Diisocyanate Compounds Research Articles

Controlling the Synthesis of Polyurea Microcapsules and the Encapsulation of Active Diisocyanate Compounds.

The encapsulation of active components is currently used as common methodology for the insertion of additional functions like self-healing properties on a polymeric matrix. Among the different approaches, polyurea microcapsules are used in different applications. The design of polyurea microcapsules (MCs) containing active diisocyanate compounds, namely isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HDI), is explored in the present work. The polyurea shell of MCs is formed through the interfacial polymerization of oil-in-water emulsions between the highly active methylene diphenyl diisocyanate (MDI) and diethylenetriamine (DETA), while the cores of MCs contain, apart from IPDI or HDI, a liquid Novolac resin. The hydroxyl functionalities of the resin were either unprotected (Novolac resin), partially protected (Benzyl Novolac resin) or fully protected (Acetyl Novolac resin). It has been found that the formation of MCs is controlled by the MDI/DETA ratio, while the shape and size of MCs depends on the homogenization rate applied for emulsification. The encapsulated active compound, as determined through the titration of isocyanate (NCO) groups, was found to decrease with the hydroxyl functionality content of the Novolac resin used, indicating a reaction between NCO and the hydroxyl groups. Through the thorough investigation of the organic phase, the rapid reaction (within a few minutes) of MDI with the unprotected Novolac resin was revealed, while a gradual decrease in the NCO groups (within two months) has been observed through the evolution of the Attenuated Total Reflectance-Fourier-Transform Infrared (ATR-FTIR) spectroscopy and titration, due to the reaction of these groups with the hydroxyl functionalities of unprotected and partially protected Novolac resin. Over longer times (above two months), the reaction of the remaining NCO groups with humidity was evidenced, especially when the fully protected Acetyl Novolac resin was used. HDI was found to be more susceptible to reactions, as compared with IPDI.

Investigating the potential of dihydroxystearic acid as feedstock for rigid polyurethane foam

Rigid polyurethane (PU) foam has been widely used for a multitude of applications, primarily as thermal insulation materials. With the exhortation of “green chemistry” and sustainable development, bio-based polyols are being introduced to replace the conventional petrochemical-based polyols. Hence, the use of 9, 10-dihydroxystearic acid (DHSA), derived from palm oil-based oleic acid, as a feedstock for rigid PU foam production was explored. In this study, the effects of the weight ratio percentage of DHSA on the characteristics of the resulting PU foams were investigated. The DHSA was utilized as a co-polyol to synthesize rigid PU foams by reacting with the diisocyanate compound, blowing agent and additives. In general, the effects of DHSA in the formulations on the quality of the foams were relatively similar to PU formulation without the addition of DHSA, particularly in terms of density, compressive strength, thermal conductivity, cell structure and dimensional stability. The remarkable effect of DHSA addition in the PU formulations was observed through the open PU cell content using a pycnometer and scanning electron microscopy (SEM). The addition of DHSA has the ability to open the cell structure of the resulting rigid PU foams. The open cell content increased notably from 6.83% to 90.99% when the DHSA content was increased from 0% to 50%. The ability of DHSA to produce open-cell rigid PU foam widens up the potential applications of rigid PU foams as sound absorption materials.

Preparation and environmental analysis of biodegradable polylactic acid and modified cellulose nanofiber composites

Polylactic acid (PLA) and cellulose nanofibers (CNFs) show promise as bio-based alternatives to non-degradable plastics, which pose environmental challenges. Yet, CNFs' hydrophilicity hampers their dispersion in hydrophobic PLA. This study modifies CNF surfaces with diisocyanate compounds to create hydrophobic isocyanate-modified CNFs (mCNFs), enhancing their compatibility with PLA. One isocyanate of the diisocyanate compound is grafted onto the surface of CNF and the isocyanate content varied by adjusting grafting reaction time. PLA-mCNF composites are produced by a twin-screw extruder and show improved mechanical properties and biodegradability compared to pristine PLA and PLA-unmodified CNF composite. The environmental impacts of PLA-mCNF composites are evaluated using a life-cycle assessment method and compared to corn grain-based PLA. The optimized PLA-mCNF composite (6 h of grafting reaction) has lower environmental impacts than corn grain-based PLA, with global warming and fossil resource scarcity of 3.021 kg eq and 0.813 kg oil eq, respectively. This study underscores the feasibility of optimizing PLA composite properties by employing a small proportion of toxic diisocyanate on CNF surfaces. The findings highlight the potential of such modified composites to offer improved sustainability and performance characteristics, contributing to the development of eco-friendly materials.

