Effects of formulation on set-to-touch time of waterborne alkyd resin by uniform design

In order to optimize the formulation of waterborne alkyd resin preparation, a 9-level-3-factor uniform design and regression analysis were firstly employed to evaluate the effects of the selected variables including fatty acid content (L), hydroxyl/carboxyl molar ratio (r) and molar ratio of polyatomic acids (f) on set-to-touch time of film. The results indicate that the data can be adequately fitted with a first-order polynomial model, and the main factors successively affecting set-to-touch time are fatty acid content (L) and molar ratio of polyatomic acid (f). The above model is proved valid within the designed scopes of the investigated formulation parameters by validation experiments. The optimized formulation parameters for waterborne alkyd resin synthesis is predicated as follows according to the model, i.e. L is 30%, r is 1.2, f is 2.2, the result set-to-touch time is 43 min, which significantly shorten the drying time.     

塑料复合膜用水性聚氨酯胶粘剂的研制

以聚酯二元醇、甲苯二异氰酸酯(TDI)、二羟甲基丙酸(DMPA)等为原料，利用两步法工艺，合成出阴离子型聚氨酯(PU)乳液，并配合交联剂制得性能良好的双组分水性PU胶粘剂。研究结果表明：控制-COOH质量分数在1．6％～1．8％、NCO／OH值在1．3～1．4，合成的阴离子型PU乳液粒径较小；随着-COOH的增加，乳液的粘度和胶膜的吸水性增大。以该乳液配制的胶粘剂，贮存稳定，无毒、无污染，剥离强度高，可用于多种塑料复合膜材料的粘接。     

反应性阳离子聚氨酯对羊绒针织物起球性能的影响

以自制的反应性阳离子水性聚氨酯对纯羊绒针织物进行抗起毛起球整理,研究整理剂对纯羊绒针织物整理效果及其服用性能的影响。研究结果表明：在整理剂最佳的应用工艺下（整理剂质量浓度50g/L、浴比1：35、整理液pH5.5、40℃下处理20min、100℃烘干）,可显著提高羊绒针织物的抗起毛起球性能,其起毛起球等级从2.0级提高到4.0级,且织物的手感和白度等风格不受整理剂的影响。     

A fully bio-based waterborne polyurethane dispersion from vegetable oils: From synthesis of precursors by thiol-ene reaction to study of final material

A new linear saturated terminal diisocyanate was synthesized from castor oil-derived undecylenic acid by thiol-ene coupling (TEC) and Curtius rearrangement. The structure of the diisocyanate was carefully examined using Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance (NMR), and ¹³C NMR. This diisocyanate was used as a starting material for the preparation of a fully bio-based waterborne polyurethane dispersion (BPUD) by reacting with castor oil and castor oil-based carboxylic acid-type hydrophilic chain extender, which was prepared from castor oil by using 3-mercaptopropionic acid via TEC. The thermal/mechanical properties of the formed BPUD film were characterized via differential scanning calorimetry, thermogravimetric analysis, tensile test, hardness test, and water resistance test. The fatty acid-derived diisocyanate and the castor oil-based hydrophilic chain extender were used to produce BPUD with favorable properties.     

Polymer/silica nanohybrids by means of tetraethoxysilane sol–gel condensation onto waterborne polyurethane particles

Stable waterborne polyurethane/silica hybrid dispersions were obtained by sol–gel reaction of tetraethoxysilane added to previously synthesized waterborne polyurethane nanodispersions. Two series of polyurethane/silica nanostructures with different silica contents were synthesized using pure polyurethane particles and polyurethane particles previously functionalized with (3-aminopropyl)triethoxysilane (APTES) as colloidal templates. The optimum experimental conditions for tetraethoxysilane sol–gel reaction (T = 75 °C and semi batch polymerization conditions) leading to the formation of silica/polyurethane aqueous nanodispersions were established. The presence of silica was confirmed using TGA, FTIR, ²⁹Si NMR and TEM. TEM images showed an excellent final dispersion of the silica nanoparticles in the polymer matrix when silane functionalized polyurethane nanoparticles were used.     

Electrochemical impedance spectroscopy study of waterborne coatings film formation

In order to establish electrochemical impedance spectroscopy (EIS) as a viable quantitative method for characterization of latex film formation, three waterborne acrylate and styrene–acrylate polymer dispersions were periodically analyzed during a course of 2 weeks. Impedance spectra were fitted on the base of equivalent circuit consisting of a capacitor in parallel with a Warburg element representing film capacitance and the extent of ion diffusion through the film. Calculated EIS parameter values showed a decrease in Warburg diffusion over time, which is a result of particle coalescence and in agreement with the established theory of latex film formation. Atomic force microscopy (AFM) of the samples showed a smoothing of the surface and blurring of interparticle boundaries which confirmed that EIS can be used to study film formation of latex.     

