Mechanical Properties Of Polypropylene Research Articles

The effect of nanoclay filler addition on the foaming and mechanical properties of polypropylene

AbstractIn this study, onium‐ion‐added nanoclay (NC)/microcellular polypropylene (PP) composites were created using a conventional injection molding machine. A chemical foaming agent was utilized to facilitate mixing. The primary focus was to analyze how altering the NC content affects the mechanical characteristics and the properties of the endothermic chemical foaming agent added PP/NC composites. The composites were created using a chemical foaming agent at a weight ratio of 1 wt% and NC at weight ratios of 0 wt%, 2.5 wt% and 5 wt%. The findings indicated that an increase in the NC ratio led to higher cell count and cell density, along with a reduction in cell diameter. Additionally, the outcomes demonstrated that the foaming of PP/NC composites resulted in decreased modulus of elasticity and tensile strength while enhancing impact strength. © 2024 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

The effect of maleic anhydride grafted polypropylene addition on the degradation in the mechanical properties of the PP/wood composites

This work focuses on studying the influence of coupling agents on the degradation in the mechanical properties of Polypropylene (PP)/wood composites. Maleic anhydride polypropylene (MAPP) was used as a coupling agent between the wood flour and PP matrix. As the coupling agent plays an important role in the stability of the WPC, a 10 wt% wood flour was mixed with PP granules along with a UV stabilizer and varying percentages (1, 3, 5 wt%) of MAPP in a twin-screw extruder to obtain PWC granules. The composite granules were injection molded to produce tensile samples for the mechanical characterization of the composites. To test the environmental degradation of the PWCs, the tensile samples were exposed to the environmental conditions for 0, 336 h (14 days), and 672 h (28 days) prior to testing. After the specified exposure time, the samples were mechanically characterized using tensile testing. The degradation characteristics of the WPCs were quantified in terms of the failure strains of the composite with exposure time. The experiments were designed, and various analyses, including ANOVA, regression equation, and prediction tests, were carried out to investigate the impact of parameters on the failure strain of the PWCs. Moreover, the study aimed to examine the effect of parameters such as MAPP and time, on the failure strain of the composites. From the experimental results, it is concluded that the composites containing 1 wt% of MAPP showed superior retention in the degradation of composites when compared with 3 and 5 wt% MAPP content.

Effect of Ethylene-Propylene-Diene Monomer Blending on the Dielectric Properties of Polypropylene for Power Cable Insulation

Thermoplastic materials such as polypropylene (PP) are ideal candidates to be used as power cable insulation materials. However, the mechanical properties of PP, which is brittle and stiff, need to be modified to meet the requirements of power cable insulation applications. To overcome this, ethylene-propylene-diene monomer (EPDM) can be melt blended with PP to improve PP’s mechanical properties. In the current work, the effect of blending different contents of EPDM with PP was investigated in terms of the morphology, chemical structure, dielectric response, electrical, and mechanical properties. The results show that the EPDM blended well with the PP as the EPDM dispersed in the PP structure. Meanwhile, the chemical structure and dielectric response of the EPDM and PP blend became slightly different with high contents of EPDM, which subsequently affected the breakdown strength and mechanical properties. Nevertheless, it is worth noting that PP blended with low contents of EPDM has the potential to be used as recyclable power cable insulation materials.

The impact of post-radiation high-temperature shear grinding on the thermal and mechanical properties of polypropylene

The effect of input doses of 60Co γ-radiation from 80 to 12,000 kGy on the thermophysical properties and thermal stability of samples of polypropylene granules and powder obtained by high temperature shear grinding of irradiated granules, as well as on the tensile strength properties of a plate made from irradiated granules and their corresponding powders, was studied. The thermophysical properties of the powder are determined by the changes introduced by radiation into the initial polymer granules. The effects of radiation in air (environments with oxygen) were studied. Grinding redistributes oxygen-containing functional groups from the surface layer of irradiated granules throughout the entire volume of the obtained powder leading to the destruction of polymer chains as there is a component due to thermal destruction of radiolyzed polymer chains. High-temperature shear grinding of irradiated granules has a significant effect on the product powder, reducing its thermal stability but increasing the tensile strength of plates pressed from it at low absorbed doses. The current work shows that radiation treatment coupled with high temperature shear grinding could be a method for modifying the properties of polymers so that polypropylene waste can be processed for other applications.

