Rudinei Fiorio

Crosslinking Kinetics of Blends of Ethylene Vinyl Acetate and Ground Tire Rubber

The copolymer ethylene vinyl acetate (EVA) and blends of EVA and ground tire rubber (GTR) with different compositions are prepared in the presence and absence of dicumyl peroxide (DCP) as a crosslinking agent. The crosslinking kinetics is investigated through oscillatory disc rheometry (ODR) and differential scanning calorimetry (DSC). The crosslinking kinetics is found to be dependent on the amount of GTR in the EVA/GTR blends; the partially crosslinked GTR phase acts as a physical barrier, slowing down the EVA crosslinking rate. Furthermore, activation energies (Ea) and reaction order (n) values suggest that the crosslinking reactions are not restricted to the EVA bulk, but can also occur to some extent at the EVA/GTR interface.

Thermoplastic polyurethane synthesis using POSS as a chain modifier

In this study, thermoplastic polyurethanes (TPUs) were synthesized using the one-shot process in solution. To obtain the samples n-phenylaminopropyl polyhedric oligomeric silsesquioxane (POSS) was added as a chain modifier during the synthesis in four different amounts. The samples were characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and capillary rheometry. FTIR confirm the TPU attainment due the absence of the band at ~2253 cm-1 suggesting a complete conversion of the isocyanate terminations. The TGA showed that incorporation of POSS decreased the rate of mass loss of TPU under isothermal conditions. The flexible phase showed an enhanced stability to temperature, probably due to increased phase separation between the rigid and flexible domains. The DSC showed that incorporation of 0.4 wt. (%) of POSS increased the glass transition temperature of the flexible phase. Moreover, addition of POSS modified the melting behaviour, providing samples with a higher melting enthalpy compared to neat TPU as a consequence of the formation of larger crystals. The capillary rheometry analysis revels that the POSS addition showed a clear tendency toward higher intrinsic viscosities as the amount of POSS was increased.

Thermal and Mechanical Characterization of a Terpolymer Mixture of Devulcanized Recycled Ethylene-Propylene-Diene and Low-density Polyethylene

In this study, mixtures of low-density polyethylene (LDPE) and the recycled elastomeric terpolymer ethylene-propylene-diene (EPDM-r) were obtained. The EPDM-r was incorporated as obtained by the manufacturer (vulcanized) and also after being submitted to a devulcanization process using microwaves. The mixtures were obtained with the use of bis(α, α-dimethylbenzyl) peroxide. The elastomeric residue was characterized by gel content and scanning electron microscopy, before and after the devulcanization process. The mixtures obtained were characterized by thermogravimetric analysis, differential scanning calorimetry, and mechanical tests for resistance to traction and impact. The results of the analysis of the residues showed that the devulcanization process reduced significantly the gel content of the elastomer. The mixtures obtained demonstrated that the incorporation of vulcanized EPDM-r reduced the crystallization and fusion enthalpies, while conserving the crystallization and fusion characteristics of the thermoplastic. The mixtures showed a reduction in the deformation and traction strength; however, the incorporation of devulcanized EPDM-r led to a significant increase in the elasticity modulus values and the resistance to impact in relation to the pure LDPE.

Polymerization kinetics of polyurethanes containing trisilanol isooctyl polyhedral oligomeric silsesquioxane

Two polyurethane model compounds obtained from 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO) or MDI and trisilanol isooctyl polyhedral oligomeric silsesquioxane (POSS) were synthesized and characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. Moreover, polymerization kinetics of the samples obtained from an isocyanate-terminated prepolymer and BDO containing 0, 0.23, 0.57, 1.14 and 2.28 wt% of POSS were studied from oscillatory rheometry and differential scanning calorimetry. A higher thermal stability was observed for MDI + POSS when compared with MDI + BDO compound. The addition of 1.14 and 2.28 wt% of POSS increased the activation energy of polymerization. The polymerization mechanisms observed were nucleation and growth (A2) at the beginning of synthesis and diffusion controlled (D n ) at the last stage of conversion.

Influence of Processing Conditions on Productivity, Thermal and Rheological Properties of Reprocessed Low Density Polyethylene

Abstract The market for recycled thermoplastic polymers is undergoing a sharp increase, although recyclate polymers are regarded as materials with inferior properties when compared to the virgin material. This study investigates the behavior of non-contaminated scraps of low density polyethylene (LDPE) from the plastic packaging industry after single processing stage, in terms of the productivity and the thermal and rheological properties. The LDPE used was reprocessed on a single-screw extruder (Miotto) of 90 mm screw diameter and L/D = 25. Three screw speeds (80, 90 and 100 min−1) were investigated at three processing temperatures (200, 250 and 300°C). The reprocessed materials were characterized by thermogravimetric analysis TGA, parallel plates rheometry and productivity. The results obtained by TGA showed a typical range of polyolefin degradation (350 to 450°C). The viscoelastic properties did not show significant changes in relation to the rheological behavior. Increasing the temperature and screw speed promoted a productivity gain of approximately 30%. This suggests that under the conditions studied it is possible to reprocess this material with good productivity ensuring its thermal, mechanical and rheological properties.