Glass Fiber Reinforced Polypropylene Composites Research Articles

Influence of Processing Parameters in Injection Molding on the Properties of Short Carbon and Glass Fiber Reinforced Polypropylene Composites

Short-fiber reinforcement is a potent approach to improving the material properties of injection-molded parts. The main consideration in such reinforced materials is to preserve the fiber length, as this is the major influence on the properties of a given composite. The aim of this work was to investigate the different influencing parameters in injection molding processing on the properties of short carbon and glass fiber-reinforced polypropylene. We investigated parameters like melt temperature and back pressure, but also machine size and pre-heating regarding their influence on the tensile properties. We found that adjustments of melt temperature and back pressure only yield small improvements in the fiber length and the tensile properties, also depending on machine size, but a pre-heating step of the granules can significantly improve the properties.

Assessing Intra-Bundle Impregnation in Partially Impregnated Glass Fiber-Reinforced Polypropylene Composites Using a 2D Extended-Field and Multimodal Imaging Approach.

This study evaluates multimodal imaging for characterizing microstructures in partially impregnated thermoplastic matrix composites made of woven glass fiber and polypropylene. The research quantifies the impregnation degree of fiber bundles within composite plates manufactured through a simplified compression resin transfer molding process. For comparison, a reference plate was produced using compression molding of film stacks. An original surface polishing procedure was introduced to minimize surface defects while polishing partially impregnated samples. Extended-field 2D imaging techniques, including polarized light, fluorescence, and scanning electron microscopies, were used to generate images of the same microstructure at fiber-scale resolutions throughout the plate. Post-processing workflows at the macro-scale involved stitching, rigid registration, and pixel classification of FM and SEM images. Meso-scale workflows focused on 0°-oriented fiber bundles extracted from extended-field images to conduct quantitative analyses of glass fiber and porosity area fractions. A one-way ANOVA analysis confirmed the reliability of the statistical data within the 95% confidence interval. Porosity quantification based on the conducted multimodal approach indicated the sensitivity of the impregnation degree according to the layer distance from the pool of melted polypropylene in the context of simplified-CRTM. The findings underscore the potential of multimodal imaging for quantitative analysis in composite material production.

Mechanical, Dielectric and Flame-Retardant Properties of GF/PP Modified with Different Flame Retardants.

With the rapid development of electronic information technology, higher requirements have been put forward for the dielectric properties and load-bearing capacity of materials. In continuous glass fiber-reinforced thermoplastic composites, polypropylene matrix is a non-polar polymer with a very low dielectric constant and dielectric loss, but polypropylene is extremely flammable which greatly limits its application. Aiming at the better application of flame retardant-modified continuous glass fiber-reinforced polypropylene composites (FR/GF/PP) in the field of electronic communication, the effects of four different kinds of flame retardants (Decabromodiphenyl ethane (DBDPE), halogen-free one-component flame retardant (MONO), halogen-free compound flame retardant (MULTI), and intumescent flame retardant (IFR)) on the properties of FR/GF/PP were compared, including the mechanical properties, dielectric properties and flame-retardant properties. The results showed that among the FR/GF/PP, IFR has the highest performance in mechanical properties, MULTI has better performance in LOI, DBDPE and IFR have better performance in flame retardant rating, and DBDPE and IFR have lower dielectric properties. Finally, gray relational analysis is applied to propose an approach for selecting the optimal combination (flame retardant type and flame-retardant content) of comprehensive performance. In the application exemplified in this paper, the performance of IFR-3-modified GF/PP is optimized.

