DIFFERENTIAL SCANNING CALORIMETRY OF ULTRAMID PLASTIC MATERIAL

Transcription

1 DIFFERENTIAL SCANNING CALORIMETRY OF ULTRAMID PLASTIC MATERIAL Dumitru Nedelcu 1, Nicoleta Monica Lohan 2, Ciprian Ciofu 1, Constantin Carausu 1 1 Gheorghe Asachi Technical University of Iasi, Department of Machine Manufacturing Technologies, Blvd. Mangeron, No. 59A, Iasi, Romania, Tel-Fax: , 2 Gheorghe Asachi Technical University of Iasi, Faculty of Materials Science and Engineering, Corresponding author: Dumitru Nedelcu, dnedelcu@tcm.tuiasi.ro Abstract: The Differential scanning calorimetry (DSC) is a commonly used method for thermal studying of polymers [1, 2] it allows to highlight the changes that occur with the polymer being subjected to a controlled temperature program (heating - keeping - cooling). The use of DSC may be provided with information about the temperature at which the phase changes occur, such as the glass transformation temperature, melting temperature, crystallization temperature [3], but can be determined and appropriate processing enthalpy, entropy changes or modifications the specific heat or the latent heat. The advantage of DSC analysis compared to others thermal analysis techniques is the high speed range for heating, cooling, respectively, that can be used [2]. The glass transition temperature is one of the most important thermal processing that occurs in heating a polymer and a corresponding transition of the amorphous glassy phase during high - elastic. When a polymer undergoes a glass transition some plastics and mechanical properties change rapidly [1, 4]. The DSC curve shows a glass transition slope endothermic low intensity. DSC analysis allows us to identify from thermogram obtained of glasss transition temperature (inflection point) (Tg), temperature of the beginning and end of transformation and change of specific heat (ΔCp ). This paper aims to highlight the behavior of glass transition using DSC analysis, the transformation that occurs during heating of the two polymers (Ultramid A3EG5, Ultramid A3EG6) obtained using three injection angles: 0 o, 45 o and 90 o. Key words: Calorimetry, Injection, Ultramid Plastic Materials Introduction Calorimetry has played a very important role in research since the 20 th century, being used is various fields such as: physics, chemistry, science and materials technology. Its applicability has also extended to other fields, such as nano-thermodynamics and bio-thermodynamics, [5]. Differential scanning calorimetry (DSC) measures the amount of heat absorbed/dissipated by a test sample as compared to a reference value, when the test sample is subjected to a heating and/or cooling cycle. The calorimetric effect may be revealed by the temperature- and/or time-dependent heat flow variation, and its evaluation makes sense when particular heat flow variations, specific to the various transformations accompanying temperature variation, occur. 2-69

2 These may take the form of exothermal peaks, which mark increases of the amount of absorbed heat, or of endothermal minimums, which mark the dissipation of an amount of heat. These may be attributed to solid state transformations, like for instance direct and reversed martensitic transformation of a shape-memory material, [6]. The calorimetric effect may also refer to an endothermal stage marking the glass transition of an amorphous material, [7, 8]. Methodology and Experimental The planning of the experiments was achieved by means of the Taguchi methodology, [9]. The model proposed by Viger and Sisson is also easy to study; this is the matrix model of the system comprising I factors: F 1, F 2... F i each factor having n i levels. Each experiment was conducted three times. The proposed matrix model takes into consideration six technological parameters with two levels. The coefficients of a type (1) model were determined within the experimental research: Z t =M+ T top + t inj + t r + S s + P inj + T mat + P inj T top + P inj t inj + P inj t r + P inj S s + P inj T mat (1) where: M-general average; T top -melting temperature, [ o C]; t inj -injection time, [s], t r - cooling time, [s], S s -screw speed, [mm], P inj -injection pressure, [MPa], T mat -matrix temperature, [ o C]. The figure 1 presents the sample dimensions according to the recommendation of DIN EN ISO 527-1/1A/5. Fig. 1. Sample dimensions The fibers orientation will be in three directions for samples obtained, such as: 0 o, 45 o and 90 o (figure 2). In order to achieve the DSC experiments were removed by 3 pieces of each specimen (Ultramid A3EG5, Ultramid A3EG6) obtained using the three angles of injection, all the samples having mass less than 50mg. The experiments were performed on differential scanning calorimeter (DSC) F3 Maia type (supplied by NETZSCH) in a protective atmosphere of argon. The features of DSC F3 Maia calorimeter used are: temperature range ( ) C; heating rate ( )K/min; the cooling rate of ( )K/min; temperature precision 0.1 K; sensitivity <1μW; determining the enthalpy accuracy ± 0.5 %. The device was calibrated according to standards, Bi, In, Sn and Zn. Samples were heated from room temperature to 200 C at a heating rate of 10K/min, followed by free cooling to room temperature. The DSC thermograms were recorded during the heating program was evaluated by Proteus. 2-70

