Maleated PP Research Articles

Improvement of the impact resistance of natural fiber–reinforced polypropylene composites through hybridization

AbstractPolypropylene (PP) hybrid composites were prepared by the combination of natural reinforcements and poly(ethylene terephthalate) (PET) fibers. Wood, flax, and sugar palm fibers were used to increase stiffness and strength, while PET fibers served to improve impact resistance. Interfacial adhesion was increased by using a maleated PP (MAPP) coupling agent. The hybrid composites containing 20 wt% of the natural fibers were homogenized in a twin‐screw compounder and then injection molded into standard tensile specimens. The amount of PET fibers was changed from 0 to 40 wt% in the composites. Tensile and impact testing, acoustic emission measurements, and scanning electron microscopy (SEM) were used for the characterization of the composites as well as to follow deformation and failure processes. The results proved that the concept of using PET fibers to improve impact resistance works with all natural fibers. Local deformations, the debonding or pullout of the PET fibers, initiate the plastic deformation of the matrix, which consumes considerable energy. The fracture of PET fibers might also contribute to energy absorption. The type of natural fiber does not influence the effect; the amount of PET fibers determines fracture resistance. The improvement of interfacial adhesion by coupling increases strength and slightly improves impact resistance. The overall properties of the hybrid composites prepared are acceptable, sufficiently large stiffness and impact resistance being achieved for a large number of structural applications.

Impact modification of fiber reinforced polypropylene composites with flexible poly(ethylene terephthalate) fibers

AbstractPolypropylene (PP) hybrid composites were prepared by the combination of traditional reinforcements (wood, glass, carbon) and poly(ethylene terephthalate) (PET) fibers. Interfacial adhesion was improved by the use of maleated PP (MAPP). The composites contained 20 wt% of the traditional reinforcement and the amount of PET fiber changed from 0 to 40 wt% in them. Tensile and impact testing were complemented by acoustic emission testing and scanning electron microscopy (SEM) to follow deformation and failure processes. The results obtained proved that the impact strength of hybrid PP composites can be improved in the presence of all stiff fibers and not only wood as shown earlier. Approximately the same impact resistance can be achieved in all composites, which depends on the amount of PET fiber used; an impact strength as large as 15 kJ m−2 can be obtained with the approach. The large impact resistance is the result of the local deformation processes initiated by the polymeric fiber. Irrespectively of the strength of interfacial adhesion, the main local process is the debonding and/or pullout of the PET fibers, which facilitates also the plastic deformation of the matrix polymer. Other properties depend on the type of the reinforcement and on interfacial adhesion. The application of carbon fibers results in composites with large stiffness, while at good adhesion the strength of glass fiber reinforced composites is the largest. The proper selection of components, composition and interfacial adhesion allows the adjustment of overall composite properties in a relatively wide range. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Cysteamine functionalised reduced graphene oxide modification of maleated poly(propylene)

Graphene oxide (GO) was reduced (rGO) and then functionalised with an amino terminated thiol molecule (cysteamine) via a thiol-ene click chemistry reaction to produce reduced graphene oxide-cysteamine (rGO-cyst). The presence of the C–S bond in the X-ray photoelectron spectrum (XPS) confirmed the reaction between the thiol in cysteamine and both the double bonds present on the rGO surface and the pyrazolic structures formed due to reduction. The rGO-cysyteamine was reacted with polypropylene-graft-maleic anhydride (PP-g-MA) to produce PP-g-MA-rGO-cysteamine, where the free amino group present on the rGO-cysteamine reacts with the maleic anhydride group of PP-g-MA. This was confirmed from solid state 13C Magic-Angle-Spinning, Nuclear Magnetic Resonance (MAS NMR), Fourier transform infrared (FTIR) and XPS studies which demonstrated that a mixture of open and closed ring structures based on amides, imides and imines were formed. Growth of the PP chain on the rGO surface was observed from electron microscopy imaging. Cysteamine acts like a ‘cross-linker’ between the rGO and PP-g-MA, increasing interfacial interaction between the two phases resulting in increased thermal stability and altering the crystallization behaviour of the maleated PP. The approach described could be used to compatabilise graphene oxide and a range of polymers to produce functional composite materials.

