Intercalated clays from pentaerythritol stearate for use in polymer nanocomposites

Smectite clays treated with quaternary ammonium salts have been utilized for decades in paints, greases, cosmetics, and personal care products as rheological modifiers. They have also been used in industrial wastewater treatment extensively. In more recent times these surface modified clays have demonstrated benefits in polymer/clay nanocomposites. The use of quaternary ammonium modifiers limits the usefulness of these composites in food packaging because they are not approved for direct food contact. It would be advantageous to have surface modifying chemicals acceptable for direct food contact in these composites. This article reports research conducted on a promising surface modifier pentaerythritol stearate (PS), which is approved by the FDA for inclusion in food as a preservative. The surface modification of montmorillonite with PS is reported in detail as well as the production of nanocomposites with selected polymers made with the modified clay. Molecular modeling and purification of commercial PS samples indicate that the mono‐ and diesters are the critical surface modifiers, although the as received commercial material works well in forming intercalated clay complexes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical Properties of Plasma Surface-Modified Calcium Carbonate–Polypropylene Composites

Calcium carbonate was surface-modified by plasma-polymerized acetylene and the effect of surface modification on the mechanical properties of calcium carbonate–polypropylene composites was investigated. Two different plasma polymerization conditions were selected and applied. Chemical structures of plasma-polymerized acetylene products were identified. Mechanical and thermal properties of the composites prepared were evaluated and the effects of surface modification on the extent of adhesion of filler to the matrix, as well as on polymer phase, were investigated with the help of scanning electron microscopy. Some of the composite samples prepared with surface-modified calcium carbonate are found to yield higher percentage elongations and are mechanically superior compared to those prepared with unmodified filler. © 1997 SCI.     

Removal of chromium from waste water using polyaniline

One of the suitable methods for removing heavy metals from waste water is using surface adsorption process. In this article, the preparation of polyaniline and its composites as adsorbents are discussed and the capability of separating chromium from industrial waste water is studied. The results were compared with anthracite and cation exchangers such as purolite‐302 and amberjet. The observations indicated that the purolite and amberjet have the most chromium removal percentage. Also the role of polyaniline and its composite as adsorbents were studied. The results show that the percentage of chromium removal has increased in polyaniline/poly(vinyl alcohol) composite. Furthermore, the adsorption percentage is related to the surface morphology, type of adsorbents, and their weight ratios. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1964–1967, 2007     

Preparation of sialon–transition metal silicide composites

A process to prepare sialon–transition metal silicide composites is proposed in the present study. The oxides of transition metals are used as the starting materials and the metal silicides are formed in situ in sialons at elevated temperature. The metal oxides, silica and alumina in starting materials first form a liquid phase on sintering to assist the densification in the graphite furnace. The transition metals then precipitate out to react with Si₃N₄ to form silicides. The sialon–metal silicide composites with uniform microstructures can be produced. By applying a suitable post-sintering heat-treatment, metallic fibers can also be formed in situ in the surface region on samples. Results for both sialon–Cr-silicide and sialon–Fe-silicide composites are demonstrated in the present study.     

Acid-base character of carbon fiber surfaces

The acid-base character of the surfaces of commercially available carbon fibers used in advanced composites is determined using both pulsed and continuous flow microcalorimetry techniques. The carbon fibers investigated include unsized versions of AS4, IM6, IM7X, T300, and several Apollo fibers with different levels of surface treatment. All of these carbon fiber surfaces are amphoteric and energetically heterogeneous. In general, the heats of preferential adsorption in the pulsed flow mode of bases dissolved in n-heptane are larger than for acids. While most of the adsorbates used are reversibly and physically adsorbed onto the carbon fibers, some primary and secondary amines exhibit irreversible binding to a portion of the surface. In continuous flow experiments the adsorption heat isotherms for several bases on T300 display a sharp jump at low probe concentrations, reflecting the energetically heterogeneous nature of these surfaces. Comparisons between the flow microcalorimetry data and other measures of the surface chemistry are made. Pulsed flow adsorption heats correlate with the amount of oxidized carbon species on the fiber surfaces as detected using ESCA, and recently reported results of inverse gas chromatography and programmed thermal desorption (S. Wesson, Textile Research Institute). Calorimetry results are also compared with fracture mechanical measures of fiber-resin adhesion in manufactured composites. Adsorption heats of both acids and bases on selected carbon fibers correlate with edge delamination and 90° flexural strengths of composites composed of these fibers in both epoxy and bismaleimide resins. This supports a causal connection between carbon fiber surface adsorption heats and a practical measure of fiber-resin adhesion.     

