Polypropylene Composites Research Articles

Improving the Long-Term Mechanical Properties of Thermoplastic Short Natural Fiber Compounds by Using Alternative Matrices

Wood plastic composites (WPCs) offer a means to reduce the carbon footprint by incorporating natural fibers to enhance the mechanical properties. However, there is limited information on the mechanical properties of these materials under hostile conditions. This study evaluated composites of polypropylene (PP), polystyrene (PS), and polylactic acid (PLA) processed via extrusion and injection molding. Tests were conducted on tensile and flexural strength and modulus, heat deflection temperature (HDT), and creep analysis under varying relative humidity conditions (10% and 90%) and water immersion, followed by freeze—thaw cycles. The addition of fibers generally improved the mechanical properties but increased water absorption. HDT and creep were dependent on the crystallinity of the composites. PLA and PS demonstrated a superior overall performance, except for their impact properties, where PP was slightly better than PLA.

Multiscale analysis of the mechanical properties and interface damage mechanisms of carbon fiber reinforced polypropylene composites

AbstractIn this article, the mechanical properties of carbon fiber reinforced polypropylene (CF/PP) composites at different carbon fiber (CF) mass fractions were systematically investigated. A comprehensive examination is provided through the integration of experimental testing, numerical simulation, and theoretical analysis, revealing the enhancement effects of CF on the polypropylene (PP) matrix across multiple scales. Experimental results demonstrated that the incorporation of CF significantly impedes crack propagation and enhances the fracture resistance of the composites. Specifically, at a CF mass fraction of 15%, the elastic modulus of the composites is enhanced by 21.7% compared with pure PP, while the tensile strength increases by 40.9%–43.2%. The addition of maleic anhydride grafted polypropylene (MAH‐g‐PP) as a compatibilizer significantly improves the interfacial compatibility between CF/PP. Furthermore, finite element simulations revealed the damage evolution process at the CF/PP interface during tensile loading. Based on the Mori‐Tanaka model, the elastic modulus was predicted, aligning well with experimental and simulated results. This research offers a scientific basis for the design and application of CF/PP composites and contributes to the advancement of high‐performance composites.Highlights CF/PP composites show enhancements in mechanical properties with CF addition MAH improves interfacial adhesion between CF and PP, boosting tensile strength Multiscale experimental and FEA studies reveal CF/PP interface damage mechanisms Mori‐Tanaka model accurately predicts the elastic modulus of CF/PP composites

Flame Retardancy and Heat Shielding in Green Polypropylene Composites Using Biohybrid Fibers and Agro-Waste Fillers.

The current work presents the flame-retardant performance of hybrid polypropylene composites, reinforced with specific short woven flax fabrics (SWFs), short basalt fibers (BFs), and rice husk powder (RHP), using polypropylene grafted maleic anhydride (MAPP) as the coupling agent. Horizontal burning test (HBT), microcalorimeter test (MCT), and cone calorimeter test (CCT) were conducted on these composites. The formulations used were 25% SWF/PP, 25% SWF/20% BF/PP, and 25% SWF/20% BF/PP with 6% RHP and 25% SWF/20% BF/PP with varying RHP contents (6, 12, and 18%) in combination with 6% MAPP. A peak heat release rate (pHRR) reduction of 14.42% was recorded in microcalorimeter test results. However, cone calorimeter test results indicated a reduction of 80.95% in pHRR and 23.84% in total heat release rate (THR). Furthermore, the emissions of CO and CO2 were reduced by 68 and 67%, respectively, in the 25SWF/20BF/PP.6MAPP-18RHP composite compared to pure PP, indicating an overall improvement in combustion efficiency. Fire performance index (FPI) also improved remarkably: FPI increased by 130% and fire growth index (FGI) improved by 81.34%. Moreover, the horizontal burning test showed an improved performance, with the burning rate further reduced by 11.10% compared to that of the 25% SWF/PP composite. These results highlight the synergy among natural fibers, agro-waste fillers, and MAPP in improving flame retardancy of polypropylene composites, and hence their potential application in automobiles and construction, where the demand for fire safety is very high.

