GUR 1020, which already exceeds 20% in the initial state of polymers. Tribological tests conducted on the T-05 and T-01 testers have shown that electron irradiation (6×26 kGy) of both polymers result in a four-fold reduction in wear as compared to unmodified polyethylenes. The obtained results demonstrate the effectiveness of radiation modification, which promises the possibility of extending the service life of endoprosthesis cups

The influence of e-beam radiation on plastic deformation, mechanical properties and wear of the polyethylene GUR 1050 for acetabular cups

The resistance of polyethylene to wear and permanent deformation influences the durability of polymer-metal kinematic systems. The recently introduced polyethylene, GUR 1050, of a molecular weight of 9.2 * 106 g/mole is intended especially for medical implants. This justifies the need for evaluating the resistance of this material to wear and deformation and for determining if its functional properties can be improved by radiation modification. Samples of the initial (base) polymer were electron-irradiated with applying an irradiation multiplication factor I = 1–6 and a dose of 26 kGy. An analysis of changes in the deformation value under the influence of operational loads has shown an increase in the polyethylene resistance to permanent deformation as a result of the irradiation applied. The improvement of mechanical properties has been confirmed in micro-indentation tests. An increase in the hardness and Young's modulus was identified. This effect has been preserved despite an opposite trend that causes a growing level of plastic deformation of the polymer under the influence of load. Tribological tests have shown a significant increase (by ca. 4 times) in the resistance to abrasive wear of the polyethylene modified through irradiation. The significant wear reduction prognosticates a longer life of the friction couple, which will prolong the durability of acetabular cups in the human organism. The test results presented in the paper prove the effectiveness of modification through irradiation that enhances the tested functional properties proportionally to the applied dose of electron irradiation

The influence of radiation and thermal modification on the functional properties of GUR 1050 polyethylene

This paper presents a method of improving the operational durability of UHMWPE, while ensuring high oxidation resistance of the polymer. The initial material, GUR 1050 (Poly Hi Solidur Medi TECH), underwent a sequential process consisting of a stage of modification through radiation, and a stage of thermal processing. The assessment of the effectiveness of the applied method was performed using micromechanical examination and tribological tests using a T-01 (polymer/Vitalium alloy) tester. It was found that there was a slight decrease in the micromechanical characteristics (hardness and Young's modulus) for the variants subjected to the sequential modification process compared to the variants only irradiated. However, the tribological test results show an increase in resistance to wear compared to unmodified material, and unchanged resistance to wear compared to the irradiated polymer

The EPR method investigation of free radicals in polymer UHMWPE applied in the biomedical knots of the friction

In this paper, the results of EPR measuring of free radicals for two types of polyethylene of ultra high molecular weight: GUR 1020 and GUR 1050 are presented. Samples were irradiated by electron beam energy of 10 MeV and dose 26 kGy a number of times (i = 1, 2, 3, 4, or 6). With the increase of radiation, the amount of free radicals increases as well. In both cases of polyethylene GUR 1020 and GUR 1050, the effect of saturation at the maximum dose of radiation equal 156 kGy was not observed. This proves that both types of material show similar radiation resistance