Improvement In Impact Properties Research Articles

The impact properties of a polyamide 6– polytetrafluoroethylene composite

Polyamide 6 (PA6)-filled polytetrafluoroethylene (PTFE) at different compositions has been successfully prepared in a corotating twin screw extruder where PTFE acts as the polymer matrix and PA6 as the dispersed phase. The morphology and impact properties of these blends were investigated using a scanning electron microscope. The presence of PA6 particles dispersed in the PTFE continuous phase exhibited a coarse morphology. Increasing PA6 contents in the blend improved the impact properties at weak deformation. It was found that the interfacial adhesion played an important role in the creation of an interphase that was formed by the interaction between the PTFE and PA6. This induced an improvement in impact properties. In addition, the optimum impact properties were obtained when the content of PA6 is 30 vol%.

Preparation and characterization of EP/SiO2 hybrid materials containing PEG flexible chain

EP/SiO2 hybrid materials, which contained flexible chain, were prepared by epoxy resin (EP) and polyethylene glycol (PEG)-grafted polysilicic acid (PSA), which was obtained by endcapping polyethylene glycol-1000 with toluene 2,4-diisocyanate (TDI), followed by a reaction with polysilicic acid. The formation of hybrid materials was confirmed by a wide-angle X-ray diffraction (WAXD) and atomic force microscopy (AFM) analysis. Results showed that the EP/SiO2 hybrid particles were nanosized and the average size was about 20–50 nm. The mechanical properties, dynamic mechanical properties, and thermal properties were evaluated and compared with the corresponding matrix. The improvement in impact properties in hybrid materials was explained in terms of the impact fracture surface analysis by scanning electron microscope (SEM).

Improvement of impact property of natural fiber–polypropylene composite by using natural rubber and EPDM rubber

In this research, vetiver grass was used as a filler in polypropylene (PP) composite. Chemical treatment was done to modify fiber surface. Natural rubber (NR) and Ethylene Propylene Diene Monomer (EPDM) rubber at various contents were used as an impact modifier for the composites. The composites were prepared by using an injection molding. Rheological, morphological and mechanical properties of PP and PP composites with and without NR or EPDM were studied. Adding NR or EPDM to PP composites, a significant increase in the impact strength and elongation at break is observed in the PP composite with rubber content more than 20% by weight. However, the tensile strength and Young’s modulus of the PP composites decrease with increasing rubber contents. Nevertheless, the tensile strength and Young’s modulus of the composites with rubber contents up to 10% are still higher than those of PP. Moreover, comparisons between NR and EPDM rubber on the mechanical properties of the PP composites were elucidated. The PP composites with EPDM rubber show slightly higher tensile strength and impact strength than the PP composites with NR.

Optimizing the balance between impact strength and stiffness in polypropylene/elastomer blends by incorporation of a nucleating agent

AbstractIsotactic polypropylene (iPP) blends were prepared with two different thermoplastic elastomers, a triblock copolymer styrene–ethylene butylene–styrene (SEBS) and a metallocenic ethylene‐octene copolymer (EO). The mechanical properties and morphology of blends with 0–50 wt% elastomer were studied to determine the influence of the presence of the elastomer on the improvement of toughness. The addition of a nucleating agent as a third component exerted a significant effect on the overall properties. Dynamic mechanical properties, flexural modulus, and impact strength as well as morphology were studied for nucleated and nonnucleated iPP/SEBS and iPP/EO blends. The improvement of impact properties found in binary blends was accompanied by a decrease in stiffness. However, the addition of the nucleating agent provided a good balance between impact strength and stiffness. From the results, SEBS was determined to be a better impact modifier for iPP than EO. The nucleated iPP/SEBS blends demonstrated improved mechanical properties compared with both the nucleated iPP/EO blends and the nonnucleated blends. POLYM. ENG. SCI., 48:80–87, 2008. © 2007 Society of Plastics Engineers

Biodegradable Nanocomposites from Toughened Polyhydroxybutyrate and Titanate-Modified Montmorillonite Clay

