Prepolymer Mixing Process Research Articles

Flame Retardant Waterborne Polyurethanes: Synthesis, Characterization, and Evaluation of Different Properties

A series of flame retardant waterborne polyurethanes (WBPUs) with varying NCO:OH mole ratio, i.e., isocyanate:hydroxyl groups, was synthesized using phosphorus-based polyester polyol and isophorone diisocyanate (IPDI). The phosphorus moiety was kept in the polymeric chain, which improves flame retardancy of the WBPU films. The prepolymer mixing process was adopted for the synthesis route of WBPU systems. The presence of structural-functional groups was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The thermal stability and percentage char yield were observed by TGA analysis. As a consequence of the existence of phosphorous moiety, these WBPUs also exhibit flame retardancy, which was examined by limiting oxygen index (LOI) and UL-94 test. All the samples show an increment in thermal stability with an increase in NCO:OH ratio. Maximum flame retardancy was obtained in FWP5 and FWP6 systems with LOI value of 32%.

A new route for synthesis of polyurethane vinyl acetate acrylate emulsions as binders for pigment printing of cotton fabrics

HEREIN, two polyurethane oligomers were successfully synthesized using a prepolymer mixing process. The prepolymers were synthesized based on the step-growth addition polymerization of polypropylene glycol, Methylene diphenyl diisocyanate and 2-hydroxyethyl methacrylate or 2-hydroxyethyl acrylate. Isopropanol was functioned as the isocyanate blocking agent. Thereafter, different terpolymer emulsions were prepared by the emulsion graft copolymerization with the vinyl acetate monomer in presence of 2-ethylhexyl acrylate as a vinyl monomer. The chemical structures of the synthesized oligomeric monomers were probed by FTIR spectroscopy and found to vary with the content of acrylic monomer used in the oligomer synthesis phase (i.e.hydroxyethyl acrylate or hydroxyethyl methacrylate). The topography, thermal stability, and particle size of terpolymers were investigated by SEM, TGA, and zeta potential, respectively. The TGA results demonstrated marked enhancement in thermal stability of the synthesized terpolymers up to ca. 600°C, which was concurrent with enhanced surface homogeneity and film properties as evidenced by the SEM images. These terpolymers showed also property enhancement as binders for textile pigment printing in terms of rubbing resistance, color strength and fastness to washing when compared to the commercial binders. These judgments would provide a new competent synthesis route by introducing polyurethane acetate vinyl acrylate as the binder for use in pigment printing of cotton fabrics.

Green Approach for the Development of Novel Flame Retardant Waterborne Polyurethanes: Synthesis and its Characterizations

Waterborne polyurethanes (WBPUs) are developed from water as a medium instead of solvent. Due to high volatile organic compounds (VOC) content in the solvents, the government has banned solvent based polyurethanes in few countries. Therefore, in present work attempts have been made to synthesize polyurethanes by the green approach in terms of utilizing water as a solvent medium. Waterborne polyurethane is one of the unique utmost quickly developing environmental friendly material. It has been found extensively useful in the field of applications like coatings, adhesives for automobiles and wood. Furthermore, extremely useful in flexible substrates such as leather, membranes, textiles and rubbers. These fields require a prominent flame retardancy of the materials, but the instant flammability is a major disadvantage of WBPU, which limits its use in further application in a rigorous situation of fire. Hence, flame retardancy has been improved in present work by incorporating phosphorous moiety in the polymeric chain in a reactive way. By the use of prepolymer mixing process and varying NCO:OH mole ratio, various flame retardant waterborne polyurethanes were synthesized. These synthesized WBPUs were coated on mild steel panels, glass panels and wood. Characterization was done through Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. Microtrac particle size analyzer was used to investigate the particle size. Scratch resistance, pencil hardness, adhesion (cross hatch), flexibility 1/4“ mandrel test, chemical resistance and solvent resistance test of the coated panels were also performed. Flame retardancy was inspected by limiting oxygen index (LOI) and UL-94 test methods.

