Enhanced Impact Strength Research Articles

Effect of the content of ethyl cellulose-rubber blend on physicochemical properties of adhesive compositions

Results of comprehensive systematic physicochemical studies of the blends of ethyl cellulose and butadiene-acrylonitrile rubbers are reported. It is shown that the addition of butadiene-acrylonitrile rubbers to ethyl cellulose results in the formation of ethyl cellulose-butadiene-acrylonitrile rubber thermoelastoplastic complexes due to the elastification of the thermoplastic polymorphous structure of ethyl cellulose with enhanced impact strength and heat resistance.

Effect of acid and TETA modification on mechanical properties of MWCNTs/epoxy composites

Acid treatment and triethylene-tetramine (TETA) modification of multi-walled carbon nanotubes (MWCNTs) purposing to attain better dispersibility and stronger interfacial bonding between MWCNTs and epoxy matrix have been carried out in this paper. The epoxy and MWCNTs/epoxy composites were produced by cast molding method. Stress–strain curves show that TETA-MWCNTs/epoxy hold the greatest toughness of all samples with 0.5 wt.% nanoparticles. The Young’s modulus of TETA-MWCNTs/epoxy has a significant increase about 38% compared to the neat epoxy, while the Young’s modulus of unmodified MWCNTs/epoxy or acid-modified MWCNTs/epoxy has a bit of decrease. Tensile and impact strength tests reflect that TETA-MWCNTs reinforced epoxy composites have an obvious improvement of tensile strength about 30% and an enhancement of impact strength over 34% compared to the pure epoxy composites with only 0.5 wt.% loading of TETA-MWCNTs. Scanning electron microscopy images of fractured surface of MWCNTs/epoxy indicate homogeneous dispersibility of TETA-MWCNTs and strong interfacial adhesion between the TETA-MWCNTs and the epoxy in the MWCNTs/epoxy composite.

Properties and Structure of Polypropylene/ Polyethylene-Octene Elastomer/Nano CaCO 3 Composites

Polypropylene (PP)-based nanocomposites were developed by the incorporation of a novel nano-sized precipitated calcium carbonate (NPCC) nanoparticles and polyethylene—octene elastomer (POE). The NPCC filler loading selected were 10 and 15wt.% while the POE contents were varied between 0 and 30wt.%. A slight decrease in the tensile strength of the PP nanocomposites was observed with increasing NPCC content. Results of impact strength indicated that the NPCC filler imparted some toughening effects on the PP and PP/POE blends. Maximum impact strength enhancement was achieved for the PP when blended with 30wt.% POE and filled with 15wt.% NPCC. However, the essential property balance between toughness and stiffness was still lacking in the nanocomposites developed. Differential Scanning Calorimeter results showed that NPCC acted as a nucleating agent for PP, increasing the crystallization temperature of PP by approximately 9°C.

Effects of electron radiation and compatibilizers on impact strength of composites of recycled polymers

The aim of this article was to show the effects of an electron radiation dose and compatibilizer on the Charpy impact strength ( σ c) and tensile-impact strength ( σ t) of composites made of blends of the following recycled polymers: low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and poly(ethylene terephthalate) (PET). The purpose of both applying the high-energy electron radiation with doses of up to 300 kGy and adding a compatibilizer to the blends was to enhance impact strength of the studied composites and, at the same time, to investigate the possibility of using this method in the processing of recycling plastic waste. Styrene–ethylene/butylene–styrene elastomer grafted with maleic anhydride (SEBS- g-MA) and trimethylol propane trimethacrylate (TMPTA) were used as the compatibilizers, added at 10 and 1 wt %, respectively. It was found that, under the influence of SEBS- g-MA, the values of σ c and σ t for the studied composites increased by over three and almost five times, respectively. On the other hand, the electron radiation and TMPTA had no noticeable effect on these quantities, which might be due to the protective properties of aromatic rings included in the macromolecules of PS and PET. The study also showed that the inclusion of SEBS- g-MA enabled achievement of satisfactory impact strength of composites made of recycled polyolefins, PS and PET, while it was not necessary to use the electron radiation and TMPTA.

