Modification of Epoxides with Metallic Fillers-Mechanical Properties after Ageing in Aqueous Environments.

The aim of this research was a comparative analysis of selected mechanical properties of epoxy compounds that were modified with metallic fillers and aged in aqueous environments. The tested epoxy compounds consisted of three components: styrene modified epoxy resin based on Bisphenol A, triethylenetetramine curing agent (resin/curing agent ratio of 100:10) and two types of metallic fillers in the form of particles: aluminum alloy (EN AW-2024-AlCu4Mg1) and tin-phosphor bronze (CuSn10P). Samples were subjected to ageing in 4 water environments: low-, medium- and high-mineralized natural water and in a sugar-containing solution for 1, 2 and 3 months. The epoxy samples were subjected to compressive strength tests in accordance with the ISO 604:2002 standard. It was observed that, among others, the compositions seasoned in low-mineralized water usually achieved the highest average compressive strength. As for filler type, using the bronze filler (CuSn10P) usually achieved the highest average compressive strength results.

Adhesive Joint Degradation Due to Hardener-to-Epoxy Ratio Inaccuracy under Varying Curing and Thermal Operating Conditions.

This paper presents the results of an experimental study of adhesive joint strength with consideration of the inaccuracy of the hardener dosage, in the context of evaluating the degradation of joints when used either at ambient or elevated temperatures. The butt joint strength characteristics were assessed for two types of adhesives-rigid and flexible-and two curing scenarios-with and without heat curing. An excess hardener was shown to be significantly more unfavourable than its deficiency, which can ultimately be considered as a recommendation for forming epoxy adhesive joint assemblies. In order to fully understand the relationship between the analysed mechanical properties of the material and the influence of component ratio excesses and heating, a process of fitting basic mathematical models to the obtained experimental data was also performed.

Analysis of the Effect of Component Ratio Imbalances on Selected Mechanical Properties of Seasoned, Medium Viscosity Bone Cements.

The paper presents the results of experimental strength tests of specimens made of two commercially available bone cements subjected to compression, that is a typical variant of load of this material during use in the human body, after it has been used for implantation of prostheses or supplementation of bone defects. One of the factors analysed in detail was the duration of cement seasoning in Ringer's solution that simulates the aggressive environment of the human body and material degradation caused by it. The study also focused on the parameters of quantitative deviation from the recommended proportions of liquid (MMA monomer, accelerator and stabiliser) and powder (PMMA prepolymer and initiator) components, i.e., unintentional inaccuracy of component proportioning at the stage of cement mass preparation. Statistical analysis has shown the influence of these factors on the decrease in compressive strength of the cements studied, which may be of significant importance in operational practice.

Evaluation of the Effect of Selected Physiological Fluid Contaminants on the Mechanical Properties of Selected Medium-Viscosity PMMA Bone Cements.

Revision surgeries several years after the implantation of the prosthesis are unfavorable from the patient's point of view as they expose him to additional discomfort, to risk of complications and are expensive. One of the factors responsible for the aseptic loosening of the prosthesis is the gradual degradation of the cement material as a result of working under considerable loads, in an aggressive environment of the human body. Contaminants present in the surgical field may significantly affect the durability of the bone cement and, consequently, of the entire bone-cement-prosthesis system. The paper presents the results of an analysis of selected mechanical properties of two medium-viscosity bone cements DePuy CMW3 Gentamicin and Heraeus Palamed, for the samples contaminated with saline and blood in the range of 1-10%. The results obtained for compressive strength and modulus of elasticity were subjected to statistical analysis, which estimated the nature of changes in these parameters depending on the amount and type of contamination and their statistical significance.

Application of an Artificial Neural Network in the Modelling of Heat Curing Effects on the Strength of Adhesive Joints at Elevated Temperature with Imprecise Adhesive Mix Ratios.

This paper is a discussion of the results of tests intended to (i) estimate the effects of component mix ratios and heat curing of an adhesive joint on the tensile strength, and (ii) to determine the adhesive component mix ratio for which heat curing is insignificant to the strength of adhesive butt joints. Experimental tests were carried out at ambient temperature and elevated temperature during which adhesive butt joints were loaded with a tensile force until failure. The variables were the mix ratio of epoxy adhesive components and the application of heat holding at the adhesive curing stage. An LSTM (long short-time memory) forecast was used to determine the point corresponding to the mix ratio of adhesive components at which heat holding of the adhesive joint no longer has a positive and significant importance to the final tensile strength of the joint.

The Impact of Contaminating Poly (Methyl Methacrylate) (PMMA) Bone Cements on Their Compressive Strength.

