**Van Khoi Nguyen \*, Thanh Tung Nguyen \*, Thu Ha Pham Thi and Thu Trang Pham**

Institute of Chemistry, VAST, 18 Hoang Quoc Viet, Cau Giay, Ha Noi 122300, Vietnam; haptt6@gmail.com (T.H.P.T.); thutrang90vhh@gmail.com (T.T.P.)

**\*** Correspondence: khoinguyen56@gmail.com (V.K.N.); nttung@ich.vast.vn (T.T.N.); Tel.: +84-904141011 (V.K.N.); +84-901333885 (T.T.N.)

Received: 13 April 2020; Accepted: 15 May 2020; Published: 19 May 2020

**Abstract:** Recently, various environmental-friendly materials have been investigated and developed, especially composites of polylactic acid (PLA) and plant fibers. This paper investigates the effects of pulp fiber (PF) and epoxidized Tung oil (ETO) content on the properties of biocomposites, based on polylactic acid. The bleached pulp fiber reinforced PLA (PLA/PF) composites with 10–50 wt% fiber contents and 0–15% epoxidized Tung oil contents (with a certain number of fiber) were prepared in an internal mixer (Plastograph® EC) at 150 ◦C. The mechanical properties of PLA/PF composites were improved significantly. The pulp fiber reinforced PLA composites, with the fiber content of 30 wt%, were found to have the highest mechanical properties. The tensile and flexural properties of PLA/Tung oil-soaked-pulp fiber composites were higher than those of PLA/Tung oil unsoaked pulp fiber composites. In addition, the degradation temperature of PLA-based composites decreased after adding more pulp fiber. The pulp fibers were well-dispersed in the PLA matrix with the content up to 30 wt%. The interaction between pulp fiber and PLA matrix improved by the addition of epoxidized Tung oil. Epoxidized Tung oil also improved tensile and flexural strength of composite materials when it was added with a number of below 10% of fiber.

**Keywords:** poly (lactic acid); pulp fiber; natural fiber reinforced composites; epoxidized Tung oil
