Microencapsulation of oil soluble polyaspartic acid ester and isophorone diisocyanate and their application in self-healing anticorrosive epoxy resin

Isocyanate and amine solution are microencapsulated, respectively, via in situ polymerization to realize the self-healing function in epoxy matrix. First, the isophorone diisocyanate (IPDI) microcapsules prepared with different core/shell ratios, emulsifier dosages and emulsification rates are characterized by field emission scanning electron microscope (FE-SEM). They exhibit integral spherical shape when the core/shell ratio is 3:1 and emulsifier concentration is 2.52 wt %, and the diameter of IPDI microcapsules ranged from 2.66 μm to 11.25 μm is manufactured by adjusting emulsification rate over the range of 3000–9000 rpm. Besides, during the microencapsulation of polyaspartic acid ester (PAE), urea, tung oil, as well as aqueous isocyanate are proposed to improve the stability of PAE emulsion. SEM and FTIR results reveal that aqueous isocyanate can react with partial PAE and form polyurea (PU) layer to take protection effectively. Further, IPDI-PAE dual microcapsules are incorporated into epoxy coatings, the self-healing and anticorrosion performance of coatings with various amounts of microcapsules are investigated systematically. It was found that the degree of repair and anticorrosion are increased with increasing microcapsules loading, and the appropriate amount of microcapsules addition is 15 wt %, which corresponding to 93% repair efficiency. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48478.     

Preparation and characterization of polyurea/polyurethane double‐shell microcapsules containing butyl stearate through interfacial polymerization

Double‐shell microcapsules containing butyl stearate were prepared through interfacial polymerization. The outer shell is polyurea formed through polymerization of toluene‐2,4‐diisocyanate (TDI) and diethylene triamine, and the inner shell is polyurethane (PU) formed through polymerization of TDI and polypropylene glycol 2000 (PPG2000). Styrene maleic anhydride copolymer was used as emulsifier. The effects of core to monomer ratio and dosage of PPG2000 on core content and encapsulation efficiency of microcapsules were investigated. The core content has a maximum at core to monomer ratio of 3–4, and the encapsulation efficiency has a maximum value of 95% at core to monomer ratio of 2. The prepared microcapsules were smooth and compact and have an obvious latent heat of 85 J/g. The shell structure of microcapsules was polyurea and PU. The average diameter of the microcapsules was 1–5 μm. The stabilities of the double‐shell microcapsule, such as anti‐ethanol wash and antiheat properties are obviously improved than those of single‐shell microcapsule. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Encapsulation of ionic liquid BMIm[PF6] within polyurea microspheres

The encapsulation of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIm[PF₆]) in polyurea microspheres is demonstrated. This method is based on the encapsulation of ionic liquid within a polyurea shell by emulsification and interfacial polymerization of amine and isocyanate monomers. Emulsification of BMIm[PF₆] was performed in water or oil, enabling formation of two different BMIm[PF₆] polyurea microcapsules with different chemical features. While the BMIm[PF₆]-in-water emulsion enables the formation of BMIm[PF₆] polyurea microcapsules with regular aliphatic diamines, the BMIm[PF₆]-in-oil emulsion requires the utilization of a specific diamine functionalized with ionic liquid groups. The microcapsules were characterized by scanning electron microscopy, thermal gravimetric analysis, infrared and solid NMR.     

界面聚合聚脲/聚氨酯复合壳体香精微胶囊的制备及性能

以茉莉香精为芯材,以异氟尔酮二异氰酸酯（IPDI）分别与二乙烯三胺（DETA）、β-环糊精（β-CD）及β-CD/DETA反应物为壁材,采用界面聚合法制备了聚脲、聚氨酯、聚脲/聚氨酯3种不同结构壳体的香精微胶囊。探究了不同微胶囊壳体对微胶囊表观形貌、热稳定性、香精微胶囊缓释性的影响并通过动力学模型分析了香精扩散方式。结果表明,以β-CD/DETA制备的聚脲/聚氨酯复合壳体微胶囊成囊性优异,壳体致密完整,热稳定性和缓释性能最好,经其整理的纺织品可保持较浓香味90多天。3种香精微胶囊在100℃、120℃高温缓释数据均符合零级、一级、Ritger-Peppas及Higuchi动力学模型。聚脲/聚氨酯复合壳体Ritger-Peppas方程拟合后n值更加接近0.45,更符合Fick扩散,缓释性能更好。     

