Improvement of Processing and Mechanical Properties of Polyetherimide by Antiplasticization with Resorcinol Bis(diphenyl phosphate) Evandro M. Alexandrino, Thiago F. da Conceic ¸ ~ ao, Maria I. Felisberti Institute of Chemistry, University of Campinas (UNICAMP), Campinas 13083-970, Brazil Correspondence to: M. I. Felisberti (E-mail: misabel@iqm.unicamp.br) ABSTRACT: This article describes the antiplasticization of a commercial polyetherimide ULTEMV R series 1000 [poly(bisphenol A-co- 4-nitrophthalic anhydride-co-1,3-phenylenediamine) by resorcinol bis(diphenyl phosphate)] (RDP) and its implications on the ther- momechanical processing, namely extrusion and injection molding, as well as on the thermal and mechanical properties of the formulations. This antiplasticization effect allows the processing of polyetherimide formulations at lower temperatures in comparison with neat polymer due to the progressive decrease of the glass transition temperature with increased RDP concentration, as observed by differential scanning calorimetry and dynamic mechanical analysis. The decrease of T g occurs concomitantly with the overlap of the glass transition and b relaxation and with the shift of the c relaxation to higher temperatures. These changes in the relaxation spectrum of polyetherimide formulations are possibly responsible for the increase of the tensile strength and Young’s modulus and changes in the fracture mechanism, as observed by stress–strain tests and by scanning electron microscopy, respectively. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40619. KEYWORDS: glass transition; mechanical properties; plasticizer; polyimides; synthesis and processing Received 29 October 2013; accepted 18 February 2014 DOI: 10.1002/app.40619 INTRODUCTION Plasticizers are common additives of great interest for the engineer- ing thermoplastics market, representing a third of the additives market. 1 The plasticization effect of low molar mass diluents mixed into polymeric materials is quite well known and topic of reviews and books. 1–5 The usual effect of plasticizers on a polymer matrix is characterized mainly by a decrease in the glass transition tempera- ture (T g ), Young’s modulus, and tensile strength, with an increase in the elongation at break and toughness. 1 However, for some diluent-polymer pairs, an increase in stiffness is observed despite the usual decrease in glass transition temperature. This unexpected behavior is known as the antiplasticization effect 6–10 for which the magnitude depends on the molecular characteristics of the addi- tives (size, shape, and stiffness), of the polymers (polarity and stiff- ness) and of the polymer-additives interactions. 11,12 The antiplasticization occurs in many different diluent-polymer systems as, for example, tricresyl phosphate in polysulfone 13,14 ; dibutylphthalate 15,16 , nonlinear optical dyes such as lead tetracu- mylphenoxy phthalocyanine 17 and p-therphenyl 18 in polycarbon- ate; phenacetin and acetanilide in poly(ethylene terephthalate) 19 ; 4,4 0 -(hexafluoroisopropylidene) diphenol, hydroquinone, and 4-hydroxybenzophenone in poly(amino-ether) resin 20 ; water in starch 21–23 ; water in poly(ether ether ketone) 24 ; among others. The antiplasticization of poly(vinyl chloride) has been extensively studied for several diluents. For example, Kinjo and Nakagawa 25 studied the effect of five different diluents (tricresyl phosphate, butyl benzyl phthalate, dioctyl phthalate, dibutyl sebacate, and dioctyl sebacate) on the b secondary relaxation, glass transition, and Young’s modulus, observing a simultaneous decrease in T g and increase in modulus. The probable mechanism of antiplasti- cization is not well understood, however, the suppression of sec- ondary relaxations with the decrease in T g , together with changes in the free-volume, are considered as the main causes of it. 10,19–30 The antiplasticization magnitude is determined by the potential of the additive in inhibiting secondary relaxations. 10 The antiplasticization induced by low molar mass molecules has been extensively used in order to improve the barrier properties of polymers. One argument for this is that antiplasticization is associated with losing of free volume that results in changes in the relaxation spectrum of the polymer and, therefore, in barrier and mechanical properties. 20 However, one of the most interest- ing aspects of this effect is the enhancement of the Young’s modulus without losing the transparency of amorphous poly- mers, as the antiplasticizer is soluble in the polymer. Moreover, V C 2014 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2014, DOI: 10.1002/APP.40619 40619 (1 of 8)