Internal Lubricant Research Articles

Mechanical hysteresis, interface and filler–filler structural breakdowns in ethylene vinyl acetate organoclay composites internally lubricated via radiolytically degraded PTFE microparticles

ABSTRACTInclusion of two or more distinct fillers (hybrid fillers) in a matrix is envisaged to entail synergetic advantages. This study reports synthesis and property evaluation of a novel hybrid filler‐based polymer composite containing two types of fillers with distinct attributes namely mechanical reinforcement and internal lubrication. Poly(tetrafluoroethylene) micro‐particles (PTFEMP) were synthesized via radiolytic‐mechanical degradation and used as an internal lubricant for organoclay (OC) reinforced ethylene vinyl acetate (EVA) matrix. Mechanical hysteresis, nonlinear and linear small amplitude oscillatory shear rheology, morphology, small angle X‐ray scattering (SAXS), dynamic coefficient of friction (DCoF), surface wetting and thermoxidative stability of binary and ternary composites were investigated. In EVA/OC composites, PTFEMP acted as an internal lubricant and reduced DCoF in a volume fraction‐dependent fashion. OC and PTFEMP both increased the mechanical hysteresis of EVA; though the magnitude of hysteresis was much less in PTFEMP. Intriguingly, PTFEMP reduced mechanical hysteresis of EVA/OC composites that is work done during loading and unloading stress–strain cycles was considerably reduced with the inclusion of PTFEMP in EVA/OC composites. SAXS results revealed mass fractals and the presence of an interfacial layer in EVA/OC composites but not in EVA/PTFEMP composites. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 509–519

Results of modeling the secondary kinematics of the piston in the cylinder of a high-speed diesel engine

The relevance of the investigation of the processes of secondary kinematics of the piston in the internal combustion engine’s cylinder is due to their strong influence on such indicators as mechanical losses, wear, noise, vibration, oil consumption, and their insufficient knowledge concerning high-speed piston engines. The purpose of the research was an assessment of the influence on the character of the secondary kinematics of the piston of the high-speed internal combustion engine design factors, operating conditions and lubricant and on this basis finding the ways to improve the lubrication and friction conditions in coupling of the «cylinder-piston skirt». The tasks to be performed to achieve the research goal were in an identification the most significant parameters of the construction on the piston's secondary kinematics, mode of operation and properties of the lubricant; obtaining diagrams of the piston's secondary kinematics depending on the change in the values of the influencing factors, as well as the analysis of the obtained results and the development of recommendations aimed at reducing friction and wear in the piston-cylinder-unit. For the subject of the research the piston of the high-speed diesel engine 1CH 8,5/8,0, having a barrel-shaped profile of the piston skirt in the serial production and a negative dezaksial of piston pin, was chosen. The research method is mathematical modeling using the calculation program PISTON-DHT. Discussion of the obtained results made it possible to reveal the two most influential parameters on the character of the secondary kinematics of the piston: the dezaksial of piston pin and piston skirt profile. The variation of the sign and the values of these indicators were established an expedience to switch from a negative one to the positive dezaxial and an application of rational profile of the piston skirt. For the two most dynamically loaded strokes of the working cycle «Compression» and «Expansion», the dominance of the piston movement in the position of the scraper relative to the adjacent side of the cylinder wall was highlighted. The generalized recommendations aimed at eliminating the dominance of this undesirable situation can be taken into account and used in the design and completion of high-speed internal combustion engines pistons in order to minimize mechanical losses and wear.

Roll Compaction/Dry Granulation of Dibasic Calcium Phosphate Anhydrous—Does the Morphology of the Raw Material Influence the Tabletability of Dry Granules?

The influence of raw material particle morphology on the tabletabilty of dry granules was investigated. Therefore, dibasic calcium phosphate anhydrous was used as a model material. One milled grade, 2 agglomerated grades with different porosities, and a functionalized structure, that is, an agglomerate formed by very small primary particles, were included. Particle size, density, and specific surface area of raw materials were measured. The starting materials and 2 fractions of dry granules were compressed to tablets. The tabletability of granules was compared to that of the powders and the influence of specific compaction force, granule size, and lubrication on tablet tensile strength was evaluated. All materials showed a loss in tabletability induced by a previous compaction step but to a varying extent. Only in case of the functionalized calcium phosphate morphology, this effect depended on the specific compaction force. In contrast to the other materials, the tabletability of functionalized calcium phosphate was influenced by the granule size. This effect was not related to an overlubrication as internal and external lubrication resulted in similar tensile strengths. A clear influence of the particle morphology on tablet strength was demonstrated by the study. The functionalized structure showed aspects of a more plastic deformation behavior. The functionalized dibasic calcium phosphate and the more porous agglomerate performed as potential filler/binder in the field of roll compaction/dry granulation.

