Waterborne Poly Urethane-urea Research Articles

Bioinks Functionalized with Natural Extracts for 3D Printing

In the search of materials valid for direct ink writing (DIW) 3D printing and with special interest for the biomedical and pharmaceutical applications, the development of bioactive inks for DIW is of great interest. For that purpose, in this work bioactive waterborne polyurethane–urea inks were prepared by addition of natural extracts (logwood, chestnut, and alder buckthorn) and cellulose nanofibers (CNF). The rheological behavior of the inks proved to be strongly dependent on the extract type and content, and the addition route used. Inks prepared by ex-situ incorporation of the extracts showed a strong gel-like behavior, as did inks prepared with chestnut and alder buckthorn extracts, which, in turn, hindered a continuous flow during the printing process, resulting in 3D printed parts with poor shape fidelity. On the other hand, inks prepared in-situ and with logwood extract showed more facility to flow and higher homogeneity, which translated in better printability and better shape fidelity, further enhanced for CNF containing inks. 3D printed composites showed reinforced mechanical behavior, as well as in materials with enhanced antibacterial behavior. Overall, the possibility to successfully prepare bioactive inks valid for 3D printing was proven.

Robust, self-healing, anti-corrosive waterborne polyurethane urea composite coatings enabled by dynamic hindered urea bonds

To meet the increasing concerns for health, safety, and the environment, traditional solvent coatings are gradually replaced by their waterborne counterparts and the development of robust and self-healing waterborne polymers is showing important application significance. Herein, waterborne polyurethane urea composite coatings (WPUU) with dynamic hindered urea bonds are reported. The dispersion of WPUU synthesized with hindered amine as the chain extender has a smaller particle size. The mussel-inspired polydopamine modification was applied to improve the dispersion and interfacial interactions of carbon nanotubes (CNTs) in the WPUU matrix. Due to the dynamic reversibility of the hindered urea and abundant hydrogen bonding, the resulting WPUU-2T2B can achieve self-healing at 70 °C, also showing good mechanical toughness, the tensile strength of 34.0 MPa and elongation at break of 530 %. After adding the modified CNTs, 10%PDA@CNTs/WPUU demonstrates the tensile strength of 22.4 MPa, elongation at break of 251 % and yield strength of 13.1 M Pa. The self-healing properties of nanocomposites are still retained. The maximum electrical conductivity of the composite coating reaches 56.8 S m−1. The composite coating can recover excellent corrosion resistance in the electrolyte environment after healing, which could ensure its safety and sustainability in the long-term service. We envisage this work offers an idea for the fabrication of environmentally friendly, self-healing, corrosion resistant and electrically conductive coatings with good thermal stability and robust mechanical properties.

Enhancing the Mechanical Properties of 3D-Printed Waterborne Polyurethane-Urea and Cellulose Nanocrystal Scaffolds through Crosslinking.

In this work, shape-customized scaffolds based on waterborne polyurethane-urea (WBPUU) were prepared via the combination of direct ink writing 3D-printing and freeze-drying techniques. To improve the printing performance of the ink and guarantee a good shape fidelity of the scaffold, cellulose nanocrystals (CNC) were added during the synthesis of the WBPUU and some of the printed constructs were immersed in CaCl2 prior to the freeze-drying process to promote ionic crosslinking between calcium ions and the polyurethane. The results showed that apart from allowing the ink to be successfully printed, obtaining scaffolds with good shape fidelity, the addition of the CNC resulted in a greater homogeneity of the porous structure as well as an increase of the swelling capacity of the scaffolds. Additionally, the CNC has a reinforcement effect in the printed systems, presenting a higher compression modulus as the CNC content increases. In the case of samples crosslinked by calcium ions, a rigid shell was observed by scanning electron microscopy, which resulted in stiffer scaffolds that presented a lower water absorption capacity as well as an enhancement of the thermal stability. These results showed the potential of this type of post-printing process to tune the mechanical properties of the scaffold, thus widening the potential of this type of material.

