Poly(propylene carbonate)/aluminum flake composite films with enhanced gas barrier properties Lipeng Zhai, 1 Gaofeng Li, 1 Yan Xu, 2 Min Xiao, 1 Shuanjin Wang, 1 Yuezhong Meng 1 1 State Key Laboratory of Optoelectronic Materials and Technologies/The Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province, Sun Yat-sen University, Guangzhou 510275, People’s Republic of China 2 Instrumental Analysis & Research Center, Sun Yat-sen University, Guangzhou 510275, People’s Republic of China Correspondence to: Y. Z. Meng (E - mail: mengyzh@mail.sysu.edu.cn) and Y. Xu (E - mail: xuyan@mail.sysu.edu.cn) ABSTRACT: A series of poly(propylene carbonate) (PPC)/aluminum flake (ALF) composite films with different ALF contents were pre- pared via a melt-blending method. Their cross-section morphologies, thermal properties, tensile strength (TS), and gas barrier prop- erties were investigated as a function of ALF contents. SEM images reveal the good dispersion and orientation of ALF along with melt flow direction within PPC matrix. The oxygen permeability coefficient (OP) and water vapor permeability coefficient (WVP) of the composite films decrease continuously with ALF contents increasing up to 5 wt %, which are 32.4% and 75.2% that of pure PPC, respectively. Furthermore, the TS and thermal properties of PPC/ALF composite film are also improved by the incorporation of ALF particles. The PPC/ALF composite films have potential applications in packaging area due to its environmental-friendly proper- ties, superior water vapor, and oxygen barrier characteristics. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41663. KEYWORDS: biodegradable; blends; composites; manufacturing; packaging Received 19 May 2014; accepted 20 October 2014 DOI: 10.1002/app.41663 INTRODUCTION The white pollution caused by petroleum-based materials has become an international environmental issue and the limited petroleum has driven amount of efforts to explore biodegrad- able or bio-based materials. 1,2 Additionally, global warming, also known as the greenhouse effect, is caused by the mass emission of CO 2 produced by industries. 3–5 Therefore, the fixa- tion of carbon dioxide has attracted a great deal of interest as a means to reduce greenhouse gas pollution and has been consid- ered an alternative to overcome shortages in conventional petro- leum fuel supplies. In these regard, much attention has been paid to the synthesis of degradable aliphatic polycarbonates from carbon dioxide since the pioneering work by Inoue. 6–13 Poly(propylene carbonate) (PPC) is one of these aliphatic poly- carbonates that has been extensively studied and its production is known to have been industrialized. 14–16 The resulting PPC exhibits an alternating molecular structure as illustrated in Fig- ure 1, and it also showed superior mechanical properties and considerable degradability in both soil and buffer. Importantly, PPC synthesis recycles carbon dioxide from the environment and has meaningful chemical and physical properties such as compatibility, impact resistance, high translucence, and innocuousness. Such properties are advantageous in adhesives, plasticizers, solid electrolytes, barrier materials, and new materi- als for packaging applications. 17 Recently, to expand the application of PPC, great efforts have been devoted to improve the deficient thermal, mechanical, and barrier properties of PPC, including the chemically modifying the end group 18 and the physical method such as blending it with other polymers 19,20 or introducing inorganic fillers. 21,22 Among these methods, addition of various types of fillers is commercially advantageous as the physical properties are readily manipulated by the type and concentration of fillers. 23 However, for conventional filler/PPC composites, the high loading level of fillers causes the deterioration of some properties, such as the high density and the loss of toughness. Thus, it is still a chal- lenging work to obtain PPC composites with superior thermal, mechanical, barrier, and processing properties with quite low filler content. High aspect ratio flakes or platelets have been used to enhance gas barrier properties of polymers. 24 Platelet-type fillers such as aluminum flake (ALF), mica, and talc are most useful in thin barrier films. 25 Besides, for packaging materials, the best barriers can be achieved with laminates incorporating metallized films. Aluminum layers about 50–80 nm thick allow very low gas transmission rates (O 2 TR, 0.02 cm 3 m 22 day 2l ; water vapor V C 2014 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2015, DOI: 10.1002/APP.41663 41663 (1 of 6)