Abstract:Polypropylene (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 proc… Show more
“…The decrease is somewhat more pronounced in the case of the wood and CF composites since the sizing of the glass fibers is relatively effective and adhesion is also reasonably good without coupling. 36 The addition of MAPP increases tensile strength considerably showing that coupling is effective; interfacial adhesion and thus the load-bearing capacity of the fibers increase considerably upon coupling. We can deduce from these results that interfacial adhesion and coupling influence the failure process and thus possibly also fracture resistance.Figure 2.Dependence of the tensile strength of PP/GF hybrid composites on PVA fiber content.…”
Section: Resultsmentioning
confidence: 99%
“…The addition of the PET fibers does not change stiffness practically at !novel concept of using synthetic fibers for the impact modification of PP could be used with all kinds of reinforcing fibers and PET. 36,37 Although PVA fibers were also effective in two-component PP composites, 35 no proof is so far available that they improve impact resistance in the presence of reinforcing fibers as well. The traditional approach of using an elastomer and a filler or fiber worked with inorganic fillers and glass or carbon fibers, but proved to be completely inefficient for wood composites.…”
Section: Introductionmentioning
confidence: 99%
“…In order to overcome the deficiencies of the traditional approach, that is, the use of elastomers and fillers or fibers, hybrid materials containing synthetic fibers were prepared recently. 34 Synthetic polymer fibers, poly(ethylene terephthalate), PET and poly(vinyl alcohol), PVA, increased the impact resistance of PP when they were used as a single additive, 35 and the PET fibers proved efficient impact modifiers in hybrid composites reinforced either with traditional glass or carbon fibers, 36 or various natural fibers like flax, sugar palm fiber or wood flour as well. 37 In these hybrid composites, the stiffness of the material was determined by the amount of the stiff, reinforcing fibers, while impact resistance by that of the synthetic fiber.…”
Polypropylene (PP) hybrid composites were prepared by the combination of three reinforcing (carbon, glass, and wood) and a synthetic (PVA) fiber. 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 obtained prove that the novel concept of using synthetic fibers for impact modification can be applied successfully also with PVA fibers. The extent of improvement in impact strength depends on fiber type and content, but also on interfacial adhesion which strongly influences the local deformation processes occurring around the fibers during fracture. Both the reinforcing and the synthetic fibers take part in these processes and contribute to energy consumption. Debonding and the subsequent plastic deformation of the matrix consumes energy the most efficiently, but the fracture of the PVA fibers also requires energy; thus, PVA fibers improve impact resistance both at poor and good adhesion. This approach allows the design of materials for structural applications; the combination of a stiffness of 4–6 GPa and an impact resistance of 20–25 kJ/m2 exceeds the properties of most PP composites available on the market.
“…The decrease is somewhat more pronounced in the case of the wood and CF composites since the sizing of the glass fibers is relatively effective and adhesion is also reasonably good without coupling. 36 The addition of MAPP increases tensile strength considerably showing that coupling is effective; interfacial adhesion and thus the load-bearing capacity of the fibers increase considerably upon coupling. We can deduce from these results that interfacial adhesion and coupling influence the failure process and thus possibly also fracture resistance.Figure 2.Dependence of the tensile strength of PP/GF hybrid composites on PVA fiber content.…”
Section: Resultsmentioning
confidence: 99%
“…The addition of the PET fibers does not change stiffness practically at !novel concept of using synthetic fibers for the impact modification of PP could be used with all kinds of reinforcing fibers and PET. 36,37 Although PVA fibers were also effective in two-component PP composites, 35 no proof is so far available that they improve impact resistance in the presence of reinforcing fibers as well. The traditional approach of using an elastomer and a filler or fiber worked with inorganic fillers and glass or carbon fibers, but proved to be completely inefficient for wood composites.…”
Section: Introductionmentioning
confidence: 99%
“…In order to overcome the deficiencies of the traditional approach, that is, the use of elastomers and fillers or fibers, hybrid materials containing synthetic fibers were prepared recently. 34 Synthetic polymer fibers, poly(ethylene terephthalate), PET and poly(vinyl alcohol), PVA, increased the impact resistance of PP when they were used as a single additive, 35 and the PET fibers proved efficient impact modifiers in hybrid composites reinforced either with traditional glass or carbon fibers, 36 or various natural fibers like flax, sugar palm fiber or wood flour as well. 37 In these hybrid composites, the stiffness of the material was determined by the amount of the stiff, reinforcing fibers, while impact resistance by that of the synthetic fiber.…”
Polypropylene (PP) hybrid composites were prepared by the combination of three reinforcing (carbon, glass, and wood) and a synthetic (PVA) fiber. 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 obtained prove that the novel concept of using synthetic fibers for impact modification can be applied successfully also with PVA fibers. The extent of improvement in impact strength depends on fiber type and content, but also on interfacial adhesion which strongly influences the local deformation processes occurring around the fibers during fracture. Both the reinforcing and the synthetic fibers take part in these processes and contribute to energy consumption. Debonding and the subsequent plastic deformation of the matrix consumes energy the most efficiently, but the fracture of the PVA fibers also requires energy; thus, PVA fibers improve impact resistance both at poor and good adhesion. This approach allows the design of materials for structural applications; the combination of a stiffness of 4–6 GPa and an impact resistance of 20–25 kJ/m2 exceeds the properties of most PP composites available on the market.
“…Cavitation and the fracture of the natural reinforcement resulted in the limited impact resistance [24], meaning that a different solution had to be found. The approach that proved to be very successful was the introduction of organic fibers, mainly poly(ethylene terephthalate) (PET) [25] or poly(vinyl alcohol) (PVA), into a PP matrix reinforced with traditional fibers (glass, carbon) [25]. Very large stiffness (6-8 GPa) and impact resistance (15-20 kJ/m 2 ) could be achieved by the approach even in the case of natural reinforcements [25].…”
Hybrid composites were prepared from a PP homopolymer, talc and PVA fibers by twin-screw extrusion and injection molding. Talc was added to improve stiffness, while the fibers serve to increase impact resistance. Mechanical properties were characterized by tensile and impact testing, while structure was studied by SEM and optical microscopy. The results showed that talc has a strong nucleating effect in the PP used in spite of the fact that the grade contained a nucleating agent inherently. PVA also nucleated the PP slightly, with trans-crystallization occurring around the fibers. The effect of the two components was independent of each other on lamella thickness, but crystallinity decreased with increasing PVA content in the hybrid composites. The results clearly showed that crystalline structure changes considerably upon the addition of the two components, both lamella thickness and crystallinity increasing. However, somewhat contradictorily, the effect of these changes on the mechanical properties of the composites is small. Model calculations have shown that stiffness increases by about 0.5 GPa due to nucleation, while moduli as large as 7 GPa are reached by the addition of talc. Impact resistance is completely independent of lamella thickness or crystallinity; this property is determined mainly by local deformation processes initiated by the PVA fibers. Dispersed structure and the direct effect of the additive determine properties in the hybrid composites studied, and the role of crystalline structure is of secondary importance.
Polypropylene (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
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