• Asian-Australasian Journal of Animal Sciences
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• v.23 no.4
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• pp.491-500
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• 2010

Three experiments were conducted to investigate the effects of polyurethane coated urea on in vitro ruminal fermentation, ammonia release dynamics and lactating performance of Holstein dairy cows fed a steam-flaked corn-based diet. In Exp. 1, a dual-flow continuous culture was run to investigate the effect of polyurethane coated urea on nutrient digestibility, rumen fermentation parameters and microbial efficiency. Three treatment diets with isonitrogenous contents (13.0% CP) were prepared: i) feedgrade urea (FGU) diet; ii) polyurethane coated urea (PCU) diet; and iii) isolated soy protein (ISP) diet. Each of the diets consisted of 40% steam-flaked corn meal, 58.5% forages and 1.5% different sources of nitrogen. PCU and FGU diets had significantly lower digestibility of NDF and ADF (p<0.01) than the ISP diet. Nitrogen source had no significant effect (p = 0.62) on CP digestibility. The microbial efficiency (expressed as grams of microbial N/kg organic matter truly digested (OMTD)) in vitro of the PCU diet (13.0 g N/kg OMTD) was significantly higher than the FGU diet (11.3 g N/kg OMTD), but comparable with the ISP diet (14.7 g N/kg OMTD). Exp. 2, an in vitro ruminal fermentation experiment, was conducted to determine the ammonia release dynamics during an 8 h ruminal fermentation. Three treatment diets were based on steam-flaked corn diets commonly fed to lactating cows in China, in which FGU, PCU or soybean meal (SBM) was added to provide 10% of total dietary N. In vitro $NH_3-N$ concentrations were lower (p<0.05) for the PCU diet than the FGU diet, but similar to that for the SBM diet at all time points. In Exp. 3, a lactation trial was performed using 24 lactating Holstein cows to compare the lactating performance and blood urea nitrogen (BUN) concentrations when cows were fed PCU, FGU and SBM diets. Cows consuming the PCU diet had approximately 12.8% more (p = 0.02) dietary dry matter intake than those consuming the FGU diet. Cows fed the PCU diet had higher milk protein content (3.16% vs. 2.94%) and lower milk urea nitrogen (MUN) concentration (13.0 mg/dl vs. 14.4 mg/dl) than those fed the FGU diet. Blood urea nitrogen (BUN) concentration was significantly lower for cows fed the PCU (16.7 mg/dl) and SBM (16.4 mg/dl) diets than the FGU (18.7 mg/dl) diet. Cows fed the PCU diet had less surplus ruminal N than those fed the FGU diet and produced a comparable lactation performance to the SBM diet, suggesting that polyurethane coated urea can partially substitute soybean meal in the dairy cow diet without impairing lactation performance.

• Macromolecular Research
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• v.14 no.6
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• pp.634-639
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• 2006

Waterborne polyurethane (WBPU) adhesive with varying amounts of dimethylol propionic acid (DMPA) was synthesized by prepolymer process and blended with polyisocyanate hardener. The mean particle size of the WBPU dispersion decreased with increasing DMPA content. $^1H$ NMR spectroscopy confirmed the formation of allophanate bonds and biuret bonds due to the reaction of hardener NCO with urethane/urea groups. The optimum NCO content with the greatest adhesive strength was dependent on the total content of urethane/urea groups in the WBPU molecules. The optimum NCO content increased with increasing number of urethane groups (DMPA content). The adhesion strength of WBPU adhesives was maximized at a molar ratio of hardener NCO to urethane/urea of about 0.28.

• Journal of the Korean Wood Science and Technology
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• v.51 no.1
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• pp.14-22
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• 2023

Economical use of larix (larch) boards (grade 3) in industries is lower than that of imported hardwood; thus, studies have been conducted toward performance improvement of larix boards. Herein, flexural modulus of larix board samples laminated with wood adhesives polyurethane resins, poly (vinyl acetate) resins, phenol-resorcinol-formaldehyde resins, melamine-formaldehyde resins, and urea-formaldehyde resins was compared with that of the samples bonded with adhesives reinforced with mesh-type basalt fibers. Moreover, the flexural moduli of the laminated samples bonded by mesh-type basalt fibers were compared with those of reinforced samples. The results showed that boards laminated with polyurethane and urea-formaldehyde resin adhesives had higher flexural modulus than those without the lamination. In particular, the increase in the flexural modulus was relatively significant for the 2- and 3-ply board structures laminated with polyurethane adhesives compared to those with reinforcement. The 3-ply board structure without reinforcement had the highest flexural modulus when the urea-formaldehyde resin adhesive was used.

