Synthesis and properties of a novel bio‐based benzoxazine resin with excellent low‐temperature curing ability

A novel bio‐based benzoxazine resin (diphenolic acid/furfurylamine benzoxazine resin, PDPA‐F‐Boz) was prepared by using bio‐based diphenolic acid, furfurylamine and paraformaldehyde as raw materials. The structure of DPA‐F‐Boz monomer was characterized by Fourier transform infrared spectroscopy, ¹H NMR and ¹³C NMR, and then its curing reaction and the thermal stability of the cured PDPA‐F‐Boz were analyzed. Compared with the traditional fossil‐based benzoxazine (bisphenol A/aniline benzoxazine, BPA‐A‐Boz) and the bio‐based benzoxazine (diphenolic acid/aniline benzoxazine, DPA‐A‐Boz), DPA‐F‐Boz monomer showed the lowest curing temperature, and PDPA‐F‐Boz had the highest residual char ratio at 800 °C and the lowest degradation rate at the peak temperature. Meanwhile, the total heat release, peak heat release rate and heat release capacity of PDPA‐F‐Boz were much lower than those of PBPA‐A‐Boz and PDPA‐A‐Boz. Thus, PDPA‐F‐Boz showed excellent low‐temperature curing ability and thermal stability. © 2019 Society of Chemical Industry     

Single component self‐curable aqueous‐based PU system with new aziridinyl curing agent

The self‐emulsified aqueous‐based polyurethane (PU) consists of carboxyl group, which is an ionic center not only stabilizing the aqueous polymer dispersion but also serving as the curing site toward aziridinyl curing agent. Two new aziridinyl curing agents, HDI‐AZ and ADA‐AZ, are prepared from an addition reaction of aziridine to hexamethylene diisocyanate (HDI) and adipic acyl chloride (ADA), respectively. These curing agents are added separately into NCO‐terminated PU prepolymer before or after the water dispersion process. The resulting PU dispersion becomes a single component self‐curable aqueous‐based PU system. The cured PU is obtained from this single component PU dispersion on drying at ambient temperature. The improved PU properties demonstrate the feasibility of this convenient single component self‐curable aqueous‐based PU system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:1997–2007, 2004     

Polymerization efficiency of bulk‐fill dental resin composites with different curing modes

The aim of this study was to investigate the effect of four different curing modes on the polymerization efficiency of eight bulk‐fill composites. Five specimens for each material were prepared for Vickers hardness measurements. The measurements were performed at 0 and 2 or 4 mm from the top of the surface of the specimens 24 h after photopolymerization. Statistical analysis was performed with one‐way analysis of variance and Tukey post hoc tests at a level of significance of a = 0.05 where a is the the level of significance. The light‐curing mode affected the microhardness in all depths, but this influence was material‐dependent (p_mat < 0.001), where p_mat is the probability to be affected by the material. The Vickers hardness numbers of the tested composites at 0 mm ranged from 9.32 ± 0.87 to 72.58 ± 6.52 and those of the tested composites at 4 mm ranged from 5.48 ± 0.32 to 54.34 ± 2.27. The clinician has to be aware of the technical characteristics of the materials and light‐curing units (LCUs) to use the most appropriate combination of LCU, composite material, and application technique. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43392.     

Effects of processing parameters on axial stiffness of self‐reinforced polyethylene composites

Self‐reinforced polyethylene composites have proven to be promising candidate materials for a number of wear‐resistance and bioimplant applications. In this study, we investigated the effects of processing parameters on the elastic modulus of self‐reinforced high‐density polyethylene (HDPE) composites. The processing parameters investigated were the cooling rate, processing pressure, temperature, and duration. Our results showed an optimum processing temperature, pressure, and duration that were matrix‐dependent. In addition, for an HDPE matrix, the slower the composite cooling rate was, the higher the composite modulus was. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1136–1141, 2001     