Effect of Cellulose Nanofibers' Structure and Incorporation Route in Waterborne Polyurethane-Urea Based Nanocomposite Inks.

In order to continue the development of inks valid for cold extrusion 3D printing, waterborne, polyurethane-urea (WBPUU) based inks with cellulose nanofibers (CNF), as a rheological modulator, were prepared by two incorporation methods, ex situ and in situ, in which the CNF were added after and during the synthesis process, respectively. Moreover, in order to improve the affinity of the reinforcement with the matrix, modified CNF was also employed. In the ex situ preparation, interactions between CNFs and water prevail over interactions between CNFs and WBPUU nanoparticles, resulting in strong gel-like structures. On the other hand, in situ addition allows the proximity of WBPUU particles and CNF, favoring interactions between both components and allowing the formation of chemical bonds. The fewer amount of CNF/water interactions present in the in situ formulations translates into weaker gel-like structures, with poorer rheological behavior for inks for 3D printing. Stronger gel-like behavior translated into 3D-printed parts with higher precision. However, the direct interactions present between the cellulose and the polyurethane-urea molecules in the in situ preparations, and more so in materials reinforced with carboxylated CNF, result in stronger mechanical properties of the final 3D parts.

Bioactive inks suitable for 3D printing based on waterborne polyurethane urea, cellulose nanocrystals and Salvia extract

This work explores the preparation of a bioactive ink suitable for direct ink writing (DIW) 3D printing by adding extract obtained from Salvia officinalis L. during the synthesis of a waterborne polyurethane urea (WBPUU). Additionally, to guarantee a successful printing performance, cellulose nanocrystals (CNC), a well-known rheology modulator, have been added after the synthesis process. In order to predict the behaviour of the inks in DIW, the rheological properties of the inks with and without the Salvia extract and the CNC have been studied. The results showed that the incorporation of Salvia extract into the WBPUU ink resulted in a decrease of the viscosity, yield point and storage modulus, obtaining an ink that cannot maintain the shape after being printed. On the contrary, the incorporation of the CNC into the WBPUU/Salvia ink increased the aforementioned rheological parameters leading to the obtaining of pieces presenting a good shape fidelity without compromising their printability. Finally, scaffolds were prepared from the printed pieces by freeze-drying technique and were tested against Gram negative Escherichia coli and Gram positive Staphylococcus aureus. The scaffolds containing CNC and Salvia showed bactericide behaviour against both bacteria, which was not seen in the WBPUU matrix, confirming the bioactive capacity of this ink.

Bacteriostatic effect of waterborne polyurethane-urea films containing bioactive plant extracts incorporated by different routes

The environmental awareness has promoted the development of new materials towards eco-friendly systems based on both, green synthesis processes as well as the renewable origin of the raw compounds. In this way, focusing on synthesis methods, the use of waterborne polyurethane-urea dispersions have gained attention due to their versatility leading to a wide variety of applications, broadening the range of applications. In addition, it is worth nothing that the dispersibility in water offers the possibility of incorporating soluble additives, such as plant extracts. Therefore, in this work Melissa officinalis L. plant was selected in order to obtain bioactive plant extract, in order to be incorporated to a waterborne polyurethane-urea dispersion, varying their content as well as using three different incorporation routes. These dispersions were characterized and employed in the preparation of films which were analyzed from the viewpoint of physicochemical, thermal and mechanical properties, among others. Finally, the antibacterial properties of the films were analyzed after 1 and 4 days of incubation, where it was observed that the content and incorporation route of the extract influenced in the behavior of the films against common pathogens (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa).

Biobased Waterborne Polyurethane-Ureas Modified with POSS-OH for Fluorine-Free Hydrophobic Textile Coatings.