聚脲交联改性丙烯酸酯弹性乳液的制备与性能研究

为了在性能上对聚脲交联改性后的丙烯酸酯乳液(PUA)和纯丙乳液(以)进行比较,文章以丙酮为溶剂,通过端氨基聚醚和甲苯二异氰酸酯的缩合反应合成了端异氰酸酯基聚脲预聚物,由于丙酮与胺基的可逆缩合反应,降低了胺基与异氰酸酯基反应的活性,从而可以更好地控制反应速度,降低副反应的发生几率.聚脲预聚体经丙烯酸羟乙基酯双键封端制备了含有2个双键的聚氨酯脲大单体,以其为外交联剂,通过与甲基丙烯酸甲酯、丙烯酸丁酯的乳液共聚反应制备了聚氨酯脲改性的纯丙弹性乳液,对乳液涂膜进行了FT-IR,DSC和TGA的表征.研究表明:PUA涂膜比PA涂膜具有更好的热稳定性、机械性能、耐低温性以及耐溶剂性.     

Understanding the role of isocyanate dilution toward spraying of polyurea

An experimental study into the consequences of diluting isocyanate toward processing of polyurea has been reported. The effect of introducing increasing amount of propylene carbonate into a representative isocyanate precursor has been established. Viscosity‐blending index based equations were found to be more reliable toward prediction of isocyanate precursor‐propylene carbonate blend viscosity. Spraying of undiluted isocyanate precursor with amine formulations led to formation of “noodle‐like” fibrous product, irrespective of the type of chain extender being used. Diluting isocyanate with propylene carbonate (10% v/v), lowered the viscosity of the precursor from 85 to 48 mPa s (at 70 °C), and the resulting formulations could be effectively sprayed to form polyurea films with excellent mechanical properties. Dilution with propylene carbonate also increased the “tack free” time appreciably from ～1 to ～4 s, which directly reflects on the improved processability. Rheological studies were performed to quantify the activation energy associated with the isocyanate‐amine reaction for polyurea preparation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45869.     

Synthesis of isocyanate microcapsules as functional crosslinking agent for wood adhesive

ABSTRACT

In this study, controlled-release isocyanate microcapsules were synthesized as functional crosslinking to slowdown the rate of cross-linking reactions. The isocyanate microcapsules were prepared by In-situ polymerization with polymethylene polyphenyl polyisocyanates (PAPI) as core and Urea formaldehyde resin as shell in oil-in-water emulsions. The particle size distribution, chemical structure, morphology, activity, and stability of the microcapsules were comprehensively characterized. Finally, the microcapsules were applied in a wood adhesive to prepare water-resistant plywood. The results showed that the size of the microcapsules was around 100 μm, the active content of NCO was about 23.5%, and the core content was approximately 80%. Compared with the stability of the bulk isocyanate, the stability of the isocyanate in microcapsules was significantly improved in the wood adhesive system. Furthermore, the isocyanate microcapsules showed highly efficient in plywood at different time, which indicated that isocyanate microcapsules could be controllable released in plywood applications.     

Synthesis and characterization of a methacrylic polyelectrolyte capable of reacting with primary amines at room temperature in water

The synthesis of a water-soluble ionic methacrylate monomer containing a sodium 4-hydroxybenzenesulfonate reactive blocked isocyanate is described. The optimized synthetic procedure is fast and easy to use, yielding a monomer of high purity and in good yields. An investigation of the hydrolytic stability of this electrophilic reagent indicated that it could be stored under reasonable conditions. A polyelectrolyte exhibiting the pendant reactive functionalities as side groups was obtained by free-radical polymerization. The obtained polymer exhibited excellent reactivity toward a primary aliphatic amine in water at room temperature, supporting the possible use of this monomer in the bioconjugation area.     

