Mechanical Properties Of Polypropylene Research Articles

The Influence of Glass Fiber/Glass Fiber Powder with β-Nucleating Agent on the Properties of Polypropylene

Glass fiber-reinforced polypropylene (PP/GF) has been widely used due to its high stiffness, but for some applications that need low-module characteristics, PP/GF will have limitations due to its lower toughness, so it is necessary to develop glass fiber-modified polypropylene with good stiffness–toughness balance performance. In this study, two average length glass fibers (4.5 mm and 12 mm) and glass fiber powder, combined with β-nucleating agent, were used to investigate the effects on the crystallization and mechanical properties of polypropylene. The results show that compared with glass fiber, glass fiber powder cooperates with β-nucleating agent reinforced polypropylene composite showed good stiffness–toughness balance performance, and β-crystals were found in the composite measured by Differential Scanning Calorimetry (DSC), the presence of β-crystals can improve the toughness of the composite.

The Effect of Wastes of Nettle Fiber on Mechanical and Thermal Properties of Polypropylene Composite

ABSTRACT In this study, ground wastes of Nettle (Urtica dioica L.) fiber (GWN), which contains cellulose of 52.2 wt%, hemicellulose of 28.9 wt%, and lignin of 18.9 wt%, filled polypropylene (PP) composites were fabricated by using a high-speed kinetic mixer. The effect of filling GWN into PP at different weight fractions on density, crystallization behavior, coefficient of thermal expansion, and thermal stability was investigated. In addition, tensile and flexural tests were performed to determine how the mechanical properties of PP were affected. Morphological observations were conducted using scanning electron microscopy (SEM). The flexural strength values of PP increased by 10%, 15%, and 31% with the addition of 7 wt%, 14 wt%, and 21 wt% GWN, respectively. However tensile strength value of PP decreased slightly with the addition of GWN. 21 wt% GWN addition into PP led to a considerable decrease (about 29%) in the thermal expansion coefficient of PP. The degree of crystallinity of PP was not affected by the addition of GWN.

Towards a Circular Economy: Study of the Mechanical, Thermal, and Electrical Properties of Recycled Polypropylene and Their Composite Materials.

This research focuses on the mechanical properties of polypropylene (PP) blended with recycled PP (rPP) at various concentrations. The rPP can be added at up to 40 wt% into the PP matrix without significantly affecting the mechanical properties. MFI of blended PP increased with increasing rPP content. Modulus and tensile strength of PP slightly decreased with increased rPP content, while the elongation at break increased to up to 30.68% with a 40 wt% increase in rPP content. This is probably caused by the interfacial adhesion of PP and rPP during the blending process. The electrical conductivity of materials was improved by adding carbon black into the rPP matrices. It has a significant effect on the mechanical and electrical properties of the composites. Stress-strain curves of composites changed from ductile to brittle behaviors. This could be caused by the poor interfacial interaction between rPP and carbon black. FTIR spectra indicate that carbon black did not have any chemical reactions with the PP chains. The obtained composites exhibited good performance in the electrical properties tested. Finally, DSC results showed that rPP and carbon black could act as nucleating agents and thus increase the degree of crystallinity of PP.

Comprehensive Comparisons of Grafting-Modified Different Polypropylene as HVDC Cable Insulation Material

Polypropylene (PP) is considered to be a rather potential material for recyclable HVDC cable insulation. Grafting modification has been proven to be effective to further enhance the dielectric properties of PP. To investigate the grafting effect on the performance of different PPs, homopolymerized PP (PPH), ethylene-propylene copolymer (PEC), and impact PP copolymer (IPC) are, respectively, grafting-modified by styrene, and the comprehensive properties are experimentally studied. The results indicate that all these grafting-modified PPs show enhanced dielectric properties, while the enhancement levels differ. Styrene-grafted PPH presents the best dielectric properties improvement and highest thermostability, but the elastic modulus is also the highest. PEC exhibits moderate dielectric properties enhancement after grafting modification. Grafting-modified IPC shows excellent mechanical properties, but the enhancements on dielectric properties are rather limited. Grafting styrene has no significant influence on the thermal and mechanical properties of PP. In conclusion, PPH is preferred to be the matrix for styrene-grafting to achieve enhanced dielectric properties. However, the mechanical properties still need further modification to meet the demands of cable insulation.

