Artigo de peri??dico
Gamma-radiation effect on mechanical properties of Pp/Epdm polymeric blends
Autor
CARDOSO, ELIZABETH C.L.
SCAGLIUSI, SANDRA R.
LUGAO, ADEMAR B.
Resumen
Thermoplastic elastomers (TPEs) are provided with many properties of elastomeric or
rubbery materials, but can be processed with the thermoplastic processing methods; they
are one of the fastest growing polymers materials which combine the elastic and
mechanical properties of crosslinked rubbers with the melt processability of
thermoplastics. In addition, TPEs find a lot of applications in automotive, buildings and
construction, wires and cables, etc.; besides their ability to reuse and recycle the
production scrap and waste. Polypropylene (Pp) is a commodity, with high melting point,
high chemical resistance, low density, with a balance between physical and mechanical
properties and easy processing at low cost. Nevertheless, Pp shows limitations for some
special applications, in terms of impact resistance; in order to minimize this
characteristic, an impact modifier, as Ethylene Propylene Diene Terpolymer (Epdm) can
be used. Due to different polarity and structure between the thermoplastic and
elastomeric phases, most thermoplastic elastomers are incompatible. Poor interfacial
adhesion and high interfacial tension between rubber and thermoplastic phases are main
reasons for incompatibility of these systems; in case of Pp and Epdm, there is a relatively
low interfacial tension (driving force for the transformation of a co-continuous structure
into a dispersed one) between Pp and Epdm (approximately 0.3 mN/m), reducing the rate
of breakup and facilitating the formation of a continuous structure. Pp/Epdm blends are
completely recyclable and reusable, safe to the environment, thus improving the overall
profitability of the process. Besides a higher impact resistance shown by Pp/Epdm
blends, it is possible that Epdm incorporation in Pp causes a reduction in tensile
resistance. In order to eliminate this interference and assuring a more comprehensive
application in automotive, buildings and construction, Pp/Epdm blends, rubber contents
ranging from zero to 30% (thirty percent), were subjected to gamma-irradiation, within
doses from 5 to 20 kGy. Isotactic Pp was considered for this work. Characterization
assessments included mechanical, thermal and rheological essays.