Recycling Polymer Blend made from Post-used Styrofoam and Polypropylene for Fuse Deposition Modelling

Fuse deposition modelling (FDM) has become a revolutionary manufacturing technology as it offers numerous advantages, including freedom of fabrication, mass customisation, fast prototyping, and cost-effectiveness. Thermoplastic material is commonly used as feedstock for FDM process. The current state of material development, the recycled plastic material also can be used as printing material for FDM machine. Expanded polystyrene (EPS) has been extensively used as packaging materials for many industries but rarely be recycled, as its relatively large volume with minimal weight is unconducive for transportation. This research aimed to utilize EPS waste and turn it into FDM feedstock. This research also aims to enhance the properties of recycled polystyrene (rPS) made from EPS waste by blending it with polypropylene (PP). Different ratios of rPS/PP blends were prepared and extruded into FDM filament using filament extruder. The formulated filaments were printed into specimen using FDM machine. This research found the filament made from rPS/PP blends can be printed into specimen with good printing quality if the nozzle temperature controlled at 240° C with 120 % extrusion rate. With this printing parameter, the specimen printed with rPS/PP blend filament exhibit the greatest adhesion between the deposited layers without any visible voids or gaps. Besides, the printed specimen with rPS/PP blends possess lower tensile strength, but higher tensile modulus as compared to the printed specimen with neat rPS. The addition of more PP decreased both tensile strength and modulus of rPS/PP blends. On the other hand, the rPS/PP blends have higher thermal stability as the PP content increased. Overall, the rPS/PP blends filament shows a great potential as a feedstock material for FDM fabrication.

Nanosilicates in Compatibilized Mixed Recycled Polyolefins: Rheological Behavior and Film Production in a Circular Approach

Currently, plastic packaging represents a global challenge and has become a key point of attention for governments, media and consumers due to the visibility of the waste it generates. Despite their high resource efficiency, the perceived non-recyclability of polymeric films risks precluding them from being a relevant packaging solution in a circular economy approach. In this regard, the aim of this study was to implement a strategy to try closing the loop, via the mechanical recycling of post-consumer flexible packaging of small size (denoted as Fil-s) to obtain new films. In particular, two lots of Fil-s were used, which are PE/PP blends differing for the PP content and the presence of polar contaminants. The suitability for film blowing extrusion of these recycled materials, as such and after the addition of a compatibilizer and/or a lamellar nanosilicate, was evaluated. It was first evidenced that the difficulty of producing blown films with the pristine recycled materials, due to the frequent bubble breakages, occurring even at low draw ratios. Moreover, the shear and extensional rheological behavior of all Fil-s based systems was usefully correlated with their processability features, evidencing the key roles of the nanofiller to stabilize the bubble and of the compatibilizer to ensure a uniform film deformation, avoiding its premature breakage. Even if the adopted upgrading strategies allowed the production of blown films with both types of Fil-s, the different components of the recycled matrices were proven to significantly affect their processability and final film performances.

IDENTIFICATION OF BIODEGRADABLE POLYMERS AS CONTAMINANTS IN THE THERMOPLASTICS RECYCLING PROCESS

In this work, the presence of biodegradable polymers in recycled plastic materials was characterized using readily available techniques. Recycled polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET) were studied. The contamination of these plastics with polylactic acid (PLA), polyhydroxybutyrate (PHB) and thermoplastic starch (TPS) was simulated using 10 wt.% of the contaminant. Fourier transform infrared spectrometry (FTIR) and differential scanning calorimetry (DSC) were used as characterization techniques. In addition, the effect of aging on recycled products from PET blends contaminated with TPS and PHB was studied. The results show changes in the intensity of the FTIR spectra bands of the PS and PP blends contaminated with biodegradable polymers. By DSC, changes in the cold crystallization peak of recycled PET are observed when mixed with TPS and PHB. When the contaminant is PLA, the changes are masked due to the thermal characteristics of both materials. In PS, changes in the calorimetric curves are identified by the presence of PLA and PHB. Contamination with PLA, PHB and TPS hinders the processing of recycled PET after one year of storage due to the aging of the material.

