Arteries tensile properties

The discovery of living cationic polymerization has provided methods and technology for the synthesis of useful block copolymers, especially those based on elastomeric polyisobutylene (Kennedy and Puskas, 2004). It is noteworthy that isobutylene can only be polymerized by a cationic mechanism. One of the most useful thermoplastic elastomers prepared by cationic polymerization is the polystyrene-f -polyisobutylene-(>-polystyrene (SIBS) triblock copolymer. This polymer imbibed with anti-inflammatory dmgs was one of the first polymers used to coat metal stents as a treatment for blocked arteries (Sipos et al., 2005). The SIBS polymers possess an oxidatively stable, elastomeric polyisobutylene center block and exhibit the critical enabling properties for this application including processing, vascular compatibility, and biostability (Faust, 2012). As illustrated below, SIBS polymers can be prepared by sequential monomer addition using a difunctional initiator with titanium tetrachloride in a mixed solvent (methylene chloride/methylcyclohexane) at low temperature (-70 to -90°C) in the presence of a proton trap (2,6-dt-f-butylpyridine). To prevent formation of coupled products formed by intermolecular alkylation, the polymerization is terminated prior to complete consumption of styrene. These SIBS polymers exhibit tensile properties essentially the same as those of... 

Table B6.16 presents typical data for the tensile properties of arterial tissues from Yamada [43]. The test specimens of tissues were strips each with a reduced middle region 10 mm length, 2-3 mm in width, and a length to width ratio of 3 1. In the tables ...

Table B6.16 Tensile Properties of Human Coronary Arterial Tissue (Longitudinal Direction)...

Table B6.16 lists the tensile data for human coronary arterial tissue in the longitudinal direction. Other arteries have similar properties [43]. Yamada [43] provides the tensile properties of animal tissues in various tables.

The tensile properties of human venous tissues are presented in Table B6.20. For the testing method and definitions of the terms in the table, please refer to Section B6.5 on Mechanical properties of arteries. 

The polymerization of p ra-dioxanone as well as that of methyl and dimethyl homologues were described by Doddi et al. [183]. Poly(ptira-dioxanone) is primarily used as the absorbable suture material PDS (manufactured by Ethicon Inc.) because of its good tensile properties with respect to PGA and its ability to form monofilaments [28]. PDS material has been investigated for arterial regeneration in rabbit [184] and for internal suspension and fixation of facial fractures clinically [185], for cerclage of the eyeball [186], for closure of abdominal wounds [187] and for orbital floor reconstruction [188] as well as for use in pediatric cardiovascular operations [189] and in orthopeadic surgery [190]. 

Several studies have shown that microbial cellulose can be molded into tubular form with diameter < 6 mm. Klemm et al. [101] prepared a microbial cellulose tube having 1 mm diameter and 5 mm length with a wall thickness of 0.7 mm. The tensile strength of the material was foxmd to be comparable to that of normal blood vessels (800 mN) and is employed as blood vessel to replace part of the carotid artery. Alter four weeks, the microbial cellulose/carotid artery complex was covered with connective tissue. The in-vivo bicompatibility tests show that microbial cellulose can be used as a replacement blood vessel. Recently, Brown et al [102] have prepared small tubes of microbial cellulose-fibrin composites treated with glutaraldehyde in order to crosslink the polymers and allow a better match of the mechanical properties with those of native small-diameter blood vessels. 

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