Adhesion of nylon-6 to triazine trithiol-treated metals during injection molding

Abstract —An examination was made of the adhesion of nylon-6 resin to treated metals such as phosphor bronze, brass plates, and electronickel platings during injection molding. No adhesion to any of these metals was noted to occur under ordinary injection molding conditions and an aqueous solution of 1,3,5-triazine-2,4,6-trithiol mononatrium (TTN) was thus used to induce adhesion. Following treatment with aqueous TTN solution under optimal conditions, nylon-6 adhered tightly to all the above metals under ordinary injection molding conditions. The TTN treatment led to the formation of surface films containing metal salts of 1,3,5-triazine-2,4,6-trithiol (TT). Conditions were made optimal with regard to time, temperature and TTN concentration. Adherent films were generally formed when bronze and brass were treated for short periods, at low temperature, and at low TTN concentration, although this was not the case with nickel plating. There was no adhesion to nickel plating even for a prolonged treatment time, high temperature, and high TTN concentration. Adherent and non-adherent films did not differ in the chemical structures of the metal salts of TT but they did differ in morphology. Good adhesion was noted in the case of TT-metal salts present at low density on the metal surface. Some films readily reacted with amino compounds under conditions similar to those generally used for the injection molding of nylon. The adhesion was concluded to be due to the formation of interfacial bonds during injection molding.     

The role of water in delamination in electronic packages: degradation of interfacial adhesion

Polymeric electronic packages subjected to standard Joint Electron Device Engineering Council (JEDEC) reliability testing are known to exhibit weakening and failures at the polymeric adhesive interfaces. Coupling agents are typically used as additives in epoxy-based materials to improve package reliability. Coupling agent chemistry and environment conditions, including pH, temperature and applied stress, are known factors that affect the rate of adhesion degradation and jeopardize the long-term reliability of the package. In this study, the subcritical interfacial debonding process is described. The debonding rates of polymers with silane, titanate and zirconate coupling agents were characterized at different temperatures by shear fracture tests and tapered double cantilever beam tests under mechanical loading and simultaneous exposure to controlled acidic environments. An analytical procedure was developed to delineate the material parameters governing adhesion degradation. Elevated temperature and acidity were shown to have a strong effect on package reliability, but mechanical loading was found to have a minimal effect on the rate of adhesion degradation. The effects of the JEDEC testing conditions on interfacial bond degradation are discussed using the chemical kinetic model.     

Different surface treatments to improve the adhesion of polypropylene

Injection-molded samples of polypropylene were exposed to oxygen plasma and SACO (SAndblasting and COating) treatments. The pretreated surfaces were successively adhesively bonded or lacquered. The adhesion strength and failure mode of these specimens were examined. The surfaces obtained after treatments were characterized by electron spectroscopy for chemical analysis (ESCA), contact angle measurements, and scanning electron microscopy (SEM). Both microroughness and chemical modification of the surface led to an increase in adhesion by up to a factor of 10. The stability of the surface changes generated during the plasma and SACO pretreatments was observed by different kinds of aging experiments in air and water. The aging of SACO-treated surfaces led to no significant change on the surface. In the case of plasma-treated surfaces, hydrophobic recovery during aging in air reduced the polarity of the surface layer. During aging in water, no hydrophobic recovery on the surface was observed.     

Temperature influence on the physicochemical surface properties and adhesion behaviour of Enterococcus faecalis to glass and silicone

