Multiscale modelling for the heterogeneous strength of biodegradable polyesters

Abstract

A heterogeneous method of coupled multiscale strength model is presented in this paper for calculating the strength of medical polyesters such as polylactide (PLA), polyglycolide (PGA) and their copolymers during degradation by bulk erosion. The macroscopic device is discretized into an array of mesoscopic cells. A polymer chain is assumed to stay in one cell. With the polymer chain scission, it is found that the molecular weight, chain recrystallization induced by polymer chain scissions, and the cavities formation due to polymer cell collapse play different roles in the composition of mechanical strength of the polymer. Therefore, three types of strength phases were proposed to display the heterogeneous strength structures and to represent different strength contribution to polymers, which are amorphous phase, crystallinity phase and strength vacancy phase, respectively. The strength of the amorphous phase is related to the molecular weight; strength of the crystallinity phase is related to molecular weight and degree of crystallization; and the strength vacancy phase has negligible strength. The vacancy strength phase includes not only the cells with cavity status but also those with an amorphous status, but a molecular weight value below a threshold molecular weight. This heterogeneous strength model is coupled with micro chain scission, chain recrystallization and a macro oligomer diffusion equation to form a multiscale strength model which can simulate the strength phase evolution, cells status evolution, molecular weight, degree of crystallinity, weight loss and device strength during degradation. Different example cases are used to verify this model. The results demonstrate a good fit to experimental data.

Experiment and modelling of the strain-rate-dependent response during in vitro degradation of PLA fibres

“…Recently, Zhang et al [32] proposed an interesting three-scale method (microscale, mesoscopic scale and macroscale) to predict strength of bioresorbable polyesters during hydrolytic degradation. The strength was related to molecular weight through a power law given by Eq.…”

“…Again, this is a semiempirical approach with parameters obtained from experiments. Curiously, the authors did not consider the stiffness degradation [30][31][32]. Table 1 shows the results from Weir et al as molecular weight, elastic modulus and tensile strength decrease with degradation; this evolution is well represented by exponential law as described in Eq.…”

Durability of Biodegradable Polymer Nanocomposites

“…Zhang et al [ 158 ] proposed a semiempirical approach for predicting the strength of biodegradable medical polyesters, namely, PLA and polyglycolide (PGA) and their copolymers, during hydrolytic degradation. Three different phases in the mesoscopic-scale (amorphous, crystalline and vacancy phases) were defined and further integrated into the multiscale heterogeneous strength model.…”

SILVER SULFATE (Ag2SO4): MOLECULAR ANALYSIS AND ION TRANSPORT

“…Sifat Kimia Kegunaan Sintesis (12) Kapasitas Pemisahan (18) Penyaringan (15) Kalor (107)(108)(109) Rumus kimia (110)(111)(112)(113)(114) Endapan Ikatan Pemanasan Kepolaran kimia (25) kelaruta n Perak Sulfat (Ag 2 SO 4 ) (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) Bentuk (24) Bilangan Kelimpahan transport di alam (14) (83)(84)(85)(86)(87) densitas (11) Mobilitas ion (88)(89)(90)(91) Sintesi Berat Titik Lebur molekul(5-9) s (13) (19) Difusi Warna (92)(93)(94)(95) Bau (21)…”

“…elektron (56)(57)(58)(59)(60)(61)(62)(63)(64) yang digunakan untuk membentuk ikatan kovalen polar (65)(66)(67)(68)(69)(70)(71)(72)(73) lebih kuat tertarik pada salah satu atom. Parameter transfer ion (74)(75)(76)(77)(78) disini yaitu kecepatan hanyut (79)(80)(81)(82) , bilangan transport (83)(84)(85)(86)(87) , mobilitas ion (88)(89)(90)(91) , difusi (92)(93)(94)(95) , dan hukum I Fick (96)(97)(98)(99)(100)(101) dari senyawa perak sulfat (Ag2SO4).…”