Aliphatic Diisocyanate Research Articles

Exploring structure/property relationships to health and environmental hazards of polymeric polyisocyanate prepolymer substances-2. Dermal sensitization potential in the mouse local lymph node assay.

The sensitization potencies of twenty custom-designed monomer-depleted polymeric polyisocyanate prepolymer substances and their associated toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI) monomer precursors were investigated by means of the mouse Local Lymph Node Assay (LLNA). These polymeric prepolymers were designed to represent the structural features and physical-chemical properties exhibited by a broad range of commercial polymeric polyisocyanate prepolymers that are produced from the reaction of aromatic and aliphatic diisocyanate monomers with aliphatic polyether and polyester polyols. The normalization of LLNA responses to the applied (15-45-135mM) concentrations showed that the skin sensitization potency of polymeric polyisocyanate prepolymers is at least 300 times less than that of the diisocyanate monomers from which they are derived. The sensitization potency of the prepolymers was shown to be mainly governed by their hydrophobicity (as expressed by the calculated octanol-water partition coefficient, log Kow) and surfactant properties. Neither hydrophilic (log Kow <0) nor very hydrophobic (log Kow >25) prepolymers stimulated lymphocyte proliferation beyond that of the dosing vehicle control. The findings of this investigation challenge the generally held assumption that all isocyanate (-N=C=O) bearing substances are potential skin (and respiratory) sensitizers. Further, these findings can guide the future development of isocyanate chemistries and associated polyurethane applications toward reduced exposure and health hazard potentials.

Influence of the Reaction Injection Moulding Process on the Thermomechanical Behaviour of Fast Curing Polyurethane

In this contribution, the influence of the reaction injection moulding process on the thermomechanical material behaviour of aliphatic hexamethylene diisocyanate (HDI) based fast curing polyurethane is demonstrated. Uniaxial tensile tests, temperature-frequency dependent dynamic mechanical thermal analysis (DMTA) and Differential Scanning Calorimetry (DSC) are used to show the differences in properties for ten different sets of process parameters. The mould and resin components temperature, the mass flow during the filling process and the residence time during the reaction process of the polyurethane are varied in several stages. Further experiments to determine the molar mass of the molecular chain between two crosslinking points of the polyurethane are used to explain the process influences on the thermomechanical properties. Thus, a direct correlation between manufacturing and material properties is shown. In addition, the mutual effect of the different parameters and their overall influence on the material behaviour is presented.

Fire-retardant effect of titania-polyurea coating and additional enhancement via aromatic diamine and modified melamine polyphosphate

Polymeric materials and composites are well suited to support structures in marine conditions due to their corrosion resistance. However, their low glass transition temperature makes them vulnerable to softening at high temperatures. Hence, fire retardancy is a key aspect if these materials are selected to ensure stiffness under flammable conditions. In this paper, a fire-retardant polyurea coating for industrial applications is proposed. The aromatic diamine and aliphatic diisocyanate are believed to have a synergistic effect in improving flame properties. Moreover, various combinations of flame-retardant additives with aromatic and aliphatic-based polyurea are mixed to further improve fire-retardancy. Through the characterizations of their glass transition temperature and delay in the ignition, it indicates that the combination of Talc and melamine polyphosphate may provide an outstanding enhancement for the Titania-polyurea coating, and such enhancement may improve its original tensile and compression strength, and surface hardness as well.

Superhydrophobic coordination polyurethane films based on methylolated-cardanol and hexamethylene diisocyanate: Synthesis, characterization and antibacterial evaluation

