Cycloaliphatic Polyesters Research Articles

Ultraviolet-Curable Cycloaliphatic Polyesters Containing Spiroacetal Moieties for Application as Powder Coatings

Ultraviolet-Curable Cycloaliphatic Polyesters Containing Spiroacetal Moieties for Application as Powder Coatings

Synthesis and properties of UV-curable polyurethane acrylates based on different polyols for coating of metal sheets

ABSTRACTThe UV-curable coatings are emerging as new environmental friendly coating technology for replacement of solvent-based ones. UV-curable polyurethane acrylate oligomers were newly synthesized using cycloaliphatic polyisocyanate and polycaprolactone polyol, polycarbonate polyol or cycloaliphatic polyester polyol, and their cured properties were investigated by differential scanning calorimeter, thermogravimetric analysis and dynamic mechanical analysis. The results showed that the cycloaliphatic polyester polyol-based film showed better properties on UV resistance, accelerated weathering, water resistance and chemical resistance. It might be attributed to its unique structure with 1,4‐substitution.

Visible light cure characteristics of a cycloaliphatic polyester dimethacrylate alternative oligomer to bisGMA

Objective: The goal of this study was to characterize the light curing characteristics of a new oligomer PEM-665 designed to be used as an alternative monomer to BisGMA.Materials and methods: PEM-665 (P) and BisGMA (B) solutions were prepared with triethylene glycol dimethacrylate (T) diluent in different weight proportions (70/30 and 50/50). Solutions containing 70% P and 30% T were designated as 70PT, 70%B and 30%T as 70BT, 50%P and 50%T as 50PT and 50%B and 50%T as 50BT. The initiators were CQ (EDMAB was used as amine accelerator for CQ) and DPO in 1% concentration. Eight solutions were prepared in a factorial design: 70PT/DPO; 70PT/CQ; 50PT/DPO; 50PT/CQ; 70BT/DPO; 70BT/CQ; 50BT/DPO; 50BT/CQ. BISCO VIP visible light was used to cure the monomer solutions using 30 s exposure time and 400 W power setting. TA Instruments Differential Scanning Calorimeter (DSC 2910) was used to determine the heat of cure (J/g) during polymerization at 37 °C, from which molar heat of cure (kJ/mole) and %Conversion values were estimated.Results: Range of mean values as a function monomer selections were: heat of cure (J/g): 161.7 for 70PT/DPO system to 198.6 for 50BT/CQ system; molar heat of cure (kJ/mole): 67.3 for 70BT/DPO to 78.86 for 50PT/CQ; % conversion: 59.9 for 70BT/DPO to 70.3 for 50PT/CQ. Analysis of variance and Tukey HSD pairwise contrast showed statistically significant differences between % conversion means of PEM and BisGMA mixtures, with PEM mixtures showing significantly higher mean values.Conclusions: The results suggest that PEM-665 is a promising candidate material for dental polymer applications.

The use of anhydride linkages to increase the glass transition temperatures of polymers containing carboxyl end groups: A perspective in powder coatings

A method to increase the glass transition temperature of carboxyl terminated low molecular weight cycloaliphatic polyesters through anhydride linkages is described. Low molecular weight carboxyl terminated cycloaliphatic polyesters, poly(1,4-cyclohexylidenecyclohexane-1,4-dicarboxylate) (PCCD), were synthesized by the polycondensation reaction of cis/trans-1,4-cyclohexane dicarboxylic acid and cis/trans-1,4-cyclohexane dimethanol. The corresponding poly(ester-anhydrides)s were obtained using a mixed anhydride method in melt where the low molecular weight carboxyl terminated cycloaliphatic polyesters were chain extended at the terminal carboxylic acid end groups through reversible anhydride linkages. The poly(ester-anhydrides)s as expected had higher glass transition temperature than the corresponding parent oligomers. PCCD oligomers with no anhydride linkages and PCCD based poly(ester-anhydrides)s with anhydride linkages at comparable molecular weights, had similar glass transition temperatures. However, the latter potentially offer higher reactive group concentration thanks to the reactive anhydride groups. This work was carried out as a proof of concept to show that the glass transition temperature of carboxyl terminated oligomers can be increased by increasing the molecular weight but without sacrificing the reactive group concentration. This approach, the authors suggest, may potentially be used in the design of new carboxyl functional base resins, especially for powder coatings, where both the acid number and glass transition temperature are important.

