China
Africa
Explore chapters and articles related to this topic
st Century
Published in Tatiana G. Volova, Yuri S. Vinnik, Ekaterina I. Shishatskaya, Nadejda M. Markelova, Gennady E. Zaikov, Natural-Based Polymers for Biomedical Applications, 2017
Tatiana G. Volova, Yuri S. Vinnik, Ekaterina I. Shishatskaya, Nadejda M. Markelova, Gennady E. Zaikov
Polyethylene (PE) [–СН2–СН2]n is a hydrophobic and bio-inert material. The low yield strength of polyethylene limits its applications. There are three commercial types of PE: low density, high density, and ultra high molecular weight PE. Low-density polyethylene (LDPE) is a wide-spread material, exhibiting high biological inertness, with a molecular weight of 50–200 Da. High density polyethylene (HDPE) is a more crystalline material. Porous HDPE produced by Porex Surgical, Inc. (U.S.) under the trademark MEDPOR® is used to manufacture implants. LDPE and HDPE are readily moldable. Ultra high molecular weight polyethylene (UHMWPE) has a molecular weight over 106 Da; it is non-moldable and has to be sintered prior to processing; then the material is processed mechanically to get a desired shape. UHMWPE is a partially crystalline polymer with a degree of crystallinity of 45–60%. Because of its high molecular weight, this PE has enhanced mechanical properties, which are in many respects better than those of LDPE. The tensile strength of UHMWPE is 30–44 MPa and its hardness reaches 4 MPa, while LDPE is characterized by values that are 2.0–2.5 times lower. The wear rate of UHMWPE amounts to 18 min/mm3. UHMWPE is produced under different trademarks (Hostalen GUR, Hercules Н, RCH-WOO, Hifax-1900, Spectra 900, Hylamer M, etc.). UHMWPE is used as a basis for constructing composite materials with enhanced mechanical properties. These materials are used to fabricate vascular grafts, to regenerate bone tissue, and as fixing systems.
Antifriction Nanocomposites Based on the Chemically Modified Ultra-High Molecular Weight Polyethylene
Published in Frank Abdi, Mohit Garg, Characterization of Nanocomposites, 2017
Lyudmila A. Kornienko, Sergey V. Panin
Ultra-high molecular weight polyethylene (UHMWPE) is of special importance among the family of polymeric materials owing to its high corrosion and chemical resistance [9, 10], and also biocompatibility, which open opportunities for application of this polymer in medicine and, first of all, in endoprosthesis (implants) manufacturing. The basic problem in the development of UHMWPE based on antifriction composites is its low adhesion to nanofillers because of the absence of polar groups. Finding ways to increase adhesion between the UHMWPE and nanofillers is an actual problem [4, 5, 6, 7, 8, 9, 10, 11]. In the present work an attempt has been made to enhance adhesion between UHMWPE and nanofillers by means of chemical modification of the polymer by adding UHMWPE grafted with maleic anhydride (SMA) and high-density polythene (HDPE) grafted with (SMA) and a more complex multipolar component— vinyltrimethoxysilane (VTMS, C5H12O3Si), for the design of antifriction nanocomposites. Grafted copolymers with functional groups are effective compatibilizers to increase interphase adhesion [12]. The mechanism of compatibilizer action consists in the following: the grafted copolymers based on UHMWPE and HDPE have thermodynamic affinity with filled nonpolar polymer of the same type and can be well combined with it.
Hard Tissue Replacements
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Sang-Hyun Park, Adolfo Llinás, and Vijay K. Goel
e prosthesis for total hip replacement consists of a femoral component and an acetabular component (Figure 37.8a and b). e femoral stem is divided into head, neck, and sha. e femoral stem is made of Ti alloy or Co-Cr alloy (316L stainless steel was used earlier) and is xed into a reamed medullary canal by cementation or press-tting. Femoral head is made of Co-Cr alloy, alumina, or zirconia. Although Ti alloy heads function well under clean articulating conditions, they have fallen into disuse because of their low wear resistance to third bodies, for example, bone or cement particles. Acetabular component is generally made of ultra-high-molecular-weight polyethylene (UHMWPE).
