A photo-curing study of a pigmented UV-curable alkyd

The photo-curing of a pigmented UV-curable tung oil alkyd system (UVTA) was investigated. The UV-curable alkyd was a Diels–Alder Adduct of trimethylolpropane trimethacrylate with a tung oil-based alkyd. A mixture of yellow iron oxide, red iron oxide, titanium dioxide and lamp black pigments were chosen to obtain an observed yellow color. The pigment mixture, UV-curable alkyd and a reactive diluent were formulated together and photo-cured via a free radical mechanism. The through and surface cure was assessed by thumb twist, blocking resistance and MEK single rub. The through cure and surface cure assessment showed that optimum cure was achieved using UV-A as a source with two photoinitiators: phenylbis(2,4,6-trimethylbenzoyl-phosphine oxide) at 2 wt% and 1-hydroxy-cyclohexyl-phenyl-ketone at 4 wt%. The effect of reactive diluent was also investigated. Ten different reactive diluents were used. After curing, pencil hardness, conical mandrel, impact resistance, cross cut adhesion and gloss were measured. In addition, dynamic mechanical thermal analysis (DMTA) was used to evaluate selected systems. The coatings tests showed that the use of long chain linear structure diluents, such as isodecyl methacrylate, provided UV-curable paint films with better impact resistance, flexibility, and adhesion over other reactive diluents.     

Synthesis and properties of acrylate functionalized alkyds via a Diels–Alder reaction

The α-eleosterate pendent fatty acid of a tung oil based alkyd was functionalized via a Diels–Alder reaction with three different acrylate groups: (1) 2,2,2-trifluoroethyl methacrylate, (2) 3-methacryloxypropyl trimethoxysilane, and (3) triallyl ether acrylate. The modified alkyds were characterized by using ¹H NMR, ¹³C NMR, and gel permeation chromatography (GPC). The drying time was measured at ambient temperature. The viscoelastic properties of the alkyd-modified films were measured using dynamic mechanical thermal analysis. The viscoelastic and drying time results show that the alkyd modified with siloxane and triallyl group affords a faster drying time, higher crosslink density, and higher glass transition temperature compared to the unmodified alkyd, whereas the fluorinated alkyd possesses surface active properties, but suffers in terms of drying and crosslinking density.     

Tung based reactive diluents for alkyd systems: Film properties

Reactive diluents were prepared from tung oil via a Diels–Alder reaction with three different dienophiles: methacryloxypropyl trimethoxysilane (TOMAS), 2,2,2-trifluoroethyl methacrylate (TOF) and triallyl ether acrylate (TOTAE). The reactive diluents were mixed with a long oil soya alkyd, a metal drier package, and a wetting agent; and then cured. Formulations were prepared as a function of reactive diluent type and wt%. Tensile, thermomechanical, and coatings properties were evaluated after curing the films. The addition of two reactive diluents, TOMAS and TOTAE, improved the tensile strength and tensile modulus of the alkyd. The addition of the diluents, however, did not significantly change the elongation at break compared to the alkyd in any of the systems. Also, the addition of TOMAS and TOTAE increased both the crosslink density and glass transition temperature of the alkyd. Basic film properties including hardness, solvent resistance, impact resistance, adhesion, and gloss were not adversely affected by the introduction of any of the tung oil based diluents.     

桐油基水性光固化树脂的合成及性能研究

以生物质资源桐油（TO）、马来酸酐（MA）为原料,通过Diels-Alder反应合成了桐油酸酐,再以其与丙烯酸羟乙酯（HEA）反应,经中和水化制备了桐油基水性光固化树脂。通过红外光谱（FTIR）、核磁共振氢谱（1H NMR）表征了合成产物的分子结构。考察了TO、MA以及HEA的比例对桐油基水性光固化树脂的乳液性质、光固化活性以及涂膜性能的影响。研究结果表明,当n(TO):n(MA):n(HEA):n(TEA)= 1:2.5:2.5:2.5时,合成的桐油基水性光固化树脂的稳定性、光固化活性以及涂膜性能最优异。     

