Sound attenuation in composite friction materials containing thermoplastic elastomers

Attempts have been made for the first time to modify and improve the sound attenuation ability of a friction material by the inclusion of combined plastic/rubber properties of thermoplastic elastomers (TPE) as viscoelastic polymeric materials, into the formulation. To evaluate the attenuation coefficient (α) and also the real part wave number (k′) for the friction material, the viscoelastic parameters such as loss factor (tan δ) and elastic modulus (E′) were measured by the use of dynamic mechanical analyzer (DMA). Styrene‐butadiene‐styrene (SBS), styrene‐ethylene‐butylene‐styrene (SEBS) and nitrile rubber/polyvinyl chloride (NBR/PVC) blend system were used as TPE materials. However, SEBS and NBR/PVC were found to be much more effective in reducing the sound propagating speed as well as the sound level. All the friction materials containing TPEs exhibited more sound damping behavior at a wide range of temperature compared with the reference sample. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2187–2194, 2006     

Processing and tribology of thermoplastic polyurethane particulate composite materials

The processing, mechanical and tribological properties of wax containing thermoplastic polyurethane–filler composites were studied for different weight ratios of graphite, TiO₂, MoS₂, and ZrO₂ microparticles and SiO₂ nanoparticles. The composites were compounded by extrusion and processed by compression molding. The rheological, thermal, and mechanical properties were measured, and the wear characteristics were tested with ball-on-plate reciprocating tribometer tests under fixed friction conditions and then observed by scanning electron microscopy. Correlations between the friction, wear, and mechanical properties were observed, and their mechanisms are discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Elastomeric and electrically conductive materials on basis of thermoplastic elastomers and their controlled manufacturing

Abstract

The present work presents a possibility to produce a rubber elastic and electrically conductive polymer material on the basis of dynamic vulcanisates. Thanks to the specific morphology of dynamic vulcanisates and the non-uniform carbon black distribution, carbon black filled dynamic vulcanisates can exhibit a very low percolation threshold of ～4 wt-%. Keeping the carbon black content low, a broad spectrum of resistivity properties can be achieved by variation of material factors like type and content of rubber phase and filler, concentration of cross-linking agent and compatibiliser and technological factors like mixing time respectively. In comparison with thermoplastic elastomers on the basis of block copolymers dynamic vulcanisates show a distinct lower percolation threshold. Up to a carbon black content of ～10 wt-% the mechanical properties of carbon black filled dynamic vulcanisates are not negative influenced essentially. To characterise the development of the carbon black dispersion and distribution processes and the conductivity properties in an internal mixer, the method of online measured electrical conductivity is suited very well for carbon black containing rubber mixtures. It could be shown in pre-investigations that this method promises to be a very useful tool for monitoring the mixing processes of carbon black filled dynamic vulcanisates in continuous mixing processes by means of extruders too.     

Use of oxazoline functionalized polyolefins and elastomers as compatibilizers for thermoplastic blends

Oxazoline functionalized polypropylene, polyethylene, ethylene propylene copolymer (E/P), and styrene ethylene/butylene styrene copolymer (SEBS) were studied as compatibilizers in blends of polyolefins with polyesters and polyamides. The blends investigated were polypropylene/polyamide 6, polypropylene/polybutylene terephtalate, and polyethylene/polyamide 6, with engineering thermoplastic contents of 30 wt %. The blends were prepared in a twin-screw midiextruder, and injection molded with a mini-injection molding machine. The effect of compatibilizing on the morphology and mechanical properties of the blends was of interest. Compatibilization substantially improved the toughness of all tested blends. Their strength and stiffness remained at the level of the binary blends when polypropylene or polyethylene based compatibilizers were used, but slightly decreased with other compatibilizers. Morphological studies showed that the particle size was reduced, and the adhesion of the dispersed phase to the matrix improved by compatibilization. The effect of unfunctionalized polyethylene, polypropylene, E/P, and SEBS was also studied to compare the compatibilizers with them. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1923–1930, 1998     