Study on morphological, rheological, and mechanical properties of PP/SEBS‐MA/SGF hybrid composites

AbstractHybrid composite samples composed of polypropylene as matrix, 20% short glass fibers (SGF) as reinforcement and varying amount of maleic anhydride (MA) grafted SEBS as compatibilizer and impact modifier were prepared by melt mixing in a modular twin screw extruder. The SEM examination performed on cryogenically fractured surfaces of hybrid samples showed a three‐phase type morphology in which SGF and rubber phase finely distributed in the PP matrix. SEM results also revealed that in the hybrid samples containing SEBS‐MA, the surface of the SGF are coated with a thin layer of SEBS‐MA, indicating a strong adhesion between SGF and matrix materials. The results of rheological studies showed nearly equal viscosity for compatible and incompatible hybrid samples. Tensile yield strength enhanced with increasing rubber content up to 10% above which it decreased and highest impact strength enhancement was obtained for sample containing 20% rubber. The impact strength of composites was found to be increased with increasing the SGF content. In final, it was shown that a good balance between stiffness and toughness could be achieved by adjusting the SGF and rubber content in this ternary system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2704–2710, 2007

On enhanced impact strength of calcium carbonate-reinforced high-density polyethylene composites

The micromechanism of plastic deformation during impact loading of 20% calcium carbonate-reinforced polyethylene micrometric composite is investigated through scanning electron microscopy and atomic force microscopy and the behavior compared with the un-reinforced polyethylene under identical conditions of processing. The impact strength of composites is linked to structural studies by X-ray diffraction and atomic force microscopy observations. The adoption of calcium carbonate in polyethylene has two primary effects: the reinforcement and the nucleating effect. The reinforcement effect increases the bulk crystallinity and modulus, while the nucleating effect decreases the spherulite size. The addition of calcium carbonate to polyethylene increases impact strength in the investigated temperature range of −40 to +70 °C and alters the primary micromechanism of plastic deformation from crazing–tearing and brittle behavior in neat polyethylene to particle-induced cavitation and fibrillation in the composite.

On the strength enhancement under impact loading of square tubes made from rate insensitive metals

This paper presents a study on the strength enhancement of a model structure (square tubes) under impact loading. It aims at the understanding of the impact strength enhancement in a successive folding process of some cellular structures (aluminium powder metallurgy foams and honeycombs). Compressive crushing tests of square tubes made of brass were performed under static and dynamic loading. A significant enhancement (up to 40%) of peak loads was found in successive folding cycles. Static and dynamic compressive tests on specimens cut from these brass tubes were also performed to prove the rate insensitivity of the brass itself, demonstrating the increase of the crush resistance of the brass square tube in successive folding is not caused by the rate sensitivity of the base material. Numerical simulations of crushing tests under static and impact loading were performed to obtain local information such as the time histories of stress and strain fields everywhere in the tube, which are difficult to measure under impact loading. The simulations indicated that the regions around the four edges of a square tube remain straight even when the flat plates between two adjacent edges are already strongly bent. Furthermore, the straight edge line zones support about 80% of the global crushing load. Therefore, buckling of these edge-areas determines the peak loads in successive folding cycles. Theoretical analysis of an idealized square box column model leads to a reasonable prediction of successive crushing peak loads in both static and dynamic cases. Under impact loading, the strain reached in these edge-areas is higher because of inertia. Strain hardening of the base material is the reason for the increase of crushing forces. Post-mortem micro-hardness measurements confirmed this theory and a good agreement between experiment and simulation was found.

On the use of extruders as chemical reactors

AbstractComposites of polyamide‐6 (PA‐6) and poly(butadiene acrylonitrile) (PBAN), varying in the quantity of the elastomer and the content of its nitrile groups, were examined during extrusion in a 45‐mm extruder at 225 ± 2°C and with a shear rate over 450 s−1. It was established that these two incompatible polymers can be mixed and the blends display solubility in formic acid. This fact is explained by chemical transformation of the nitrile groups followed by chemical interaction between the polyamide and elastomer components. As a result, graft copolymers were most probably formed. The reaction proceeds easily if the PA‐6 contains water. The extrusion leads to improved compatibility of the polymers and enhanced impact strength of the extrudates. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 871–877, 2004

Microstructure and properties of poly(butylene terephthalate) based nanocomposites