An alternative strategy for the synthesis of disazo disperse dyes and their application on polyester fabric

Due to the limitations of dye solubility in reaction solvents, the crosslinking reaction between two monoazo disperse dyes will tend to result in low yield and multiple by-products. In this work, an alternative synthetic strategy was used to prepare three disazo disperse dyes, which involved first synthesizing crosslinked coupling components with diisocyanate compounds followed by diazotization with a double diazonium salt. The structures of these new dyes were characterized by nuclear magnetic resonance (NMR), mass spectrometry (MS), and fourier transform infrared spectroscopy (FT-IR) analysis, and the spectral characteristics of the dyes in dimethylformamide (DMF) solutions were evaluated. Three synthesized disazo dyes were applied to the polyester fabrics by high-temperature and hot-melt dyeing processes. The results showed that a higher yield was obtained for all three dyes, and each of the dyes had relatively high molar extinction coefficient and slow dyeing rate on the polyester fabric due to the existence of the double-chromophore. Therefore, a certain amount of carrier or solubilizer had to be added to the dyebath to improve the dyeing rate. At 220 °C for 2.5 min, a satisfactory dyeing effect was achieved, which demonstrated that the disazo disperse dyes exhibited excellent colorfastness properties. Compared with high-temperature dyeing, thermosol dyeing produced higher dye uptake, build-up, and fastness properties, and this process was suitable for the dyeing of polyester fabrics with the disazo disperse dyes.

Alkynyl-functionalized chain-extended PCL for coupling to biological molecules

Chemical functionalization of poly(ε-caprolactone) (PCL) enables a molecular integration of additional function. Here, we report an approach to incorporate reactive alkynyl side-groups by synthesizing a chain-extended PCL, where the reactive site is introduced through the covalently functionalizable chain extender 3-(prop-2-yn-1-yloxy)propane-1,2-diol (YPD). Chain-extended PCL with Mw of 101 to 385 kg·mol−1 were successfully synthesized in a one-pot reaction from PCL-diols with various molar masses, L-lysine ethyl ester diisocyanate (LDI) or trimethyl(hexamethylene)diisocyanate (TMDI), and YPD, in which the density of functionalizable groups and spacing between them can be controlled by the composition of the polymer. The employed diisocyanate compounds and YPD possess an asymmetric structure and form a non-crystallizable segment leaving the PCL crystallites to dominate the material’s mechanical properties. The mixed glass transition temperature Tg = −60 to −46 °C of the PCL/polyurethane amorphous phase maintains the synthesized materials in a highly elastic state at ambient and physiological conditions. Reaction conditions for covalent attachment in copper(I)-catalyzed azide-alkyne-cycloaddition reactions (CuAAC) in solution were optimized in a series of model reactions between the alkyne moieties of the chain-extended PCL and benzyl azide, reaching conversions over 95% of the alkyne moieties and with yields of up to 94% for the purified functionalized PCL. This methodology was applied for reaction with the azide-functionalized cell adhesion peptide GRGDS. The required modification of the peptide provides selectivity in the coupling reactions. The obtained results suggest that YPD could potentially be employed as versatile molecular unit for the creation of a variety of functionalizable polyesters as well as polyurethanes and polycarbonates offering efficient and selective click-reactions.

Hydrothermal Synthesis of Polyoxometalate Containing Cobalt Ion, and Its Polyurethane Composites for Dielectric Material Applications