Reinforcement of PP with polymer fibers: Effect of matrix characteristics, fiber type and interfacial adhesion

Two polypropylene polymers with considerably differing properties were modified with poly(ethylene terephthalate) (PET) and poly(vinyl alcohol) (PVA) fibers. Fiber content changed from 0 to 60 vol% and interfacial adhesion was modified with the addition of a maleated PP coupling agent. Mechanical properties were characterized by tensile and impact testing, while structure was evaluated by acoustic emission measurements and scanning electron microscopy. Attention was focused on the balance of stiffness and impact resistance and on the relationship of local deformation processes to macroscopic properties. The results showed that different inherent matrix properties result in a dissimilar combination of properties. The strength of interfacial adhesion together with matrix properties determines the extent of reinforcement and the direction in the change of properties as a function of composition. Adhesion influences local deformation processes very strongly and these processes determine the macroscopic properties of the composites. Shear yielding induced by the debonding of fibers consumes much energy, while fiber fracture is less efficient in increasing impact resistance. Fiber characteristics are important for modulus and strength, but less significant for impact resistance. A good combination of stiffness and impact resistance can be obtained in PP homopolymers modified with PVA fibers, while this type of modification is less efficient and/or advantageous in elastomer modified PP.

Preparation and Characterization of Amine-Modified Maleated Polypropylene

In this study, reactive processing of maleated polypropylene with different types of amine modifiers, including 1,12-diaminododecane, tetraethylenepentamine, p-phenylenediamine, and 1,6-diaminlhexane were carried out. The changes in melt viscosity, molecular weight and its distribution, as well as crystallization were measured and discussed. All the modified samples exhibited increased molecular weight and enhanced branching structure compared to the virgin maleated PP. Aniline modified sample exhibited the highest weight average molar mass., while polyamide-modified maleated PP showed the highest degree of branching. It was also noted that all of the amine-modified samples showed higher crystallization and melting temperatures than that of the unmodified sample.

Factorial study of material and process parameters on the mechanical properties of extruded kenaf fibre/polypropylene composite sheets

Thin kenaf/polypropylene (PP) composite sheets were manufactured via extrusion. The effects of kenaf and maleated PP (MAPP) proportions, fibre length, PP melt flow index (MFI) and die temperature on tensile, flexural, in-plane and out-of-plane shear properties were analysed by conducting experiments through ‘design of experiments’ methodology. Higher kenaf content and lower die/barrel temperatures resulted in composite sheets with higher average mechanical properties in various modes of testing. Matrix MFI appeared to significantly affect all mechanical properties. It is interesting to note that the properties of the very short-fibre composites produced are comparable to those reinforced with longer discontinuous fibres and long-fibre mats.

Ecotoxicity and fungal deterioration of recycled polypropylene/wood composites: Effect of wood content and coupling

Recycled polypropylene (rPP) was recovered from an industrial shredder and composites were prepared with a relatively wide range of wood content and with two coupling agents, a maleated PP (MAPP) and a maleated ethylene-propylene-diene elastomer (MAEPDM). The mechanical properties of the composites showed that the coupling agents change structure only slightly, but interfacial adhesion quite drastically. The durability of the materials was determined by exposing them to a range of fungi and, ecotoxicity was studied on the aquatic organism Vibrio fischeri. The composites generally exhibit low acute toxicity, with values below the levels considered to have direct ecotoxic effect on aquatic ecosystems (<2 toxic units). Their toxicity to V. fischeri depended on the presence of the coupling agents with larger E50 values in 24-h aqueous extracts from composites containing MAPP or MAEPDM in comparison to composites without any coupling agent. Evaluation of resistance against fungal colonization and deterioration proved that wood facilitates fungal colonization. Fungi caused slight mass loss (below 3%) but it was not correlated with substantial deterioration in material properties. MAPP seems to be beneficial in the retention of mechanical properties during fungal attack. rPP/wood composites can be considered non-ecotoxic and quite durable, but the influence of wood content on resistance to fungal attack must be taken into account for materials intended for applications requiring long-term outdoor exposure.