Preparation of pressure-sensitive adhesives from tung oil via Diels-Alder reaction

In this study, tung oil was polymerized with a dimaleimide (4,4’-methylene-bis(N-phenylmaleimide) (MPMI) and two diacrylates (poly(propylene glycol) diacrylate (PPGDA) and bisphenol A glycerolate diacrylate (BPAGDA) via Diels-Alder reaction (DA reaction) to prepare pressure-sensitive adhesives (PSAs). On the one hand, the polymer of tung oil and MPMI was readily prepared however it was too rigid to serve as a PSA. On the other hand, the polymerization of tung oil with PPGDA or BPAGDA resulted in PSAs with peel strengths ranging from 0.1 to 0.2 N cm⁻¹ and loop tacks ranging from 0.4 to 0.5 N. Nevertheless, tung oil reacted readily with acrylic acid to form adducts (TOAA) with lower content of conjugated diene groups than those of tung oil. The use of TOAAs instead of tung oil to polymerize PPGDA failed to increase the peel strength of the resulting PSAs. However, polymerizations of TOAAs with BPAGDA resulted in PSAs with much higher peel strengths and much higher loop tacks than the polymerization of tung oil with BPAGDA. In addition, the introduction of a small amount of MPMI in the polymerization of TOAA and PPGDA significantly shortened the curing time.     

Preparation and properties of glycerin ester of tung oil modified rosin

Tung oil modified rosins (TR) were prepared by reaction rosin with different amount of tung oil via Diels‐Alder addition reaction and further used in the formulation of glycerin ester of tung oil modified rosins (GTR) with flexible characteristics. The effects of the amount of tung oil on the bromine value, molecular weight, thermostability, physical, and tackifying properties of GTRs were studied. The results showed that the bromine value of GTRs decreased and molecular weight of GTRs increased with the increase in the amount of tung oil. Meanwhile, increasing the amount of tung oil resulted in a significant decrease in both the softening points and viscosities of GTRs, but a slight increase in the thermostability of GTRs due to the incorporation of the flexible fatty chains into the rigid hydrophenanthrene units in rosins. Applied in PU adhesive as tackifier, the increase of the flexible chains content in GTRs led to an increase first and then decrease in both the miscibility of GTRs with PU and the T‐peel strength of adhesives. The elongation at break of films increased monotonously, but their tensile strengths increased first and then decreased with increasing the flexible chains content in GTRs. GTRs with desired properties were prepared when the tung oil/rosin weight ratios were in the range from10/100 to 40/100. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1700–1706, 2013     

Polymerization of tung oil by reaction of phenols with tung oil

Investigation was made on the mechanism of polymerization in reactions of tung oil and phenols in the presence of an acid catalyst. It was made by means of comparative HLC and NMR analyses of the products of tung oil self-polymerization, other varied vegetable oil-various phenol reactions, and tung oil-various-in-functionality phenol reactions under given conditions. As a result, it was confirmed that polymerization in reactions of tung oil and phenols is attributed not to tung oil self-polymerization but to di- or trialkylation, with tung oil, of phenols, which can serve as crosslinking agents of tung oil.     

A one-pot approach to dendritic star polymers via double click reactions

A class of well-defined dendritic star polymers with poly (ε-caprolactone) (PCLs) on the periphery has been prepared via one-pot double click reactions (Cu-catalyzed azide/alkyne click chemistry, i.e., CuAAC and Diels–Alder [4+2] cycloaddition reactions). The predecessors for Diels–Alder reaction, maleimide end-functionalized PCLs were produced by ring-opening polymerization (ROP). Obtained dendritic star polymers were characterized by ¹H NMR, size exclusion chromatography (SEC), UV/vis, and fluorescence spectroscopy.     