A novel in-situ formation of bio-based coordination polyurethane (CPUs) have been demonstrated which could substitute to traditional petroleum-built PUs and was formulated by considering the objectives of green and sustainable development. Present work seeks to synthesize cheap and environment-friendly M(II) [Mn(II), Co(II), Ni(II) and Zn(II)] coordinated PUs [M(II)ColF-AliPU] using cardanol formaldehyde (ColF) and aliphatic diisocyanate. The ambient-cured free-standing film/coatings were developed and their properties were discussed and compared. However, free-standing films of Ni(II)-ColF-AliPU and Zn(II)-ColF-AliPU were not obtained even after subjecting the curing at elevated temperatures. FTIR and UV–Visible analysis helps in confirming the octahedral [Mn(II), Co(II), Ni(II)] and tetrahedral [Zn(II)] coordinated structures. The incorporation of metal ions was confirmed by EDX analysis, and the semi-crystalline behavior observed (XRD) was collaborated to the presence of hexamethylene chains of HMDI with nanostructured framework (spheres and tubes). Metal incorporation increases the thermal stability of M(II)-ColF-AliPU and accredits the applications up to 200–220 °C. Co(II) showed the best thermal stability and flame retardancy among other PUs, however, these films were found to be comparatively less thermally stable than aromatic diisocyanate (TDI) based CPUs. After metal integration, the physicomechanical study indicated significant mechanical strength in terms of scratch resistance (1.8 kg), high impact (1.50 × 102 lb./in.), excellent adhesion, bending (1/8 in.), and improved gloss value, although less than M(II)-ColF-ArPU (CPU with aromatic diisocyanate). Water contact angle of ColF-AliPU (151°), Mn(II)-ColF-AliPU and Co(II)-ColF-AliPU (152° and 153°, respectively) revealed the development of superhydrophobic surfaces. The antibacterial activity results revealed Co(II)-ColF-AliPU to be the best composition for inhibiting the bacterial growth (E. coli, S. aureus, K. pneumoniae, and B. subtilis) and thus can be employed in market as antibacterial thin films and coatings.

Self-assembly and crystallization of double crystalline aliphatic thermoplastic biopolyurethane and its nucleation with cellulose nanocrystals

An aliphatic segmented thermoplastic biopolyurethane (STPU), based on aliphatic hexamethylene diisocyanate (HDI) and 1,3 propanediol (1,3PD) as urethane rich phase and a poly(sebacate) as a macrodiol phase, with ∼50 wt% of renewable carbon content, was synthetized and mixed with cellulose nanocrystals (CNC) to develop new bionanocomposites. The phase behaviour of the STPU and derived bionanocomposites was analyzed with a variety of techniques which include differential scanning calorimetry (DSC), isothermal crystallization, X-ray scattering and atomic force microscopy (AFM). The Isothermal crystallization of the STPU matrix allowed fitting to the Lauritzen-Hofmann model and calculation of the overall crystallization constant, Kgτ. Further dynamic thermal analysis by X-ray scattering and DSC allowed the determination of the impact of CNC on the morphology and nucleation of the urethane rich phase. Self-nucleation experiments with the STPU matrix allowed quantification of the nucleation effect of the CNC.

Synthesis and modification of spherical SiO2 nanoparticles with different particle sizes and morphologies and their effects on the properties of thermoplastic polyurethane urea elastomers

AbstractA thermoplastic polyurethane urea (TPUU) elastomer with superior mechanical and thermal properties was recently reported from our group and synthesized by asymmetric aliphatic diisocyanate and diamine. In order to enhance its performance, this TPUU was further modified with spherical SiO2 nanoparticles in this work, and the influence of the size and morphology of spherical SiO2 nanoparticles on mechanical, thermal, and thermomechanical properties of TPUU was investigated. The results showed that spherical SiO2 nanoparticles could significantly improve the mechanical, thermal, and thermomechanical properties of TPUU, which increased, with the decrease of the particle size of SiO2 nanoparticles. Especially, compared with solid spherical SiO2 nanoparticles, TPUU nanocomposites filled with hollow spherical SiO2 (HSSiO2) particles showed abnormal but unique stress–strain behavior, and their elongations at break increased with the decrease of particle size of HSSiO2 nanoparticles.

