Water transport in an epoxy–phenolic coating

Thermoset coatings commonly rely on high cross-linking density to provide enhanced barrier properties. Hence it is surprising that for the industrial epoxy–phenolic network investigated, equilibrium moisture uptake is found to increase with respect to cure time, i.e., with greater cross-linking. Molecular interactions between absorbed water and the resin are characterised using infrared spectroscopy, and water uptake is correlated to network polymer features such as polarity and free volume.     

双组分喷涂型无溶剂超厚膜环氧重防腐涂料的研制

选用高环氧值、低黏度改性环氧树脂作为基料树脂,按一定比例复配曼尼斯碱和腰果酚酚醛胺为固化剂,搭配自制触变性浆体、多活性端基低黏度聚合物活性稀释剂、缓蚀型颜填料及助剂,制备了一种双组分喷涂型无溶剂超厚膜环氧重防腐涂料,并对涂料性能影响因素进行了分析,对涂层性能进行了测试,结果显示该涂料机械性能和防腐性能优异。     

无溶剂环氧输油气管内低表面处理防腐减阻涂料的研制

以液态环氧树脂、稀释剂为基体树脂,以腰果壳液改性酚醛胺为固化剂,以复合铁钛粉、磷酸锌、氧化铁红、聚四氟乙烯、沉淀硫酸钡、陶瓷微珠等为填料,在多种功能助剂的配合下制备成无溶剂环氧输油气管内低表面处理防腐减阻涂料.集带锈带油、带湿涂装为一体,具有防腐、减阻、耐磨等特性.     

Design and UV-curable behaviour of boron based reactive diluent for epoxy acrylate oligomer used for flame retardant wood coating

Difunctional boron-containing reactive flame retardant for UV-curable epoxy acrylate oligomer was synthesized from phenyl boronic acid and glycidyl methacrylate. The synthesized reactive diluent was utilized to formulate ultraviolet (UV)-curable wood coatings. The weight fractions of reactive diluent in coatings formulation was varied from 5 to 25 wt % with constant photoinitiator concentration. The molecular structure of reactive flame retardant was confirmed by Fourier-transform infrared, Nuclear magnetic resonance (NMR) and ¹¹B NMR spectral analysis. Further, the efficacy of flame retardant behaviour of coatings was evaluated using limiting oxygen index and UL-94 vertical burning test. Thermal stability of cured coatings films were estimated from thermogravimetric and differential scanning calorimetry analysis. The effects of varying concentration of reactive diluent on the viscosity of coatings formulation along with optical, mechanical and chemical resistance properties of coatings were also evaluated. The coatings gel content, water absorption behaviour, contact angle analysis and stain resistance were also studied.     

Swelling of acrylic microgels in aliphatic ketones

The paper deals with the swelling behaviour of hydroxyl-functionalised microgels in the presence of aliphatic ketones. The copolymer microgels with different cross-linking densities were synthesized by the semi-batch emulsion copolymerisation of methyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate and allyl methacrylate. The extent of microgel particles swelling was evaluated using the dynamic light scattering, the potentiometric titration of accessible hydroxyl groups and the solvent-uptake measurements. It was found that the swelling ability of microgels decreased with growing degree of cross-linking. Microgels comprising copolymerised butyl methacrylate swelled less in utilised aliphatic ketones than microgels without this comonomer. Among all the investigated solvents, acetone was found to be the strongest solvent, while 5-methyl-2-hexanone (methyl isopentyl ketone) was shown to be the weakest one. Further, the microgels were investigated as reactive network precursors in a commercial thermosetting solvent-borne acrylic binder. It was shown that the application of functionalised microgels that were redispersed in acetone did not affect the surface appearance and transparency of coatings. Moreover, the presence of microgel network precursors accelerated film curing at ambient temperature and improved final hardness of coatings.     