Synthesis and Characterisation of New Water-Based Polyurethane Dispersion via Solvent-Free Prepolymer Mixing Process

A new type of water-based polyurethane dispersion (NWPUD) was synthesised from isophorone diisocyanate, polyethylene glycol (Mw = 400 g/mol and 1000 g/mol), dimethylol propionic acid, and 1,4-butanediol using the prepolymer mixing process and without the incorporation of any volatile organic solvent. The hard-/soft-segment molar ratio of NWPUD formulations was varied with higher values (i.e. 5 to 11) allowing excess diisocyanate to reduce the prepolymer viscosity. The formulation using polyethylene glycol 400 g/mol with a hard-/soft-segment molar ratio of 5 failed by solidifying upon dispersion in water. Using polyethylene glycol 1000 g/mol and varying hard segment content, successful NWPUD formulations were obtained, all with pH between 6 and 7. FT-IR spectroscopy was used for the identification of chemical structures and functional groups. The colloidal properties of NWPUD formulations such as particle size, zeta potential, and dispersion stability were investigated to demonstrate feasibility for application in industrial coatings. The size distribution of NWPUD formulations varied from heterogeneous to homogeneous when the hard-/soft-segment molar ratio was increased. It was found that formulations with hard-/soft-segment molar ratio between 7 and 11 exhibited the most desirable dispersion stability within the zeta potential range of -50 to -55 mV.

Studies on Influence of the Size of Waterborne Polyurethane Nanoparticles on Coating Performance

Abstract Waterborne polyurethanes are extensively utilized as in coatings and adhesive applications because of their outstanding performance as solventless system. To achieve such a product with almost no or minimum volatile organic compounds, water is the best choice to utilize as a solvent medium in coating formulations to eliminate organic solvents from the final products. During the synthesis of the waterborne polyurethanes, the particle size of final dispersion products depends on many factors like NCO:OH content, the concentration of acid, synthesis conditions, chain extension process etc. In this research work using the prepolymer mixing process and changing NCO:OH content, flame retardant waterborne polyurethane dispersions (FWBPUD) were prepared from phosphorous containing polyester polyol and isophorone diisocyanate (IPDI). These prepolymers were neutralized by triethylamine followed by the addition of predefined quantity of water. Diethylenetriamine was used as a chain extender. These FWBPUs were further coated on various substrates. Characterization was done using Fourier transform infrared and Nuclear magnetic resonance spectroscopy. The average particle size of the dispersions was characterized by Microtrac-analyser. An influence of the size of waterborne polyurethane nanoparticles on the coating performance was described by scratch resistance, pencil hardness, adhesion (cross-hatch), flexibility 1/4“ mandrel test, chemical resistance and solvent resistance test. Due to the presence of phosphorous moiety, these FWBPUs also show flame retardancy which was investigated by limiting oxygen index (LOI) and UL-94 test methods. The FWBPU dispersions were stable for 8 months.

Studies on the effect of the size of waterborne polyurethane nanoparticles on properties and performance of coatings

Present research work was performed utilizing prepolymer mixing process and varying NCO:OH mole ratios. Waterborne polyurethane dispersions (WBPUs) were prepared from phosphorous containing polyester polyol and isophorone diisocyanate. These prepolymers were neutralized by triethylamine followed by the addition of optimized quantity of water. Diethylenetriamine was used as a chain extender. These WBPUs were further coated on mild steel panels, glass panels, and wood. Chemical structure was confirmed using instrumental methods. Microtrac particle size analyzer was used to analyze the particle size. An impact of the size of nanoparticles on the performance of coatings was explained by different testing methods.

Synthesis and Properties of Waterborne Polyurethane (WBPU)/Modified Lignin Amine (MLA) Adhesive: A Promising Adhesive Material.