• Macromolecular Research
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• v.15 no.1
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• pp.22-30
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• 2007

High water vapor permeable coating materials were prepared by blending aqueous poly(vinyl alcohol) (PVA) solution with waterborne polyurethane-urea (WBPU) dispersions synthesized by prepolymer mixing process. Stable WBPU/PVA dispersions were achieved at PVA content below 30 wt%. As the water soluble polymer PVA content increased, the number and density of total micro-pores (tunnel-like/isolated micro-pores) formed after the dissolution of PVA in water increased, and the water vapor permeability of coated Nylon fabric also increased significantly. Using WBPU/water soluble polymer PVA blends as a coating material and then dissolving PVA in water was confirmed to be an effective method to obtain prominent breathable fabrics.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.540-544
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• 2011

Novel phosphrous flame retardant tetramethylene bis(orthophosphorylurea) (TBPU) was synthesized by the reaction of diphosphoric acid with 1,4-butanediol and urea, and charaterized by Fourier transform infrared spectroscopy (FT-IR). As the amount of TBPU added in polyurethane foam (PUF) was increased, the flame retardancy of PUF was increased and the mechanical properties were not decreased. Also, in the flame resistance test after the reduced pressure storage, the flame retardancy of TBPU added PUF was retained. We could find out that the thermal resistance of TBPU added PUF increased compared to that of pure PUF.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.41-48
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• 1993

An ISFET urea sensor was fabricated by immobilizing the urease using polyurethane on the $H^{+}$ sensing $Si_{3}N_{4}$ thin film of pH-ISFET. The sensor could determine the urea concentration $1{\sim}50$ mg/dl with fast response of $3{\sim}5$ min. and good repeatability. For its application to clinical analysis, the results of the urea measurements in blood plasma using ISFET urea sensor were compared with these of conventional Urease-Indophenol method.

• Journal of Biomedical Engineering Research
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• v.19 no.3
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• pp.215-224
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• 1998

This paper is fundamental study to develope the extracorporeal liver support system for patient with fulminant hepatic failure(FHF) or being expected for orthotopic liver transplantation. The polyurethane foam, which is composed of the density of 33kg/m3, the average pore diameter of 500${\mu}{\textrm}{m}$, the closed window of 60-70%, was manufactured with the prepolymer of 15% NCO-, Hepatocytes were inoculated to form spheroids in polyurethane foam. The time of spheroid formation in BSA(Bovine Serum Albumin) coated polyurethane foam was shorter than that in raw polyurethane foam. To verify the function of hepatocyte spheroids, we measured ammonia removal rate, urea and albumin secretion rate. Polyurethane foam was suitable for culture of hepatocyte spheroids. And culture of hepatocyte spheroids in polyurethane foam has high possibility in using as an extracorporeal liver support system.

• Elastomers and Composites
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• v.57 no.1
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• pp.13-19
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• 2022

Polycarbonate diol-based waterborne polyurethane (WPU) was prepared by prepolymer mixing process. The prepolymer mixture contained the polycarbonate diol, isophorone diisocyanate (IPDI), dimethylol propionic acid, triethylamine, and ethylenediamine (EDA). The NCO/OH ratio in the prepolymer was adjusted by controlling the molar ratio of IPDI, and its effects on the properties of WPU were studied. The structure of WPU was characterized by fourier transform infrared spectroscopy. The average particle size increased and viscosity decreased with increasing NCO/OH ratio and EDA content in WPU. The reduced phase separation between soft and hard segments increased glass transition temperature. The reduction in the thermal decomposition temperature could be attributed to the low bond energy of urethane and urea groups, which constituted the hard segment. Additionally, the polyurethane chain mobility was restricted, elongation decreased, and tensile strength increased. The hydrogen bond between the hard segments formed a dense structure that hindered water absorption.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.388-393
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• 1999

Polyurethane foams are polymeric material with repeating groups of urethane and urea. When these are heated with ethylene glycol and K acetate catalyst at $200^{\circ}C$, the transesterification of them leads to soluble products. The mechanisms of the reaction were investigated from the molecular weight and the component distributions of the products by GPC and IR analysis. The degradation of the urethane groups was faster than that of urea groups in transesterification reaction. K acetate catalyst accelerated the rate of the transesterification because it had a high ionization tendency. Each reaction, using K or Sr acetate as a catalyst, progressed in the same reaction path but yielded different compositions in products because of the difference of the reaction rate.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.57-63
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• 2017

In this study, we identified how the water content change in various NCO index affects the static comfort of polyurethane seat foam pad for automobiles. In order to identify factors that affect the static comfort, a static load test was performed using UTM to plot a hysteresis curve. The hardness of the foam when it was modified by 25, 65%, hysteresis loop area, hysteresis loss (%), and Sag factor were also obtained. By measuring the swelling ratio, it was confirmed that, as the water content increased in a fixed NCO index, the hardness and crosslinking density increased while the restoring force decreased due to the increase of urea bond. Also the Sag factor decreased due to the increase of surface hardness. As the NCO index increased in a fixed water content, the urethane and urea bond reacted more with isocyanate, leading to an increase in hardness and decrease in restoring force.