Cast Polyamide Research Articles

The effect of foam and PA6 reinforcement on bending performance of 6063-T5 tube

The influence of cast polyamide (PA6) and polyvinyl chloride (PVC) foam, which have different lengths, on the bending performance of a thin-walled aluminium tube was investigated experimentally. Three-point bending test was performed to determine load carrying and energy absorbing capacity (EAC) of composite tubes. The experimental results indicated that the reinforcement of PVC foam relatively enhanced buckling displacement but its effect on load carrying capacity (LCC) and EAC is negligible. PA6 and PVC foam-reinforced composite beam shows superior bending resistance with higher buckling displacement. The improvement in bending performance of composite specimens arises from the hindering of local buckling as well as increasing bending stiffness. Accordingly, LCC and EAC increased a maximum of 3.6 and 3.9 times, respectively. The developed composite structure is promising for parts serving as support member of vehicles for which light weight is a critical design consideration.

Investigating the benefits of using circular die springs instead of rectangular die springs

AbstractDie springs with rectangular cross section (rectangular die springs) are common in the industry. However, the production of rectangular die springs is difficult, and the cost of production is high. In this study, we examined the use of die springs with circular cross section (circular die springs), which are both easier to produce and less costly, in place of rectangular ones. To this aim, the fatigue life values of both die spring with equivalent specifications were compared experimentally. The results obtained were transferred to the finite element methods software to run the simulation of the fatigue test. From the experimental results obtained, it has been observed that using circular die springs in place of rectangular die springs is always possible, provided that the springs are guided with cast polyamide guides.

Investigation of the Effect of Glass Fiber Content on the Mechanical Properties of Cast Polyamide

In this study, a series of cast polyamide-based composite materials were produced by injection molding process. In the production of composite materials, cast polyamide and short glass fiber were used as matrix and reinforcement materials, respectively. The specimens obtained from composite materials having different fiber content were tested to determine tensile and impact strength, modulus of elasticity, tensile elongation and density of composites. In addition, scanning electron microscopic studies were carried out on the fracture surfaces of impact test specimens. It was observed that mechanical properties of composites such as tensile strength and modulus of elasticity increased when the fiber volume content is increased up to 35%. However, these properties decreased at the fiber content higher than that of 35%. Moreover, tensile elongation and impact energy values were decreased when the fiber content was increased. In addition, the fiber efficiency factor increased with the increasing fiber content up to 35%, and after this point, it decreased with the increasing fiber content. On the other hand, it was observed that the fiber efficiency factor for modulus of elasticity was higher than that of the tensile strength. Consequently, it was observed that adding short glass fiber up to 35% was an effective method to improve mechanical properties of cast polyamide-based composites.

Effects of High Pressure Treatments on Polymeric Films for Flexible Food Packaging

Effects of high pressure (HP) treatments on functional and morphological properties of commercial packaging films have been investigated, to assess their suitability for use in these processes. Experimental analyses have been performed on packaging films, used to make pouches containing four different types of food simulants, after HP pasteurization and sterilization treatments at 200, 500 and 700 MPa. The investigated polymeric flexible packaging structures were single layer as well as bilayer films. Effects of treatments on structural/morphological properties (i.e. crystallinity and density) and on thermodynamic and barrier properties were addressed. Quite all the investigated films were found to be suitable for HP pasteurization, which only determined a negligible effect on the glass transition temperatures and on density of the amorphous regions of some polymeric materials, without a significant effect on functional properties of the packaging. Only bilayer structures including metalized polyethyleneterephthalate were not able to withstand processing conditions because of an extensive delamination accompanied by loss of metallization layer. Conversely, in the case of HP sterilization, combined effects of HP and relatively high temperature caused significant modifications in some of the packaging materials, even those not including a metalized film. In particular, localized delamination occurred in the case of bilayer structures made by laminating polyethyleneterephtalate with linear low density polyethylene or with polypropylene. Films obtained by laminating cast polyamide and bioriented polyamide with polypropylene displayed no evidence of delamination. In the case of films not displaying delamination, only limited changes in gas and vapour barrier properties were detected. Copyright © 2014 John Wiley & Sons, Ltd.

Evaluation of the sliding performance of polyamide, poly-oxy-methylene and their composites

Abstract The friction and wear performance of cast polyamide, unfilled poly-oxy-methylene, 10 wt.% graphite filled polyamide 6, 10 wt.% graphite filled poly-oxy-methylene, and 10 wt.% graphite plus 6% wax filled polyamide 6 sliding against stainless steel under dry sliding conditions were studied. The aim was to evaluate the tribological behavior of the above materials which enables suggesting alternative material for costly cast polyamide polymer in industrial applications. Tribological tests were carried out using a pin-on-disk arrangement at a sliding speed of 0.5–2.0 m s−1 and under applied loads of 50 to 150 N. The results showed that the friction coefficient of the tested materials decreases with the increase in applied load as well as with the decrease in sliding speed values. Furthermore, the lowest wear rate is 2.24−15 m2 N−1 for 10 wt.% graphite filled polyamide 6 composite. This suggests its use instead of cast polyamide polymer. Finally, it is concluded that the wear mechanism includes transfer film and deformation.