ABSTRACT Polyurethane (PU) composites were prepared with different diisocyanate and diol compounds by adding cobalt ion-based polyoxometalate (Co-POM) as reinforcement. For the determination of using potential in microelectronic applications, the dielectric behavior and dielectric constant of these PU composites were investigated and compared to pure polyurethane structures. For this aim, firstly, Co-POM with Keggin structure was obtained from ammonium heptamolybdate, 1,10-phenanthroline ligand and a cobalt (II) salt by hydrothermal synthesis technique. Then, polyurethane/Co-POM composites (PU/Co-POM) were prepared with ethylene glycol, nonaromatic diisocyanate and different amounts of Co-POM reinforcement (1%, 3%, 5% and 10%, w/w) by in situ polymerization and mix-blend technique. Obtained PU/Co-POM composites were characterized in detail by infrared spectroscopy, Elemental Mapping, Energy-dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD) spectroscopy. The surface structure, morphology and roughness of PU/Co-POM composites were investigated by SEM and AFM analysis. The elemental maps of the PU/Co-POM surface were examined by EDX elemental mapping analysis methods. Thermal stability, Tg values and thermal decomposition temperatures of PU/Co-POM structures were determined by different thermal analysis techniques. Thermal analysis results showed that the PU/Co-POM composites are thermally stable up to approximately 200°C and Tg values of synthesized PU composites are seen between 54.72°C and 75.15°C. The dielectric properties and dielectric constants of the PU/Co-POM composites were determined in the frequency range 1 Hz to 1000 kHz at room temperature using impedance analyzer. Dielectric constants of these composites were ranged from 5.50 to 9.26 according to their polarizability and H-bonding ability of PU matrix structure. According to the dielectric measurements, the dielectric constants of the PU/Co-POM structures were significantly decreased compared to the pure PU structures.

Synthesis and Properties of Organic-Inorganic Hybrid Porous Polymers Obtained with Click Addition Reactions of Thiol-Functionalized Random Type Silsesquioxane by and Diacrylate or Diisocyanate Compounds

Organic-inorganic hybrid network polymers have been synthesized by addition reaction of a thiol-functionalized random type silsesquioxane (SQ109) and alkyl diacrylate or diisocyanate compounds. Thiol-ene reaction of SQ109 and 1,4-butanediol diacrylate (BDA) successfully yield porous polymer in toluene initiated by azobis(isobutyronitrile) (AIBN) at 60°C. Morphology of the porous polymers was composed by connected globules, and the diameter of the globules decreased with increasing in the monomer concentration of the reaction system. By contrast, the reaction with 1,6-hexanediol diacrylate or 1,5-hexadiene yielded homogeneous clear gels. Thermal analyses of SQ109-BDA porous polymers indicated that thermal degradation of ester groups of BDA in the polymer network occurred at around 300°C. The porous polymer was also obtained by the reaction using a photo-initiator (Irugacure184) at room temperature, and showed higher Young’s modulus than the corresponding porous polymer obtained with the reaction with AIBN due to the small size of the globules. Young’s modulus of SQ109-BDA porous polymer increased with increasing in the monomer concentration of the reaction systems. Thiolisocyanate addition reactions between SQ109 and hexamethylene diisocyanate (HDI) or methylenediphenyl 4,4’-diisocyanate (MDI) were investigated to obtain network polymers. The reactions in toluene yielded the corresponding homogeneous clear gels. By contrast the reactions in a mixed solvent of toluene (50 vol.%) and N,N-dimethylformamide (50 vol.%) produced porous polymers. The morphology of the porous polymers was composed by connected globules or aggregated particles. The size of globules and particles in the SQ109-HDI porous polymers was larger than those in the SQ109-MDI porous polymers. Thermal degradation of SQ109-HDI and SQ109-MDI porous polymers started at round 260°C and showed endothermic peak at around 350°C derived from degradation of thio-urethane bond.

Novel biologically active polyurea derivatives and its TiO2-doped nanocomposites

ABSTRACT A new series of polyurea derivatives and its nanocomposites were synthesised by the solution polycondensation method through the interaction between 4(2-aminothiazol-4-ylbenzylidene)-4-(tert-butyl) cyclohexanone and diisocyanate compound in pyridine. The PU1–3 structure was confirmed using Fourier transform-infrared (FTIR) spectroscopy and characterised by solubility, viscometry, gel permeation chromatography (GPC), and X-ray diffraction (XRD) analysis. In addition, PU1–3 was evaluated by TGA. Polyurea–TiO2nanocomposites were synthesised using the same technique as that of PU1–3 by adding TiO2 as a nanofiller. The thermal properties of PU2TiO2a–d were evaluated by TGA. Moreover, the morphological properties of a selected sample were examined by SEM and TEM. In addition, PU1–3 and PU2TiO2a–d were examined for antimicrobial activity against certain bacteria and fungi. The PU1–3 showed antibacterial activity against some of the tested bacteria and fungi, as did PU2TiO2a–d, which increased with the increase in TiO2 content. Furthermore, molecular docking studies were displayed against all PU1–3 derivatives against two types of proteins. The results show that the increase in the strength of π–H interactions and H-donors contributed to improved binding of PU2 compared to PU1 andPU3. The docking of 1KZN against the tested polymers suggests an increase in the docking score of PU2, then PU1, and PU3, which is in agreement with the antibacterial study.