Biomimetic flow field flame retardant modification of sisal fiber and its polypropylene composites

The lumen of sisal fiber provides a good space for loading flame retardants and constructing a three-dimensional flame-retardant network, effectively improving the flame retardancy of their polymer composites. In this study, we combined water/nutrient transport mechanism of plant fiber with layer-by-layer self-assembly technology, innovated a biomimetic flow field flame retardant modification method and successfully deposited ammonium polyphosphate (APP) and polyethyleneimine (PEI) into sisal fiber lumen. After 20 cycles modification, the flame retardants in fiber increased to 18.36wt%. Its TG residue achieved to 43.23% from 17.35% (unmodified) and its limited oxygen index (LOI) value achieved to 39.1% from 20.7% (unmodified). Compared to directly immersing fiber in APP/PEI solution, this method mitigated the blockage of flame retardants at lumen entrance and realized a uniformly deposition in lumen interior. When blending this modified fiber with polypropylene (PP) at 30wt% (the flame retardant content is only about 4.65wt%), the composite TG residue increased from 3.10% (unmodified) to 15.77%, and its LOI value increased from 19.4% (unmodified) to 23.2%. This composites also has better flame retardancy than APP/PEI directly dispersed in PP matrix (TG residues 11.10%, LOI value 21.1%). For sisal fiber polymer composites, employing fiber lumen as flame retardant carrier could improve its flame retardancy efficiently. The carried flame retardants inhibit the combustion of flammable sisal fiber, and the constructed flame-retardant network restrict PP matrix combustion.

Investigation of mechanical, morphological and thermal properties of waste glass powder and wood flour reinforced polypropylene composite

Investigation of mechanical, morphological and thermal properties of waste glass powder and wood flour reinforced polypropylene composite

Flame-retardant effects of NH2-MIL-53(Al) in combination with phosphorus-containing and nitrogen-containing flame retardants on polypropylene

Polypropylene (PP) flammability poses great fire risks for its application. A metal-organic framework (MOF), NH2-MIL-53(Al), was synthesized and subsequently integrated into PP, the flame-retardant efficacy in conjunction with piperazine pyrophosphate (PAPP) and melamine cyanurate (MCA) was additionally examined. When the total mass fraction of the additives was 25 %, the limiting oxygen index (LOI) of PP composite reached 31.1 %, it also passed the UL-94 test with a V-0 rating. The peak heat release rate (pHRR) and the total heat release rate (THR) was reduced by 88.55 % and 79.75 %, respectively, compared with the pure PP. The char residual char percentage increased to 8.02 %. The Tensile Strength reached 30.1 MPa. The results indicate that adding NH2-MIL-53(Al) significantly enhanced the flame retardancy and thermal stability of PP composites, without significantly affecting their mechanical properties, which offers a novel potential direction for the advancement of polymer flame retardants (FRs).

In English

Iron-containing polypropylene (PP) composites were synthesized by precipitating iron(III) nitrate from aqueous solutions of varying concentrations onto a polypropylene matrix, followed by drying at ≤110°C and heating at ≤230°C temperatures. The resulting composites were characterized using scanning electron microscopy combined with energy-dispersive elemental analysis (SEM/EDS), X-ray diffractometry (XRD), and electron magnetic resonance (EMR).The study revealed that the composites obtained through thermal decomposition of iron(III) nitrate from aqueous solutions on a polypropylene matrix, with subsequent heat treatment at 220°C, form a two-phase system consisting of isotactic polypropylene and magnetite. SEM/EDS data showed a non-uniform distribution of the iron-containing component on the PP surface, even in samples with less than 1% by weight of the iron component. FMR spectra indicated the formation of superparamagnetic and ferromagnetic particles within the polypropylene matrix, attributed to nanosized magnetite particles of varying dimensions.Theoretical spectra were calculated using the Landau-Lifshitz-Gilbert equation, considering Lorentzian, Gaussian, and Dyson resonance signal shapes. These theoretical spectra, which accounted for the dependence of g-factor values and line widths of the FMR spectra on particle size, were adjusted to match the experimental data to clarify the magnetic resonance characteristics of the iron-containing particles.The study concluded that magnetite particles formed during the thermal decomposition of iron(III) nitrate deposited from an aqueous solution onto the polypropylene matrix do not interact significantly with the polypropylene. These particles remain mobile on the polymer surface and are prone to aggregation, posing challenges for achieving a uniform composite material.