Montmorillonite clay treated with neopentyl (diallyl)oxy tri(dioctyl) pyrophosphato titanate was used as a reinforcement for toughened bacterial bioplastic, Polyhydroxybutyrate (PHB) in order to develop novel biodegradable nanocomposites. The modified clay, PHB, toughening partner and specific compatibilizer were processed by extrusion followed by injection molding. Different microscopy and goniometry techniques, rheology analysis, X-ray diffraction and thermo-mechanical testing were used to characterize the nanocomposites. Results showed that the nanocomposites with 5 wt% titanate-modified clay loading exhibited about 400% improvement in impact properties and 40% reduction in modulus in comparison with virgin PHB. The novel aspect of the titanate-based modification was that the nanocomposites still maintained nearly the same impact strength value as that of toughened PHB. The diffraction patterns suggest exfoliation of the organically modified clays and this was further supported by transmission electron microscopy and melt rheological analysis. The mechanical properties of the nanocomposites were correlated with a modified Halpin-Tsai theoretical model and the predictions matched significantly with the experimental results. Toughened and compatibilized PHB showed significantly lower biodegradation rate than virgin PHB and most significantly the addition of the titanate-modified clay in the same formulation enhanced the biodegradation several fold.

Low velocity impact of combination Kevlar/carbon fiber sandwich composites

Impact, compression after impact, and tensile stiffness properties of carbon fiber and Kevlar combination sandwich composites were investigated in this study. The different samples consisted of impact-side facesheets having different combinations of carbon fiber/Kevlar and carbon fiber/hybrid. The bottom facesheets remained entirely carbon fiber to maintain the high overall flexural stiffness of the sandwich composite. The focus of this research was to determine if any improvement in impact properties existed as a result of replacing the impact-side facesheet layers of carbon fiber with Kevlar or hybrid. Impact tests were conducted on different sample types to obtain information about absorbed energy and maximum impact force. Also, compression after impact tests were conducted to determine the reduction in compressive strength when comparing impacted to non-impacted samples. The elastic moduli of carbon fiber, Kevlar, and hybrid were determined from tensile testing. This data was used to characterize the reduction in stiffness from replacing carbon fiber layers with the Kevlar or hybrid layers. The experimental data in its entirety helps define the benefits and disadvantages of replacing carbon fiber layers with Kevlar or hybrid.

Impact Strength of β-Nucleated Polypropylene

Abstract Structural transformations of semicrystalline polymers form an important field of current scientific research. The preparation of controlled supermolecular structure may lead to significant improvements in mechanical, thermal and optical properties. As for isotactic polypropylene (iPP), its properties essentially depend on its crystalline phase composition, which is due to polymorphism of iPP. Thus, the aim of this work is to analyze the influence of the β-phase content in polypropylene and of its spatial arrangement on mechanical properties, in particular on its impact strength. Commercially available isotactic polypropylene (iPP) was modified by various amounts of a specific β-nucleating agent (N, N'-dicyclohexylnaphtalene-2,6-dicarboxamide). From the prepared mixtures standard impact testing bars were injection molded. The structure of the specimens was studied by X-ray diffractometry, and impact properties were determined using Charpy impact tester. It was found that addition of the nucleator led to β-phase content increase, especially in the core region of the injection molded samples. The skin (surface layer of the samples) contained lower amount of β-phase. Furthermore, notch impact strength dramatically increased with increasing concentrations of the β-nucleating agent. The concentration of 0.03 wt.% of the nucleator can be considered a “boundary value” due to the fact that the maximum notch impact strength value was reached. With further addition of the nucleating agent the impact strength slowly decreased. Therefore it should be noted that the improvement of impact properties is not only due to the presence of β-phase, but also there are some synergy-applied factors – such as the structural heterogeneity and spatial arrangement of the β-phase in injection molded samples.

Nanocomposites based on a combination of epoxy resin, hyperbranched epoxy and a layered silicate

Epoxy/clay nanocomposites have been prepared using an diglycidyl ether of bisphenol A (DGEBA) epoxy and its blend with an epoxy functionalized hyperbranched polymer (HBP). The formation of nanocomposites was confirmed by a wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) analysis. The mechanical and dynamic mechanical properties of the nanocomposites were evaluated and compared with the corresponding matrix. The improvement in impact properties in blend and nanocomposites was explained in terms of fracture surface analysis by scanning electron microscopy (SEM).