Design of novel glass fiber reinforced polypropylene cable-anchor component and its long-term properties exposed in alkaline solution

The high performance and long life of engineering structures can be realized through replacing traditional steel materials with glass fiber reinforced polypropylene composites with high toughness/durability, flexibility design and recycling. In addition, the anchorage problem of composites needs to be solved by developing new anchorage technologies or forms. In the present paper, a new type cable-anchor component was developed to prolong the service life and realize the reliable anchoring of composite. The influence mechanism of arc angle (10°, 20°, and 30°) on the mechanical properties of cable-anchor component was evaluated through the experimental and mechanical simulation. The durability evolution of cable-anchor component exposed to alkali solution environment was investigated through macro-performance test and microstructure analysis. The results showed the tensile strength retention of cable-anchor component was up to 88.7 % at the arc angles of 10° under the circumferential constraint of carbon fiber. Larger arc angle increased the stress concentration and fiber misalignment of transition area between arc and straight segments, leading to the formation and propagation of defects or cracks in transition areas and early fracture failure. The saturated water absorption and diffusion coefficient of glass fiber reinforced polypropylene composites were obtained to be 0.78 % and 4.41×10−14 m2/s, respectively. Compared with nylon 6 and epoxy resin, polypropylene has excellent hydrophobic properties with the diffusion coefficient ratio of 0.0077 and 0.024. At the longest immersion, the tensile strength retentions of cable-anchor component were 61.8 % and the failure mode changed from component longitudinal splitting to brittleness fracture of arc region. The degradation mechanism was attributed to the initial defects of arc section formed and expanded under the complex stress and corrosive medium, which further aggravated the fiber/resin interfacial debonding. Through comparing with other glass fiber reinforced thermoplastic and thermosetting composites, the cable-anchor component has higher tensile strength retention after the immersion of alkaline solution owing to excellent hydrophobicity behavior of polypropylene and efficient preparation process.

Performance analysis of fiber-reinforced polypropylene composite laminates under quasi-static and super-sonic shock loading conditions for impact application

In the present research, glass and basalt fiber-reinforced polypropylene composites’ behaviour in quasi-static and dynamic conditions is studied. Composites were fabricated by vacuum assisted Compression molding method. Composites failure under quasi-static tension and compressive conditions was studied along with its failure behaviour under low-velocity impact and super-sonic shock loading under dynamic conditions. The study results showed that basalt fiber-reinforced polypropylene (Basalt/PP) composite’s tensile and compressive strength is higher than glass fiber-reinforced polypropylene (Glass/PP). The Basalt/PP showed no penetration against low velocity impact (LVI) with negligible deformations till 50 J. However, the Glass/PP perforated at 50 J with various failure patterns occurring at back side. The fiber-matrix interface adhesion plays an important role in super-sonic shock loading by absorbing shock wave energy due to ductile nature of polypropylene and the two composites absorbed energy via matrix and fibers failure, no brittle failure of laminates occurred under shock loading.

Numerical simulation analysis of forming of continuous fiber reinforced polypropylene composites: Relaxation, creep, and hot stamping

In this study, the viscoelastic constitutive equation of continuous glass fiber reinforced polypropylene composites based on the generalized Maxwell model and SCFM model was constructed by combining genetic algorithm. Based on this, a multi-scale numerical model for describing material relaxation and creep is proposed, and the accuracy of different scale models was compared through experiments. The forming state of the workpiece under various stamping speeds and preheating temperatures was also examined using a hot stamping numerical model. The independent design of the hot stamping hemispherical mold was used to confirm the hot stamping model's accuracy. The study's findings demonstrate that the macroscopic model can accurately simulate the relaxation and creep of composite materials. The hot stamping simulation results are match up well with experimental results. Composite molding defects appeared at the waist of the part, and defects were accompanied by resin loss.

Non-isothermal crystallization kinetics of halloysite nanotube/short glass fibre-reinforced polypropylene composites

Non-isothermal crystallization kinetics of halloysite nanotube/short glass fibre-reinforced polypropylene composites

Material and mechanical characterization of recycled polypropylene reinforced with different weight percentages of short glass fiber developed by injection molding