Direct fluorination of Twaron fiber and investigation of mechanical thermal and morphological properties of high density polyethylene and Twaron fiber composites

Composites consisting of high density polyethylene (HDPE) reinforced with randomly oriented chopped Twaron fibers (both fluorinated and nonfluorinated) show a significant increase in mechanical and thermal properties. To increase the better fiber matrix adhesion, the Twaron fiber is surface fluorinated using elemental fluorine. The surface of the Twaron fiber becomes very rough and the diameter of Twaron fiber increases from ～ 12 to 14 μm after fluorination. The composites were prepared using solution method to overcome the damage of the fiber. The tensile strength and the Young's modulus increases with increasing fiber content. The tensile strength and modulus of modified fiber (fluorinated Twaron fiber) composites is much higher than nonmodified fiber composites indicating that there is better mechanical interlocking between the modified fiber and the matrix. Thermal properties obtained from DSC and DTA‐TG analysis of the fluorinated fiber composites are also improved. Contact angle measurements, as well as the surface energy measurements, indicate that the composites are more wettable and is maximum for fluorinated fiber composites i.e., surface energy for fluorinated fiber composites is highest. Crystallinity is also higher for fluorinated fiber composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Improved interfacial adhesion in carbon fiber/poly (ether ether ketone) composites with the sulfonated poly (ether ether ketone) sizing treatment

A water-soluble sulfonated poly (ether ether ketone) (SPEEK) sizing agent is prepared and applied to improve the interfacial adhesion of carbon fiber/poly (ether ether ketone) (CF/PEEK) composites. The surface morphology, surface roughness, surface chemistries, and surface free energy of SPEEK sized CF are obtained to understand the sizing effect. The results reveal the increased surface free energy and surface roughness of SPEEK sized CF. In addition, a chemical reaction between the CF surface and sizing layer is proved based on the results of XPS, IR, and ¹H NMR. The interfacial structure of CF/PEEK composites is further ascertained by AFM and the appearance of gradient interface could be verified for SPEEK sized CF/PEEK composites. The formation of the gradient interface is due to the chemical reaction between the CF and sizing agent as well as the improved compatibility between the sized CF and matrix, which benefits the improvement of interfacial adhesion.     

碳纳米管/丙烯酸酯橡胶复合材料的制备及性能研究

采用自制的大分子表面改性剂对多壁碳纳米管(MWNTs)进行表面改性,制备改性MWNTs/丙烯酸酯橡胶(ACM)复合材料,研究改性MWNTs用量对复合材料性能的影响,并与炭黑补强的ACM性能进行对比.结果表明:用MWNTs填充ACM制备的材料,其性能远优于炭黑补强的ACM橡胶的性能;随着改性MWNTs用量的增大,复合材料...     

钢—热塑性树脂界面之间粘合的耐水性研究

研究钢/粘合剂/聚乙烯层状复合材料在自来水中的耐水性能。使用两种钢基材进行比较;一种未经任何表面处理(So),另外一种经过磷酸化表面处理(S_1)。粘合剂是聚乙烯接枝马来酸酐(PE-g-MAH)。采用剥离强度测试来定量分析钢/粘合剂/聚乙烯之间的粘接性能。结果表明,经磷酸化处理的层状物的耐水性好。     

UHMWPE/PE复合材料的开发与性能研究

本文在阐述聚乙烯自增强复合材料(PE/PE)的涵义基础上,介绍超高分子量聚乙烯(UHMWPE)纤维增强聚乙烯复合材料的制备原理和新产品的加工技术与工艺特点;试验测得复合材料的性能,验证了为改善复合材料性能而采用的几种UHMWPE纤维表面处理方法的有效性;同时证实了界面粘结是影响UHMWPE/PE复合材料性能的关键因素;最后就UHMWPE/PE复合材料界面粘结机理展开讨论,并概述了界面穿晶层的起源、形态和结晶结构研究的新进展.     

Processing and Properties of Intermetallic/Ceramic Composites with Interpenetrating Microstructure

Intermetallic/ceramic composites represent an interesting class of materials for high-temperature structural and functional applications. These materials can be prepared via high-energy milling of pure metals with Al₂O₃ as well as of aluminum with metal oxides. During subsequent compaction via pressureless sintering, the components react to form dense composites that consist of interpenetrating networks of the ceramic and intermetallic phases. Microstructural investigations, mechanical properties, and resistivity and wear resistance measurements of selected composites are presented. Improved fracture toughness and bending strength, with respect to monolithic Al₂O₃, have been achieved.     

