Polypropylene Blends Research Articles

Characterization of PS/PP/HDPE/LDPE Polymer Blend Obtained from Plastic Waste Collected on Beaches in Ilhéus-Bahia, Brazil.

A large volume of polymeric waste is generated in cities, and some of this reaches the sea and beaches. This waste stays for hundreds of years, damaging marine environments and organisms. To minimize the effects of pollution, collection and recycling allow a return to the production chain. This research aims to produce and evaluate a polymeric mixture obtained via processing plastic waste collected on the beaches of the city of Ilhéus-Bahia. Subsequently, the mixture is converted into a granulated form for application as fine aggregate in the production of cementitious matrices. A polymer blend of polystyrene, polypropylene, and high- and low-density polyethylene was obtained and evaluated by thermal, morphological, and mechanical tests in three processing stages. The degradation temperatures were close for the three processing stages and the level of processing influenced the mechanical strength. As for elastic modulus and deformation, there was no significant difference in using the mixture processed once or twice. The results showed that the reuse of the waste is applicable, the mixture presented a compact, reasonably homogeneous material with different morphology. Therefore, this work finds importance in the possibility of promoting waste recycling and adding value to a material that would become waste, thus showing its potential for application in the construction industry as an addition to cementitious mixtures and leading to savings in inputs.

Physico-mechanical properties of gamma irradiated polypropylene/ ethylene propylene diene monomer/CaCO3 nanocomposites

ABSTRACT The effect of gamma irradiation on the physico-mechanical properties of nanocomposites-based ethylene propylene diene monomer (EPDM) rubber and polypropylene (PP) blends reinforced with CaCO3 nanoparticles was studied. The nanocomposites were characterized in terms of mechanical, thermal and morphological properties and XRD diffraction. The results indicated, generally, that the elongation at break (E%) was found to decrease by increasing the ratio of PP in the nanocomposite blends and the irradiation dose. The E% values of unirradiated pure EPDM and PP polymers were 1785.0 and 125.0%, respectively. The nanocomposite EPDM/PP (50%)/CaCO3 irradiated to 60 kGy displayed the best properties.

Quasistatic fracture analysis of multicomponent polypropylene blends containing brominated polystyrene

AbstractBrominated flame retardants can be added to many thermoplastics to meet flammability requirements for a range of applications, but can lead to undesirable brittleness. This reduction in toughness can be mitigated by encapsulating the rigid flame retardant with an elastomer. The present study explores the effectiveness of elastomer‐coated brominated polystyrene (BPS) in commercial polypropylene (PP) compositions for improved fracture resistance, where inorganic fillers such as antimony trioxide (ATO) and talc are usually included as synergists for flame‐retardancy. Quasi‐static fracture toughness was determined by J‐integral based on the load separation criterion and the crack growth resistance curve (J vs. Δa). It is found that well dispersed elastomer‐coated BPS can help disperse ATO and talc to exert enhanced toughening effect in PP. Possible fracture mechanisms behind these observed phenomena are discussed.

Thermo-Oxidative Aging Effect on Charge Transport in Polypropylene/Ultra-High Molecular Weight Polyethylene Nanocomposites

This study investigates the impact of magnesium oxide (MgO) nanoparticles on the thermo-oxidative aging behavior of blends of polypropylene (PP) and ultra-high molecular weight polyethylene (UHMWPE). The samples, both unfilled and filled with MgO, were aged at 120 °C for varying durations of up to 672 h. The observed structural changes are not monotonic; recrystallization leads to the increased crystallinity and melting temperature of UHMWPE until 336 h. Beyond this, the consumption of the antioxidant leads to chain scission which, in turn, results in decreased crystallinity. The presence of carbonyl groups indicates chemical changes and, as such, the carbonyl index is used as an indicator of aging, with subsequent changes to charge transport. During thermal aging, the interaction between PP and UHMWPE chains at interfaces is enhanced, leading to improved compatibility and the emergence of a new single crystallization peak in PP/UHMWPE blends. Although MgO does not show evidence of elevating the crystallization temperature, implying the absence of enhanced nucleation, it acts as a compatibilizer, improving interfacial interaction compared with the unfilled blend counterparts. MgO hinders the breakage of molecular structures and impedes the diffusion of oxygen. This, in turn, results in nanocomposites filled with MgO having reduced their charge accumulation and conductivity, thus delaying the aging process compared to PP/UHMWPE blends without nanofiller.

The Effect of Functionalized SEBS on the Properties of PP/SEBS Blends.

