A.J. Marzocca

Finite element analysis of cure in a rubber cylinder

Abstract The variation of temperature inside a rubber cylinder was recorded during vulcanization in a mould. The results were compared with those obtained by solving the transient heat equation by a finite element technique. Heat generation during cure was considered by means of first-order curing kinetics with the introduction of an induction time. The state of cure at any point of the object was obtained by using the equivalent time concept and was represented by a map of isocure curves.

Dynamic properties in aluminum filled PMMA

The dynamic mechanical properties of polymethyl methacrylate reinforced with different amounts of aluminum filler were investigated. The internal friction and the shear storage modulus were measured with an automated damped torsional pendulum in the temperature range between 200 and 375 K in an argon atmosphere. An increase in the glass transition temperature occurred at higher filler contents. The amount of filler in the matrix seems to modify the β relaxation of the composite. The dynamic modulus increases with the aluminum percentages for low filler content. These results were explained in terms of a model presented in the literature for the elastic modulus.

Physical Phenomena Related to Free Volumes in Rubber and Blends

In the present chapter, different aspects related to free volumes and the physical phenomena involving free volumes in rubbers and blends are discussed. Experimental results were obtained using conventional experimental techniques (e.g. dynamic mechanical tests, differential scanning calorymetry and swelling) and principally a non-conventional one (positron annihilation lifetime spectroscopy—PALS). PALS has demonstrated a high capability to give direct information on free volumes. Due to its significant role in the study of nanoscopic effects in molecular systems (among them polymers), the physical grounds of the technique are explained. It is also illustrated how PALS detects free nanohole volumes and gives information on their changes as a consequence of different reactions induced in polymers. Based on the latest experience of the authors, some examples of PALS studies on NR and SBR rubbers and NR/SBR blends are presented. The results obtained are discussed using a modern scientific approach to the study of physicals processes in these elastomers; i.e. the analysis of the experimental information is given into the frame of well recognized theoretical models.

Influence of the Crosslinking Content on the Structural Properties of Polybutadiene Rubbers with Different Isomeric Composition

In the present work first results on structural properties of three commercial isomers of polybutadiene rubber are presented. To this aim, rheometry, PALS, DSC and swelling techniques were used. Different samples were prepared containing diverse amounts of dycumil peroxide as crosslinking agent and vulcanized at 433 K.A correlation among the experimental results obtained using different techniques is also discussed.