Electrochemical characterisation of protective organic coatings for food packaging

A very common material for food packaging is steel, in the form of metallic containers (cans), in particular for beverage packaging. The corrosion degradation of the packaging must be carefully controlled, not only because the packaging integrity must be preserved, but also in order to avoid any significant contamination of the food or drink, compromising the flavour. In order to increase the coating performance and the food compatibility, new organic coatings are under development with very high protective properties, with the final aim to increase the shelf life of the product. An electrochemical characterisation is often used to study the protective performance of organic coatings on metal substrate for various applications. Some different coatings for food packaging were considered in the present study, including materials with different chemical composition and different pigments content. The protective properties were quantified using electrochemical impedance spectroscopy (EIS) measurements, comparing the electrochemical substrate activity with electrochemical noise (EN) and scanning Kelvin probe (SKP) measurements. The influence of mechanical deformations on the protective properties was also investigated. The results obtained on the studied coatings confirmed the validity of the electrochemical approach and showed that, in general, the coatings containing pigments (TiO₂) have better performance than clearcoats, while comparing the different polymers, epoxy–phenolic coatings have a better corrosion protection than epoxy–melamine coatings.     

Development of high performance,waterborne coatings. Part III: Characterization of coatings and cured film

High performance waterborne coatings were developed which could be utilized as an adhesive primer for sideseam bonded cans. The manufacturing process is unique; blending an epoxy / phenolic solution and an acrylic resin solution and dispersing the mixture in an aqueous medium by the phase transition method. The epoxy resins are neither chemically modified by grafting nor esterified by acrylic resin, which is thought to develop the excellent performance of epoxy / phenolic coatings. The morphology of the coatings and cured film was characterized and found to be quite different from the conventional waterborne coatings, i.e., the acrylic-modified epoxy resin systems. It was confirmed that acrylics and epoxy / phenolic resins exist in separate phases in the cured film, and that the epoxy / phenolic resin constitutes the continuous phase.     

Predicting the reactivity of phenolic compounds with formaldehyde. II. Continuation of an ab initio study

Phenol–formaldehyde resins are important adhesives used by the forest products industry. The phenolic compounds in these resins are derived primarily from petrochemical sources. Alternate sources of phenolic compounds include tannins, lignins, biomass pyrolysis products, and coal gasification products. Because of variations in their chemical structures, the reactivities of these phenolic compounds with formaldehyde vary in quite subtle ways. Previously, it was demonstrated that the reactivity of a number of phenols with formaldehyde in nonaqueous conditions could be correlated with charges calculated for reactive sites on the aromatic ring (Conner, A. H. J Appl Polym Sci 2000, 78, 355–363). We studied the reactivity of a larger number of phenolic compounds with formaldehyde in an aqueous solution using sodium hydroxide as the catalyst. Reaction rates were determined from measurements of the concentrations of the phenolic compounds and formaldehyde as functions of time. The reaction rate constants varied over a wide range (approximately 10^?2 to 10⁴ L mol^?1 h^?1). An estimate of the reactivity per reactive site on the phenolic ring was determined by dividing the rate by the number of reactive sites. Atomic charges for each phenolic compound were calculated by ab initio methods at the RHF/6‐31+ G level of theory using the CHelpG method. The charge per reactive site was estimated by summing the charges at all the reactive sites on the phenolic ring and dividing by the number of reactive sites. A strong correlation was observed between the reactivity per reactive site and the average charge per reactive site. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 135–140, 2002     

Fabrication and properties of SiCnw-reinforced SiC composites by reactive melt infiltration with BN and PyC interface

To tailor the fiber–matrix interface of SiC nanowires-reinforced SiC (SiC_nw/SiC) ceramic matrix composites (CMCs) for improved mechanical properties, SiC nanowires were coated with BN and pyrolytic carbon (PyC) compound coatings prepared by the dip-coating process in boric acid and urea solution and the pyrolysis of phenolic resin. SiC_nw/SiC CMC with PyC/BN interfaces were fabricated by reactive melt infiltration (RMI) at 1680°C for 1 h. The influences of phenolic resin content on the microstructure and mechanical properties of the CMC were investigated. The results showed that the flexural strength and fracture toughness reach the maximum values of 294 MPa and 4.74 MPa m^1/2 as the phenolic resin content was 16 and 12 wt%, respectively. The displacement–load curve of the sample exhibited a gradient drop with increasing phenolic resin content up to 12 wt%. The results demonstrated that the PyC/BN compound coatings could play the role of protecting the SiC_nw from degradation as well as improving the more moderate interfacial bonding strengths during the RMI.     