Three different polymer/layered silicate nanocomposites based on poly(butylene terephthalate), PBT, were prepared via melt intercalation; PBT/organoclay nanocomposite, poly(ethyleneco-vinyl acetate) (EVA)/organoclay nanocomposite, and PBT/EVA/organoclay ternary nanocomposite. For ternary composites, maleic anhydride grafted EVA (EVA-g-MAH) was used instead of EVA. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the microstructure of the nanocomposites. The results show that nanocomposite formation requires sufficiently hydrophobic organically modified layered silicates, as well as the presence of polar interactions between the silicate and polymer. It was found that the PBT/EVA/organoclay ternary nanocomposite showed much enhanced impact strength in comparison to PBT without severely sacrificing the tensile strength of PBT.

Fracture behavior of rubber‐modified injection molded poly(butylene terephthalate) with and without short glass fiber reinforcement

AbstractFracture behavior of poly(butylene terephthalate) (PBT) and its rubber‐toughened (RT) 10 wt %) grades; ethylene‐co‐glycidyl methacrylate‐co‐methacrylate terpolymer‐toughened poly(butylene terephthalate) PBT/AX8900 (90/10), and Paraloid acrylic‐based rubber‐toughened poly(butylene terephthalate) PBT/EX2314 (90/10) was investigated using the fracture mechanics approach. The effects of controlling parameters such as type of impact modifier and deformation rate on fracture behavior of PBT and RT‐PBT were investigated. Fracture tests were carried out on notched compact tension (CT) specimens. Fracture toughness, Kc, and fracture energy, Gc, of PBT decreased as the test speed increased from 1 to 500 mm/min. An opposite trend was observed in PBT/AX8900 and PBT/EXL2314. The fracture properties of 30 wt % short glass fiber‐reinforced PBT (SGF‐PBT) and 10 wt % impact‐modified PBT composite (SGF‐RT‐PBT) were also studied. Incorporation of SGF into PBT has profoundly increased the fracture properties both at high and low speed. However, inclusion of 10 wt % of AX8900 into the reinforced PBT (PBT/AX8900/SGF) (60/10/30) adversely affected the fracture properties. EXL2314, on the other hand, showed a different effect, especially at high testing speed. Both types of impact modifiers were able to retain the flexural strength and flexural modulus of PBT. However, PBT/EXL2314 showed a better retention of flexural properties than PBT/AX8900. Incorporation of SGF in the EXL2314‐toughened PBT, i.e., PBT/EXL2314/SGF (60/10/30) also gave a better balance of flexural properties compared to PBT/AX8900/SGF (60/10/30). Both PBT/AX8900 and PBT/EXL2314 showed enhancement of impact strength on the unnotched specimens. The failure modes of CT and impact specimens of PBT, RT‐PBTs, and SGF‐RT‐PBTs were assessed using a scanning electron microscope (SEM). Brittle failure was observed for CT specimens of PBT at high testing speed, while incorporation of the impact modifier AX8900 and EXL2314 resulted in a shift of failure mode from brittle to ductile. SEM micrographs also revealed extensive fiber pull out in SGF‐PBT and SGF‐RT‐PBT. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1233–1244, 2002; DOI 10.1002/app.10446

Effects of Prestrainning on the Impact Response and Twinning Structure of 304L Stainless Steel

An investigation has been made into the effects of prestraining on the impact response and twinning structure of 304L stainless steel by means of a split Hopkinson bar and TEM metallography. Annealed 304L stainless steel was pre-deformed at prestrains of 0.15 and 0.3 using a Saginomiya 100 metal forming machine, providing specimens with different microstructural parameters and mechanical properties. Cylindrical specimens were machined from the pre-deformed material and tested at room temperature at strain rates of 10−3, 8×102, 2.3×103 and 4.8×103 s−1, with the true strains varying from 0.1 to 0.3. The results indicate that the overall stress-strain response was strongly dependent on applied strain rate and prestrain level. Flow stress increased with strain and strain rate for each prestrain condition. The higher prestrain specimen was generally stronger because of the different initial microstructure and degree of work hardening. Strain-rate sensitivity and activation volume varied with prestrain and work hardening stress (σ−σy). Increased prestrain and work hardening stress resulted in increased strain-rate sensitivity, but the inverse was observed for activation volume. TEM thin foil observation revealed deformation twinning was operative in 304L stainless steel over a broad strain and strain rate range, and can combine with prestrain effects for different work hardening characteristics and impact strength enhancement. Twin density was observed to increase with prestrain and work hardening stress.

