Recycling of Pretreated Polyolefin-Based Ocean-Bound Plastic Waste by Incorporating Clay and Rubber

Plastic waste found in oceans has become a major concern because of its impact on marine organisms and human health. There is significant global interest in recycling these materials, but their reclamation, sorting, cleaning, and reprocessing, along with the degradation that occurs in the natural environment, all make it difficult to achieve high quality recycled resins from ocean plastic waste. To mitigate these limitations, various additives including clay and rubber were explored. In this study, we compounded different types of ocean-bound (o-HDPE and o-PP) and virgin polymers (v-LDPE and v-PS) with various additives including a functionalized clay, styrene-multi-block-copolymer (SMB), and ethylene-propylene-based rubber (EPR). Physical observation showed that all blends containing PS were brittle due to the weak interfaces between the polyolefin regions and the PS domains within the polymer blend matrix. Blends containing clay showed rough surfaces and brittleness because of the non-uniform distribution of clay particles in the polymer matrix. To evaluate the properties and compatibility of the blends, characterizations using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and small-amplitude oscillatory shear (SAOS) rheology were carried out. The polymer blend (v-LDPE, o-HDPE, o-PP) containing EPR showed improved elasticity. Incorporating additives such as rubber could improve the mechanical properties of polymer blends for recycling purposes.

Influence of Selectively Localised Nanoclay Particles on Non-Isothermal Crystallisation and Degradation Behaviour of PP/LDPE Blend Composites

In immiscible polymer blend nanocomposites, nanoparticles can be localised either in polymer matrices or at the interface, invoking the simple question of how the spatial distribution of the nanoparticles and the resulting morphological changes affect the non-isothermal crystallisation and degradation kinetics. In this study, the non-isothermal crystallisation of polypropylene in polypropylene (PP)-rich compatibilised and non-compatibilised PP/low-density polyethylene (LDPE)/clay composites and their degradation are investigated. The non-isothermal crystallisation analyses show that the localisation of the clay particles in the blend composites has two opposing effects. First, the poorly dispersed clay particles at the PP/LDPE interface in the non-compatibilised blend composite has no significant effect on the crystallisation temperature of PP but allows the free movement of PP chains, resulting in a higher crystallinity of PP than that of PP in the neat blend. Second, the well-dispersed clay particles in the compatibilised blend composites disrupt the free movement of PP chains, resulting in a lower crystallisation temperature and crystallinity than that of PP in the neat blend. The influences of different selective localisations of clay particles on the activation energies of degradation are studied. The presence of maleated compatibilisers, clay, and the distribution of clay in the blend composite play important roles in determining the activation energies of degradation.