The Effects of Surface Treatment

Workers do have divergent opinions about the reasons for improved bonding after surface treatment and a selection is described along with an attempted summary. 

Herrick [98] treated Thornel 25 with HNO3 and found that the ILSS of the resultant composite, the specific surface area and the number of surface oxygen complexes increased. Treatment with H2 removed the surface oxygen groups accompanied by a distinct reduction in ILSS, suggesting that the surface groups improved the fiber/resin bond. 

This work was questioned by Scola and Brooks [99], who, whilst agreeing that the surface area and the amount of surface groups were increased, argued that H2 reduction of oxidized Hitco HMG 50 did not alter the ILSS, the process having presumably removed the surface groups. 

Harvey [100] studied the surface area by gas adsorption (BET) and the adsorption of aqueous solutions of the dyes, methylene blue and metanil yellow, on Courtaulds types A, HT and HM carbon fibers. 

Fiber type Kr BET surface area pmol g Adsorption methylene blue msat pmol g Adsorption metanil yellow fflsat (imol g  

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It is critical that surface treatment conditions be optimized to composite properties since overtreatment as well as undertreatment will degrade composite properties. Typically composite interlaminar shear strength (ILSS), in-plane shear, and transverse tension ate used to assess the effectiveness of surface treatment. More recently damage tolerance properties such as edge delamination strength, open hole compression, and compression after impact have become more important in evaluating the toughness of composite parts. 

Surface treatment of the composite can have a significant effect on adhesion. Surface treatment enhances one or more of the mechanisms described previously. Wu et al. [15] studied the effects of surface treatment on adhesive bonding for AS-4/APC-2 laminates. They found that the greatest bond strength was achieved from acid etching and plasma etching the composite surface. Table 1 summarizes the various surface treatments that were evaluated. 

Wu, S.Y, Schuler, A.M. and Keane, D.V., Adhesive bonding of thermoplastic composites 1. The effect of surface treatment on adhesive bonding. 9th Int. SAMPE Symp., Oct. 13-15, 1987. 

The coarseness of a surface and consequently the effect of surface treatment can be measured with a laser beam. In addition the surface is often investigated by means of various microscopic techniques. The nature of a surface can tell us something of the structure of the material. The information obtained depends on the treatment the area has undergone and the way in which the surface is examined. The researcher may want to determine how many phases there are present in the sample, how they are distributed throughout the sample or what the pores and the pores distribution are like. For these purposes many kinds of light and electron micros-copes are available. 

Flexible epoxy adhesives generally give good bond strengths to heated fluorocarbon surfaces. Table 16.11 shows the effect of surface treatments on the bondability of epoxy... 

Chapter 4 describes how the electrical nature of corrosion reactions allows the interface to be modeled as an electrical circuit, as well as how this electrical circuit can be used to obtain information on corrosion rates. Chapter 5 focuses on how to characterize flow and how to include its effects in the test procedure. Chapter 6 describes the origins of the observed distributions in space and time of the reaction rate. Chapter 7 describes the applications of electrochemical measurements to predictive corrosion models, emphasizing their use in the long-term prediction of corrosion behavior of metallic packages for high-level nuclear waste. Chapter 8 outlines the electrochemical methods that have been applied to develop and test the effectiveness of surface treatments for metals and alloys. The final chapter gives experimental procedures that can be used to illustrate the principles described. 

The interface between plastic and wood fibres strongly influences the mechanical properties of a plastic/wood fibre composite. A means for evaluating the effectiveness of surface treatment on the wood fibres in the PVC/wood fibre composites is presented that investigated the adhesion between PVC and laminated wood veneers. Wood veneers were first treated with gamma-aminopropyltriethoxysilane, dichlorodiethylsilane, phthalic anhydride, and maleated PP for surface modification. The chemical modification made on the wood surfaces was then characterised by different complementary surface analytical techniques X-ray photoelectron spectroscopy and surface tension measurements. 63 refs. 

In addition to the particle size expressed in the jetness (My-value), the surface chemistry of the pigment blacks has a decisive influence on their processing behavior. The effect of surface treatment on the performance of pigment black in coatings was shown in Section 4.4.7. 

We investigated the use of the molding resin powder (<150 m) as a filler for construction materials composed of bisphenol A type epoxy resin and amine type hardener, and compared the material properties with those produced with a silica powder filler (<150 fi m). Furthermore, the effect of surface treatment of the molding resin powder on these properties was examined by using epoxy or amino silane coupling agents, which were added at lwt% to the molding resin powder and heated at 100°C for 1 hr. 

This equation was used to estimate the interfacial adhesion in comparison with the acid-base properties of glass fibers in LDPE. The effect of surface treatment of glass beads on their interfacial adhesion to PET was also estimated from a mechanical property measurement. A mathematical model describing the adsorption of polymers on filler surfaces related coupling density to the average area available for coupling between rubber and filler surface. ... 

Several examples may be quoted from the literature to illustrate the adsorption of surfactant ions onto soHd surfaces. For a model hydrophobic surface, carbon black has been chosen [22, 23], and Figure 5.5 shows the typical results for the adsorption of sodium dodecyl sulphate (SDS) onto two carbon black surfaces, namely Spheron 6 (untreated) and Graphon (graphitised), which also describes the effect of surface treatment. 

Ellaz N et al (2009) The effect of surface treatment on the surface texture and contact angle of electrochemically deposited hydroxyapatite coating and on its interaction with boneforming cells. Acta Biomater 5(8) 3178-3191... 

In the low shear rate region, the first normal stress difference increases with the fiber content, which may be due to the hydrodynamic effect associated with fiber orientation in the flow direction. The effect of surface treatment was identical to that in the high shear rate region. The shear viscosity and the first normal stress difference as a function of shear rate for maleic anhydride modified PP (5wt.%) added composites (GF/mPP/PP compositese) are plotted in Fig. 2. Although the overall level of the both functions rj and Nj was higher than that in GF/PP composites (Fig. 1), the effect of surface treatment by lwt.% ASC on rj and NiofGF/PP composites is similar to that of GF/mPP / PP. 

It is evident that a large number of parameters are involved in the fabrication and testing of bulk adhesive specimens and adhesive joints these must be controlled if meaningful experimental data are to be obtained. Joint tests evaluate not only the mechanical properties of the adhesive, but also the degree of adhesion and the effectiveness of surface treatments. The standard test procedures listed by ASTM, BSI, DIN and other official bodies are essentially for testing adhesives and surface treatments rather than joints (e.g. Table 4.3). Unfortunately, most of these tests consist of joints in which the adhesive stresses are far from uniform. The designer and the researcher therefore have to select appropriate tests, and to know what the results mean in terms of their own particular investigations and applications. 

Manocha et al [32] reported the effect of surface treatment and preferred carbon fiber with a circular cross-section, which was less likely to form stressed areas around the filament periphery [33]. 

Park RC, Jang JS, Impact behavior of carbon fibre polyethylene fibre hybrid composite, the effect of surface treatment of polyethylene fibre, Polymer Composites, 19(5), 600-607, 1998. 

The effect of surface treatment on the mechanical properties of carbon-fibre composites Brittle fibres in a brittle matrix can have appreciable toughness because the cracks can get diverted along the fibre-matrix interface. If the bond is weak the composite will not support loads in shear or compression, but when the bond is too strong, the material will be brittle. These aspects are illustrated in Fig. 6, where it is seen that the interlaminar shear strength reaches a plateau but the notched tensile strength decreases... 

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