Waterborne polyurethane-urea dispersions (WPUD), which are based on fully biobased amorphous polyester polyol and isophorone diisocyanate (IPDI), have been successfully synthesized obtaining a finishing agent that provides textiles with an enhanced hydrophobicity and water column. Grafting of trans-cyclohexanediol isobutyl POSS (POSS-OH) to the biobased polymer backbone has also been investigated for the first time and its properties compared to a standard chain extender, 1,3-propanediol (PDO). The chemical structure of WPUD has been characterized by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The thermal properties have been evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Mechanical properties have been studied by tensile stress–strain analysis. Moreover, the particle size, particle size distribution (PSD), and stability of developed waterborne dispersions have been assessed by dynamic light scattering (DLS), Z-potential, storage aging tests, and accelerated aging tests by analytical centrifuge (LUM). Subsequently, selected fabrics have been face-coated by the WPUD using the knife coating method and their properties have been assessed by measuring the water contact angle (WCA), oil contact angle (OCA), water column, fabric stiffness, air permeability, and water vapor resistance (breathability). Finally, the surface morphology and elemental composition of uncoated and coated fabrics have been studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. All of the synthesized polyurethane-ureas provided the coated substrates with a remarkable hydrophobicity and water column, resulting in a more sustainable alternative to waterproof coatings based on fluoropolymers, such as PTFE. Grafting POSS-OH to the polymeric backbone has led to textile coatings with enhanced hydrophobicity, maintaining thermal, mechanical, and water column properties, giving rise to multifunctional coatings that are highly demanded in protective workwear and technical textiles.

Design of a Waterborne Polyurethane-Urea Ink for Direct Ink Writing 3D Printing.

In this work, polycaprolactone–polyethylene glycol (PCL–PEG) based waterborne polyurethane–urea (WBPUU) inks have been developed for an extrusion-based 3D printing technology. The WBPUU, synthesized from an optimized ratio of hydrophobic polycaprolactone diol and hydrophilic polyethylene glycol (0.2:0.8) in the soft segment, is able to form a physical gel at low solid contents. WBPUU inks with different solid contents have been synthesized. The rheology of the prepared systems was studied and the WBPUUs were subsequently used in the printing of different pieces to demonstrate the relationship between their rheological properties and their printing viability, establishing an optimal window of compositions for the developed WBPUU based inks. The results showed that the increase in solid content results in more structured inks, presenting a higher storage modulus as well as lower tan δ values, allowing for the improvement of the ink’s shape fidelity. However, an increase in solid content also leads to an increase in the yield point and viscosity, leading to printability limitations. From among all printable systems, the WBPUU with a solid content of 32 wt% is proposed to be the more suitable ink for a successful printing performance, presenting both adequate printability and good shape fidelity, which leads to the realization of a recognizable and accurate 3D construct and an understanding of its relationship with rheological parameters.

Biobased Waterborne Polyurethane-Urea/SWCNT Nanocomposites for Hydrophobic and Electrically Conductive Textile Coatings.

Waterborne polyurethane-urea dispersions (WPUD), which are based on 100% bio-based semi-crystalline polyester polyol and isophorone diisocyanate, have been successfully synthesized and doped with single-walled carbon nanotubes (SWCNT) to obtain a finishing agent that provides textiles with multifunctional properties. The chemical structure of WPUD has been characterized by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The thermal properties have been evaluated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA). Mechanical properties have been studied by tensile stress–strain analysis. Moreover, the particle size, particle size distribution (PSD), and stability of developed waterborne dispersions have been assessed by dynamic light scattering (DLS), Z-potential, and accelerated aging tests (analytical centrifugation). Subsequently, selected fabrics have been face-coated by the WPUD using knife coating method and their properties have been assessed by measuring water contact angle (WCA), water column, fabric stiffness, and air permeability. The electrical conductivity of textiles coated with SWCNT-doped WPUD has been evaluated by EN 1149 standard. Finally, the surface morphologies of uncoated and coated fabrics have been studied by scanning electron microscopy (SEM). All of the synthesized polyurethane-ureas provide the coated substrates with remarkable water-repellency and water column, being therefore a more sustainable alternative to waterproof coatings based on fluoropolymers, such as PTFE. The additivation of the polymeric matrices with SWCNT has led to textile coatings with excellent electrical conductivity, maintaining water column properties, giving rise to multifunctional coatings that are highly demanded in protective workwear and technical textiles.