A validated liquid chromatography/tandem mass spectrometry method for 4,4'-methylenedianiline quantitation in human urine as a measure of 4,4'-methylene diphenyl diisocyanate exposure.

4,4'-Methylene diphenyl diisocyanate (MDI) is a highly reactive isocyanate used in the production of polyurethanes. Workers exposed to these products may develop sensitization to the diisocyanate compounds, leading to occupational asthma. Quantifying MDI levels is necessary to ensure workplace safety. MDI is metabolized by acetylation and/or conjugation to macromolecules for excretion into urine. All metabolites can be chemically hydrolyzed to form the free diamine 4,4'-methylenedianiline (MDA) as a urinary biomarker of MDI exposure. Current methods involve long sample preparation, or have been designed using costly automation. There is therefore a need to develop a new practical method for assessing exposure to MDI. Urine samples were acidified and heated to form MDA, followed by neutralization and liquid-liquid extraction. Extracts were separated by reversed-phase chromatography on a HSS T3 column followed by analysis on a triple quadrupole mass spectrometer in multiple reaction monitoring (MRM) mode. 13 C15 N-MDA was selected as the internal standard (IS) of choice following an investigation of internal standard stability. The hydrolysis efficiency, forming free MDA from conjugated metabolites in vivo, was evaluated using 4,4'-methylenebis(acetanilide) spiked into urine and complete hydrolysis occurred after 1 h. A dynamic range of 5 to 500 nM was achieved, and was useful for monitoring MDI exposure considering the biological guidance value (BGV) of 10 μg/L (~50 nM) proposed by the German Research Foundation (DFG). The limit of detection (LOD) and limit of quantification (LOQ) of the method were 0.8 and 2.7 nM, respectively. The intra-day and inter-day precisions were 4.33% and 4.27%, respectively. Finally, the method was tested with inter-laboratory samples from the German External Quality Assessment Scheme (G-EQUAS) program and the results submitted were all within the allowable tolerance range. A practical and validated method for the analysis of small- to medium-sized batches of samples has been developed for the biological monitoring of MDI exposure in human urine.

Functionalization of Cellulose through Polyurethanization by the Addition of Polyethylene Glycol and Diisocyanate

Plastic consumption becomes a main factor of land pollution due to poor degradability. To reduce the impact of land pollution, a biodegradable material such as cellulose, which has biodegradability, high strength, and specific modulus, is combined with plastic materials. However, the combination result poor compatibility because of different properties. Through grafting technique, the compatibility can be improved. The experimental results were conducted using Fourier-Transform Infrared (FT-IR), Simultaneous Thermal Analysis (STA), Scanning Electron Microscope (SEM) and 1H-Nuclear Magnetic Resonance (1H-NMR). The results revealed that the structure of hybrid material consists of cellulose as a chain extender in a hard segment which connects two diisocyanate compounds and polyol as a soft segment. The addition of 2.5 g of cellulose and 5 mole of diisocyanate can increase the melting temperature (Tm) of the hard segment from 417.92 to 460.72 °C and from 417.92 to 467.04 °C respectively. However, its melting temperatures of soft segment decrease from 378.53 to 350.74 °C and from 378.53 to 350.74 °C as well as the glass transition temperature (Tg) of the soft segment from 73.7 to 57.2 °C and from 73.7 to 71.8 °C. This study also discovers that cellulose and diisocyanate can raise thermal stability and create good interfacial bonding.

