Toughness Enhancement of Polymers

Polymer Engineering and Science, 1981

The impact modification mechanisms of polycarbonate (PC) blended with polyethylene (PE) and blends of polyxylenol ether (PXE)/high impact polystyrene (HIPS), were studied using a volume dilation technique. With two extensometers, measurements of volume change during tensile deformation were made on the plastics. Strain rates of 2 x s-' to 4 s-' were achieved with a MTS servo-hydraulic testing machine. Analysis of both systems were supported with scanning and transmission electron microscopy. Results on the PC/PE system indicate that the impact modification mechanism is one of voiding and shear banding. The mechanism appeared to be rate sensitive: the amount of voiding increased with rate. The toughening mechanism iri the PXE/HIPS blends is identified as a combination of crazing and shear banding. The amount of shear banding that occurs is proportional to the amount of PXE in the blends. The point of craze initiation was found to be delayed by increasing strain rate. The stress for craze initiation appears to be greater than for shear banding.

Polymer, 1998

Rubber toughening of a series of blends constituted by a polypropylene (PP) matrix added with talc, and modified by ethylene-propylene (EPR) and/or ethylene-butene rubber (EBR), with different molecular weights, was investigated. The fracture toughness was measured by an elasto-plastic fracture mechanics approach, applying the methodology of the essential work of fracture, and by conventional testing. It was found that: (i) EBR has a higher toughening efficiency than EPR; and (ii) the fracture toughness increases by increasing the molecular weight of the dispersed elastomeric phase. Measurements of volume change and temperature increase in specimens stretched during tensile tests indicated that the presence of EBR in the blends reduces cavitation and crazing, and induces a large amount of shear yielding. Some difference in the microcavitation mechanisms induced by each of the two elastomers was shown by electron microscopy analysis. An explanation of this behaviour on the basis of structural changes within the matrix or at the rubber-matrix interface was sought. Dynamic thermomechanical analysis indicated that EBR has a stronger interaction than EPR with the PP matrix.

Graft-modified rubbers including maleic anhydride grafted ethylene propylene diene monomer (MAH-g-EPDM) and 49% methyl methacrylate grafted natural rubber (MMA-g-NR, i.e. MG49 rubber) were employed to toughen polypropylene (PP) and polystyrene (PS). The results showed that Charpy impact strength of the notched PP specimens and unnotched PS specimens at room temperature was improved markedly by addition of the graft-modified rubbers. Moreover, Charpy impact strength of the plastics increased with increasing graftmodified rubbers content and the incorporation of MAH-g-EPDM enhanced impact strength of the plastics more markedly than MG49. The result of thermogravimetric analysis (TGA) indicated that the addition of MAH-g-EPDM improved the thermal stability of PP, while the incorporation of MG49 reduced it. Good compatibility between the plastics and MAH-g-EPDM and saturation of EPDM could be responsible for these mechanical and thermal features. This preliminary work may also provide some information for oil-resistant modification of plastics due to the polar groups grafted onto the backbone of rubbers.

Materials Research-ibero-american Journal of Materials, 2000

The effect of incorporating (C2-C8) ethylene-octene elastomer on the mechanical properties and morphology of polypropylene copolymers has been investigated employing two types of PP copolymer, with and without nucleating agent. The results were compared to the ones presented by a commercial PP heterophase (reactor impact modified PP/EPR). The addition of the elastomer increases the toughness of the blends but reduces their stiffness. PP blends in the low elastomer content region (< 20%) show low values of the Izod impact strength and both, elastomer content and impact strength, are directly proportional to the area under the β damping peak or its maximum intensity of the elastomer. The morphology is a continuous pattern of segregate elastomeric particles with average particle size in the range of 0.27 µm to 0.39 µm. The average particle size and particle size distribution plotted in log-normal distribution curves, increases slightly with the increase in the elastomer content. The reactor modified PP heterophase has a broader particle size distribution and an average particle size of 0.56 µm, at the lower limit but inside the range for good impact performance, as observed.

mechanical properties study of polycarbonate and other thermoplastic polymer, 2021

The polymeric materials in this study underwent mechanical tests (tensile test, impact resistance and hardness), which explained the use of polymeric materials in engineering and industrial applications that need good mechanical properties compared to metals, ceramic materials and woods, and this is a good thing because it is characterized by low cost and high efficiency with application performance In this study, the polycarbonate polymer was characterized by its high tensile strength in the event of breakage, but the elongation values decreased compared with the polypropylene and polyethylene polymers, which were characterized by high elongation at the expense of tensile strength, as the polycarbonate polymer acted as a brittle material as for resistance to shock, which reflected the amount of energy absorbed From the striking hammer, the impact resistance of high-density polyethylene increased compared to other polymers, as well as the hardness whose values were close to the three types of polymers used, which confirms the importance of these types in the application used in engineering.