3 Fig. 2. Fibers orientation Results and Discussion DSC curves occurring during the heating to a temperature of 200 C are shown in the following figures. Thus, Figure 3 presents the variation of heat flux with temperature for sample Ultramid A3EG5 for the three injection angles: 0 o, 45 o and 90 o. 2-71

4 Fig.3 DSC curves recorded during heating the sample Ultramid A3EG5: I-0 o, II-45 o III-90 o The sample injected at higher angle is shifted to a higher temperature compared with other two samples injected at smaller angles. It should be noted that this polymer shows a decrease of ΔCp with the increase of the injection angle, the higher values recorded at the sample injection Ultramid A3EG5 angle of 0. In this case, the highest values of specific heat flow are for the sample injected with the largest angle, 90 0 and the values are close to 0 injected angle. The minimum value, mw/mg is specific for A3EG5 Ultramid injected sample at 45 o angle, values about 1.4 times smaller than sample injected at 0 o. For Ultramid A3EG6 samples the DSC curves are shown in Figure 4. According to the data of table 1 this material has a glass transition moving at temperature values lower with increasing the angle of injection. The ΔCp has similar values for all three samples analyzed. At higher temperature the heat flow stabilizes, the highest value (about 0.35 mw/mg) is for sample injected at 45 o and the smallest for the 90 injection angle (approximately mw/mg). The average value is specific for the injected sample at 0 angle. 2-72

5 Fig.4 Curba DSC înregistrata în timpul încălzirii probei Ultramid A3EG6 Table 1. Summary of data evaluation with Proteus software for determination of glass transition temperatures and heat capacity ΔCp Material Injection angle, [ o ] Inflection point, [ o C] ΔCp, [J/g K] Started temperature, [ o C] End temperature, [ o C] Ultramid A3EG5 Ultramid A3EG Conclusions The main conclusion consists of during the heating on DSC thermogram at temperatures between 40 and 60 C occurred a glass transition for all analyzed samples. The glass transition was not clearly influenced by the increasing of the injection angle and at glass transition higher temperatures on the DSC thermogram has been no change of the heat flow that would suggest the presence of a solid processing. From this point of view it can be stated that the analyzed samples are thermally stable up to the temperature of 200 C. 2-73

6 References [1] L. Feng, X. Bian, G. Li, Z. Chen, Yi Cui, X. Chen, Determination of ultra-low glass transition temperature via differential scanning calorimetry, Polymer Testing 32 (2013), [2] M.J. Richardson, Thermal analysis of polymers using quantitative differential scanning calorimetry, Polym. Test. 4 (1984), [3] C. Schick, Calorimetry, Polymer Science: A Comprehensive Reference, 2, (2012), [4] W. Sun, A.P.Vassilopoulos, T. Keller, Effect of thermal lag on glass transition temperature of polymers measured by DMA, International Journal of Adhesion & Adhesives, 52, (2014), [5]. Tooru Atake, Application of calorimetry and thermodynamics to critical problems in materials science, J. Chem. Thermodynamics 41 (2009), [6]. N.M. Lohan, L.-G. Bujoreanu, C. Baciu, Influence of temperature variation rate on calorimetric response during heating and on martensite structure obtained after subsequent cooling of Cu Zn Al shape memory alloy, Micro & Nano Letters, (2012), Vol. 7, Iss. 6, [7]. A. V. Svanidze, H. Huth, S. G. Lushnikov, C. Schick, Study of phase transition in tetragonal lysozyme crystals by AC-nanocalorimetry, Thermochimica Acta 544 (2012) [8]. C. Schick, Glass transition under confinement what can be learned from calorimetry, Eur. Phys. J. Spec. Top. 189 (2010), [9] D. Nedelcu, O. Pruteanu, Aspecte ale formarii canelurilor exterioare prin deformare plastic la rece utilizand metoda Taguchi, Tehnica-Info Publishing House, Chisinau, 2000,