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This study investigated the production of phosphate glass fiber/polylactic acid (PGF/PLA) commingled yarns, textiles and composites for biomedical applications. The PGF volume contents of the composites investigated were 25% and 40%. Plain weave textiles with yarn counts of 10 warp/cm and 6 weft/cm were produced using a commercial weaving machine. An orthogonal array design (OAD) was employed as a statistical method to investigate the effects of compression molding parameters (processing temperature, preheating time, compression time, and pressure) on flexural strength and porosity of PGF/PLA textile composites. Processing temperature showed the most significant effect in achieving maximum laminate flexural strength and molecular weight of PLA. Processing models were developed using regression techniques to predict the laminate flexural strength and the molecular weight of PLA. Composites with fiber contents of 25 and 40 vol% produced using optimized processing conditions identified by the processing models, provided flexural strengths of 236 MPa and 293 MPa, respectively., (© 2020 Wiley Periodicals LLC.)

This work presents manufacturing, processing and characterisation of the phosphate glass fibre (PGF) products for biomedical applications, including multifilament PGF strands, yarns and textiles, and PGF textile composites. The multifilament production of PGF strands was achieved using a 50-nozzle bushing. PGF yarns, with a linear density of 87 tex, a twist angle of 14° and a tensile strength of 0.29 N/tex, were produced by combining 8 fibre strands using the ring-spinning method. PGF textiles, with a width of 15 mm and a thickness of 0.36 mm, were prepared using an inkle loom. The maximum flexural strength and modulus of unidirectional (UD) composites with a fibre volume fraction of ~17% were 262 ± 11 MPa and 10.4 ± 0.2 GPa, respectively. PGF textile composites with a fibre volume fraction of ~21% exhibited mechanical properties of 176 ± 13 MPa for flexural strength and 8.6 ± 0.6 GPa for flexural modulus. Despite the UD and textile composites having almost an equivalent amount of fibres in the 0 direction, the crimp of the yarns was found to contribute to the significantly lower flexural properties of the textile composites in comparison with the unidirectional (UD) composites. Additionally, the processing conditions such as processing temperature and time were found to have a strong effect on the mechanical properties of the resultant composite products. The number-average molecular weight of PLA was also found to reduce by 13% and 19% after the production of PLA films and PLA plates, respectively, in comparison with the as-received PLA pellets., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Fibre reinforced composites have recently received much attention as potential bone fracture fixation applications. Bioresorbable composites based on poly lactic acid (PLA) and phosphate based glass fibre were investigated according to ion release, degradation, biocompatibility and mechanical retention profiles. The phosphate based glass fibres used in this study had the composition of 40P2O5-24MgO-16CaO-16Na2O-4Fe2O3 in mol% (P40). The degradation and ion release profiles for the composites showed similar trends with the amount of sodium and orthophosphate ions released being greater than the other cations and anions investigated. This was attributed to low Dietzal's field strength for the Na(+) in comparison with Mg(2+) and Ca(2+) and breakdown of longer chain polyphosphates into orthophosphate ions. P40 composites exhibited good biocompatibility to human mesenchymal stem cells (MSCs), which was suggested to be due to the low degradation rate of P40 fibres. After 63 days immersion in PBS at 37 °C, the P40 composite rods lost ~1.1% of mass. The wet flexural, shear and compressive strengths for P40 UD rods were ~70%, ~80% and ~50% of their initial dry values after 3 days of degradation, whereas the flexural modulus, shear and compressive strengths were ~70%, ~80%, and ~65% respectively. Subsequently, the mechanical properties remained stable for the duration of the study at 63 days. The initial decrease in mechanical properties was attributed to a combination of the plasticisation effect of water and degradation of the fibre-matrix interface, with the subsequent linear behaviour being attributed to the chemical durability of P40 fibres. P40 composite rods showed low degradation and ion release rates, good biocompatibility and maintained mechanical properties similar to cortical bone for the duration of the study. Therefore, P40 composite rods have huge potential as resorbable intramedullary nails or rods., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Use of bioresorbable screws could eliminate disadvantages associated with metals such as removal operations, corrosion, MRI interference and stress shielding. Mechanical properties of bioresorbable polymers alone are insufficient for load bearing applications application as screws. Thus, reinforcement is necessary to try and match or surpass the mechanical properties of cortical bone. Phosphate based glass fibres were used to reinforce polylactic acid (PLA) in order to produce unidirectionally aligned (UD) and unidirectionally plus randomly distributed (UD/RM) composite screws (P40 UD and P40 UD/RM). The maximum flexural and push-out properties for the composite screws (P40 UD and P40 UD/RM) increased by almost 100% in comparison with the PLA screws. While the pull-out strength and stiffness of the headless composite screws were ∼80% (strength) and ∼130% (stiffness) higher than for PLA, those with heads exhibited properties lower than those for PLA alone as a result of failure at the heads. An increase in the maximum shear load and stiffness for the composite screws (∼30% and ∼40%) in comparison to the PLA screws was also seen. Maximum torque for the PLA screws was ∼1000 mN m, while that for the composite screws were slightly lower. The SEM micrographs for P40 UD and P40 UD/RM screws revealed small gaps around the fibres, which were suggested to be due to buckling of the UD fibres during the manufacturing process., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Internal fixation for bone fractures with rigid metallic plates, screws and pins is a proven operative technique. However, refracture's have been observed after rigid internal fixation with metal plates and plate fixation has been known to cause localised osteopenia under and near the plate. In the present study, resorbable composites comprising a PLA matrix reinforced with iron doped phosphate glass fibres were investigated. Non-woven random mat laminates of approximately 30% and 45% fibre volume fraction (V(f)) were produced, along with unidirectional and 0°-90° samples of approximately 20% V(f). The non-woven composite laminates achieved maximum values of 10 GPa modulus and 120 MPa strength. The 0-90º samples showed unexpectedly low strengths close to matrix value (~50 MPa) although with a modulus of 7 GPa. The UD specimens exhibited values of 130 MPa and 11.5 GPa for strength and modulus respectively. All the modulus values observed were close to that expected from the rule of mixtures. Samples immersed in deionised water at 37°C revealed rapid mechanical property loss, more so for the UD and 0-90º samples. It was suggested that continuous fibres wicked the degradation media into the composite plates which sped up the deterioration of the fibre-matrix interface. The effect was less pronounced in the non-woven random mat laminates due to the discontinuous arrangement of fibres within the composite, making it less prone to wicking. Random mat composites revealed a higher mass loss than the UD and 0°-90° specimens, it was suggested this was due to the higher fibre volume fractions of these composites and SEM studies revealed voidage around the fibres by day 3. Studies of pH of the degradation media showed similar profiles for all the composites investigated. An initial decrease in pH was attributed to the release of phosphate ions into solution followed by a gradual return back to neutral.