Improving Rheological and Mechanical Properties of Various Virgin and Recycled Polypropylenes by Blending with Long-Chain Branched Polypropylene

Blends of two long-chain branched polypropylenes (LCB-PP) and five linear polypropylenes (L-PP) were prepared in a single screw extruder at 240 °C. The two LCB-PPs were self-created via reactive extrusion at 180 °C by using dimyristyl peroxydicarbonate (PODIC C126) and dilauroyl peroxide (LP) as peroxides. For blending two virgin and three recycled PPs like coffee caps, yoghurt cups and buckets with different melt flow rate (MFR) values were used. The influence of using blends was assessed by investigating the rheological (dynamic and extensional rheology) and mechanical properties (tensile test and impact tensile test). The dynamic rheology indicated that the molecular weight as well as the molecular weight distribution could be increased or broadened. Also the melt strength behavior could be improved by using the two peroxide modified LCB-PP blends on the basis of PODIC C126 or PEROXAN LP (dilauroyl peroxide). In addition, the mechanical properties were consistently enhanced or at least kept constant compared to the original material. In particular, the impact tensile strength but also the elongation at break could be increased considerably. This study showed that the blending of LCB-PP can increase the investigated properties and represents a promising option, especially when using recycled PP, which demonstrates a real “up-cycling” process.

Impact of Repetitive Recycling on Optical Properties of Virgin and Recycled Polypropylene Blends Based on Material Value Conservation Paradigm

Implementation of material value conservation (MVC) needs to be proven through research to determine impact upon plastic properties such as optical properties of virgin plastic and recycled plastic blends. Optical properties such as colour, transparency and gloss are important parameters for appropriate quality of plastic packaging. Degradation of optical properties occurs during recycling processes of plastic materials and the declining properties of recycled products could be improved by blending them with virgin materials. This research aims to reveal the impact of repetitive recycling on optical properties of virgin and recycled polypropylene (PP) blends based on MVC paradigm. The first step of this research was to determine composition of virgin PP and recycled PP blends. Proportion of 70% virgin PP and 30% recycled PP was selected as a blend composition. The next step of this research was repetitive recycling of virgin PP and recycled PP blends with implementation of MVC up to the 8th recycling stage. The specimens of plastic blends were made from the 1st, 2nd, 4th and the 8th recycling stage and then their optical properties were tested with the American Society for Testing Materials (ASTM) methods. Generally, degradation level of optical properties will increase during the recycling processes. Testing results show a slightly change of colour properties. Degradation level of gloss properties is gradually increased by a maximum degradation level at the 8th recycling stage as 17.46%. However, transparency had a maximum degradation level at the 4th recycling stage as 20.93%. It means that the plastic blends can be used as viable raw materials based on their optical properties with more attention to the gloss. Furthermore, the implementation of MVC will provide more benefits through extending the life cycle of recycled products, reducing virgin plastic consumption, optimizing the use of plastic waste and reducing plastic waste generation.

The reactive compatibilization of PLA/PP blends and improvement of PLA crystallization properties induced by in situ UV irradiation

The crystallization rate of PLA in PLA/PP blends increased after reactive compatibilization during a reactive extrusion process.

Antistatic and Thermal Properties of Poly(Lactic Acid)/Polypropylene/Carbon Nanotube Nanocomposites

The aim of this study is to investigate the influence of carbon nanotubes (CNT) on the antistatic and thermal properties of poly(lactic acid)/polypropylene/carbon nanotubes (PLA/PP/CNT) nanocomposites. PLA/PP (blend ratio = 60:40) containing CNT (loading 1.0 to 2.5 phr) was melt-compounded followed by compression moulding. The antistatic properties of PLA/PP/CNT nanocomposites achieved at 2.5 phr CNT loading. Thermogravimetric analysis (TGA) results indicated that the thermal stability of PLA/PP/ CNT nanocomposite was higher than PLA/PP blend. Differential Scanning Calorimetry (DSC) results demonstrated that CNT reduced the cold crystallisation temperature of PLA, while increased the crystallisation temperature of PP, which evidenced the nucleatingability of CNT in the PLA/PP blends.