A new tri‐functional azetidine compound for self‐curing aqueous‐based PU system

A mono‐azetidine compound had been demonstrating a ring opening reaction with carboxylic acid (e.g., trimethylacetic acid, TMAA) and that resulted in an amino ester bond formation at ambient temperature. A triazetidine compound (trimethylolpropane tris(1‐azetidinyl)propionate, TMPTA‐AZT) was obtained via Michael addition of azetidine (AZT) to trimethylolpropane triacrylate (TMPTA). The carboxylic groups of anionic aqueous‐based polyurethanes (PU) served as internal emulsifier, which stabilized PU dispersion and also served as PU curing sites. The triazetidine compound (TMPTA‐AZT) was introduced into anionic aqueous‐based PU dispersion as a new latent curing agent and that mixture became a single‐component self‐curable aqueous PU system. A crosslinked PU film was obtained from this PU system on drying at ambient temperature. The final polymer performance properties demonstrated the crosslinking behaviors of this new curing agent, TMPTA‐AZT, with carboxylic ion‐containing aqueous‐based PU resins. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and properties of soybean oil–based curing agents for epoxy resin

In order to improve the flexibility properties of conventional epoxy resin, two novel soybean oil–based curing agents were synthesized. The curing agent obtained from the reaction between epoxy soybean oil and ethylene diamine was named EEDA, and another curing agent derived from epoxy soybean oil and isophorone diamine was named EIPDA. Several techniques were used to systematically investigate the effects of the structure and content of the two curing agents on the properties of the cured products. The Fourier transform infrared analysis demonstrated that epoxy resin reacted with soybean oil–based curing agents. The differential scanning calorimetry analysis showed that the curing process between diglycidyl ether of bisphenol‐A (DGEBA) and soybean oil–based curing agents only had an exothermic peak. Thermogravimetric analysis indicated that the cured DGEBA/EIPDA system was more stable than the DGEBA/EEDA system below 300 °C. Mechanical tests and Shore D hardness tests suggested that excessive EEDA greatly enhanced the toughness of cured products because of the introduction of aliphatic chains.© 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44754.     

Study on the curing process of QY8911‐3 resin

The effect of t‐butyl peroxybenzoate (TBPB) on the cure reaction of QY8911‐3 resin (BMI) was studied by differential scanning calorimetry (DSC) and gel time analysis. The mechanical properties of the resin and the composite were tested and analyzed with the peroxide content. The results showed that TBPB decomposed between 117 and 191°C and the enthalpy was 1123 J/g. TBPB reduced the initial reaction temperature, prompted the reaction speed, and shortened the gel time of the BMI resin. TBPB also increased the bending strength and decreased the impacting strength of the postcured samples. So, the peroxide content should be less than 0.6%. CF/SiO₂/BMI composites were prepared from the BMI containing peroxide and their microstructure and properties were better than those of the composites free of peroxide. According to the injection‐molding experiment, the spilling problem was overcome and the forming time was reduced from 2 h to 15 min when peroxide was added. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3769–3773, 2003     

复合材料缠绕成型用电子束固化环氧树脂体系研究

为了研究适合于缠绕成型的低粘度可电子束固化复合材料的耐热环氧树脂基体,研究了不同组成的电子束固化树脂体系的粘度与温度的关系、耐热性与辐射剂量的关系及浇注体的力学性能。研究表明,树脂EB-4在60℃时粘度为389 mPa.s,树脂辐射固化的最佳剂量为150 kGy,而且在150 kGy辐射固化的EB-1、EB-4的玻璃化转变温度Tg分别为212.96℃、214.77℃,EB-4树脂浇注体的拉伸强度可以达到52.7 MPa,拉伸弹性模量2.79 GPa,断裂延伸率为2.18%,是1种适用于室温或低温下缠绕成型的耐热电子束固化环氧树脂基复合材料树脂体系。     

Synthesis and characterization of emulsion‐type curing agent of water‐borne epoxy resin