Styrene (St) was used as comonomer and glycidyl methacrylate (GMA) as grafting monomer to prepare SEBS-g-(GMA-co-St) graft copolymers via melt grafting. Then, the graft copolymers were employed as a compatibilizer for melt blending polypropylene (PP) and hydrogenated styrene-butadiene-styrene (SEBS) triblock copolymers. The effects of the amount of GMA in the graft copolymers on thermal properties, rheology, crystallization, optical and mechanical properties, and microstructure of the blends were investigated. The results show that GMA and St were successfully grafted onto SEBS. The GMA amount in the graft copolymer significantly influenced the comprehensive properties of PP/SEBS/SEBS-g-(GMA-co-St) blends. The epoxy groups of GMA reacted with PP and SEBS, forming interfacial chemical bonds, thereby enhancing the compatibility between PP and SEBS to varying extents. After introducing SEBS-g-(GMA-co-St) into PP/SEBS blends, crystallinity decreased, crystal size increased while transmittance remained above 91% with rising GMA amount in the graft copolymers, indicating excellent optical properties. Notched impact strength and elongation at break of the blends showed a trend of first increasing and then decreasing with increased amounts of GMA in the graft copolymers. When the amount of GMA in the graft copolymers was 3 wt%, the blends exhibited optimal toughness with notched impact strength and elongation at break of 30,165.82 J/m2 and 1445.40%, respectively. This was attributed to the tightest dispersion interface adhesion and maximum matrix plastic deformation, consistent with the mechanical performance results.

The Cellular Structure and Mechanical Properties of Polypropylene/Nano-CaCO3/Ethylene-propylene-diene-monomer Composites Prepared by an In-Mold-Decoration/Microcellular-Injection-Molding Process.

Polypropylene (PP)-composite foams were prepared by a combination process of microcellular injection molding (MIM) and in-mold decoration (IMD). The effect of ethylene propylene diene monomer (EPDM) on the crystallization properties, rheological properties, microstructure, and mechanical properties of PP-composite foams was studied. The effect of the additives on the strength and toughness of PP-composite foam as determined by the multiscale simulation method is discussed. The results showed that an appropriate amount of EPDM was beneficial to the cell growth and toughening of the PP blends. When the content of EPDM was 15 wt%, the PP-composite foams obtained the minimum cellular size, the maximum cellular density, and the best impact toughness. At the same time, the mesoscopic simulation shows that the stress concentration is the smallest, which indicates that 15 wt% EPDM has the best toughening effect in these composite materials.

Interfacial shear strength of surface functionalized and functionalized CNT coated carbon fiber: A single fiber fragmentation study

The compatibility among nonpolar thermoplastics like polypropylene (PP) and carbon fibers (CF) having traditional sizing or coating is challenging. In this study, facile and effective surface functionalization of CF and its subsequent coating with functionalized carbon nanotubes (CNTs) were carried out to obtain improved interfacial shear strength (IFSS) which was validated by the single fiber fragmentation test (SFFT). Functional groups, -COOH, -OH, and -NH2, were separately grafted on the CF surface using different chemical routes. Additionally, ultrasonic assisted electrophoretic deposition (EPD) technique was used to coat -COOH, -OH, and -NH2 functionalized CNTs on the sized and surface functionalized CFs. Attenuated total reflection-infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FE-SEM) images confirmed the successful surface functionalization and coating on CF. Neat PP and a blend of PP and maleic anhydride-grafted-styrene ethylene butylene styrene (MA-g-SEBS) were used as two different base polymer matrixes in preparing a total of 26 different SFFT samples. Silane functionalized CF coated with amine functionalized CNTs using ultrasonic assisted EPD process showed IFSS of ∼29 MPa which was an impressive ∼758% higher than pristine CF and highest among all the surface modified CFs. Interestingly, this translated into useful increase of ∼13% in single fiber tensile strength of functionalized and treated CF over and above that of as received CF.

Cooperative Effect of Ni-Decorated Monolayer WS2, NiO, and AC on Improving the Flame Retardancy and Mechanical Property of Polypropylene Blends.

Improving the residual char of polypropylene (PP) is difficult due to the preferential complete combustion. Here, we designed a combination catalyst that not only provides physical barrier effects, but also dramatically promotes catalytic charring activity. We successfully synthesized WS2 monolayer sheets decorated with isolated Ni atoms that bond covalently to sulfur vacancies on the basal planes via thiourea. Subsequently, PP blends composed of 8 wt.% Ni-decorated WS2, NiO, and activated carbon (AC) were obtained (ENi-SWS2-AC-PP). Combining the physical barrier effects of WS2 monolayer sheets with the excellent catalytic carbonization ability of the ENi-SWS2-AC combination catalyst, the PP blends showed a remarkable improvement in flame retardancy, with the yield of residual char reaching as high as 41.6 wt.%. According to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations, it was revealed that the microstructure of residual char contained a large number of carbon nanotubes. The production of a large amount of residual char not only reduced the release of pyrolytic products, but also formed a thermal shield preventing oxygen and heat transport. Compared to pure PP, the peak heat release rate (pHRR) and total heat release rate (THR) of ENi-SWS2-AC-PP were reduced by 46.32% and 26.03%, respectively. Furthermore, benefiting from the highly dispersed WS2, the tensile strength and Young's modulus of ENi-SWS2-AC-PP showed similar values to pure PP, without sacrificing the toughness.