Interfacial encapsulation of bio‐based benzoxazines in epoxy shells for temperature triggered healing

Successful application of interfacial engineering for the preparation of cross‐linked epoxy microspheres containing thermally polymerizable cardanol‐based benzoxazine (Bz‐C) monomer in the core is demonstrated. Bz‐C is facilely synthesized by Mannich type condensation of cardanol (a by‐product of cashew nut industry) and aniline with formaldehyde under solventless conditions. The encapsulation process relies on the preferential reaction of polydimethylsiloxane immiscible epoxy resin and amine‐based hardener to form a cross‐linked spherical shell at the interface. The microcapsule dimensions and core content could be tailored by modulating the operating parameters, particularly stirring speed and Bz‐C: epoxy ratio. Spherical microcapsules with a core content of ～37% were obtained when the reaction was carried out at 600 rpm, while maintaining the reaction medium at 70°C with Bz‐C: epoxy ratio of 2.3 : 1. The simplicity and versatility of the present methodology are the forte of this technique, which widens the scope for large‐scale application of benzoxazines in the field of temperature triggered healing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42832.     

Emulsion of polyurethane having thermosetting properties. II. Relation between the mechanical properties of film and the polyurethane structure

A self-emulsifiable polyurethane emulsion having thermosetting property was prepared by the following procedure: the polyurethane–urea–amine was first prepared by the reaction of diethylene–triamine with a prepolymer containing terminal isocyanate groups in a ketone solvent, and then the primary amino group in the polyurethane–urea–amine was reacted with epichlorohydrin. The mixture was neutralized with an aqueous acid, and finally the ketone solvent was removed by distillation in vacuo. In the polyurethane, polytetramethylene glycol (PTMG) was the base polymer functioning as the soft segment. The present paper reports the effects of the following variables on the mechanical properties of the film prepared from the polyurethane emulsion, i.e., the M _n of PTMG, the molar ratio of diethylene–triamine (DTA) to prepolymer containing terminal isocyanate groups, the structure of the isocyanate end group and the molar ratio of tolylene diisocyanate (TDI) with PTMG. The best elastomer property was realized when M_n of PTMG was 2000, TDI/PTMG molar ratio was 2.0, and prepolymer/DTA molar ratio was 0.85.     

热膨胀微胶囊的研究进展

综述了近年来热膨胀微胶囊的研究进展,重点介绍了配方组分、合成工艺对热膨胀微胶囊性能的影响,叙述了聚合单体、发泡剂、交联剂、分散稳定剂的选择,分别讨论了反应温度、水油比例、均化条件、搅拌速度合成工艺的选择,并综述了热膨胀微胶囊壳体接枝改性技术的研究进展,同时叙述了热膨胀微胶囊在复合材料、水泥、微流体等领域的应用.最后,对热膨胀微胶囊的发展前景及研究方向进行展望.     

基于聚天冬氨酸酯的磺酸盐型聚脲分散体的成与表征

以马来酸二丁酯（DBM）和己二胺（HDA）为原料,通过Michael加成反应合成了天冬氨酸酯二聚物（AE）;AE与己二异氰酸酯（HDI）反应制得含末端仲胺和乙内酰脲环的聚天冬氨酸酯聚脲低聚物（PAE）;以N-〖DK〗(2-氨基乙基)-2-氨基乙磺酸钠（AAS）为亲水单体,PAE、异佛尔酮二异氰酸酯（IPDI）、乙二胺（EDA）为原料,采用丙酮法合成了磺酸盐型聚脲分散体（PUD）。采用FT-IR表征了AE和PAE的结构;聚脲分散体的ζ电位处于-48～-58 mV之间,具有良好的稳定性;随着亲水单体含量的增加,分散体黏度增加,平均粒径减小;TEM结果显示分散体胶粒为大小不一的球形结构,呈多元分布;拉伸实验表明聚脲分散体胶膜断裂伸长率大于450%;邵氏硬度在40～50之间;TGA显示其起始分解温度约为200℃,至450℃聚合物基本分解完毕。     