Role of in situ added cellulose nanocrystals as rheological modulator of novel waterborne polyurethane urea for 3D-printing technology

Cellulose nanocrystals (CNC) have been studied as rheological modulator in order to improve the printing performance of a novel polycaprolactone-polyethylene glycol (PCL-PEG) waterborne polyurethane urea (WBPUU) based ink for direct ink writing 3D-printing technology. The cellulose nanocrystals are chemically bonded to the WBPU, since they were added during the synthesis of a WBPUU, in order to tune the rheological properties of the ink and thus, improve the printing performances. The WBPUU-CNC inks have been extensively characterized from the rheological viewpoint and have been subsequently used to print different pieces. To determine the capacity of the CNC to improve the printing performance of this type of inks, we establish the relationship between the rheological properties of the inks and their printing viability by an optimal window of compositions of the inks. Additionally, we have measured the mechanical and thermomechanical properties of printed WBPUU-CNC pieces to evaluate the effective reinforcement of in situ incorporated CNC in the WBPUU-CNC inks. The results showed that the addition of CNC accentuates the shear-thinning behaviour, presenting lower tan δ, especially at the lowest CNC contents compared with the matrix, which resulted in inks with excellent printable properties. Moreover, the shape fidelity is increased by the solid-like behavior due to the filler effect of CNC and confirmed by SEM images. Finally, a large increase in Young’s modulus and thermal and thermomechanical stability were observed on the printed pieces that contained only 0.5 wt% CNC compared to the matrix, suggesting the formation of effective interactions between CNC and WBPUU, as corroborated by FTIR, that lead to a greater reinforcement.

Synthetic scheme to increase the abrasion resistance of waterborne polyurethane–urea by controlling micro‐phase separation

AbstractAs an environmental‐friendly coating material in industry, waterborne polyurethane–urea (WPU) is still not comparable with solvent‐based polyurethane (SPU) in mechanical properties, due to the hydrophilic chain‐extender. Herein, a synthetic scheme to increase the abrasion resistance of WPU with ether diol, and conventional hydrophilic chain‐extender (DMBA, 2,2‐bis[hydroxymethyl]butanoic acid) is revealed. This study discuss the degree of micro‐phase separation (DPS) with toughness, elongation, abrasion resistance, and compared with the WPU contain various types of diol, such as esters, ether and carbonates, and the ether‐based SPU. From the results, the major factor that affect to the abrasion properties of WPU is DPS, which is highly depend on the chemical structure of diol, and hard segment content. WPU film achieve higher toughness with ether‐based diol with higher DPS, and better abrasion resistance than SPU. This study demonstrate a strategy for the composition designing, and the synthesis of high‐abrasion resistance WPU by controlling the micro‐phase separation, and content of DMBA without any inorganic fillers.

Green nanocomposites from Salvia-based waterborne polyurethane-urea dispersions reinforced with nanocellulose

Waterborne polyurethane-urea (WBPUU) dispersions, products having none or low contents of organic solvents, depending on the used synthesis process, can provide suitable environmentally-friendly strategies to prepare novel materials. Moreover, waterborne systems enable the incorporation of aqueous dispersible nanoentities and soluble additives, which provides a strategy to design versatile functional materials with tailored properties. Having demonstrated in previous work the bacteriostatic properties of a 3 wt% Salvia-based WBPUU against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, this work is focused in the preparation of Salvia-based WBPUU added with cellulose nanocrystals (CNC) tackling the preparation of functional green nanocomposite films with increased mechanical properties. Through this strategy, nanocomposites loaded with 1, 3 and 5 wt% of CNC were prepared, showing an effective CNC incorporation avoiding agglomerates. CNC addition is able to modulate soft and hard phase’s segregation, inducing enhanced mechanical stiffness, together with improved deformability, while retarding thermomechanical instability to higher temperatures.

