Degradation profiles of polyester–urethane (hydroxylated polyester/diphenylmethane diisocyanate) and polyester–melamine (hydroxylated polyester/hexamethoxymethylmelamine) coatings: An accelerated weathering study

The successful material performance of coatings depends on the environmental conditions to which they are exposed. The effects of the diol structure and acetoacetylation on the weathering degradation of hydroxylated polyester (HP)/hexamethoxymethylmelamine and HP/diphenylmethane diisocyanate clear coatings were studied. The acetoacetylation of HPs led to better performance for higher application solids than the acetoacetylation of their base counterparts. Weathering degradation profiles were investigated with dynamic mechanical thermal analysis, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The structural variations of the building blocks and acetoacetylation were found to be important for enhancing the stability of coatings at higher application solids. Polyester–urethane coatings were more stable toward weathering than polyester–melamine coatings. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1069–1081, 2005     

Degradation profiles of polyester‐urethane (HP‐MDI) and polyester‐melamine (HP‐HMMM) coatings: A thermal study

This article investigates the effect of diol structure and acetoacetylation of the hydroxylated polyesters (HPs) on thermal stability and degradation profiles of HPs/hexamethoxymethylmelamine (HMMM) as well as HPs/diphenylmethane diisocyanate (MDI) high solids coatings (HSCs) by thermogravimetry. Thermal stability of HP‐MDI and HP‐HMMM coatings constitute the main focus of this investigation. It is found that variations in the constituent groups to synthesize HPs and acetoacetylation of HPs are important to achieve superior performance. Results of this study indicated a good thermal stability of coatings. However, not much variation in thermal stability was observed with the structural variations in HPs. Mathematical equations of Broido, Coats‐Redfern, and Chang were used to evaluate the kinetic parameters. Activation energy was found to be dependent on the kinetic methods used. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 518–526, 2005     

Hybrid polymer networks of unsaturated polyester–urethane as composite matrices for jute reinforcement

Reactions of unsaturated polyester resin and 4,4′ diphenyl methane diisocyanate were carried out at different NCO/OH ratios in presence of catalysts to form the hybrid polymer networks. Chain extender (1,4 butanediol) added in the hybrid network (NCO/OH ratio: 0.76) was optimized at a level of ～ 3 wt % only of the polyester resin. The curing of these networks was studied by a rigid body pendulum type (RPT) method in terms of reduced damping ratio and increased frequency. Lack of multiple glass transition temperatures, sharp Tan delta peak, and particulate composite type morphology clearly demonstrated the formation of phase mixed domains in the hybrid networks. The storage modulus and loss modulus master curves obtained by dynamic mechanical analysis indicate that hybrid polymer networks retained higher modulus at lower and intermediate frequencies over the polyester resin showing their superior time‐dependent response. Efficacy of these hybrid network resins was examined as matrices in the jute composites and compared with those of polyester resin and unsaturated polyester–polyurethane interpenetrating network matrices. It is found that the hybrid polymer network matrix composites exhibited superior physicomechanical properties under both dry and boiling water age test. Fractographic evidences such as fiber–matrix adhesion, hackle markings, and fiber breakage also supported their superior behavior over other composite matrices. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fire behaviour of polyester–clay nanocomposites

The aim of this study was on the one hand, to compare the fire behaviour of polyester/clay nanocomposites with that of the neat polymers added with the conventional flame retardant melamine isocyanurate (MIC) and on the other hand, to study the effect of the flame retardant added to the nanocomposites. Polyester/clay nanocomposites were prepared by using polybutylene terephthalate (PBT) and a co‐polyester elastomer as polymeric matrices and a commercial organoclay as filler. As verified by X‐ray diffractometry (XRD) and transmission electron microscopy (TEM) intercalated structures were obtained by mixing the molten polymer with the layered silicate in a corotating twin screw extruder. The fire behaviour of these materials was investigated by means of an oxygen consumption calorimetry (Cone Calorimeter). Peak heat release rate of 3‐mm thick samples measured at 50 kW/m² external heat flux was reduced by a factor of 2–3 by the addition of organically modified montmorillonite to the polymers. The further addition of MIC did not give a significant improvement in the behaviour of the materials. Copyright © 2005 John Wiley & Sons, Ltd.     