The roles of rigid particles on the friction and wear behavior of short carbon fiber reinforced PBT hybrid materials in the absence of solid lubricants

Abstract Polymeric materials filled with micro-sized short carbon fiber (SCF) and various internal lubricants, i.e. graphite and PTFE etc., have been proved as a beneficial tribomaterial formulation in contact with a steel counterbody. The SCFs carry the most load applied on the tribosystem, while the internal lubricants improve the friction behavior of the polymer matrix. In the present study, the roles of rigid particles on the friction and wear performance of SCF filled Polybutylenterephthalate (PBT) with and without graphite were investigated by using a pin-on-disc (PoD) tribometer under dry sliding condition. The experimental results show that the tribocomposite filled with nanoparticles without graphite particles presents outstanding friction and wear performance especially under moderate and severe load conditions in combination with superior mechanical properties compared with graphite-filled tribocomposite. The friction coefficient and wear rate under a pv-condition of 3 MPa and 2 m/s are 0.18 and 0.8*10−6 mm3/Nm, respectively. Based-on the optical analysis of the worn surfaces of the polymer samples and the transfer layers formed on the steel disc, the possible friction and wear mechanisms were discussed.

A high-resolution study of graphite nodule formation in experimental medium-carbon machining steel

Alloying a medium-carbon steel has accelerated graphite formation during annealing, for example, during high-temperature tempering. Electron microscopy and related techniques have been used to characterise the graphite particle structure and dispersion from pre-anneal starting microstructures of ferrite-pearlite, bainite and martensite. Graphitisation in the solid state in steels (and also, for useful comparison, in cast irons) has previously received little attention. However, FIB/FEGSEM has permitted specimen preparation of the relatively coarse microstructures, thus enabling high-resolution observation previously limited for graphite formation in cast irons and steels. The study has importance to the potential development of more economic and user-friendly machining steels, which would rely upon internal lubrication by graphite nodules within the microstructure. Many recently developed advanced steels are reduced in carbon but expensively alloyed to produce the desired properties, whereas an aim in this project is simply to use carbon, which is a very cheap and abundant alloying element.

Tribological Properties of Porous PEEK Composites Containing Ionic Liquid under Dry Friction Condition

NaCl particles were added into Polyetheretherketone (PEEK) and its composites to produce porous PEEK-based materials by washing NaCl away after the high-temperature compression molding process. After that, an ionic liquid was added into the porous materials under vacuum condition. Carbon fibers (CF), as reinforcement, and PTFE, as an internal solid lubricant, were employed to prepare PEEK composites. Tribological properties under dry friction condition were studied on a ring-on-disc tribo-meter. The influence of CF and PTFE on tribological properties was carefully investigated. The results indicated that, in comparison with traditional PEEK composites (CF/PTFE/PEEK), the porous PEEK composites containing ionic liquid showed much better tribological properties. It is found that CF can help PEEK form effective pores to suck in the ionic liquid resulting in a better tribological performance. CF reinforced porous PEEK containing ionic liquid (p-CF/PEEK + IL) demonstrated the lowest friction coefficient (27% of CF/PTFE/PEEK) and the lowest wear loss (only 0.9% of CF/PTFE/PEEK). Long time tribological test revealed that the wear mass loss comes from the running-in period, while its wear is negligible after this period. It is also found that the addition of PTFE has a negative influence on the tribological behaviors, especially under high sliding velocity and applied load.

The Influence of Oil Pressure in the Engine Lubrication System on Friction Losses

The purpose of the internal combustion engine lubrication system is to provide optimal conditions for the oil film formation in all friction couples, such as a piston-cylinder, piston rings-cylinder, main bearings, etc. The oil film is designed to minimize the wear of the elements while ensuring the smallest possible friction losses. Lack of continuity of the oil film, and thus boundary or mixed friction conditions, obviously have a negative effect on the friction losses. However, the continuous oil film, depending on the conditions of its formation, may be characterized by different values of friction losses. One of the factors that may affect the conditions of formation of the oil film is the value of oil pressure in the lubrication system. In the paper the results of researches on friction losses carried out on an engine test bench are presented. The study consisted of measuring the driving torque of the internal combustion engine by an electric machine which is the source of power for the internal combustion engine. The oil temperature, the oil pressure, which was generated by independent from the engine oil pump, and the rotational speed of the crankshaft were the variables during test stand measurement. The article analyzes the results and conclusions are drawn.

