Papers by Keyword: Polypropylene (PP)

Abstract: This study evaluates the processability of recycled polypropylene (rPP) in pellet-based material extrusion (MEX) to support more sustainable additive manufacturing. Virgin polypropylene (PP) and post-consumer rPP obtained from end-of-life woven builder bags were processed in neat form and as PP/rPP blends with increasing recycled content. Melt-flow behavior was characterized using a Technological Melt Flow Index (TMFI), a process-specific metric reflecting the combined effects of temperature and screw rotation. Disk-shaped specimens were printed to assess deposition behavior through the build-up rate (BUR), which integrates shear flow in the extruder and elongational deformation during deposition. TMFI results show that rPP exhibits markedly higher flowability than virgin PP below 200°C, indicating potential for lower-temperature, energy-efficient processing. In contrast, printing experiments reveal that BUR systematically decreases with increasing rPP content. This trend indicates a transition to an elongation-dominated deposition regime, where rPP displays higher resistance to extensional deformation during deposition, resulting in narrower roads and reduced spreading. Regression analysis confirms that BUR is governed primarily by flow-rate setting (F%) and nozzle speed (Sp%), whereas nozzle temperature Te (°C) has only a minor influence within the investigated window. Overall, the results demonstrate the competing rheological effects introduced by recycling and highlight the need for tailored parameter optimization to enable higher rPP incorporation in pellet-based 3D printing.

Abstract: The influence of filler type and content on the wettability and interfacial bonding between thermoplastic elastomer (TPE) and polypropylene (PP) by using the injection overmolding process was investigated in this study. Calcium carbonate (CaCO₃) and talcum (Talc) masterbatchs, ranging from 0 to 40 percent by weight (wt%), were mixed into the PP matrix as fillers. The bond strength of TPE overmolded onto PP composites was characterized by the tensile and tear tests. Good compatibility was observed between TPE and PP filled with various amounts of CaCO₃ and Talc. In the case of the tensile test, the crack initiation stress, ultimate tensile strength, strain at break, and bond energy were found to decrease with increasing filler content. The results obtained from the tear test indicated that the propagation strength, ultimate tear strength, strain at break, and bond energy of injection overmolded TPE-PP filled with various CaCO₃ contents did not significantly change compared to those obtained from Talc. This can be attributed to the high reinforcing efficiency of Talc in comparison with CaCO₃, which can enhance the stiffness and thermal resistance of the PP matrix. As a result, the contact area becomes more resistant to molecular diffusion of TPE chains, particularly at high Talc loadings (30 and 40 wt%), leading to the reduction of interfacial bonding.

Abstract: In this study, a multifunctional air filtration material was developed by coating polypropylene (PP) nonwoven fabric with a chitosan/TiO₂ (P25) composite. The aim was to enhance air filtration efficiency. The chitosan–P25 composite was applied onto the PP nonwoven via a solution spray method followed by drying. Scanning electron microscopy (SEM) analysis revealed a uniform coating layer with good adherence to the PP fiber surface. X-ray diffraction (XRD) analysis confirmed the presence of crystalline TiO₂ in the P25 phases, as well as the semi-crystalline nature of the PP substrate. Air permeability tests showed a moderate reduction in air flow rate due to surface coating, while maintaining acceptable breathability for filter applications.

Abstract: This study aims to determine the key thermal parameters of plastic waste degradation, specifically polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS), using differential scanning calorimetry (DSC), differential thermogravimetry (DTG), and thermogravimetric (TG) analysis. The thermal stability of these materials was evaluated by analyzing residual solid and wax quantities, conversion percentages, liquid and gas product yields, and process duration. Experiments were conducted at 550–600°C with a heating rate of 50°C/min. Key thermal parameters investigated include onset decomposition temperature, temperature at 50% conversion, completion temperature, maximum DTG temperature, peak DTG value, melting point, and pyrolysis temperature. The activation energy for mass loss was calculated, ranging from 35 to 68 kcal/mol, with PS exhibiting the highest thermal stability (68 kcal/mol). The degradation conversion efficiency ranged from 85% to 99%. Notably, PET pyrolysis produced significantly more solid residues (0.136–0.150 g/g₀) than PP and PS (0.006–0.088 g/g₀). These findings provide valuable insights into the thermal behavior of plastic waste, supporting advancements in waste management and energy recovery applications.

Abstract: The exponential increase in global plastic wastes dangerously impacts the environment and human health. In this study, Polyethylene Terephthalate (PET), High-density Polyethylene (HDPE), Polypropylene (PP), and Polymethyl methacrylate (PMMA) were recycled into sandwich panels and polymer blends. Recycled PET (rPET) fibers, with 25 and 50 fibers, were used as the middle layer for the sandwich panels. The face layers were made from the recycled HDPE (rHDPE), recycled PP (rPP), and recycled PMMA (rPMMA). The weak interaction between rPET fibers and the face panels resulted in low mechanical performance. The sandwich panel with rPMMA as the face layers and 25 rPET fibers as the core exhibited good overall mechanical performance. The stiffness of sandwich panels was improved. The polymer blends were prepared using rPET at 70 wt% and other plastic wastes at 30 wt%. The addition of a compatibilizer can enhance the mechanical properties of polymer blends. The rPET/ rPP blend and rPET/ rHDPE blend showed slightly higher mechanical performance compared to the rPET/ rPMMA blend. All polymer blends exhibited higher flexural strength, impact strength, and hardness compared to neat rPET.