Sorption and diffusion of a brake fluid in EPDM elastomers

This article reports on an investigation into how the morphology of four commercially available ethylene propylene diene monomer (EPDM) elastomers was affected by exposure to a brake fluid. The sorption and diffusion coefficients as a function of carbon‐black content as well as the EPDM type were determined at 23°C, 60°C, 100°C and 150°C. It was found that variation in carbon‐black loading showed an effect on the transport characteristics of EPDM elastomers. The sorption data at room temperature were not reported since these took too long a time. The leaching out of the indigenous additives might be due to the paraffin oil migrating to the surface of the specimens. The diffusion of the brake fluid in the EPDM membranes follows non‐Fickian transport. The results of this investigation are discussed in terms of the morphological differences in the EPDM formulations. The diffusion coefficients showed a dependence on the morphology of EPDM, as studied by the glass‐transition temperature of the elastomers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 000–000, 2001     

Fabrication and properties of thermoplastic starch/montmorillonite composite using dialdehyde starch as a crosslinker

The poor mechanical properties and high water solubility of biodegradable thermoplastic starch (TPS) represent the main disadvantages of TPS in many applications. In this work, TPS film was prepared from a water solution of corn starch modified by 5 wt% dialdehyde starch (DAS) as crosslinking agent and 3 wt% montmorillonite (MMT) as reinforcing additive. Interactions occurring in the TPS films were investigated by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, XRD, DSC, dynamic mechanical thermal analysis (DMTA) and TGA. The results obtained fom FTIR spectroscopy and DSC suggest the formation of hydrogen bond interactions between the hydroxyl group of starch, DAS, the MMT layers and glycerol. DMTA indicated that the relaxation of films with DAS and MMT appears in a higher and broader temperature range due to the starch backbone stiffness; the extreme increase in the storage modulus confirmed the suggested interactions. The determination of the weight loss of the films in water indicated a significant increase of the water resistance of TPS due to incorporation of DAS and MMT. Changes in mechanical properties of the films containing DAS and clay were determined, showing a substantial increase in tensile strength from 2.7 to 6.7 MPa, while Young's modulus increased by 15 times for TPS modified with 5% DAS and 3% MMT. Therefore, the outcomes of this study confirmed that DAS is a suitable biomacromolecule crosslinker for starch and can significantly enhance TPS and TPS/MMT properties. © 2019 Society of Chemical Industry     

复合材料在风力发电上的应用发展

成本是制约风力发电的瓶颈,要突破风电成本低于3美分／（kW-h）的目标,采用新材料及其制程是关键。从性能、成型工艺、价格等方面对可回收的低成本和环保型的热塑型树脂取代热固性树脂,以及碳纤维取代玻纤的必要陛和可行性展开详细阐述。指出随着风电叶片的超大型化、轻量化及长寿化,选择碳纤维热塑性复合材料和技术是必然趋势。     

Sugarcane bagasse ash as a reinforcing filler in thermoplastic elastomers: Structural and mechanical characterizations

The incorporation of residues as reinforcing fillers in polymer composites has emerged as a viable solution, enabling improvements in the mechanical properties of these materials, and has also resulted in a reduction in the cost of the final product. In this work, sugarcane bagasse ash (SBA) was used as a reinforcing filler in comparison with commercial silica (CS) in thermoplastic elastomers prepared from the compatibility of low‐density polyethylene (LDPE) with natural rubber (NR). The composites were obtained by a physical mixture of LDPE and NR with different proportions of CS and SBA using a Haake rotational rheometer. The samples were analyzed by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and tensile testing. The results show that SBA has similar properties to CS, thus making its use feasible as a reinforcing filler in thermoplastic elastomers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41466.     

Reinforcement of maleated polyethylene/ground tire rubber thermoplastic elastomers using talc and wood flour

Maleated polyethylene (MAPE)/Ground tire rubber (GTR) thermoplastic elastomer with 50 vol % GTR was reinforced by incorporation of talc powder and wood flour. Scanning electron microscopy (SEM) reveals that maleated polyethylene (MAPE) has good compatibility with wood flour, but the adhesion with talc particles is weak. Tensile moduli of MAPE/GTR increase more significantly after inclusion of talc particles compared to wood flour. Prediction of the tensile modulus of hybrid MAPE/GTR/particle composites is successfully performed using a combination of Kerner and Halpin‐Tsai models. Elastic moduli are shown to depend strongly on both aspect ratio and level of particle dispersion in the matrix. Measurement of compression sets shows that elastic recovery of the compounds decreases after addition of solid particles. Samples having better particles/matrix compatibility show higher elastic recovery. Thermogravimetric analysis shows that inclusion of wood flour decreases thermal stability of compounds. Density and hardness of MAPE/GTR are also shown to increase after inclusion of particulate reinforcements. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40195.     