Confocal Raman microscopy study of the melamine distribution in polyester–melamine coil coating

Hexamethoxymethylmelamine, a common crosslinker used in combination with polyester resins to prepare thermosetting coatings, can self-condense during curing and in theory build up regions with high crosslink density (melamine enrichment). This distribution may affect such properties as the “local” glass transition temperature and structural heterogeneity and thereby modify formability, stain resistance, and weatherability. The self-condensation regions have not previously been observed in detail so their distribution in the film is unclear. Confocal Raman microscopy (CRM) has been used to characterize the melamine distribution in three polyester–melamine paint systems: one clear and two pigmented coil coatings. Both the surface mapping and depth profiling features of CRM were used to perform a 3D analysis. The depth profiling of the clear coating was performed in a nondestructive way, but due to the opaque nature of the pigments, cross sections of the pigmented coatings were prepared in order to facilitate the analysis of the melamine distribution through the film thickness. Melamine-enriched zones were found on the surfaces of all three samples. They appeared to be approximately spherical with diameters of around 5 μm. It was also observed from the cross sections that the melamine-enriched zones appeared as “particles” distributed randomly through the coating. The Raman spectra collected at these regions show significantly higher triazine ring band intensity. All of these findings confirm the hypotheses constructed over the past 20–30 years. This paper was awarded Second Place in the 2008 FSCT Roon Awards competition held as part of the FutureCoat! conference sponsored by the Federation of Societies for Coatings Technology, in Chicago, IL, on October 14–16, 2008.     

An investigation on the melamine self-condensation in polyester/melamine organic coating

Melamine is a common crosslinker widely used in the coil coating industry to crosslink hydroxyl functional polyesters. Theoretically, melamine can also self-condense with the consequence regions with higher crosslink density build up in the coating. Although the melamine self-condensation has been studied, most of works were based on melamine segregation on the coating surface; the existence of melamine self-condensation has only been modelled rather than observed. Utilising confocal Raman microscopy and nanoindentation, the regions with higher melamine concentration were clearly observed and characterised for the first time.     

Micromechanisms of high-energy peel failure in polyester–aluminum–polyester laminates

Symmetrical polyester-aluminum-polyester laminates are prepared using poly(ethylene terephthalate) film subjected to a glow discharge pretreatment. Extremely high peel energies (several hundred J m^?2) are achieved, and the fracture path is principally cohesive: the laminate performance thus fully exploits the bulk mechanical properties of the PET. The peel surface exhibits extensive plasticity on a scale of tens of microns, with finer ductile tearing on a scale of order 1 μm. The mechanism of peel propagation and energy dissipation is discussed with regard to the optimisation of peel strength.     

Study on the enzymatic degradation of aliphatic polyester–PBS and its copolymers

The catalytic degradation of prepared matrix poly(butylene succinate) (PBS) and its copolymers by immobilized lipase is carried out in the mixed organic solvent containing a small amount of water. The degradation products were studied with various characterizations techniques, including gel permeation chromatography (GPC), time of flight mass spectrum (TOF‐MS), nuclear magnetic resonance (NMR), and Fourier transform‐infrared spectroscopy (FT‐IR). The results showed that under atmospheric pressure, 60°C, after 24 h catalytic degradation of PBS and its copolymers by immobilized lipase, the yellow oil‐like degradation products can be obtained. The lipase has catalytic activity on various copolymers. At the first time, the monomer of BDO was found in the degradation products and the molecular weight of product with aromatic smell is below 1000. The products consisted of cyclic oligomer, linear oligomer and monomers, and cyclic oligomer is at least dimmer. The minimum and maximum degradation yields correspond to PBS (40%) and P(BS‐co‐CL‐co‐CHDM) (54%). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermochemical and isoconversional kinetic analysis of a polyester–epoxy hybrid powder coating resin for wood based panel finishing