The objective of this study was to develop short glass fiber-reinforced recycled polypropylene composites using injection molding technique with varying fiber percentages (0–50 wt%). The study aimed to evaluate the mechanical and material properties of the composites and their potential applications. To achieve this, polypropylene composite pellets were prepared using a low-cost and simple manufacturing method that involved plastic recycling using a crushing method and pelletizing with different weight percentages of short glass fiber using twin-screw extruder. The study conducted various analyses, such as melt flow index, capillary rhinometry, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Results showed that the recycled polypropylene/short glass fiber composites exhibited improved heat resistance, crystallization rate, and thermal stability compared to the pure polymer. The best impact mechanical (about 3.65 ± 0.09 J/m) properties were obtained at 50 wt% of short glass fiber in the fabricated composites. Scanning electron microscope analysis indicated a uniform dispersion of short glass fiber in the polypropylene matrix. The potential applications of these composites were found in household appliances, industrial plastic products, and other areas. Overall, this study demonstrates the potential of short glass fiber-reinforced polypropylene composites as a cost-effective, environmentally friendly and sustainable alternative for various applications.

Effect of Strain Rate and Temperature on the Tensile Properties of Long Glass Fiber-Reinforced Polypropylene Composites.

Strain rate and temperature are influential factors that significantly impact the mechanical properties of long glass fiber-reinforced polypropylene composites. This study aims to investigate the tensile properties of these composites, analyzing the effects of temperature, strain rate, and their interplay on variables such as tensile stress, tensile strength, fracture stress, and fracture morphology through a series of comprehensive tensile experiments. The experimental results demonstrate a notable increase in both tensile strength and tensile fracture stress when the temperature is set at 25 °C, accompanied by strain rates of 10-4, 10-3, 10-2, and 10-1 s-1. Conversely, a significant decrease is observed in the aforementioned properties when the strain rate is fixed at 10-4, while varying temperatures of -25 °C, 0 °C, 25 °C, 50 °C, and 75 °C are applied. At lower temperatures, cracks manifest on the fracture surface, while matrix softening occurs at higher temperatures. Additionally, in the context of strain rate-temperature coupling, the decreasing trend of both tensile strength and tensile fracture stress decelerates as the temperature ranges from -25 °C to 75 °C at a strain rate of 10-1, compared to 10-4 s-1. These findings highlight the significant influence of both strain rate and temperature on high fiber content long glass fiber-reinforced polypropylene composites.

Thermo-visco mechanical behavior of glass fiber reinforced thermoplastic composite

Thermoplastic composite materials are being increasingly used in many domains, such as automotive, marine and aeronautics. This growing interest is due to the relatively good mechanical properties and the recycle-ability of these materials. In various heat assisted forming technologies, thermoplastic composites may be subjected to severe conditions such as high temperatures, complex strain paths and potentially significant strain rates. This is expected to highly influence the overall behavior of these materials and make the characterization of their mechanical behavior more complicated. In this paper, the mechanical behavior of discontinuous glass fiber reinforced polypropylene composite is investigated at temperatures going from room temperature (RT) to 120°C and strain rates ranging from quasi-static conditions to 10 s−1 by means of uniaxial tensile tests. The effect of material orientation is also investigated at RT and quasi-static strain rate of 0.001 s−1 pointing out a clear anisotropic behavior. The tensile properties including Young’s modulus E, ultimate tensile strength σ ult and strain at failure ɛ f are determined based on the Standard ISO-527 reporting an obvious sensitivity of the material to temperature and strain rate. Based on literature review, the phenomenological isotropic constitutive model of G’Sell and Jonas, originally designed for unreinforced semi-crystalline polymers, is selected to describe the mechanical behavior of the studied material. A modification of the original constitutive equation is proposed for a better representation of the overall behavior of the material at different temperature and strain rate conditions. Finally, the validity of this phenomenological law calibrated by means of the uniaxial tests, is evaluated for an equi-biaxial loading state close to that encountered by the material during heat assisted sheet forming process. The significant disagreement highlighted between numerical and experimental results proved that the uniaxial tensile tests are not sufficient to characterize the behavior of the material when a complex loading condition is imposed.

