Surface Chemical Study of Sheet Molded Composite (SMC) as Related to Adhesion

Surfaces of commercial sheet molded composite (SMC) materials have been characterized by X-ray photoelectron spectroscopy (XPS) before and after various surface treatments. Surface treatments included cleaning with methylene chloride, abrasion using methylene chloride and a Scotch Brite ® abrasive pad, and application of an isocyanate primer. The pretreated SMC materials were bonded using a polyurethane adhesive. Bonded coupons were tested under a variety of conditions using the lap shear technique. Lap shear test results for specimens bonded following the abrasion and primer pretreatment indicated a favorable fracture force and mode of failure. Surface analysis studies were used to characterize the pretreated and failed surfaces.     

Surface Properties and Adhesion of Flame Treated Sheet Molded Composite (SMC)

The surface chemistry of sheet molded composite (SMC) following interaction with a natural gas/air flame operated under reducing, stoichiometric, and oxidizing conditions has been investigated. The SMC surface chemistry is altered to contain in addition to hydrocarbon, ether, and ester functional groups, carbonyl and a greater carboxyl concentration. The extent of surface oxidation varies with the flame condition in the manner oxidizing ～ stoichiometric > reducing. Lap shear tests carried out at 82°C (180°F) for coupons bonded with a urethane adhesive did not fail by fiber tear. Surface analysis results indicate failure at an oxidized SMC-adhesive/non-oxidized SMC interface and within the non-oxidized SMC surface.     

An Investigation of the Effect of Plasma Treatment on the Surface Properties and Adhesion in Sheet Molded Composite (SMC) Material

Sheet molded composite was treated with different plasmas (oxygen, dry air, nitrogen, and argon). Plasma treatment of SMC alters the surface properties in a manner dependent on the type of plasma used and the time of treatment. The surface properties were evaluated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Fourier transform infrared spectros-copy (FTIR). A two-part urethane adhesive was used to prepare lap shear specimens. Untreated SMC, plasma-treated SMC, and primer-treated SMC were prepared, bonded and tested. The surface properties of the failed specimens were measured. The adhesion characteristics of SMC and the surface properties of the failed specimens were correlated with the type of treatment and the surface properties of treated SMC. Comparison of the surface and adhesive properties of plasma-treated samples with those for untreated samples indicates a) an increase in roughness, b) an increase in the level of SMC surface oxidation, and c) an increase in the failure force for lap shear tests.     

An Investigation of the Effect of Plasma Treatment on the Surface Properties and Adhesion in Sheet Molded Composite (SMC) Material

Sheet molded composite was treated with different plasmas (oxygen, dry air, nitrogen, and argon). Plasma treatment of SMC alters the surface properties in a manner dependent on the type of plasma used and the time of treatment. The surface properties were evaluated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Fourier transform infrared spectros-copy (FTIR). A two-part urethane adhesive was used to prepare lap shear specimens. Untreated SMC, plasma-treated SMC, and primer-treated SMC were prepared, bonded and tested. The surface properties of the failed specimens were measured. The adhesion characteristics of SMC and the surface properties of the failed specimens were correlated with the type of treatment and the surface properties of treated SMC. Comparison of the surface and adhesive properties of plasma-treated samples with those for untreated samples indicates a) an increase in roughness, b) an increase in the level of SMC surface oxidation, and c) an increase in the failure force for lap shear tests.     

The Adhesively Bonded Aluminium Joint: The Effect of Pretreatment on Durability

The interface in aluminium bonded structures can be revealed by ultramicrotomy and subsequently studied by transmission electron microscopy. By these means, the more usual surface pretreatments encountered, have been characterised in depth.

A similar examination has been effected following exposure of bonded joints (floating roller peel specimens) to 85% relative humidity at 70°C. Although a drop in peel performance is noted over the exposure time, interfacial examination reveals little damage to the adhesive or adherend. Possible mechanisms for bond strength reduction are discussed: subtle undermining of the alumina film and disruption of physico-chemical bonds across the interface. Both are initiated by moisture reaching the alumina film, either passing along the interface itself or travelling through the adhesive matrix. Also considered are the effects of surface pretreatment and “oxide” penetration, by the adhesive, on durability.

The effect of priming the adherend surface prior to bonding, using a heavily strontium chromate filled adhesive primer, is mentioned and its possible influence on durability is briefly discussed.     

The Adhesively Bonded Aluminium Joint: The Effect of Pretreatment on Durability

The interface in aluminium bonded structures can be revealed by ultramicrotomy and subsequently studied by transmission electron microscopy. By these means, the more usual surface pretreatments encountered, have been characterised in depth.