Thermal analysis and its application in evaluation of fluorinated polyimide membranes for gas separation

Seven polyimides based on (4,4′-hexafluoroisopropylidene) diphthalic anhydride, 6FDA, with different chemical structures were synthesized in a single pot two-step procedure by first producing a high molecular weight polyamic acid (PAA), followed by reaction with acetic anhydride to produce polyimide (PI). The resulting polymers were characterized using thermal analysis techniques including TGA, derivative weight analysis, TGA–MS, and DSC. The decarboxylation-induced thermal cross-linking, ester cross-linking through a diol, and ion-exchange reactions of selected polyimide membranes were investigated. Cross-linking of polymer membranes was confirmed by solubility tests and CO₂ permeability measurements. The thermal analysis provides simple and timesaving opportunities to characterize the polymer properties, the ability to optimize polymer cross-linking conditions, and to monitor polymer functionalization to develop high performance polymeric membranes for gas separations.     

Epoxy resin from cardanol as partial replacement of bisphenol-A-based epoxy for coating application

With continuous depletion of petrochemical feedstock and their rising prices, the chemical industry is now looking for alternative renewable and sustainable materials. Such materials could be processed with various chemistries to produce high performance functional materials for a range of applications, such as plastics, coatings, constructions, pharmaceuticals, and food applications. Cardanol derived from cashew nut shell liquid has a reactive phenolic group and aliphatic double bond that could be exploited to produce novel functional materials for polymer and coating applications. It has previously been used for preparation of phenolics, epoxy, and phenalkamine hardeners. In this study, we report on the preparation of novel epoxy resin from cardanol via simple a two-step reaction. The prepared resin with epoxy equivalent weight of 210–220 gm/eq was analyzed using FTIR and NMR spectroscopy. The epoxy resin was then used as binder along with bisphenol-A-based epoxy resin (DGEBPA) at various weight proportions and cured with different amine hardeners. The cured coatings were analyzed for physical, mechanical, and chemical properties for optimization of the coating formulation. The study conducted showed that 40–60% of DGEBPA resulted in comparable properties to that of completely DGEBPA-based system. Further, thermal and anticorrosive properties of the optimized coatings were also evaluated.     

Multifunctional,robust, and self-healable polyurethane coatings cross-linked by Diels–Alder reaction of calix[4] arenes containing furan groups

Self-healing coatings can restore their performance after inevitable damage and are promising in the industry owing to their longer service life and lower repair cost. The use of Diels–Alder reaction bonds is well-known to generate thermally self-healing coatings. In this study, a series of cross-linked self-healing polyurethane (PU) coatings were synthesized through Diels–Alder reactions of p-tert-butyl calix[4]arene bearing furan groups (C4A-FA) as a new chain extender and a bismaleimide (BMI) polyether amine as a Diels–Alder cross-linking agent. Adding C4A-FA to PUs improves their mechanical properties, thermal stability, and self-healing ability. Additionally, these modifications can result in the formation of composite networks with PU that exhibit thermoreversibility and self-healing properties. These changes have led to PUs containing modified calix[4]arene (C4A-FA) having better properties compared with unmodified calix[4]arene PUs. The properties of prepared coatings were evaluated by Fourier transform infrared spectroscopy, scanning electron microscope, differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), and tensile tests compared with a typical PU sample. The tensile and TGA results show an improvement in the thermal and mechanical properties of the polymers by increasing the C4A-FA content. By replacing 15% of butandiol (BDO) with C4A-FA in PU pure, the tensile strength increased from 1.69 to 5.14 MPa. Furthermore, adding diels–alder (DA) bonds enhanced the tensile strength to 10.49 MPa for PU-C4A15-DA. According to DSC results, a broad endothermic peak from nearly 80–140°C confirmed the retro-DA reactions in the synthesized thermoreversible samples. The healing efficiency of the PU-C4A15-DA sample was obtained at 92.5% (measured by tensile test), which is the highest value among cross-linked self-healing PUs reported in the literature.     