Core–shell latex particles consisting of polysiloxane–poly(styrene-methyl methacrylate-acrylic acid): Preparation and pore generation

Latexes with a poly(dimethyl siloxane) core and a poly(styrene-methyl methacrylate-acrylic acid) [poly(St-MMA-AA)] shell have been prepared in two steps in order to generate particles that have a core with a very low glass transition temperature. In the first step, poly(dimethyl siloxane) particles were obtained via the ring-opening emulsion polymerization of octamethyl tetracyclosiloxane (D4). The polymerization was carried out using either an anionic or a cationic catalyst. In the first case, sodium hydroxide was used as catalyst and sodium dodecylbenzene sulfonate as surfactant, while in the second, the alkylbenzene sulfonic acid (ABSA) was used both as catalyst and surfactant. Using a PD4 latex as seed, a seeded emulsion polymerization of St-MMA-AA was conducted to obtain PD4–P(St-MMA-AA) core–shell particles. Numerous recipes were attempted and the most successful were those in which the seed was prepared with a cationic catalyst (ABSA) at a relatively low temperature (75°C). The core–shell structure of the particles was identified by transmission electron microscopy, but also via wetting angle, water absorption, and Tg measurements. Finally, pores were generated in the core–shell particles via an alkali–acid treatment. Because PD4 has a very low glass transition temperature, it cannot be easily handled. However, protected by a shell, it could be used as a constituent of composite materials with enhanced impact strength, even at very low temperatures. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2235–2245, 1999

Core-shell latex particles consisting of polysiloxane-poly(styrene-methyl methacrylate-acrylic acid): Preparation and pore generation

Latexes with a poly(dimethyl siloxane) core and a poly(styrene-methyl methacrylate-acrylic acid) [poly(St-MMA-AA)] shell have been prepared in two steps in order to generate particles that have a core with a very low glass transition temperature. In the first step, poly(dimethyl siloxane) particles were obtained via the ring-opening emulsion polymerization of octamethyl tetracyclosiloxane (D4). The polymerization was carried out using either an anionic or a cationic catalyst. In the first case, sodium hydroxide was used as catalyst and sodium dodecylbenzene sulfonate as surfactant, while in the second, the alkylbenzene sulfonic acid (ABSA) was used both as catalyst and surfactant. Using a PD4 latex as seed, a seeded emulsion polymerization of St-MMA-AA was conducted to obtain PD4–P(St-MMA-AA) core–shell particles. Numerous recipes were attempted and the most successful were those in which the seed was prepared with a cationic catalyst (ABSA) at a relatively low temperature (75°C). The core–shell structure of the particles was identified by transmission electron microscopy, but also via wetting angle, water absorption, and Tg measurements. Finally, pores were generated in the core–shell particles via an alkali–acid treatment. Because PD4 has a very low glass transition temperature, it cannot be easily handled. However, protected by a shell, it could be used as a constituent of composite materials with enhanced impact strength, even at very low temperatures. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2235–2245, 1999

Structure and Properties of Injection Moldings of β-Crystal Nucleator-added PP

Abstract Aiming at a synergism of improvements of impact strength of polypropylene by the addition of β-crystal nucleator and of its rigidity by the filling of particulate, the addition of the nucleator to particulate-filled polypropylenes has been studied. 0 to 3000 ppm of γ-quinacridone (GQ) which is a β-crystal nucleator was added to homo isotactic polypropylenes (PP) filled with 0 to 30 wt-% of talc (TC) which shows an α-crystal nucleating effect, of mica (MC), or of glass flake (GF), last two of which show β-crystal nucleating effects. Flexural and Izod impact test specimens were injection-molded from the PPs under constant molding conditions and the structure and properties have been investigated. The β-crystal content is reduced by the filling of particulates. The degree of the reduction is in the order of TC >MC >GF, which agrees with that of the crystallization temperature. The flexural modulus decreases slightly with increasing GQ content and increases with increases in particulate contents. The increase is in the order of MC > TC > GF, which agrees with that of the aspect ratio. The enhancing effect of the Izod impact strength by the addition of GQ decreases with increasing particulate contents and diminishes at contents above 10 wt-%. Particulates deteriorate the enhanced impact strength of β-PP. Thus the expected synergism could not be obtained enough.