Initial tack and viscoelastic properties of MF/PVAc hybrid resins used as adhesives for composite flooring materials

The initial tack and viscoelastic properties of blends of melamine–formaldehyde (MF) resin and poly(vinyl acetate) (PVAc) emulsion on decorative veneer and plywood surfaces were investigated using a texture analyzer and dynamic mechanical thermal analysis (DMTA) at room temperature with respect to the 'open time', the time delay between applying an adhesive to a surface and contacting that surface with the other material. We determined and compared the effects of PVAc content, at 0, 30, 50, 70 and 100 wt%, in blends with MF resin. As PVAc is curable at room temperature, PVAc markedly affected the initial tack, as well as DMTA results. The degree of 'tack' was determined quantitatively based on the probe tack data. As the adhesion in an engineered flooring should be achieved in 2–3 min, the acceptable tack range is between 100 and 200 g. From the DMTA results, i.e., the tan δ _max values, the maximum loss modulus (E&Prime) and the rigidity (ΔE) of MF/PVAc blends at room temperature, it was found that tan δ and loss modulus (E&Prime) increased with increasing MF resin content. Moreover, the rigidities of the 70:30 and 50:50 MF/PVAc blends were higher than those of the other blends, especially in comparison with the pure 100% PVAc and 100% MF. We conclude that the initial tack correlates with the MF/PVAc blend ratio during the adhesion process at room temperature.     

Rheological and viscoelastic behavior of dynamically vulcanized poly(vinyl chloride)–epoxidized natural‐rubber thermoplastic elastomers

Dynamically vulcanized poly(vinyl chloride)–epoxidized natural‐rubber thermoplastic elastomers (PVC–ENR TPEs) were prepared using a semi‐EV vulcanization system. The compounds were melt‐mixed, and the rheological behavior was evaluated. The effect of curatives concentration on the rheological behavior using the shear dependence of viscosity and the activation energy for viscous flow was evaluated. Viscoelastic behavior was also investigated with the Monsanto MDR 2000. The parameters studied include the elastic modulus at maximum torque, the loss peak at maximum torque, and their ratio (tan δ). The data obtained were correlated with the material properties, such as hardness and resilience. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2886–2893, 1999     

Wear and thermal effects in low modulus polymer‐based composite friction materials

The wear properties of low modulus polymer‐based friction materials were studied. The wear equation W = K P^a V^b t^c was used to correlate the wear of polymer‐based friction material sliding against cast iron with the wear coefficient (K), load (P), speed (V), and time (t). The parameters were determined experimentally by varying only one variable at a time and keeping the other two variables constant. The wear rate of selected polymer‐based friction material was compared with cast iron friction material. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1181–1188, 2005     

Dynamic friction property and mechanism of line‐type thermoplastic polymer materials for new optical wiring technology

We have been developing a new optical wiring technology for installing indoor optical fiber cables directly into apartment houses for fiber to the home. The technology must minimize the friction of optical fiber cable. We reviewed many studies on friction behavior, and studied the friction properties of a wide variety of polymer sheets and optical fiber cables, and considered the friction mechanism. Relatively, soft polymer materials exhibited stick‐slip behavior and the hard polymers exhibited constant slip behavior. Lubricants are effective in reducing friction and play a dominant role as regards the friction property. Silicon and fluorocarbon agents play some role in converting the stick‐slip characteristic into constant slip behavior. A certain roughness is effective in reducing friction. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers.     

Efficiency of silver‐based antibacterial additives and its influence in thermoplastic elastomers

Styrene‐butylene/ethylene‐styrene‐based thermoplastic elastomers (TPE) are polymers with soft touch properties that are widely used for manufacturing devices that involve hand contact. However, when contaminated with microorganisms these products can contribute to spreading diseases. The incorporation of antibacterial additives can help maintain low bacteria counts. This work evaluated the antibacterial action of TPE loaded with silver ions and silver nanoparticles. The additives nanosilver on fumed silica (NpAg_silica), silver phosphate glass (Ag⁺_phosphate), and bentonite organomodified with silver (Ag⁺_bentonite) were added to the TPE formulation. The compounds were evaluated for tensile and thermal properties and antimicrobial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). All the additives eliminated over 90% of E. coli, but only NpAg_silica killed more than 80% of S. aureus population. The better effect of NpAg_silica was attributed to the additive's high specific surface area, which promoted greater contact with bacteria cells. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43956.     

