Scientia Agricultura Sinica ›› 2026, Vol. 59 ›› Issue (13): 2894-2905.doi: 10.3864/j.issn.0578-1752.2026.13.011

• SOIL & FERTILIZER·WATER-SAVING IRRIGATION·AGROECOLOGY & ENVIRONMENT • Previous Articles     Next Articles

Preparation and Application of Surfactant-Modified Castor Oil-Based Polyurethane-Coated Urea

LIAN SiRong1(), TANG JianWei1,2,3, WANG YongJie1, HUANG JingLong1, WANG ChengQian1, LI Rui1, MAO KeLu1, WANG Xu1, YUE YanJun4, LIU Yong2,3,5, WANG BaoMing1,2,3, LIU PengFei1()   

  1. 1 School of Ecology and Environment, Zhengzhou University, Zhengzhou 450001
    2 National Centre of Research & Popularization on Calcium, Magnesium, Phosphate and Compound Fertilizer Technology, Zhengzhou University, Zhengzhou 450001
    3 Research Centre of Engineering and Technology for Synergetic Control of Environmental Pollution and Carbon Emissions of Henan Province, Zhengzhou 450001
    4 Henan Xinlianxin Chemical Industry Group Co., Ltd, Xinxiang 453706, Henan
    5 School of Chemical Engineering, Zhengzhou University, Zhengzhou 450001
  • Received:2025-08-06 Accepted:2025-12-19 Online:2026-07-01 Published:2026-07-01
  • Contact: LIU PengFei

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Abstract:

【Objective】Surfactants affect the properties and controlled-release performance of coated fertilizers by influencing the structure of polyurethane film materials based on castor oil. This study offered a theoretical support for the practical use of surfactant-modified plant oil-based polyurethane coated urea in agriculture through a methodical examination of the properties of coated urea, surfactant-modified castor oil-based polyurethane film, and field tests. 【Method】Using surfactant modification, castor oil-based polyurethane-coated urea (BPCU) was created. The surfactant modification mechanism was examined, and FT-IR was used to corroborate the polyurethane synthesis. The effects of surfactants on the hydrophobic properties of membrane materials were investigated. In Zhaodi Village, Xinxiang, Henan Province, a field experiment was carried out using homemade slow-release fertilizer to reduce fertilizer application by 20% while using regular urea as the control. The impact of BPCU on summer maize yield was examined, and Zhongjinyu 2513 was the test crop. 【Result】By improving the compatibility of the polyurethane matrix and creating a pseudo-crosslinking effect, the surfactant could make the high hydroxyl value castor oil-based polyol and PM-200 more evenly distribution on the coating film's surface. Additionally, the cross-linking density was further enhanced by lowering the energy consumption of the interfacial reaction between the high hydroxyl value castor oil-based polyol and PM-200 to form polyurethane. The improved membrane material had a decreased residual carbon content, according to the results. The improved membrane shell's water contact angle was 105.5°, a 13.0 % increase from the unmodified membrane shell's 93.4°. The modified membrane material had a 7-day water absorption rate of 1.64%, a porosity of 1.14%, and a swelling degree of 1.18%. The 7-day water absorption rate, porosity, and swelling degree were all reduced by 76.8%, 76.7%, and 25.3%, respectively, when compared with the unmodified membrane material. The slow-release duration of BPCU was extended from 70 to 83 days at 0.5% surfactant addition, which was 18.6% longer than that of castor oil-based polyurethane-coated urea (PCU). With a 20% decrease and a 5% coating, the corn yield of the BPCU fertilizer was 11 908.1 kg·hm-2, a 22.0% increase over the maize yield of 9 757.2 kg·hm-2 following the application of regular urea. In contrast, the thousand-grain weight likewise rose by 16.9%. The yield and thousand-grain weight of maize were significantly impacted by the application of BPCU. It mostly influenced the thousand-grain weight of maize, which in turn impacted its yield. 【Conclusion】It was demonstrated from aspects such as nitrogen release period and summer maize yield that the performance of BPCU was superior to that of the unmodified PCU. The application of BPCU could be regarded as an effective way to reduce fertilizer application and increase efficiency. The creation of novel coated controlled-release fertilizers was supported theoretically and technically by this study.

Key words: coated fertilizer, surfactant, polyurethane, slow release, field experiment, summer maize

Fig. 1

The preparation process and schematic diagram of PCU and BPCU"

Table 1

Physical and chemical properties of soil"

pH
 NH4+-N
(mg·L-1)		 NO3--N
(mg·L-1)		 有效磷Available P
(mg·L-1)		 速效钾
Available K
(mg·L-1)		 交换性钙Exchangeable Ca
(mg·L-1)
8.6 9.9 19.1 39.2 143.8 2041.2

Fig. 2

GC chromatogram of castor oil"

Table 2

Types and relative content of fatty acids in castor oil"

脂肪酸 Fatty acid 脂肪酸简写 Abbreviation 保留时间 Retention time (min) 相对含量 Relative content (%)
棕榈酸 Palmitic acid C16:0 18.26 1.82
α-亚油酸 Alpha-linoleic acid C18:2 22.25 7.96
油酸 Oleic acid C18:1 22.37 8.73
反异油酸 Trans-isoleic acid C18:1 22.51 2.65
硬脂酸 Stearic acid C18:0 22.94 4.09
亚油酸 Linoleic acid C18:1 23.40 0.34
亚麻酸 Linolenic acid C18:3 24.17 2.68
二十碳烯酸 Eicosenoic acid C20:1 24.98 4.56
蓖麻油酸 Ricinoleic acid C18:1 25.92 63.74
9,10-二羟基硬脂酸 9,10-Dihydroxystearic acid C18:1 27.02 3.43
蓖麻油酸 Ricinoleic acid C18:1 25.92 63.74
9,10-二羟基硬脂酸 9,10-Dihydroxystearic acid C18:1 27.02 3.43

Fig. 3

Infrared spectra of CO (a), GI (b), and COP (c)"

Fig. 4

Infrared spectra of COP (a), PM-200 (b), castor oil- based polyurethanes (c) and castor oil-based polyurethane coupling surfactants (d)"

Fig. 5

Morphology of PCU (a, c) and BPCU (b, d) membrane surface"

Fig. 6

TG-DTG diagrams of PCU (a) and BPCU (b) shells"

Fig. 7

Effect of surfactant addition on water absorption of membrane material"

Fig. 8

Effect of surfactant addition on porosity and swelling degree of membrane materials"

Fig. 9

Influence of surfactant addition on slow-release performance of BPCU"

Fig. 10

Effect of GI addition on slow-release performance of BPCU"

Fig. 11

Influence of castor oil-based polyol content on slow- release performance of BPCU"

Table 3

Effects of different fertilization treatments on summer maize yield"

处理
Treatment		 穗粒数
Number of grains in a spike		 千粒重
Thousand grain weight (g)		 产量
Yield (kg·hm-2)
普通尿素 Common urea 549.25±38.33a 286.84±10.47b 9757.16±19.45b
自制控释尿素 Self-made controlled release urea 525.5±25.57a 335.40±11.91a 11908.07±23.74a
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