Buckling behavior of fiber reinforced plastic–metal hybrid-composite beam

It is known that the buckling is characterized by a sudden failure of a structural member subjected to high compressive load. In this study, the buckling behavior of the aluminum tubular beam (ATB) was analyzed using finite element (FE) method, and the reinforcing arrangements as well as its combinations were decided for the composite beams based on the FE results. Buckling and bending behaviors of thin-walled ATBs with internal cast polyamide (PA6) and external glass and carbon fiber reinforcement polymers (GFRPs and CFRPs) were investigated systematically. Experimental studies showed that the 219% increase in buckling load and 661% in bending load were obtained with reinforcements. The use of plastics and metal together as a reinforced structure yields better mechanical performance properties such as high resistance to buckling and bending loads, dimensional stability and high energy absorption capacity, including weight reduction. While the thin-walled metallic component provides required strength and stiffness, the plastic component provides the support necessary to prevent premature buckling without adding significant weight to the structure. It is thought that the combination of these materials will offer a promising new focus of attention for designers seeking more appropriate composite beams with high buckling loads beside light weight. The developed plastic–metal hybrid-composite structure is promising especially for critical parts serving as a support member of vehicles for which light weight is a critical design consideration.

Buckling behavior of fiber reinforced plastic-metal hybrid-composite beam

In this study, buckling and bending behaviors of thin-walled aluminum tubular beams (ATBs) with internal cast polyamide (PA6) and external glass and carbon fiber reinforcement polymers (GFRP and CFRP) were investigated systematically. Experimental studies showed that the increases of 3.2 times in buckling load and 7.6 times in bending load were obtained with reinforcements. The use of plastics and metal together as a reinforced structure yields better mechanical performance properties such as high resistance to buckling and bending loads, dimensional stability and high energy absorption capacity, including weight reduction. While the thin-walled metallic component provides required strength and stiffness, the plastic component provides the support necessary to prevent premature buckling without adding significant weight to the structure. It is thought that the combination of these materials will offer a promising new focus of attention for designers seeking more appropriate composite beams with high buckling loads beside light weight. The developed plastic-metal hybrid-composite structure is promising especially for critical parts serving as a support member of vehicles for which light weight is a critical design consideration.

Monomer cast polyamide 6 composites and their treatment with high‐energy electrons

AbstractAt first, the impact of selected spherically structured nanofillers made of different polar materials (carbon, silicon carbide, surface‐modified silica, 2 wt % each) on mechanical properties of monomer cast polyamide 6 (MCPA6) was examined. Only the low‐polar carbon‐based nanofiller showed an average particle size below 100 nm in the liquid phase before polymerization was initiated. With regard to neat MCPA6, mechanical properties of the composite loaded with the carbon nanoparticles like tensile strength, Young's modulus, and heat distortion temperature could be improved by 6.4%, 13.5%, and 27.5%, respectively. The efficiency of carbon as filler material for MCPA6 was also shown for carbon short‐cut fibers. A fiber content of 15% improved tensile strength from 78 to 93 MPa (19%) and Young's modulus could be doubled from 2660 MPa to nearly 5300 MPa. Regardless of the improved mechanical properties, the composites showed reduced degrees of crystallinity. Therefore, electron beam irradiation was applied to crosslink the polymer chains as an alternative to improve material properties. Crosslinking was supported by the application of a curing agent (CA). Two strategies for crosslinking experiments were tested: (1) Irradiation of CA‐containing neat MCPA6 to find the most effective dose and subsequent treatment of the composites under this special condition; (2) Optimization of the properties by irradiation of the composites itself at graduated dose values. The second way was more convenient and showed, with regard to the composites without CA, improvements of tensile strength and Young's modulus of 6% each. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Surface roughness prediction in machining of cast polyamide using neural network

This paper is about predicting the surface roughness by means of neural network approach method on machining of an engineering plastic material. The work material was an extruded PA6G cast polyamide for the machining tests. The network has 2 inputs called spindle speed and feed rate for this study. Output of the network is surface roughness (Ra). Gradient Descent Method was applied to optimize the weight parameters of neuron connections. The minimum Ra is obtained for 400 rpm and 251 cm/min as 0.8371 μm.