Boron-containing UV-curable oligomer-based linseed oil as flame-retardant coatings: synthesis and characterization

A boron-containing UV-curable oligomer was derived from linseed oil, phenylboronic acid and glycidyl methacrylate to use in flame-retardant coating applications. The synthesized UV-curable oligomer was characterized for its structural and physicochemical properties by means of Fourier transform infrared (FTIR), ¹H and ¹¹B-nuclear magnetic resonance (NMR) spectroscopy techniques. The boron-containing UV-curable oligomer (BELO) was added to a conventional polyurethane acrylate (PUA) at varying concentrations ranging from 10 to 40 wt% in the presence of a photoinitiator and a reactive diluent. LOI and UL-94 tests were performed to understand the flame-retardancy behavior of the synthesized BELO oligomer, and the results revealed that the flame retardancy of UV-curable coatings enhanced as the percentage of BELO oligomer in the coating formulations increased. The glass transition temperature (T_g) and thermal stability of cured coatings were analyzed by differential scanning calorimetry and thermogravimetric analysis, respectively. The TGA analysis showed that char yield at 600 °C increased by increasing the BELO oligomer content. The mechanical properties, and stain, solvent, and chemical resistance and thermal behavior of the coatings were investigated. Incorporation of BELO into the PUA coating formulations and the comparison of the properties of BELO-incorporated PUA coatings with those of the conventional PUA coating exhibited interesting results.     

桐油改性双环戊二烯不饱和树脂的固化研究

采用红外光谱(FT-IR)和示差扫描量热法(DSC)对桐油改性DCPD-UPR的固化特性和固化动力学进行了研究。利用Kissinger方程和Crane方程计算得到桐油改性DCPD-UPR的表观活化能94.03 kJ/mol,反应级数为0.94,指前因子为2.185×1012。利用T-β外推法确定了桐油改性DCPD-UPR的固化温度为107.28℃,后处理温度为120.65℃。较未改性的DCPD-UPR,桐油改性DCPD-UPR的固化放热曲线平缓,放热峰温度低,固化时间长,可以避免树脂固化成型时翘曲、开裂等现象的发生。     

Preparation and properties of epoxy‐modified tung oil waterborne insulation varnish

This work aimed to develop a novel epoxy‐modified tung oil waterborne insulation varnish with blocked hexamethylene diisocyanate as a curing agent. The Diels–Alder reaction between tung oil and maleic anhydride, and the ring‐opening esterification reaction of epoxy resin were confirmed. The conversion rate of epoxy was explored as a function of reaction time and temperature. The effects of epoxy resin content on the thermal stability, water absorption and insulation properties (insulation strength, volume resistivity, and surface resistivity) of films were investigated, and the resistances of films to salted water were evaluated. The increase in epoxy resin contents could improve the thermal stability and insulation properties of films, and decreased the water adsorption of films, but when the epoxy resin content reached 30% and above, the water solubility of resin became poor. After being immersed in 3.5 wt % NaCl solution, the electrical insulation strength of films were lower than that in dry state, and decreased as the immersed time prolonged. In particular, the electrical insulation strength loss of films increased significantly for epoxy resin content at 15% and below. Furthermore, the increase of epoxy resin content could improve the hardness and adhesion of films, but the flexibility of films became worse. On the basis of experimental, the epoxy resin content at 25% was appropriate to prepare waterborne epoxy‐modified tung oil resin. The resulting varnish may have potential as an immersing insulation varnish for the spindle of electric motor. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42755.     

