Effect of Compatibilisers on Mechanical, Barrier and Antimicrobial Properties of iPP/ZnO Nano/Microcomposites for Food Packaging Application

It is investigated the effects of the addition of three PPgMA, with different molecular weight and maleic anhydride content, on the structure, morphology, mechanical, thermal and antimicrobial properties and oxygen permeability of iPP/ZnO 98/2 wt% composite. The composition of iPP/PPgMA/ZnO composites is fixed at 88/10/2 wt%, that is, about 10 wt% of iPP is substituted with PPgMA. The composites are prepared via melt mixing by using a twin-screw extruder. The ZnO is obtained in a preindustrial scale spray pyrolysis platform. The Fourier Transform Infrared spectroscopy indicates that the ZnO particles, in all the ternary composites, react with maleic anhydride groups of PPgMA. From the analyses of the mechanical properties, permeability to oxygen and antibacterial activity agaist E.Coli, it is concluded that the best compatibiliser among the three is PPgMA with 1.4% of MA and Mw 65,000, but the antibacterial activity is much lower than that of the binary iPP/ZnO 98/2 wt%. Moreover, it is found that the antibacterial activity is more efficient for the film that presents clusters of the ZnO particles on the surface than the film with ZnO particles smaller and better distributed on the film surface, and embedded in it

Polyolefins based hybrid nanocomposites

This thesis aimed at completing the study of the properties of iPP modified with an hydrogenated oligomer resin (Escorez-ESC) and at improving these properties by making nanocomposites with the addition of two clays (modified one 67G and unmodified one HPS) for possible use in the food packaging sector. The study of the structure, morphology and thermal, rheological, mechanical and barrier properties of the binary and ternary systems have been reported as function of composition, kind of constituents and preparation conditions. Moreover for all the systems the study on crystallization in situ under shear and during cooling is reported. From the results obtained the main highlights can be draw: i) the iPP is not intercalated between clay layers. The clay 67G is well dispersed in the matrix (iPP and iPP/ESC blends), whereas HPS forms large agglomerates. ii) The iPP/ESC5%/67G presents similar mechanical properties to iPP and improved barrier properties respect to iPP, it could be a good starting point for investigations in order to use the ternary systems in the food packaging. For these systems the improvement of dispersion of the clay nanoparticles must be achieved by optimizing the preparation conditions and the mixing procedures. iii) The rheological results show that there is a good swelling of the clay HPS and the ESC. HPS should have a better affinity for the oligomer respect to iPP and should be dispersed more in this phase respect to iPP. At this point the modality of blending seems become very important. A masterbach made of Escorez and HPS could present structure intercalated/exfoliated. iv) the in-situ SAXS experiments have revealed that the temperature at which crystal growth rate is at a maxima is strongly dependent on the temperature at which the shear flow was applied. In the melt after shear flow, the polymer chains which were extended will be relaxing towards isotropic state. If crystallisation takes place before the chains are full relaxed, the extended chains acts as row nuclei which has 2 consequences. The first is a high level of common orientation of the crystals and second that crystallisation occurs at a higher temperatures, essential the chains are nucleating agents. As the polymer will crystallise in any event, the questions is really how much is directed by row nuclei and how much by randomly arrange nuclei. This changes the crystallisation temperature and the level of anisotropy. The clay platelet orientation is affected by flow but it does not template the crystallisation, although clearly the crystallisation behaviour depends on the details of the clay and other components

Preparation and characterization of isotactic polypropylene​/zinc oxide microcomposites with antibacterial activity

In this study, we investigated the influence of ZnO particles obtained by spray pyrolysis with submicron dimensions on the structure, morphology, thermal stability, photodegradation stability, mechanical and antibacterial properties of isotactic polypropylene (iPP)/ZnO composites prepared by melt mixing. The results of the morphological analyses indicate that, despite the surface polarity mismatch between iPP and ZnO, the extrusion process and the unique characteristics of the utilized particles allow a composite with a fair distribution of particles to be obtained, although some agglomeration phenomena can occur, which primarily depends on the composition of the composite. The addition of ZnO particles imparts significant improvements on the photodegradation resistance of iPP to ultraviolet irradiation, which confirms that ZnO particles act as screens for this type of radiation. The thermal stability of the iPP/ZnO composites is improved with respect to that of neat iPP and increases with the content of ZnO. The iPP/ZnO composites exhibit significant antibacterial activity against Escherichia coli. This activity is dependent on exposure time and composition