Synthesis and properties of Ricinodendron heudelotii oil based hybrid alkyd–acrylate latexes via miniemulsion polymerization

Ricinodendron heudelotii (R. heudelotii) oil-based novel alkyd–acrylate hybrid latexes were synthesized as waterborne environmental friendly binder for coating systems. Long oil length alkyd resins were synthesized by two-stage alcoholysis–polyesterification reaction with variation of phthalic anhydride (PA) and maleic anhydride (MAH) proportion and further polymerized with methyl methacrylate (MMA) and butyl acrylate (BA) via miniemulsion polymerization. It is found that increasing the proportion of MAH in the alkyd resin enhances monomer conversion and total solid content of the hybrid latex. The latexes exhibited fast drying time at room temperature. The prepared latexes showed a bimodal particle size distribution motion. It is shown that the increase in MAH content in the alkyd moiety has a significant effect on the improved performance properties of hybrid latexes as well as latex films including, fast drying time at room temperature, highly crosslinked network, improved mechanical characteristics before and after UV exposure, better shore A hardness and hydrophobic water repellency contact angle. The results suggested that, the R. heudelotii oil-based alkyd–acrylate hybrid latexes have potential improved properties for manufacture of waterborne coatings and are usable as an alternative to petroleum-based coating systems.     

Abrasion resistance of waterborne polyurethane films incorporated with PU/silica hybrids

We describe polyurethane (PU)/silica hybrids (PSHs) prepared through hydrolysis and condensation reactions of tetraethoxysilane (TEOS) with or without methyltriethoxysilane (MTES) in the presence of polyurethane dispersion, which were subsequently incorporated into waterborne polyurethane (WPU) to prepare composites. The effects of the solid mass ratio of PSHs/WPU on the particle size of composite emulsions, the dispersion of silica nanoparticles in composite films, and the hardness and abrasion resistance of the corresponding films were examined. Composite emulsions possess a nanoscale particle size when incorporated with PSHs prepared using TEOS and MTES as precursors, and are superior to those with PSHs prepared using TEOS alone. Transmission electron microscopy revealed that silica nanoparticles had a uniform distribution in the polymer matrix and agglomerates could be almost completely avoided through in situ modification of silica with Si-CH₃ groups in the polyurethane dispersion. Composite films prepared with this method exhibited a superior hardness and abrasion resistance even at a lower silica content compared with that containing unmodified silica. In particular, optical microscopy and scanning probe microscopy observations demonstrated wear behavior differences among these composite films from the macro- and nanoscale viewpoints, respectively. It is proved that abrasive wear occurs, and surface morphology studies are in accordance with the results of abrasion resistance tests.     

Study on synthesis and thickening property of hyperbranched waterborne polyurethane

A series of hyperbranched waterborne polyurethanes (HWPU-4, HWPU-6 and HWPU-12) containing hydrophobic end groups were prepared by the hyperbranched core and the polyurethane prepolymer. The core was polyol including pentaerythritol (PE-4), hyperbranched polyester with six hydroxyl end groups (HPE-6) and hyperbranched polyester with 12 hydroxyl end groups (HPE-12). The polyurethane prepolymer was synthesized by hexamethylene diisocyanate (HDI), polyethylene glycol (PEG) and hexadecanol. The structures of the hyperbranched cores and HWPUs were characterized by Fourier transform infrared spectra (FTIR), nuclear magnetic resonance spectra (¹H NMR and ¹³C NMR) and gel permeation chromatography (GPC). The influences of HWPU content and structure on its thickening property were studied by the measurement of rotary viscosity. The results showed that the thickening effect of HWPU enhanced with the increase of HWPU content in the aqueous polyurethane emulsion. The thickening effect of HWPU-6 was superior to that of HWPU-4 and HWPU-12 with the same length of hydrophilic chain. In addition, the thickening effect of HWPU with the same core was related to the length of hydrophilic chain and the relative content of hydrophobic end groups.     

Waterborne hybrid polyurethane coatings functionalized with (3-aminopropyl)triethoxysilane: Adhesion properties

Waterborne polyurethanes based on isophorone diisocyanate and two different soft segments, poly(1,4-butylene adipate) and poly(propylene glycol), were end-capped with (3-aminopropyl) triethoxysilane to impart them the ability to crosslink at room temperature. Polyurethanes were synthesized by means of acetone process and stabilized in aqueous medium using dimethylolpropionic acid (DMTA) as internal emulsifier. ¹³C NMR experiments confirmed the insertion of the alkoxysilane. The adhesion properties of the room temperature cured films as a function of alkoxysilane concentration were evaluated. The optimum film formation time and adhesion temperatures were established using the design of experiments (DOE) methodology. The Lap Shear adhesion increased as a function of the alkoxysilane content up to a point, 9.7 wt.% of alkoxysilane, where the adhesion capacity disappeared totally due to the rigidity of the material. Furthermore, both polyester and polyether based systems presented an optimum window, between 5 and 15 wt.% of alkoxysilane, where the synthesized systems promoted good adhesion at high temperatures above 200 °C for more than 24 h.