电线电缆用阻燃热塑性弹性体的研究应用进展

介绍了几种用于电线电缆的阻燃热塑性弹性体的研究及应用,主要包括聚烯烃热塑性弹性体、苯乙烯类热塑性弹性体、聚氨酯热塑性弹性体和聚酯类热塑性弹性体。     

Bound rubber in elastomers: Analysis of elastomer-filler interaction and its effect on viscosity and modulus of composite systems

Bound rubber measurement may be very misleading as a measure of elastomer–carbon black interaction because sometimes only part of the apparently bound rubber is truly adsorbed on the carbon black surface. A theory is proposed which utilizes bound rubber measurements, but separates truly adsorbed rubber from other insoluble gel and enables calculation of the adsorbed elastomer layer thickness, a numerical value of interaction. Measurements of interaction were obtained for many different rubbers, including polybutadienes, styrene–butadienes, EPDMs, and butyl, with several different furnace blacks. An equation for viscosity of a rubber–carbon black composite is proposed, based on the degree of interaction obtained from the theory and the possible varying degree of orientation of the composite as the rate of shear is changed. This has been applied experimentally both to soluble elastomers and to an elastomer containing a nonrigid gel. The modulus of a vulcanized composite is shown to be related to the effective volume fraction of filler, which is equivalent to the volume fraction of filler plus adsorbed rubber, at temperatures above the glass transition temperature, regardless of the type of rigid filler. Below the glass transition temperature, the modulus depends only on the filler volume concentration.     

Deformation and fracture characterization of inelastic composite materials using potentials

An approach using strain energy-like potentials to characterize deformation and fracture of inelastic, nonlinear composite materials is described. The inelasticity may be due to various causes, including microcracking, microslipping, and rate processes responsible for fading memory (viscoelasticity). The concept of work potentials is introduced first, and then arguments are given for their existence for inelastic materials. Emphasis in the paper is on elastic composite materials with changing or constant states of distributed damage. Experimental results on polymeric composites are subsequently presented to illustrate this approach to deformation and fracture characterization. Finally, extension to viscoelastic behavior is discussed.     

Dynamic properties of thermoplastic butadiene–styrene (SBS) and oxidized short carbon fiber composite materials

In composites consisting of a thermoplastic butadiene–styrene (SBS) elastomer matrix reinforced with oxidized short carbon fiber, scanning electron microscopy (SEM) reveals the existence of matrix–fiber interactions, which are not detected when employing commercial carbon fiber. Interpretation of the dynamic properties and other parameters, such as equivalent interfacial thickness, and glass transition temperature, measured in terms of maximum damping temperature, as well as the apparent activation energy of the relaxation process, helps to explain the existence of such interactions. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1819–1826, 1998     

利用生物活性物质除臭的缓释固体清洁剂的研制

介绍了一种利用生物活性物质除臭的缓释固体清洁剂的研制过程及其性能评价。其最佳配方为缓释剂45g,混合表面活性剂15g,微生物材料30g,甘油30g,颜料0.5g,香料0.4g。该产品具有优良的除臭和保洁能力;且无腐蚀性,使用方便。     

Development and status of resin composite as dental restorative materials

Dental composites are comprised of a polymerizable matrix and reinforcing fillers that can be hardened into a solid restoration in the prepared tooth cavity. Composites are becoming increasingly popular due to their esthetics and improved mechanical and physical properties. However, dental composites still encounter several problems, mainly secondary (recurrent) caries, restoration fracture, excessive wear, marginal degradation, and tooth sensitivity. Therefore, extensive efforts are underway to improve the composite compositions and microstructure, and enhance their clinical performance and longevity. Relying on advances in materials science and technology, dental composites have been continuously improved and their clinical applications have been expanded. In this review article, the development of dental composites was summarized, including compositional changes, performance improvements in key areas, current research hot spots, and outlook for future direction. The intention is to provide a review of the history and development of dental composites with a discussion of strategies on addressing the current challenges facing dental composites. In addition, this review will provide a better understanding of dental composites and their properties for the practicing clinicians, to contribute to improving the quality of composite restorations. The review of literature indicates that while current composites are generally bio-inert and can replace the missing tooth structure, future composites should be bioactive and therapeutic to inhibit caries, modulate biofilms, and protect the surrounding tooth structures, in order to increase the restoration longevity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48180.