Effects of methyl methacrylate grafting and polyamide coating on the interfacial behavior and mechanical properties of jute‐fiber‐reinforced polypropylene composites

In recent years, environmentally friendly materials have become popular because of the growing environmental demands in human society. Natural fibers are now widely used as reinforcements in polymer matrix composites for their various advantages such as low cost, light weight, abundant resources, and biodegradability. However, the applications of these kinds of composites are limited because of their unsatisfactory mechanical properties, which are caused by the poor interfacial compatibility between the fibers and the thermoplastic matrix. In this paper, three methods, including (i) alkali treatment, (ii) alkali and methyl methacrylate (MMA) treatment, and (iii) alkali and polyamide (PA) treatment (APT), were used to treat jute fibers and improve the interfacial adhesion of jute‐fiber‐reinforced polypropylene (PP) composites (JPCs). The mechanical properties of the JPCs were tested, and their impact fracture surfaces were observed. Infrared spectral analysis showed that MMA was grafted and that PA was coated onto the surface of jute fibers. Mechanical tests indicated that the three kinds of pretreated composites presented better mechanical properties than untreated composites. Among them, the APT composite had the best comprehensive properties. Compared with untreated composites, the tensile strength, flexural strength, and flexural modulus of APT composite were increased by 24.8, 31.3, and 28.4%, respectively. Analysis by scanning electron microscopy showed that better interfacial compatibility between jute fibers and PP occured in this kind of composite. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Morphology/behavior relationship and recyclability of composites based on PP/EPDM blends and short aramid fibers

The effect of short aramid fibers on the mechanical behavior of polypropylene (PP) and ethylene‐propylene‐diene (EPDM) and their blends has been investigated by means of an experimental design. The results have shown that aramid fibers are very effective reinforcing agents for composites when the continuous phase of the matrix is constituted by PP, so sensible increments in tensile modulus and strength are obtained as fiber content in the composites increases. An optimal matrix composition and fiber content has been observed that produced high abrasion resistance compounds. However, the abrasion resistance of very rich EPDM matrices is hardly affected by fibers content. The addition of fibers to EPDM rich (>50%) matrices gives rise to a sensible decrease of the impact strength of this polymer. However, at PP contents above 50% in the polymer matrix, an increase of impact strength is observed at fiber percentages in the composites above 10%. The different behavior of the fibers depending on matrix type can be attributed to a better affinity of these fibers for PP matrix. Morphological studies of the composites have been carried out by scanning electron microscopy. Finally, the price and recyclability of these materials have been analyzed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2474–2484, 2002     

Effects of alkali and silane treatment on the mechanical properties of jute‐fiber‐reinforced recycled polypropylene composites

Jute‐fibers‐reinforced thermoplastic composites are widely used in the automobile, packaging, and electronic industries because of their various advantages such as low cost, ease of recycling, and biodegradability. However, the applications of these kinds of composites are limited because of their unsatisfactory mechanical properties, which are caused by the poor interfacial compatibility between jute fibers and the thermoplastic matrix. In this work, four methods, including (i) alkali treatment, (ii) alkali and silane treatment, (iii) alkali and (maleic anhydride)‐polypropylene (MAPP) treatment, and (iv) alkali, silane, and MAPP treatment (ASMT) were used to treat jute fibers and improve the interfacial adhesion of jute‐fiber‐reinforced recycled polypropylene composites (JRPCS). The mechanical properties and impact fracture surfaces of the composites were observed, and their fracture mechanism was analyzed. The results showed that ASMT composites possessed the optimum comprehensive mechanical properties. When the weight fraction of jute fibers was 15%, the tensile strength and impact toughness were increased by 46 and 36%, respectively, compared to those of untreated composites. The strongest interfacial adhesion between jute fibers and recycled polypropylene was obtained for ASMT composites. The fracture styles of this kind of composite included fiber breakage, fiber pull‐out, and interfacial debonding. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers.     

The influence of chemical surface modification on the performance of sisal‐polyester biocomposites

This article concerns the effectiveness of various types and degrees of surface modification of sisal fibers involving dewaxing, alkali treatment, bleaching cyanoethylation and viny1 grafting in enhancing the mechanical properties, such as tensile, flexural and impact strength, of sisal‐polyester biocomposites. The mechanical properties are optimum at a fiber loading of 30 wt%. Among all modifications, cyanoethylation and alkali treatment result in improved properties of the biocomposites. Cyanoethylated sisal‐polyester composite exhibited maximum tensile strength (84.29 MPa). The alkali treated sisal‐polyester composite exhibited best flexural (153.94 MPa) and impac strength (197.88 J/m), which are, respectively, 21.8% and 20.9% higher than the corresponding mechanical properties of the untreated sisal‐polyester composites. In the case of vinyl grafting, acrylonitrile (AN)‐grafted sisal‐polyester composites show better mechanical properties than methyl‐methacrylate (MMA)‐grafted sisal composites. Scanning electron microscopic studies were carried out to analyze the fiber‐matrix interaction in various surface‐modified sisal‐polyester composites.     