Self‐emulsified water‐borne epoxy curing agent of nonionic type was prepared using triethylene tetramine (TETA) and derivative of epoxy resin as a capping agent, which was synthesized by liquid epoxy resin (E51) and polyethylene glycol (PEG), and the curing agent possessed emulsification and curing properties at the same time. The curing agent with good property of emulsifying liquid epoxy resin could be obtained under the condition of the molar ratio of PEG : E51 : TETA as 0.8 : 1 : 3.5 at 80°C for 5 h. The mean particle size of the emulsion liquid was about 220 nm with the prepared curing agent and epoxy resin at the mass ratio of 1 : 3. The structure of the emulsion‐type curing agent was confirmed by FTIR and ¹H NMR spectra, and the mechanism of cured film formation was also analyzed by SEM photographs. The cured film prepared by the emulsion‐type curing agent and epoxy resin under ambient cure conditions showed good properties even at high staving temperature. This study provides useful suggestions for the application of the water‐borne epoxy resins in coating industry. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2652–2659, 2013     

Ultraviolet‐curing behavior of an epoxy acrylate resin system

Ultraviolet (UV)‐curing behavior of an epoxy acrylate resin system comprising an epoxy acrylate oligomer, a reactive diluent, and a photoinitiator was investigated by Fourier transform infrared (FTIR) spectroscopy. The conversion changes of the resin system containing 20 phr of 1,6‐hexanediol diacrylate as a reactive diluent and 2‐hydroxy‐2‐methyl‐1‐phenyl‐propan‐1‐one as a photoinitiator were measured under different UV‐curing conditions. The fractional conversion was calculated from the area of the absorption peak for the vinyl group vibration occurring at 810 cm^?1. The effects of photoinitiator concentration, total UV dosage, one‐step or stepwise UV irradiation, UV intensity, atmosphere, and temperature on the curing behavior of the resin system were investigated. The conversion of the resin system increased rapidly at the initial stage of the UV‐curing process but increased very slowly after that. The final conversion of the resin system was mainly affected by total UV dosage. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1180–1185, 2005     

Hybridization of aqueous PU/epoxy resin via a dual self‐curing process

Amino‐terminated and carboxyl‐containing polyurethane (PU) is prepared by an isocyanate‐terminated PU prepolymer process. Carboxyl‐containing epoxy resin is obtained from a half‐esterification of epoxy resin with maleic anhydride. These two aqueous resins are obtained after neutralization with triethylamine and dispersion into water phase, respectively. A latent curing agent (TMPTA‐AZ) is prepared by a Michael addition of aziridine with trimethylolpropane triacrylate (TMPTA). A self‐curing system of PU/epoxy hybrid is obtained from a blending of these two aqueous resins with latent curing agent. PU/epoxy hybrid is derived from two self‐curing reactions on drying. The first curing for hybridization between PU amino groups with oxirane groups of epoxy resin is via a ring‐opening reaction and the secondary curing takes place on carboxyl groups of PU/epoxy hybrid with aziridine of TMPTA‐AZ. The final properties of these dual self‐cured PU/epoxy hybrids are reported. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Long‐term development of thermophysical and mechanical properties of cold‐curing structural adhesives due to post‐curing

The long‐term changes in the thermophysical and mechanical properties of a cold‐curing structural epoxy adhesive were investigated by accelerating the curing reaction by post‐curing at elevated temperatures. Experimental data concerning the glass transition temperature for periods of up to 7 years and tensile strength and stiffness measurements could be extrapolated for a period of up to 17 years. An existing model for the long‐term development of concrete properties was modified for the prediction of the long‐term mechanical properties of adhesives. The applicability of the acceleration procedure and the new model was confirmed by several verification procedures. Structural adhesives exhibit significant increases in glass transition temperature, strength and stiffness over the long term provided that joints are adequately sealed and protected from humidity and UV radiation. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

二茂铁甲酸封端不饱和聚酯的固化及热性能研究

以乙二醇、反丁烯二酸为原料合成的不饱和聚酯作为主链,二茂铁甲酸(FCA)作为封端剂,合成了含二茂铁基的不饱和聚酯(RFc),采用红外光谱对产物结构进行了表征。采用DSC及TGA研究了不同二茂铁甲酸含量对不饱和聚酯树脂固化性能和热稳定性的影响。结果表明,随着二茂铁甲酸含量的增加,RFc树脂固化反应活性减弱,热稳定性下降。其最高放热峰温度在171～173℃,且具有比较宽的加工温度范围(152～195℃),符合模塑料固化工艺要求。树脂的耐热性较好,初始热分解温度约为340℃,N2气氛下600℃残炭率可达19.76%。     