Abstract: Plastic is now regarded as the third most polluting waste source on a global scale, with its volume rising rapidly as the global population increases. Recycling plastics will help prevent serious environmental threats and add value to plastic waste by incorporating them into various applications, such as construction. Previous research primarily focuses on the investigation of replacing aggregates with plastic wastes in manufacturing concrete. There is a lack of study pertaining to the partial replacement of fine aggregates with plastic waste in producing PPB. In this study, PPB is produced by partially replacing fine aggregates with HDPE and PP plastic wastes. Results show that the 15% HDPE and 15% PP plastic waste replacement of fine aggregates exhibited maximum compressive strength at 11.1 MPa and 9.9 MPa, respectively. The maximum average density recorded was 2678.026 kg/m3, which shows a 23.95% increase compared to the reference block. Additionally, the replacement improved the infiltration rate of PPB, recording a maximum increase of 10% plastic waste replacement. The PPB with 15% HDPE replacement is identified as the optimum mixture and is best utilized in low-traffic areas.

Abstract: Materials of thermoplastic polymer when they break is usually thrown away, or is recycled which requires a long process. The purpose of this study is splicing the broken thermoplastic polymer using hot gas hand welding with different variations of welding wire/electrodes. Materials of thermoplastic polymer used are Polyethylene (PE), Polypropylene (PP), and Polyvinyl chloride (PVC) by using welding wire like the three materials. The method is carried out by using hot gas hand welding, there are two materials that cannot be connected, namely PE with PVC welding wire, and PP with PVC welding wire. The permeable liquid penetrant test is PP with PE welding wire, and PVC with PE welding wire. The longest elongation is PE with PE welding wire is 15.96% and the best of bending result is PVC with PVC welding wire reach value 181.2 kgf/mm². The microstructure was all described in Scanning Electron Microscopy (SEM) observations.

Abstract: Sugarcane bagasse fiber reinforced polypropylene (PP) based composites were prepared by compression molding. The fiber content was 40% by weight. Tensile strength (TS), tensile modulus (TM) and elongation break (Eb%) of the composites were found to be 51MPa, 1414 MPa and 14% respectively. The TS, TM and Eb% of the PP sheet were 25 MPa, 456 MPa and 76% respectively. Due to fiber reinforcement, an increase of 102% TS and 210% TM, was noticed. Water uptake test was carried out by immersing the composite sample in deionized water and it was noticed that water uptake was lower for sugarcane bagasse fiber reinforced PP composite. Transform Infrared Spectroscopy was employed for functional groups analysis of the fabricated composite.

Abstract: Fully utilisation of urban wastes such as polymer waste is considered as promising step to save the environment besides contributing to the production of Carbon Nanomaterials (CNMs) and their insight in mechanism involved. In this work, CNMs were successfully synthesised using polypropylene (PP) waste as carbon precursor via Chemical Vapour Deposition (CVD). Ferrocene was used as metal catalyst whereas argon was used as purging gas. The CVD were operated at various reactor temperatures to assess the possibility of CNMs growth at 600°C, 700°C, 800°C, 900°C, and 1000°C. The reaction time and argon flow rate were fixed at 90 minutes and 85 ml/min, respectively. The production of CNMs started at reactor temperature of 700°C and increased steadily from 0.0178 g to 0.2950 g with elevated temperature up to 1000°C. The diameter distribution of synthesised-CNMs reduced with the increased of reactor temperature. The XRD patterns revealed a sharp diffraction peak at around 26^o (002) and broad diffraction peak at around 44^o (111) which was proven to be Carbon Nanotubes (CNTs). Reactor temperature of 800°C considered as the best temperature to synthesis small diameter of CNMs in high quantity.

Abstract: Pineapple Leaf Fiber (PALF)-reinforced polypropylene (PP) based composites were prepared successfully by conventional compression molding technique. Different percentages (25,30,35, 40 and 405% by weight) of fiber were used to prepare composites. Tensile Strength (TS), Tensile Modulus (TM), Elongation at Break (Eb %), Bending Strength (BS), Bending Modulus (BM) and Impact Strength (IS) were evaluated. The 45 wt% PALF/PP composite exhibited an increase of 132% TS, 412% TM, 155% BS, 265% BM, and 140% IS with respect to the matrix material (PP). Fourier Transform Infrared (FTIR) Spectroscopy was employed for functional group analysis of PALF/PP composites. For all percentages of fiber, the composites demonstrated lower water uptake. The fabricated composites were immersed in alkali solution (Sodium hydroxide solution, 3%, 5% and 7% by weight) for 60 min and showed low TS, TM and Eb% compared to control composites.