Synthesis of joint-linker type gels and porous polymers by addition reactions of multi-functional thiol and alkyl diacrylate, diisocyanate compounds

Joint-linker type gels and porous polymers have been synthesized by addition reaction of multi-functional thiol and alkyl diacrylate or diisocyanate compounds. The reaction of multi-functional thiol, 1,3,5-tris(3-mercaptobutyloxethyl)-1,3,5-triazine-2,4,6- (1H,3H,5H)-trione (3T) or pentaerythritol tetrakis(3-mercaptobutylate) (PTMB), as joint molecule, and alkyl diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, as linker molecule in toluene successfully yield the corresponding gels. Network structure of the gels was quantitatively characterized by means of a scanning microscopic light scattering. The obtained gels formed homogeneous network structure with 1.2–2.0 nm of mesh. Mechanical properties of the gels were investigated by compression test. Increasing of the monomer concentration increased Young’s modulus and breaking stress of the gels. The gels composed of PTMB showed high Young’s modulus and breaking stress than the gels composed of 3T. The gels were also prepared in propylene carbonate or dimethyl sulfoxide (DMSO), and the gels prepared in DMSO showed high Young’s modulus. The addition reaction of 3T or PTMB and diisocyanate compound, hexamethylene diisocyanate (HDI) or 1,12-diisocyanatododecane (DDI), in toluene yielded porous polymers induced by phase separation during the polymerization. The porous structure was formed by connected globules about 5–10 μm diameter. The reactions of 3T, PTMB with HDI, DDI in tetrahydrofuran (THF) or N,N’-dimethylformamide (DMF) yielded transparent gels, and the gels prepared in DMF showed higher Young’s modulus than those prepared in THF.

Isophorone Diisocyanate (IPDI) Microencapsulation for Mono-Component Adhesives: Effect of the Active H and NCO Sources.

Polyurea/polyurethane (PUa/PU) shell microcapsules (MCs), containing high loadings of isophorone diisocyanate (IPDI) in the core, were developed to enable the production of mono-component, eco-friendly and safer adhesive formulations for the footwear industry. IPDI microencapsulation was obtained via oil–in–water (O/W) microemulsion combined with interfacial polymerization. A methylene diphenyl diisocyanate (MDI) compound (a commercial blend of monomeric and polymeric species), with higher reactivity than IPDI and low viscosity, was added to the O phase to competitively contribute to the shell formation, improving its quality. Four different active H sources were tested, aimed at achieving a high encapsulation yield. The successful encapsulation of IPDI was confirmed by Fourier transformed infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), while the MCs’ morphology and size distribution were assessed by scanning electron microscopy (SEM). The incorporation of a multifunctional isocyanate silane in the O phase, as “latent” active H source, led to the formation of impermeable PUa/PU-silica hybrid shell MCs with more than 60 wt.% of pure encapsulated IPDI. A proof-of-concept study shows high peeling strength and a structural type of failure of the adhesive joint, revealing an effective IPDI release. These new engineered MCs are found to be promising crosslinkers for mono-component adhesives for high demanding applications.

Novel route of synthesis for cellulose fiber-based hybrid polyurethane

Polyurethanes, obtained by the reaction of a diisocyanate compound with bifunctional or multifunctional reagent such as diols or polyols, have been studied intensively and well developed. The wide range modifier such as chemical structures and molecular weight to build polyurethanes led to designs of materials that may easily meet the functional product demand and to the extraordinary spreading of these materials in market. Properties of the obtained polymer are related to the chemical structure of polyurethane backbone. A number polyurethanes prepared from biomass-based monomers have been reported. Cellulose fiber, as a biomass material is containing abundant hydroxyl, promising material as chain extender for building hybrid polyurethanes. In previous researches, cellulose fiber was used as filler in synthesis of polyurethane composites. This paper reported a novel route of hybrid polyurethane synthesis, which a cellulose fiber was used as chain extender. The experiment performed by reacting 4,4’-Methylenebis (cyclohexyl isocyanate) (HMDI) and polyethylene glycol with variation of molecular weight to obtained pre-polyurethane, continued by adding micro fiber cellulose (MFC) with variation of type and composition in the mixture. The experiment was evaluated by NMR, FTIR, SEM and STA measurement. NMR and FTIR confirmed the reaction of the hybrid polyurethane. STA showed hybrid polyurethane has good thermal stability. SEM showed good distribution and dispersion of sorghum-based MFC.