Mechanical and thermal degradation properties of Isotactic Polypropylene Composites with Cloisite15A and Cloisite20A

This work studies the influence of maleic anhydride grafted polypropylene (PP-g-MA) content on thermal and mechanical properties of polypropylene (PP) composites with two types of clays, differing modifier density in the interlayer space, Cloisite15A and Cloisite20A. PP/clay composites are melt blended in presence of different content of PP-g-MA from 3, 6, 9, and 12 wt.%. It is found that Cloisite15A with a high density of the modifier promotes the formation of intercalated structures, while Cloisite20A with a low density of the modifier, predominantly exfoliated nanocomposites are formed. In the first case, the structure tends to become intercalated whilst composites with Cloisite20A favor the formation of predominantly exfoliated structures. The formation of the nanocomposite is accompanied by a significant increase in thermal stability (50% weight loss is observed at temperatures of 360°C and 430°C for polypropylene and nanocomposites based on it, respectively). An analysis of the mechanical properties of nanocomposites generally indicates an increase in the elastic modulus by 15-20%, and this effect is more pronounced for exfoliated structures, the yield strength practically does not change and the elongation at break decreases noticeably.

Synergistic Effects of DOPO-Based Derivative and Organo-Montmorillonite on Flame Retardancy, Thermal Stability and Mechanical Properties of Polypropylene.

Polypropylene (PP), as a general thermoplastic polymer, is broadly used in different fields. However, the high flammability, melt dripping and poor mechanical properties of PP are a constraint to the expansion of its applications. In this paper, PP composites containing a combination of a phenethyl-bridged DOPO derivative (PN-DOPO) and organic montmorillonite (OMMT) were prepared via melt blending. The synergistic effects of PN-DOPO and OMMT on the flame retardancy, thermal stability and mechanical properties of PP composites were investigated systematically. The results showed that 20 wt% addition of PN-DOPO with OMMT improved the flame retardancy of PP composites. In particular, the introduction of 17 wt% PN-DOPO and 3 wt% OMMT increased the LOI values of the PP matrix from 17.2% to 23.6%, and the sample reached the V-0 level and reduced the heat release rate and total heat release. TGA indicated that OMMT could improve the thermal stability of the PP/PN-DOPO blends and promote the char residues of PP systems. Rheological behaviour showed a higher storage modulus, loss modulus and complex viscosity of PP/PN-DOPO/OMMT composites, suggesting a more effective network structure. In addition, the tensile strength, flexural properties and impact strength of the PP/PN-DOPO/OMMT composites actually increased for a good dispersion effect. Combined with the char layer analysis, the introduction of OMMT promoted more continuous and compact structural layers containing an aluminium–silicon barrier and phosphorus-containing carbonaceous char in the condensed phase. OMMT can improve the flame retardancy, thermal stability and mechanical properties of PP, and, thus, PN-DOPO/OMMT blends can serve as an efficient synergistic system for flame-retarded PP composites.

Preparation of Exfoliated Organo‐Montmorillonite and Its Effect on Flame Retardancy and Mechanical Properties of Polypropylene