The interest in studies on the physicochemical surface properties of bacteria has increased because they are related to the causes of the initial adhesion of microorganisms to biomaterials and the subsequent biofilm formation on indwelling medical devices. The determination of physicochemical parameters such as hydrophobicity or surface tension is usually done at room temperature, not taking into account the real temperature at which bacteria cause infection inside the human body. In this work, the influence of the experimental temperature on the surface physicochemical characteristics and adhesion behaviour of Enterococcus faecalis ATCC29212 to glass and silicone has been studied. Water, formamide and diiodomethane contact angles on bacterial lawns changed when the experimental temperature was increased from 22°C to 37°C. Moreover, hydrophobicity, as determined by water contact angle, increases with temperature, in agreement with the higher and lower adhesion to silicone and glass, respectively, observed at 37°C, with respect to the results at 22°C. Also, when the formamide and diiodomethane contact angles are considered, the changes in the adhesion behaviour to glass and silicone are predicted by the sum of Lifshitz-van der Waals and acid-base interaction free energies if the measurement temperature is the same as the bacterial growth temperature, i.e. 37°C.     

The aging effects of repeated oxygen plasma treatment on the surface rearrangement and adhesion of LDPE to aluminum

The effects of aging temperature and time on the adhesion properties of oxygen plasmatreated low-density polyethylene (LDPE) were investigated. As the aging temperature and time increased, surface rearrangement and the migration of molecules containing polar functional groups into the bulk were accelerated to the surface to form a hydrophobic surface. The adhesion strength of oxygen plasma-treated LDPE/aluminum joints was measured using a 90° peel test by varying the plasma treatment time and aging temperature. The adhesion strength was constant, regardless of the plasma treatment time. As the aging temperature increased, the adhesion strength of the LDPE/aluminum joints decreased and the locus of failure changed from cohesive to interfacial failure. It was also found that the polar functional groups buried in the bulk could be reoriented to the surface in a polar environment. This study also investigated whether repeated oxygen plasma treatment would increase the concentration of polar functional groups at the surface and reduce the surface rearrangement and the migration of molecules containing polar functional groups during aging. Contact angle measurements and X-ray photoelectron spectroscopy (XPS) showed that repeated oxygen plasma treatments increased the concentration of polar functional groups at the surface. However, the aging time between plasma treatments had a negligible effect on the concentration of polar functional groups at the surface.     

Study of adhesion forces and mechanical properties of human skin in vivo

In this work we have studied the effect of adhesion forces on the mechanical parameters between a spherical indenter and human skin surface with an indentation test. To take into account the effect of adhesion on Hertzian contact radius, pressure and strain, a theory of adhesion contact, like that of Johnson, Kendall and Roberts (JKR) or Derjaguin, Muller and Toporov (DMT) must be used. These theories correct the errors induced by the adhesion forces on contact parameters. The change in skin surface lipid film during hydration by water is assessed by analyzing the evolution of the adhesion energy and skin stiffness.     

Effect of ZnO contents at the surface of brass-plated steel cord on the adhesion property to rubber compound

An effect of ZnO concentration at the surface of brass-plated steel cord on the adhesion property between a rubber compound and a brass-plated steel cord was investigated. Cord composition was determined by an Auger microscope with Ar ion sputtering. Two different steel cords were prepared; one (cord A) had higher ZnO concentration at the cord surface compared to the other (cord B). Pull-out force of unaged adhesion sample of cord A was lower than that of cord B. But the adhesion durability of the humidity-aged adhesion sample of cord A was better than the latter. Rubber coverage of the pull out cord for the unaged adhesion samples of cord A was poor, indicating insufficient formation of an adhesion layer. Pull-out force of the thermal-aged adhesion samples decreased with increasing aging time and that of cord A was lower than that of cord B. The enhancement of rubber coverage during initial aging period could be explained by an additional formation of copper sulfide at the adhesion interphase and an increase of modulus of rubber compound adjacent to the adhesion layer. With further increases of aging time, adhesion interphase grew excessively and the physical property of rubber compound deteriorated significantly, such that rubber coverage of adhesion samples decreased markedly with increasing aging time.     