Influence of fiber surface treatment on mechanical performance of Xanthoceras sorbifolia bunge husk fibers/PP composites

The PP Composites containing Xanthoceras sorbifolia Bunge husks fibers with different surface treatments were prepared. The mechanical properties such as tensile properties and impact properties of the composites were investigated. It is revealed that the composites with fibers treated by alkali and the following treatments of silane coupling agents KH570, titanate coupling agent JN‐9A, acetic anhydride, MAPP, or bleach, all performed higher in tensile properties than that with untreated fibers, while lower in impact properties. Meanwhile, all treated fibers performed better thermal stability than untreated fibers. The fibers treated by alkali followed by KH570 treatment were added into PP with different contents. It is found that as the fiber content increases, the elastic modulus and impact strength of the composites increase sharply at first followed by a decrease, while the tensile strength decrease initially and increase with a peak at 10%, then decrease continuously. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41217.     

Mechanical,thermal, and morphological properties of maleic anhydride‐g‐polypropylene compatibilized and chemically modified banana‐fiber‐reinforced polypropylene composites

Composites were prepared with chemically modified banana fibers in polypropylene (PP). The effects of 40‐mm fiber loading and resin modification on the physical, mechanical, thermal, and morphological properties of the composites were evaluated with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Infrared (IR) spectroscopy, and so on. Maleic anhydride grafted polypropylene (MA‐g‐PP) compatibilizer was used to improve the fiber‐matrix adhesion. SEM studies carried out on fractured specimens indicated poor dispersion in the unmodified fiber composites and improved adhesion and uniform dispersion in the treated composites. A fiber loading of 15 vol % in the treated composites was optimum, with maximum mechanical properties and thermal stability evident. The composite with 5% MA‐g‐PP concentration at a 15% fiber volume showed an 80% increase in impact strength, a 48% increase in flexural strength, a 125% increase in flexural modulus, a 33% increase in tensile strength, and an 82% increase in tensile modulus, whereas the heat deflection temperature increased by 18°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical properties of wood-fiber/toughened isotactic polypropylene composites

This study investigates the mechanical properties of wood-fiber/toughened PP composite modified by physical blending with an EPDM rubber to improve impact toughness. Wood-fiber thermoplastic composites were prepared with a modified PP matrix resin, employing high shear thermokinetic compounding aided with maleated PP for the fiber dispersion. The addition of EPDM improved the impact toughness, while it reduced stiffness and strength properties. To compensate the non-plane strain fracture toughness, the specimen strength ratio (R_sb) was adopted as a comparative measure of fracture toughness. The strength ratio increased with the addition of EPDM, while it decreased with increasing wood-fiber concentration. The work of fracture increased with EPDM level except at large wood-fiber concentration. The effectiveness of the impact modification was assessed with the balance between tensile modulus and unnotched impact energy as a function of wood-fiber concentration. EPDM rubber modification was moderately effective for wood-fiber PP composites. The examination of fracture surfaces showed twisted fibers, fiber breakage, and fiber pull-out from the matrix resin.     

Use of wet‐laid techniques to form flax‐polypropylene nonwovens as base substrates for eco‐friendly composites by using hot‐press molding

The wet‐laid process with flax (base) and polypropylene (binder) fibers has been used to obtain nonwovens for further processing by hot‐press molding. Mechanical characterization of nonwovens has revealed that slight anisotropy is obtained with the wet‐laid process as better tensile strength is obtained in the preferential deposition direction. The thermo‐bonding process provides good cohesion to nonwovens, which is critical for further handling/shaping by hot‐press molding. Flax:PP composites have been processed by stacking eight individual flax:PP nonwoven sheets and applying moderate temperature and pressure. As the amount of binder fiber is relatively low (<30 wt%) if compared with similar systems processed by extrusion and injection molding, it is possible to obtain eco‐friendly composites as the total content on natural fiber (flax) is higher than 70 wt%. Mechanical characterization of hot‐pressed flax:PP composites has revealed high dependency of tensile and flexural strength on the total amount of binder fiber as this component is responsible for flax fiber embedment which is a critical parameter to ensure good fiber–matrix interaction. Combination of wet‐laid techniques with hot‐press molding processes is interesting from both technical and environmental points of view as high natural fiber content composites with balanced properties can be obtained. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Conifer fibers as reinforcing materials for polypropylene‐based composites