偶联剂处理陶瓷颗粒增强聚丙烯复合材料的性能

用熔融共混法制备了陶瓷颗粒增强聚丙烯复合材料,测试了复合材料的力学性能,探讨了研究了表面处理对PP复合材料性能的影响。结果表明:偶联剂处理陶瓷颗粒表面后,复合材料的拉伸强度和冲击强度均比未处理的有所提高。拉伸断面的扫描电镜照片分析表明,未活化处理陶瓷颗粒与PP的界面粘结较差,界面发现许多空隙;而偶联剂KH-550活化处理后,陶瓷颗粒能与PP界面粘结良好,在拉伸过程中多数陶瓷颗粒被基体牢固粘附而难以脱出。     

Tribological behavior of epoxy composites containing reactive SiC nanoparticles

The present article evaluated the sliding wear behaviors of epoxy and its composites filled with SiC nanoparticles. Polyglycidyl methacrylate (PGMA) and a copolymer of glycidyl methacrylate and styrene were grafted onto the nanoparticles as a measure of surface pretreatment, respectively. The grafted polymers were selected because the epoxide groups on PGMA would take part in the curing reaction of epoxy resin and covalently connect the nanoparticles with the matrix, while styrene acted as a copolymerized monomer to adjust the amount of the reactive groups of the grafted macromolecular chains, and hence the compatibility between the grafted polymers and the matrix. In comparison to the composites filled with untreated nano‐SiC particles, the composites with the grafted nano‐SiC exhibit improved sliding wear resistance and reduced frictional coefficient owing to the chemical bonding at the filler/matrix interface. The results were analyzed in terms of structure‐properties relationship of the composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2608–2619, 2007     

Surface Engineering Strategies to Enhance the In Situ Performance of Medical Devices Including Atomic Scale Engineering

Decades of intense scientific research investigations clearly suggest that only a subset of a large number of metals, ceramics, polymers, composites, and nanomaterials are suitable as biomaterials for a growing number of biomedical devices and biomedical uses. However, biomaterials are prone to microbial infection due to Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Staphylococcus epidermidis (S. epidermidis), hepatitis, tuberculosis, human immunodeficiency virus (HIV), and many more. Hence, a range of surface engineering strategies are devised in order to achieve desired biocompatibility and antimicrobial performance in situ. Surface engineering strategies are a group of techniques that alter or modify the surface properties of the material in order to obtain a product with desired functionalities. There are two categories of surface engineering methods: conventional surface engineering methods (such as coating, bioactive coating, plasma spray coating, hydrothermal, lithography, shot peening, and electrophoretic deposition) and emerging surface engineering methods (laser treatment, robot laser treatment, electrospinning, electrospray, additive manufacturing, and radio frequency magnetron sputtering technique). Atomic-scale engineering, such as chemical vapor deposition, atomic layer etching, plasma immersion ion deposition, and atomic layer deposition, is a subsection of emerging technology that has demonstrated improved control and flexibility at finer length scales than compared to the conventional methods. With the advancements in technologies and the demand for even better control of biomaterial surfaces, research efforts in recent years are aimed at the atomic scale and molecular scale while incorporating functional agents in order to elicit optimal in situ performance. The functional agents include synthetic materials (monolithic ZnO, quaternary ammonium salts, silver nano-clusters, titanium dioxide, and graphene) and natural materials (chitosan, totarol, botanical extracts, and nisin). This review highlights the various strategies of surface engineering of biomaterial including their functional mechanism, applications, and shortcomings. Additionally, this review article emphasizes atomic scale engineering of biomaterials for fabricating antimicrobial biomaterials and explores their challenges.     

Single-walled carbon nanotubes and their composites with polyaniline. Structure, catalytic and capacitive properties as applied to fuel cells and supercapacitors

The structure and hydrophilic–hydrophobic properties of SWCNTs before and after oxidative functionalization were studied by standard porosimetry method. The correlation between the values of specific surface of hydrophilic and hydrophobic pores for the two types of SWCNTs is discussed. The capacity properties of SWCNTs and their composites with polyaniline were also investigated. The composite layer is shown to have exceptionally high capacitance that is due to the large surface area of the former, as well as to the proceeding of the reversible faradaic reaction of counter ions intercalation into PANI. The structure and electrocatalytic properties of platinum metals incorporated by various methods into support of SWCNTs and their composites with PANI were studied. Kinetics of the reactions proceeding in DMFC and the mechanism of catalytic influence of the support are discussed. The structure of the catalytic layer is shown to be the main factor that determines the overall catalytic activity.     