Reaction of 3-methyl phenol with tung oil

The aromatic ring substitution reaction of 3-methyl phenol with tung oil under acidic conditions was carried out. The product was analyzed to find out if 3-methyl phenol was subjected to the ring substitution reaction with tung oil at its conjugated double bonds. Up to two molecules of 3-methyl phenol were addition-reacted with the conjugated triene of one eleostearyl group of triglyceride of α-eleostearic acid which is the major component of tung oil. The 4-position of 3-methyl phenol was preferentially subjected to the cresol's ring substitution. Therefore, up to 6 mol of 3-methyl phenol was added to 1 mol of tung oil, most of which was bonded to 3-methyl phenol at its 4-position. When 3-methyl phenol was reacted with a relatively large amount of tung oil, the substitution reaction occurred at the 6-as well as 4-position of 3-methyl phenol to yield a tung oil dimer having 3-methyl phenol units in its molecule. The above results were confirmed by infrared (IR), nuclear magnetic resonance (NMR), and high-speed liquid chromatographic (HLC) analyses.     

UV-curable hyperbranched urethane acrylate oligomers modified with different fatty acids

The UV-curable hyperbranched urethane acrylate oligomers modified with different fatty acids including undecylenic acid (UCA), myristic acid (MA), and oleic oil (OA) are successfully synthesized in this paper. The prepared oligomers are characterized using FTIR, ¹HNMR, GPC, DSC, and TGA. The properties of the UV-curable films formed by these oligomers are also determined. The effects of the oligomer structures including double bond content, chain length of the modified fatty acids, and content of fatty acid and polyurethane acrylate segment, on the properties of the cured films, which are tack-free time, pencil hardness, impact resistance, adhesion, and boiling water resistance, are discussed in detail. It is observed that the curing film formed by HBPE₂-60%UCA-20%PUA shows the best comprehensive performance among the films prepared in this study.     

Synthesis and Characterization of Tetra-Functional Epoxy Resins from Rosin

Tetra functional epoxy resins were prepared by the reaction of diethanolamine with Diels–Alder adducts of rosin ketone. These adducts were reacted with epichlorohydrine in the presence of NaOH as a catalyst to produce epoxy resins. The resins obtained were characterized by IR and ¹H NMR spectroscopy. The curing behaviours of these resins with their poly (amide-imide) derivatives were investigated by viscosity measurements. The curing activation energy was calculated from the gel time and critical viscosity measurements. The curing exotherms of the epoxy resins produced with poly (amide-imide) hardeners were investigated. The curing and gel times of the resins produced show slight differences between the synthesized resins. The chemical resistances and mechanical properties of the cured films were evaluated. The produced coats show high stability for salt spray at a duration time of 563 h.     

High bio-based content waterborne UV-curable coatings with excellent adhesion and flexibility

A series of bio-based unsaturated polyesters was synthesized by melt polycondensation of itaconic acid with 1,4-butanediol and glycerol. Their chemical structures were confirmed by FT-IR, ¹H NMR, acid and hydroxyl values. Waterborne UV curable dispersion coatings based on these polyesters and acrylated epoxidized soybean oil (AESO) were formulated. The average particle size and their stability before curing as well as the coating properties after curing, including adhesion, flexibility, pencil hardness and solvent resistance, were investigated. Results demonstrated that the glycerol segment in the polyesters together with AESO led to the excellent coating properties in terms of highest grade of adhesion (5B), 0T flexibility, pencil hardness of 5H and excellent solvent resistance (no appearance change after 250 double rubs with ethanol and acetone). This work provided us the coating systems combining the merits of being bio-based, UV-curable and water dispersible.     

High performance bio‐based thermosetting resins composed of tung oil and bismaleimide