Conifer fibers were used to reinforce polypropylene (PP). To improve the compatibility between the conifer fibers and the PP matrix, the fibers were either grafted with maleated PP (MAPP), treated by adding MAPP, or mixed with ethylene/propylene/diene terpolymer (EPDM). The treatments resulted in improved processing, as well as improvements in the thermal and mechanical properties of the resultant composites compared with the composites filled with untreated conifer fibers. Moreover, MAPP grafting and MAPP treating displayed more obvious benefits than EPDM treating in terms of thermal properties, processing flowability, and tensile strength improvements. EPDM treating also produced more significant benefits than either MAPP grafting or MAPP treating in terms of impact strength and tensile elongation improvements. These improvements were attributed to surface coating of the fibers when EPDM was used. In addition, the effect of the concentration of the conifer fibers on the properties of the composites and the difference between MAPP grafting and MAPP treating were evaluated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2833–2841, 2001     

Unidirectional hemp and flax EP‐ and PP‐composites: Influence of defined fiber treatments

In some technical areas, mainly in the automotive industry, glass fiber reinforced polymers are intended to be replaced by natural fiber reinforced polymer systems. Therefore, higher requirements will be imposed to the physical fiber properties, fiber‐matrix adhesion, and the quality assurance. To improve the properties of epoxy resins (EP) and polypropylene (PP) composites, flax and hemp fibers were modified by mercerization and MAH‐PP coupling agent was used for preparing the PP composites. The effects of different mercerization parameters such as concentration of alkali (NaOH), temperature, and duration time along with tensile stress applied to the fibers on the structure and properties of hemp fibers were studied and judged via the cellulose I–II lattice conversion. It was observed that the mechanical properties of the fibers can be controlled in a broad range by using appropriate mercerization parameters. Unidirectional EP composites were manufactured by the filament winding technique; at the PP matrix material, a combination with a film‐stacking technique was used. The influence of mercerization parameters on the properties of EP composites was studied with hemp yarn as an example. Different macromechanical effects are shown at hemp‐ and flax‐PP model composites with mercerized, MAH‐PP‐treated, or MAH‐PP‐treated mercerized yarns. The composites' properties were verified by tensile and flexural tests. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2150–2156, 2004     

Preparation and properties of peroxide dynamically vulcanized polypropylene/ethylene‐propylene‐diene monomer/zinc dimethacrylate thermoplastic olefin

Attempts were made to prepare the polypropylene (PP) /ethylene‐propylene‐diene monomer (EPDM) blends with zinc dimethacrylate (ZDMA) via peroxide dynamic vulcanization. PP was melt‐mixed with EPDM and ZDMA at different compositions (PP/EPDM/ZDMA, i.e., 70/30/0, 70/30/3, 70/30/6, and 70/30/9, w/w/w) using an internal mixer at 50 rpm rotor speed. The addition of ZDMA improved the rheological properties of the resulting materials in the melt state. The morphological studies revealed that the addition of ZDMA led to an improvement of size reduction and distribution uniformity for crosslinked EPDM phase. ZDMA showed a positive effect on the mechanical properties of the PP/EPDM/ZDMA composites, particularly on the toughness and extensibility. With the incorporation of ZDMA, the izod impact strength and the elongation of PP/EPDM/ZDMA composites increased from 41 kJ/m² to 72 kJ/m² and 110% to 495%, respectively. The crystallization behaviors analysis indicated that the addition of ZDMA promoted the nucleation process of PP but the crystallinity of the PP phase was decreased at the meantime. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Long jute fiber‐reinforced polypropylene composite: Effects of jute fiber bundle and glass fiber hybridization

Two types of long jute fiber pellet consisting of twisted‐jute yarn (LFT‐JF/PP) and untwisted‐jute yarn (UT‐JF/PP) pellets are used to prepare jute fiber–reinforced polypropylene (JF/PP) composites. The mechanical properties of both long fiber composites are compared with that of re‐pelletized pellet (RP‐JF/PP) of LFT‐JF/PP pellet, which is re‐compounded by extrusion compounding. High stiffness and high impact strength of JF/PP composites are as a result of using long fiber. However, the longer fiber bundle consequently affects the distribution of jute fiber. The incorporation of 10 wt % glass fibers is found to improve mechanical properties of JF/PP composites. Increasing mechanical properties of hybrid composites is dependent on the type of JF/PP pellets, which directly affect the fiber length and fiber orientation of glass fiber within hybrid composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41819.     