Extruder‐made TPO nanocomposites. II. Effect of maleated poly(propylene)/organoclay ratio on morphology and thermal expansion behavior

ABSTRACTCoefficients of linear thermal expansion (CTE) for poly(propylene)/ poly(propylene)‐grafted‐maleic anhydride/montmorillonite ethylene‐co‐octene elastomer (PP/PP‐g‐MA/MMT/EOR) blend nanocomposites were determined as a function of MMT content and various PP‐g‐MA/organoclay masterbatch ratios. The nanocomposites were prepared in a twin‐screw extruder at a fixed 30 wt % elastomer, 0–7 wt % MMT content, and various PP‐g‐MA/organoclay ratio of 0, 0.5, 1.0, and 1.5. The organoclay dispersion facilitated by the maleated PP helps to reduce the size of the dispersed phase elastomer particles in the PP matrix. The elastomer particle size decreased significantly as the PP‐g‐MA/organoclay ratio and MMT content increased; the elastomer particles viewed // to flow direction (FD) are smaller and less deformed compared to those viewed // to transverse direction (TD). The elastomer particle shape based on the view along the three orthogonal directions of the injection molded sample is similar to a prolate ellipsoid. The CTE decreased significantly in the FD and TD, whereas a slight increase is observed in the normal direction in the presence of MMT and PP‐g‐MA. The Chow model based on a two population approach showed better fit to experimental CTE when the effect of MMT and elastomer are considered individually. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B Polym. Phys. 2013, 51, 952–965

Thermal, mechanical, and morphological properties of maleated polypropylene compatibilized Borassus fruit fiber/polypropylene composites

AbstractWith a view of exploring the potential use of natural recourses, we made an attempt to fabricate new Borassus fruit fiber/polypropylene composites by melt mixing method using 5 wt % of fiber. Fibers were chemically modified by alkali treatment using maleated PP (MAPP) as compatibilizer to improve the adhesion between fibers and matrix. Thermal, mechanical, and morphological properties of untreated, alkali treated, and MAPP modified fiber reinforced composites were explored by thermogravimetric analysis, differential scanning calorimetry, universal testing machine, and scanning electron microscopy (SEM), respectively. Thermal stability of the composites was enhanced to some extent on alkali treatment and addition of MAPP. The tensile strength and modulus, flexural strength and modulus, and impact strength were increased for alkali treated/MAPP composites by 4.5%, 17%, 17.2 %, 9%, and 10% respectively. SEM studies on tensile fractured specimens of unmodified composites reveal the poor fiber‐matrix interaction, whereas the interaction is strong with enhanced mechanical properties for modified fiber composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effect of compatibilizing agents on the mechanical property of rice husk flour as nano-potential filler in polypropylene biocomposite

In this article, rice husk flour filler/polypropylene (RH/PP) composites with different ratios of the filler were prepared without and with maleated PP, which was used as a compatibilizer. The RH filler in the RH/PP composites was treated with acid and alkali, and their mechanical properties were measured. The mechanical properties were improved with the addition of the compatibilizer. In this study, grafting of maleic anhydride (MA) onto PP with different ratios of benzoyl peroxide (BPO) and MA was prepared. Infrared analysis showed characteristic bands at 1786 and 1863 cm−1 for the grafted sample (maleated PP). Also, from chemical titration, the optimum MA and BPO contents were 4 and 1 part per hundred parts (php of polymer), respectively. The results showed that the morphology of the grafted sample was a flat with coarse surface, and that of the composite clearly elucidated that the interfacial bonding between RH and PP was enhanced by the presence of the compatibilizer. Thermal stability of the grafted PP was enhanced by the grafting process. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Structure–property relationships of polymer blend/clay nanocomposites: Compatibilized and noncompatibilized polystyrene/propylene/clay