Robot Assisted Polyurethane Chain Extension of Dihydroxy Telechelic Depsipeptides

ABSTRACTDepsipeptide-based multiblock copolymers synthesized from dihydroxy telechelic oligodepsipeptide precursors are promising candidate materials for biomedical and pharmaceutical applications. High molecular weight polymers in polyaddition reactions e.g. of diols with diisocyanates can only be reached when reactive groups are equivalent and a high conversion for this step growth polymerization is obtained. However, in depsipeptide-based multiblock urethanes reported so far, the stoichiometric ratio of the diisocyanate compound exceeded the theoretical value of 100% by far. In order to investigate the influence of the dosing system in this unusual behavior of the stoichiometric reaction two dosing devices, a solid dosing unit (SDU) and a gravimetric dosing unit (GDU) were used for a gravimetric transfer of an oligo(3-sec-butylmorpholine-2.5-dione) (OBMD) as model oligodepsipeptide. The OBMD precursor, which was transferred as a solid or as a highly viscous solution, was reacted with an isomeric mixture of 2,2,4- and 2,4,4-trimethylhexamethylene diisocyanate (TMDI) as chain extender. Two series of 49 reactions were performed and the chain extension efficacy of the building block was compared between the SDU and GDU as well as with respect to the Carothers equation. When the GDU was used the chain extension yielded higher molecular weights, proving the high accuracy of the dosing device, and the molar ratio of TMDI required for the high-throughput synthesis of the depsipeptide-based multiblock copolymers was similar to depsipeptide-based multiblock copolymers created in a classical synthesis approach.

Degradation behaviour of PLA-based polyesterurethanes under abiotic and biotic environments

Study was conducted on the degradation of polyurethanes based on Poly(lactic acid)/Poly(ethylene glycol), containing three differing concentrations of di-isocyanate compound, under three conditions (hydrolytic, thermal and composting). In the hydrolysis study, the effect of temperature and time were studied by techniques including weighting and GPC. Thermal decomposition was examined by thermogravimetry and mass spectroscopy. Composting was performed under standardized conditions and the amount of CO2 was measured. It was found that hydrolysis of the material started almost immediately after exposure to a water environment at both investigated temperatures (37 °C and 55 °C), whereas weight loss exhibited a certain delay. Thermal decomposition of the studied materials started below 230 °C and lactide was identified as the main product. A biodegradation experiment showed that all the investigated samples successfully (>80%) mineralized within 90 days under composting conditions.

Synthesis and characterization of polyurethane based on hydroxyl terminated polybutadiene and reinforced by carbon nanotubes

Nanocomposites consisting of multi wall carbon wall carbon nano tubes MWCNT/polyurethane (PU) had been successfully prepared based on hydroxy terminated polybutadiene HTPB and the prepared MWCNT. The effect of concentration of prepared MWCNT and surface modified CNT on the morphology, mechanical reinforcement, and thermal properties of PU-based composites had been evaluated by FESEM, tensile testing, thermo gravimetric analysis TGA and differential scanning calorimeter DSC.Polyurethane (PU) networks based on hydroxyl terminated polybutadiene (HTPB) and isophorone diisocyanate (IPDI) compound were prepared by a batch process. Two methods had been used to fabricate PU matrix/carbon nanotube nanocomposites: direct incorporation of unfunctional CNT (UCNT) into polymer matrices (noncovalent attachment) and in situ polymerization at their surface (covalent attachment).TGA showed a much better improvement of thermal stability of the composites than pure PU. Glass temperature (Tg) increased due to high interaction of CNT with PU. Also Young’s modulus increased. FESEM gave that the covalent attachment was better than noncovalent attachment for preparing PU/CNT composites.