Influence of PANI‐complex on the mechanical and electrical properties of carbon fiber reinforced polypropylene composites

The aim of this work was to determine the influence of PANI‐complex on the mechanical and electrical properties of CF‐PP composites. As expected, an increase in tensile strength and modulus of the PP matrix could be achieved with an increasing fiber weight fraction. On the other hand, the PANI‐complex decreased the tensile strength and modulus of the fiber reinforced composites; however, these values remained on a better level than the value of the neat PP. Further, by using a long carbon fiber (LCF) reinforcement instead of short carbon fibers (SCF) the percolation threshold was moved towards a lower fiber weight content. In addition, a synergy effect between PANI‐complex and LCF in the PP‐matrix regarding the electrical properties occurred. In particular, an abrupt decrease in the surface resistivity could be avoided. Also, the surface resistivity of a blend is better when the blend consists of both PANI‐complex and LCF instead of only one of these fillers.     

Effect of hybridization and compatibilization on the mechanical properties of recycled polypropylene‐hemp composites

Hemp fibers and particles, with different sizes and contents, were used to make hybrid composites based on recycled polypropylene (PP). In particular, the effect of maleated polypropylene (MAPP) addition on the morphology and mechanical properties is reported. The results show that better adhesion is obtained with MAPP addition. In general, fiber content and size had a substantial effect on the tensile, flexural, torsion, and impact properties of the resulting composites. Although, adding MAPP to the samples improved the impact strength of the composites, the values were always lower than neat PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Impact modification of polypropylene‐based composites using surface‐coated waste rubber crumbs

Blends of maleated polypropylene (MAPP) with high contents of waste rubber powder, namely ground tire rubber and waste ethylene propylene diene monomer (EPDM) powder, were used as impact modifiers for polypropylene (PP) based composites with different reinforcements (hemp, talc, and milled glass fiber). Adding reinforcements led to increase in modulus (tensile, flexural, and torsion moduli) of PP, while its impact strength decreased noticeably. Impact modification of PP‐based composites was successfully performed via inclusion of MAPP/waste rubber compounds, especially compounds containing waste EPDM powder. Inclusion of such impact modifiers increased impact strength of composites over 80%. The effects of impact modification were more significant for hemp‐ and glass‐filled composites compared to composites containing talc. However, slight decrease in tensile, flexural, and torsion moduli (up to 30%) of the composites was also observed after inclusion of impact modifiers. POLYM. COMPOS., 35:2280–2289, 2014. © 2014 Society of Plastics Engineers     

Non‐traditional lightweight polypropylene composites reinforced with milkweed floss

Lightweight composites are preferred for automotive applications due to the weight restrictions and also due to the presence of inherent voids that can enhance the sound absorption of these composites. The density of the reinforcing materials plays a crucial role in such lightweight composites. Milkweed is a unique natural cellulose fiber that has a completely hollow center and low density (0.9 g cm^?3) unlike any other natural cellulose fiber. The low density of milkweed fibers will allow the incorporation of higher amounts of fiber per unit weight of a composite, which is expected to lead to lightweight composites with better properties. Polypropylene (PP) composites reinforced with milkweed fibers have much better flexural and tensile properties than similar PP composites reinforced with kenaf fibers. Milkweed fiber‐reinforced composites have much higher strength but are stiffer than kenaf fiber‐reinforced PP composites. Increasing the proportion of milkweed in the composites from 35 to 50% increases the flexural strength but decreases the tensile strength. The low density of milkweed fibers allows the incorporation of higher amounts of fibers per unit weight of the composites and hence provides better properties compared to composites reinforced with common cellulose fibers with relatively high density. This research shows that low‐density reinforcing materials can more efficiently reinforce lightweight composites. Copyright © 2010 Society of Chemical Industry     

Novel eco‐friendly biodegradable coir‐polyester amide biocomposites: Fabrication and properties evaluation