Introducing a flexible drug delivery system based on poly(glycerol sebacate)-urethane and its nanocomposite: potential application in the prevention and treatment of oral diseases

In this study, a novel biopolymer based on poly(glycerol sebacic)-urethane (PGS-U) and its nanocomposites containing Cloisite@30B were synthesized by facile approach in which the crosslinking was created by aliphatic hexamethylene diisocyanate (HDI) at room temperature and 80 °C. Moreover, metronidazole and tetracycline drugs were selected as target drugs and loaded into PGSU based nanocomposites. A uniform and continuous microstructure with smooth surface is observed in the case of pristine PGS-U sample. The continuity of microstructure is observed in the case of all bionanocomposites. XRD result confirmed an intercalated morphology for PGSU containing 5 wt% of clay nanoparticles with a d-spacing 3.4 nm. The increment of nanoclay content up to 5%, the ultimate tensile stress and elastic modulus were obtained nearly 0.32 and 0.83 MPa, which the latter was more than eight-fold than that of pristine PGS-U. A sustained release for both dugs was observed by 200 h. The slowest and controlled drug release rate was determined in the case of PGSU containing 5 wt% clay and cured at 80 °C. A non-Fickian diffusion can be concluded in the case of tetracycline release via PGS-U/nanoclay bionanocomposites, while a Fickian process was detected in the case of metronidazole release by PGS-U/nanoclay bionanocomposites. As a result, the designed scaffold showed high flexibility, which makes it an appropriate option for utilization in the treatment of periodontal disease.

Supramolecular polyurea hydrogels with anti-swelling capacity, reversible thermochromic properties, and tunable water content and mechanical performance

Supramolecular polyurea (PU) hydrogels with combined anti-swelling capacity, thermochromic properties, and tunable water content and mechanical performance were obtained by immersing phase separated PU films with hydrophilic soft segments in water till swelling equilibrium. The multiple H-bonds within hard-segment domains are critical to the swelling and mechanical properties, which were rationally designed by using simultaneously two aliphatic diisocyanates with different symmetry and varying molar ratio. Consequently, the hydrogels exhibit a wide range of equilibrium water content (57–80%), elastic modulus (22–476 kPa), breaking strength (33–1720 kPa), and elongation at break (160–1460%). The hydrogels also exhibit fast recovery during cyclic loading-unloading. The incorporation of strong quadruple H-bonds into hard-segment domains endowed the hydrogels with stable anti-swelling capacity. Additionally, the hydrogels changed from transparent to opaque reversibly upon heating and cooling, originating from the phase transition of soft segments. The developed supramolecular PU hydrogels show promising potentials in many fields like smart windows.

Photocrosslinkable gelatin/collagen based bioinspired polyurethane-acrylate bone adhesives with biocompatibility and biodegradability

Hard or soft tissue adhesives have been presented as a promising candidate to replace traditional wound closure methods. However, there are mechanical strength problems in biological adhesives and biocompatibility problems in synthetic-based adhesives. At this point, we aimed to remove all these disadvantages and produce a single adhesive that contains all the necessary features and acrylate functionalized UV-curable polyurethane formulations were produced with high crosslink density, high adhesion strength, biocompatibility and injectable property for easy application as potential biomedical adhesives. Aliphatic isophorone diisocyanate (IPDI) was used as the isocyanate source and β-cyclodextrin was used for host-guest relationship with gentamicin by crosslinking. Proteins (gelatin (GEL), collagen (COL)) and PEGs of various molecular weight ranges (P200, P400, P600) were selected as the polyol backbone for polyurethane synthesis due to their multiple biological activities such as biocompatibility, biodegradability, biomimetic property. Several techniques have been used to characterize the structural, thermal, morphological, and various other physicochemical properties of the adhesive formulations. Besides, the possibility of its use as a hard tissue adhesive was investigated by evaluating the tissue adhesion strength in vitro and ex vivo via a universal testing analyzer in tensile mode. Corresponding adhesive formulations were evaluated by in vitro and in vivo techniques for biocompatibility. The best adhesion strength results were obtained as 3821.0 ± 214.9, and 3722.2 ± 486.8 kPa, for IPDI-COL-P200 and IPDI-GEL-P200, respectively. Good antibacterial activity capability toward Escherichia coli Pseudomonas aeruginosa, and Staphylococcus aureus were confirmed using disc diffusion method. Moreover, cell viability assay demonstrated that the formulations have no significant cytotoxicity on the L929 fibroblast cells. Most importantly, we finally performed the in vivo biodegradability and in vivo biocompatibility evaluations of the adhesive formulations on rat model. Considering their excellent cell/tissue viability, fast curable, strong adhesion, high antibacterial character, and injectability, these adhesive formulations have significant potential for tissue engineering applications.