AbstractIn this study, a new type of ammonium polyphosphate‐intercalated organic montmorillonite (APP/OMt) was synthesized using in‐situ polymerization, and the chemical structure and surface morphology of APP/OMt was confirmed by FT‐IR, XRD, EDS and SEM. Moreover, the intumescent flame retardant (IFR) composed of APP/OMt, pentaerythritol (PER) and melamine (MA) was added into polypropylene (PP) to fabricate the PP/IFRAPP/OMt composites, and their flame‐retardant and mechanical properties were characterized systematically. When the additive mass of the flame retardants was 30 %, the limiting oxygen index (LOI) value reached 33.3 %, and the UL‐94 test passed the V‐0 level when the added amount was only 20 %. Especially, compared to the counterpart of IFRAPP, the addition of IFRAPP/OMt dramatically decreased the released smoke of PP during combustion, and the quality of carbon layer after combustion was obviously improved. The flame‐retardant mechanism of IFRAPP/OMt was deeply explored. In addition, the mechanical properties of PP composites with IFRAPP/OMt were significantly improved compared with IFRAPP. The enhanced flame retardancy and mechanical strength were attributed to the synergistic effect between OMt and IFR particles along with improved the dispersion of IFRAPP/OMt within the PP matrix.

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.

Mechanical and Thermal Degradation Properties of Isotactic Polypropylene Composites with Cloisite15A and Cloisite20A

In this work, the influence of maleic anhydride grafted polypropylene (PP-g-MA) content on thermal and me-chanical properties of polypropylene (PP) composites with two types of clays, differing modifier density in the interlayer space, Cloisite15A and Cloisite20A, was studied. PP/clay composites were melt blended in presence of different content of PP-g-MA from 3, 6, 9, and 12 wt.%. It was found that Cloisite15A with a high density of the modifier promotes the formation of intercalated structures, while Cloisite20A with a low density of the modifier, predominantly exfoliated nanocomposites are formed. In the first case, the structure tends to become intercalated whilst composites with Cloisite20A favor the formation of predominantly exfo-liated structures. The formation of the nanocomposite is accompanied by a significant increase in thermal sta-bility (50 % weight loss is observed at temperatures of 360 °C and 430 °C for polypropylene and nanocomposites based on it, respectively). An analysis of the mechanical properties of nanocomposites gen-erally indicates an increase in the elastic modulus by 15–20 %, and this effect is more pronounced for exfoli-ated structures, the yield strength practically does not change and the elongation at break decreases noticeably.

Machine Learning and Structural Design to Optimize the Flame Retardancy of Polymer Nanocomposites with Graphene Oxide Hydrogen Bonded Zinc Hydroxystannate.

Designing flame-retardant polymers with high performance is a long-standing challenge, partly because of the time-consuming traditional approaches based on experiential intuition and trial-and-error screenings. Inspired by the effective new paradigm of data-driven material discovery, we used machine learning to analyze experimental data to accelerate the development of new flame-retardant polymers. To explore the relationship between limit oxygen index (LOI) and components, we prepared 20 composites and then trained a simple equation for the LOI using the method sure independence screening and sparsifying operator (SISSO). The data analysis allows us for a better understanding of the flame-retardant mechanism and components, and the equation has good accuracy in guiding the design of composites with high flame-retardant performance. Meanwhile, the increasing structural design of flame retardants is crucial to flame-retardant polymer composites. We proposed a structure of nano graphene oxide (GO) wrapped micro zinc hydroxystannate (ZHS) in a simple but effective way as a novel flame-retardant agent to enhance the flame retardancy and mechanical properties of polypropylene (PP) composites. The GO sheets were like "light yarns" wrapped onto the ZHS via hydrogen bonding in an ethanol solution. The selected samples were analyzed to confirm the predictive LOI model. The resultant composites with the substitution of intumescent flame retardant (IFR) by 1.0, 2.0, and 4.0 wt % ZHS@GO conferred better flame retardancy compared with PP composite containing only IFR, reflected by the efficient increase of LOI value and V0 rating of UL-94 vertical tests. The analysis principles and facile fabrication strategies proposed in this work could be important for developing highly flame retardant composites.

Influence of the Crystalline Structure of Components and the Boundary Layer between Them on Mechanical Properties of Polypropylene–High Density Polyethylene Composites

Influence of the Crystalline Structure of Components and the Boundary Layer between Them on Mechanical Properties of Polypropylene–High Density Polyethylene Composites

Properties of Wood-Plastic Composites Manufactured from Two Different Wood Feedstocks: Wood Flour and Wood Pellets.