Bacterial adhesion to poly(vinyl chloride) films: Effect of chemical modification and water induced surface reconstruction

Escherichia coli (E. coli) and Staphyloccus aureus (S. aureus) bacteria adhesion to pure and modified poly(vinyl chloride) (PVC) was investigated through classical wettability measurements, captive bubble time dependent measurements, and static adhesion tests. Various chemical modifiers were studied, namely 4-mercaptophenol, 4-mercaptobenzylalcohol, 4-methoxybenzenethiol, 2-naphthalenethiol and 4-mercaptopyridine. The surface thermodynamics of the modified PVC films was investigated via the van Oss, Chaudhury and Good (vOCG) theory and an increase in the hydrophilic character was deduced from the increase of the contact angle of the air bubble in water with time of immersion. This is ascribed to a water induced surface reconstruction of the modified PVC surface. E. coli bacteria exhibit a hydrophilic character and strong adhesion, dependence on the nature of the PVC modifier as shown by the remaining attached bacteria. S. aureus which is hydrophobic showed no difference in its adhesion to pure or modified PVC. A slight increase in the adhesion of E. coli is observed with the water induced surface reconstruction. This work highlights the predominance of the hydrophilic/hydrophobic nature over the acid–base in the bacteria/polymer adhesion mechanism. It also provides, through chemical modification of PVC, a nice route to control the micro-organisms' adhesion to biomedical devices.     

Influence of glass mechanical strengthening on the adhesion properties of poly(vinyl butyral) films to a float glass surface

The effects of various methods of mechanical strengthening of glass on the adhesion properties of poly(vinyl butyral) (PVB) film to a float glass surface were investigated. The mechanisms of the influence of the strengthening processes on the adhesion properties were analyzed. The influence of different types of pretreatment of the glass surface on the adhesion of the polymer films was also considered. It was shown that ion-exchange strengthening followed by treatment with an alkaline water solution provided the best combination of high mechanical strength of glass and good adhesion of the PVB films to the glass surface. Metal-oxide coatings on float glass increased the mechanical strength of glass but decreased the adhesion strength between the polymer and glass. The adhesion of PVB to the metal-oxide layers was determined not only by the chemical composition of the layers, but also by the method of layers formation, the type of glass surface pretreatment, and the nature of the intermediate layer between the metal-oxide layer and the glass surface.     

Study on the interfacial interactions and adhesion behaviors of various polymer-metal interfaces in nano molding

This study focuses on investigating interfacial interactions and the adhesion mechanism of polymer-metal interfaces in nano-molding. Polyphenylene sulfide (PPS), polyamide 6 (PA6), and isotactic polypropylene (iPP) were chosen as candidate polymers, and aluminum (Al), and copper (Cu) were used as metal substrates. By establishing the metal matrix composed of a rectangular pit with length, width, and depth of 4.5, 4.5, and 2.0 nm, respectively, six paired polymer-metal interfacial systems in a cuboid of 7.5 × 7.5 × 11.5 nm, consisting of metal, polymer, and vacuum layer (from bottom to top) were constructed. Molecular dynamics simulations were performed to calculate interfacial interactions and bonding processes. Results showed that wall-slip behavior was pronounced in nano-molding. Viscoelasticity and polarity of the polymers played a crucial role in interfacial interactions, which guided the wall-slip behavior and greatly affected the bolt performance. PA6 and PPS were more suitable for molding than iPP on both Al and Cu substrates. PA6 showed the best filling and bonding performances, followed by PPS, while iPP revealed the poorest performances. The Cu substrate exhibited better anchor strength and filling rate than Al substrates with the same polymer.     

An analytical approach for the adhesion of a semi-infinite elastic body in contact with a sinusoidal rigid surface under zero external pressure

An analytical approach for the adhesion of a semi-infinite elastic body in contact with a sinusoidal rigid surface under zero external pressure is presented. Although Johnson (Int. J. Solids Struct. 32, 423 (1995)) has proposed an analytical solution for a slightly wavy surface, while Zilberman and Persson (Solid State Commun. 123, 173 (2002); J. Chem. Phys. 118, 6473 (2003)) have given a numerical solution for a highly wavy surface by considering the curvature of the contact area in the calculation of the interfacial term of the total energy, our solution is not only for small amplitude of roughness (i.e., the slightly wavy surface as Johnson's) but also for large amplitude of roughness (i.e., the highly wavy surface as of Zilberman and Persson). Our solution considers the curvature of the contact area as do Zilberman and Persson. Our results which are obtained for the total energy and equilibrium condition of the system agree with both Johnson's and Zilberman and Persson's results. The effects of the material constants and the surface roughness on the adhesion are clearly expressed and discussed.     

