Degradation of composite materials composed of tricalcium phosphate and a new type of block polyester containing a poly(L-lactic acid) segment

Abstract

Degradation of a new type of poly(L-lactic acid)/poly(ethylene; hexamethylene/ sebacate) block polyester and its composite containing 10 and 30 wt% tricalcium phosphate (TCP) were studied in vitro. Film specimens of thickness 100 and 250 microm for each of the three materials were immersed in phosphate buffered saline (pH 7.4) at 37 degrees C for up to 24 weeks. At appropriate intervals, water absorption, dry and wet tensile strength, molecular weight, and thermal properties of the specimens were measured by weighing, tensile strength testing, size exclusion chromatography, and differential scanning calorimetry, respectively. The decrease in tensile strength was greater in the unblended and thicker polymer film than in the other five films. The retention of tensile strength after 24 weeks increased with increasing TCP content. This trend was also noticed in the retention of molecular weight. The tensile strength of the materials having molecular weights below 5 x 10(4)-6 x 10(4) Mw or 2 x 10(4)-3 x 10(4) Mn dropped substantially and the materials became fragile. Blending of TCP to the PLLA block polyester retarded degradation, suggesting that TCP neutralized the carboxyl end groups formed by hydrolysis of ester bonds.

In-situ polymerisation of fully bioresorbable polycaprolactone/phosphate glass fibre composites: In vitro degradation and mechanical properties

“…The flexural strength and modulus of all PCL/PGF composite specimens in this study exhibited an initial reduction after immersion in PBS for 1 day, which was suggested to be due to plasticisation of the fibre/matrix interface by the diffused PBS within the composite specimens [14,16,28]. The diffused PBS might also cause micro cracks and stress concentration sites on the fibre surfaces and led to the reduction in composites mechanical properties [2].…”

“…The most frequently used manufacturing technique adapted for bioresorbable polymer composites is laminate stacking (LS) and hot press moulding [13][14][15]. However, a number of studies have seen a rapid loss in mechanical properties of the composites manufactured by LS after immersion in aqueous environment [2,12,16,17].…”

Preparation of poly(ε-caprolactone)/continuous bioglass fibre composite using monomer transfer moulding for bone implant

“…This provides these polymers with a tremendous advantage over other new degradable polymers that have to undergo time and cost consuming biocompatibility assessments [3]. The reinforcing phase most often used are bioactive ceramics such as hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) [4], biocompatible phosphate glass [5], and bioactive glass in the system of Na 2 O-K 2 OCaO-MgO-P 2 O 5 -SiO 2 [6,7].…”

“…The poor bonding between polymeric matrix and reinforcements are related to the polymer composite processing methods and interfacial bonding properties. Currently used methods are conventional hot press moulding [4,10,11] and film stacking [12,13]. Due to high viscosity of the polymer melt, it is difficult to wet out the surface of the reinforcements or to impregnate the reinforcing preform.…”

The degradation properties of co-continuous calcium phosphate polyester composites: insights with synchrotron micro-computer tomography

“…The combination of polymers with calcium phosphate has been widely studied since this concept offers improved mechanical properties, while maintaining the favourable biocompatibility and osteoconductivity of calcium phosphates (Bonfield et al 1981;Suchanek & Yoshimura 1998). These composites often consist of a degradable polyester matrix to which calcium phosphate fibres or particles are added (Agrawal & Athanasiou 1997;Suchanek & Yoshimura 1998;Imai et al 1999;Heidemann et al 2001;Ignatius et al 2001;Ara et al 2002;Kikuchi et al 2002;Niemela et al 2004a;Niemela 2005). An additional effect of these composites is that, because of the addition of the calcium phosphates, the degradation is delayed (Heidemann et al 2001;Niemela et al 2004a,b) and the pH of the surrounding solution remains stable for longer periods (Agrawal & Athanasiou 1997;Heidemann et al 2001).…”