Comparative Effects of Carbon Fiber Reinforcement on Polypropylene and Polylactic Acid Composites in Fused Deposition Modeling.

Comparative Effects of Carbon Fiber Reinforcement on Polypropylene and Polylactic Acid Composites in Fused Deposition Modeling.

Effects of Consolidation Parameters on Flexural Behavior of Polypropylene/Glass Fiber Thermoplastic Composites

In this study, the flexural behavior of glass fiber-reinforced polypropylene (GFR-PP) composites was systematically investigated under three-point bending conditions to evaluate the impact of key production parameters. Composite plates with a thickness of 4 mm were fabricated using a stepped mold under varying pressure levels (10, 20, and 30 bar) and durations under pressure (5, 10, and 20 minutes). The specimens were prepared according to ASTM standards to ensure consistency and reliability. The primary objective of this study was to understand how production parameters influence the mechanical properties of GFR-PP composites. The results indicated that the combination of low pressure (10 bar) and longer durations (20 minutes) led to superior flexural strength and enhanced fiber-matrix adhesion due to optimized consolidation, with a maximum flexural strength exceeding 500 MPa. In contrast, higher pressure levels (30 bar) resulted in fiber deformation and reduced mechanical performance. This work provides critical insights into the optimization of production parameters to achieve high-performance GFR-PP composites, with potential applications in aerospace and other lightweight structural components requiring high mechanical strength and durability.

Effect of particle size and loading of cherry tree branch fillers on the mechanical and viscoelastic properties of polypropylene composites

Effect of particle size and loading of cherry tree branch fillers on the mechanical and viscoelastic properties of polypropylene composites

Improved fracture toughness of glass fibers reinforced polypropylene composites through hybridization with polyolefin elastomers and polymeric fibers for automotive applications

AbstractPolypropylene‐reinforced composites mostly exhibit a trade‐off between stiffness and toughness. In this study, the impact of incorporating polyolefin elastomer (POE) and Polyvinyl Alcohol (PVA) fibers as individual and hybrid reinforcement to glass fiber‐reinforced polypropylene composite in the presence of a compatibilizer was explored. The main focus was on achieving an optimal stiffness/toughness balance. Several ternary and quaternary hybrid composite systems were developed and analyzed. All components were melt‐blended using a twin‐screw extruder and then injection molded for subsequent mechanical and morphological analysis. A significant stiffness of approximately 2.4 GPa Young's modulus, and notched izod impact strength ranges between 250 and 400 J/m can be attained with the quaternary hybrid system, PP/GF/POE/PVA fibers. Its performance can be controlled by altering the POE/PVA fibers ratio to achieve the targeted stiffness/toughness balance. These values represent a remarkable increase, with Young's modulus being 120% higher and the izod impact strength surpassing that of the control sample by over 800%. The achieved results aligned with the requirements of the automotive industry, so the developed composites could have a high potential for automotive parts.Highlights Ternary and quaternary hybrid systems were fabricated by a twin‐screw extruder. An improvement of 120% in stiffness and 800% in toughness was observed. Distinct micromechanical deformation mechanisms were identified. Remarkable stiffness‐toughness balance was achieved. Reduction in weight makes the system suitable for automotive applications.

Rotomolded polypropylene‐ignimbrite composites: Giving a second life to mineral dust wastes

AbstractThe possibility of rotomolding polypropylene (PP) composites with high loadings of a silica‐based dust of ignimbrite, a byproduct of volcanic stone extraction is demonstrated. This study aims to establish the properties of composites with various ratios of mineral dust as a filler in PP matrices at loadings from 5 to 30 wt%, ultimately transforming mining residues into a valuable resource for composite production and creating a value chain around the traditional mining industry. Once the composites were obtained, they were subjected to several characterization techniques to comprehensively assess their mechanical and thermal properties. In general, a high percentage of ignimbrite powder has resulted in a reduction in the mechanical properties of neat PP, although no significant changes were observed for composites at lower loadings. Furthermore, the incorporation of this mineral material modified the thermal properties of the PP, enhancing its thermal stability. The blending of the matrix and filler resulted in a reduction in both the melting crystallization temperatures for highly‐filled composites. Rotomolded items with good aesthetics, with stone‐like appearance, were obtained without any modification on the mineral dust or even without any melt compounding, therefore not increasing the energy consumption during the composites production.Highlights Composites production is a suitable strategy for valorization of mineral residues. Welded ignimbrite residual dust has been used for the first time in composites. Mineral dust has been successfully used in composites obtained by rotomolding. Polypropylene with up to 30% of the stone dust can be processed. Good aesthetics and mechanical features can be obtained with mineral wastes.