Magnetorheological finishing of UHMWPE acetabular cup surface and its performance analysis
Published in Materials and Manufacturing Processes, 2020
Kunal Arora, Anant Kumar Singh
Ultra-high molecular weight polyethylene (UHMWPE) is the most commonly used polymer for joint replacement prosthesis in the modern medical implant industry.[1] The surface finishing has significant importance in these components. For example, in hip-joint implants, fine finishing of acetabular cup leads to thedecrease in the coefficient of friction due to which there is proper relative motion can be performed amid the acetabular cup surface and the femoral head.[4] This further tends to decrease the osteolysis and increases the life span of hip-joint implants. Similarly, in knee and spine implantation, a fine finish UHMWPE is essential for the proper functioning of implants. Hence, UHMWPE is used as the workpiece in the present experimentation. In the present work, the UHMWPE hemispherical cups are manufactured with the diameter of the 22 mm as depicted in Fig. 1(a). Initially, a turning operation is done on the UHMWPE rod for making samples as per the dimension required. Further, traditional grinding is done on workpiece samples to eliminate the uneven marks from the hemispherical cup surface. After that workpieces are cleaned using the acetone and maintained properly before the magnetorheological (MR) fluid-based finishing. Further, a fixture of length 50 mm is made to hold the workpiece sample on the table as depicted in Fig. 1(b).
Medical textiles
Published in Textile Progress, 2020
Ultra-High Molecular Weight Polyethylene (UHMWPE) is a type of polyethylene in which the degree of polymerisation is extremely high, yielding long polymer chains of molecular weight between two and six million Daltons. UHMWPE is used as a bearing surface in joint arthroplasty. In this form, it is a semicrystalline with the polymer exhibiting a degree of crystallisation of around 50%, hence the human body temperature is:Above the UHMWPE’s glass transition temperature (quoted figures vary, from as low as -160 °C to -80 °C compared with the values for PE at -110 to -120 °C [160], but it is the figure of -80 °C for UHMWPE that makes more sense as it is expected to be higher than for PE because of restricted freedom of movement owing to fewer polymer chain ends) [161] andBelow the polymer’s melting point (132.7 °C) [162, 163]and it therefore exhibits both the rigidity expected in solids and some mobility in the non-crystalline chain segments yielding other attributes more characteristic of a liquid. Crosslinked, it is used in the liners of joint replacements as it has better wear characteristics than polyethylene [164] and also it has been shown to perform excellently well when incorporated together with polycaprolactone in a partially-absorbable suture for tendon and ligament repair [165].
Influence of Five-Year Degradation on Mechanical and Tribology Properties of Ultra-High-Molecular-Weight Polyethylene
Published in Tribology Transactions, 2018
Xueqin Kang, Chi Yao, Chunmin Yang, Peizhong Feng
Ultra-high-molecular-weight polyethylene (UHMWPE) is a distinctive polymer with the highest wear resistance, good biocompatibility, low friction, improved chemical inertness, and high impact resistance compared to any other polymers (Ge, et al. (1)). It has been used as a bearing material in total joint replacement for over 50 years (Kurtz, et al. (2)); however, the in vivo wear debris of UHMWPE materials after implantation has been proven to induce osteolysis and eventual loosening, which is one reason for long-term failure of total hip joints composed of UHMWPE, including acetabulums and hard femoral balls (Pokorny, et al. (3); Ingham and Fisher (4)). Mechanical property changes and chemical decomposition are involved in the degradation process (Kang, et al. (5)). Chemical decomposition is the most important parameter and can induce damage with regard to mechanical properties (Kurtz (6)). Oxidation is the most powerful factor in UHMWPE chemical decomposition, because the wear and delamination of UHMWPE are mainly caused by oxidation (Willie, et al. (7); Bracco, et al. (8)). The mechanical performance of UHMWPE in vitro has been studied extensively, but the change in mechanical properties in vitro, especially wear resistance, is not clearly understood (Kang, et al. (5)), because previous studies only studied the effect of long-term shelf aging on the oxidation index (Kurtz, et al. (9)) and the effect of aging on the oxidation and wear of UHMWPE in distilled water at high pressure (Fouad (10); Wannomae, et al. (11)). The environment in shelf aging or real-time aging is very different from that in a physiological environment.