Ag–Sr doped mesoporous bioactive glass nanoparticles loaded chitosan/gelatin coating for orthopedic implants

In this study, we investigated surface and biological properties of Ag–Sr-doped mesoporous bioactive glass nanoparticle (Ag–Sr MBGN) loaded chitosan/gelatin coatings deposited by electrophoretic deposition (EPD) on 316L stainless steel. The EPD parameters, that is, deposition time, applied voltage, and distance between the electrodes was optimized by the Taguchi design of experiment (DoE) approach. Scanning electron microscopy (SEM) images illustrated the spherical morphology of the synthesized Ag–Sr MBGNs with the mean particle size of 160 ± 20 nm. Energy-dispersive X-ray (EDX) spectroscopy results confirmed the presence of Ag and Sr in the synthesized MBGNs. Optimum EPD parameters determined by DoE approach were 5 g/L of Ag–Sr MBGNs, deposition time of 5 min, and applied voltage of 30 V. SEM images confirmed that the coatings were fairly homogenous. Fourier-transform infrared spectroscopy and EDX results confirmed the presence of chitosan, gelatin, and Ag–Sr MBGNs in the coatings. Chitosan/gelatin/Ag–Sr MBGN composite coatings exhibited suitable wettability for the protein attachment and proliferation of osteoblast cells. The composite coatings exhibited suitable adhesion strength with the substrate. The coatings developed HA crystals upon immersion in simulated body fluid. The results of the turbidity test confirmed that the coatings are antibacterial to the Escherichia coli cells.     

高阻尼性涂层用环氧-丙烯酸酯复合乳液的合成

采用分步乳液聚合法合成了一种具有核-壳结构的环氧-丙烯酸酯复合乳液,通过核层和壳层之间的化学交联使涂膜具有较高的阻尼性能。通过透射电镜观察到乳胶粒子呈均匀的核-壳球形结构,红外光谱（FTIR）结果表明复合乳液涂膜实现了环氧与丙烯酸树脂的交联反应。动态热机械分析（DMA）显示该乳液涂膜具有较高的损耗因子和较宽的阻尼温域,加热成膜的最大损耗因子（tan δ）达到2.12,明显高于传统阻尼涂料,在tan δ >0.3的阻尼温域为40℃,在金属阻尼涂层材料领域具有良好的应用潜能。     

Synthesis of reactive copolymers with peroxide functionality for cross-linking water-soluble polymers

A series of reactive copolymers with peroxide functionality (RCPFs) were synthesized via radical copolymerization of monomer mixtures in an organic solvent comprised of a peroxide monomer 5-(tert-butyl peroxy)-5-methylhex-1-en-3-yne, acrylamide, maleic anhydride, and butyl methacrylate. Peroxide functionality allows the RCPFs to initiate a variety of radical processes, including cross-linking of organic polymers. Hydrophilic monomer subunits (acrylamide and maleic anhydride) within the RCPF macromolecules promote cross-linking of water-soluble polymers. We aimed to investigate RCPF comonomer ratio and its effects on copolymerization kinetics and composition, as well as physico-chemical and colloidal properties. We also evaluated and characterized the kinetic parameters of the thermal decomposition of peroxide moieties in the synthesized RCPF. Findings revealed that RCPF possessed surface-active properties and reduced surface tension at its aqueous solution–air interface. The data indicated that the decomposition process complied with the first-order kinetics, and complex thermal analysis confirmed the presence of peroxide moieties. RCPFs' ability to cross-link water-soluble polymers was demonstrated on poly(acrylamide) and poly(vinyl alcohol).     