Novel four-in-one intumescent flame retardants for polypropylene: Synthesis, characterization and properties

To address the shortcomings of traditional intumescent flame retardants (IFRs), a novel four-in-one IFR (M [APP/NiCo2O4]) was constructed for the first time. It integrates acid source, gas source, carbon source (crosslinking β-CD), and synergistic agent (NiCo2O4 nanoparticles) into a single entity by a co-encapsulation technology. Under the loading of 20 wt%, its flame retardant performance was significantly better than that of simple mixed flame retardants, and it could increase the limiting oxygen index of polypropylene (PP) from 18 to 30.2 and pass the UL-94 V-0 rating. At the same time, it could reduce the peak of heat release rate, total heat release, and peak of CO production of PP by 77%, 22%, and 80%, respectively, showing excellent flame retardant performance. The excellent flame retardant performance is mainly because the synergist NiCo2O4 nanoparticles in the four-in-one flame retardant can easily combine and efficiently interact with the acid source, carbon source, and gas source in the intumescent flame retardant to form a more stable protective char residue. In addition, the crosslinking β-CD shell enhances both the water resistance and initial thermal decomposition temperature of PP containing the four-in-one IFR compared to PP with simple mixed control samples. After 72 h of water resistance test, it can still maintain the UL-94 V-0 rating. The presence of the crosslinking β-CD shell also improves the compatibility of the four-in-one flame retardant in PP, and its adverse effects on the mechanical properties of PP are also significantly smaller than those of the mixed control sample.

Elongational flow‐induced microstructure evolutions in polypropylene/layered double hydroxides nanocomposites

AbstractIn this work, the effect of the non‐isothermal elongational flow on the morphology and mechanical properties of polypropylene (PP)‐based nanocomposites containing Mg‐Al layered double hydroxides (LDHs) modified with stearate or oleate functional groups has been investigated. In particular, nanocomposites containing 5 and 10 wt% of LDHs prepared through melt compounding were subjected to uniaxial elongational flow at the exit of the extruder, leading to the formation of fibers characterized by different draw ratios (DRs). The mechanical characterization of the fibers demonstrated a progressive enhancement of the tensile strength as a function of the DR with increasing the content of nanofillers. Notably, for the fibers stretched at a DR of 200 and containing 10 wt% of LDHs modified with oleate groups, the tensile strength increased fourfold as compared to that of the unfilled matrix. These results have been attributed to a progressive enhancement of the extent of the dispersions of the embedded LDHs induced by the application of the elongational flow, as also confirmed by morphological analyses. In all, the obtained results demonstrated the beneficial effect of the elongational flow in promoting the achievement of superior mechanical properties in LDHs‐containing nanocomposites, hence widening the application field of these nanostructured materials.Highlights PP/organomodified LDH nanocomposites were obtained through melt compounding. Nonisothermal elongational flow was applied to the extrudates at the die exit. Anisotropic fibers showed progressively enhanced tensile strength values. Elongational flow promoted a gradual evolution of the material microstructure. A gradual improvement of the nanofiller dispersion was observed upon elongation.

Dual functionalized copper nanoparticles for thermoplastics with improved processing and mechanical properties and superior antibacterial performance.

The utilization of metal nanoparticles for antibacterial thermoplastic composites has the potential to enhance the safety of human and animal life by mitigating the spread and transmission of foodborne pathogenic bacteria. The dispersion, antioxidant and antimicrobial activities of metal nanoparticles directly affect the application performance of the composites. This study focused on achieving amine-carboxyl co-modified copper nanoparticles (Cu-AC) with excellent antioxidant properties and monodispersity through in situ grafting of amine and carboxyl groups onto the surface of copper nanoparticles via ligand interaction. Polyacrylic acid's extended carbon chain structure was utilized to improve its dispersion and antioxidant properties, and its antibacterial properties were synergistically enhanced using secondary amines. It was found that Cu-AC possesses high antibacterial properties, with a minimum inhibition concentration of 0.156 mg mL-1. Antibacterial masterbatches and their composites (polypropylene/Cu) manufactured by melt blending of polypropylene and Cu-AC exhibited excellent antibacterial rates of up to 90% and 99% at 300 ppm and 700 ppm Cu-AC, respectively. Additionally, Cu-AC bolstered the thermal degradation, processing and mechanical properties of polypropylene. The successful implementation of this product substantiates the potential applications of polypropylene/Cu composite materials across diverse industries.