Nanostructured polyurethane ceramer coatings for aircraft

A new low VOC (volatile organic compounds) polyurethane/oligosiloxane coating was formulated using 1,6-hexamethylene diisocyanate (HDI) isocyanurate, alkoxysilane-functionalized HDI isocyanurate, tetraethyl orthosilicate (TEOS) oligomers, and three cycloaliphatic polyesters. One series of polyesters was synthesized using 1,4-cyclohexanedimethanol (CHDM) with 1,4-cyclohexanedicarboxylic acid (1,4-CHDA) and 1,3-cyclohexanedicarboxylic acid (1,3-CHDA). A second series of polyesters was synthesized using 2-butyl-2-ethyl-1,3-propanediol (BEPD) with 1,4-CHDA or 1,4-CHDA, and 1,3-CHDA, respectively. The polyurethane provided the general mechanical properties and the polysiloxane functioned as an adhesion promoter and corrosion inhibitor. The continuous organic polyurethane phase was coupled with the inorganic polysiloxane phase via the alkoxysilane-functionalized HDI isocyanurate. The general coatings, tensile, and viscoelastic properties were evaluated for the ceramer coatings as functions of the polyester and concentration of TEOS oligomers. Damage tolerance was evaluated via fracture toughness and development of the film deformation zone prior to crack propagation. The coatings’ properties were dominated by the organic phase. The film morphology was investigated using the combination of SEM (scanning electron microscope) and X-ray analysis. Phase separation was observed for ceramer coatings resulting in SiO2 particles. The size of the preceramic silicon-oxo-particles was controlled by the Tg of the organic phase and the concentration of TEOS oligomers.

Polyurethane/Polysiloxane Ceramer Coatings: Evaluation of Corrosion Protection

A series of polyurea and polyurethane ceramer coatings were formulated using hexamethylene diisocyanate (HDI) isocyanurate, alkoxysilane-functionalized HDI isocyanurate, tetraethyl orthosilicate (TEOS) oligomers and cycloaliphatic polyesters. The coatings were prepared as a function of alkoxysilane-functionalized HDI isocyanurate and TEOS oligomers concentration. Also, the effect of acid catalyst was investigated. The corrosion resistance of polyurea or polyurethane ceramer coating systems were evaluated using a prohesion chamber on aluminium alloy 2024-T3 substrate. The polyurethane ceramer coatings were compared with the chromate pretreatment and the epoxy-polyamide primer containing the chromate pigment. In addition to prohesion, the interface between the coating and substrate was characterized using X-ray photoelectron spectroscopy (XPS). The prohesion data showed that the corrosion was inhibited by the TEOS oligomers. However, high concentrations of TEOS oligomers and acid catalyst produced blistering in the polyurea/polysiloxane ceramer coatings. The prohesion data also showed that the corrosion protection of ceramer coatings performed as well as the chromate pretreatment and competitively with the epoxy primer. From the XPS and prohesion data, a self assembling silicon oxide layer at the metal-coating interface was proposed.

Cycloaliphatic polyester based high solids polyurethane coatings: I. The effect of difunctional alcohols

High-solids polyesters were synthesized with two cycloaliphatic diacids, 1,4- cyclohexanedicarboxylic acid (1,4-CHDA) and 1,3-cyclohexanedicarboxylic acid (1,3-CHDA); and with five diols, 1,4-cyclohexanedimethanol (CHDM), neopentyl glycol (NPG), hydroxypivalyl hydroxypivalate (HPHP), 2-butyl-2-ethyl-1, 3-propanediol (BEPD), and 1,6-hexanediol (HD). The viscosity of the polyesters was dependent on the structures of diols. The viscosity of polyesters is lower with the diol HD, intermediate with BEPD and HPHP, and higher with the diols CHDM and NPG. The polyesters were crosslinked with hexamethylene diisocyanate isocyanurate (HDI isocyanurate) affording polyurethane coatings. The mechanical properties, tensile properties, fracture toughness, and viscoelastic properties were investigated for the polyurethane films with five different diols. The cyclohexyl structure of the CHDM provides the polyurethane with rigidity which is manifested in high tensile modulus, hardness, and fracture toughness. In contrast, the linear diol, 1,6-hexanediol provides polyurethane with very high flexibility, but these coatings suffer with respect to low hardness and tensile modulus.

Synthesis and characterization of semicrystalline cycloaliphatic polyester/poly(dimethylsiloxane) segmented copolymers

High molecular weight poly(dimethylsiloxane)/semicrystalline cycloaliphatic polyester segmented copolymers based on dimethyl-1,4-cyclohexane dicarboxylate were prepared and characterized. The copolymers were synthesized using a high trans content isomer that afforded semicrystalline morphologies. Aminopropyl-terminated poly(dimethylsiloxane) (PDMS) oligomers of controlled molecular weight were synthesized, end capped with excess diester to form a diester-terminated oligomer, and incorporated via melt transesterification step reaction copolymerization. The molecular weight of the polysiloxane and chemical composition of the copolymer were systematically varied. The polysiloxane segment was efficiently incorporated into the copolymers via an amide link and its structure was unaffected by low concentrations of titanate transesterification catalyst, as shown by control melt experiments. The homopolymer and copolymers were characterized by solution, thermal, mechanical, and surface techniques. The segmented copolymers were microphase separated as determined by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and by transmission electron microscopy (TEM). It was demonstrated that relatively short poly(dimethylsiloxane) segment lengths and compositions were required to maintain single phase melt polymerization conditions. This was, in fact, the key to the successful preparation of these materials. The copolymers derived from short poly(dimethylsiloxane) segments demonstrated good mechanical properties, melt viscosities representative of single phase polymer melts, and were easily compression molded into films. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3495–3506, 1997