A series of waterborne polyurethane (WBPU)/modified lignin amine (MLA) adhesives was prepared using MLA as a chain extender by a prepolymer mixing process. A successful Mannich reaction was achieved during the synthesis of MLA by reacting lignin with bis(3-aminopropyl)amine. Higher tensile strength, Young’s modulus, and thermal stability were recorded for WBPU/MLA adhesives with higher MLA contents. The WBPU/MLA adhesive materials were used to coat polyvinyl chloride (PVC) substrates. The adhesive strength increased with increasing MLA content. More importantly, the MLA also enhanced the WBPU/MLA coating in terms of adhesive strength at moderately high temperatures as well as under natural weather exposed conditions. The adhesive strength was essentially unaffected with 6.48 mol % MLA in the WBPU/MLA coating after exposure to natural weather conditions for 180 days.

Synthesis of waterborne polyurethane dispersions with glycolyzed product from pet waste: Effect of hard segment content on its properties

A series of waterborne polyurethane (WPU) with different hard segment content were synthesized by a prepolymer mixing process from isophorone diisocyanate, dimethylol propionic acid, the glycolyzed product of poly(ethylene terephthalate) as the soft segment and trimethylol propane as the crosslinking agent. The effect of the hard segment content on the thermal and mechanical properties of WPU films was studied. The results reveal that the hard segment content play a key role in the thermal and physical-mechanical properties of the WPU films. The waterborne polyurethane synthesized from circulating reuse of waste PET materials have good thermal stability and mechanical properties, which is confirmed their potential application as protective and decorative coatings.

Preparation and properties of waterborne polyurethane/self-cross-linkable fluorinated acrylic copolymer hybrid emulsions using a solvent/emulsifier-free method

A series of waterborne polyurethane (WBPU)/fluorinated self-cross-linkable acrylic copolymer hybrids (WBPU/FPA) emulsions were successfully prepared by solvent/emulsifier-free prepolymer mixing process. This study focused on the effect of vinyl triethoxysilane (VTES, 0–15 wt%)/butyl acrylate (BA, 15–0 wt%) weight ratio on the properties of WBPU/self-cross-linked fluorinated acrylic copolymer hybrids for high-performance water-repellent coating materials. As the VTES content increased, the particle size of hybrid emulsion decreased; however, the viscosity of the emulsion increased. The glass transition temperature Tgα, tensile modulus, storage modulus, and hardness increased with increasing VTES content. The surface tension of film sample decreased with increasing VTES content up to about 9 wt% and then levelled off. The tensile strength and water/methylene iodide contact angles of film sample increased with increasing VTES content up to about 9 wt% and then almost levelled off. The optimum VTES/BA weight ratio was found to be about 9:6 wt% to obtain high-performance water-repellent coating materials.

Synthesis and Characteristics of m-TMXDI-based Waterborne Polyurethane Modified by Aqueous Chitosan

Environmental issues have received increasing attention recently. Compared to solvent borne polyurethane (PU), waterborne PU requires relatively little solvent dosage. Therefore, waterborne PU is used to replace traditional solvent borne PU to satisfy environmental and economic requirements. Chitosan is a material that has been discussed widely in recent years because of its exceptional antimicrobial performance, biocompatibility, bioactivity, and biodegradability. This study primarily uses a prepolymer mixing process to synthesize m-TMXDI based waterborne PU with different ratios of aqueous chitosan and chain extenders (ethylenediamine; EDA). Modification reactions are conducted and waterborne PU modified by aqueous chitosan is synthesized. Through this experimental method, emulsions modified by different compositional proportions of aqueous chitosan to EDA were tested. For material determination, FTIR, NMR, and XPS were used to conduct chemical structure determination and GPC molecular weight tests. Regarding membrane properties, a contact angle meter analyzed the hydrophility of the membrane and the antimicrobial performance of the prepared waterborne PU membrane against Staphylococcus aureus and Escherichia coli. The test results showed the following characteristics: (1) The terminal NCO group of the waterborne PU (WPU) was bonded with the terminal amino group(-NH2) of chitosan, and (2) as the proportion of aqueous chitosan added increased, improvements were observed regarding molecular weight, hydrophility, and antimicrobial performance.