Permanent Strain Behavior of Marginal Granular Material

To better understand the marginality of marginal granular materials (i.e., an aggregate that does not fully meet a premium quality specification), this study investigated the permanent strain behavior of two granular materials with different geological and mineralogical characteristics under repeated loading and different moisture conditions. The secant permanent strain rate and shakedown approach were used to analyze the permanent strain behavior of the materials. A one-dimensional swelling test was used to explain the mechanism of the permanent strain behavior of the soaked materials under repeated loading. The results show that compared with a New Zealand premium quality aggregate, the marginal aggregate exhibits a more significant increase in the cumulative permanent strain and the secant permanent strain rate after the 4-day soaking process. The results of the shakedown approach illustrate that the marginal aggregate performs reasonably well to resist permanent deformation in a dry condition, but the performance will considerably deteriorate when in contact with water under high stress. This change is a result of the presence of swelling clay minerals (e.g., smectite) in the marginal aggregates. The result of the one-dimensional swelling test indicates the high swelling potential of marginal aggregate, which provides an explanation for its poorer resistance to permanent strain. The marginal aggregate gains undesirable internal lubrication when surrounded by (moist) swelling clay mineral particles; thus, its shear strength reduces and permanent strain rate increases under repeated loading.

Effect of the External Lubrication Method for a Rotary Tablet Press on the Adhesion of the Film Coating Layer.

External lubrication is a useful method which reduces the adhesion of powder to punches and dies by spraying lubricants during the tableting process. However, no information is available on whether the tablets prepared using an external lubrication system can be applicable for a film coating process. In this study, we evaluated the adhesion force of the film coating layer to the surface of tablets prepared using an external lubrication method, compared with those prepared using internal lubrication method. We also evaluated wettability, roughness and lubricant distribution state on the tablet surface before film coating, and investigated the relationship between peeling of the film coating layer and these tablet surface properties. Increasing lubrication through the external lubrication method decreased wettability of the tablet surface. However, no change was observed in the adhesion force of the film coating layer. On the other hand, increasing lubrication through the internal lubrication method, decreased both wettability of the tablet surface and the adhesion force of the film coating layer. The magnesium stearate distribution state on the tablet surface was assessed using an X-ray fluorescent analyzer and lubricant agglomerates were observed in the case of the internal lubrication method. However, the lubricant was uniformly dispersed in the external lubrication samples. These results indicate that the distribution state of the lubricant affects the adhesion force of the film coating layer, and external lubrication maintained sufficient lubricity and adhesion force of the film coating layer with a small amount of lubricant.

Friction characteristics of self-lubricating ABS under different surface roughnesses and temperatures

N, N"-Ethylenedistearamide (EBS) and poly(ethylene-co-octene) (EN) were selected as internal lubricants for ABS to improve its friction characteristics. The effects of additive type, part surface roughness and testing temperature on the friction characteristics were investigated and found that at 80°C, kinetic COF were lower than at 23°C owing to thermal softening and melting of rubber components of the contacting surfaces. EN was more effective than EBS in reducing COF and double amplitude of stick-slip curves of ABS both at 23°C and 80°C due to the decrease in surface energy and adhesion between moving surfaces with EN added. At 23°C kinetic COF of ABS+5wt%EN showed strong dependence on the surface roughness while this was not the case for ABS and ABS+0.5wt%EBS.

High-Resolution Metallography of a Coarse Microstructure: Graphite Formation in the Solid-State in Steel

Abstract The equilibrium form of carbon in iron and steel is graphite. In higher carbon cast irons graphite is normally formed from the liquid state. In lower carbon steels, carbon invariably exists in the form of metastable cementite, due to slow graphitization kinetics in the solid, but in fact, graphite formation is also more likely to be prevented by alloying to stabilize the microstructure for service. Relatively few high-resolution studies of graphite formation have thus been made in the past; this is also because of probable difficulties associated with specimen preparation of a relatively coarse aggregate microstructure. More recently, new investigative techniques and methods have allowed closer examination of graphite formation in steels. Examples are given of HRTEM, EELS, ELNES, EFTEM, and FIB/FEGSEM recently applied to observations of graphite nucleation and growth in the solid state in steel. This has importance, for example, in the potential development of more economic and user-friendly machining steels, which would rely upon internal lubrication by graphite particles in the microstructure.