The reaction of tung oil (TO) and 1,1′‐(methylenedi‐4,1‐phenylene)bismaleimide (BMI) in 1,3‐dimethyl‐2‐imidazolidinone (DMI) at 150°C for 4 h and subsequent precipitation gave TO/BMI prepolymer, which was cured at 200°C for 2 h gave crosslinked TO/BMI product with CC ratio from 1/1 to 1/4. The FE‐SEM analysis revealed that all the cured products are homogeneous and no phase separation was observed. The glass transition temperature and 5% weight loss temperature of the cured TO/BMI increased with increasing BMI content. The maximal tensile strength (38.1 MPa) and modulus (2.6 GPa) were obtained for the cured products with the CC ratios of 1/2 and 1/3, respectively. To evaluate the reaction of TO and BMI, the model reaction products of TO and N‐phenylmaleimide (PMI) in DMI were analyzed by ¹H‐NMR spectroscopy. The NMR data of the reaction products of TO/PMI with the CC ratio 2/1, 1/1, 1/2, 1/3, and 1/4 at 150°C for 24 h revealed that Diels‐Alder reaction preferentially occurred at 2/1, and that ene reaction and other reactions such as radical homo and copolymerization gradually increased with decreasing CC ratio of TO/PMI. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The performance of biodegradable tung oil coatings

Using immersion tests, viscosity measurements, FTIR and SEM, as well as biodegradation tests, biodegradable tung oil coatings were investigated. Results showed that the curing times for different formulae decreased as the amount of catalyst increased. During the curing process, there was an initial induction period where the viscosity remained more or less the same, and after a certain time, a sharp increase in viscosity was observed. The steady viscosity increased with time, revealing a continuous autoxidation process. Microorganisms in the soil attacked the surfaces of the tung oil films either uniformly on the whole plate or at specific weak points, leading to decreased volume, blurring of the small humps as well as holes. The weak point on the crosslinked chain was located at the carbonyl-containing groups, where chemical biodegradation occurred more easily and faster.     

Preparation and characterization of tung oil-based flame retardant polyols

Three kinds of tung oil-based structural flame retardants polyols (TOFPs) were prepared by new methods in this paper. First, tung oil was used to produce monoglyceride and diglyceride by transesterification with glycerol by sodium methoxide. The products after transesterification were epoxidized by peracetic acid which was in-situ generated from acetic acid and hydrogen peroxide in the presence of sulfuric acid catalyst. And then, TOFPs were prepared from epoxidized alcoholysis tung oil (EGTO) with 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), diethyl phosphate (DEP) and diethanolamine (DEA) by ring-opening reactions, respectively. GPC was used to evaluate the conversion rate, at optimum reaction conditions, selectivity for monoglyceride in transesterification. The influence of different parameters such as temperature, mole ratio or mass ratio on the conversion rate of transesterification and epoxidation were investigated. The molecular structures of TOFPs were characterized by FTIR and ¹HNMR. Finally, tung oil-based polyurethane foams (TOPUFs) were prepared by a one-shot process using TOFPs with polyisocyanate. The LOI values of TOPUFs whose content of DOPO-EGTO, DEP-EGTO and DEA-EGTO were 100 wt% can reach to 26.2%, 25.1%, and 24.4%, respectively.     

Synthesis and characterization of novel renewable castor oil-based UV-curable polyfunctional polyurethane acrylate

In recent years, a lot of interest has been given to renewable resources for their environmental friendliness and potential biodegradability in the synthesis of urethane-derived polymers. In this work, UV-curable castor oil-based polyfunctional polyurethane acrylate (COPUA) was prepared by the reaction of isophorone diisocyanate (IPDI) with castor oil and pentaerythritol triacrylate (PETA). The structures and molecular weights of the targeted IPDI–PETA and COPUA were characterized by FTIR, ¹H NMR, and GPC, respectively. In addition, the effect of reactive diluent content on damping properties, thermal stabilities, and mechanical properties of COPUA was characterized by dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and universal test machine. DMA revealed the copolymers had a glass transition temperature (T _g) from 31.81 to 48.09°C. TGA showed that thermal initial decomposition temperatures were above 344.5°C, indicating the copolymers had certain thermal stability. Finally, some physical properties of curing films were studied by the contact angle and water absorption, and the results showed that the coatings exhibited good hydrophobicity. The COPUA obtained from castor oil can be used as eco-friendly materials and other applications alternative to the use of other petrochemicals in coatings.