Improvement of the mechanical properties of an HDPE/PS blend by compatibilization and incorporation of CaCO3

AbstractGenerally, recycled polymer blends exhibit solid dispersion‐like morphology with poor mechanical properties. The aim of this work was to enhance the mechanical properties of a HDPE/PS (75/25) blend, in particular the stiffness and the impact strength. In order to improve the stiffness, CaCO3 filler was incorporated. It was shown that PS and CaCO3 were separately dispersed with poor adhesion to the HDPE matrix. The incorporation of CaCO3 significantly enhanced the stiffness but lowers the impact resistance. Elastomer copolymers were incorporated in order to compensate for the embrittlement caused by the CaCO3 filler. Depending on their chemical structure, either grafted with a reactive function or ungrafted, the elastomers acted differently at the interfaces of the HDPE/PS/CaCO3 system. SEBS acts exclusively at the HDPE‐PS interface whereas SEBSgMA acts at both the HDPE‐PS and the HDPE‐CaCO3 interface. The SEBSgMA elastomer lowered the stiffening effect caused by CaCO3 and provided an insufficient increase in impact properties. One the other hand, SEBS, which concentrates its action at the HDPE‐PS interface, retained much of the stiffening effect of CaCO3 and provided a greater improvement in impact properties than SEBSgMA. In the recycled HDPE/PS (75/25) blend, the incorporation of 20 vol% CaCO3 and 4 vol% SEBS led to an increase in both impact strength (from 39 to 70 kJ/m2) and in stiffness (from 1335 to 1560 MPa). So, encouraging results were obtained, enabling us to predict a promising future for this approach to the recycling of commingled plastics.

Effects of post-weld heat treatment conditions on hardness, microstructures and impact properties of vanadium alloys

Gas-tungsten-arc (GTA) weld joints were made from V–4Cr–4Ti alloys in which oxygen levels at the weld metal ranged from 73 to 355 wppm. Both the weld metal and the base metal of the joints showed hardening after the welding. In this study, the influence of post-weld heat treatment (PWHT) on hardness, microstructure and impact properties were investigated. Change in hardness due to annealing at 673 and 973–1273 K was shown to be caused by release of contaminant hydrogen and precipitate evolution, respectively. Results indicated that the precipitation hardening increased with oxygen level. Charpy impact properties did not change significantly due to annealing at 673 K, while fine precipitation at 1073 K degraded the impact property. No improvement of impact property by PWHT is expected at low oxygen level in the weld metal. Precipitation behavior during aging and irradiation may determine the performance of V–4Cr–4Ti weld joints.

Reactive extrusion of recycled bottle waste material

AbstractThe objective of this study is to investigate the effect of reactive processing of commingled bottle waste polymer in an extruder. A variety of peroxides and monomers were tested to assess their influence on the final mechanical properties of the product. The reactive extruded polymer blends were prepared in two types of extruders: a co‐rotating twin‐screw extruder and a Buss co‐Kneader single‐screw extruder. Blends were analyzed for mechanical and thermal properties. The effectiveness of the different monomers and peroxides was evaluated in terms of improvement in impact properties. It has been found that the toughness of the polymer blend is improved by reactive processing. Depending on the amount and type of reactants, the impact strength can be improved by 220%, with a slight reduction in the modulus compared to an unmodified physical blend. The most suitable monomers were n‐butylmethacrylate (BMA), t‐butylamino ethylmethacrylate (TBAEMA) and a combination of styrene/maleic anhydride (ST/MAH). The peroxide should have a short half‐lifetime compared to the average residence time in the extruder. The most effective monomers have a high initial reactivity and low rate of evaporation at the processing conditions used. Changes in processing conditions in the extruder influence the reaction conditions and therefore the final properties of the blend. Results were interpreted in terms of residence time, melting profile and peroxide concentration.