Studying surface charge and suspension stability of hydroxyapatite powder in isopropyl alcohol to prepare stable suspension for electrophoretic deposition

Abstract

Suspension stability of hydroxyapatite powder in isopropyl alcohol was investigated by measuring zeta potential. In this study, isopropyl alcohol was used as a suspension media, and nitric acid, polyvinyl butyral and polyethylenimine were the dispersing agents. Fine grain particles with mean particle size and surface area of 2·54 μm and 5·8 m² g^?1 respectively, were prepared. Stable suspensions were made by mixing 40 g L^?1 milled powders in isopropyl alcohol. The zeta potential of the suspensions was measured by using zeta sizer equipment. The results showed that by adding nitric acid and polyvinyl butyral to the system, negative charge was introduced, while polyethylenimine donated positive charge to the surface of particles and induced electrostatic and steric stabilisation. It was concluded that the suspension which was stabilised with 4 g L^?1 polyethylenimine revealed the highest zeta potential and stability which is suitable for cathodic electrophoretic deposition.     

轿车子午线轮胎带束层胶高硫黄-钴盐粘合体系的研究

研究高硫黄-钴盐粘合体系在轿车子午线轮胎带束层胶中的应用。试验结果表明,在轿车子午线轮胎带束层胶中采用高硫黄-钴盐粘合体系,可以提高硫化胶的200％和300％定伸应力及拉伸强度,保持硫化胶与钢丝帘线的粘合性能,提高硫化胶的动态力学性能及成品轮胎的高速性能和耐久性能,降低生产成本,改善作业环境。     

Water-based chlorination treatment of SBS rubber soles to improve their adhesion to waterborne polyurethane adhesives in the footwear industry

Solutions of trichloroisocyanuric acid (TCI) in different organic solvents are commonly employed in the footwear industry to improve the adhesion of SBS (styrene-butadiene-styrene) rubber soles to polyurethane adhesive. To avoid the use of organic solvents in the chlorinating solutions, several water-based chlorinating treatments were investigated in this study: (i) inorganic chlorine compounds (HCl-acidified sodium hypochlorite solution; free active chlorine (FAC) = 47.8 g/l); (ii) organic chlorine donors (aqueous solution of 3 wt% TCI/H₂O, and ethanol solutions of 3 wt% HD (1,3-dichloro-5,5-dimethylhydantoine), or NCS (N-chlorosuccinimide); (iii) organic chlorine donor salts (aqueous solutions containing 3 wt% DCI (sodium dichloro isocyanurate), CB (chloramine B, N-chloro-sodium-phenylsulphenamide), or CT (chloramine T, N-chloro-sodium-p-toluenesulphenamide). The surface modifications produced by treatment of SBS rubber with the aqueous chlorinating agents were compared with those obtained by using the current solvent-based chlorinating treatment (3 wt% TCI/MEK). The FAC concentration and the chlorine stability in the solutions were determined by iodine titration, and the SBS rubber surface pH was determined with a flat pH probe. The surface modifications on the SBS rubber were analyzed by ATR-IR spectroscopy, XPS, contact-angle measurements and SEM. The adhesion properties were evaluated by T-peel strength tests on treated SBS rubber/waterborne polyurethane adhesive/roughened leather joints. The failed surfaces obtained after peel tests were analyzed by ATR-IR spectroscopy to precisely assess the locus of failure of the adhesive joints. The nature of the modifications produced on the SBS rubber surface depended on the chlorinating system used, the SBS rubber surface pH value, and the free active chlorine concentration of the chlorinating solution. The most effective chlorinating agents were TCI/H₂O and HD/EtOH, but they were not stable over time due to quick chlorine evolution. Treatment with NaClO/HCl and DCI/H₂O provided acceptable adhesive strength values although there was fast chlorine evolution in the NaClO/HCl solution; the free active chlorine concentration in the DCI/H₂O solution was stable for at least 4 days after preparation. Finally, the treatment with NCS/EtOH, CB/H₂O and CT/H₂O did not chemically modify the SBS rubber surface, so the adhesion to polyurethane adhesive was not improved.     