Preparation of Waterborne Polyurethane‐OMt Nanocomposites and Effect of Clay on UV Degradation

SummaryWaterborne polyurethane polymers (WPU) have gained importance for some decades because of their environmentally friendly characteristics due to low or zero content of solvents. Polyurethane properties can be modified by changing segmental structure or incorporating inorganic fillers into the polymer matrix. Montmorillonite (Mt) clay which is a member of smectite family is widely used in polymer clay composites as a filler. In this work, linear WPU nanocomposites were synthesized using different polyols as soft segment via acetone process which has many advantages over the prepolymer mixing process in terms of reliable reproducibility and convenience for obtaining linear polyurethanes. Sodium modified montmorillonite (NaMt) clay was used without any chemical pretreatment. WPU nanocomposites were prepared via in‐situ polymerization method by modification of sodium modified montmorillonite (NaMt) clay in polyol and following polyurethane reaction. Finally, spectroscopic, thermal, morphological characterizations and UV weathering tests carried out. As a result, different thermal and mechanical properties were observed due to different soft and hard segment content. Furthermore, increasing clay content caused lowering of resistance against UV degradation.

Synthesis, morphology, and properties of waterborne m-TMXDI-based anionic polyurethane and hybrids

In this study, waterborne polyurethane (WPU) hybrid emulsions with a weight ratio of 2/1 were prepared by emulsion polymerization using a mixture of styrene (St) and/or butyl acrylate (BA) monomers with WPU dispersion. WPU dispersion was synthesized with isocyanic acid and m-tetramethylxylene diisocyanate (m-TMXDI)-based anionic poly(urethane-urea) dispersions using the prepolymer mixing process. The structures of WPU and hybrids were characterized by FTIR spectroscopy. The size and morphology of the latex particles were investigated using dynamic light scattering and transmission electron microscopy, respectively. The stability of the emulsions was determined according to their shelf life and particle size using the dispersion analyser LUMiSizer® with STEP™-Technology. The thermal and mechanical properties of these films were examined by thermogravimetric analysis and strain-stress curves.

Polydimethylsiloxane and Castor Oil Comodified Waterborne Polyurethane

In view of both improving properties of waterborne polyurethane (WPU) and sufficient utilization of renewable resources, a series of polydimethylsiloxane (PDMS) and castor oil (C.O.) comodified anionic WPUs with internal cross-linking was prepared through a prepolymer mixing process. The chemical structure of synthesized polymers was characterized by Fourier transforms infrared spectroscopy (FT-IR). In comparison with traditional linear WPU synthesized from petroleum-based polyols, these novel WPU films exhibited superior properties in solvent and water resistance, thermal stability, and mechanical strength, which suggest promising applications of these new environmentally friendly materials, particularly in the area of decorative and protective coatings. In addition, the results showed that with the increase in PDMS content in these co-modified WPUs the average particle size, the water resistance, and the thermal stability increased accordingly while the solvent resistance and the mechanical properties decreased.

Synthesis and Properties of Caprolactam-Blocked Non-Ionic Waterborne Polyurethane Crosslinker

A novel kind of water-borne caprolactam-blocked non-ionic polyurethane crosslinker (CL-bnp) was prepared by prepolymer mixing process, using hexamethylene diisocyanate (HDI), poly (ethylene glycol) (PEG), 1,1,1-trimethylolpropane (TMP) and caprolactam (CL). The physical properties of prepared blocked polyurethane crosslinker dispersion, such as viscosity, pH and storage stability were measured. The chemical structure and its de-blocking temperature (Tde) were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), and thermo-gravimetric analysis (TGA) techniques. The FTIR confirmed that the NCO groups of the original HDI molecule were completely blocked by this blocking agent. The thermal analysis measurements revealed that the maximum de-blocking ratio temperature of CL-bnp was around 160-170 °C

Synthesis and swelling behavior of pH‐responsive polyurethane/poly[2‐(diethylamino)ethyl methacrylate] hybrid materials