Evaluation of Octyltetramethyldisiloxane‐Containing Ethylene Copolymers as Composite Lubricant for High‐Density Polyethylene

A series of octyltetramethyldisiloxane‐containing ethylene copolymers, poly(ethylene‐co‐OO7) (abbreviated as E‐co‐OO7), are prepared from vanadium catalyzed copolymerization of ethylene with 1‐oct(7‐en)yl‐3‐octyl‐1,1,3,3‐tetramethyldisiloxane (or OO7) macromonomer. The copolymers containing different silicone contents are employed as composite lubricants for high‐density polyethylene (HDPE). The influences of the silicone content in the copolymer and that of the added copolymer amount in the blend on the bulk and surface properties of the blends are systematically investigated. The results show that E‐co‐OO7 exhibits superior overall performance in comparison with conventional lubricants silicone masterbatch and polyethylene wax. Compared to HDPE control, 10 wt% E‐co‐OO7 addition increases the melt flow rates by 49%, increases the elongation at break from 740 to 860%, increases the water‐contact angle from 90° up to 108°, lowers the coefficient of friction from 0.072 to 0.049, lowers the specific wear rate from 11 × 10−3 to 5.6 × 10−3 mm3 Nm−1. The impact strength and high temperature thermal stability are also slightly improved. The measured Si/C atomic ratios demonstrate the sufficient silicone enrichment on surface of the blends. E‐co‐OO7 with 23.5 SiOSi per 1000 C gives the best internal lubrication, and E‐co‐OO7 with 29.7 SiOSi per 1000 C gives the best external lubrication.image

Improved crystallizability and processability of ultra high molecular weight polyethylene modified by poly(amido amine) dendrimers

Ultrahigh molecular weight polyethylene (UHMWPE) is usually difficult to be melt processed due to severe intermolecular entanglement in its melt. In this work, we reported the development of a poly(amido amine) (PAMAM) dendrimer (G1) and its derivatives with different terminal groups which showed promising feasibility for aiding UHMWPE melt processing. The rheological, crystalline, and mechanical properties of the blends were investigated comprehensively. The addition of the dendritic modifiers to the UHMWPE matrix resulted in a significant decrease in melt viscosity, thus an obvious enhancement of the processability. The dynamic analysis of the mechanical properties and rotation-rheological test indicated a disentanglement effect of the UHMWPE melt molecules was generated by the PAMAM dendrimer (G1) and its derivatives. Furthermore, the PAMAM dendrimer (G1), as an internal lubricant, was uniformly distributed in the UHMWPE matrix. The heteronucleation effect of the PAMAM dendrimer (G1) with its derivatives led to a higher degree of crystallinity, smaller crystallites in the matrix and enhanced tensile strength in the UHMWPE blends. POLYM. ENG. SCI., 57:153–160, 2017. © 2016 Society of Plastics Engineers

The structure properties and tribological behavior of the ionic liquid–polyimide composite films under high-vacuum environment

Ionic liquid (IL) can be used as external or internal lubricant. The tribological performance of polyimide (PI)–steel contact surface driven by IL lubricant was investigated using a ball-on-disk tribometer in high-vacuum environment. The experimental results indicated that IL as the external lubricant could obviously decrease the friction coefficient of PI from 0.41 to 0.01 and corrode the surface of steel ball. As internal lubricant, some IL/PI composite films were prepared, and the structure properties and tribological behavior were investigated. IL can be uniformly dispersed in the polymer and could make film surface more hydrophilic along with the increasing content of IL in PI. The IL/PI composite film with 1% content of IL has the lowest friction coefficient and causes the least damage against the steel ball.