高生物基含量光固化涂料的制备及其性能研究

环氧化大豆油丙烯酸酯(AESO)已大规模用于UV固化涂料中,但目前同时获得高生物基含量以及优异机械性能的大豆油基光固化涂料依然是一个很大的挑战。文中设计并合成了异山梨醇甲基丙烯酸酯(ISDMA)作为光固化活性稀释剂。使用流变仪研究了ISDMA对AESO稀释性的影响。将ISDMA与AESO混合制备了一系列生物基UV固化涂料,并对这些涂料的热机械性能、力学性能和涂层基本性能进行了评估。结果表明:ISDMA对AESO表现出良好稀释性的同时,可以有效地提高固化涂层的玻璃化转变温度(T_g)、储能模量和硬度。     

The synthesis and properties of triazine-stilbene fluorescent brighteners containing a monophenolic antioxidant

Various triazine-stilbene fluorescent brighteners that were substituted with four different amine derivatives including a phenolic antioxidant on 4,4′-bistriazine moieties were synthesized. The obtained compounds (6a–m) were characterized by the analysis of proton NMR spectrum and confirmed by UV spectrum. The physical properties of the new compounds (6a–m) were determined by fastness test and whiteness measurement and compared with those of CI86.     

UV-curable behavior of phosphorus- and nitrogen-based reactive diluent for epoxy acrylate oligomer used for flame-retardant wood coating

Multifunctional phosphorus and nitrogen containing tris-diethanolamine spirocyclic pentaerythritol bisphosphorate reactive diluent (TDSPBRD) for epoxy acrylate oligomer was synthesized from spirocyclic pentaerythritol bisphosphorate diphosphoryl chloride, diethanolamine, and allyl chloroformate. The synthesized reactive diluent was utilized to formulate ultraviolet (UV)-curable wood coating. The weight fraction of reactive diluent in the coating formulation was varied from 5 to 25 wt% with constant photoinitiator concentration. The molecular structure of the reactive flame retardant was confirmed by Fourier transform infrared (FTIR), ¹H nuclear magnetic resonance (NMR) and ³¹P NMR spectral analysis and energy dispersive spectroscopy (EDAX). Further, the effectiveness of the flame retardant behavior of the coatings was evaluated using the limiting oxygen index and UL-94 vertical burning test. Thermal stability was estimated from thermogravimetric analysis and differential scanning calorimetry. The effects of varying the concentration of TDSPBRD on the viscosity of the coating formulation along with the optical, mechanical and chemical resistance properties of the coatings were evaluated. The coatings gel content, water absorption behavior, and stain resistance were also studied.     

Antioxidant performance of mixed tocopherols in styrenic block copolymers

Mixed tocopherols (MT) containing a predominance of γ‐tocopherol were evaluated for antioxidant (AO) performance in polybutadiene‐ and polyisoprene‐based styrenic block copolymers (SBS and SIS, respectively) by using oxidative induction time as a measure of AO performance. A conventional hindered phenolic AO and α‐tocopherol (vitamin E) were evaluated in comparison. MT exhibited significantly higher performance than the controls in both SIS and SBS polymers. J. VINYL ADDIT. TECHNOL., 12:73–77, 2006. © 2006 Society of Plastics Engineers     

PF/PDMS-OH流变性能对其泡沫材料泡孔结构的影响

分别将质量分数为10%,15%和20%的端羟基聚硅氧烷(PDMS–OH)通过机械共混的方法改性酚醛树脂(PF),进而采用化学发泡的方法制备PF/PDMS–OH泡沫复合材料。采用旋转式流变仪表征共混体系的稳态及动态流变性能,研究黏弹性对树脂发泡过程的影响。傅立叶变换红外光谱表征PDMS–OH与树脂在固化过程中的化学反应。扫描电镜表征不同共混体系下泡孔的结构与形态。结果表明,加入15%PDMS–OH的共混体系具有最利于发泡成型的黏弹性,且可与PF形成化学交联作用,对PF泡沫的泡孔形态影响显著。同时红外表征显示,PDMS–OH与PF在固化过程中发生化学交联,这种互穿交联网状结构为PF及泡沫提供了更多稳定的柔性链段。