Hybrid multiwalled‐carbon nanotube/nanosilica/polypropylene nanocomposites: Morphology, rheology, and mechanical properties

AbstractPolymer composite are very interesting materials in automotive industry. Nanocomposites play a crucial role in the automotive parts and cars weight reduction fields. Hybridization of polymer nanocomposites is appeared as a process of choice in obtaining the required property/weight ration. Simple and hybrid nanocomposites of polypropylene (PP) blend with carbon nanotubes (CNTs) having different aspect ratios and nanosilica at different nanosilica contents were prepared in molten state in an internal mixer. Scanning electron microscopic images along with rheological and tensile properties revealed that only 0.2 wt% CNT is high enough to finely disperse nanosilica particles in PP matrix in the absence of any chemical compatibilizer. Differential scanning calorimetric thermograms showed that none of nanoparticles has any effect on crystallinity of PP. Mechanical characterizations showed that hybrid composites are superior to PP‐S3 composite. Due to its more intensive hydrodynamic motions it was also observed that the longer CNT showed a higher ability to disintegrate nanosilica particles aggregates. Transmission electron microscopic images well portrayed the nanosilica particles in the vicinity of CNTs' surfaces which accounts for electrostatic adsorption of fine nanosilica particles. At such a low CNT content (say 0.2 wt%) in the absence of any chemical compatibilizer, elongation at break of the tensiled nanocomposites raised from 13.23% to 35.41% and fracture energy was mounted from 1253 to 2750 J. This divulges the effectiveness of CNTs to disperse nanosilica in PP matrix but a poor adhesion between the particles and PP matrix is an overwhelming drawback yet. Under these conditions a maleic anhydride grafted PP (PP‐g‐MA) was added to the composite in molten state. The tensile strength of these chemically compatibilized nanocomposites increased with respect of that of their counterpart physically mixed nanocomposites. For example, in the presence of this chemical compatibilizer, the tensile strength of PP‐S3 nanocomposite raised from 21 to 28 MPa.

Effect of the Chemical Modification of Diatomite/Isotactic Polypropylene Composite on the Rheological, Morphological and Mechanical Properties

The present study deals with the effect of the Diatomite (D) microcomposite with and without chemical modification in a polypropylene (iPP) blend. The objective is to achieve a material with a better performance at a lower cost and more accessible and more suitable processing. The chemical surface modification of Diatomite (MD) was achieved using a crosslinking system based on a mixture of sulfur, accelerator, and peroxide. The iPP/Diatomite composite was prepared by batch melt mixing in a Brabender Plasti-Corde under intense shearing at high temperatures and varying the Diatomite content from 0 to 15 wt%. The rheological behavior was examined by monitoring the Brabender Plasti-Corde torque/time rheographs. Different techniques were used to characterize the sample: Fourier transform infrared spectroscopy (FTIR), WAXS, SEM, and DSC. In addition, tensile strength tests and impact strength mechanical tests were conducted to study the performance. It was found that chemical modification strongly affected rheological behavior and generated a new rheological characteristic compared to the composites without modification. This has induced a new structure form that has improved mechanical properties. Moreover, the chemical modification used and due to its simplicity, can be successfully used on an industrial scale with the appropriate process.

Polypropylene Blends for Highly Drawn Tapes with Improved Toughness.

In this study, we used four amorphous poly-alpha-olefin (APAO) grades to improve the toughness of drawn polypropylene (PP) tapes. The samples containing different amounts of APAOs were drawn in a heat chamber of a tensile testing machine. The APAOs reduced the work of drawing and increased the melting enthalpy of the drawn specimens, as they facilitated the movement of the PP molecules. The APAO with the highest molecular weight and with a low level of crystallinity increased both the tensile strength and the strain-at-break of the specimens, so we also produced drawn tapes from that PP/APAO blend on a continuous-operation stretching line. The continuously drawn tapes also showed improved toughness.