This study presents an analysis of the impact of doping bone cement with saline. The two-ingredient cement, made right before the surgery, is subject to various kinds of organic contaminants and liquids used in the operating area, such as saline used to cleanse or cool it, during the process of mounting the prosthesis or bone-filling procedures. The processes of experimental destructive testing and statistical analysis have shown that, depending on the degree of saline doping, the static compressive strength parameters may greatly improve (with a low degree of contamination) or significantly worsen (when the contamination degree is higher). The limit value of the degree of salt admixture was estimated (2%), with which no statistically significant differences were observed in the cement strength in relation to the strength of non-contaminated cement.

Use of Deep Learning Networks and Statistical Modeling to Predict Changes in Mechanical Parameters of Contaminated Bone Cements.

The purpose of the study was to test the usefulness of deep learning artificial neural networks and statistical modeling in predicting the strength of bone cements with defects. The defects are related to the introduction of admixtures, such as blood or saline, as contaminants into the cement at the preparation stage. Due to the wide range of applications of deep learning, among others in speech recognition, bioinformation processing, and medication design, the extent was checked to which it is possible to obtain information related to the prediction of the compressive strength of bone cements. Development and improvement of deep learning network (DLN) algorithms and statistical modeling in the analysis of changes in the mechanical parameters of the tested materials will enable determining an acceptable margin of error during surgery or cement preparation in relation to the expected strength of the material used to fill bone cavities. The use of the abovementioned computer methods may, therefore, play a significant role in the initial qualitative assessment of the effects of procedures and, thus, mitigation of errors resulting in failure to maintain the required mechanical parameters and patient dissatisfaction.

Effect of Physiological Saline Solution Contamination on Selected Mechanical Properties of Seasoned Acrylic Bone Cements of Medium and High Viscosity.

Bone cements play a key role in present-day surgery, including the implantation of hip and knee joint endoprostheses. The correct and durable bonding of the prosthesis to the bone is affected by both the static strength characteristics determined in accordance with ISO 5833:2002 and the resistance to long-term exposure to an aggressive environment of the human body and the impurities that may be introduced into the cement during implementation. The study attempts to demonstrate statistically significant degradation of cement as a result of the seasoning of cement samples in Ringer's solution with simultaneous contamination of the material with saline solution, which is usually present in the surgical field (e.g., during the fixing of endoprostheses). The results of statistical analysis showed the nature of changes in compressive strength and microhardness due to seasoning time and degree of contamination.

Effect of Physiological Fluids Contamination on Selected Mechanical Properties of Acrylate Bone Cement.

This study analyses the degradation rate of selected mechanical properties of bone cement contaminated with human blood and saline solution. During the polymerisation stage, the PMMA cement specimens were supplemented with the selected physiological fluids in a range of concentrations from 0% to 10%. The samples were then subjected to the standardised compression tests, as per ISO 5833: 2002, and hardness tests. The obtained results were analysed statistically to display the difference in the degradation of the material relative to the degree of contamination. Subsequently, numerical modelling was employed to determine the mathematical relationship between the degree of contamination and the material strength degradation rate. The introduction of various concentrations of contaminants into the cement mass resulted in a statistically significant change in their compressive strength. It was shown that the addition of more than 4% of saline and more than 6% of blood (by weight) causes that the specimens exhibit lower strength than the minimum critical value of 70 MPa, specified in the abovementioned International Standard. It was further revealed that the cement hardness characteristics degraded accordingly. The mathematical models showed a very good fit with the results from the experiments: The coefficient of determination R2 was 0.987 in the case of the linear hardness model for blood and 0.983 for salt solution; secondly, the values of R2 for the third-degree polynomial model of compressive strength were 0.88 for blood and 0.92 for salt. From the results, it can be seen that there is a quantitative/qualitative relationship between the contamination rate and the drop in the tested mechanical characteristics. Therefore, great effort must be taken to minimise the contact of the bone cement with physiological fluids, which naturally occur in the operative field, particularly when the material cures, in order to prevent the cement material strength declining below the minimum threshold specified in the ISO standard.

Seasoning Polymethyl Methacrylate (PMMA) Bone Cements with Incorrect Mix Ratio.

Cemented joint prostheses are widely used in orthopaedic surgery; however, implants/bone bonds are known to be susceptible to aseptic loosening, particularly in the case of long-term performance. The exact mechanism of this failure is under constant examination. One of the critical factors to the final mechanical functionality of bone cement can be an incorrect mix ratio of a two-component material (powdered polymer and liquid monomer). It can result in the deterioration of the final mechanical strength properties. The paper presents the results from an experimental study on the effects of the deviation from the correct mix ratio on the moisture uptake and the compression strength of cement depending on the seasoning time in Ringer's solution. The results were subjected to statistical analysis and a mathematical model was developed.