ABSTRACTPolyurethane (PU)/poly[2‐(diethylamino)ethyl methacrylate] hybrids, having a chemical bond between the PU and acrylic moieties and with different compositions, were prepared by the dispersion polymerization of 2‐(diethylamino)ethyl methacrylate (DEA) in the presence of preformed PU chains with polymerizable terminal vinyl groups. The PU dispersion was synthesized according to a prepolymer mixing process by the polyaddition of isophorone diisocyanate, poly(propylene glycol), 2‐hydroxyethyl methacrylate, and dimethylol propionic acid (DMPA). Then, it was dispersed in water by the prior neutralization of the carboxylic acid groups of DMPA with triethylamine, chain‐extended with ethylenediamine. The effect of the DEA content on the swelling properties (water uptake and dynamic swelling degree) at different pHs and at 37°C was determined. The samples were also characterized by Fourier transform infrared spectroscopy and modulated differential scanning calorimetry. The experimental results indicate a higher water uptake when the DEA content was increased on the hybrid materials and a significant change in the kinetics of swelling at pH 4 compared to those at pH 7. The water content of the hydrogels depended on the DEA content, and it was inversely proportional to the pH value. The pure PU film did not show important changes over the pH range examined in this study. The synthesized hybrids were useful as drug‐delivery, pH‐sensitive matrices. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39799.

Effect of total acrylic/fluorinated acrylic monomer contents on the properties of waterborne polyurethane/acrylic hybrid emulsions

Stable emulsions of waterborne poly(urethane-urea) (WBPU, soft segment content: 57 wt%, dimethylol propionic acid: 19 mol%/5.8 wt%)/n-butyl acrylate (BA)/glycidyl methacrylate (GMA)/perfluorodecyl acrylate (PFA) (weight ratio of BA/GMA/PFA: 5/3/2) hybrid materials containing 0-30 wt% of acrylate content (fluorinated acrylate content: 0–6 wt%) were successfully prepared by an emulsifier-free/solvent-free prepolymer mixing process. However, the as-polymerized hybrid emulsion containing 40 wt% of acrylic monomer content was found to be unstable, indicating that near 40 wt% in acrylic monomer content was beyond the limit of the self-emulsifying ability. By the curve fitting analysis of IR-peaks and X-ray photoelectron spectroscopy (XPS) analysis, the C-F content was found to increase with the increase in acrylate content. The average particle size of emulsion, young modulus/ yield point in stress-strain curve, hardness, thermostability, and water/methylene iodide-contact angles of the film sample increased with increasing acrylate content. However, the viscosity of emulsion, the elongation at break, water swelling and surface energy of film samples were significantly decreased with increasing acrylate content. The tensile strength of film sample decreased a little with increasing acrylate content. These results point to the strong potential of WBPU (70 wt%)/acrylate copolymer (30 wt%) hybrid as a coating material with the lowest surface energy (18.18 mN/m) and the highest contact angles (water: 111.76o, and methylene iodide: 79.95°). Open image in new window

Preparation of dendritic waterborne polyurethane-urea/Ni–Zn ferrite composite coatings and investigation of their microwave absorption properties

This study shows the preparation of microwave absorbing composite material by using Ni–Zn ferrite filler and dendritic waterborne polyurethane-urea (WPU) polymer as a matrix. Initially, waterborne polyurethane prepolymers were synthesized by using PEG1500 (WPU1) and PPG1000 (WPU2) polyols via prepolymer mixing process. Then, chain extended with water in the presence of hexamethylenetetramine (HMTA) as crosslinker. Then, 1/1 (w/w) amount of Ni–Zn ferrite was dispersed in the WPU polymer to be converted into a microwave absorbing composite coating (CWPU1 and CWPU2). Structural, mechanical and morphological properties were investigated. The microwave absorption measurements were performed by using transmission/reflection method via waveguide method in the frequency range of 8.2–12.4GHz. Permittivity and permeability measurements were performed in the frequency range of 8.2–12.4GHz. It has been found that CWPU1 which was prepared by using WPU1 polymer indicated broader microwave absorption between 9.4 and 11.7GHz due to its dendritic structure. Besides, permittivity and permeability results indicated that CWPU1 and CWPU2 have distinctive magnetic properties.

