PSI - Issue 5

L. ALEXANDRESCU et al. / Procedia Structural Integrity 5 (2017) 667–674 Laurentia Alexandrescu/ Structural Integrity Procedia 00 (2017) 000 – 000

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INTRODUCTION Composite materials are very promising materials which are largely applied in both industrial and biomedical applications. Long time, the advance in the field of polymer science was assured by the developing of new polymers with controlled/predicted properties. Now, the trend is to design new materials with predicted, superior properties by using different polymers for preparing composite materials, to functionalize polymers or fillers for a better compatibility of the phases. (Abdou-Sabet, S., 2000.). Thermoplastic elastomers (TPE) are a unique class of polymers with many positive properties characteristic of vulcanized rubber, such as high wear, low compression and high flexibility, low processing time by conventional techniques specific to plastomers (injection). The high temperature required for processing into finished products is the only disadvantage of TPEs (Fazan H. and all 2006; Feldman, D. 2012]. The first dynamically vulcanized thermoplastic composite was put on the market in 1973 by W.K. Fisher (Fisher ,W. K. 1978), who partially crosslinked the elastomeric phase-EPDM of PP/EPDM compound with peroxide. Significant improvements in the properties of these compounds were achieved in 1978 by Coran, Das and Patel (Coran, Y.and all, 1995); by complete vulcanization of elastomer phase by dynamic vulcanization, while maintaining thermoplasticity of the compound. Dynamic vulcanization is an overlapping process consisting of plastomer melt compounding and selective crosslinking of elastomer which allows production of thermoplastic vulcanizates (TPV), many of which already have commercial applications, especially in the automotive and electronics sector. Developing a set morphology of a phase in polymeric compounds by melt mixing is a complex process during which the type of morphology of the resulting mixture (molecular or heterogeneous, mixed or homogeneous) is determined by the miscibility of the components, which depends on temperature, pressure and concentration. Most of the compounds contain polymeric components that are thermodynamically immiscible. They consist of separate phases, which may be present either in pure form of the specific components or in mixed state. (Naskar, K., 2004.; Rane1, A.V., V.K. Abitha, 2015) In the past 20 years polymeric structures have been reinforced with different organic or inorganic fillers with micron particles and lately with nanometric particles. In general, a unique combination of characteristics of nanomaterials, such as size, mechanical properties and low concentrations necessary to make changes in a polymer matrix, combined with available advanced techniques of characterization and simulation has generated a great interest on the part of researchers in the field of nanocomposites.( Deyrail, Y. and Cassagnau, P., 2013) The properties of a nanocomposite are greatly influenced by the size of component phases and mixing degree of the two phases, elastomer and plastomer. TPVs are obtained by melt compounding techniques in extrusion granulators with co-rotating twin screws and a high L (length) / D (diameter) ratio, continuous flow processing technology (Ellul et al. , 2004; Harrats et al. , 2006; Van Duin, M., 2010). The properties of the composites depend on the polymer, reinforcing agents, the type and amount of compatibilizer and their proportion in compounding and processing conditions. Therefore, the reinforcing agents properties must be known, they influence compound properties, and therefore the domain of interest (Thostenson and Chou, 2005; Koo, 2006; Yu-kun Chen and all 2013; Ionescu, Fand all 2008.). There are different types of nanoparticles that can be incorporated in the polymer matrix, selected according to the properties they have and their application. Rubber and plastics industry, as well as textile industry are domains where ZnO and TiO 2 is intensively used due to its antibacterial and antifungal activity. (Emamifar,A and all 2010). Its role is particularly important in terms of antimicrobial and UV protection. ZnO and TiO 2 has antibacterial and antifungal activity and is 1 of 5 Zn and Ti compounds that are currently accepted by the U.S. Food and Drug Administration (21CFR182.8991) (Kim, 2013; Shu-Cai Li, Ya-Na Li, 2010.). Antibacterial activity has been proven on various bacterial strains ( Staphyloccocus aureus, Staphylococcus epidermidis 1487, Streptococcus pyogenes, E. coli, E. coli O157:H7, Listeria monocytogenes, Bacillus subtilis, Bacillus atrophaeus , Pseudomonas fluorescens, Pseudomonas aeruginosa, Salmonella enteritidis, Salmonella typhimurium, Enterococcus faecalis , Enterobacter cloacae, Lactobacillus helveticus). . In another paper, Alexandrescu, L. (Alexandrescu and all 2016) have experienced nanocomposites PE/PE g-MA/EPDM/nanoZnO based polymeric nanocomposites, dynamically crosslinked with peroxide. The phisico mechanical test is To the limit of product specifications. Sulfur and accelerators vulcanization lead to much improved results compared to peroxide vulcanization. EXPERIMENTAL Materials. All composites contain the same two polymers: the EPDM elastomer (Nordell IP 3745P-DuPont) and the high density polyethilene (HDPE-SIDPEC, Egyptene), in the ratio 60:40.