AbstractPolymer blends represent an important class of materials in engineering applications. The incorporation of clay nanofiller may provide new opportunities for this type of materials to enhance their applications. This article reports on the effects of clay on the structure and properties of compatibilized and noncompatibilized polymer blends and presents a detailed process for quantitative analysis of the elastic moduli of polymer blend/clay nanocomposites, based on immiscible polystyrene/polypropylene (PS/PP) blends with or without maleated PP as the compatibilizer. The results show that in the noncompatibilized PS/PP/clay nanocomposite clay locates solely in the PS phase, whereas in the compatibilized nanocomposite clay disperses in both phases. The addition of clay to both polymer blends reduces the domain size significantly, modifies the crystallinity and improves the stiffness. The Mori–Tanaka and Christensen's models offer a reasonably good prediction of the elastic moduli of both types of nanocomposites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

Water absorption and dimensional stability of short kenaf fiber‐filled polypropylene composites treated with maleated polypropylene

AbstractThe purpose of this research was to investigate the water absorption behavior and associated dimensional stability of kenaf‐polypropylene‐filled (PP/KF) composites. Composites with different fiber loadings, ranging from 0 to 40 wt %, were prepared with a twin‐screw extruder followed by hot press molding. The influence of the compatibilizer was also studied for PP/KF composite with 5 wt % maleated PP (MAPP). Water absorption testing was carried out at room temperature for 7 weeks. Tensile, flexural, and impact tests were also performed on control, wet, and re‐dried specimens. Increasing the fiber content resulted in higher water absorption and thickness swelling. The inferior mechanical properties of the wet composites were attributed to the effect of water, which deteriorates the interfacial properties of composites. On re‐drying, all properties were almost recovered because of the recovery of interfacial area as evident in scanning electron micrographs. Incorporation of the MAPP significantly improved the compatibility between the fiber and matrix and the mechanical properties of the composites compared with those without MAPP. It also diminished the water absorption as well as the related thickness swelling in the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A comparative study on the electrical and mechanical behaviour of multi‐walled carbon nanotube composites prepared by diluting a masterbatch with various types of polypropylenes

AbstractPolypropylene (PP) nanocomposites with multi‐walled carbon nanotubes (CNT) were produced by a small‐scale masterbatch melt dilution technique using five PP differing in melt flow index (MFI) and degree of maleination. PP used in a masterbatch has MFI = 12 (PP12), the others used PP which have MFI = 2 or MFI = 8. The state of CNT dispersion as assessed by melt rheological and morphological investigations indicated a better dispersion when using unmodified PP with MFI = 8 (PP8) and the masterbatch's PP12. Electrical conductivity results showed nanotube percolation at contents between 1.1 and 2.0 vol %, whereas lower values were obtained for the matrices with the best dispersion, i.e., PP8 and PP12. The dependencies of the relative Young's modulus on the CNT content showed that the maleinization improved the interfacial interactions between the components, especially in the case of maleated PP with MFI = 8 (PP‐MA8), but the better dispersion was prevented by the incompatibility between polar groups of PP‐MA and the nonpolar origin masterbatch PP12. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Polypropylene nanocomposite using maleated PP and diamine