A similar examination has been effected following exposure of bonded joints (floating roller peel specimens) to 85% relative humidity at 70°C. Although a drop in peel performance is noted over the exposure time, interfacial examination reveals little damage to the adhesive or adherend. Possible mechanisms for bond strength reduction are discussed: subtle undermining of the alumina film and disruption of physico-chemical bonds across the interface. Both are initiated by moisture reaching the alumina film, either passing along the interface itself or travelling through the adhesive matrix. Also considered are the effects of surface pretreatment and “oxide” penetration, by the adhesive, on durability.

The effect of priming the adherend surface prior to bonding, using a heavily strontium chromate filled adhesive primer, is mentioned and its possible influence on durability is briefly discussed.     

复合材料表面膜的制备与性能研究

采用丙烯酸酯齐聚物改性合成了一种环氧基复合材料表面膜,并用丁腈橡胶增韧,芳香族二胺提高材料整体热性能。通过万能拉伸机、红外光谱、流变仪和热失重分析仪对其热性能、机械性能和老化性能进行了研究。研究了不同固化剂含量、增韧剂含量对体系整体性能影响。此外,当环氧树脂∶丙烯酸酯齐聚物∶固化促进剂质量比为100∶20∶5时,获得了优良的综合性能,经湿热老化后,室温下剪切强度超过20MPa,热分解温度超过290℃,其在耐高温胶黏剂领域具有良好的前景。     

The Effect of Abrasion Surface Treatment on the Bonding Behavior of Various Carbon Fiber-Reinforced Composites

Abstract

In this paper we show that current abrasion surface preparation practices do not perform equally on all composite surfaces. The effect of abrasion on the adhesive bond strength of various carbon fiber (CF) composites was investigated. Cyanate ester composites were fabricated using a low, a high and an ultra high modulus carbon fiber (T300, M55J, K13C2U). XPS and contact angle measurements showed that the surface energy of all three composites increased due to the removal of contaminants as well as increased in surface roughness. However, the lap shear strength degraded sharply for a number of cases, irrespective of roughness, depending on the fiber used. Composites utilizing lower modulus carbon fibers increased in adhesive bond strength following abrasion in comparison to composites with higher modulus fibers. As the modulus of the fiber and the abrasive grit size increased, the degree of degradation caused by abrasion was shown to increase significantly. Scanning electron microscopy (SEM) and profilometry measurements showed the development of an abrasion-affected zone that was especially prevalent for higher stiffness composites. The failures for the higher modulus specimens were caused by subsurface damage located a few fiber diameters below the abraded surface. However, an alternate technique using atmospheric plasma surface treatment exhibited efficient removal of contaminants while showing no degradation of bond quality when treating these ultra high modulus composites.     

Effect of Adherend Thickness and Mixed Mode Loading on Debond Growth in Adhesively Bonded Composite Joints

Symmetric and unsymmetric double cantilever beam (DCB) specimens were tested and analyzed to assess the effect of (1) adherend thickness and (2) a predominantly mode I mixed mode loading on cyclic debond growth and static fracture toughness. The specimens were made of unidirectional composite (T300/5208) adherends bonded together with EC3445 structural adhesive. The thickness was 8, 16 or 24 plies. The experimental results indicated that the static fracture toughness increases and the cyclic debond growth rate decreases with increasing adherend thickness. This behavior was related to the length of the plastic zone ahead of the debond tip. For the symmetric DCB specimens, it was further found that displacement control tests resulted in higher debond growth rates than did load control tests. While the symmetric DCB tests always resulted in cohesive failures in the bondline, the unsymmetric DCB tests resulted in the debond growing into the thinner adherend and the damage progressing as delamination in that adherend. This behavior resulted in much lower fracture toughness and damage growth rates than found in the symmetric DCB tests.     

Optimization of Surface Treatment and Adhesive Selection for Bond Durability in Ti-15-3 Laminates

The promising mechanical performance of a baseline Hybrid Titanium Composite Laminate (HTCL) inspired an investigation into maximizing the strength and environmental performance of this new aerospace material. This research focused upon finding the strongest and most durably combination of three commercially-available titanium surface treatments (i.e., Pasa-Jell 107^TM, Boeing's Sol-Gel, and Turco 5578^R) and two polyimide adhesives (i.e., LaRC^TM-IAX and FM5^R) for use in HTCL. The tests employed the cracked-lap shear (CLS) specimen geometry for fatigue crack growth measurements and also for fracture toughness analyses of the bonded specimens. The CLS geometry models several bonded applications found in the aerospace industry, and it also represents the debonding characteristics of a cracked titanium foil in HTCL.