Studies on curing kinetics and thermal behavior of phosphorylated epoxy resin in the presence of aromatic amide‐amines

This article describes the synthesis of some novel aromatic amide‐amine curing agents by reacting 1 mole of p‐amino benzoic acid with 1 mole of each of 1,4‐phenylene diamine (P), 1,5‐diamino naphthalene (N), 4,4′‐(9‐fluorenyllidene)‐dianiline (F), 3,4′‐oxydianiline (O), and 4,4′‐diaminodiphenyl sulphide (DS) and were designated as PA, NA, FA, OA, and SA, respectively. The aromatic amide‐amines so synthesized were characterized with the help of spectroscopic techniques, viz., Fourier Transform Infrared, proton nuclear magnetic resonance, and carbon nuclear magnetic resonance. The curing kinetics of the epoxy resins obtained by reacting amines with diglycidyl ether of bisphenol‐A blended with tris(glycidyloxy)phosphine oxide in a ratio of 3 : 2, respectively, were investigated by DSC technique using multiple heating rate method (5, 10, 15, 20°C/min). Activation energies were determined by fitting the experimental data into Kissinger and Flynn‐Wall‐Ozawa Kinetic models. The activation energies obtained through Flynn‐Wall‐Ozawa method were slightly higher than Kissinger method but were comparable. However, both the energies were found to be dependent on the structure of amines. The thermal stability and weight loss behavior of isothermally cured thermosets were also investigated using thermogravimetric analysis in nitrogen atmosphere. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fourier transform IR and differential scanning calorimetry study of curing of trifunctional amino‐epoxy resin

The curing process was studied for a trifunctional epoxy resin, triglycidyl‐p‐aminophenol, using the hardener 4,4′‐diaminodiphenylsulfone. Two curing cycles were carried out: one following the manufacturer's guidelines (2 h at 80°C, 1 h at 100°C, 4 h at 150°C, and 24 h at 200°C) and another proposed in this study, in which the two stages at low temperatures were excluded. Fourier transform IR spectroscopy was used to quantify the conversion of different functional groups (primary amine, secondary amine, epoxide, hydroxyl and ether functional groups), and these conversions could be used to infer the type of reactions that took place. These results allowed us to analyze the evolution of the curing process over time and the influence of the curing cycle. Furthermore, the enthalpy of the curing process was determined using differential scanning calorimetry, and from this the thermal conversion for the whole process was evaluated. By taking into account the autocatalytic kinetic model, the rate constants were evaluated. The glass‐transition temperatures were also estimated by applying different curing cycles to the resin. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1524–1535, 2005     

复合材料气瓶用环氧树脂固化性能研究

为了制造复合材料气瓶,采用红外光谱、动态模量分析(DMA)等方法研究了按不同升温制度固化的复合材料气瓶用环氧树脂基体的反应固化度、玻璃化转变温度(Tg)以及其力学性能,以考察固化温度对树脂基体性能的影响,并对2种固化制度各自优缺点进行了对比分析。结果表明:加上促进剂可有效降低固化反应温度,80℃固化8 h固化度可达95%以上。同130℃固化4 h结果相似。试验证明该基体配方可以作为高性能湿法缠绕复合材料气瓶用树脂基体配方。     

A study of localized curing of glass‐filled composites using microhardness measurements

Extent of cure of hybrid composite systems is examined by conducting hardness measurements at different stages of the photopolymerization reaction and obtaining kinetic parameters that matched the experimental data. The materials are commercial dental composites based on bis[4‐(2‐hydroxy‐3‐methacryloyloxypropoxy)phenyl]propane resins with different photoinitiator concentrations as well as filler particle sizes and combinations. Samples (five per group) were made using nylon molds (2.5 × 5 mm) of the tested composites. The samples were light cured with a constant‐power light source for durations up to 20 s. After curing, all samples underwent Vicker's hardness testing of top and bottom surfaces. While there are significant differences in the polymerization behavior between the top and bottom locations for the tested composites, the corresponding growth exponent n, a kinetic parameter in the kinetic theory, is very close in all cases. For the tested materials the coefficient factor k is much lower for the bottom surfaces compared with the top surfaces. This reduction in the value of k is more severe for the material with a higher concentration of the photoinitiator as well as a higher percentage of glass filler particles in the wavelength range affecting the photopolymerization. It is argued that a relationship between k and the irradiation intensity can be used to quantify the decay of irradiated light with its penetration into the composites. The comparisons can be used to draw preliminary conclusions on the parameters controlling the effective depth of cure in a hybrid composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 426–431, 2005     