The insertion of the aliphatic diamine inside the organoclay will help the dispersion of the clay platelets in the PP/clay nanocomposite due to the reaction between the maleated PP and the diamine. Cloisite®20A was just simply mixed with hexamethylene diamine (HMDA) under shearing condition in Brabender mixer. HMDA group was successfully penetrated into silicate layers. As a result of penetration, d-spacing of organoclay was increased. Polypropylene/clay nanocomposites were prepared by compounding with maleated PP and amine-treated clay. From the FTIR spectra, reaction between amine group and maleic-anhydride group was confirmed. The effect of the organoclay on the properties of the nanocomposite such as the morphology, dynamic mechanical properties, crystal structure and crystallization behavior, glass transition temperature, thermal stability, and tensile properties were investigated and analyzed. Nanocomposites with amine-treated clays show enhanced properties compared with those with non–amine-treated clay (Cloisite®20A). From the TEM analysis, nanocomposites with amine-treated clays shows better dispersibility compared with those with Cloisite®20A alone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of fiber/matrix chemical modification on the mechanical properties and water absorption of extruded flax/polypropylene composite

AbstractCompound of flax/polypropylene (PP) is characterized concerning the mechanical properties of stiffness, strength, and impact in addition to the water absorption behavior. Manufacturing takes place by twin‐screw extruder. The extruder screw layout is modified through different kneading elements to get high fiber aspect ratio. Sodium hydroxide solution was used as a washing solution for the flax fibers' surfaces. Both fiber and matrix are chemically modified. Selected groups of the fibers were further treated using trimethoxyvinylsilan TMVS and acrylic acid AA. The PP matrix is also treated with different coupling agents; namely, maleated PP MAPP, TMVS‐MAPP, and acrylic acid‐functionalized PP AAPP. The combinations of different fiber/matrix are extruder compounded, injection molded, and finally tested. Fiber modification seems to be positive with AA‐modified surface. AAPP matrix modification improves the stiffness four times that of the untreated flax/PP. Till 30 and 40 wt %, the more the fiber is the more the strength and stiffness, respectively. MAPP‐modified matrix improves the mechanical properties and keeps low water absorption values. AAPP‐modified matrix shows the best stiffness values. TMVS‐MAPP does not seem to have distinguished improvement compared with MAPP. NaOH‐TMVS/MAPP and NaOH‐TMVS/AAPP systems can serve as alternatives to the normal NaOH/MAPP treatment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Processing and properties of mineral‐interfaced cellulose fibre composites

AbstractPolypropylene (PP) or, in some cases, poly (lactic acid) (PLA) were compounded with cellulosic fibres. The amount of fibres used was in the range 10–30 vol % and, in case of PP, a series of compounds was prepared with a minor amount of maleated PP as a compatibiliser. This matrix was denoted MAPP. Before compounding the polymers and the fibres, undelaminated bentonite (industrial scale) or delaminated clay (nanoclay) was deposited on the fibres in different amounts to improve the dispersion of the fibres in the polymer matrix, i. e., to avoid detrimental fibre bundles. The PP‐based compounds were either extruded or injection moulded, whereas the PLA‐compounds were only injection moulded. The mechanical properties were primarily evaluated for the injection moulded specimens. In general, the fibres had a strong effect on the mechanical behaviour of the materials, especially in the case of PLA and MAPP. Treating the fibres with undelaminated clay or nanoclay improved to some extent the dispersion of the fibres and the mechanical performance of the composites, but further optimization of the function of the mineral in this respect is probably required. The combination of the mineral treatment with a debonding agent appeared to be an interesting route here. With such a combination, a visually very good dispersion of the fibres in the PP‐based matrix could be obtained, partly at the expense of the mechanical performance. The compounding of the cellulosic fibres with PP led in this case to a marked decrease in the fibre length. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Fracture toughness of glass microsphere-filled polypropylene and polypropylene/poly (ethylene terephthalate-co-isophthalate) blend-matrix composites

The fracture behaviour of glass microsphere-filled polypropylene/poly(ethylene terephthalate-co-isophthalate) blend-matrix composites was investigated in comparison with that of the glass microsphere-filled PP composites. Depending on the deformability displayed by the composite, it was carried out through the linear-elastic fracture mechanics or by applying the J-integral concept. The matrix ductility was regulated in the composite through the glass bead surface treatment applied with different silane-coupling agents, as well as with the addition of maleated PP as polymer compatibilizer. Whereas all the composites failed in a brittle manner at moderate impact speed, quasi-brittle fracture behaviour was only observed at low strain rate in composites having high and medium interfacial adhesion level. Results showed that composites containing both aminosilane-treated glass microspheres and maleated PP showed the highest values of fracture toughness. In composites with low adhesion level between matrix and glass beads, the critical J-integral value diminished due to the presence of PET.