Mixing rules for high density polyethylene‐polypropylene blends

AbstractHigh‐density polyethylene (HDPE) and polypropylene (PP) blends of varying composition have been evaluated in an effort to establish a mixing rule for melt flow index (MFI). In addition, a previously established relationship between MFI and for linear polymers was also evaluated for these blends. It was found that a parabolic relationship existed between the composition (by weight fraction) and MFI and that the MFI and relationship held for this set of polymeric materials. Additionally, all properties and relationships were evaluated over five extrusion cycles, which showed minimal to no deviations over the five cycles.

Optimizing the blending ratio and processing parameters for ternary blends of recycled polypropylene with recycled high and virgin linear low-densities polyethylene

The thermoplastic polymer of polypropylene (PP) is employed in many different applications. A huge amount of PP waste is produced by using its discarded parts. Recycled polypropylene (rPP) does not provide virgin properties and further reuse causes more loss of properties. This study investigates experimentally the effect of adding different ratios of recycled high-density polyethylene (rHDPE) and virgin linear low-density polyethylene (vLLDPE) with different process variables on the rPP's tensile strength. The most significant injection factors of melt temperature, injection pressure, holding pressure, holding time, and cooling time with the ternary blend ratio were proposed with three levels. Also, three different compositions of I, II and III with 85/12/3, 85/3/12, and 85/8/7 wt percent are considered respectively to the levels of the rPP/rHDPE/vLLDPE blend. Accordingly, 18 experiments are designed based on Taguchi's orthogonal array (OA) of L18. An injection molding die is designed and manufactured to produce tensile test samples. Scanning electron microscopic (SEM) is applied to show the microstructure of the blends. The response data of ultimate tensile stress are transmitted to signal-to-noise ratio (S/N) to facilitate their analysis by analysis of variance (ANOVA). Finally, the optimum set of parameters that provides the optimal blend with the highest ultimate stress of 21.62 MPa was defined. Additionally, according to the P-values the most significant parameters are holding pressure, injection pressure, and cooling time, respectively.

Tailoring the mechanical properties of binary polypropylene blends with polymorphic and oriented hierarchical structures

Tailoring the mechanical properties of binary polypropylene blends with polymorphic and oriented hierarchical structures

Reactive Blending of Recycled Poly(ethylene terephthalate)/Recycled Polypropylene: Kinetics Modeling of Non-Isothermal Crystallization.

Plastics were developed to change our world for the better. However, plastic pollution has become a serious global environmental crisis. Thermoplastic polyesters and polyolefins are among the most abundant plastic waste. This work presents an in-depth non-isothermal crystallization kinetics analysis of recycled post-consumer poly(ethylene terephthalate) (rPET) and recycled polypropylene (rPP) blends prepared through reactive compounding. The effect of pyromellitic dianhydride (PMDA) on crystallization kinetics and phase morphology of rPET/rPP blends was investigated by differential scanning calorimetry (DSC) and microscopy techniques. DSC results showed that increasing rPP content accelerated rPET crystallization while reducing crystallinity, which indicates the nucleation effect of the rPP phase in blends. Further, it was found that the incorporation of PMDA increased the degree of crystallinity during non-isothermal crystallization, even though the rate of crystallinity decreased slightly due to its restriction effects. The non-isothermal crystallization kinetics was analyzed based on the theoretical models developed by Jeziorny, Ozawa, Mo, and Tobin. The activation energy of the crystallization process derived from Kissinger, Takhor, and Augis-Bennett models was found to increase in rPET/rPP blends with increasing PMDA due to hindered dynamics of the system. Rheological measurements revealed that rPET melt viscosity is remarkably increased in the presence of PMDA and reactive blending with rPP relevant for processing. Moreover, nanomechanical mapping of the rPP phase dispersed in the rPET matrix demonstrated the broadening of the interfacial domains after reactive blending due to the branching effect of PMDA. Findings from this study are essential for the recycling/upcycling thermoplastics through non-isothermal fabrication processes, such as extrusion and injection molding, to mitigate the lack of sorting options.

Employing impedance spectroscopy to investigate electrical conduction mechanism in polymer composite blends containing conductive masterbatch: PP/EVA/ (PP-g-MA/MWCNTS)

