Synthesis and Characterization of Hyperbranched and Organosilicone Modified Waterborne Polyurethane Acrylates Photosensitive Resin

A new type of waterborne polyurethane acrylate was synthesized for use as a UV curing coating. The N,N-dihydroxy methyl ethyl-3-Methyl aminopropanoate monomer was first prepared via adding reactions of methyl acrylate and diethanol amine with methyl alcohol as the solvent. Then, the hyperbranched prepolymer was obtained by addition of trimethylolpropane with toluenesulfonic acid as catalyst and N,N-dimethyl formamide as solvent. The resulting hyperbranched and organosilicone modified waterborne polyurethane acrylates was synthesized through the mixed reaction of prepolymer and Hydroxy silicone oil, polyethylene glycol-1000, toluene diisocynate, dimethylolpropionic acid, 1,2-propylene glycol, hydroxyethyl acrylate, and triethylamine with dibutyltin dilaurate as the catalyst. The molecular structures were characterized by FT-IR and 1H NMR spectroscopy and GPC analysis and the thermal stability was studied by using TGA. Moreover, the influence of contemodnt of hydroxyl silicone oil, dimethylolpropionic acid, polyethylene glycol-1000, and prepolymer to various of properties such as glossiness, hardness, adhesive force, abrasion resistance, water absorption, elongation at break and tensile strength of films were analyzed. The temperature and catalyst dosage impact on percent conversion of isocyanate group (–NCO) were also studied. It was proven that the best dosage of hydroxyl silicone oil and dimethylolpropionic acid were 4.6%, the dosage of polyethylene glycol-1000 was 50%, and the amount of hyperbranched prepolymer was 0.5%, which could make the film achieve the optimum properties. The percent conversion of isocyanate group (–NCO) was maximum when reacting two hours at 80 °C with 0.2% catalyst.

Improving the Appearance of a 3-Coat-1-Bake Coating Film by Minimizing the Shrinkage Difference between the Three Layers

The 3-coat-1-bake coating system has been widely employed in automobile body painting. This study examined whether the appearance (waviness) of the coating film can be improved by reducing the difference in the shrinkage percentage (by weight) between the primer surfacer and the basecoat and the clearcoat after flow/leveling stops in the clearcoat while baking. To delay the time of flow/leveling stops in the clearcoat (tC) and to reduce the difference in the shrinkage percentage between the basecoat and clearcoat, solventborne clearcoats were prepared by blocking all or part of the isocyanate group with 3,5-dimethylpyrazole (DMP). tC was measured using the electric-field tweezers system while baking at 140 °C. The respective shrinkage percentages of the primer surfacer, basecoat, and clearcoat (ωS, ωB, and ωC, respectively) were measured after tC. tC increased as the DMP content of the solventborne clearcoat increased. The ωC value is lower than the ωS and ωB values when the DMP content is zero; however, the ωC value increased when tC increased, and the ωS and ωB values decreased as tC increased. Wavescan Wa, Wb, Wc, and Wd decreased (i.e., improved the appearance) as |ωS − ωB| + |ωB − ωC| decreased. We confirmed that reducing the difference in the shrinkage percentage between the primer surfacer, basecoat, and clearcoat after tC is an effective way to improve the appearance.

Velcrand Functionalized Polyethylene

Velcrands are a specific class of cavitands whose complementary surfaces induce self-dimerization. The insertion of a velcrand as physical cross-linking unit into a polymer is reported. To this purpose, the velcrand was functionalized at the lower rim with an isocyanate group. The functional velcrand was reacted with poly (ethylene-co-(2-hydroxethylmethacrylate)) (PE-HEMA), a polymer equipped with free hydroxyl groups suitable for reaction with the isocyanate group. The obtained functionalized polymer was characterized by nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR), proving the introduction of velcraplexes in the polymer. Films with varying amounts of velcrands were obtained by solution casting and slow evaporation, testifying the processability of the functionalized polymers. The obtained films were used to measure the oxygen barrier properties of the functionalized material.

Bulk Polymerization Kinetics of Hydroxy Terminated Polybutadiene and Toluene Diisocyanate with Infrared Spectroscopy

A study on bulk polymerization kinetics of HTPB (Hydroxy Terminated Polybutadiene) and TDI (Toluene Diisocyanate) with infrared (IR) spectroscopy has been conducted. The investigations included the molar ratio of 2,4-TDI to 2,6-TDI isomers, the initial molar ratio of isocyanate group to a hydroxyl group, and the reaction temperature. The polymerization rate constant was calculated based on the decrease rate of TDI. Kinetics model had been evaluated through the following reaction steps: (1) 2,4-urethane production, (2) 2,6-urethane production, (3) the reaction between 2,4-urethane and the isocyanate group of 2,4-TDI, (4) the reaction between 2,4-urethane and the isocyanate group of 2,4-TDI, (5) the reaction between 2,6-urethane and isocyanate group of 2,4-TDI, and (6) the reaction between 2,6-urethane and the isocyanate group of 2,6-TDI. Those reaction steps were assumed to be the first order reaction with the reaction rate constants k1, k2, k3, k4, k5, and k6, respectively. The reaction rate constants obtained at molar ratio of 2,4-TDI to 2,6-TDI of 80:20, isocyanate group to hydroxyl group (RNCO/OH) initial molar ratio of 1:1, and reaction temperature of 40 °C were 6.2 × 10-5, 5.8 × 10-5, 3.1 × 10-5, 2.8 × 10-5, and 2.5 × 10-5 L.mole-1.min-1 for k1, k2, k3, k4, k5, and k6, respectively, with the activation energy of 1152, 952, 1001, 656, and 1001 kJ/mole for reaction (1)–(6), respectively. The results show that the polymerization reaction rate-determining step was the reaction of 2,6-urethane and isocyanate group of 2,6-TDI (reaction (6)).

Improvement of Method for Determination of Isocyanate Group Content in Polyurethane Prepolymer

This paper represents the improvement of method for determination of isocyanate group content in polyurethane prepolymer. Acetone-dibutylamine method and toluene-dibutylamine method were used separately to determine the isocyanate group content in polyurethane prepolymer. The –NCO content tested by the two methods were close. In the former method, 15-20 mL acetone was used as solvent and the titration end point was easy to confirm. While in the latter method, additional solvent (isopropanol) was used which causes environmental contamination.