Carbohydrate Polymers 83 (2011) 354–361 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Thermal and microstructural characterization of biodegradable films prepared by extrusion–calendering process T. Galicia-García a,∗ , F. Martínez-Bustos a , O. Jiménez-Arevalo b , A.B. Martínez c , R. Ibarra-Gómez d , M. Gaytán-Martínez a , M. Mendoza-Duarte d a CINVESTAV-Unidad Querétaro, Libramiento Norponiente 2000, Fracc. Real Juriquilla, Qro, CP.76001, Mexico b CIATEQ, Av Retablo 150, Col. FOVISSSTE, Santiago de Querétaro, Qro CP. 76150, Mexico c Centro Catalán del Plástico, Universidad Politécnica de Catalu˜ na, Edifici Vapor Universitari, Carrier Colom, 114, 08222 Terrasa, Spain d CIMAV, Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chihuahua, Mexico article info Article history: Received 26 February 2010 Received in revised form 1 June 2010 Accepted 26 July 2010 Available online 11 August 2010 Keywords: Extrusion–calandering Thermal and microstructural properties Starch films abstract Native starch (corn, potato and waxy corn) and phosphorylated corn starch blended with bagasse fiber and glycerol were used for the preparation of biodegradable films. The processing extrusion vari- ables were: feed moisture FM (18.25–20.5%), fiber content FC (0–10%) and type of starch TS (native or phosphorylated). The analysis of infrared spectroscopy showed OH and C–O bands at 2750–3250 and 550–1000 cm -1 , related to plasticizer–starch interactions. Films processed without fiber revealed peaks of low intensity associated to the plastizicing of starch. Differential scanning calorimeter displayed some changes in calorific capacity that could be attributed to molecular excitations and the mobility of polymeric chains (T g ) in a range of temperature between 40 and 80 ◦ C. The dynamic mechanical analy- ses presented a decrease in the loss modulus at a temperature lower than 100 ◦ C associated to a more structural mobility of bonds indicating a film with more flexibility. The thermal and microstructural char- acterization of films showed appropriate functional properties in the development of packing materials or flexible containers type bag. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction The worldwide consumption of biodegradable polymers (BPs) has increased in the last years. These natural biodegradable mate- rials include packaging materials (trash bags, wrappings, loose-fill foam, food containers, film wrapping, laminated paper), dispos- able nonwovens (engineered fabrics) and hygiene products (diaper back sheets, cotton swabs), consumer goods (fast-food tableware, containers, egg cartons, razor handles, toys), and agricultural tools (mulch films, planters) (Bernard, Gontard, & Guilbert, 1998). Polymers are a series of viscoelastic materials. The structural and mechanical characterizations are important tools and a good example of introducing the measurement of the physical properties of industrial polymers into the research field of biodegradable poly- mers. Edible films or biodegradable films have a wide application in the industry market for their specified thermal and mechan- ical properties. Heating amorphous thermoplastic agro-polymers above the glass transition temperature, produces soft and rubbery ∗ Corresponding author. Tel.: +52 442 441 4900; fax: +52 442 441 4933. E-mail addresses: thomhhas@yahoo.com.mx, tgalicia@qro.cinvestav.mx (T. Galicia-García). materials, and may permit their incorporation into specific prod- ucts such as packaging materials. Cooling to room temperature can reconvert rubbery products to glassy materials, giving more or less rigid forms with the desired structure (Cuq, Gontard, & Guilbert, 1997). Starch-based biopolymers can be produced by blending or mix- ing as different naturals polymers as fiber. By varying the blend component and processing conditions and its miscibility with starch, the morphology and hence, the functional and structural properties can be regulated efficiently and, also, allows to design the most important mechanical and functional properties of these materials improving the efficiency of biodegradable packages. Besides, as for synthetic polymers, composition, microstructure and functional properties of films based on biopolymers deter- mine their possible applications. In 2002, two million tons of starch were produced in the world. Because of its abundance and its renewable and environmental friendly characteristics, physically and/or chemically modified starch has been the feedstock of choice in numerous research efforts on development of biodegradable starch-based loose-fill foams and biodegradable materials. Generally, plasticizers are used for two purposes which are to aid processing and to modify the properties of the final product. In the case of starch-based films, a plasticizer addition overcomes 0144-8617/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbpol.2010.07.050