Driven by the motive of minimizing the transportation costs of raw materials to manufacture wood–plastic composites (WPCs), Part I and the current Part II of this paper series explore the utilization of an alternative wood feedstock, i.e., pellets. Part I of this study reported on the characteristics of wood flour and wood pellets manufactured from secondary processing mill residues. Part II reports on the physical and mechanical properties of polypropylene (PP)-based WPCs made using the two different wood feedstocks, i.e., wood flour and wood pellets. WPCs were made from 40-mesh wood flour and wood pellets from four different wood species (white cedar, white pine, spruce-fir and red maple) in the presence and absence of the coupling agent maleic anhydride polypropylene (MAPP). With MAPP, the weight percentage of wood filler was 20%, PP 78%, MAPP 2% and without MAPP, formulation by weight percentage of wood filler was 20% and PP 80%. Fluorescent images showed wood particles’ distribution in the PP polymer matrix was similar for both wood flour and ground wood pellets. Dispersion of particles was higher with ground wood pellets in the PP matrix. On average, the density of composite products from wood pellets was higher, tensile strength, tensile modulus and impact strength were lower than the composites made from wood flour. Flexural properties of the control composites made with pellets were higher and with MAPP were lower than the composites made from wood flour. However, the overall mechanical property differences were low (0.5–10%) depending on the particular WPC formulations. Statistical analysis also showed there was no significant differences in the material property values of the composites made from wood flour and wood pellets. In some situations, WPC properties were better using wood pellets rather than using wood flour. We expect if the material properties of WPCs from wood flour versus wood pellets are similar and with a greater reduction in transportation costs for wood pellet feedstocks, this would be beneficial to WPC manufacturers and consumers.

Effect of Filler Morphology on the Electrical and Thermal Conductivity of PP/Carbon-Based Nanocomposites

In this paper, we studied the effect of different carbon-based nanostructures on the electrical and mechanical properties of polypropylene (PP) nanocomposites. Multi-walled carbon nanotubes (MWCNT), expanded graphite (EG), and two different carbon black nanoparticles (CB) have been dispersed at several weight contents in the polymer matrix through a melt extrusion process. The produced nanocomposites have been used to obtain samples for the characterization by injection molding. The dispersion of the nanoparticles in the matrix has been evaluated by scanning electron microscopy (SEM) analysis. The electrical characterization has been performed both in DC and in AC configuration. The mechanical properties have been evaluated with both tensile test and impact strength (Izod). The thermal conductivity has been also evaluated. As a result, MWCNTs are the nanoadditive with the lowest electrical percolation threshold. This allows MWCNT nanocomposite to drastically change the electrical behavior without a significant embrittlement observed with the other nanoadditives. However, CB with the lowest surface area allows the highest conductivity, even though at a high particle content. EG has a limited effect on electrical properties, but it is the only one with a significant effect on thermal conductivity.

Long-Lived T-Shaped Micropillars with Submicron-Villi on PP/POE Surfaces with Grinding-Enhanced Water Repellency Fabricated via Hot Compression Molding.

Superhydrophobic properties are derived from the roughness of the surface of micro/nanostructures and low-surface-energy materials. However, they are both easy to damage on superhydrophobic surfaces after mechanical abrasion in practical applications, resulting in the transition from the Cassie-Baxter state to the Wenzel state and even the loss of water repellency. In this work, the mechanical properties of polypropylene (PP) toughened with poly(ethylene-co-octene) (POE) were improved for the fabrication of long-lived T-shaped micropillars with submicron-villi on top by a combined method of compression molding and grinding. A universal testing machine was modified as equipment for the precise control of the traveling distance of specimens on sandpaper in precise. The PP/POE blend possessed high tensile strength of up to ∼23.84 MPa as well as elongation at break of ∼533.60%. The abrasive grains on sandpaper reshaped their surface morphologies from micropillars to T-shaped microstructures, on which the submicron-villi as secondary structures formed. The abraded microstructured PP/POE surface exhibited the highest contact angle of 154.4° and the most stable wetting state with a bouncing height of 7.68 mm (3.2 times the diameter of the 7-μL droplet) after a traveling distance of 1000 mm on 3000-grit sandpaper among the abraded and unabraded PP/POE surfaces.