Development of an Automotive-Relevant Recycling Process for Paper Fiber-Reinforced Polypropylene Composites

The automotive industry is under growing pressure from regulatory agencies to improve the recyclability of its plastic components. Simultaneously, manufacturers are adopting natural fiber composites in vehicles to reduce their carbon footprint and decrease reliance on petroleum-based materials. This presents a challenge at vehicle end-of-life, however, as natural fiber-reinforced polymers are substantially more difficult to recycle than their unreinforced counterparts. This study investigated the development of a mechanical recycling process for paper fiber-reinforced polypropylene composites, focusing on the impact of injection molding parameters—specifically, injection temperature and rate—on the thermal, mechanical, and water uptake properties of the composites. The results showed that processing temperature had a greater influence on composite performance than injection rate, with some limited interaction effects between the two. Higher processing intensity damaged the paper fibers, increasing the number of nucleation sites and resulting in greater polypropylene crystallinity. These structural changes reduced tensile properties at higher intensities, while flexural properties improved. Objective function analysis was applied to identify optimal processing conditions, balancing these competing trends. Overall, the findings demonstrate that paper fiber-reinforced polypropylene composites can be recycled into automotive-relevant injection molding compounds using conventional plastic manufacturing techniques, though careful tuning of processing parameters is essential to achieve optimal performance.

Effect of soft and hard segments ratio of waterborne polyurethane on the properties of modified basalt fiber reinforced polypropylene composites

Effect of soft and hard segments ratio of waterborne polyurethane on the properties of modified basalt fiber reinforced polypropylene composites

Fabrication of microfibrillated cellulose reinforced polypropylene composites assisted by a synergistic strategy of pre‐quaternization and paper‐making process

AbstractTo tackle the ease of aggregation issue of highly hydrophilic microfibrillated cellulose (MFC) in polypropylene (PP) that thus results in an undesired reinforcing effect, this work developed an effective and industrially feasible strategy combining pre‐quaternization of pulp fibers with paper‐making process to fabricate PP/MFC composite with enhanced performance. Effects of MFC consistency, maleic anhydride grafted polypropylene (MAPP) content, and plasma treatment of chopped PP fibers on the mechanical and thermal properties of resultant composites were systematically investigated. The surface‐quaternized MFC obtained by a low‐consistency refiner (L‐MFC) exhibited a higher aspect ratio and degree of fibrillation than the corresponding surface‐quaternized MFC obtained by a high‐consistency one (H‐MFC). It was found that there existed a synergistic effect between pre‐quaternization and the paper‐making process in promoting the dispersion of MFC in PP. As compared with L‐MFC, a higher reinforcing efficiency on PP was achieved for H‐MFC, which was because the former one was more prone to form the fibril aggregates in the PP matrix. Due to both the entangled network of MFC and its nucleation effect on PP, the heat deflection temperature (HDT) of resulting composites was largely increased up to 159.9°C, an increase of 68.7°C with respect to that of PP.Highlights The H‐MFC yielded a superior reinforcement on PP than L‐MFC. The optimum mechanical properties of PP/composites were achieved at 15% MAPP. Interfacial bonding between PP and H‐MFC was enhanced by plasma treatment. An increase in Tc of the PP matrix was noted for PP/MFC. A maximum increase of 159.9°C in HDT was achieved for PP/MFC.

Influence of Lignin Type on the Properties of Hemp Fiber-Reinforced Polypropylene Composites.

