2.1. Materials
The biodegradable (PLA) used as the thermoplastic matrix polymer was supplied by NatureWorks LLC., USA. PLA has a density of 1.24 g/cm3 and melt flow index at 210 ◦C of 15–30 g/10 min. The crystalline melt temperature (Tm) is 160–170 ◦C, and the glass transition temperature is 55–60 ◦C as reported by the manufacturer. Polyhydroxybutyrate (PHB), which is a biopolymer, was supplied by GoodFellow Corporation. The density was 1.25 g/cm3, and the melting temperature was 170 ◦C based on information from the supplier. CNF, trade name Celish-Rokameijin: solid paste state
(dried CNF/water = 35 wt.%/65 wt.%)) was purchased from Daicel Chemical Industries, Ltd., Japan. The fibril diameter and length of the CNF were 10–500 nm and 1–10 m respectively (Fig. 1).