Preparation and physical properties of functionalized graphene/waterborne polyurethane UV‐curing composites by click chemistry

Functionalized graphene nanoplatelets (f‐GNS) were modified with (3‐mercaptopropyl)trimethoxysilane (MPTMS) to enhance their compatibility with the polyurethane coating matrix. The results of Fourier transform infrared spectroscopy, AFM, Raman and XRD showed that the MPTMS was successfully attached onto the surface of the graphene nanoplatelets. Functionalized graphene/waterborne polyurethane acrylate (f‐GNS/WPUA) nanocomposites were fabricated by UV‐curing technology. The SEM and TEM images indicated that f‐GNS could be well dispersed in the polymer matrix and improved the interfacial adhesion. With the incorporation of 1 wt% f‐GNS, the thermal decomposition temperature of the composites was increased by 25 °C. Meanwhile, the conductivity, hydrophobicity and tensile strength were increased. When the load was further increased, the performance of the composites showed varying degrees of reduction. However, the dielectric loss tangent (tan δ) could be maintained at 0.08 or less and the electromagnetic shielding factor of the composites reached from 5 to 36 dB, showing a good electromagnetic shielding effect at a high content (2.5 wt% f‐GNS). It was considered that f‐GNS could disperse in the waterborne polyurethane well and crosslink with the polyurethane. © 2016 Society of Chemical Industry     

Cationic electron‐beam curing of a high‐functionality epoxy: effect of post‐curing on glass transition and conversion

This paper reports on the cationic electron‐beam curing of a high‐functionality SU8 epoxy resin, which is extensively used as a UV‐curing negative photoresist for micro‐electronics machine systems (MEMS) applications. Results show that elevated post‐curing treatment significantly increased both the conversion and the glass transition. The degree of conversion and the glass transition temperature were measured by using Fourier‐transform infrared (FTIR) spectroscopy and modulated differential scanning calorimetry (MDSC^®), respectively. The glass transition temperature (T_g), which has been observed to be dependent on the degree of conversion, reaches a maximum of 162 °C at 50 Mrad and post‐curing at 90 °C. The degradation pattern of the cured resin does not show much variation for exposure at 5 Mrad, but does show significant variation for 50 Mrad exposure at various post‐curing temperatures. A degree of conversion of more than 0.8 was achieved at a dosage of 30 Mrad with post curing at 80 °C, for the epoxy resin with an average functionality of 8 a feature simply not achievable when using UV‐curing. Copyright © 2004 Society of Chemical Industry     

Synthesis,curing behavior and thermal properties of silicon‐containing hybrid polymers with Si−C≡C units

Three novel kinds of linear silicon‐containing hybrid polymers with Si?C≡C units were synthesized by polycondensation reactions using the Grignard reagent method. All the polymers were thermosetting, highly heat‐resistant, moldable and easily soluble in common organic solvents. The structure, curing behavior, thermal and oxidative properties were characterized using Fourier transform infrared spectroscopy, ¹H NMR, ¹³C NMR, gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis. The results obtained can provide theoretical guidance for determining the curing of the resin system. In addition, the cured polymers exhibit excellent thermal and oxidative stabilities with temperatures of 5% weight loss (T_d5) above 480 °C and 450 °C in nitrogen and air respectively; the residues at 1000 °C were above 70.0% and 45.0% respectively. The thermal and oxidative stabilities of the polymers are attributed to a crosslinking reaction between the Si?H and C≡C bonds or C≡C bonds. These polymers have the potential for use as high‐temperature‐resistant resins and ceramic precursors. © 2013 Society of Chemical Industry