Preparation of high-performance anti-aging polypropylene by modified nano-TiO2 and calcium sulfate whisker grafted acrylonitrile composite PP.

By employing the radical polymerization method, acrylonitrile (AN) was grafted on the surface of nano titanium dioxide (TiO2), and the calcium sulfate whisker (CSW) was modified using the coupling agent KH570 to provide ultraviolet (UV)-absorption capacity. The prepared TiO2-PAN and CSW-PAN materials can improve the anti-aging performance and mechanical properties of polypropylene (PP) and meet the application requirements of high-performance polypropylene. Further, the obtained PP composites show prolonged service life and application scope, which can effectively reduce white waste and avoid both resource waste and environmental pollution.

Preparation of magnesium hydroxide by modifier-directed hydration and its effect on flame retardancy and mechanical properties of polypropylene

With the rapid development of the polymer materials industry and the improvement of people's environmental awareness, magnesium hydroxide has been widely used in polymer materials due to its high decomposition temperature, non-toxic smoke suppression, and the advantages of neutralizing harmful gases produced by polymer combustion. However, the conventional preparation methods of magnesium hydroxide exhibit several issues, including high hydrophilicity, elevated polarity, and limited compatibility with polymers. This research proposes an improved method by adding sodium stearate and KH560 modifier, controlling the rate of magnesium oxide and preparing magnesium hydroxide flame retardants using a modifier-directed hydration method. Various characterizations confirmed its morphology, particle size and structure. The magnesium hydroxide exhibits low polarity, small particle size, stable structure and excellent hydrophobicity (with a contact angle of 120.32°, and a free energy of 1.34mN/m). In parallel, the magnesium hydroxide/polypropylene composites demonstrate excellent flame retardancy (LOI of 25%, V-1 grade) and simultaneously enhance the dispersion of magnesium hydroxide within the polypropylene matrix, improving the material's toughness and strength.

Synthesis of Zinc Oxide Doped Magnesium Hydrate and Its Effect on the Flame Retardant and Mechanical Properties of Polypropylene.

In this work, an effective flame retardant consisting of nanoscale zinc oxide doped on the surface of hexagonal lamellar magnesium hydrate (ZO@MH) has been successfully synthesized via a hydrothermal process. Approximately 3-methacryloxypropyltrimethoxysilane (KH-570) is chosen as a modifier of ZO@MH for the purpose of enhancing the interfacial interaction between ZO@MH and the polypropylene (PP) matrix and reducing the agglomeration of ZO@MH. Afterwards, ZO@MH and KH-570 modified ZO@MH (KZO@MH) filled PP (PP/ZO@MH and PP/KZO@MH) composites are respectively prepared via the melt blending method. The flame retardant and smoke suppression properties of PP/ZO@MH and PP/KZO@MH composites are estimated by a cone calorimetry test (CCT). The peak value of the heat release rate of the PP/40KZO@MH composite is 327.0 kW/m2, which is 6.1% and 31.2% lower than that of the PP/40ZO@MH and PP/40MH composites, respectively. The lowest peak values of CO and CO2 production, 0.008 and 0.62 g/s, also appeared in the PP/40KZO@MH composite, which are 11.1% and 10.1% lower than those of the PP/40ZO@MH composite. Analysis of char residues indicates that nanoscale ZO and modification of KH-570 improve the amount and quality of char residues, which should be the main reason for the good flame retardant and smoke suppression properties of KZO@MH. Impact strength and nominal strain at break results show that the PP matrix is toughened by ZO@MH rather than KZO@MH. Tensile properties and the quantitative interfacial interaction calculated by the Turcsányi equation both prove the reinforcement of KZO@MH on the PP matrix.

