Importance of reversible reaction for the synthesis of telechelic polymer by means of polycondensation using an excess of one monomer

We show that reversible polycondensation through alkoxide-catalyzed ester-ester exchange reaction is an effective strategy for the synthesis of telechelic polymers free from contamination with cyclic polymer in the polycondensation of...

Novel sustainable biobased flame retardant from functionalized vegetable oil for enhanced flame retardancy of engineering plastic

The flame retardancy of an engineering plastic, poly(butylene terephthalate) (PBT), with a biobased flame retardant (FR) made from phosphorylated linseed oil (PLO) and phosphorylated downstream corn oil (PCO) was studied. Different phosphorus moieties were incorporated into the vegetable oil backbone through a ring-opening reaction. The chemical structure of the phosphorylated oil was confirmed by Fourier-transform infrared (FTIR) and nuclear resonance magnetic (NMR) spectroscopy. It was found that the incorporation of only 7.5 wt% of PLO was sufficient to change the UL-94 fire class of PBT from non-rating to V-0. The flame-retardancy mechanism of the PBT/PLO blends was evaluated from TGA-FTIR analysis. The combined effects of the gas phase mechanism and the dripping tendency of the blends aided to retard the flame propagation effectively. As the synthesized PLO and PCO contained high free fatty acids, the acid-ester exchange reaction occurred in the blends to form oligomers during the ignition. As a result, the blend dripped immediately and the drips carried all the heat to prevent fire. This work suggests that this sustainable biobased FR could be a desirable alternative to halogen-based FRs for PBT and other engineering polymers to develop more environmentally friendly FR products for various future applications.

Synthesis, Characterization, and Antioxidant Evaluation of Novel Pyridylurea-Functionalized Chitosan Derivatives

In order to improve the bioactivity of chitosan, we synthesized a novel series of chitosan derivatives: firstly, chitosan was reacted with methylclhlorofonmate obtaining N-methoxyformylated chitosan (1), which was then converted into N-pyridylurea chitosan derivatives (2a-2c) by amine-ester exchange reaction. In addition, N-pyridylurea chitosan derivatives were conducted by reacting with iodomethane to obtain quaternized N-pyridylurea chitosan derivatives (3a-3c). The structural characteristics of as-prepared chitosan derivatives were confirmed by fourier transform infrared (FT-IR), 1H nuclear magnetic resonance (1H NMR), elemental analysis, and scanning electron microscope (SEM). Meanwhile, the antioxidant activity of the chitosan derivatives was assessed in vitro. As shown in this paper, the antioxidant activity decreased in the order: c > b > a. Moreover, after the quaternization with iodomethane, quaternized N-pyridylurea chitosan derivatives immediately exhibited enhanced antioxidant capacity compared with N-pyridylurea chitosan derivatives. For example, in 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay, the scavenging activities of 3a-3c were 91.75%, 93.63%, and 97.63% while 2a-2c were 42.32%, 42.97%, and 43.07% at 0.4 mg/mL. L929 cells were also adopted for cytotoxicity test of chitosan and synthesized derivatives by CCK-8 assay and all samples showed decreased cytotoxicity. These results suggested that the novel pyridylurea-functionalized chitosan derivatives could be an ideal biomaterial.

Biodiesel Production through Direct Transesterification of Waste Cooking Oil with Alcohol via Ultrasonic Wave

Biodiesel is prepared from waste cooking oil and methanol. The ester exchange reaction is conducted under ultrasonic conditions with alkali as the catalysts. Five factors influencing on the transesterification reaction of biodiesel production are discussed in this study, including the reaction time, reaction temperature, catalyst amount, methanol to oil molar ratio, ultrasonic power. A series of laboratory experiments were carried out to test the conversion of biodiesel under various conditions. The process of biodiesel production was optimized by application of orthogonal test obtain the optimum conditions for biodiesel synthesis. The results showed that the optimum reaction conditions were:molar ratio of oil to methanol 8:1,catalysts 1.2g KOH/100g oil,reaction temperature 70°C, reaction time 50 min,Ultrasonic power 400W. The conversion may up to 96.48%.

Experiment Study on Biodiesel Produced from Soybean Oil by Solid Base Catalysts

In this paper, biodiesel is successfully produced by the ester exchange reaction with solid base catalyst of K2O/Ti-HMS based on soybean oil as raw materials. The result of which shows that K2O/Ti-HMS has good ester exchange activity as solid base catalyst and the catalyst easily is separated from products. By single factor experiment, the influence of K2O load, molar ratio of methanol and oil and catalyst dosage on the biodiesel conversion rate is researched and the optimal relationship between the above parameters is obtained.