Assessing distribution of nanosmears due to mutual interaction of additives in high shear mixing of pharmaceutical blends

The objective of this study was to investigate the mutual interaction behavior of magnesium stearate (MgSt) and colloidal silica (CS) affecting their smear coating phenomena on excipient and active ingredient particles during shear mixing of pharmaceutical blends. Multiple pharmaceutical blends were processed in a v-blender under high shear condition by simultaneously varying the mixing orders of blends and concentration of additives. Uniformity of smeared patterns of additives was found to be affected by the physical and chemical nature of excipient surfaces. Although, an increase in concentration of lubricant in the formulation increased the amount of smeared lubricant coating on surrounding particles, the hydrophobic behavior was found to be predominantly dependent upon the order of mixing of constituent components of additives. More interestingly, prior mixing of the blend with MgSt followed by other components although increased the smearing area, surprisingly decreased the hydrophobic behavior, indicating a strong interaction parametric effect of MgSt with CS. For the first time, this work successfully demonstrated the limits of additive concentration in the blends governing the smearing at nanoscale. A phenomenal increase in nanosmearing area of CS compared to MgSt also prolonged the dissolution of tablets, indicating a strong interaction effect of both additives at nanoscale.     

软岩地层露天开采地表移动分析

通过建立Fuzzy测度模型,推导出软岩地层露天开采地表下沉和水平移动计算公式,并利用该模型对软岩地层露天开采地表移动的实例进行了分析,理论预测结果与实测数据相吻合,满足工程需要.     

Study of siloxane additives migration to the surface of polyester-(melamine)-polyurethane coatings: Aging effects after ethanol cleaning

This study determines the influences of siloxane flow agents’ migration on the outermost surface composition of clearcoats, before and after ethanol cleaning. This evaluation is undertaken to improve adhesion of pressure-sensitive adhesives (PSAs) on automotive paint systems. Most of the siloxane flow agents segregate from the bulk to the clearcoat outermost surface during curing. These additives can cover until 50% of the surface area but X-ray photoelectron spectroscopy (XPS) and time of flight-secondary ion mass spectrometry (ToF-SIMS) analyses indicate that they can be removed by ethanol cleaning. Composition of the cleaned clearcoats surfaces are similar as the composition of clearcoat formulated without siloxane additives: the polyester-(melamine)-polyurethane network is more detected than before cleaning. However, outermost surface analyses show that several aging weeks increase the siloxane additives segregation. This post-cleaning migration modifies the clearcoat surface composition and cancels the chemical modifications due to the ethanol cleaning. XPS analyses show that silicon concentrations after cleaning and aging are inversely proportional to the initial silicon concentrations measured after curing. It highlights that aging has to be controlled to improve adhesion of PSAs on clearcoats. A second ethanol cleaning on aged clearcoats is not effective to remove these new siloxane additives. Their formulation should be different from the flow agents and it could modify their solubility in ethanol. This result could also indicate that these new siloxane additives are not located on the last molecular layer of surface and they would not be soluble in ethanol.     

