Abstract:

Objective Polyester industry is an important industry relating to the national economy and the people's livelihood. Most polyesters are prepared from petroleum and other fossil resources as raw materials. The combustion process of polyester will produce a large amount of carbon dioxide and sulfur dioxide, which not only pollute the environment, but also lead to global warming, climate change and other serious problems. In order to further implement the sustainable development and the promote China's ″double carbon″ strategic goal, it is urgent to minimise the dependence on fossil energy. In 2004, the US Department of Energy released 12 platform compounds derived from biomass that can be converted into high value-added biobased materials. Among them, the chemical structure of 2,5-furanedicarboxylic acid (FDCA) is similar to petroleum based terephthalic acid (PTA), which can be used as an ideal biobased substitute for PTA. With the maturity of the synthesis and purification technology of FDCA, furan based polyester has attracted attention in various fields, becoming a key research direction of biobased high molecular materials. This research focus is on the study of furan based homopolymers and copolymers.

Method In this research, the use conditions of zinc acetate tetrabutyl titanate composite catalyst were optimized using 1,3-PDO and DMFD as raw materials. The full biological PTF with high molecular weight was synthesized by transesterification melt polycondensation. The chemical structure and thermal properties of the PTF were characterized by infrared spectroscopy, nuclear magnetic resonance hydrogen spectroscopy, differential scanning calorimetry and thermogravimetry, the biobased PTF fibers were prepared by two-step spinning process(UDY-DT), and the influences of different drafting ratios on the mechanical properties of the fibers were studied.

Results In the process of adjusting the reaction process, it was found that only zinc acetate was added in the esterification stage, and tetrabutyl titanate was added in the polycondensation stage. The alcohol ester ratio was increased to 2.6, which would synchronously reduce the transesterification reaction time (Tab. 1). The analysis of the chemical structure of the product showed that the target product PTF (Figs.3 and 4) was successfully synthesized, and the number average molecular weight of the prepared product reached 3.25 × 10⁴ g/mol, the PDI was controlled below 3 (Tab. 4), and the chip color was light yellow. It is believed that the optimal use conditions of the combined catalyst were found. The glass transition temperature of the synthesized product was 60-62 ℃, the melting point was about 171 ℃, and the initial thermal decomposition temperature was higher than 370 ℃ (Tab.5). With the primary fiber drawn to 2.5 times, the elongation at break of PTF fiber was about 34.2%, and the breaking strength was 0.48 cN/dtex (Tab. 6).

Conclusion The whole biological PTF fiber was successfully prepared by UDY-DT two-step method. After 2.5 times of drafting, the elongation at break of the fiber was 34%, and the breaking strength was 0.48 cN/dtex. Owing to wide molecular weight distribution of PTF, relatively low breaking strength of prepared PEF fiber, and yellow color of polymer and fiber, further optimization and improvement of synthesis and spinning process are required in future research work.

Key words: fully biobased material, polytrimethylene furandicarboxylate, synthesis process, melt spinning, transesterification melt polycondensation, thermal performance