| 1. |
- Gustafsson, Gustaf, et al.
(författare)
-
Mechanical characterization and modelling of the temperature-dependent impact behaviour of a biocompatible poly(L-lactide)/poly(ε-caprolactone) polymer blend
- 2015
-
Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161 .- 1878-0180. ; 51, s. 279-290
-
Tidskriftsartikel (refereegranskat)abstract
- Poly(ε-caprolactone) (PCL) is a ductile, bioabsorbable polymer that has been employed as a blend partner for poly(L-lactic acid) (PLLA). An improvement of the material strength and impact resistance of PLLA/PCL polymer blends compared to pure PLLA has been shown previously. To use numerical simulations in the design process of new components composed of the PLLA/PCL blend, a constitutive model for the material has to be established. In this work, a constitutive model for a PLLA/PCL polymer blend is established from the results of compressive tests at high and low strain rates at three different temperatures, including the body temperature. Finite element simulations of the split Hopkinson pressure bar test using the established constitutive model are carried out under the same condition as the experiments. During the experiments, the changes in the diameter and thickness of the specimens are captured by a high-speed video camera. The accuracy of the numerical model is tested by comparing the simulation results, such as the stress, strain, thickness and diameter histories of the specimens, with those measured in the experiments. The numerical model is also validated against an impact test of non-homogenous strains and strain rates. The results of this study provide a validated numerical model for a PLLA/PCL polymer blend at strain rates of up to 1800 s−1 in the temperature range between 22 °C and 50 °C.
|
|
| 2. |
- Lay, Makara, et al.
(författare)
-
Changes in the dielectric constant of interphase volume in polyimide-ceramic nanocomposites: A power law model approach
- 2022
-
Ingår i: Journal of Applied Polymer Science. - : WILEY. - 0021-8995 .- 1097-4628. ; 139:6
-
Tidskriftsartikel (refereegranskat)abstract
- The interphase properties in nanocomposites indicate the interaction between filler and matrix, which is dependent on the preparation method, shape, and size of filler and the chemical interaction between two phases. Local chemical environment in polymer matrix give rise to the different dielectric properties compared to that of bulk material. These properties allow the understanding of their effects on the dielectric properties and glass transition (T-g) of the nanocomposites. In this study, interphase power law model was used to predict the interphase properties based on the experimental dielectric constant of polyimide (PI) with BaTiO3, TiO2, and ZrO2 nanocomposites. They were prepared via in situ polymerization of PI whose dielectric constant were increased at interphase filler volume fraction of BaTiO3, TiO2, and ZrO2 at 3.8, 2.05, and 1.7, respectively. These results indicate that PI/ceramics nanocomposites had poor dispersion and weak interphase interaction between the filler and the matrix, as an evidence of scanning electron microscopy and Fourier transform infrared spectroscopy results. However, PI incorporated with high aspect ratio of BaTiO3 nanofiber shows better dispersion than nanocomposites of TiO2 and ZrO2 filled PI; therefore provide higher dielectric constant and T-g.
|
|
| 3. |
- Shimizu, Hideo, et al.
(författare)
-
Tissue Reaction to a Novel Bone Substitute Material Fabricated With Biodegradable Polymer-Calcium Phosphate Nanoparticle Composite
- 2016
-
Ingår i: Implant Dentistry. - : Lippincott Williams & Wilkins. - 1056-6163 .- 1538-2982. ; 25:5, s. 567-574
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: The aim of this study was to evaluate the effectiveness of a novel bone substitute material fabricated using a biodegradable polymer-calcium phosphate nanoparticle composite. Methods: Porous structured poly-L-lactic acid (PLLA) and hydroxyapatite (HA) nanoparticle composite, which was fabricated using solid-liquid phase separation and freeze-drying methods, was grafted into bone defects created in rat calvarium or tibia. Rats were killed 4 weeks after surgery, and histological analyses were performed to evaluate new bone formation. Results: Scanning electron microscopic observation showed the interconnecting pores within the material and the pore diameter was approximately 100 to 300 mm. HA nanoparticles were observed to be embedded into the PLLA beams. In the calvarial implantation model, abundant blood vessels and fibroblastic cells were observed penetrating into pores, and in the tibia model, newly formed bone was present around and within the composite. Conclusions: The PLLA-HA nanoparticle composite bone substitute developed in this study showed biocompatibility, elasticity, and operability and thus has potential as a novel bone substitute.
|
|