Properties of nanoparticles filled soft poly(vinyl chloride) composites including antistatic plasticizer

Nanoparticles (NP) filled permanently antistatic poly(vinyl chloride) (PVC) composites, constituted of dibutyl phthalate (DBP) and antistatic plasticizer (AP) which included bis[2‐(2‐methoxyethoxy)ethyl]phthalate doped with sodium perchlorate (NaClO₄), were prepared in a Haaka torque rheometer. Surface resistivity measurement, mechanical test, scanning electron microscopy (SEM) investigation, and thermal gravimetric analysis (TGA)‐differential scanning calorimetry (DSC) analysis were used to investigate the comprehensive properties of PVC/AP/NP (100/40/x) (A40/NP) and PVC/AP/DBP/NP (100/40/40/x) (A80/NP) composites. The results demonstrated that the surface resistivity of A40/NP composites was lower than that of pure A40 composites at a humidity of 60% and 0.1% as the nano SiO₂ or TiO₂ content is 2 phr, respectively. Moreover, the surface resistivity of A40 composites was decreased by about half an order of magnitude even at the humidity of 0.1% when 2 phr of NP was added. The surface resistivity of A80/NP composites achieved the optimum value as the SiO₂ and TiO₂ content were 1 phr and 2 phr, respectively. Because the DBP functioned as small molecule plasticizer which endowed PVC composites with comparatively large free volume, the surface resistivity of A80/NP composites is much lower than that of A40/NP composites. The tensile strength and elongation at break of A40/NP (100/2) and A80/NP (100/2) were increased to some extent with respect to pure PVC/AP composites. DSC‐TGA analysis and rheological properties demonstrated that NP filled PVC composites processed good thermostability and thermoprocessability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polypropylene composites. III: Chemical modification of the interphase and its influence on the properties of PP/mica composites

A surface treatment technology was developed for PP/mica composites that produces a diffuse interlayer with excellent adhesion between the components. The interlayer is created by the silane treatment of the filler and the chemical modification of the polymer components, and its polarity gradually decreases from the surface of the filler to the matrix. Properties of the composites depend on the characteristics of the interphase. With changing chemical composition, the characteristics of the interphase change from a thin, rigid layer to a more diffuse, elastic one. Properties of the composites change accordingly, optimum properties are achieved with a thick interlayer ensuring good stress transfer, strength, hardness, acceptable impact properties, and low mold shrinkage.     

In situ formation of noble metal nanoparticles on multiwalled carbon nanotubes and its implication in metal–nanotube interactions

A simple method to decorate multiwalled carbon nanotubes (MWCNTs) with Au, Ag and Cu nanoparticles is illustrated. The method consists in directly depositing the selected metals by thermal evaporation on the carbon nanotubes. Comparative measurements carried out on samples that differ in the quantity and type of the deposited metal, reveal that isolated discrete particles form on the nanotube outer wall for all three metals. The CNT-based composites have been investigated by scanning and transmission electron microscopy to determine the size, shape and distribution of the nanoparticles. The results indicate that the quantity of evaporated metal only affects the nanoparticle size and not the average particle density. Particle composition was determined by X-ray photoelectron spectroscopy study. The results are discussed in terms of metal nanoparticle–tube interactions, an important issue for the fundamental and practical applications of similar MWCNT based composites.     

炭纤维表面处理对CF／PMR—15复合材料力学性能的影响

研究了炭纤维表面不同处理方法对复合材料力学性能的影响,采用等离子体和等离子体接枝技术对炭纤维表面进行处理后,CF／PMR－15复合材料的界面剪切强度与层间剪切强度均有所提高,随着界面状态的改善,界面剪切强度提高的幅度比层间剪切强度提高的大,本文为指导炭纤维的表面处理,评价处理效果,进一步预报复合材料的宏观性能打下了基础。     

Surface preparation for adhesive bonding of polycyanurate‐based fiber‐reinforced composites using atmospheric plasma treatment

In this article, the effects of atmospheric plasma treatment on the microstructural, chemical, and mechanical behavior of epoxy‐bonded polycyanurate composites are investigated. Adhesive bond strength of plasma‐treated specimens exhibited strength increases of over 35% to that of peel‐ply and solvent‐wiped surface preparation techniques. The improvements were as much as 50% greater than those obtained using abrasive surface preparation techniques. X‐ray photoelectron spectroscopy analysis showed an increase in the surface concentration of oxygen as a function of plasma treatment passes. However, the levels were substantially lower than that of epoxy composites treated under identical conditions. In addition, the concentration of carboxyl groups (O CO), which have been associated with improved adhesive strength in epoxy‐based composites, was shown to saturate in cyanate ester composites after a much lower exposure period than what was observed when treating epoxies. The effect of plasma surface treatment on the surface morphology of the cyanate ester composite was also studied using scanning electron microscopy and atomic force microscopy. Atomic force microscopy analysis showed a progressive increase in surface roughness with treatment; however, this increase only translated into a marginal increase in surface area and is not believed to contribute significantly to adhesive strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011