Impedance spectroscopy analysis has been employed to investigate the effect of melt mixing time on electrical conduction mechanism, direct contact or electron tunneling, of a polymer blend using a conductive masterbatch. A novel approach is proposed to correlate the dispersion/distribution states of conductive nanoparticles within the phases, achieved through kinetic control of the conductive masterbatch, and their impedance properties. A blend of polypropylene and ethylene-vinyl acetate copolymer (PP/EVA) was considered as a case study for the matrix. An electrically conductive masterbatch of multiwalled carbon nanotubes (MWCNTs) in polypropylene-grafted-maleic anhydride (PP-g-MA) was added to the blend. The masterbatch in varying amounts was mixed with PP/EVA in a range of 1 min–4.5 min. The co-continuous morphology of the ternary polymer blend was validated via scanning electron microscopy micrographs. The atomic force microscopy (AFM) results showed that as the mixing time of the masterbatch increases the interconnected structures within the conductive interphase decrease. Impedance spectroscopy using alternating current was employed to probe the conduction mechanism in the composite blends. The impedance spectroscopy results revealed that for samples with low mixing time, a dielectric relaxation peak occurs at high frequencies due to the existence of more conductive pathways as a consequence of the interconnected structures of the masterbatch phase. Also, the major contribution of conductance was direct contact in the samples with low mixing times while electron tunneling mechanism was considerable for the samples with high mixing times. Dielectric constant was increased as a result of interfacial polarization boosting with mixing time. The percolation threshold was considerably decreased from 0.95 v% for simultaneous direct mixing method to 0.16 v% for the masterbatch method.

Enhancement of the Mechanical and Thermal Properties of Polypropylene and Nylon 6.6 Composite Blends

The mechanical and thermal properties of nylon 6.6 on polypropylene (PP) blends were investigated. Five weight percentages of nylon 6.6, 1 wt%—5 wt%, were blended with PP by an injection molding process to produce PP/nylon 6.6 blends. The impact of the mixture on the mechanical properties was investigated by performing a three-point bend test to determine the flexural strength and hardness test using nanoindentation. Both differential scanning calorimetry and thermogravimetric analysis were used to study the thermal properties of the mixture. Chemical and morphological testing was performed by Fourier-transform infrared spectroscopy and scanning electron microscope tests. Mechanical testing revealed improved strength, modulus, and hardness of the PP/nylon 6.6 blends. The 2 wt% blend showed elastic modulus, tensile, and yield stress enhancement. TGA showed variable results with improved thermal resistance for the 3 wt% and 4 wt% blends, whereas there was no effect for the 2 wt% blend and reduced thermal resistance for the 1 wt% and 5 wt% blends. DSC analysis revealed no influence on the melting temperature of the blends. SEM images showed a homogeneous mixture between PP and nylon 6.6, which substantiated the interfacial adhesion between PP and nylon 6.6 and was verified by FTIR.

Glycol lignin/MAH-g-PP blends and composites with exceptional mechanical properties for automotive applications

Lightweight plastics and their composites are being increasingly used in automobiles to reduce emissions and costs, but the market demand for fossil fuel-based plastics such as polypropylene (PP) creates several environmental problems such as pollution and waste. Although replacing PP with biomass such as lignin is not a new endeavor, the vast majority of past studies reported reduced mechanical properties as lignin content increases, which limits its application in industry. Herein, blends of maleic anhydride-grafted PP (MAH-g-PP) and softwood-derived glycol lignin (GL) are successfully fabricated via a melt-mixing approach, which boast exceptional mechanical properties and thermal stability. Synergistic performance enhancement is observed when combined with carbon fiber reinforcement, which is elucidated by nanoindentation of the fiber/polymer interface. This work contributes to the development of sustainable automotive structures by efficiently combining biomass and traditional materials.

Aquatic Biodegradation of Poly(β-Hydroxybutyrate) and Polypropylene Blends with Compatibilizer and the Generation of Micro- and Nano-Plastics on Biodegradation

Aquatic Biodegradation of Poly(β-Hydroxybutyrate) and Polypropylene Blends with Compatibilizer and the Generation of Micro- and Nano-Plastics on Biodegradation

Interactions of polymeric components in a POM-based binder system for titanium metal injection moulding feedstocks

ABSTRACT Owing to the different characteristics of each of the multiple polymers, obtaining a homogenous metal injection moulding (MIM) feedstock blend is challenging. Therefore, studying interactions between the polymeric components is vital for achieving suitable MIM feedstocks. We report on the effects of different compatibilisers – EGMA and E40 – on the interactions in polyoxymethylene (POM) and polypropylene (PP) blends. We measured contact angles and performed Fourier transform infrared spectroscopy and atomic force microscopy analyses to identify the suitable compatibiliser that yields a feedstock with excellent properties. It was found that the binder system based on EGMA-3 demonstrates the lowest contact angle and best miscibility for the POM/PP blends compared to E40. This enhanced interaction lies in the chemistry of EGMA, having an active site that reduces the interfacial tension between the components of the POM/PP blend. Subsequently, this creates a positive interaction between the polymers and metal powders, ensuring good adhesion within the feedstock.