Compatibility enhancement of ABS/polycarbonate blends

The effects of blend composition, melt viscosity of poly(acrylonitrile-butadiene-styrene) (ABS), and compatibilizing effect of poly(methyl methacrylate) (PMMA) on mechanical properties of ABS/polycarbonate (PC) blends at ABS-rich compositions were studied. As the content of PC was increased, impact strength and Vicat softening temperature (VST) were increased. As the melt viscosity of ABS was increased near to that of PC, finer distribution of dispersed PC phase and consequent enhanced impact strength and VST were observed. The compatibilizing effect of PMMA can be ascer-tained from the enhanced properties of ¼-inch notch impact strength, VST, tensilestrength, and the morphology observed by a scanning electron microscope. The improved adhesion of the ABS/PC interface by PMMA changed the fracture mechanism and reduced the notch sensitivity of blends. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 533–542, 1998

Structures and Mechanical Properties of Microcellular Foamed Polyvinyl Chloride

In this paper, microcellular foamed polyvinyl chloride (PVC) with unique cell morphology and mechanical properties is characterised. Microcellular foamed structures were produced in PVC by first saturating the polymer with C02 under high pressure followed by rapidly decreasing the solubility of C02 in the samples. The void fraction of the microcellular foamed PVC was controlled by tailoring the foaming temperature and foaming time. Tensile and impact tests were performed on the foamed PVC to investigate the dependence of these properties on the void fraction of foamed specimens. The notched Izod impact strength of microcellular foamed PVC increased as the void fraction increased. When the void fraction was 80%, the notched Izod impact strength of foamed PVC was four times as high as that of the unfoamed PVC. However, the tensile strength and modulus decreased as the void fraction increased. Experimental results indicate that the relative density of microcellular foamed PVC should be determined in consideration of the material saving, weight reduction, enhanced impact strength and reduced tensile strength and modulus to optimise performance of the foamed materials.

Mechanism of enhanced impact strength of poly(vinyl chloride) modified by acrylic graft copolymer

Mechanism of enhanced impact strength of poly(vinyl chloride) modified by acrylic graft copolymer

Mechanism of enhanced impact strength of poly(vinyl chloride) modified by acrylic graft copolymer

The mechanism of enhanced PVC impact strength of poly(vinyl chloride) modified by an acrylic graft copolymer was studied by the three-point bending test on a U-notched bar. In the mechanism, the void formation from the modifier released the constrained strain. The release suppresses the stress below the fibril strength in the material; consequently, stable deformation can develop over a large area and, thus, the impact strength of PVC modified by the acrylic graft copolymer is improved. © 1996 John Wiley & Sons, Inc.

Rheologische Eigenschaften von mit Holzmehl gefülltem Polypropylen

The rheological properties of polypropene containing various amounts of woodflour, of polypropene elastified with 1,4-poly-cis-isoprene and of the ternary composite material based on polypropene, elastified polypropene and wood-flour were studied. The flow curves (viscosity curves) of the melts were obtained by means of a capillary viscosimeter, and the melt flow index, the consistency index and the melt flow rate through the capillary were determined from these curves. A pseudo-plastic nature of the flow was established, the compositions containing 7 to 15 wt.-% of elastomer showing the best flowability. The activation energy of viscous flow was calculated from the shear viscosity using the Frenkel-Eyring equation. The elastified polypropene was characterized by an enhanced impact strength, timber outlook and higher outdoor durability, as compared to elastomer-free, wood-flour-filled polypropene

Chemical structure and mechanical properties of a number of aromatic polyketones

Limiting strength and relaxation properties and heat stability were studied of a number of aromatic polyketones with various chemical structures. It was found that these polymers can be easily shaped into monolithic products with enhanced impact strength and good bending strength. The effect of chemical structure on thermal stability was investigated, as characterized by relaxation mechanical measurements in a broad strain and temperature range.