Powder coating is an established technology especially for the surface finishing of metallic substrates for example in the automotive industry. Moreover, powder technology holds also great promises for the coating of non-conventional substrates like plastics or wood due to the lack of solvents and good recoverability. Here, low-temperature curing resins are required and especially mild processing conditions are demanded by the substrates. Advanced characterization methods need to be established that allow the precise balancing of the processing conditions required for adequate melting, flowing and curing of the powder with the process conditions that can be tolerated by the temperature-sensitive substrates. In the present contribution it is shown that differential scanning calorimetry (DSC) in combination with isoconversional kinetic analysis (ICKA) provides great potential for this purpose. DSC is a standard thermo-chemical method that can be successfully used to study both the melting and curing processes of powder coatings and to determine, for example the glass transition temperature of the cured coating directly from the measured thermograms. However, still more information can be extracted from the enthalpy signals when more sophisticated methods of data post-treatment and analysis are employed. Isoconversional kinetic analysis techniques such as the Kissinger–Akahira–Sunose (KAS) or the advanced Vyazovkin (VA) approaches allow calculating the time-dependencies of physical and chemical processes at various temperatures based on the estimates of activation energies which are obtained from DSC raw data. These analyses allow for example to calculate the time required for a certain degree of cross-linking in the coating after processing the coating under specified curing conditions. In the present contribution the application of ICKA of DSC measurements for the analysis of the flowing and curing behaviour of a powder coating based on a polyester–epoxy hybrid resin is illustrated and the potential of this approach to predict optimal curing times for arbitrary curing temperatures is demonstrated. This is especially useful when temperature-sensitive substrates like wood-based panels are coated. Additionally, the potential to relate the thermo-chemical properties of the powder coating to the surface properties of the coated substrates is discussed.     

Effect of the nanoclay types on the rheological response of unsaturated polyester–clay nanocomposites

The rheological behavior of styrene‐free unsaturated polyester resin–nanoclay (Cloisite 15A and 30B) nanocomposites at various nanoclay contents prepared by melt mixing was investigated. To investigate the effect of shear and diffusion induced phenomena as well as nanoclay surface modification on the rheological behavior, samples were prepared at two different temperatures of 40°C (cold mixed) and 150°C (hot mixed) and tested in a range of 40–120°C using dynamic rheometry. Viscosity–temperature curves for the cold mixed samples showed a decrease in viscosity with increasing temperature followed by the formation of a plateau with onset temperature which depends on the nanoclay type and content. The results of small angle X‐ray scattering and transmission electron microscopy analysis were in agreement with the formation of a physical network in which nanoclay particles act as the nodes, whereas polymer chains serve as the links. It is believed that for the cold‐mixed samples, higher shear forces break the nanoclay stacks associations efficiently, and hence more nanoparticles are available for polymer chains to form the network. In this context, the initial d‐spacing was much more effective than the nanoclay modification type. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers.     

Preparation and properties of unsaturated polyester–montmorillonite intercalated hybrid

An unsaturated polyester–organophilic montmorillonite hybrid was prepared by dispersing polymerizable quaternary ammonium‐modified montmorillonite in an unsaturated polyester resin, followed by cross‐linking reaction. The purpose of this investigation was to discover the role of the polymerizable group of quaternary ammonium in improving interfacial interaction between the silicate layers and polymer chains and the mechanical properties of unsaturated polyester–montmorillonite hybrids. It is found that when the content of organophilic montmorillonite is between 2 and 5%, the tensile strength, impact strength, heat resistance, and swelling resistance of the hybrid are obviously enhanced and are better than that of the composites prepared with pristine or nonpolymerizable quaternary ammonium‐modified montmorillonite. Results of X‐ray diffraction and transmission electron microscopy show that unsaturated polyester and styrene in the resin can be intercalated into the interlayer space of organophilic montmorillonites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2038–2044, 2004     

Thermal degradation study of fire resistive coating containing melamine polyphosphate and dipentaerythritol

A melamine polyphosphate (MPP)/dipentaerythritol (DPER) mixture was used as fire retardant additives for preparing waterborne intumescent fire resistive coating. The thermal degradation of the MPP/DPER mixture and of the coating was studied by TGA and FTIR. The resulting char of the coating was investigated by XPS, SEM and energy dispersive spectroscopy (EDS). The results showed that the thermal degradation behavior of the MPP/DPER mixture was similar to that of the coating. They decomposed to nonflammable gases, and formed intumescent char layer containing phosphorus oxide at high temperature. The EDS results proved that the resulting char was gradually oxidized with the temperature increase. The SEM micrographs showed that the average cell size of the char layers became bigger and the cell size distribution became wider as the temperature increased from 500 °C to 800 °C, and this non-uniform char layer could damage the fire protection of the coating.     