Experimental study on mechanical properties of material extrusion additive manufactured parts from recycled glass fibre-reinforced polypropylene composite

This paper presents an optimised material extrusion (MEX) 3D printing method with feedstock produced from glass fibre reinforced polypropylene (GFRPP) composite waste and investigates the effect of glass fibre weight fraction (0%, 15%, 30%, 40%) on the printability and mechanical properties of filaments and printed specimens. GFRPP feedstock filaments were fabricated by optimising the filament extrusion process parameters. The highest ultimate tensile strength (112 MPa) was obtained in a filament with 40% fibre weight content. In addition, repeated recycling of filament was shown to reduce the fibre aspect ratio and enhance the filament quality. It was shown that the increase in glass fibre content from 0% to 40% improved the ultimate tensile strength of MEX 3D printed specimens from 14.7 MPa to 23.4 MPa as well as the flexural strength of MEX 3D printed samples from 11.68 MPa to 66.55 MPa. The increase in fibre weight content from 30% to 40% had a minimal effect (+1%) on the ultimate tensile strength of the printed samples. In addition, the 40% filaments exhibited a more brittle behaviour, rendering them less suitable for MEX 3D printing than 30% GFRPP. The results showed that waste industrial GFRPP material can be effectively enhanced and converted to short fibre reinforced material extrusion filament feedstock for the printing of components as a circular economy demonstrator.

Recycling effects on the bending, rheological, and structural properties of glass fiber-reinforced isotactic polypropylene composites

In the present work, a combination of virgin polypropylene and E-glass fiber was subjected to ten (10) reprocessing cycles via extrusion and compression molding techniques to mimic recycling and its impacts on the bending properties of the composites. The samples were characterized using Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), scanning electron microscopy (SEM), and melt flow index (MFI). The results revealed a gradual depreciation in flexural properties after each reprocessing cycle. The XRD analysis indicated a substantial reduction of peak intensities, degrees of crystallinities, and average crystallite sizes, explaining the lowered flexural properties in addition to a possible reduction in glass fiber lengths (fiber attrition). Melt-processing behavior shows a progressive increase of MFI from 7 to 19.16 g/10 min, confirming the probable damage in molecular weight and loss of complex viscosity. Chemical and structural analysis showed no alteration in the polypropylene major functional groups. It is concluded that the reductions in molecular weight and composites’ properties occurred due to chain scission from recycling effects; hence, glass fiber-reinforced polypropylene composites can be recycled only three (3) times unless it is refreshed by the addition of virgin parts to compensate for the lost property.

Study on Recycling of Waste Glass Fiber Reinforced Polypropylene Composites: Examination of Mechanical and Thermal Properties

This study presents the preparation of short glass fiber reinforced polypropylene (PP/FG) composites using with waste (post-consumer) polypropylene composite containing long glass fiber (PP/LFG) obtained from the recycling of battery covers of trucks. Waste PP/LFG composite parts were mechanically grinded before adding to PP/FG composites. An injection molding machine was used to produce the PP/FG composite test samples loading with recycled waste PP/LFG composite in the range of 1-20% by weight. Effects of recycled waste PP/LFG content on the mechanical, thermal, and morphological properties of the PP/FG composites were investigated. The following three different tests, at various waste PP/LFG ratios, were conducted: Izod/Charpy Impact test, bending test, and tensile test. Mechanical test results showed that mechanical strength of prepared PP/FG composites were not influenced by content of waste PP/LFG material up to 10 wt.%. Differential scanning calorimetry (DSC) was used for the evaluation of thermal parameters such as melting point and crystallization temperature of the polymer matrix in the composites studied. Furthermore, by analyzing the values of thermal effects determined using the DSC method, it was possible to determine the degree of crystallinity. The DSC results showed that crystallinity %, melting, and crystallization temperatures of PP/FG composites were not influenced to adding waste PP/LFG at different ratios. The morphology of composite materials was investigated by SEM analysis. Good fiber dispersion was observed in the PP matrix for PP/FG composites containing short glass fiber prepared with all ratios of recycled waste PP/LFG material containing long glass fiber.