Materials Letters, 2015

Materials are often characterized in terms of their toughness, though more than one definition of toughness exists. Likely the most widely recognized means of defining material toughness, denoted here as τ, is by the area under the stress strain curve from a tensile test. Another important feature describing the nature of materials is that property known as brittleness, which has for a long time been much less quantitatively understood. Using a quantitative definition of brittleness provided in 2006, we demonstrate the existence of a quantitative relationship between τ and brittleness B, valid for polymers with a very wide range of chemical structures and properties, for some polymer-based composites, and also for steel and aluminum. We provide an equation relating toughness to brittleness, while for polymers we mark the determining influence of chemical structures on the properties B and τ.

In this work, naturally woven coconut sheath, a new type of reinforcement was used. Composite Laminates were prepared in a compression molding press. Tensile, flexural and impact tests were conducted as per ASTM standards, and results were compared with the glass fibre composite. Fractured specimens were analyzed with the help of scanning electron microscope images. Enhancements in mechanical properties were found with the new reinforcement. And the coconut sheath was found to be a suitable material that can reduce the utilization of non-decomposed glass fibres for polymer composite reinforcements.

2007

Since toughness is an important mechanical property, impact modifiers are widely used to enhance the impact properties of many thermoplastics. This paper focused on the effectiveness of styrene-b-ethylenealt- butylenes-b-styrene (SEBS) as an impact modifier in polypropylene (PP) and polystyrene (PS). In this study, blends of PP/SEBS and PS/SEBS were prepared using single screw extruder. The concentration of SEBS varied from 5 to 20phr of polymer for both PP and PS. After mixing and pelletizing, the dried pellets were injection molded and tested for mechanical properties. With increasing SEBS content, the increase in impact properties is more significant in PP/SEBS blends compared to PS/SEBS blends. Tensile test showed a slightly decrease of tensile strength for both blends. For PP/SEBS blends of 15phr SEBS content and above, no sample break was observed during the tensile test. A decrease in flexural modulus of both blends with increasing SEBS contents was observed, with a more sigi...

Materiale Plastice, 2010

In the recent years the utilization of polymeric materials increased due to their good mechanical properties and easy manufacturing. Starting from automotive industry up to food industry polymeric materials are used for obtaining components by molding or by machining. Taking into account the wide range of applications, it is important to know the mechanical behaviour of these materials in different loading conditions. Accordingly, this paper presents an experimental study to determine mechanical properties on 11 commercial polymeric materials. Tensile and shear static tests and impact tests on notched and un-notched specimens were performed. The results are presented comparatively, and two new parameters were introduced for material selection purpose.

Taylor and Francis, 2022

The barrier and mechanical properties are the primary requirement of a rubber for tyre inner liner application that can be fulfilled by incorporation of organically modified clay (OMC) into rubber matrix. In this work, functional rubber composites with an improved gas barrier performance were prepared using bromobutyl rubber (BIIR) and natural rubber (NR) as the elastomer phases, and OMC and carbon black (CB) as the functional fillers by employing standard solid-state mixing and vulcanization methods. CB was partially replaced by OMC to achieve adequate barrier and mechanical properties. OMC modified composite showed ~35% improvement in the barrier properties as compared to the control compound (60 phr carbon black, 10 phr NR and 90 phr of BIIR loaded rubber compound). The dispersion of the nano clays were investigated by transmission electron microscopic (TEM), scanning electron microscopic (SEM) and X-ray diffraction (XRD) studies. The XRD study revealed that higher d-spacing and crystalinity of the nano clay composites ease the exfoliation tendency. The mechanical properties of the clay filled nano composites, such as hardness tensile strength, modulus and air barrier properties were superior to the control compound. The developed BIIR/nanoclay composites with improved barrier properties prepared by conventional mixing method in line with common industrial practice can be used in rubber products such as tire inner liner.