Addition of small amounts of graphene oxide in the polyol during the synthesis of waterborne polyurethane urea adhesives for improving their adhesion properties

Mixtures of polyadipate of 1,4-butanediol polyol and different small amounts (0.01–0.10 wt%) of graphene oxide (GO) were added during the synthesis of waterborne polyurethane urea dispersions (PUDs) carried out with the acetone method. The addition of 0.02–0.04 wt% GO increased the T-peel strength of plasticized poly (vinyl chloride)/PUD/plasticized poly (vinyl chloride) joints whereas the addition of 0.05–0.10 wt% GO increased the single lap-shear strength of stainless steel/PUD/stainless steel joints. The improved adhesion of the PUDs containing GO was ascribed to the creation of covalent interactions between the surface groups on the GO surface and the NCO groups of the isocyanate during prepolymer formation, creating new urethane groups; during the phase inversion, the covalently bonded GO sheets were embedded between the polyurethane urea chains inside the PUD particles, this changed the degree of phase separation between the hard and the soft segments. When more than 0.04 wt% GO was added, some GO particles cannot be covalently bonded to the prepolymer during the PUD synthesis but they agglomerated and physically “trapped” between the polyurethane urea chains. As a consequence, the adhesion properties of the PU + GO films were different in the PU films containing 0.01–0.04 wt% GO and the ones containing 0.05–0.10 wt% GO.

Addition of Graphene Oxide in Different Stages of the Synthesis of Waterborne Polyurethane-Urea Adhesives and Its Influence On Their Structure, Thermal, Viscoelastic and Adhesion Properties.

In this study, 0.04 wt % graphene oxide (GO) was added in different stages (before and after prepolymer formation, and during water addition) of the synthesis of waterborne polyurethane-urea dispersions (PUDs) prepared by using the acetone method. The structural, thermal, mechanical, viscoelastic, surface and adhesion properties of the polyurethane-ureas (PUUs) containing 0.04 wt % GO were studied. The addition of GO before and after prepolymer formation produced covalent bonds between the GO sheets and the NCO groups of the isocyanate, whereas the GO sheets were trapped between the polyurethane chains when added during water addition step. As a consequence, depending on the stage of the PUD synthesis in which GO was added, the degree of micro-phase separation between the hard and soft segments changed differently. The addition of GO before prepolymer formation changed more efficiently the polyurethane-urea structure, i.e., the covalently bonded GO sheets disturbed the interactions between the hard segments causing lower percentage of free urethane groups, higher crystallinity, lower storage modulus, higher yield stress and T-peel strength. The interactions between the GO sheets and the polymeric chains have been evidenced by plate-plate rheology, thermal gravimetric analysis and spectroscopy. On the other hand, physical interactions between GO and the polyurethane-urea chains were produced when GO was added in water during the synthesis, i.e., GO was acting as a nanofiller, which justified the improved mechanical properties and high lap-shear strength, but poor T-peel strength.

New Waterborne Polyurethane-Urea Synthesized with Ether-Carbonate Copolymer and Amino-Alcohol Chain Extenders with Tailored Pressure-Sensitive Adhesion Properties.

