Vol.:(0123456789) 1 3 Journal of Polymers and the Environment https://doi.org/10.1007/s10924-020-01652-8 ORIGINAL PAPER Tuning Degradation and Mechanical Properties of Poly(L‑lactic acid) with Biomass‑Derived Poly(L‑malic acid) Qianru Wanyan 1  · Yaxin Qiu 1,2  · Wenyuan Xie 1,3  · Defeng Wu 1,2,3 © Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract Poly(L-malic acid) (PLMA) oligomer was used as the minor phase to prepare the blends with poly(L-lactic acid) (PLLA), with the objective to develop fully biomass-derived and biodegradable aliphatic polyester blends with balanced overall performance. The phase behavior and viscoelastic responses reveals that the two phases are thermodynamically immiscible, showing high level of interfacial tension in their blends. Poor phase adhesion and lower mass weight of PLMA results in an evident decrease of mechanical properties of the blends as compared to PLLA. The dilute efect caused by the addition of PLMA, however, promotes the cold crystallization of PLLA. Therefore, the strength and modulus losses of the blends can be remedied well by the annealing in solid state. Besides, the degradation rates can also be regulated by the presence of hydrophilic PLMA phase. In this case, a fully green PLLA/PLMA blend with balanced properties is fabricated. This work also provides useful information developing new applications of PLMA. Keywords Poly(L-lactic acid) · Poly(L-malic acid) · Mechanical properties · Degradation · Phase behavior Introduction Poly(L-lactic acid) (PLLA) is a biomass-derived aliphatic polyester material with good mechanical strength. Its mono- mer, lactic acid or lactide, is derived from the fermentation products of industrial maize. Therefore, it becomes a prom- ising candidate to replace the petrochemical-based polymers in many applications such as packaging and fber weaving [1–3]. However, the most attractive characteristic of PLLA is its biodegradability. It can be hydrolyzed, or recycled back to the monomer at diferent conditions [2–5]. Owing to these eco-friendly and sustainable characteristics, PLLA has attracted increasing interest in recent years. To improve its overall performance, and in this way to open up its new applications, blending it with other biodegradable aliphatic polyesters with fully diferent bulk properties is an efcient and simple way. For instance, the ductile polycaprolactone or poly(butylene succinate) possesses better toughness and solid plasticity than the glassy PLLA, with far lower degra- dation rates. Accordingly, using them as the minor phase, the overall properties of glassy PLLA is easily regulated through physical blending [6–11]. Similar with PLLA, poly(L-malic acid) (PLMA) is bio- mass-derived and biodegradable [12]. It is synthetic via ring- opening polymerization [13–15], or direct polycondensation [16], and its monomer L-malic acid is easily derived from fresh fruits. However, these two ways are not convenient. The ring-opening polymerization consists of many repeated purifcation steps [17], while the direct polycondensation has poor yield, and the resultant PLMA is of lower number aver- age molecular weight (1500–2500) [17]. The preparation of PLMA is hence still of lab-scale. The reported works mainly concentrate on the chain extensions of PLMA with L-lactide [18–20], ε-caprolactone [21–23], or β-butyrolactone [24, 25] by grafting reactions or copolymerization, or on the chemi- cal crosslinking [26], and in these ways to endow PLMA with acceptable material strengths and rigidity. Actually it is not always necessary to improve the chain structure of PLMA by those time-consuming and high-cost approaches. The backbone of PLMA is hydrophilic [12], and the lower mass weight endows PLMA with good fowability. * Defeng Wu dfwu@yzu.edu.cn 1 School of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou 225002, Jiangsu, China 2 Provincial Key Laboratories of Environmental Engineering & Materials, Yangzhou 225002, Jiangsu, China 3 College of Innovative Material & Energy, Yangzhou University, Yangzhou 225002, Jiangsu, China