Piezoresistive behavior of polymer reinforced by expanded graphite

In this study, piezoresistive properties of expanded graphite reinforced polypropylene modified by maleic anhydride were investigated. Expanded graphite as a nanoscale filler dispersed in a polymer matrix was explored in the last few years to examine the novel properties such as dielectric properties and electrical conductivity. It was shown that the change in electrical conductivity was consistent with the classical percolation theory whereby a threshold existed for transition from an insulator to a semi-conductor. Most piezoelectric materials are ceramic based. Little is understood on the piezoresistive behavior of polymer nanocomposites. The expanded graphite reinforced maleated PP in this study were prepared using a melt-compounding method. The percolation threshold of the composite conducting films at room temperature was found to be as low as 0.4 wt%. It was also shown that at a compressive stress less than 10 MPa, the electrical resistivity decreased fairly rapidly with an increase in compressive stress. Thereafter the resistivity reached a steady state and then slightly increased with the increase in the stress exceeding 30 MPa. The electrical response as a function of time under constant stress was investigated experimentally. The results showed that the electrical resistivity decreased significantly with time under high mechanical stress while it increased slightly at a compressive stress of 31 MPa. The potential mechanisms of piezoresistivity is qualitatively discussed in light of the observed experimental data.

The structure and physical properties of polypropylene and thermoplastic olefin nanocomposites containing nanosilica

The morphology and physical properties of thermoplastic olefin blend (TPO) based nanocomposites containing nanosilica are reported. Addition of maleated PP resulted in improved filler dispersion within the PP matrix, where the filler resided exclusively. This separated morphology resulted in selective reinforcement of the PP matrix without compromising ductility, as demonstrated by mechanical property characterization. The tensile moduli, impact and flexural properties of TPO/nanosilica composites showed improvements at low loadings of nanosilica, indicating a good balance of stiffness and toughness. The addition of nanosilica into the TPOs decreased the size of the dispersed elastomer phase, which was a factor in the observed improvements of impact strength. Silane-modified nanosilica dispersed more efficiently in the polymer matrix, giving rise to improved impact properties of the TPO composites, compared to the unmodified filler.

Preparation and mechanical properties of PP/PP-g-MA/Org-MMT nanocomposites with different MA content

Polypropylene-clay nanocomposites were prepared by melt intercalation in a twin screw extruder using two mixing methods: two-step mixing and one-step mixing. The effect of using two different kinds of PP-g-MA (polypropylene-grafted maleic anhydride), with graft efficiencies of 0.1 and 1.0 wt% of MA and with different molecular weight, on clay dispersion and mechanical properties of nanocomposites was investigated. Three different clays, natural montmorillonite (Cloisite Na+) and chemically modified clays Cloisite 20A and Cloisite 30B were used. The relative influence of each factor was observed from structural analysis by WAXD, TEM, and mechanical properties. X-ray diffractometry (XRD) was used to investigate the intercalation effect in the nanocomposites. The results indicted that the intercalation effect and mechanical properties, specially modulus, tensile strength and impact strength, were enhanced by increasing the content of MA, using maleated PP with higher graft efficiency, and using the two step mixing conditions. Better dispersion and exfoliation were obtained when using clay 20A than 30B and natural Na+ montmorillonite. The results showed that clay dispersion and interfacial adhesion are greatly affected by the kind of maleated PP. The increase in content of polar groups gives as a result better interfacial adhesion and subsequent mechanical performance.