The effect of rubber powder additives on mechanical properties of polypropylene glass-fiber-reinforced composite

Abstract. Reinforced thermoplastic composites offer considerable advantages in structural and industrial applications in terms of high specific strength, excellent corrosion resistance, high impact toughness, high specific stiffness, recyclability, cost effectiveness, and design flexibility. Glass fibers (GFs) are the reinforcement material used in polypropylene (PP) composites to enhance PP properties with reasonable cost. To obtain better mechanical properties and decrease the overall cost, recycled rubber powder was used as a low-cost additive to PP/GF composites. The PP and GF, with different weight fractions, were mixed mechanically; then, the mixture was fed into injection molding machine. The PP/GF composites with the highest mechanical properties were selected for further improvements using rubber powder. The obtained samples were tested using tension, impact, and wear tests. The results show that tensile strength of PP/GF composite was improved by 17.8 % by adding 15 wt % GF, and there was a huge drop in impact strength by 80 % for the same GF weight fraction (15 wt %) compared to that of pure PP because of existence of GF. Wear properties and impact strength were improved by adding rubber powder to the composite, with a low weight fraction of 5 wt %, due to the shock-absorbing properties of rubber powder. Micrographs of the fractured sample surfaces revealed the good adhesion between the GF, PP, and the rubber particles.

Use of Nanoindentation to Mechanically Characterized Polypropylene/Cloisite 15A Nanocomposites Films Exposed to Gamma‐Irradiation

AbstractIn this paper, the effect of γ‐irradiation on the mechanical properties of polypropylene (PP)/Cloisite 15A (5 wt %) nanocomposites is investigated by nanoindentation technique up to 100 kGy. The film samples, with an average thickness of 150 μm, are prepared by melt compounding with and without PP‐grafted‐maleic anhydride (PP‐g‐MA) used as the compatibilizer at 20 wt %. Nanoindentation results show an increase in both modulus and hardness with the irradiation dose for the PP nanocomposites, being however much higher for the compatibilized sample compared to both uncompatibilized one and neat PP. FTIR spectra show a strong absorption band at 1715 cm−1 in the irradiated samples assigned to ketonic groups whose intensity increased with the dose. Further, the oxidation rate of PP nanocomposites is faster than that of neat PP. Overall, the nanoindentation results are in a good agreement with those obtained by FTIR spectroscopy.

Effect of Alkaline Treatment and Coupling Agent on Thermal and Mechanical Properties of Macadamia Nutshell Residues Based PP Composites

The influence of alkaline treatment on the thermal and mechanical properties of polypropylene (PP) reinforced with fibers from macadamia nutshell (5 to 30 wt%) was studied. To improve the interaction between fiber and matrix, the fibers were submitted to an alkaline treatment, as well as a coupling agent (MAPP) was used. The composites were obtained in a thermokinetic mixer, milled, and injected. Then, the degradation temperature and the loss of mass of the composites, pure PP, and fibers were evaluated. The mechanical properties of the composites were also evaluated. The results indicated that the degradation peak of composites occurred at higher temperatures, which indicated that composite exhibited higher thermal stability at higher temperatures. The addition of raw and treated macadamia fibers to the PP increased the stiffness of the composites, as well as the use of a coupling agent when compared to the neat PP. However, the incorporation of 30 wt% treated fiber to the PP showed an enhancement of 67.5% in the tensile modulus. The morphological analysis enabled to evaluate the efficiency of the coupling agent and the treated fibers adhered to matrix. The response surface methodology (RSM) technique showed that the higher fiber content added to the PP enhanced the stiffness, and consequently reduced the impact strength of the materials.