Reprocessable polylactide-based networks containing urethane and disulfide linkages

One of the ways of improving the mechanical properties of polylactide (PLA), which is produced from renewable resources, is crosslinking. In this contribution crosslinked polylactide was obtained by coupling of PLA star polymers using aliphatic diisocyanate, resulting in poly(ester-urethanes). To obtain crosslinked material, able to reprocess, disulfide groups undergoing exchange reactions were introduced into the PLA network structure during the synthesis step. Networks without disulfide groups both, without and with additional low molecular weight diol (diethylene glycol), replacing diol containing disulfide bond (2-hydroxyethyl disulfide) were also prepared for comparative study of mechanical and rheological properties. DSC and FT IR analyses of the networks indicated the presence of hydrogen bonding in obtained materials which influences the ability of disulfide linkages to exchange. The networks with disulfide groups were able to rearrange only at a temperature at which hydrogen bonds were broken (above 100 °C). The ability to rearrange network structure manifested itself in lower storage modulus (G’) above glass transition (Tg = 38–48 °C) as well as faster stress relaxation in comparison with the analogous network without disulfide groups. A PLA-based network containing a sufficiently high density of disulfide groups could be reprocessed at a temperature above 170 °C.

Silver- and Zinc-Decorated Polyurethane Ionomers with Tunable Hard/Soft Phase Segregation.

Segmented polyurethane ionomers find prominent applications in the biomedical field since they can combine the good mechanical and biostability properties of polyurethanes (PUs) with the strong hydrophilicity features of ionomers. In this work, PU ionomers were prepared from a carboxylated diol, poly(tetrahydrofuran) (soft phase) and a small library of diisocyanates (hard phase), either aliphatic or aromatic. The synthesized PUs were characterized to investigate the effect of ionic groups and the nature of diisocyanate upon the structure–property relationship. Results showed how the polymer hard/soft phase segregation was affected by both the concentration of ionic groups and the type of diisocyanate. Specifically, PUs obtained with aliphatic diisocyanates possessed a hard/soft phase segregation stronger than PUs with aromatic diisocyanates, as well as greater bulk and surface hydrophilicity. In contrast, a higher content of ionic groups per polymer repeat unit promoted phase mixing. The neutralization of polymer ionic groups with silver or zinc further increased the hard/soft phase segregation and provided polymers with antimicrobial properties. In particular, the Zinc/PU hybrid systems possessed activity only against the Gram-positive Staphylococcus epidermidis while Silver/PU systems were active also against the Gram-negative Pseudomonas aeruginosa. The herein-obtained polyurethanes could find promising applications as antimicrobial coatings for different kinds of surfaces including medical devices, fabric for wound dressings and other textiles.

Actuator Behaviour of Tailored Poly(thiourethane) Shape Memory Thermosets.

