Polymer Testing 21 (2002) 545–550 www.elsevier.com/locate/polytest Material Properties Mechanical properties evaluation of PVC/plasticizers and PVC/thermoplastic polyurethane blends from extrusion processing V.J.R.R. Pita a , E.E.M. Sampaio b , E.E.C. Monteiro a,* a Instituto de Macromole ´culas, Professora Eloisa Mano Universidade Federal do Rio de Janeiro, CP 68525, Rio de Janeiro, 21945-970, Brazil b Campus regional da UERJ, Nova Friburgo, RJ, Brazil Received 17 July 2001; accepted 16 October 2001 Abstract Mechanical and processing properties of blends of poly(vinyl chloride) (PVC) with di-isodecyl phthalate (DIDP) and thermoplastic polyurethane (TPU) were compared with di-2-ethylhexyl phthalate (DOP). The influence of processing conditions on the mechanical properties was studied by changing the content of the additives and using different twin screw speeds. The mechanical properties (tensile strength, modulus, and energy) of PVC/DIDP presented the same behaviour as PVC/DOP at all concentrations. The mechanical characteristics of PVC/DOP and PVC/DIDP show that these systems are probably affected by the speed of the twin screw. Polyurethane blends exhibit better structural properties compared to the other plasticizers. The twin screw speed exhibited no influence on the stress–strain property profile of the PVC/TPU blends. The results indicate a minor influence on the decrease of PVC properties when the plasticizer used is a TPU.  2002 Elsevier Science Ltd. All rights reserved. Keywords: PVC/plasticizers blends; Mechanical properties; Extrusion processing 1. Introduction Poly(vinyl chloride) (PVC) plays an important role in the plastic industry and is one of the most versatile thermoplastics, but it must be combined with a number of additives before processing. Low-molecular-weight plasticizer is one of the major additives used in PVC compounding. The addition of plasticizers to a PVC formulation decreases many mech- anical properties of the PVC product (hardness, tensile strength, modulus, etc.); however, low-temperature flexibility, elongation, and the ease of processing are all * Corresponding author. Tel.: +55-21-495-2861; fax: +55- 21-270-1317. E-mail address: ecermel@ima.ufrj.br (E.E.C. Monteiro). 0142-9418/02/$ - see front matter  2002 Elsevier Science Ltd. All rights reserved. PII:S0142-9418(01)00122-2 improved. The most widely used low-molecular-weight plasticizer is di-2-ethylhexyl phthalate (DOP) [1]. These types of blends present serious problems of high migration (permanence) and consequent loss of blend properties. One alternative to this kind of problem is the use of polymeric plasticizers. Polyester/PVC miscibility studies [2,3] have shown that some polymeric polyesters are to some extent miscible with PVC, and other studies have shown that some polyurethanes are also miscible with PVC. Polyester-based thermoplastic polyurethane (TPU) is commonly blended with plasticized PVC resulting in a PVC blend with improved abrasion and fatigue resist- ance [1,4,5]. However, as with most PVC/thermoplastic blends, they are difficult to process on conventional PVC processing equipment because of their high melt vis- cosity and limited heat stability [6]. The addition of TPU plasticizers to PVC to form a