Development of devices for self-injection: using tribological analysis to optimize injection force

This article describes the use of analytical models and physical measurements to characterize and optimize the tribological behavior of pen injectors for self-administration of biopharmaceuticals. One of the main performance attributes of this kind of device is its efficiency in transmitting the external force applied by the user on to the cartridge inside the pen in order to effectuate an injection. This injection force characteristic is heavily influenced by the frictional properties of the polymeric materials employed in the mechanism. Standard friction tests are available for characterizing candidate materials, but they use geometries and conditions far removed from the actual situation inside a pen injector and thus do not always generate relevant data. A new test procedure, allowing the direct measurement of the coefficient of friction between two key parts of a pen injector mechanism using real parts under simulated use conditions, is presented. In addition to the absolute level of friction, the test method provides information on expected evolution of friction over lifetime as well as on expected consistency between individual devices. Paired with an analytical model of the pen mechanism, the frictional data allow the expected overall injection system force efficiency to be estimated. The test method and analytical model are applied to a range of polymer combinations with different kinds of lubrication. It is found that material combinations used without lubrication generally have unsatisfactory performance, that the use of silicone-based internal lubricating additives improves performance, and that the best results can be achieved with external silicone-based lubricants. Polytetrafluoroethylene-based internal lubrication and external lubrication are also evaluated but found to provide only limited benefits unless used in combination with silicone.

Tribological properties and thermomechanical analysis of unsaturated polyester fabric composite in oscillating line-contact sliding

The friction and wear properties of a composite containing unsaturated polyester resin with polyester fiber fabric reinforcement and internal PTFE lubricants are described under reciprocating dry sliding in a cylinder-on-plate contact against steel. By taking into account the deformation, creep, thermal expansion and strain recovery, on-line measurements for diameter reduction by wear are in agreement with post-mortem weight loss measurements. However, it is most important to consider the effects of the maximum polymer surface temperatures. The sliding properties are controlled by mechanical shear and plasticization of the PTFE lubricants under mild sliding conditions with a transition into instable sliding at 75°C correlating with curing of the matrix, and stable sliding at temperatures of 120°C corresponding to thermally-controlled sliding of PTFE.

Statistical tools and control of internal lubricant content of inhalation grade HPMC capsules during manufacture

The internal lubricant content (ILC) of inhalation grade HPMC capsules is a key factor to ensure good powder release when the patient inhales a medicine from a dry powder inhaler (DPI). Powder release from capsules has been shown to be influenced by the ILC. The characteristics used to measure this are the emitted dose, fine particle fraction and mass median aerodynamic diameter. In addition the ILC level is critical for capsule shell manufacture because it is an essential part of the process that cannot work without it. An experiment has been applied to the manufacture of inhalation capsules with the required ILC. A full factorial model was used to identify the controlling factors and from this a linear model has been proposed to improve control of the process.

2 つの給油口を有するジャーナル油膜すべり軸受内部の潤滑油流れのRGB カラーモデルによる可視化

2 つの給油口を有するジャーナル油膜すべり軸受内部の潤滑油流れのRGB カラーモデルによる可視化

Impact of process parameters on Mg–St content and tablet surface wettability in the external lubrication method for a rotary tablet press

External lubrication is a new alternative used in compression processes of the pharmaceutical industry to minimize the negative effect of lubricant and to resolve sticking problems. This method can also prevent the deterioration of tablet properties; e.g., reduced tensile strength and a retarded rate of drug dissolution. The current study prepared tablets using the external lubrication method with varying potential critical process parameters and clarified the process of external lubrication via statistical analysis. In accordance with past results, tablets prepared using the external lubrication method had better tablet properties (higher hardness and more rapid disintegration) than those prepared using the internal lubrication method. Quantitative analyses of the magnesium stearate content and contact angle showed that the wettability of the tablet surface increased with the magnesium stearate content. Analysis of variance showed that all potential critical parameters are influential for the magnesium stearate content, but not for the disintegration of tablets. In addition, predictions of the magnesium stearate content and disintegration time of tablets made using a model equation correlated well with observed values. The external lubrication method can thus be applied by identifying the critical process parameters in the compression process during the development and manufacture of pharmaceutical products.

Effect of starting microstructure upon the nucleation sites and distribution of graphite particles during a graphitising anneal of an experimental medium-carbon machining steel

The potential for using graphite particles as an internal lubricant during machining is considered. Graphite particles were found to form during graphitisation of experimental medium-carbon steel alloyed with Si and Al. The graphite nucleation sites were strongly influenced by the starting microstructure, whether ferrite–pearlite, bainite or martensite, as revealed by light and electron microscopy. Favourable nucleation sites in the ferrite–pearlite starting microstructure were, not unexpectedly, found to be located within pearlite colonies, no doubt due to the presence of abundant cementite as a source of carbon. In consequence, the final distribution of graphite nodules in ferrite–pearlite microstructures was less uniform than for the bainite microstructure studied. In the case of martensite, this study found a predominance of nucleation at grain boundaries, again leading to less uniform graphite dispersions.