Green Composites Based on Polypropylene and Recycled Coffee Gunny: Morphology, Thermal and Mechanical Properties

In this study, coffee gunny which is made of jute fiber (Jf) hybrid woven cloth was used to reinforce polypropylene (PP). Maleic anhydride grafted polypropylene (MAPP) was added as a compatibilizer. Moreover, Jf was chemically treated by various methods to enhance the compatibility between fiber and the PP matrix. The results of Fourier transform infrared spectroscopy (FTIR), Polarized optical microscopy (POM), and Differential scanning calorimetry (DSC) showed that Jf is composed of jute yarn, PE fiber, and PP/PE hybrid fiber. Scanning electron microscopy (SEM) analysis showed that the compatibility between Jf and PP was improved by the chemical treatment of Jf. The results of tensile and impact tests showed that PP composite containing MAPP and the Jf after alkaline treatment (PP/MAPP/BJf) exhibited the best tensile and impact strengths. Its increments of tensile and impact strengths were 25% and 29% as compared to the untreated Jf-containing composite (PP/Jf). Apart from enhancing the mechanical properties of PP, the incorporation of coffee gunny can reduce the production cost of materials while meeting the demands of environmental protection agencies.

High‐efficiencyammonium polyphosphate intumescent encapsulated polypropylene flame retardant

AbstractThe flame retardant polypropylene containing the micro‐envelope core‐shell structure flame retardant, which encapsulated ammonium polyphosphate into melamine‐formaldehyde resin and sodium silicate through in situ polymerization was prepared with polyamide 6, added as a carbon‐forming agent. The composition of ammonium polyphosphate, encapsulated ammonium polyphosphate with melamine‐formaldehyde resin and the micro‐envelope core‐shell structure flame retardant were characterized. The fire safety and thermal stability were investigated and showed an improvement including limiting oxygen index, thermogravimetric analysis, vertical burning tests, and microscale combustion calorimeter. The burned compounds were also studied to confirm the burning mechanism. The results showed the flame retardant performance had been greatly improved, while polyamide 6 had better char‐forming effect. Besides, the water solubility of flame retardants and their influence on the mechanical properties of polypropylene were also investigated. The results on the effects of additives demonstrated a high efficiency flame retardant to polypropylene. A core‐shell flame retardant that sodium silicate and melamine‐formaldehyde resin‐coated ammonium polyphosphate had been constructed. The effect of the built flame retardant system on the combustion performance of polypropylene was studied from the mechanism and performance. The LOI of the most flame retardant polypropylene reached 28.6%, and UL‐94 reached the V‐0 level.

3D printed estradiol-eluting urogynecological mesh implants: Influence of material and mesh geometry on their mechanical properties.

Current treatment for pelvic organ prolapse (POP) and stress urinary incontinence (SUI) involves transvaginal implantation of surgical mesh, conventionally made of polypropylene (PP). However, it has recently become apparent that the mechanical properties of PP are unsuitable, resulting in serious complications such as tissue erosion. In this study, thermoplastic polyurethane (TPU) was chosen as an alternative material, and hormone-loaded meshes were produced by fused deposition modelling (FDM). Filaments containing various concentrations (0%, 0.25%, 1%) of 17-β-estradiol (E2) were prepared by hot-melt extrusion (HME) and were 3D printed into meshes with various geometries. The resulting meshes were characterised through a variety of instruments such as attenuated total reflection-Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermal analysis, fracture force and in vitro release studies. The results showed that E2 was homogeneously distributed throughout the TPU matrix. Moreover, the thermogravimetric analysis (TGA) showed degradation temperatures above those used during the FDM process, showing that the meshes can be produced below the degradation temperatures of the materials. The fracture force testing showed that material and mesh geometry influence mechanical properties, with TPU meshes appearing more elastic and therefore more suitable for pelvic floor repair than PP mesh. However, interestingly the mechanical properties of the TPU70 filament was not affected by the inclusion of E2. In addition, the 3D printed meshes showed a linear E2 release profile over a two weeks period, which can be modified according to the percentage of E2 added to the 3D printed construct. This proof of concept study demonstrates the potential of using FDM to create a new generation of safer mesh implants.