Polymer-polymer miscibility in PEO/cationic starch and PEO/hydrophobic starch blends

A. G. B. Pereira, A. T. Paulino, A. F. Rubira, E. C. Muniz
2010 eXPRESS Polymer Letters  
Introduction Blending of polymers is an interesting route for producing new materials, basically due to economics aspects [1] . The miscibility between the polymers is a very important factor in the development of polymer blends [1, 2] . Considering the low entropy associated to the polymers mixture, ΔS m , the miscibility between the components of a polymer blend is mainly driven by the enthalpy of mixing, ΔH m . Thus, effects that decrease ΔH m will favor to the miscibility due to the
more » ... due to the decrease of the Gibbs energy of mixture, ΔG m . In the light of this, attractive interactions among side groups or polymer segments are, in most of the cases, responsible for polymer-polymer miscibility. Different techniques have been used for evaluating the miscibility, for example, thermal analysis through determination of the glass transition temperature (T g ) [3-5], microscopy (Optical Microscopy -OM, Scanning Electronic Microscopy -SEM, Atomic Force Microscopy -AFM, Transmission Electronic Microscopy -TEM, and so on) [5] [6] [7] [8] and spectroscopy (Fourier Transform Infrared -FTIR-Image, Raman-Image, Nuclear Magnetic Resonance -NMR, and so on) [9] [10] [11] [12] . The presence of an amorphous (or slightly crystalline) component affects the crystallization process of the other polymer component significantly. When a given system is miscible, the equilibrium melting temperature (T m 0 ) is expected to be lower 488 Abstract. The main purposes were evaluating the influence of different starches on the miscibility with Poly(ethylene oxide) (PEO) and their effects on the spherulite growth rate. Polymer-polymer miscibility in PEO/cationic starch and PEO/hydrophobic starch blends consisting of different w/w ratios (100/0, 95/05, 90/10, 80/20, 70/30, 65/35 and 60/40) was investigated. This analysis was based on the depression in the equilibrium melting temperature (T m 0 ). By treating the data of thermal analysis (Differential Scanning Calorimetry -DSC) with Nishi-Wang equation, a positive value (0.68) was found for the interaction parameter of PEO/cationic starch. For PEO/hydrophobic starch blends, a negative value (-0.63) was obtained for the interaction parameter. The results suggested that PEO/cationic starch system should be immiscible. However, the system PEO/hydrophobic starch was considered to be miscible in the whole range of studied compositions. Through optical microscopy analysis, it was concluded that the spherulite growth rate is significantly affected by changing the amount and the type of starch as well. Keywords: polymer blends and alloys, PEO/starch blends, PEO/starch miscibility, PEO/starch spherulite growth rate, biopolymer eXPRESS
doi:10.3144/expresspolymlett.2010.62 fatcat:jtkvh34dwza55lk7gsegimnj34