Imaging in evaluation of polymer coatings adhesion to glass at high humidity

Adhesion reduction occurring after polymer coated glass was immersed in water was studied in a variety of UV-cured urethane acrylate coatings containing alkyloxysilane adhesion promoting additives. It was observed that water accumulated under the coating surface in drops and formed ‘blisters’ in the glass-polymer interface. A non-destructive imaging technique was developed to measure the average size of the water blisters. The size of the water blisters within the interface was correlated with the wet adhesion force measured by coating resistance to 180° peel. The force of coating resistance to 180° peel off glass surface decreased non-linearly with the increase of the average size of the water blisters. It was concluded that the decrease in adhesion between the coating and glass was a result of stretching and breaking of the silane bridging bonds and polymer fibrils by water condensing on the glass surface within the polymer-glass interface. The mathematical model relating coating wet peel resistance force with the size of the debonding produced by water accumulation was presented.     

Investigating the change in surface acoustic wave velocity due to the change in adhesion of a SU-8 thin film using a SU-8/AlN/Si SAW sensor

This study investigates the change in surface acoustic wave (SAW) phase velocity due to the change in adhesion of a SU-8 thin film using an Aluminum Nitride (AlN)/Silicon (Si) SAW sensor. The variation in the stress field at the SU-8/AlN interface at different levels of SU-8 adhesion is also investigated and correlated to the change in SAW phase velocity. A theoretical model is developed to determine the change in wave dispersion profile due to the change in adhesion of the SU-8 film on the surface of the AlN/Si sensor. The interface of the SU-8/AlN layers is represented by a layer of massless springs with interface stiffness K (N/m³). The results illustrate that as the adhesion of the SU-8 film weakens on the surface of the AlN/Si SAW sensor the velocity dispersion profiles fluctuate. The calculated stress field at the SU-8/AlN interface also fluctuates because the weakened interface cannot sustain the increased stress due to the confinement of the wave near the interface. Therefore, the mode of wave propagation varies between the perfect bond case where the SU-8 layer is perfectly bonded to the AlN/Si surface and when the SU-8 is completely de-bonded. Four SAW sensor designs operating in the frequency range of 84–208 MHz are developed to measure the shift in the center frequency values and the corresponding change in SAW phase velocities due to the change in adhesion of the SU-8 layer. The adhesion of the SU-8 film on the surface of the AlN/Si SAW sensor is changed by using different adhesion layers. The adhesion layers used are a gold film and an omnicoat coated gold film. Omnicoat is an adhesion promoter used to improve the adhesion of SU-8. The results illustrate that as the adhesion of the SU-8 film improves for the sensors with omnicoat the wave velocity shifts to a lower value. The wave velocity values are fitted with the wave dispersion profiles for different values of the interface spring stiffness K. The interface spring stiffness values for the SAW sensors with omnicoat coated gold and gold films are 8.1×10⁹ N/m³ and 7.95×10⁹ N/m³, respectively. The use of omnicoat improves the adhesion of the SU-8 film and corresponds to a higher interface spring stiffness value. The stress and displacement fields generated in the SU-8 layer for different values of the interface spring stiffness K are plotted. The results illustrate that as the adhesion of the SU-8 layer improves the stress transmitted to the SU-8 layer increases and the wave is more confined in the SU-8 layer, which justifies the drop in wave velocity since the Rayleigh wave velocity in SU-8 is much lower in comparison to AlN and Silicon; 1166, 5600, 5000 m/s, respectively.     

Use of the scratch test to measure changes in adhesion of Cr/Al2O3 due to ion beam mixing

The scratch test is widely used to measure the adhesion of thin films to their substrates. The adhesion improvement with ion beam mixing is difficult to quantify, however, because the mixing process itself introduces changes into the system that affect the measurement of adhesion by the scratch test. This paper described the effect of ion beam mixing on the test parameters and analyzes the results of tests on ion bombarded chromium films on sapphire substrates. The measured force to remove the Cr film increased by more than 1900% due to the ion beam treatment. Changes in the system parameters account for an increase of less than 5%, leading to the conclusion that the ion beam treatment caused a major increase in the bond strength.