Organic additives as antimicrobial agents in thermoplastics compounds
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lus, elongation at break and microbiological results using MYSTAT, student version 12 (Systat Software, Inc., CA, USA). The level of significance was set at 0.05. RESULTS Additives characterization The Ag_bentonite additive displayed a typical platelet form found in montorillonite clay as shown in the SEM image depicted in Figure 1 [7]. The nanoscale of Ag_bentonite was verified, showing unless one side with less than 100 nm. In the case of Cl_PE was not possible to obtain images relevant to this study, due the completely amorphous appearance of the sample.
Figure 1. Micrograph of Ag_bentonite, with a typical platelet form found on clay [9]. Thermogravimetric (TG) and Derivative Thermogravimetric (DTG) analysis of the samples Ag_bentonite and Cl_PE are shown in Figure 2A and Figure 2B, respectively. (A)
(B)
Figure 2. TG (A) and DTG (B) analysis of sample Ag_bentonite (continuous line) and Cl_PE (dashed line). The sample Ag_bentonite starts to decompose after 210 °C (Figure 2A). Below 150 °C the sample had weight loss of approximately 1.3%, probably due to evaporation of water. After the water evaporation, the DTG curves show three more events of decomposition, at 280, 324 and 441°C, illustrating a typical bentonite weight loss curves. This feature is due the degradation of
organic modifier, utilized to give hydrophilic character and increase basal spacing between the plates of clay [9]. At 800 °C remains bentonite ash, approximately 77% of inorganic material. The decomposition of Cl_PE starts below 150 °C, indicating that the additive is sensible to heat (Figure 2A). Noteworthy, the Cl_PE decomposition occurred below the processing temperature of SEBS- PP based polymeric matrices, which can be an impediment to its use. DTG curves from Cl_PE (Figure 2B) shows two decomposition events, which occur at 243 and 473 °C. Degradation of sample Cl_PE starts around 150 °C, and there is a weight loss of 32% until 300 °C corresponding to additive, and completely decomposition at 500 °C of PE. (5chloro-2-(2’,4’-dichlorophenoxy)-phenol), known as triclosan, is the most common antimicrobial chloride. A research realized by Celebioglu et al. (2014) [10] show a decomposition curve of triclosan in a single thermal event, from 140 °C to 250 °C, similar to the first stage reported here for Cl_PE sample. Polyethylene thermal properties varies on it reticulation degree, literature records provide thermograms with thermal degradation in the range of 300 °C to 450 °C for high density polyethylene [11-12], similar to the second degradation stage. Polymeric matrices characterization Significant differences were found between the polymeric matrices in their tension strength, modulus and elongation at break values (p ≤ 0.05). The results of tensile properties are summarized in Table 1. Table 1. Tensile properties of the polymeric matrices with Cl_PE and Ag_bentonite additives, compared with standard. Sample Tensile Strength Modulus 100% Elongation at identification (MPa) (MPa) Break (%) Standard Cl_PE Ag_bentonite
11.6 8.6 11.2
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