Details of the microscopic structure of phosphate glasses destined for biomedical applications, which include sodium, magnesium and calcium cations, have been obtained from the static structure factor measured by means of neutron scattering. A complementary, molecular dynamics study has been performed on a range of phosphate glasses using density functional theory methods, which allow structural fluctuations, including bond breaking, in the liquid phase before quenching to the glass phase. Good agreement between experiment and simulation allows the molecular dynamics trajectories to be analysed in detail. In particular, attention is focused on the cross-linking of divalent cations in contrast with the structural aspects associated with monovalent cations. Magnesium cations are found equidistant and bridging between the phosphorus atoms of different phosphate chains, leading to a shorter phosphorus-phosphorus second neighbour distance (that is, a more compact packing of neighbouring phosphate chains) compared to the effect of sodium cations. Calcium cations show behaviour intermediate between those of magnesium and sodium. Molecular dynamics simulations give access to the cation mobility, which is lowest for magnesium, reflecting its structural, cross-linking role.

Phosphate-based glasses (PGs) and their composites are of interest as bone repair and tissue engineering scaffolds due to the totally degradable nature of the materials. This study has investigated the effect of Si and Fe on the properties of PG particulate-filled polycaprolactone (PCL) matrix composites. Two glass compositions were investigated (mol.%): 50P(2)O(5), 40CaO and 10SiO(2) or Fe(2)O(3) (Si(10) and Fe(10), respectively). All composites contained 40 vol.% particulate filler, either Si(10), Fe(10), or a blend (40Si(10)/0Fe(10), 30Si(10)/10Fe(10), 20Si(10)/20Fe(10), 10Si(10)/30Fe(10) or 0Si(10)/40Fe(10)). Ion release, weight loss and composite mechanical properties were characterised as a function of time in deionised water (DW) and phosphate-buffered saline (PBS), respectively. The potential for calcium phosphate deposition was assessed in simulated body fluid (SBF). Calcium and phosphate ion release in DW increased in tandem with the rate of composite weight loss, which increased with Si(10) content. A Si(10) content dependent rate of pH reduction was observed in DW. After 56 days the PG in the 40Si(10)/0Fe(10) composite was completely dissolved, whereas 67% of that in the 0Si(10)/40Fe(10) composite remained. The initial flexural strength of 40Si(10)/0Fe(10) composites was significantly lower when compared with the other materials. An increase in Si(10) content led to an increase in Young's modulus and a concomitant decrease in flexural strain. It was found that the PCL molecular weight (M(w)) decreased dramatically with increasing Si(10) content. FTIR analysis showed that Si incorporation into PG led to reaction with the PCL ester bonds, resulting in a reduction in PCL M(w) when processed at elevated temperatures. Changes in mechanical properties with time in PBS were glass blend dependent and a more rapid rate of reduction was observed in higher Si(10) content composites. After 28 days in SBF surface deposited brushite was formed in 20Si(10)/20Fe(10) PG containing composites. Thus, the properties of PCL-PG composites could be tailored by controlling the phosphate glass blend composition., (Copyright 2010 Acta Materialia Inc. All rights reserved.)

