Abstract: Introduction: Biodegradable polymers draw attention due to environmental issues of petroleum-based plastics. They have wide applications in an environmentally friendly packaging, biomedical materials, in various industrial applications such as computer and mobile phone industry [1]. Poly (lactic acid) (PLA) is the most popular biodegradable polymer which is composed of repeating units’ lactic acid. It is produced by fermentation from renewable resources, such as corn or sugar beet. [1, 2, 3]. PLA has comparable properties with the synthetic polymers such as high modulus and tensile strength value. In addition to this, it also has some disadvantages, for example, the films of PLA are very brittle and poor thermal stability [4]. Therefore, it is limited use some industrial applications. In the recent years, researchers focused on to modification of PLA to the improvement of thermal and mechanical properties. In the literature, various studies have been carried out by using different methods to improve the properties of the PLA. Annealing, adding nucleating agents, forming composites with fibers or nanoparticles, chain extending and introducing crosslinking structures were used to enhancing the heat stability or mechanical properties of PLA [4, 5]. Besides, the formation of polymer blends is one of the knowing methods for modification of polymer characteristic and including functional properties to improve the properties of PLA.
Goal: In this study, it was aimed to investigate the effect of microwave radiation on the thermal and mechanical properties of Poly (Lactic Acid)/Cationic Monomer blends. Vinyl benzyl trimethyl-ammonium chloride (VBTMAC) was selected as the cationic monomer. Method: Experimentally, the cationic monomer was added 5 wt.% to PLA. 2,2’-Azobis (2-methylpropion amidine) dihydrochloride (AIBN) was used as the initiator with the ratio of 5% of the total amount of monomer. PLA based films were prepared by solution casting method. PLA was dissolved in chloroform. Neat PLA film was used as control samples. The films were prepared two different ways. Firstly, PLA/Cationic Monomer blends were prepared without the initiator. Then, same compositions were cast by using initiator. Also, microwave irradiation was applied to the prepared film with initiator by home type microwave. The power of the microwave was set at 230 W and the films were left in the microwave for 15 minutes. Then, the properties of pure PLA film, PLA/Cationic Monomer blends with/without initiator and microwave irradiated films were compared. Discussion: Chemical structure of the films was characterized by Fourier transform infrared spectrometry (FTIR). The thermal and mechanical properties of samples were also determined by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile testing. Results: Chemical structures of the films were determined by using the FTIR spectra. The FTIR spectra of neat polymer and their blends were obtained. A new peak in the spectra was not observed. The FTIR spectra of all the blend before and after the microwave treatment did not show any significant difference. According to DSC results, the melting temperature of PLA blends was not changed significantly. The percentage crystallinity values decreased by adding VBTMAC. The maximum tensile strength and strain values were obtained for microwave irradiated films compared to the neat PLA film.
Anahtar Kelimeler: Polylactic acid (PLA), cationic monomer, initiator, microwave
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