Microencapsulated ammonium polyphosphate with boron‐modified phenolic resin

Ammonium polyphosphate (APP) was encapsulated with boron‐modified phenolic resin (BPF) by in situ polymerization with the goal of improving its hydrophobicity, thermal stability, and compatibility in polymers. The chemical and physical features of APP microcapsules were characterized by Fourier transform infrared, X‐ray photoelectron spectroscopy, scanning electron microscopy, inductively coupled plasma, and laser particle sizing. The hydrophobicity was assessed by the water contact angle. The residues from thermogravimetric analyzer and muffle burner were investigated. The results showed that the APP microcapsules with BPF shell had been achieved successfully. The shell encapsulation rate mainly depended on the amount of crosslinking agent when the ratio of APP/BPF was constant. The mean particle size increased and the particle size distribution became more narrow. The hydrophobicity of APP was improved and the improvement degree mainly depended on the amount and adding rate of crosslinking agent and the conditions of heat curing. A good thermal stability and high residue char rate at high temperature were noticed for APP microcapsules. It suggests that these microcapsules might be used as an intrinsic flame retardant. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43720.     

Development of thermoregulating textile materials with microencapsulated phase change materials (PCM). II. Preparation and application of PCM microcapsules

Melamine–formaldehyde microcapsules containing eicosane were prepared by in situ polymerization. The characterization of the microcapsules, including the particle size and size distribution, morphology, thermal properties, and stability, was carried out. The prepared microcapsules were added to polyester knit fabrics by a conventional pad–dry–cure process to develop thermoregulating textile materials. The morphology, thermal properties, and laundering properties of the treated fabrics were also investigated. The microcapsules were spherical and had melamine–formaldehyde shells containing eicosane. The microcapsules were strong enough to secure capsule stability under stirring in hot water and alkaline solutions. The heat storage capacity increased as the concentration of the microcapsules increased. The thermoregulating fabrics had heat storage capacities of 0.91–4.44 J/g, which depended on the concentration of the microcapsules. The treated fabrics retained 40% of their heat storage capacity after five launderings. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2005–2010, 2005     

Synthesis and Characterization of Polyurea Resin for Dielectric Coating Applications

In this article, polyurea coatings were synthesized by reaction between toluene diisocyanate, and polyether difunctional and trifunctional amines PO-1 and PO-2 by incorporating urea linkage. The isocyanate-terminated prepolymers formed were further reacted with short-chain amines as chain extender as well as curing agents. These resins were synthesized by varying the molar ratio of amines and isocyanate and keeping the molar ratio of other monomers constant. The presence of functional groups were determined using Fourier transform infrared spectroscopy. The thermal stability of polymers was determined using the thermogravimetric analysis and differential scanning calorimetry. The polymers were further tested for mechanical and electrical properties. It was observed that on increasing the hard segments in the polymer the electrical properties increase whereas elongation decrease. As isocyanate content increases, crosslinking increases resulting in improvement in dielectric properties. The maximum dielectric strength observed was 45 kV mm^?1 and dissipation factor was 0.068.     

Influence of MEOBiPA content on the properties of novel photoluminescent thermosensitive hydrogels

In order to establish a dual functional hydrogel, a special monomer, methacryloyloxy‐ethylene‐oxy‐carbonyl bis[4‐(phenyl‐isopropyl)phenyl]amine (MEOBiPA), was prepared from bis[4‐(phenyl‐isopropyl)phenyl]‐4‐cyanophenyl amine and 2‐hydroxyethyl methacrylate. Subsequently, a series of thermosensitive hydrogels was obtained through copolymerization of N‐isopropyl acrylamide (NIPAAm) with MEOBiPA by UV irradiation (named the NM series). The effect of MEOBiPA content on the swelling behavior, mechanical properties and drug release behavior of the hydrogels was further investigated. Results showed that the swelling ratios of the NM copolymeric hydrogels decreased from 4.73 to 1.74 g g^?1 when the MEOBiPA content in the hydrogel increased from 0.1 to 0.9 mol%. Both gel strength and crosslinking density of the NM hydrogels increased with increasing MEOBiPA. Conversely, the thermosensitive behavior of NM hydrogels significantly decreased upon increase of MEOBiPA content. Likewise, the caffeine release ratio also decreased from 70% to 25%. Notably, the intensity of photoluminescence increased with increasing MEOBiPA content in the hydrogels. Further, the corresponding copolymers of the hydrogels were prepared using free radical polymerization. The UV absorbance and photoluminescent behavior of the MEOBiPA, NIPAAm/MEOBiPA copolymeric hydrogels and their corresponding copolymers in different polar solvents were also investigated. © 2015 Society of Chemical Industry     