Physico-chemical properties of compression molded glass fiber reinforced polypropylene polymer composites

This article reports the material properties of short random discontinuous oriented glass fiber reinforced polypropylene composite is studied. The composite was prepared using compression molding process. The mechanical, structural, and thermal properties were observed by using universal testing machine, FTIR, XRD and DSC. The FTIR confirms the interaction between polypropylene and glass fibers. Semicrystalline nature is confirmed by XRD. The influence of temperature on viscosity and relaxation times in a material were analyzed using WLF and VTF equations. Mechanical stability is evaluated using stress -strain plots.

Fiber reinforced polypropylene composites interfacial behavior improvement fabricated by cold plasma jet SiOx nanoparticles deposition

In this study, cold atmospheric pressure plasma jet was adopted to glass fibers surface modification with tetraethyl orthosilicate as a precursor. To enhance the interfacial bonding forces of glass fiber reinforced polypropylene (GFRP) composites, SiOx nanoparticles were polymerized on the fiber surfaces. The effect of two factors (the distance between nozzle and fiber (D) and the treatment time (T)) on the interfacial bonding behavior of GFRP composites was studied. The modified fibers and composites properties, including surface topography, chemical composition, wettability and interfacial mechanical properties, were studied comprehensively. The optimal parameters were obtained at D = 17 mm and T = 12 s. Our results indicated that the interlaminar shear strength of GFRP composites was increased by 30.79% compared to control group. Further studies found that plasma treatment introduced larger surface roughness, surface energy and more oxygen-containing functional groups, which was responsible for the interlaminar shear strength improvement.

In-plane shear and tensile behavior of two-pass injection-molded glass fiber reinforced polypropylene composites with different fiber lengths

Glass fiber reinforced polypropylene (GF-PP) composites have proven a great potential in the designation and manufacturing of control arms, leaf springs, barriers, beams and bridge decks. Two-pass injection molding of GF-PP was investigated in this study. Polypropylene (PP) was injected with different weight fractions (w%) of chopped glass fibers (GFs) with different fiber feedstock lengths (FFSLs). The composites were then crushed and re-injected once again. Some specimens were burned out to check the actual weight fractions and fiber lengths after the injection processes. The fiber lengths dramatically decreased due to damages during two-pass injection processes and crushing. The manufactured specimens were tested in tension, and the results indicated that the tensile strength increased slightly at w = 10% of GF. Further increase of GF weight fraction leads to a drop in the tensile strength below neat PP. The results of SEM micrographs showed an increase in air voids concentrations at high GF percentages which clarifies the reason behind the drop in the tensile strength. Also, in-plane shear tests were carried out using the Iosipescu fixture where a slight increase in the in-plane shear strength was noticed by increasing fiber weight fractions. In-plane shear moduli of all specimens were measured experimentally by strain gauges and calculated theoretically. The shear modulus was enhanced by glass fiber addition and a further increase was noticed by increasing the fiber weight fractions.

Design and analysis of extrusion-compression molding setup for processing of glass fiber reinforced polypropylene composites

The processing techniques play a vital role in the development of short fiber reinforced thermoplastic composites. The extrusion technique is used for the compounding of short fiber and polymer before compression molding, as short fibers tend to entangle with each other and cause fiber agglomeration. In this paper, a new extruder nozzle design is firstly proposed for the extrusion compounding process for short glass fiber reinforced polypropylene, which can be utilized to direct the compounded composite flow towards a heated mold and then processed in compression molding. For compression molding of composite, temperature uniformity across mold plays a vital role in achieving uniform properties of the processed composite. A simulation study is done to investigate the effects of cartridge heater dimensions on temperature uniformity across mold, for its potential use as a heating element. The results show different cartridge dimensions produce different temperature profiles across the defined points in the cavity. Dimensional uniformity in the extruded strands can be achieved through the new nozzle design. The proposed nozzle and mold heat setup can be used for the extrusion-compression molding technique for the development of short glass fiber reinforced polypropylene composite.