High conductive graphite additives for magnesium catalyzed cast PA6 polymer matrix

At this article we give a brief review about the additives effects for cast polyamide 6engineering plastics. The natural grade Magnesium catalyzed polyamide 6 has unique mechanicalproperties. Our target is to keep the mechanical and tribological properties with the development ofantistatic and ESD composite version. High conductive very effective to improve the electricalconductivity of magnezium catalized cast PA 6. Only few amount, 0,5% can result good antistaticproperty for the base matrix. Over 3% of additive the surface resistance of the material – performing107 Ω - can reach the ESD (Electrostatic Dissipative) category.

Dynamic Mechanical Tests on Magnesium Catalyzed Cast Polyamide 6 Composites Having Different Additives

Due to the effect of graphite and montmorrilonit additives, the impact strenght slightly decreases, but by the influence of softening material, the value of impact strength can be three times more than the pure PA6. It is determined that graphite can be added until 3%, montmorrilonit can be added until 6% and softening material can be added until 15% to the base matrix. These samples give basis for special characteristics examinations.

Metamaterial based telemetric strain sensing in different materials

We present telemetric sensing of surface strains on different industrial materials using split-ring-resonator based metamaterials. For wireless strain sensing, we utilize metamaterial array architectures for high sensitivity and low nonlinearity-errors in strain sensing. In this work, telemetric strain measurements in three test materials of cast polyamide, derlin and polyamide are performed by observing operating frequency shift under mechanical deformation and these data are compared with commercially-available wired strain gauges. We demonstrate that hard material (cast polyamide) showed low slope in frequency shift vs. applied load (corresponding to high Young's modulus), while soft material (polyamide) exhibited high slope (low Young's modulus).

Frictional stability of pure and internally lubricated polyamides on a meso‐scale tribotester

PurposeThe purpose of this paper is to verify, experimentally, the sliding stability of cast polyamide samples under dry sliding in contact with different steel counterface roughnesses. The effect of catalyser (sodium or magnesium) and addition of internal oil or solid lubricants is investigated and a classification for coefficients of friction in relation to the polyamide intrinsic mechanical properties is discussed.Design/methodology/approachA new tribotester is designed for meso‐scale testing according to the elastic loading region of polymers. The reliability of the tribotester is verified by preliminary determination of the stick‐slip characteristics. Sliding tests for polyamide are done at 1.15‐5.15 N normal load and 0.125‐20 mm/s sliding velocity on steel counterfaces with roughness Ra=4 and 1.6 μm.FindingsPure polyamides sliding against rough steel show severe stick‐slip. The stick‐slip motion is eliminated in contact with smooth steel counterfaces. Magnesium catalysed polyamide has weaker mechanical properties and shows lower friction with better sliding stability compared to sodium catalysed polyamide. Internal oil lubricant is more efficient in reducing coefficients of friction than internal solid lubricants are. Surface energy measurements are related to coefficients of friction, showing the effect of internal lubrication on adhesion.Research limitations/implicationsPresent test results are very specific for the present tribotester configuration and should be further compared to macro‐scale testing. The choice of tribotest conditions strongly affects the sliding performance.Originality/valuePresent tests are done on the meso‐scale, being in between traditional macro‐scale testing and nano‐scale testing. It allows for low contact pressures avoiding the effects of frictional heating and relatively large surfaces areas including the effects of long‐range polymer structure such as internal lubrication.

Friction, wear and transfer of pure and internally lubricated cast polyamides at various testing scales

Friction and wear of different cast polyamide composites (including two pure polyamides with sodium or magnesium catalysers, oil filled and solid lubricant filled polyamides) is evaluated on a small-scale and a large-scale tribotester to determine transitions in tribological behaviour and application limits. Small-scale tests are done at 50–200 N and 0.3 m/s on a cylinder-on-plate configuration (contact area <10 mm 2) and compared to sliding tests at 10–40 MPa and 0.005 m/s on a flat-on-flat configuration (contact area 22,500 mm 2) for investigating the efficiency of internal lubricants and reproducibility at different testing scales. Frictional heating and transfer are important and interfere with the sliding or lubricant mechanisms. The bulk and flash temperatures during sliding are calculated and the softening and/or melting mechanisms for the different polymers are closely related to differences in transfer, either on small-scale or large-scale tests. For pure polyamides, the magnesium catalysed polyamide (PA-Mg) has different softening behaviour compared to sodium catalysed polyamide (PA-Na) as revealed from thermal analysis and Raman spectroscopy. Therefore, sliding instabilities attributed to stick-slip for PA-Na do not occur for PA-Mg at low loads. Oil lubricated composites are not able to remove the sliding instabilities as oil supply to the sliding interface is controlled by migration effects that are restricted by deformation or softening of the polyamide matrix. A relatively thick and brittle transfer film develops when the polyamide bulk melts. Solid lubricants are able to stabilise friction and lower wear own to the formation of a thin and coherent transfer film. However, increasing the amount of lubricants induces lower mechanical properties and higher deformation. The friction coefficients for pure polyamides can be extrapolated as a function of a scaling factor. The wear behaviour of tests samples with small and large contact areas is significantly different for solid lubricated composites, with lower specific wear for large-scale samples. Transitions in lubrication mechanism due to softening and melting do not allow for extrapolation and justifies the use of large-scale tests. Only pure polyamides have identical specific wear rates on small-scale and large-scale under mild conditions.