New waterborne polyurethane-urea dispersions with adequate adhesion and cohesion properties have been synthesized by reacting isophorone diisocyanate, copolymer of ether and carbonate diol polyol and three amino-alcohols with different number of OH groups chain extenders using the prepolymer method. The waterborne polyurethane-urea dispersions were characterized by pH, particle-size distribution, and viscosity, and the polyurethane-urea films were characterized by attenuated total reflectance infrared (ATR-IR) spectroscopy, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and plate-plate rheology (temperature and frequency sweeps). Polyurethane-urea pressure-sensitive adhesives (PUU PSAs) were prepared by placing the waterborne polyurethane dispersions on polyethylene terephthalate (PET) films and they were characterized at 25 °C by creep test, tack and 180° peel test. The waterborne polyurethane-urea dispersions showed mean particle sizes between 51 and 78 nm and viscosities in the range of 58–133 mPa·s. The polyurethane-urea films showed glass transition temperatures (Tgs) lower than −64 °C, and they showed a cross of the storage and loss moduli between −8 and 68 °C depending on the number of OH groups in the amino-alcohol chain extender. Different types of PUU PSAs (removable, high shear) were obtained by changing the number of OH groups in the amino-alcohol chain extender. The tack at 25 °C of the PUU PSAs varied between 488 and 1807 kPa and the 180° peel strength values ranged between 0.4 and 6.4 N/cm, and their holding times were between 2 min and 5 days. The new PUU PSAs made with amino-alcohol chain extender seemed very promising for designing environmentally friendly waterborne PSAs with high tack and improved cohesion and adhesion property.

Influence of the addition of PEG into PCL‐based waterborne polyurethane‐urea dispersions and films properties

ABSTRACTIn this work, segmented waterborne polyurethane‐urea (WBPUU) dispersions containing hydrophobic polycaprolactone (PCL) and hydrophilic poly(ethylene glycol) (PEG) in different molar ratios are synthesized and used for the subsequent preparation of films by casting. The molar ratio of PEG is gradually increased up to 0.20 in order to analyze the effect of low hydrophilic PEG content (from 1.7 to 7.1 wt %) on the properties of resulting dispersions and films. Regarding the dispersions, the addition of PEG results in an increase of the particle size, from 86 ± 1 in the case of pure PCL‐based system to 112 ± 15 for systems containing 7.1 wt % of PEG, as well as in the formation of a core–shell structure in the particles. Films show different behaviors depending on their PEG content. WBPUUs containing just PCL or very low content of PEG in the soft segment present higher stiffness. However, the addition of PEG in a content of 3.4 wt % or higher hinder the ability of the short‐range ordering of the hard segment, increasing the elongation at break from 842 ± 102 MPa for PCL‐based WBPUU to 1312 ± 84 MPa for the system with the highest PEG content. Systems with higher PEG content form nanoparticles with more segregated core–shell structures inducing to the film a higher hydrophilicity. Hence, the addition of PEG to a PCL‐based WBPUU allows to tune the properties of the resulting film increasing the range of application of these materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48847.

Structure and adhesion properties before and after hydrolytic ageing of polyurethane urea adhesives made with mixtures of waterborne polyurethane dispersions

Several waterborne polyurethane urea dispersions (WPUUs) were prepared by mixing different amounts of two waterborne polyurethane urea dispersions made with polyester (WPUU-Polyester) and polycarbonate diol (WPUU-PCD). Their crystallinity, thermal, rheological, viscoelastic and adhesion properties depended on the segmented structure and degree of phase separation which were determined by the different content of the parent dispersions. The PUU films made with WPUU-Polyester+WPUU-PCD mixtures containing more than 50 wt% of WPUU-PCD showed higher hard segments content and lower degree of phase separation, and the addition of 25 wt% of WPUU-Polyester imparted crystallinity to the polyurethane urea due to the interactions between the carbonate groups in the soft segments. The differences in the degree of phase separation and crystallinity of the PUU films made with WPUU-Polyester+WPUU-PCD mixtures were evidenced by the increase in the glass transition temperature associated to the alpha relaxation of the soft segments, and the higher modulus at the cross-over between the storage and loss moduli. Excellent adhesion was obtained in plasticized PVC/WPUU/plasticized PVC joints, and a cohesive failure of PVC was always obtained, irrespective of the composition of WPUU-Polyester+WPUU-PCD mixtures. Furthermore, the adhesion of surface-chlorinated vulcanized styrene-butadiene (SBR) rubber/WPUU+5 wt% hardener/roughened leather joints were high and similar in all joints and a dominant cohesive failure in the rubber substrate was produced. The accelerated ageing by immersion in water at 70 °C during different times showed that the polyurethane urea film and the surface-chlorinated vulcanized SBR rubber/WPUU+5 wt% hardener/roughened leather joint made with WPUU-PCD dispersion were not affected, but noticeable hydrolytic degradation of the ester units in the soft segments was produced in PUU-Polyester and, to a less extent, in PUU-50Polyester/50PCD films and adhesive joints.