Regulating the formation and extent of crazing through the application of argon plasma surface functionalisation

Polymer crazing is a phenomenon observable as fine cracks on the surface of a material. For polymers crazing is often a precursor to mechanical failure with the capacity of a craze to propagate and develop into a larger structural crack. In this study polypropylene (PP) fibres, known to be susceptible to crazing, were subjected to argon (Ar) plasma treatment with the aim of creating a crosslinked surface that displays the ability to withstand the formation of crazes. To evaluate Ar plasma success at achieving this aim: the resulting Ar treated fibres were characterised to evaluate their capacity to avoid the formation of crazes and also identify any changes induced to the chemical and mechanical properties of PP as a consequence of Ar plasma exposure. This analysis was conducted by application of low voltage (LV)-scanning electron microscopy imaging, uniaxial tensile testing, Energy Dispersive X-ray Spectroscopy (EDS) and attenuated total reflectance - fourier-transform infrared spectroscopy (ATR-FTIR). The results of this study highlight the potential of the application of Ar plasma to influence the formation of crazes on PP fibres after exposure to repeated dynamic distention cycles. Ar plasma treated PP also showed a capacity to reduce bulk fibre oxidation when compared to that of non-treated PP when exposed to dynamic distention and subsequently immersed in an oxidative stress environment.

Lignin‐derived flame retardant for improving fire safety and mechanical properties of polypropylene

AbstractIn this work, the self‐assembled lignin‐based flame retardant (LMA) was grafted with γ‐aminopropyltriethoxysilane (APTES) to obtain a novel type of silicon‐containing intumescent flame retardant (LK), which can be applied on polypropylene (PP) to obtain flame retardant PP (PP‐LK). Furthermore, low cost flame retardant PP biocomposite (PP/M/L) with high lignin content were prepared by compounding lignin, LK and PP. The developed PP‐LK and PP/M/L exhibited significant excellent flame retardancy, smoke suppression and mechanical properties. In particular, the UL‐94 test achieved V‐0, and the limit oxygen index (LOI) increased from 17.9% of PP to 28.3% of PP‐LK, and 27.2% of PP/M/L, respectively. Meanwhile, tensile strength and Young's modulus increased by 6.3% and 19.64% for PP‐LK and PP/M/L, respectively. Especially, the tensile strength of PP with 15% LK and 25% lignin achieved 30.88 MPa, and the Young's modulus reached 1415 MPa. The excellent carbonization properties of PP‐LK illustrated that the lignin component of LK had excellent carbonization ability. The prepared LK provided a novel strategy to improve the fire safety and cost of PP, and wide the applications of lignin.

Mechanical properties of isotactic polypropylene with nodular or spherulite morphologies

Abstractα‐form crystalline isotactic polypropylene (PP) was prepared by two methods: quenching from the melt state at slow or high crystallization rates. The mechanical properties of the resulting PP samples were evaluated using tensile and stress–relaxation tests to investigate the influence of nodular or spherulite morphologies. PP samples with different morphologies had almost the same crystallinity after annealing at 100°C for 5 h. The yielding stress, strain‐hardening modulus, and strength of the nodular PP were higher than those of the spherulite PP, although the crystallinity was almost the same for both PP samples. Furthermore, the relaxation time during the stress–relaxation process at ε = 4.0 was longer for the nodular PP than for the spherulite PP. The lamellar structure of a spherulite morphology comprises parent and daughter lamellar crystals, whereas that of a nodular morphology prepared via a mesophase structure comprises only parent lamellar crystals. The formation of the daughter lamellae reduces the number of tie chains. Therefore, the nodular PP has more tie chains than the spherulite PP. This transformation from a spherulite to a nodular morphology improved the mechanical properties of the PP.Highlights Influences of morphology on mechanical properties of polypropylene (PP). Tensile properties were higher for nodular PP than spherulite PP. Relaxation time of nodular PP was longer than spherulite PP. Nodular PP has more tie chains, resulting in improvements of tensile properties.

