Viscoelastic Polyurethane Foams for Use as Auxiliary Materials in Orthopedics

One of the essential factors in prostheses is their fitting. To assemble a prosthesis with the residual limb, so-called liners are used. Liners used currently are criticized by users for their lack of comfort, causing excessive sweating and skin irritation. The objective of the work was to develop viscoelastic polyurethane foams for use in limb prostheses. As part of the work, foams were produced with different isocyanate indexes (0.6–0.9) and water content (1, 2 and 3 php). The produced foams were characterized by scanning electron microscopy, computer microtomography, infrared spectroscopy, thermogravimetry and differential scanning calorimetry. Measurements also included apparent density, recovery time, rebound elasticity, permanent deformation, compressive stress value and sweat absorption. The results were discussed in the context of modifying the foam recipe. The performance properties of the foams, such as recovery time, hardness, resilience and sweat absorption, indicate that foams that will be suitable for prosthetic applications are foams with a water content of 2 php produced with an isocyanate index of 0.8 and 0.9.

Production of Biodegradable Palm Oil-Based Polyurethane as Potential Biomaterial for Biomedical Applications

Being biodegradable and biocompatible are crucial characteristics for biomaterial used for medical and biomedical applications. Vegetable oil-based polyols are known to contribute both the biodegradability and biocompatibility of polyurethanes; however, petrochemical-based polyols were often incorporated to improve the thermal and mechanical properties of polyurethane. In this work, palm oil-based polyester polyol (PPP) derived from epoxidized palm olein and glutaric acid was reacted with isophorone diisocyanate to produce an aliphatic polyurethane, without the incorporation of any commercial petrochemical-based polyol. The effects of water content and isocyanate index were investigated. The polyurethanes produced consisted of > 90% porosity with interconnected micropores and macropores (37–1700 µm) and PU 1.0 possessed tensile strength and compression stress of 111 kPa and 64 kPa. The polyurethanes with comparable thermal stability, yet susceptible to enzymatic degradation with 7–59% of mass loss after 4 weeks of treatment. The polyurethanes demonstrated superior water uptake (up to 450%) and did not induce significant changes in pH of the medium. The chemical changes of the polyurethanes after enzymatic degradation were evaluated by FTIR and TGA analyses. The polyurethanes showed cell viability of 53.43% and 80.37% after 1 and 10 day(s) of cytotoxicity test; and cell adhesion and proliferation in cell adhesion test. The polyurethanes produced demonstrated its potential as biomaterial for soft tissue engineering applications.

Rigid Polyurethane Foams with Various Isocyanate Indices Based on Polyols from Rapeseed Oil and Waste PET

Developing polyols derived from natural sources and recycling materials attracts great interest for use in replacing petroleum-based polyols in polyurethane production. In this study, rigid polyurethane (PUR) foams with various isocyanate indices were obtained from polyols based on rapeseed oil and polyethylene terephthalate (RO/PET). The various properties of the prepared PUR foams were investigated, and the effect of the isocyanate index was evaluated. The closed-cell content and water absorption were not impacted by the change of the isocyanate index. The most significant effect of increasing the isocyanate index was on the dimensional stability of the resulting foams. This is due to the increased crosslink density, as evidenced by the increased formation of isocyanurate and increase of the glass transition temperature. Additionally, the influence on compression strength, modulus, and long-term thermal conductivity were evaluated and compared with reference PUR foams from commercially available polyols. Rigid PUR foams from RO/PET polyol were found to be competitive with reference materials and could be used as thermal insulation material.

Thermal properties of polyurethane elastomers from soybean oil-based polyol with a different isocyanate index

The aim of this work was to determine the influence of used soybean oil (SO)-based polyol on the thermal properties of tested polyurethane elastomers (PUEs), with a different value of isocyanate index (INCO). The thermal properties determined by thermogravimetric analysis and differential scanning calorimetry show that the highest INCO causes an increase in hydrogen bonds in PUEs and higher thermal stability. A structural analysis and degree of phase separation (DPS) of the tested PUEs were carried out via Fourier transform infrared spectroscopy. This analysis showed that at INCO = 1.02, the largest number of urethane bonds arises in PUE. The physicomechanical properties of PUEs were also tested via density, resilience, hardness, and wear resistance. The results concluded that the increasing number of –NCO groups during production of PUEs with SO polyol changes the number of hydrogen bonds and DPS and causes the increase of properties such as thermal resistance, storage modulus, cross-linking density, and wear resistance.

Evaluation of Foaming and Nucleation and Growth Mechanism of Soy-Based Polyurethane Foams

The foaming and nucleation and growth mechanism of soybean oil-based polyurethane (SPU) were determined by the degree of hydrogen bonding, and isocyanate groups. New types of SPU were prepared by the different NCO/OH molar ratio (isocyanate index) from 1.0 to 2.0 in a soy polyol/polyether polyol (MDI) system. Foaming and nucleation and growth mechanisms of SPU were studied by fluorescence microscope (FM), scanning electron microscope (SEM), energy disperse spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT-IR). It indicated that the isocyanate index affected remarkably the velocity of foaming and the critical nucleation radius of SPU and the ester functional group increased with the increase of isocyanate index. The nucleation and growth phase transition were dominated by the diffusion controlled nucleation and isocyanate content was the key factor of foam formation.

Performance properties of rigid polyurethane-polyisocyanurate/brewers’ spent grain foamed composites as function of isocyanate index

In the presented work, rigid polyurethane-polyisocyanurate (PUR-PIR) foams filled with brewers’ spent grain (BSG) were prepared. The influence of the isocyanate index (II) on its performance was investigated. Foams obtained with higher isocyanate index required a higher amount of hydrofluorocarbon physical blowing agent to provide the same apparent density of material. An increase of isocyanate index resulted in a slight decrease of cell size, which was related to the increased crosslink density due to enhanced generation of allophanate and biuret groups. Deterioration of compressive strength, from 226 to 202 kPa was observed with the rise of the isocyanate index. Dynamic mechanical analysis and swelling tests confirmed the increase of crosslink density with the increasing isocyanate index. The glass transition temperature rose from 165.7°C to 193.2°C. Fourier transform infrared (FTIR) analysis indicated an increase of the isocyanurate rings’ content in composites with a higher isocyanate index, causing noticeable enhancement of thermal stability. The onset of degradation was shifted from 196°C to 211°C.

Synthesis of Novel Cationic Waterborne Polyurethane from Natural Rubber and its Properties Testing

The novel natural rubber based cationic waterborne polyurethanes (cWPUs) with having quaternary amine as an emulsifier were successfully synthesized by additional polymerization. These polyurethanes were synthesized by the reaction of hydroxyl the method of telechelic natural rubber. Molecular weight approximately of hydroxyl telechelic natural rubber (HTNR) for 3000 g.mole-1, toluene-2,4-diisocyanate (TDI), and N-methyl diethanol amine (NMDEA) (used as an emulsifier) were prepared for cWPU. The concentrations of NMDEA were examined in range of 0 – 2.0 moles. From the results under the isocyanate index of 100, the study revealed that cWPU with well-distributing had to consist of emulsion concentration more than 1.50 moles. Zetasizer nanorange was used to identify the prepared cWPU particle size distribution. The results showed that the particle size of cWPU was decreased from 86.6 to 78 nm with increasing of NMDEA concentration. The smallest particle size was 2 moles with non-acetic acid odor, and very soft film. In addition, cWPU would be well-dispersed more than 4 months. The 1H NMR spectroscopy and FT-IR confirmed that the cWPU has been successfully synthesized from natural rubber.