Effect of acrylic monomer content on the properties of waterborne poly(urethane‐urea)/acrylic hybrid materials

AbstractStable waterborne poly(urethane‐urea) (WBPU; soft segment content: 57%; dimethylol propionic acid: 19 mol %/5.8 wt %)–polyacrylate(methyl methacrylate/n‐butyl acrylate) (weight ratio: 4/1) hybrid latex (emulsions) with different acrylic contents [0, 10, 20, 30, and 40 wt % based on poly(urethane‐urea)] and without external surfactant were successfully prepared by in situ polymerization during a prepolymer mixing process. However, the as‐polymerized hybrid latex containing 50 wt % of acrylic monomer content was found to be unstable, indicating that about 50 wt % of acrylic monomer content was beyond the limit value of self‐emulsifying ability of WBPU anionomer prepared in this study. The breadth of particle size distribution of hybrid latex increased markedly from 20–75 to 55–275 nm with increasing acrylic monomer content from 0 to 40 wt %. The pristine WBPU and hybrid latex samples containing 10, 20, and 30 wt % of acrylic monomer showed unimodal distributions, whereas the hybrid sample having 40 wt % acrylic monomer content displayed a bimodal distribution with the broadest breadth. As acrylic monomer content increased, the yield point of stress–strain curve, hardness, glass transition, and water resistance of hybrid film samples increased, whereas their abrasion resistance, elongation at break, and elasticity decreased. The tensile strength of hybrid film samples (10–30 wt % of acrylic monomer content) was almost the same as that of pristine WBPU film sample, indicating the intimate molecular mixing between poly(urethane‐urea) and polyacrylate molecules in hybrids. However, the hybrid sample having 40 wt % acrylic monomer showed significantly diminished performance, which might be due to the deviation from intimate molecular mixing. From these results, the optimum acrylic monomer content was found to be about 30 wt %, which realized reasonably advantages of both poly(urethane‐urea) and acrylic polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Properties of Waterborne Polyurethanes: Effect of NCO/OH Ratio

Waterborne polyurethanes(WPUs) based on isophorone diisocyanate(IPDI), Polybutylene adipate (PBA) and dimethylolproprionic acid(DMPA) were synthesized by prepolymer mixing process. Effect of NCO/OH ratio on the properties of the dispersions was studied. The structure of the WPUs was studied by FT-IR. Besides the mechanical properties and water swelling of the films, the number average diameters of the dispersions and the viscosity of WPUs were characterized, results showed that all WPUs had higher solid content (over 45%). With higher NCO/OH ratio, WPUs had bigger dispersion size and lower dispersion viscosity; the casting film had higher water swelling, lower tensile strength, and more water-soluble substance.

Effect of Poly(dimethylsiloxane) Content on the Properties of Water-Borne Poly(urethane-urea)s Containing MDI

Low photo- and water-resistance is often cited as the problem of MDI-based WBPU. This study addressed this problem. Water-borne poly(urethane-urea)s (WBPUs) were synthesized using a pre-polymer mixing process from 4,4'-methylenebis(phenyl isocyanate)(MDI)/4,4-dicyclohexylmethyl diisocyanate (H12MDI) (15/85 mole %)/dimethylol propionic acid (DMPA)/ethylene diamine (EDA)/triethylamine (TEA) with different poly(propylene glycol) (PPG, M n = 2000)/hydroxyl terminated poly(dimethylsiloxane) (PDMS, M n = ∼550) molar ratios. This study highlights the effect of PDMS content on the inherent viscosity, hydrogen-bonding, storage modulus, tan δ peak intensity, tensile modulus/strength, elongation (%) at break, water swelling (%), contact angle, and the yellowness index of WBPUs containing MDI. The mechanical properties (strength/modulus), water-resistance and photo-resistance of WBPUs containing MDI increased significantly in proportion to the PDMS content. These results indicate the potential for using multi-performance WBPU with PDPS for WBPU coatings.