Increasing environmental awareness has boosted interest in sustainable alternatives for binding natural reinforcing fibers in composites. Utilizing lignin, a biorenewable polymer byproduct from several industries, as a component in polymer matrices can lead to the development of more eco-friendly and high-performance composite materials. This research work aimed to investigate the effect of two types of lignin (lignosulfonate and soda lignin) on the properties of hemp fiber-reinforced polypropylene composites for furniture applications. The composites were produced by thermoforming six overlapping layers of nonwoven material. A 20% addition of soda lignin or lignosulfonate (relative to the nonwoven mass) was incorporated between the nonwoven layers made of 80% hemp and 20% polypropylene (PP). The addition of both types of lignin resulted in an increase in the tensile and bending strength of lignin-based composites, as well as a decrease in the absorbed water percentage. Compared to oriented strand board (OSB), lignin-based composites exhibited better properties. Regarding the two types of lignin used, the addition of lignosulfonate resulted in better composite properties than those containing soda lignin. Thermal analysis revealed that the thermal degradation of soda lignin begins long before the melting temperature of polypropylene. This early degradation explains the inferior properties of the composites containing soda lignin compared to those with lignosulfonate.

Fabrication and Functional Behavior Studies of Polypropylene Composite Containing Hybrid Reinforcements

<div>Hybrid reinforcement-made polypropylene (PP) composites are beneficial over monolithic PP and utilized for various engineering and non-engineering applications. The present investigation of PP hybrid composites is developed with 10 percentages of weight (wt%) of E-glass fiber embedded with 0–6 wt% of silicon carbide via compression technique associated with hot press. E-glass fiber and SiC influencing wear rate, tensile strength, and microhardness behavior of PP and its composites are experimentally investigated. The peak loading of SiC as 6 wt% into PP/10 wt% E-glass fiber is recorded as better wear resistance (0.021 mm<sup>3</sup>/m), maximum tensile strength value (54.9 MPa), and highest hardness (68 HV). Moreover, the investigation results of hybrid PP composite are better resistance to wear and hiked tensile and hardness behavior compared to monolithic PP. This PP/10 wt% E-glass fiber/6 wt% of SiC hybrid composite is adopted for high-strength to lightweight sports goods applications.</div>

Effect of the carding process and fibre length on the properties of pineapple leaf fibre and reinforced polypropylene composites

In this work, a greener approach, the carding process, was used to remove extraneous materials from the surface of pineapple leaf fibre (PALF) instead of using conventional chemical treatments. PALF was cut into three lengths and processed using a carding machine for different numbers of passages. Carded PALF and polypropylene (PP) fibres were then blended uniformly at 50% weight percentage through the carding process. The mixed fibres were further processed by a gill-drawing machine to produce oriented PALF-PP silvers, which were consolidated in a compression moulding machine to fabricate the unidirectional composites. The experimental results indicated that the increase in the number of carding passages and PALF cut-length increased the surface fibrillation, roughness and crystallinity, and reduced the water contact angle (i.e., increased hydrophilicity) of carded PALF. The thermal insulation performance of the composites improved in cases of shorter PALF length after five carding passages and coarser PP fibres, but at the same time, the water absorbency also increased, indicating reduced water resistance of such composites.

Optimization of Compression Molding Parameters and Lifecycle Carbon Impact Assessment of Bamboo Fiber-Reinforced Polypropylene Composites.

Driven by global carbon neutrality goals, bamboo fiber-reinforced PP composites have shown significant potential for automotive applications due to their renewability, low carbon emissions, and superior mechanical properties. However, the environmental complexities associated with compression molding process parameters, which impact material properties and carbon emissions, pose challenges for large-scale adoption. This study systematically optimized the compression molding process of bamboo fiber-reinforced PP composites through a three-factor, five-level experimental design, focusing on preheating temperature, preheating time, and holding time. Additionally, an innovative life cycle assessment (LCA) was conducted to evaluate the environmental impact. The results indicated that at a preheating temperature of 220 °C, preheating time of 210-240 s, and holding time of 40-50 s, the material achieved a tensile strength of 35 MPa and a flexural strength of 45 MPa, with a 15% reduction in water absorption. The LCA further highlighted energy consumption, the compression molding process, and material composition as the primary contributors to carbon emissions and environmental impacts, identifying key areas for future optimization. This study provides an optimized framework for compression molding bamboo fiber-reinforced PP composites and establishes a theoretical foundation for their low-carbon application in the automotive industry. Future work will explore the optimization of bamboo fiber content and process parameters to further enhance material performance and reduce environmental impact.

Modeling Deformation Properties of Composite Polypropylene Threads Filled with Carbon Nanofibers

Modeling Deformation Properties of Composite Polypropylene Threads Filled with Carbon Nanofibers