In this work, a new family of poly(thiourethane) shape memory thermosetting actuators was developed and characterized. These materials can be easily prepared from mixtures of two different aliphatic diisocyanates and a trithiol in the presence of a latent catalyst, allowing an easy manipulation of the formulation. Rheological studies of the curing process confirm the latent character of the formulations. The glass transition temperatures and the mechanical properties can be modified by varying the proportion of diisocyanates (hexamethylene diisocyanate, HDI, and isophorone diisocyanate, IPDI) with stoichiometric amounts of trimethylolpropane tris(3-mercaptopropionate). The shape-memory behavior was deeply investigated under three different conditions: unconstrained, partially constrained, and fully constrained. Tests were performed in single cantilever bending mode to simulate conditions closer to real complex mechanics of thermomechanical actuators under flexural performances. The complex recovery process in single cantilever bending mode was compared with that obtained using tensile mode. The results evidenced that the amount of recovery force in fully constrained conditions, or energy released during the recovery process in partially constrained, can be modulated by simply changing the proportion of both diisocyanates. A simple model based on Timoshenko beam theory was used for the prediction of the amount of work performed. The reported results are an important guideline to design shape-memory materials based on poly(thiourethane) networks, establishing criteria for the choice of the material depending on the expected application.

Polyurethanes synthetized with polyols of distinct molar masses: Use of the artificial neural network for prediction of degree of polymerization

AbstractThe molar mass of the polyurethanes (PUs)' reagents directly influences their thermal response, affecting both the polymerization process and the enthalpy and the degree of reaction. This study reports applying an artificial neural network (ANN), associated with surface response methodology (SRM) models, to predict the calorimetric behavior of certain PU's bulk polymerizations. A noncatalyzed reaction between an aliphatic hexamethylene diisocyanate (HDI) and a polycarbonate diol (PCD) with distinct molar masses (500, 1000, and 2000 g/mol) was proposed. A high level of reliability of the predicted calorimetric curves was obtained due to an excellent agreement between theoretical and modeled results, enabling creating a 3D surface response to predict the reaction kinetics. Also, it was possible to observe that the polymerization kinetics is affected by the OH group's association phenomena. The applied methodology can be extended for other materials or properties of interest.

Stoichiometric modulation of triazine based polyurea frameworks for carbon dioxide capture

Synergistic modulation of morphology, porosity and end functionalities in porous polyurea frameworks (PPFs) was accomplished via stoichiometry control in one pot facile strategy under catalyst free room temperature conditions. Monomer feed optimization of an aliphatic diisocyanate with melamine, employing 1,4-dioxane solvent, rendered PPF-1, PPF-2 and PPF-3 manifesting tailored terminal moieties and thermal profiles. FTIR spectral data corroborated the formation of urea linkages as well as the existence of tuned reactive capping for ensuing PPFs. A high thermochemical stability was attributed to the combined effect of heat resistant urea linkages, heterocyclic aromatic triazine rings and crosslinks between the binary monomer mixtures. Distinct morphologies and surface areas were established for individual PPFs, with PPF-3 exhibiting the highest BET surface area. PPF-3 was further probed for CO2 capture capacity at different temperatures and demonstrated a good CO2 adsorption in comparison with the existing porous polymers of comparable surface areas. Simultaneous modulation of multiple structural attributes and appreciable CO2 uptake provide an impetus to unlock the immense potential of these PPFs for carbon dioxide capture under extreme thermochemical milieu.

Degradability of poly(ether-urethanes) and poly(ether-urethane)/acrylic hybrids by bacterial consortia of soil

An enrichment culture strategy was used to obtain natural consortia from soil in order to study the biodegradability of poly(ether-urethanes) (PUE). PUE were synthesized with different aliphatic diisocyanate group, termed PUIPDI and PUHMDI. In addition, PUE/acrylic hybrids, termed PUH90:DEA10 and PUH70:DEA30 consisted of PUHMDI and increasing ratio of 2-(diethylamino)ethyl methacrylate (DEA) were tested. PUIPDI was biodeteriorated through urea-bond hydrolysis by a consortium dominated by Acinetobacter. A higher biodeterioration rate was demonstrated for PUHMDI, which exhibited large surface holes and a greater weight loss. The hydrolysis of ester-urethane bonds and the oxidation of soft-segment ether bonds were the key reactions identified, possibly by Acinetobacter, Mycobacterium, Sphingopyxis and Pseudomonas, which were present in this consortium. Diverse metabolic functions were also predicted. The addition of DEA favored the biodegradability of PUH:DEA hybrids demonstrated by the increased weight loss, swelling degree and the hydrolysis of DEA-ester bond. Urethane and ether bonds degradation were also detected. PUH:DEA hybrids selected even bacterial consortia, most likely by allowing better access to the nutrients. Pseudomonadaceae and Bradyrhizobiaceae families got relevance in these consortia and their outstanding features were cell mobility and quorum sensing. This work has provided a deeper insight into PUE biodegradation by proposing the chemical mechanisms, bacterial taxa and functions that could be implicated.