Improving antistatic and mechanical properties of glass fiber reinforced polypropylene composites through polar adsorption and anchoring effect of organic salt

Matrix toughness and viscosity, fiber length, interface bonding, and crystalline structure play significant roles in tuning the antistatic and mechanical properties of polypropylene (PP) composites. However, there is no report available concerning the development of antistatic PP composites by considering all these factors. In this study, we fabricate antistatic long glass fiber reinforced polypropylene random copolymer composites filled with Li-TFSI (LGF/PPR/Li-TFSI) and explore how crystallization behavior due to Li-TFSI affects the interfacial strength and conductive mechanism. It is found that the polar effect promotes the adsorption of Li-TFSI on the surface of LGF to form a conductive track, and consequently, the three-dimensional conductive network formed by intertwined LGF effectively reduces the percolation threshold (i.e., 0.15 wt/wt%). Besides, the heterogeneous nucleation induced by Li-TFSI promotes the nucleation and crystal growth of PPR molecular chains on the surface of Li-TFS. Thus, Li-TFSI wrapped by spherulites improves the anchoring effect of the LGF on the PPR matrix. However, the anchorage degree is related to the close proximity of conductive particles, specifically, 0.05 wt/wt% Li-TFSI results in the highest level of stress transfer. Meanwhile, although the addition of 0.15 wt/wt% Li-TFSI causes a slight decrease in the interface strength, it leads to competitive nucleation between Li-TFSI and LGF, thereby generating thicker lamellae, which makes LGF/PPR/Li-TFSI the largest modulus. This study provides some new insights into the tailoring of material properties using Li-TFSI for antistatic PP composites.

Development of the temperature-dependent constitutive model of glass fiber reinforced polypropylene composites

ABSTRACT Plain-woven glass fiber-reinforced polypropylene (PW-GFRPP), as the typical advanced CoFRTP, has been rapidly emerged in aerospace, civil and automobile fields, thanks to its low cost and excellent performances. The fiber yarns of PW-GFRPP will undergo large rotations and shear deformations with immersions of molten polypropylene resin during the hot mold pressing process. The shear deformations of fiber yarns not only directly affect the formability quality of the preformed structures but also make an impact on the mechanical performances of cured products. Thus, the scope of this study is to construct the temperature-dependent material constitutive model of PW-GFRPP and investigate the influences of temperature and blank holding force (BHF) on the formability of PW-GFRPP prepregs. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) tests were first implemented to determine the melting and degradation temperatures of polypropylene. Next, the bias-extension tests for PW-GFRPP prepregs were carried out accounting for three temperature values (190°C, 220°C and 250°C). Then the temperature-dependent constitutive model was developed and validated. Finally, the validated constitutive model was used to explore the influences of temperature and blank holding force on the formability of PW-GFRPP composites on a double dome benchmark.

Synthesis of a self-assembly amphiphilic sizing agent by RAFT polymerization for improving the interfacial compatibility of short glass fiber-reinforced polypropylene composites

This experimental study focuses on the development of an amphiphilic sizing agent to improve the interfacial adhesion and the mechanical properties of short glass fiber (GF)/polypropylene (PP) composites. To solve the critical compatible issue between the hydrophilic GF and the hydrophobic PP, we strategically utilized the reversible addition-fragmentation chain-transfer (RAFT) polymerization to self-assemble and synthesize an amphiphilic sizing agent. This surfactant-free sizing agent can create hydrogen bonds and electrostatic adsorption on GF surfaces and meanwhile can form molecular entanglements, alkyl cations, and σ-π conjugates with PP matrix. The FT-IR analysis shows that a large number of hydrogen bonds are formed on the sizing agent-GF interface. Additionally, the SEM micrographs of the composite fracture surfaces demonstrate strong interfacial compatibility between the sized-GF and the PP matrix. Comparing with the neat GF/PP composites, the tensile and flexural strength of the sized-GF/PP composites are increased by 25.8% and 33.1%, respectively. Their tensile strength and young's modulus are in close agreement to the analytical calculations. In short, this paper presents a new RAFT-based methodology to develop the amphiphilic sizing agents that are able to improve the interfacial compatibility of GF/PP composites and also can be transferred towards real applications for enhancing the mechanical properties of fiber-reinforced composites.