The tribological behaviour of different engineering plastics under dry friction conditions

In this experimental study, the tribological behaviors of different polymer journal bearings are examined during the working period with steel shaft at dry friction conditions. Journal bearings are produced by different engineering plastics which are Ertacetal (POM-Delrin), Ertalyte (PETP), Ertalon 6 PLA (Cast Polyamide) and Devateks. Bearing and shaft are studied at dry friction conditions in HFN.5 journal bearing experiment apparatus. The friction force is obtained on contact surface. The friction and wear behaviors of bearings are affected by speed, load, temperature and working time. The friction coefficients between contact surfaces are determined for all materials. The wear and friction behaviors of Devateks and Ertalyte are superior to Ertacetal and Ertalon 6PLA according to test results. Ertalyte have the most wear resistantce. The lowest friction values are obtained for Devateks. It was shown that speed is the most effective parameter for friction and wear. Bearing load has less effect on friction and wear.

Softening and melting mechanisms of polyamides interfering with sliding stability under adhesive conditions

The thermal stability of polymers is a main issue when used as friction elements under dry sliding. Cast polyamide grades processed with either natrium or magnesium catalysors are slid on a small-scale and a large-scale test configuration to reveal the effect of softening or degradation on the sliding stability and to investigate possibilities for extrapolation of friction and wear rates between both testing scales. The combination of softening and afterwards transition into the glassy state is detrimental for the sliding stability of natrium catalysed polyamides, characterised by heavy noise during sliding. A transfer film formed under continuous softening also provides high friction. Melting during initial sliding is necessary for stabilisation in both friction and wear, and eventual softening of a molten film near the end of the test then not deteriorates the sliding stability. Softening of magnesium catalysed polyamides is favourable for the formation of a coherent transfer film resulting in more stable sliding than natrium catalysed polyamides. The differences in softening mechanisms of both polyamide grades is correlated to structural changes investigated by thermal analysis and Raman spectroscopy: the γ crystalline structure prevails in magnesium catalysed samples and the α crystalline structure is predominant in natrium catalysed samples. For internal oil lubricated polyamides, a time dependent degradation of the polyamide bulk deteriorates the supply of internal oil lubricant to the sliding interface, resulting in high friction and wear under overload conditions. As the degradation mechanisms during sliding are strongly correlated to the test set-up, extrapolation is only possible for friction in a limited application range, while wear rates cannot be extrapolated.

Development of orientation and mechanical properties of extrusion cast polyamide 11 films in biaxial stretching process

AbstractThe development of orientation of extrusion cast polyamide 11 films in the biaxial stretching process was studied with birefringence and wide angle X‐ray diffraction (WAXD) pole figures. White‐Spruiell biaxial orientation factors of the crystalline phase were calculated with the pole figure data. Both biaxially stretched films were developed. Planarity of hydrogen bonding planes with respect to the film surface was observed from WAXD pole figures. Mechanical properties of the films were studied. Tensile strength and elongation at break were successfully correlated with the out‐of‐plane birefringences.

Orientation and Mechanical Properties of Extrusion Cast PA 12 Films in Biaxial Stretching Process

Abstract The levels in biaxial orientations and mechanical properties of stretched extrusion cast polyamide 12 films were investigated with birefringence, wide angle X-ray diffraction (WAXD) pole figure and mechanical testing. Introduction of a pseudo-orthogonal crystalline symmetry enabled the calculation of White-Spruiell biaxial orientation factors using WAXD pole figure data. The orientation was uniaxial or biaxial depending on the stretch ratios along two principal stretching directions that are the machine direction (MD) and the transverse direction (TD). According to the WAXD pole figure patterns, planar alignments of hydrogen bonded layers were formed with respect to the film surface from most of the stretched films. Balanced stretching at higher stretch ratios enhanced the planarity. It was found that the mechanical properties (tensile strength and elongation at break) of the films had a close correlation with the out-of-plane birefringences.