Influence of Graphene Oxide Contents on Mechanical Behavior of Polyurethane Composites Fabricated with Different Diisocyanates.

The exceptional behavior of graphene has not yet been entirely implicit in the polymer matrix. To explore this fact in the present work, two series of Polyurethan (PU) composites were synthesized. The structural modification was observed by the use of two different diisocyanate of methylene diisocyanate (MDI) and hexamethylene diisocyanate (HMDI) in hydroxylterminated polybutadiene (HTPB) by using I,4 Butane diol (BD) as the chain extender. The variation in hard segment up to 25 (wt.%) in both series led to significant changes in the mechanical behavior of graphene oxide (GO) induced composites. Both series were prepared by an in situ polymerization process. Fourier transform infrared (FTIR) analysis showed a peak in the region of 1700 cm−1, which confirmed the conversion of the NCO group into urethane linkages. Thermal gravimetric analysis (TGA) revealed a thermal stability up to 450 °C @ 90% weight loss. The swelling behavior showed the optimum uptake of 30% of water and 40% of dimethyl sulfoxide (DMSO) with aliphatic diisocyanate. The values of storage modulus (E′), complex modulus (E*), and compliance complex (D*) were observed up to 7 MPa, 8 Mpa, and 0.7 MPa−1, respectively. The degree of entanglement (N) values were calculated from DMA and were found in the range of 1.7 × 10−4 (mol/m3). Phase segregation of PU was observed by scanning electron microscopy (SEM), elucidating the morphology of composites.

Eco-friendly Route for Thermoplastic Polyurethane Elastomers with Bio-based Hard Segments Composed of Bio-glycol and Mixtures of Aromatic-Aliphatic and Aliphatic-Aliphatic Diisocyanate.

Application of bio-based diisocyanates with low volatility instead petrochemical diisocyanates has positive impact on environment by reduction of hazardous effects on living organisms and lead to bio-based polyurethanes (bio-PUs) with good usage properties. This work was focused on the synthesis and chosen properties examination of partially bio-based thermoplastic polyurethane elastomers (bio-PUs) obtained using diisocyanate mixtures, polytetrahydrofurane (PolyTHF) and bio-1,3-propanediol (bio-PDO). Two types of diisocyanate mixtures were prepared as follows: aliphatic–aliphatic based on hexamethylene diisocyanate with partially bio-based aliphatic diisocyanate Tolonate™ X FLO 100 (HDI-FLO) and aromatic–aliphatic based on diphenylmethane diisocyanate with partially bio-based diisocyanate (MDI-FLO) with reduction of 25 mass% of petrochemical diisocyanate. Bio-PUs were obtained via prepolymer method. Thermoplastic polyurethane elastomers have been examined in the terms of chemical structure and thermal, thermomechanical, mechanical and physicochemical properties. Bio-PU based on HDI-FLO diisocyanate mixture exhibited higher thermal stability. The beginning of thermal decomposition took a place at lower temperature ca. 30 ºC) and lower rate than the MDI-PU based materials. DMA analysis showed that HDI-FLO based polyurethanes exhibited greater capacity to accumulate energy and higher stiffness. Both materials characterized similar tensile strength and hardness, but with difference that TPU based on HDI-FLO relieved greater elongation at break about 360% reached 813%. Taking into account versatile properties of bio-TPU, these material can find application in many branches of industry.

