Flexural and flammability evaluation of a new bio-based polyurethane foam (PUF) with alumina trihydrate (ATH) added as flame retardant were carried out. The PUF was obtained from a blend of vegetable oils. Flexural behavior of the polyurethane with different mass fractions of flame retardant (ATH) was investigated according to ASTM D790-17. Flammability tests were performed according to ASTM D3801-20 and ASTM D635-14 for the vertical and horizontal positions, respectively. The ATH addition influenced the flexural strength of the tested specimens, showing mean values for pure PUF and PUF with 50% of ATH were very close, but the highest value was obtained for PUF with 20% of ATH. Besides, the maximum strain value under flexural load was substantially reduced as the ATH mass increased, which was 11.4% for pure PUF and 3.38% for PUF with 50% of ATH. The flexural modulus increased with ATH incorporation up to 40% mass fraction. The obtained values for pure PUF, PUF with 40% of ATH and PUF with 50% of ATH specimens were 30.63 ± 1.95 MPa, 73.01 ± 2.82 MPa, and 62.16 ± 2.30 MPa, respectively. In addition, flammability test results presented better responses as the amount of ATH increased. PUF with 40% of ATH received V-2 classification, and PUF with 50% of ATH obtained HB classification. Therefore, the results for PUF with the addition of ATH show that the new bio-based material can be designed by using different mass fractions. Thus, this material becomes very useful for many types of applications, such as furniture and automobile industries, as well as sandwich structures and building constructions.
Many methods have been developed to test and evaluate the mechanical properties of the biopolymer from castor oil employed in implants and osteo-repositions, among other things. Most of the methods are performed under quasi-static and cyclic loads (creep and relaxation tests) and under high strain rate, uniaxial compression conditions. This paper presents and discusses the development and applicability of a simple load-application apparatus, devised to reduce shear and barrelling effects on specimens and allow for conventional strain around 45%. Besides contributing valuable information on the mechanical behavior of the castor oil polyurethane, the results of this research point to multiple biomedical applications for this material
Compression and morphological evaluation of a new bio-based polyurethane foam (PUF) with aluminum hydroxide (ATH) added as flame retardant were carried out. The PUF was obtained from a blend of vegetable oils. Compression behavior of the polyurethane with different mass fractions of flame retardant (ATH) was investigated according to ASTM D1621–16. The ATH addition highly increased the compression yield strength of the specimens, going from 0.85 MPa (no ATH) to 2.34 MPa ( + 50%wt ATH). The compression yield strain did not show a noteworthy difference up to 40% ATH, presenting a significant decrement in the PUF + 50%ATH. The compression elasticity modulus increased from 15.40 MPa (no ATH) up to 139.77 MPa ( + 50%wt ATH). SEM images were used in order to evaluate the morphological structure of the foam. Regarding the cell sizes, there was no pattern observed, therefore, the cell sizes were adopted as random. The shapes of the cells were detected as elliptical in two different directions in the same cross-sectional area. The digital image correlation (DIC) technique showed higher strain values where the transverse ellipsoid-shaped cells were located, therefore, the load-oriented ellipsoids presented higher stiffness. Thus, the results for PUF with addition of ATH show that the bio-based material presented an important improvement in the compression properties, which allows this material to become more useful for different applications, such as furniture, building and automobile industries, as well as sandwich structures.
Hip joint prosthesis are structural components that still have some challenging problems such as the interaction of physical and biological properties between the stem and the human femur. Composite materials allow to obtain high strength structures with a large variety of modulus of elasticity and favorable characteristics in the context of orthopedic implants. Therefore, the objective of this work was the development of a prosthesis model with biopolymeric matrix, namely the polyurethane (PU) derived from castor oil, reinforced with fiberglass. The implants were made of pure PU, PU with fiberglass, and PU with glass fiber and calcium carbonate. The reinforcement was constructed in the form of a core to be inserted into the hip prosthesis. The core and stem prototypes were produced using three-dimensional printing techniques, and subsequently used in the manufacture of flexible silicone molds. The results showed good mechanical potentialities of this material for orthopedics applications.
The aim of this work is to evaluate the changes in compression properties of a bio-based polyurethane foam after exposure to 90 °C for different periods of time, and to propose a method to extrapolate these results and use a numerical approach to predict the compression behaviour after degradation for untested conditions at different degradation times and temperatures. Bio-based polymers are an important sustainable alternative to oil-based materials. This is explained by the foaming process and the density along the material as it was possible to see in a digital image correlation analysis. After 60 days, stiffness was approximately decreased by half in both directions. The decrease in yield stress due to thermo-oxidative degradation had a minor effect in the foaming directions, changing from 352 kPa to 220 kPa after 60 days, and the transverse property was harshly impacted changing from 530 kPa to 265 kPa. The energy absorption efficiency was slightly affected by degradation. The simulation of the compression stress-strain curves were in accordance to the experimental data and made it possible to predict the changes in mechanical properties for intermediate periods of degradation time. The plateau stress for the unaged foam transverse to the foaming direction presented experimental and numerical values of 450 kPa and 470 kPa, respectively. In addition, the plateau stresses in specimens degraded for 40 days present very similar experimental and numerical results in the same direction, at 310 kPa and 300 kPa, respectively. Therefore, this paper presents important information regarding the life-span and degradation of a green PUF. It provides insights into how compression properties vary along degradation time as function of material operation temperature, according to the Arrhenius degradation equation.
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