Thermal degradation study of fire resistive coating containing melamine polyphosphate and dipentaerythritol

A melamine polyphosphate (MPP)/dipentaerythritol (DPER) mixture was used as fire retardant additives for preparing waterborne intumescent fire resistive coating. The thermal degradation of the MPP/DPER mixture and of the coating was studied by TGA and FTIR. The resulting char of the coating was investigated by XPS, SEM and energy dispersive spectroscopy (EDS). The results showed that the thermal degradation behavior of the MPP/DPER mixture was similar to that of the coating. They decomposed to nonflammable gases, and formed intumescent char layer containing phosphorus oxide at high temperature. The EDS results proved that the resulting char was gradually oxidized with the temperature increase. The SEM micrographs showed that the average cell size of the char layers became bigger and the cell size distribution became wider as the temperature increased from 500 °C to 800 °C, and this non-uniform char layer could damage the fire protection of the coating.     

Effect of drug loading on the properties of temperature‐responsive polyester–poly(ethylene glycol)–polyester hydrogels

Hydrogels that can undergo gelation upon injection in vivo are promising systems for the site‐specific delivery of drugs. In particular, some thermo‐responsive gels require no chemical additives but simply gel in response to a change from a lower temperature to physiological temperature (37 °C). The gelation mechanism does not involve covalent bonds, and it is possible that incorporation of drugs into the hydrogel could disrupt gelation. We investigated the incorporation of drugs into thermo‐responsive hydrogels based on poly(?‐caprolactone‐co‐lactide)‐block‐poly(ethylene glycol)‐block‐poly(?‐caprolactone‐co‐lactide) (PCLA–PEG–PCLA). Significant differences in properties and in the response to incorporation of the anti‐inflammatory drug celecoxib (CXB) were observed as the PEG block length was varied from 1500 to 3000 g mol^?1. Linear viscoelastic moduli of a PCLA–PEG–PCLA hydrogel containing a 2000 g mol^?1 PEG block were least affected by the incorporation of CXB and this gel also exhibited the slowest release of CXB, so the incorporation of phenylbutazone, methotrexate, ibuprofen, diclofenac and etodolac was also investigated for this hydrogel. Different drugs resulted in varying degrees of syneresis of the hydrogels, suggesting that they interact with the polymer networks in different ways. In addition, the drugs had varying effects on the viscoelastic and compressive moduli of the gels. The results showed that the effects of drug loading on the properties of thermo‐responsive hydrogels can be substantial and depend on the drug. For applications such as intra‐articular drug delivery, in which the mechanical properties of the hydrogel are important, these effects should thus be studied on a case‐by‐case basis. © 2019 Society of Chemical Industry     

Simplification and application of single fiber fragmentation test on silylated polyester–glass fiber composites

Single fiber fragmentation test (SFFT) was used to investigate the interfacial adhesion in glass fiber‐unsaturated polyester composites. A simplified approach was developed for SFFT based on determination of the maximum number of fragments on the fiber at the end of the test. This approach does not involve length measurements and shortens the experiment time to a few minutes. By using a digital camera attached to the microscope, photographs of the coupon were taken during the test, and the number of fragments within the gauge length were counted later. This method allows quick, quantitative comparison of different fibers and matrices. The test samples were prepared by using commercial polyester resin and E‐glass fibers having different commercial sizings. SFFT results were in excellent agreement with the macromechanical test done on samples prepared with the same glass fiber and same polyester. The crack modes and debonding phenomena were examined from the microscopic images. Atomic force microscopic (AFM) images of the fiber were examined to get detailed topographic information about fiber surfaces. To improve interfacial adhesion, commercial unsaturated polyester was reacted with 3‐aminopropyltriethoxy silane via Michael Addition reaction on the maleate double bonds of the polyester. The resulting silylated polyester was characterized by H¹ NMR spectroscopy. The results of SFFT showed that the maximum numbers of fragments increased 23% on using silylated polyester. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A systematic study on the effects of doping agents on polypyrrole coating of fabrics