Improvement of impact properties for Nb/MoSi2 laminate composites by the interfacial modification (II)

The thermodynamical estimation of the interfacial reaction and the impact properties of Nb/MoSi2 laminate composites containing SiC, NbSi2 or ZrO2 particles are investigated. Laminate composites, which comprise alternating layers of MoSi2 with the particle and Nb foil, were fabricated by the hot press process. It is clearly found out that the interfacial reaction of Nb/MoSi2 can be controlled by the addition of ZrO2 particle to the MoSi2 phase. The addition of ZrO2 particle increases both the impact value and the sintered density of Nb/MoSi2. The suppression of the interfacial reaction is caused by the formation of ZrSiO4 in MoSi2−ZrO2 matrix mixture.

Investigation of application of friction welding to dissimilar metal joints for electric power plants

Summary Dissimilar joints between high temperature ferritic steel and austenitic stainless steel are employed in boiler tubes of thermoelectric power plants. The friction welding method is under consideration as a new method to manufacture these dissimilar joints and fundamental investigation of this method is in progress. As indicated in the previous report, partial interfacial fracture was noted following the joint impact test; thus, in this study, improvement in impact properties was attempted by examination of the friction welding conditions. In parallel to this, evaluation of creep properties was also carried out. The effects of the friction welding conditions (upsetting pressure, heating pressure, time-lag of revolution) upon impact and creep properties were considered using dissimilar joints of modified 9Cr steel and Inconel 600. The energy absorbed by the impact test varied little, even with increased upsetting pressure, but the ratio of interfacial fracture decreased. During creep testing, the creep rupture time showed roughly similar values, irrespective of the friction welding conditions and, in addition, interfacial fracture was observed in every specimen. After observation of the creep specimen fracture surfaces, numerous minute cracks were observed in the region from the weld interface to several μm on the Inconel 600 side. Observation of element distribution of Fe and Ni near the weld interface indicated concentration peaks in the region extending from the weld interface to several μm on the Inconel 600 side for both the as-welded state and the state after creep testing. This indicates that a secondary phase was formed during friction welding and it is thought that this Fe rich secondary phase was a major factor in interfacial fracture during the creep test. A further investigation is planned into the relationship between composition analysis of the secondary phase and creep test conditions.

Recycling of PVC Packaging into Extruded Cellular Products

New packaging recovery legislation will be introduced in the UK later this year, obliging producers to recover and recycle a certain percentage of packaging waste. EVC has carried out development work to find applications for recycled post-consumer PVC bottles and PVC supermarket trays. One successful application is to use the recycled PVC packaging as the foamed core in co-extruded cellular profiles. Production-scale trials have been carried out to extrude cladding containing pulverised post-consumer PVC bottles and pulverised PVC tray material. The products had satisfactory density, foam structure, colour and surface finish. Using up to 100% bottle recylate did not affect the impact properties of the foam profile. Recycled supermarket trays actually gave an improvement in impact properties: this is attributable to the high levels of impact modifier used in tray formulations. These trials have demonstrated that PVC packaging can be recycled into foamed extrusions for use in the building industry.

Improvement of impact properties in the core of electroslag weld metal by variation in welding wire composition: Improvement of toughness properties of ESW weld metal in constructional steels (3rd report)

Summary This paper describes an investigation of improvement of the impact properties of electroslag (ESW) weld metal using different types of welding wire. The tests were conducted with six types of welding wire and three levels of welding heat input, i.e. Q = 45.6, 79.0, and 126.7 kJ/mm. The results obtained may be summarised as follows: When a heat input at any level is applied, irrespective of any difference in the welding wire used, the impact value (vE value (J), 273 K) at the centre (core) is lower than that at the periphery (rim). No major improvement of the vE value of the core is found at Q = 45.6 kJ/mm (single‐layer standard heat input conditions for 40 mm thick plate) when wires A ∼ D are used. However, it is found effective to use Ni‐containing wire F (4.18%Ni) to improve the vE value of the weld metal core at Q = 45.6 kJ/mm. The differences in the vE values of the core and rim are closely related to the size of the prior austenite (γ) grains and the different precipitation conditions of the ...