The environmental performance of these six material combinations has been evaluated after 5,000 hours of continuous exposure to either a Hot/Wet environment that subjected the bonded specimens to 160°F (71°C) with relative humidity in excess of 95%, or to a Hot/Dry environment of 350°F (177°C) with a relative humidity of less than 5%. These two exposure environments utilized in this study are the most aggressive long-term environments that the HTCL is projected to experience while in service.

Test results showed that the best combination of the titanium surface treatments and the polyimide adhesives in the FM^R adhesive used in conjunction with Boeing's Sol-Gel titanium surface treatment. Though the FM5^R/Sol-Gel system was the strongest of all combinations, its performance dropped to less than 50% of its original strength after exposure to the Hot/Dry environment. An important finding is that this bonded system did not significantly degrade after exposure to the Hot/Wet environment. The only other material combination that showed substantial bond strength was the FM5^R/Pasa-Jell 107 system, though its strength also dropped to less than 50% of its original strength after exposure to the Hot/Dry environment.     

The Effect of Moment and Flexural Rigidity of Adherend on the Strength of Adhesively Bonded Single Lap Joints

In the present study, mechanical properties of different single lap joint configurations derived from adherends with different thicknesses subjected to tensile loading were investigated experimentally and numerically. For this purpose, experimental studies were conducted on two different types of SLJ samples, the first type with identical upper and lower adherend thicknesses and the second with different upper and lower adherend thicknesses. For the first type, five different thickness values were tested. For the second type, the lower adherend thickness was constant while five different upper adherend thickness values were tested. The adhesive was prepared from a two-part paste. After the experimental studies, stress analyses on the SLJs were performed with three-dimensional finite element analysis by considering the geometrical non-linearity and the material non-linearities of the adhesive (DP460) and adherend (AA2024-T3). It was observed that, in single lap joint geometry, variation in the thickness of the adherend and the use of lower and upper adherends with different thickness values changed the stress concentrations at the edges of the overlap regions, affecting the experimental failure load of the joints.     

新型铝-锆酸酯偶联剂的制备及其对轻质碳酸钙表面性能的影响

研究开发出一种阳离子型铝一锆酸酯偶联剂，并将其应用于轻质碳酸钙(沉淀碳酸钙)的表面改性，讨论了改性前后轻质碳酸钙的表面电荷、润湿性、沉降高度等表面性质的变化，并对改性轻质碳酸钙在造纸中的应用作了预测。     

Effects of Surface Modification on the Properties of Poly(lactide-co-glycolide) Composite Materials

HA/PLGA composites with and without APS-modification were successfully prepared via solution dispersion method. The mechanical test of composites was performed by the three-point-bending test and the micrographs of materials were observed using SEM. The results indicate that by surface modification, uniform HA particles without agglomeration were obtained. Furthermore, the bending strengths and moduli of APS-HA/PLGA composites are higher than those of unmodified composites, which both first increased and then significantly decreased with increasing the HA content. The biocompatibility results show that modified HA/PLGA composite are more favorable biomaterials for cell adhesion, differentiation and proliferation than unmodified composites.     

Effect of Water Vapor on Oxidation Processes of the Cu(111) Surface and Sublayer

Copper-based catalysts have different catalytic properties depending on the oxidation states of Cu. We report operando observations of the Cu(111) oxidation processes using near-ambient pressure scanning tunneling microscopy (NAP-STM) and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). The Cu(111) surface was chemically inactive to water vapor, but only physisorption of water molecules was observed by NAP-STM. Under O₂ environments, dry oxidation started at the step edges and proceeded to the terraces as a Cu₂O phase. Humid oxidation of the H₂O/O₂ gas mixture was also promoted at the step edges to the terraces. After the Cu₂O covered the surface under humid conditions, hydroxides and adsorbed water layers formed. NAP-STM observations showed that Cu₂O was generated at lower steps in dry oxidation with independent terrace oxidations, whereas Cu₂O was generated at upper steps in humid oxidation. The difference in the oxidation mechanisms was caused by water molecules. When the surface was entirely oxidized, the diffusion of Cu and O atoms with a reconstruction of the Cu₂O structures induced additional subsurface oxidation. NAP-XPS measurements showed that the Cu₂O thickness in dry oxidation was greater than that in humid oxidation under all pressure conditions.     