Recent advances in the use of star polymers in coatings

The synthesis of methacrylate stars by an arm-first process using ethylene glycol dimethacrylate as the core-forming material is described. The level of free arm is an indicator for the extent of termination during the preparation. Using 0.2% (mole basis) of catalyst on initiator instead of higher concentration is helpful. Modifiers for the anion catalyst used in group transfer polymerization (GTP) can be used to reduce termination. Clarity of the two-phase blends with polyester polyol and isocyanate crosslinking agent depended on star composition, hydroxyl-number (OH#) and star level. Recently, benzyl methacrylate has been introduced into this technology to give improved film hardness and clarity with cycloaliphatic polyester coreactants. This permits use of 25–30% star to give fast dry and improved hardness/flexibility balance while also allowing the application at less than 3.5 Ib/gallon of solvent.

Effects of orientation on the mechanical and dielectric relaxation behavior of cycloaliphatic polyester networks

AbstractThe mechanical and dielectric relaxation behavior of strained and unstrained networks, prepared from hydroxyl‐terminated poly(diethylene glycol‐trans‐1,4‐cyclohexane dicarboxylate) (PDGC), is studied over a wide interval of frequencies and temperatures. The mechanical relaxation spectrum exhibits a glass‐rubber absorption, designated β, located in the vicinity of 0°C at 0.1 Hz, followed by a β relaxation which appears to be the result of two overlapping peaks centered at −80°C (β1) and −110°C(β2). These two peaks coalesce into a single peak in the case of strained networks. The dielectric relaxation spectrum also exhibits an α absorption followed by a subglass β relaxation whose width decreases as the elongation ratio λ increases. The activation energy associated with the mechanical β1 appears to increase as λ increases. However, the activation energy of the dielectric β process does not show a clear dependence on the elongation ratio. The analysis of the conformational characteristics of PDGC chains indicates that rotational transitions through the CcyC* bonds of the acid residue would give rise to high dielectric activity. Conformational changes about the CH2CH2 bonds of the glycol residue would produce significant mechanical activity but, comparatively, low dielectric activity. The glass‐rubber absorption is slightly displaced toward the high‐temperature side as the elongation ration increases, suggesting that the entropic effects overcome the volume effects. The glass‐rubber transition is interpreted in terms of the free volume theory.

Influence of the acid residue on the polarity of cycloaliphatic polyesters

Preparation et determination du moment dipolaire du polyadipate de cyclohexanedimethylene-1,4 cis et trans et du polysuccinate de cyclohexanedimethylene-1,4 trans dans le dioxane et le benzene en fonction de la temperature. Comparaison avec les calculs d'energie conformationnelle obtenus avec le modele RIS pour les motifs ester

Birefringence, thermoelastic, and dielectric studies on cycloaliphatic polyesters

Birefringence, thermoelastic, and dielectric studies on cycloaliphatic polyesters

Mechanical and dielectric relaxations in cycloaliphatic polyester networks

Mechanical and dielectric relaxations in cycloaliphatic polyester networks

Stress‐optical behavior of cycloaliphatic polyesters

AbstractStress‐strain‐birefringence measurements were carried out on elastomeric networks of poly(oxymethylene‐1,4‐cis‐cyclohexylenemethyleneoxysebacoyl) at several temperatures between 5 and 80°C. The dependence of both the birefringence Δn and the true stress f/A on temperature was found to be linear for T > 30°C; for T < 30°C an anomalous increase in the birefringence and a sharp decrease in the stress was observed. This behavior suggests that crystallinity is developed in the strained networks at low temperatures, and the crystallites are oriented in the direction of the elongation. Values of the optical configuration parameter Δa ranged from 9.15 to 8.28 in units of 1024 cm3 in the temperature range studied. The value at 40°C of 1024Δa, obtained from experiments performed on swollen networks, amounted to 7.47 cm3. These results suggest that intermolecular interactions enhance the birefringence of the strained networks. The quantities Δa and d In Δa/dT were calculated by using the valence optical scheme. Although the calculations reproduce the temperature coefficient fairly well, the theoretical values of Δa are smaller than the experimental ones. The agreement between theory and experiment is better assuming that the CH2CH2COOCH2 segment is freely rotating.