Advances in Primary and Revision Hip Arthroplasty
K. Mohan Iyer in Hip Joint in Adults: Advances and Developments, 2018
The polyethylene acetabular component forms part of the traditional bearing couple, that is, hard on soft, which articulates with a metal or ceramic head. A major factor influencing prosthetic survival is wear of the polyethylene with its debris, causing osteolysis and loosening of hip components. Advances in reducing the wear characteristics of polyethylene focused on three stages: manufacturing, sterilisation and shelf life. The types of polyethylene include high-density polyethylene (HDP), ultra-high-molecular-weight polyethylene (UHMWPE), highly cross-linked polyethylene (HCLPE) and vitamin E-doped polyethylene (E-Poly). The direct compression moulding technique has been identified as the preferred manufacturing process to achieve consistently lower wear rates. Inferior wear characteristics are achieved with other manufacturing techniques, such as ram bar extrusion with secondary machining, hot isostatic pressing into bars with secondary machining and compression moulding into bars with secondary machining. The calcium stearate component of the lubricant used to protect the processing equipment was recognised to produce unfused polyethylene particles, thus diminishing the mechanical properties of the final product. It was therefore avoided in the manufacturing process.
Orthopaedic operations
Ashley W. Blom, David Warwick, Michael R. Whitehouse in Apley and Solomon’s System of Orthopaedics and Trauma, 2017
Ultra-high molecular weight polyethylene (UHMWPE) is an inert thermoplastic polymer. Its density is close to that of the low-density polyethylenes but the very high molecular weight provides increased strength and wear resistance over other types of polyethylene. The material is most commonly used in orthopaedics for hip (acetabular cup) and knee (tibial tray) prostheses and is sterilized by gamma irradiation. The latter process was noted to cause oxidation of the material and detrimentally alter its physical and chemical properties to the extent that a ‘shelf life’ for the component was created. Consequently, current techniques of sterilization involve gamma irradiation in an oxygen-free, inert environment (e.g. in nitrogen). Although ethylene oxide sterilization is an alternative, irradiation of UHMWPE has the advantage of promoting cross-linking of the polymer, which also improves wear rates.
Elements of Polymer Science
E. Desmond Goddard, James V. Gruber in Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
In polymer analog modifications, a reaction takes place along the polymer chain to convert certain chemical functionalities into different functions, without altering the degree of polymerization of the starting polymer. This approach is particularly useful for the transformation of naturally occurring polymers, but it is applied also to modify synthetic polymers. For example, saturated polymers, such as polyethylene, can be chlorinated or oxidized. Polyenes, such as rubber, can be hydrogenated, halogenated, or epoxidized. Pendant groups, such as the ester groups in poly(vinyl acetate), can be hydrolyzed by transesterification with butanol or methanol to yield poly(vinyl alcohol). The latter can be modified further by reactions typical of alcohols, such as ether formation, esterification, or formation of acetal by treatment with butyraldehyde to form poly(vinyl butyral). The hydroxyl groups in polysaccharides are converted to corresponding ethers and esters. Cellulose ethers, for example, result from the reaction of cellulose with ethylene oxide or propylene oxide (see Chapter 8). Hydrophobically modified polymers such as the cationic cellulose ether derivative, Quatrisoft LM-200 (Amerchol), are obtained via polymer analog reactions (see later chapters).
Drip irrigation biofouling with treated wastewater: bacterial selection revealed by high-throughput sequencing
Published in Biofouling, 2019
Kévin Lequette, Nassim Ait-Mouheb, Nathalie Wéry
Drippers and irrigation pipes are made of polyethylene. Some microorganisms are able to colonise and alter polyethylene surfaces by modifying the functional groups on the surface, the surface topography or the hydrophobicity/hydrophilicity of the surface (Restrepo-Flórez et al. 2014). These changes can facilitate bacterial attachment to the surface and thus biofilm development on polyethylene surfaces. There are several types of polyethylene according to their density or degree of branching. For instance, Aeromonas and Nocardia were found in pipe and dripper biofilms whereas only the genus Pseudomonas was observed in dripper biofilms (Figure 5). These genera have polyethylene biodegradation abilities (Restrepo-Flórez et al. 2014). In the current study, no information was available concerning the material properties of the pipes and drippers. Nevertheless, this parameter might explain the presence of these bacterial genera in the pipe and dripper biofilms. An investigation of the effect of the material properties of polyethylene on the microbial communities would therefore improve present knowledge regarding biofouling processes in drip irrigation systems.
Removal of arsenic(III) from aqueous media using amine functionalized-grafted styrene/maleic anhydride low-density polyethylene films
Published in Toxin Reviews, 2022
A. F. G. Masud Reza, Tapos Kormoker, Abubakr M. Idris, Md. Shamsuzzoha, Md. Saiful Islam, Adel A. El-Zahhar, Md. Saiful Islam
On the other side, low-density polyethylene (LDPE), as the least expensive of all polymer packaging films, reported advantageous features when modified by some methods (Abdel Ghaffar et al.2014). Grafting of LDPE by chemical or radiation methods improved its chemical, thermal, and mechanical properties, which was exploited for various purposes including the removal of undesired components from water (Awadallah-F and Sobhy 2018). In particular, the modification by γ-ray irradiation addressed the benefits of ease of introducing functional groups, no production of detrimental residues with no need of copolymerization purification, cost-effectiveness, no need of catalysts and/or additives implementation, and no need of final product sterilization (Kim et al.2016, Oliani et al. 2013). Radiation modification is considered a friendly method allowing for modifying polymer surface with desired properties (Awadallah-F and Sobhy 2018).
Thermophysiological aspects of wearable robotics: Challenges and opportunities
Published in Temperature, 2023
While several simple routes can minimize the whole-body thermal exoskeleton impacts, minimizing local heating within the body interfaces is more challenging and may require more advanced solutions. To start with the most straightforward point that even some medieval knights got right, devices intended for outdoor use in, for example, agricultural [14,75] or construction [48] industries should have exterior surfaces that reflect short wave radiation. Instead of putting a white cloak over armor as knights [76], wearable robotics designers have a variety of novel coatings or even fabrics with engineered spectral properties to choose from. These materials reflect nearly all shortwave radiation but are either highly reflective, emissive, or even transparent to longwave radiation [77–79]. The infrared reflective materials are suited for extremely hot conditions like Phoenix in the summer, where the surrounding surfaces are much hotter than skin and thus provide a strong infrared heating source [80]. When the surrounding is not as hot, the highly infrared emissive materials can cool to sub-ambient temperatures by radiating to space through the atmospheric window [77]. Infrared transparent materials such as polyethylene textiles and thin films can help cool the body radiatively in moderate indoor or outdoor conditions. However, polyethylene becomes exponentially more absorbing with thickness, so it is not helpful as a construction material for body interface materials.
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