*2.1. Materials*

Poly (lactic acid) (PLA) resin produced by SMBEST Pvt. Ltd. (Busan, Korea) was used as the matrix material. Its density was 1.2–1.31 g/cm3, and its melt flow index (MFI) was below 5 g/10 min at 5 kg/190 ◦C. In terms of the reinforcement materials, bleached pulp fibers were initially supplied by An Hoa Paper Joint Stock Company (Tuyen Quang, Viet Nam) then cut to the size of 3–4 mm. The properties of bleached pulp fibers were listed in Table 1.


**Table 1.** The properties of bleached pulp fibers.

Tung oil was supplied by Vietnam Tung oil company limited (Ha Noi, Viet Nam). The properties of Tung oil were listed in Table 2. Amberlite® IRC120 H, hydrogen form 15 wt% to oil (Sigma), H2O2 (Sigma) and acetic acid (Sigma) were used to modified Tung oil.


**Table 2.** The properties of Tung oil.

To prepare epoxidized Tung oil, Tung oil was stirred in a flask and heated to 55 ◦C in the presence of Amberlite® IRC120 Has the catalyst with a uniform agitation under the constant stirring speed of 1600 rpm. A mixture of H2O2 and acetic acid was dropwise added into the mixture of Tung oil and Amberlite® IRC120 at a constant rate for 2 h. The reaction time was 5 h and the ratio of Tung oil/acid acetic/H2O2 was 1.0/0.5/0.5. At the end of the reaction, the mixture was cooled and centrifuged at least 5 min under the rotation speed of 2000 rpm. The oil phase, separated from the aqueous phase and the catalyst, was washed with distilled water until acid free, and evaporated for at least 1 h under the vacuum of about 40 mbar at 60 ◦C [19]. Epoxy value was determined by titration method according to TY-6-10-722-72. Epoxy value of epoxidized Tung oil was 6.8%.