Polymers prepared from polylactic acid (PLA) have found a multitude of uses as medical devices. The main advantage of having a material that degrades is so that an implant would not necessitate a second surgical event for removal. In addition, the biodegradation may offer other advantages. In this study, fibers produced from a quaternary phosphate-based glass (PBG) in the system 50P(2)O(5)-40CaO-5Na(2)O-5Fe(2)O(3) (nontreated and heat-treated) were used to reinforce the biodegradable polymer, PLA. Fiber properties were investigated, along with the mechanical and degradation properties and cytocompatibility of the composites produced. Retention of mechanical properties overtime was also evaluated. The mean fiber strength for the phosphate glass fibers was 456 MPa with a modulus value of 51.5 GPa. Weibull analysis revealed a shape and scale parameter value of 3.37 and 508, respectively. The flexural strength of the composites matched that for cortical bone; however, the modulus values were lower than those required for cortical bone. After 6 weeks of degradation in deionized water, 50% of the strength values obtained was maintained. The composite degradation properties revealed a 14% mass loss for the nontreated and a 10% mass loss for the heat-treated fiber composites. It was also seen that by heat-treating the fibers, chemical and physical degradation occurred much slower. The pH profiles also revealed that nontreated fibers degraded quicker, thus correlating well with the degradation profiles. The in vitro cell culture experiments revealed both PLA (alone) and the heat-treated fiber composites maintained higher cell viability as compared to the nontreated fiber composites. This was attributed to the slower degradation release profiles of the heat-treated composites as compared to the nontreated fiber composites. SEM analyses revealed a porous structure after degradation, and it is clear that there are possibilities here to tailor the distribution of porosity within polymer matrices.

The degradation profiles of six sodium iron phosphate glass formulations have been investigated using simple dissolution trials in deionized water. The glasses were produced from the appropriate phosphate salts by melting at 1200 degrees C in 5% Au/95% Pt crucibles. Dissolution rates varied from 0.2 gcm(-2)h(-1) for the 1% Fe glass to essentially zero over the 6-week test period for the 15% Fe and 20% Fe glasses. The overall degradation rate was found to vary according to the approximate relation: rate = 1.3e(-0.79x) gcm(-2)h(-1), where x is the percentage iron content of the glass. Glasses with 10% or greater iron content were observed to maintain a constant density over the course of the tests and thus appeared to degrade from the surface and not the bulk. In vitro cell response tests were conducted on the glasses using macrophages and primary craniofacial osteoblasts. These tests were performed on the glasses with 10% or greater iron content because glasses with lower iron content degraded too quickly. Confocal microscopy revealed a rounded macrophage morphology and IL-1beta production was low, suggesting little macrophage activation. However, a significant level of peroxide production was observed. Osteoblasts were observed to attach to the glass surfaces and spread, exhibiting a similar cytosketetal organization to the cells on the Thermanox controls, with a high level of F-actin organization. On balance, the 15% Fe glass performed slightly better than the 20% Fe glass in these assays., ((c) 2004 Wiley Periodicals, Inc.)

Changes in the thermal properties of sodium phosphate glasses during melt production have been investigated using Pt/Au and fused alumina crucibles. Glasses were produced from NaH(2)PO(4) as a starting material, providing an intrinsic Na(2)O:P(2)O(5) ratio of 1:1 and giving an O/P = 3, that is, a metaphosphate. In Pt/Au crucibles, glass transition temperatures rose to a plateau value of 295 degrees C at a rate determined by melt temperature. No contamination of the glass by platinum or gold was detected or indicated in the results. E(a) for the reaction was found to be 66.4 kJ mol(-1). In fused alumina crucibles, glass transition temperatures rose to over 450 degrees C, with these values showing some convergence at higher furnace temperatures. Extensive erosion of the alumina crucibles was observed. The amount of alumina incorporation within the glasses correlated well with the rise in glass transition temperature up to a maximum of 15.5 mol % Al(2)O(3) content. Al(2)O(3) incorporation above this value caused a reduction in the value of the T(g).