Effect of tempering on the toughness of a Cr- Mo bainitic steel

The effect of tempering on impact and fracture toughness properties of a Cr-Mo bainitic steel was studied in the quenched and stress relieved (Q & SR) condition. The lowest tempering parameter used resulted in considerable improvement in impact properties. Further tempering increased the upper shelf energy, had a minor effect on the transition temperature, and increased both the initiation fracture toughness (JIC) and the tearing modulus(T). However, the effect on JIC andT was much greater than the effect on the impact upper shelf energy. The results were discussed in light of the changes in microstructure and flow properties due to tempering.

Comparison of the effectiveness of different basic functional groups for the reactive compatibilization of polymer blends

Reactive compatibilization of immiscible polymer blends has been attracting a very considerable research interest in the past few years. While a wide variety of functionalized polymers having acidic groups are commercially available, potentially reactive polymers containing basic functional groups have rarely been developed. In this study, glycidyl methacrylate (GMA), 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate (HPMA), t-butylaminoethyl methacrylate (TBAEMA), dimethylaminoethyl methacrylate (DMAEMA), and 2-isopropenyl-2-oxazoline (IPO) were melt grafted onto a polypropylene (PP) homopolymer. The effectiveness of these functionalized PPs as compatibilizers for PP ( acrylonitrile-co- butadiene-co- acrylic acid) rubber (NBR) blends was evaluated in terms of improvement in impact properties and blend morphology. It has been found that IPO and GMA are effective in compatibilizing the PP/NBR blends, with a nine-fold improvement in impact energy over pure PP and an uncompatibilized PP/NBR blend. The other functional groups are much less effective for the blend system where carboxylic acid is the coreactive group.

Toughened thermoplastics: 1. The synthesis and use of maleate-modified poly(butylene terephthalate) in polyester/rubber blends

The synthesis of poly(butylene terephthalate), PBT, which contains approximately 3.5 mol% of maleate groups is discussed. The polymer is used in conjunction with unmodified PBT to reduce the particle size of the elastomeric phase in certain polyester/unsaturated rubber blends. This results in an improvement in impact properties compared with control samples which either contain no modified polyester, or an unreactive rubber such as polybutadiene. Model compound experiments indicate that the electron-deficient maleate groups of the modified polyester can react with unsaturated groups in ethylene-propylene-diene terpolymers via an ene mechanism.

Thermoplastic elastomers: Part 2—Effect of natural rubber/polypropylene as solid phase dispersant in polypropylene/polyethylene blends

The role of natural rubber/polypropylene (NR/PP) thermoplastic elastomer was examined as a solid phase dispersant (SPD) in the incompatible binary blend of polypropylene/low-density polyethylene (PP/LDPE). The mechanical performance of the resultant blend was compared with that of the same binary blend but in the presence of ethylene propylene diene rubber (EPDM) which was shown from previous studies to be a good SPD for this blend. The evidence presented here shows that the overall mechanical performance of the polyblend is effectively improved in the presence of NR/PP. Although the improvement in impact properties is not as high as that offered by EPDM, it is shown that the use of NR/PP as SPD offers the advantages of higher tensile strength and modulus to the blend. Both EPDM and NR/PP sensitise photo-oxidation of the polyblend, NR/PP showing a higher level of sensitisation. This difference in behaviour is attributed mainly to the difference in the level and position of the reactive unsaturated sites in the two SPD systems.

ＣＦ‐ＧＦ／ポリエステル複合材料の貫通衝撃特性に関する一考察

There have been many studies on the impact properties of carbon-fiber reinforced plastics composite materials (CFRP). Most of them are concerned with the evaluation and improvement of impact properties of CFRP, because the fracture strain of carbon-fiber (CF) is very small and its brittle nature is a matter of inquiry.In this paper, high speed impact tests using foreign projectile were performed on CF/GF hybrid composites and CFRP materials, which are composed of laminate plates, and the impact properties and fracture patterns of these materials were investigated.The results obtained showed the hybrid effectiveness of CF/GF composites, that is, the increase of impact fracture energy and the change of fracture pattern of these materials. Especially the mixing of GF materials into CF laminated plates was found to cause the enlargement of whitening area damaged by foreign projectile and thus the increase of impact fracture energy of these materials.