Biocomposites are prepared from a cheap, renewable natural fiber, coir (coconut fiber) as reinforcement with a biodegradable polyester amide (BAK 1095) matrix. In order to have better fiber‐matrix interaction the fibers are surface modified through alkali treatment, cyanoethylation, bleaching and vinyl grafting. The effects of different fiber surface treatments and fiber amounts on the performance of resulting bio‐composites are investigated. Among all modifications, cyanoethylated coir‐BAK composites show better tensile strength (35.50 MPa) whereas 7% methyl methacrylate grafted coir‐BAK composites show significant improvement in flexural strength (87.36 MPa). The remarkable achievement of the present investigation is that a low strength coir fiber, through optimal surface modifications, on reinforcement with BAK show an encouraging level of mechanical properties. Moreover, the elongation at break of BAK polymer is considerably reduced by the incorporation of coir fibers from nearly 400% (percent elongation of pure BAK) to 16‐24% (coir‐BAK biocomposites). SEM investigations show that surface modifications improve the fiber‐matrix adhesion. From biodegradation studies we find that after 52 days of soil burial, alkali treated and bleached coir‐BAK composites show significant weight loss. More than 70% decrease in flexural strength is observed for alkali treated coir‐BAK composites after 35 days of soil burial. The loss of weight and the decrease of flexural strength of degraded composites are more or less directly related.     

Effect of talc on the properties of polypropylene/ethylene/propylene/diene terpolymer blends

In the present study, the effect of talc content on the mechanical, thermal, and microstructural properties of the isotactic polypropylene (i‐PP) and elastomeric ethylene/propylene/diene terpolymer (EPDM) blends were investigated. In the experimental study, five different talc concentrations, 3, 6, 9, 12, and 15 wt %, were added to i‐PP/EPDM (88/12) blends to produce ternary composites. The mechanical properties such as yield and tensile strengths, elongation at break, elasticity modulus, izod impact strength for notch tip radius of 1 mm, and hardness with and without heat treatments and thermal properties, such as melt flow index (MFI), of the ternary composites have been investigated. The annealing heat treatment was carried out at 100°C for holding time of 75 h. From the tensile test results, an increased trend for the yield and tensile strengths and elasticity modulus was seen for lower talc contents, while elongation at break showed a sharp decrease with the addition of talc. In the case of MFI, talc addition decreased the MFI of i‐PP/EPDM blends. It was concluded that, taking into consideration, mechanical properties and annealing heat treatment, heat treatment has much more effect on higher yield and tensile strengths, elongation at break, elasticity modulus, impact strength, and hardness. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3033–3039, 2006     

Mechanical properties of surface‐modified ultra‐high molecular weight polyethylene fiber reinforced natural rubber composites

The mechanical properties of ultra‐high molecular weight polyethylene (UHMWPE) fibers reinforced natural rubber (NR) composites were determined, and the effects of fiber surface treatment and fiber mass fraction on the mechanical properties of the composites were investigated. Chromic acid was used to modify the UHMWPE fibers, and the results showed that the surface roughness and the oxygen‐containing groups on the surface of the fibers could be effectively increased. The NR matrix composites were prepared with as‐received and chromic acid treated UHMWPE fibers added 0–6 wt%. The treated UHMWPE fibers increased the elongation at break, tear strength, and hardness of the NR composites, especially the tensile stress at a given elongation, but reduced the tensile strength. The elongation at break increased markedly with increasing fiber mass fraction, attained maximum values at 3.0 wt%, and then decreased. The tear strength and hardness exhibited continuous increase with increasing the fiber content. Several microfibrillations between the fiber and NR matrix were observed from SEM images of the fractured surfaces of the treated UHMWPE fibers/NR composites, which meant that the interfacial adhesion strength was improved. POLYM. COMPOS., 38:1215–1220, 2017. © 2015 Society of Plastics Engineers     

A comparative study of the stress‐relaxation behavior of untreated and alkali‐treated jute fibers

In this study, we examined the effect of alkali treatment and its variables, namely, the time (2, 4, 6, or 8 h) and the concentration of alkali (1, 5, or 17.5% w/w), on the linear density, strength, and stress‐relaxation properties of jute fiber. It was demonstrated that this kind of treatment led to the creation of several voids and fiber fibrillation. Properties were measured for the alkali‐treated and dewaxed fibers. The linear density and tenacity of the fibers were reduced at higher alkali concentration and at longer dipping times. The strength increased with treatment with mild alkali and decreased with treatment with the strong alkali. A very low alkali treatment (1%) rendered low relaxation. At a 5% alkali concentration, interfibrillar matrix softening also played an important role and was prominent in the stress‐relaxation behavior. The stress‐relaxation value was much higher in the fibers treated with 17.5% NaOH compared to the dewaxed fibers; this was probably due to a loss in the fibrillar arrangement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012