Design and Assessment of a Polyurethane Carrier Used for the Transmembrane Transfer of Acyclovir

The Herpes simplex viruses (HSV-1, HSV-2) are responsible for a wide variety of conditions, from cutaneous-mucosal to central nervous system (CNS) infections and occasional infections of the visceral organs, some of them with a lethal end. Acyclovir is often used intravenously, orally, or locally to treat herpetic infections but it must be administered with caution to patients with kidney disease and to children of early age. The main objectives of this study were to synthesize and evaluate new polyurethane nanoparticles that might be used as proper transmembrane carriers for acyclovir. Polyurethane particles were obtained by a polyaddition process: a mixture of two aliphatic diisocyanates used as organic phase was added to a mixture of butanediol and polyethylene glycol used as aqueous phase. Two different samples (with and without acyclovir, respectively) were synthesized and characterized by UV-Vis spectra in order to assess the encapsulation efficacy and the release profile, FT-IR, DSC, SEM, and SANS for structural characterization, as well as skin irritation tests. Nearly homogeneous samples with particle sizes between 78 and 91 nm have been prepared and characterized revealing a medium tendency to form clusters and a high resistance to heat up to 300 °C. The release profile of these nanoparticles is characteristic to a drug delivery system with a late discharge of the loaded active agents. Very slight increases in the level of transepidermal water loss and erythema were found in a 15-day evaluation on human skin. The results suggest the synthesis of a non-irritative carrier with a high encapsulation efficacy that can be successfully used for the transmembrane transfer of acyclovir.

Synthesis and characterization of novel laccol based polyurethanes

AbstractDevelopment of polyurethanes (PU) has come a long way from their origin in 1937 and has unique applications in a diverse set of fields. Recent PU developments are focusing more on the naturally‐derived diols in the synthesis process in an effort to make them more environmentally friendly. In this study, three different diisocyanates (aliphatic, cycloaliphatic, and aromatic diisocyanates) were combined with laccol, which extracted from Vietnamese lacquer sap (Toxicodendron succedanea) to synthesize novel PUs. Influence of the different diisocyanates in novel PUs, hydrogen bonding capability, and crosslinking ability were investigated to provide a broader characteristic scope for future developments. Resulting materials illustrated good thermal stability after exposed to higher temperatures and the hydrogen bonding regions corresponding to NH (3326 cm−1) and CO (1652 cm−1) groups were shifted to higher wavenumber according to Fourier transform infra‐red spectroscopy analysis. Further curing occurred with temperature treatment and improved the overall quality of novel PUs. Powder X‐ray analysis, micro hardness, and swelling analysis were utilized to identify molecular packing and crosslinking effects. Higher crosslink density observed for cycloaliphatic and aromatic diisocyanate incorporated novel polyurethanes compared to aliphatic diisocyanate incorporated polyurethane.

Biomimetic Polyurethane 3D Scaffolds Based on Polytetrahydrofuran Glycol and Polyethylene Glycol for Soft Tissue Engineering.

In this study, a novel polyurethane porous 3D scaffold based on polyethylene glycol (PEG) and polytetrahydrofuran glycol (PTMG) was developed by in situ polymerization and freeze drying. Aliphatic hexamethylene diisocyanate (HDI) as a nontoxic and safe agent was adopted to produce the rigid segment in polyurethane polymerization. The chemical structure, macrostructure, and morphology—as well as mechanical strength of the scaffolds—were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), and tensile tests. The results show that the HDI can react mildly with hydroxyl (–OH) groups of PEG and PTMG, while gas foaming action caused by the release of CO2 occurred simultaneously in the reactive process, resulting in a uniform porous structure of PU scaffold. Moreover, the scaffolds were soaked in water and freeze dried to obtain higher porosity and more interconnective microstructures. The scaffolds have a porosity of over 70% and pore size from 100 to 800 μm. The mechanical properties increased with increasing PEG content, while the hydrophilicity increased as well. After immersion in simulated body fluid (SBF), the scaffolds presented a stable surface structure. The gas foaming/freezing drying process is an excellent method to prepare skin tissue engineering scaffold from PTMG/PEG materials with high porosity and good inter connectivity.