烷醇酰胺硫酸酯钠的制备及表面性能研究

以钠做催化剂,用棕榈酸甲酯,硬脂酸甲酯同乙醇胺,异丙醇胺反应制备了高纯度的烷醇酰胺,测定了硫酸化产品的外皂分散力,克拉夫特点,临界胶闭浓度及钙离子稳定性。     

NOTE The Application of Surface Analysis Techniques in the Adhesive Bonding of Oily Automotive Steel

There are fewer papers on the adhesive bonding of steel for structural applications than for aluminum and titanium alloys. However, the approach to the adhesive bonding of all three adherends has been similar, that is, the surfaces are pretreated prior to bonding. Trawinski, et al.^1,2,3 reviewed several conversion coatings or etching processes used for steel. Haak and Smith⁴ selected two surface treatments among nineteen based on minimal cost, simplicity and good durability. Smith⁵ has reported work on stainless steel-epoxy bonds under hydrothermal stress. Bischof, et al.⁶ investigated the effect of surface pretreatment of steel on bonding strength obtained with polyvinyl chloride. Ziane, et al.⁷ identified four fracture zones resulting from shear loading of epoxy bonded galvanized steel following four different surface pretreatments. But in some cases, as in the automotive industry, there is a need to bond oily steel directly without surface pretreatment. Rosty, et al.⁸ have reported a study of the role of fillers and cure temperature on the shear strength of oily steel bonded with epoxy. None of the reported research utilizes both microscopic and spectroscopic techniques to analyze the fracture surfaces.     

茶籽壳活性炭的制备条件及表面处理效果的研究

研究了茶籽壳活性炭的制备条件及化学表面处理的方法与效果。活性炭制备条件包括二种不同活化剂的浓度、高温炭化时间和高温炭化温度。实验结果表明:选用60%的ZnCl2溶液为活化剂,低、高温炭化时间为3+3h,低、高温炭化温度为300+600℃时,所制备的茶籽壳活性炭的比表面积为:1023.5g/m2。用硝酸及氨水对所制得的活性炭进行表面处理,能有效提高其活性炭对重金属和贵金属的吸附能力。实验结果表明:用氨水处理的活性炭,对重金属铅的吸附量提高了约41%,对贵金属银的吸附量提高约27%;用硝酸处理的活性炭,对重金属铅的吸附量提高了约53%,对贵金属银的吸附量提高约41%。可用于重金属废水的处理及贵金属的吸附回收。     

不同金属表面处理对高分子材料与金属连接强度影响

分别利用喷砂、氢氧化钠阳极氧化和激光毛化3种方法对钛合金板进行了表面处理,通过提高其表面粗糙度,来达到提高相应金属–高分子连接件连接强度的目的。其中激光毛化处理能有效提高相应连接件的拉伸性能,而氢氧化钠阳极氧化处理可以有效提高连接件的剥离强度。综合这两种处理方法所制备的金属–高分子连接件的连接强度得到明显提高,拉伸强度为322 MPa,断裂伸长率为5.1%,剥离强度为4.70 N/cm。     

The Effect of Surface Treatments on Tensile Bond Strength between a Silicone Soft Liner and a Heat-Cured Denture Base Resin

This study evaluated tensile bond strength of a denture soft lining material to a poly (methylmethacrylate) (PMMA) denture base resin subjected to different surface treatment modalities and thermocycling. The materials tested were a silicone-based liner, Molloplast B®, and a heat-cured denture base resin, Meliodent^TM. The denture soft lining material was packed against cured PMMA base resin, which was smoothed; sandblasted with 250-μm Al₂O₃ particles; or lased with a KTP laser; or against uncured PMMA dough (n = 10). In each group, five specimens were thermocycled in a water bath (5–55°C; 3000 cycles) before testing, whereas the other five were directly tested after 24 h. A tensile test was performed using a universal testing machine. Data showed that different treatment modalities of resin surfaces affected adhesion between these two materials and the highest bond values were recorded for cured/smoothed samples under each condition tested. Thermocycling of specimens had no significant reducing effect on measured bond strength values.     

响应面优化法在PDMS/PVDF膜制膜条件优化中的应用

用响应面优化法优化了乙烯基封端PDMS/PVDF渗透汽化透醇膜的制膜条件,研究了硅橡胶浓度、B/A质量比、交联温度和交联时间对膜性能的影响,拟合了分离因子、渗透通量与四因素之间的回归方程,并用方差分析法考察了四因素的主效应、二次效应以及相互作用效应对复合膜的分离因子与渗透通量的影响。研究发现,硅橡胶浓度对膜的分离因子与渗透通量的影响最为显著,交联时间对分离因子几乎没有影响。通过对回归方程的优化分析得知,在料液乙醇浓度为10%(wt),操作温度40℃条件下,当硅橡胶浓度为93%(wt),B/A质量比为0.08,交联温度为100℃,交联时间为13.83 h时,膜的综合分离性能达到最佳,此时分离因子与渗透通量预测值分别为9.47、77.57 g(m2 h)1,渗透侧乙醇浓度达到51.3%(wt)。回归方程的验证实验结果表明,回归方程的估计值与实验值较为吻合,可用于乙烯基封端的PDMS/PVDF复合膜的渗透汽化性能的预测与优化。