Polypyrrole is widely used as coating to produce electrically conductive textiles. Counter‐ions (i.e. doping agents) were embedded in polypyrrole to improve electrical conductivity. Good electrical performances are required for several applications, such as microwave attenuation/electro‐magnetic interference shielding, heat generation, electro‐static discharge protection, sensing, and energy storage. In this work, a systematic study was carried out on the effects of doping agents in coating cotton fabrics with a thin polypyrrole layer. A total of 11 compounds were selected and compared as counter‐ions. The electrical performances of the coated fabrics were assessed with measures of electrical conductivity. Moreover, evenness and morphology of the resulting polypyrrole layer were discussed. As the final result, the best performances in terms of electrical conductivity (i.e. low surface resistivity) were measured using on dicyclohexyl sulfosuccinate, 2,6‐naphthalenedisulfonate or 1,5‐naphthalenedisulfonate as doping agents. The weight increases after polypyrrole deposition on the fabrics were greater than 15% and polypyrrole deposited on the fibers as a uniform film. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42831.     

Use of hygrothermal decomposed polyester–urethane waste for the impact modification of epoxy resins

Hygrothermally decomposed polyurethane (HD‐PUR) of a polyester type was used as an impact modifier in tri‐ and tetrafunctional epoxy (EP) resins. Between 5 and 80 wt % of the PUR modifier was added to the EP prior to its crosslinking with a diamine compound (diaminodiphenyl sulfone, DDS). The mean molecular weight between crosslinks (M_c ) was determined from the rubbery plateau modulus of the dynamic mechanical thermal analysis (DMTA) spectra. The fracture toughness (K_c) and energy (G_c) of the modified resins were determined on static‐loaded compact tension (CT) specimens at ambient temperature. The change in the K_c and G_c as a function of M_c followed the prediction of the rubber elasticity theory. The efficiency of the HD‐PUR modifier was compared with that of a carboxyl‐terminated liquid nitrile rubber (CTBN). Attempts were also made to improve the functionality of the modifier by hygrothermal decomposition of PUR in the presence of glycine and ε‐caprolactam, respectively. DMTA and fractographic results showed that HD‐PUR functions as an active diluent and a phase‐separating additive at the same time. As HD‐PUR can be regarded as an amine‐functionalized rubber, it was used as the hardener (by replacing DDS) in some EP formulations. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1139–1151, 2000     

Exhaust dyeing of polyester‐based textiles using high‐temperature–alkaline conditions

The factors affecting the dyeability of polyester‐based textiles with disperse dyes in an alkaline medium were studied. It was found, for a given set of dyeing conditions, that (a) the appropriate conditions for attaining a higher color yield were 45 min at 130°C with pH 9 using a material‐to‐liquor ratio of 1/10; (b) increasing the Diaserver® AD‐95 concentration to 2% ows (based on weight of substrate) as well as including triethanolamine to 2% ows in the dyeing formulations bring about a significant improvement in the dye uptake; (c) both a preheat setting from 160 to 200°C/30 s and an alkaline weight reduction have a positive impact on postdyeing with the used disperse dye; (d) the extent of dye uptake as well as the color strength are governed by the type of substrate, that is, knitted fabric > spun yarn > woven fabric, nature of the dye stabilizer, that is, EDTA > Diaserver® AD‐95 > Tinoclorite® CBB > citric acid > none, as well as kind of the disperse dye; (e) direct reuse of the disperse dyebaths, without reconstitution, in the dyeing of the used substrates was shown to be feasible in a single shade and in the reverse‐order dyeings (dark → light); (f) one‐bath, one‐step exhaust dyeing of polyester/cotton‐knitted fabric using selected disperse reactive dyes combinations under high‐temperature alkaline conditions is feasible; and (g) the color and fastness properties of the resultant dyeings depend on the type of the used auxiliaries, in addition to the nature of disperse/reactive dyes combinations as well as compatibility with other ingredients. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3563–3573, 2003     

Blends of liquid crystalline polyester–polyurethane and epoxy: Preparation and properties

A novel liquid crystalline polyester–polyurethane (LCPU) that contains polyester mesogenic units was synthesized in the present work. Through a careful investigation of the structure and morphology of the LCPU, it was found that the home‐synthesized LCPU is a highly birefringent thermotropic nematic liquid crystal. After being blended with bisphenol‐A epoxy, the liquid crystalline polymer can, simultaneously, improve the impact strength and the glass transition temperature as well as the tensile strength and the tensile modulus of the blends. It was proved to be an efficient toughening agent for epoxy without the expense of other properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 783–787, 2003