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Abstract  

The gelation of a powder coating and its matrix based on a saturated carboxyl functional polyester resin and triglycidyl isocyanurate of different diastereomer racemate composition was investigated by rotational viscometry. The iso-T cure diagrams have been determined directly by isothermal viscometric measurements and the gelation curves for the TTT-diagram have been constructed. To the measured section of the gelation curves power functions could be fitted and with their help the reactivity of the investigated systems were compared. The ratio of the two diastereomer racemates of TGIC has a significant effect on the reactivity of the coating, as it was also supported by DSC measurements. β-TGIC is of highest reactivity, and by increasing its ratio in TGIC, reactivity increases, and adversely effects the performance of the powder coating. Commercial TGIC-s have similar reactivity, comparable to that of high α-TGIC. The reactivity of the matrix is higher than that of the powder.

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Introduction Powder coatings are widely used in household appliances, automobiles, office accommodations, steels and architecture fields, due to their excellent advantages such as no volatile organic content, energy savings and

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Introduction Epoxy resins, namely diglycidyl ether bisphenol-A (DGEBA) and carboxylated polyester (CPE), are versatile materials used in powder coatings. Such powder coatings are called hybrid coatings, where they are

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Summary Thermogravimetry was used to study the kinetics of isothermal degradation of an epoxy thermoset powder coating in a nitrogen atmosphere and in oxidizing atmospheres of air and pure oxygen. An integral isoconversional procedure was used to analyse how the activation energy varies depending on the degree of conversion and depending on the atmospheres used. In the case of degradation in a nitrogen atmosphere, in addition to the activation energy, the kinetic triplet was completed using an Avrami reaction model and the pre-exponential factor. With this atmosphere, the conclusion was reached that the isothermal and non-isothermal kinetics are equivalent. It was shown that the thermooxidative degradation process is more complex and consists of a two-stage process. The first stage of degradation is similar whether nitrogen, oxygen or air are present. Chain scission occurs and it seems that there is formation of thermally more stable compounds. The second stage of degradation, involving several phenomena, occurs only in the presence of oxygen or air and leads to the total disappearance of the organic material by thermooxidation. These stages are very similar under non-isothermal or isothermal conditions.

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Abstract  

This paper presents DSC investigations on the curing kinetics of an epoxy-polyester (EP/PE) powder coating system with two different accelerators and on the crystallization behaviour of a semicrystalline thermoplastic containing regranulate. In addition thermal degradation and entropy relaxation effects of an amorphous, thermoplastic due to different injection moulding parameters are discussed. Thermogravimetry results are presented for quantitative analysis of rubber, and for elucidating problems which may arise during the injection moulding of thermoplastic regranulate which is obtained from painted rejects. The measurements were carried out using NETZSCH DSC 200 (heat flux DSC) and thermobalances TG 439 and TG 209.

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. Ramis , X , Salla , JM , Cadenato , A , Morancho , JM . Simulation of isothermal cure of a powder coating—non-isothermal DSC experiments . J Therm Anal Calorim . 2003 ; 72 : 707 – 718 . 10.1023/A:1024562607857

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Journal of Thermal Analysis and Calorimetry
Authors: Rogério L. Pagano, Verônica M. A. Calado, Frederico W. Tavares, and Evaristo C. Biscaia

. Ramis , X , Salla , JM , Cadenato , A et al. 2003 Simulation of isothermal cure of a powder coating—non-isothermal DSC experiments . J Therm Anal Calorim 72 : 707 – 718 10.1023/A:1024562607857 . 7

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0300-9440(02)00100-5 . 3. Johnson , LK , Sade , WT . New monomers for polyester. Powder coating resins . J Coat Technol . 1993 ; 65 : 19 – 26

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