Designing of polyamidoamine-based polyurea microcapsules containing tung oil for anticorrosive coating applications

A novel method for the fabrication of robust polyurea microcapsules containing tung oil as a core material was developed for self-healing anticorrosive coating application. Well-distinct microcapsules with polyurea as a shell were prepared by reacting hexamethylene diisocyanate trimer with 0.0 G polyamidoamine (PAMAM) via interfacial polymerization technique. Fourier transform infrared spectroscopic analysis was performed to elucidate the chemical structure of microcapsules as well as to confirm successful encapsulation of core by the polyurea shell. Surface morphology, particle size, distribution of particle size, thermal, and mechanical properties of the prepared PAMAM-based polyurea microcapsules were compared with microcapsules that were prepared using diethylenetriamine (DETA) and triethylenetetramine (TETA). The prepared microcapsules were embedded with acrylic polyol-based polyurethane (PU) coatings to ensure anticorrosive performance. The immersion study of self-healing PU coatings loaded with 5% PAMAM-based polyurea microcapsules possesses satisfactory anticorrosive property under an accelerated corrosion process in 5% NaCl salt solution.     

Self-healing thermoset using encapsulated epoxy-amine healing chemistry

Self-healing was achieved with a dual-microcapsule epoxy-amine chemistry in thermoset epoxy. One capsule contained a modified aliphatic polyamine (EPIKURE 3274) while the second capsule contained a diluted epoxy monomer (EPON 815C). Amine microcapsules were prepared by vacuum infiltration of EPIKURE 3274 into hollow polymeric microcapsules. Epoxy microcapsules were prepared by an in situ polymerization method. Both types of capsules were incorporated into an epoxy matrix (EPON 828:DETA) and recovery of mode-I fracture toughness was measured using tapered-double-cantilever-beam (TDCB) specimens. The optimal mass ratio of amine: epoxy capsules was 4: 6 and an average healing efficiency of 91% was achieved with 7 wt% amine capsules and 10.5 wt% epoxy capsules. Long-term stability of the healing system was demonstrated for six months at ambient conditions. Thermal stability was investigated by post curing samples at 121 °C and assessing healing performance.     

Kinetics of isocyanate amine reactions

Development of polyurea-urethane and polyurea reaction injection molding (RIM) systems has created a need for kinetics of polyurea formation. Adiabatic batch reactions in solution were used to determine heats of reaction and relative reactivity of several aromatic amines and n-butanol with phenyl isocyanate (PI). In addition to comparing times required to reach 25, 50 and 75% conversion for both catalyzed and uncatalyzed reactions, n-th order models with Arrhenius rate constants were used to fit some of the exotherms. The reaction of 3,5-diethyl toluene (2,4 and 2,6)-diamine and PI could not be modeled due to unequal reactivity of the two amine groups. This unequal reactivity was studied using high performance liquid chromatography (HPLC) separation of the reaction products. The reactions of primary aliphatic amines and aromatic isocyanates were too rapid to be monitored in the batch apparatus. With a flow apparatus the reaction half time was estimated to be ～ 0.002 s.     

STRIPPING RATE OF PROPIONIC ACID FROM STYRENE-DIVINYLBENZENE COPOLYMERIC MICROCAPSULES WITH TRI-W-OCTYL AMINE AS CORE MATERIAL

ABSTRACT

The stripping rate of propionic acid from microcapsules containing tri-n-octyl amine was investigated using distilled water and aqueous NaOH as stripping solutions. The experiments were conducted at 303K. The stripping rate was found to be controlled by diffusion through porous microcapsule membrane and increased with an increase in the concentration of propionic acid in the microcapsules for each solution system. It was found that the stripping rates in aqueous NaOH solution system was higher than in distilled water at the same concentration of propionic acid in microcapsules. The experimental results in the NaOH solution system could be analyzed using a permeation model considering mass transfer accompanied by irreversible instantaneous neutralization reaction between NaOH and the propionic acid/tri-n-octyl amine complex in the microcapsule membrane.