Development of waterborne polyurethane-ureas added with plant extracts: Study of different incorporation routes and their influence on particle size, thermal, mechanical and antibacterial properties

Abstract Polyurethane-ureas are a versatile family of polymers which can be employed in a wide range of applications. Among them, waterborne polyurethane-urea (WBPUU) dispersions are gaining relevance in the field of environmentally-friendly products since their productive process adopts green synthesis routes, avoiding the use of organic solvents. Furthermore, their waterborne character can be exploited to incorporate several water compatible ingredients able to confer functional properties to the final materials. Among them, plant extracts, which are known to have relevant bioactivities, can be viewed as interesting candidates. Therefore, in this work, two extracts known to present antimicrobial activity (Melissa officinalis L. and Salvia officinalis L.) were obtained by the infusion method and incorporated into the WBPUU (1, 3 and 5 wt%) following different incorporation routes comprising its adding during different phases of the productive process (post-, in-situ and pre- methods). Thereafter films were prepared by solvent-casting and characterized from the viewpoint of physicochemical, thermal, mechanical, thermomechanical and antibacterial properties and morphologically. The studied incorporation routes resulted in different intercalation mechanisms that varied from extract positioned among the polyurethane-urea nanoparticles (post-method) to extract partially embedded inside them (in-situ and pre-methods), which produced stiffening or flexibilizing effects in the produced films, enhancing in general the antimicrobial characteristics of films after 4 days of incubation comparing with base WBPUU, especially when the extract is embedded.

Waterborne polyurethane-urea dispersion with chain extension step in homogeneous medium reinforced with cellulose nanocrystals

Waterborne polyurethane-urea (WBPUU) dispersions have gained attention towards environmentally-friendly synthesis routes. Differing from the conventional WBPUU synthesis route where the diamine chain extension is performed in heterogeneous medium in the surface of the already formed particles, in this case the chain extension was carried out in homogeneous medium, prior to WBPUU nanoparticles formation. Thus, stable WBPUU dispersion with small particle sizes and narrow distribution was synthesized. Furthermore, cellulose nanocrystals (CNC) were isolated for the preparation of eco-friendly nanocomposites just by mixing. Nanocomposites with different CNC contents were prepared and extensively characterized in terms of physicochemical, thermal, thermomechanical and mechanical properties, hydrophilic behavior and morphology.

Biocompatible waterborne polyurethane-urea elastomer as intelligent anticancer drug release matrix: A sustained drug release study

Waterborne biodegradable polyurethane–urea (WPUU) elastomer is a revolutionary step in the field of green polymer chemistry. In the present study, emulsifier–free biodegradable WPUU elastomer was synthesized by using lysine as an internal emulsifier as well as a chain extender. WPUU elastomer was used as the stimuli–responsive drug release matrix, loaded by cisplatin as a model anticancer drug. Sustained drug release was studied by changing pH (4.4–7.4), drug release medium, and NCO/OH ratio (3–4). Furthermore, significantly inhibitory effect against Sw–620 cancer lines was observed. Highest cumulative drug release of 71.9% was observed at pH of 7.4 in phosphate buffer saline (PBS) by the system having NCO/OH=3 for 250h. The oxidative degradation was evaluated in CoCl2/H2O2 solution. Mechanical properties were tested by using the mechanical testing machine. The synthesized WPUU films exhibited high thermal stability, hardness, tensile strength and hydrophobicity.