Isophorone Diisocyanate 함유 마이크로캡슐의 제조와 자기치유형 보호코팅재에의 응용

본 연구의 목적은 다이이소시아네이트 화합물을 함유하는 마이크로캡슐을 제조하고 자기치유형 보호코팅재에 적용하여 공기 중 수분에 의한 자기치유 기능을 평가하는 것이다. 다이이소시아네이트 화합물의 공기 중 수분과의 반응 거동을 조사함으로써 치유 물질로서의 가능성을 확인하였다. 폴리우레탄을 캡슐막으로 하여 이소포론 다이이소시아네이트(isophorone diisocyanate, IPDI)의 마이크로캡슐화를 계면중합법에 의해 수행하였다. 마이크로캡슐의 생성여부는 FTIR 및 NMR으로 확인하였고, 마이크로캡슐의 직경 및 크기 분포, 표면 형상과 캡슐막의 두께는 광학현미경과 FE-SEM을 통하여 관찰하였다. 교반속도 및 다이올 구조 변화에 따른 마이크로캡슐의 특성 변화를 조사하였다. 자기치유형 보호코팅재를 제조하여 스크래치를 형성시킨 후 광학현미경으로 관찰한 결과, 스크래치 형성 직후 스크래치가 지나가는 자리에 위치하는 마이크로캡슐이 깨지면서 심물질이 흘러나와 스크래치를 메워주는 것을 확인하였다. 또한 CRC 보드에 마이크로캡슐을 함유한 자기치유 코팅재를 제조하여 스크래치 형성 후 상대습도 68~89%의 공기 중에 48시간 동안 방치한 후 SEM 분석 및 내투수 테스트를 진행한 결과, 스크래치가 자기치유된 것이 확인되었다. The object of this study is to prepare microcapsules containing a diisocyanate compound, apply them to self-healing protective coating, and evaluate the self-healing capability of the coating by atmospheric moisture. Isophorone diisocyanate (IPDI) polymerized under humid atmosphere, indicating that IPDI can be used as a healing agent. Microencapsulations of IPDI were conducted via interfacial polymerization of a polyurethane prepolymer with diol compounds. The formation of microcapsules was confirmed by Fourier-transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The mean diameter, size distribution, morphology and shell wall thickness of microcapsules were investigated by optical microscopy and scanning electron microscopy (SEM). The properties of microcapsules were studied by varying agitation rates and diol structure. The self-healing coatings were prepared on test pieces of CRC board. When scratch was generated in the coatings, the core material flew out of the microcapsules and filled the scratch. The self-healing coatings were damaged and healed under atmosphere with 68~89% relative humidity for 48 h, and SEM and impermeability test for the specimens showed that the scratch could be healed by atmospheric moisture.

Examination of the Aging Effects of Silicone Molds During Vacuum Casting Processes via Scanning Electron Microscopy

We present an in-depth investigation of contaminated silicone molds by use of scanning electron microscopy, that provides additional insight into the aging process of the molds. The molds lifetime in vacuum casting processes of polyurethane is limited due to contamination with the diisocyanate compound of the PUR resin. SEM investigations, combined with FIB cross-sections and EDX measurements show that three different types of particles are distributed in the contaminated silicone matrix. The particles differ in shape and size, with a range from 50 nm to 50 µm. This explains the loss in transparency and the hardened haptics of contaminated molds.

Insertion Metathesis Depolymerization of Aromatic Disulfide-containing Dynamic Covalent Polymers under Weak Intensity Photoirradiation

Abstract Aromatic disulfide bonds become dynamic in a radical process under weak intensity photoirradiation and can undergo metathesis. Aryl disulfide-containing dynamic covalent polyurethanes were prepared by the polyaddition of disulfide-containing diol and diisocyanate compounds. To determine the dynamic nature of the aryl disulfide-containing polymers, insertion metathesis depolymerization was performed under weak intensity photoirradiation at room temperature. The molecular weights of the dynamic covalent polymers decreased as the irradiation time increased.

Preparation of high molecular weight and elastic copolyester by reactive extrusion with diisocyanate compound for laser printing process

Abstract A branched copolyester was synthesized using dimethyl terephthalate (DMT), 2,2-bis[4-(2-hydroxypropoxy)phenyl]propane, ethylene glycol (EG) and 2-(hydroxymethyl)-2- ethylpropane-1,3-diol (trimethylol propane, TMP). The branched copolyester and p-phenylene diisocyanate (PPDI) were melt extruded to enhance the melt viscosity and elasticity for use as a toner binder in the laser printing process. The effects of PPDI content on melt, thermal and rheological properties of the chain-extended copolyester were investigated. The melt flow index (MI) decreased with increasing amount of PPDI, due to a reaction between the hydroxyl chain end and isocyanate group. The storage modulus, loss modulus and complex viscosity of the chain extended copolyester were higher and the modified Cole-Cole plots revealed the chain extended copolyester to have higher elasticity than that of the branched copolyester. The chain extended copolyester exhibited suitable melt and rheological properties for applications as a toner binder in the laser printing processes.