This paper investigates the use of novel phosphate-glass fibre-reinforced rods as resorbable intramedullary nails. Random and unidirectional fibres were moulded into composite rods by forging at ~100 °C. Rods produced using non-woven random mats (RM) showed little improvement in mechanical strength over the unreinforced polylactic acid (PLA) rods. This was suggested to be due to the breakdown of the fibres during the manufacturing process; the length of the fibres decreased from 10-mm (initial) to ~1.2 mm. Modulus and stiffness values for P50 RM rods were higher than those for the PLA rods which could be due to the orientation of the fibres during the rod manufacture process. Rods produced using long fibres parallel to the length of the rod displayed superior mechanical properties, not only against the PLA rods but also cortical bone. Maximum flexural, shear and compressive strengths were 242, 87 and 400 MPa, respectively. A flexural modulus of 25 GPa was achieved, with shear and compressive stiffness values of 6 and 21.5 kN mm, respectively. These unidirectionally reinforced phosphate glass fibre PLA composites have huge potential to be used as IM fixation devices. [ABSTRACT FROM AUTHOR]

Phosphate glass fiber of the composition 20Na2O-24MgO-16CaO-40P2O5 was produced using an in-house fiber drawing rig. The interfacial properties of the phosphate glass fiber/poly(caprolactone) (PCL) system were measured using the single fiber fragmentation test (SFFT). The system was calibrated using E-glass fibers and polypropylene system. This gave an interfacial shear strength (IFSS) of 4.1 MPa, which agrees well with other published data. The IFSS for the unsized (as drawn) phosphate glass fiber/PCL system was found to be 1.75 MPa. Fibers treated with 3-aminopropyl-triethoxy silane (APS) showed an IFSS of 3.82 MPa. X-ray photoelectron spectroscopic (XPS) analysis of unsized and silane sized fibers established the presence of silane on the fiber surface. Degradation tests of the silane treated fiber/PCL samples were carried out in deionised water at 37°C and it was found that the IFSS values decreased over time. Four others silanes were also investigated but APS gave the highest IFSS values. [ABSTRACT FROM AUTHOR]

Poly(caprolactone) matrix iron phosphate glass fiber-reinforced (16Na2O-24MgO-16CaO-4Fe2O3-40P2O5) composites (10% fiber by weight) were fabricated by compression molding. Tensile strength, tensile modulus, elongation at break (%), bending strength, bending modulus and impact strength of the composites were found to be 72 MPa, 2.74 GPa, 11%, 86 MPa, 3.22 GPa and 16 kJ/m2, respectively. Degradation tests of the fibers and composites were performed in aqueous medium at 37°C. Mechanical properties of the composites retained almost 90% of their original properties after 6 months of aqueous degradation. Interfacial shear strength (IFSS) of the composite was also measured by using the single-fiber fragmentation test. The IFSS of the composite system was found to be 4.01 MPa. [ABSTRACT FROM AUTHOR]

Melt-spun phosphate glass fibres (40 mol% P2O5-20 mol% Na2O-16 mol% CaO-24 mol% MgO) were aged for up to 7 days in doubly distilled water at 37 °C prior to single-fibre tensile testing. The effects of aqueous aging on the evolution of strength and modulus are discussed along with the possibilities for mitigating property loss via surface treatment and annealing. Whilst as-drawn fibres exhibited a strength loss over time, annealing produced a significant increase in strength over the same period. Silane pre-treatment of as-drawn fibres yielded no significant benefit to strength. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare a range of phosphate-based glasses containing a fixed amount of (50 mol%) P2O5 and varying amounts of CaO and Na2O, made using two different sets of precursors in order to investigate any potential differences in their properties. Thermal analysis, XRD, dissolution, EDX, density, H-NMR and ion release studies were conducted in order to compare the data obtained from both groups. Thermal analyses revealed no differences in the glass transition temperatures obtained between the two groups, and similar crystalline phases were identified for each composition from both groups via XRD analysis. However, statistically significant differences were seen between the dissolution rates and density values obtained. The density values increased linearly with increasing CaO content, whilst the degradation rates decreased with increasing CaO content and spanned over four orders of magnitude. A decrease in the release of both cations and anions with increasing CaO content was also observed, with rates also ranging over four orders of magnitude. From the compositions investigated, the largest amounts of ions released were those of the Na+ and Ca2+ ions and the P3O3-9 anion, with higher total anion release observed from glasses prepared from one set of precursors than the other. EDX analysis confirmed the composition of the glass formulations produced and no H+ ions were detected from 1H-NMR analyses conducted, suggesting that no H+ was present in the glass produced. [ABSTRACT FROM AUTHOR]