Preparation of Waste PP/Fly Ash/Waste Stone Powder Composites and Evaluation of Their Mechanical Properties.

The research was carried out to analyze the combined and mechanical properties of polypropylene (PP)/fly ash (FA)/waste stone powder (WSP) composite materials. PP, FA and WSP were mixed and prepared into PP100 (pure PP), PP90 (90 wt% PP + 5 wt% FA + 5 wt% WSP), PP80 (80 wt% PP + 10 wt% FA + 10 wt% WSP), PP70 (70 wt% PP + 15 wt% FA + 15 wt% WSP), PP60 (60 wt% PP + 20 wt% FA + 20 wt% WSP) and PP50 (50 wt% PP + 25 wt% FA + 25 wt% WSP) composite materials using an injection molding machine. The research results indicate that all PP/FA/WSP composite materials can be prepared through the injection molding process and there are no cracks or fractures found on the surface of the composite materials. The research results of thermogravimetric analysis are consistent with expectations, indicating that the preparation method of the composite materials in this study is reliable. Although the addition of FA and WSP powder cannot increase the tensile strength, it is very helpful to improve the bending strength and notched impact energy. Especially for notched impact energy, the addition of FA and WSP results in an increase in the notched impact energy of all PP/FA/WSP composite materials by 14.58-22.22%. This study provides a new direction for the reuse of various waste resources. Moreover, based on the excellent bending strength and notched impact energy, the PP/FA/WSP composite materials have great application potential in the composite plastic industry, artificial stone, floor tiles and other industries in the future.

Influence of Different Hot Runner-Systems in the Injection Molding Process on the Structural and Mechanical Properties of Regenerated Cellulose Fiber Reinforced Polypropylene.

The increasing demand for renewable raw materials and lightweight composites leads to an increasing request for natural fiber composites (NFC) in series production. In order to be able to use NFC competitively, they must also be processable with hot runner systems in injection molding series production. For this reason, the influences of two hot runner systems on the structural and mechanical properties of Polypropylene with 20 wt.% regenerated cellulose fibers (RCF) were investigated. Therefore, the material was processed into test specimens using two different hot runner systems (open and valve gate) and six different process settings. The tensile tests carried out showed very good strength for both hot runner systems, which were max. 20% below the reference specimen processed with a cold runner and, however, significantly influenced by the different parameter settings. Fiber length measurements with the dynamic image analysis showed approx. 20% lower median values of GF and 5% lower of RCF through the processing with both hot runner systems compared to the reference, although the influence of the parameter settings was small. The X-ray microtomography performed on the open hot runner samples showed the influences of the parameter settings on the fiber orientation. In summary, it was shown that RCF composites can be processed with different hot runner systems in a wide process window. Nevertheless, the specimens of the setting with the lowest applied thermal load showed the best mechanical properties for both hot runner systems. It was furthermore shown that the resulting mechanical properties of the composites are not only due to one structural property (fiber length, orientation, or thermally induced changes in fiber properties) but are based on a combination of several material- and process-related properties.

Significantly Improved Foamability and Mechanical Properties of Polypropylene through a Core–Shell Structure via Low Gas Pressure Foam Injection Molding

Lightweight plays an important role in energy conservation and emission reduction. Foam injection molding (FIM) is a promising technology for the mass preparation of structural parts. But it is still a challenge to prepare foam with good cellular structure via low gas pressure foam injection molding (LGP-FIM). Polypropylene (PP) as a kind of universal plastic exhibits good mechanical properties, but its mechanical properties are notably deteriorated after foaming. In this study, ethylene-propylene-diene monomer (EPDM) rubber and high-density polyethylene (HDPE) were added to PP to improve its melt strength and increase the gas diffusion rate. As a result, the cell size of the ternary blend attained was ∼2 μm, and the cell density was increased to 1010 cells/cm3. Meanwhile, the tensile toughness of ternary blend foam increased by 668% compared to PP foam. The notched impact strength of ternary blend foam increased by 178% compared to PP foam. Considering the excellent performance of PP foam and the low cost of LGP-FIM, this work presents a method for fabricating high mechanical performance foams that could be easily industrialized.

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.