Hydrolysis Of Silane Coupling Agent Research Articles

Preparation and characterization of sodium polyacrylate grafted montmorillonite nanocomposite for the adsorption of cadmium ions form aqueous solution

High-efficiency adsorbents made from clay minerals have a wide application in remediation of soil and water pollution, especially in the treatment of refractory and highly toxic heavy metals. Montmorillonite itself has a good adsorption capacity and a large modification space for its layered structure. Therefore, carboxylate polymer grafted montmorillonite was developed to improve the adsorption capacity of heavy metals in this paper. Two kinds of modified preparation routes were compared, and a series of batch adsorption tests were conducted to evaluate the influence degree of parameters (contact time, pH, temperature, and cadmium concentration). The structural changes of montmorillonite samples before and after modification were characterized by a series of microscopic analyses and measurement techniques. The results show that the silicon hydroxyl produced by the hydrolysis of silane coupling agent can indeed be grafted by dehydration condensation with Si/Al-OH on clay surface. The grafting chain can be greatly increased by C=C double bond breaking polymerization. The polycarboxylate group can effectively improve the adsorption performance of modified montmorillonite for cadmium ions. The maximum adsorption capacity of modified montmorillonite increased by about 224.75%, reaching 63.49 mg/g. The adsorption model of montmorillonite conforms to Langmuir monolayer adsorption model, while modified montmorillonite samples exhibit Freundlich adsorption model and S-type isothermal adsorption curve characteristics of resin. The preparation method of neutralizing after polymerization of acrylic acid was proposed to be better, which provides technical guidance for scientific and efficient application.

Influence of surface modification on thermal, adhesive properties and impact behavior of TPU films for laminated glass

Abstract The poor adhesion of TPU films limits their extensive application in lightweight laminated glass (LLG). A simple and effective method is reported in this paper to obtain modified TPU films by silane coupling agent (SCA) treatment. The polar groups (such as urethane groups, carboxyl groups, etc.) on the surface of TPU films reacted chemically with the reactive groups of SCA. Meanwhile, hydrogen bonds were formed between the silicon hydroxyl groups generated by the hydrolysis of SCA. Therefore, the adhesivity and thermal stability of TPU films were improved. Moreover, the surface of TPU films became rough after modification, hence the interfacial bonding area between TPU film and glass increased, which furthered the bonding effect of TPU film with glass plate. Compared with unmodified TPU films, the tensile shear bond strength (TSBS) of modified TPU films increased by nearly 28%, and the initial decomposition temperature increased from 277 °C to a maximum of 295.3 °C. The impact resistance of LLG was significantly improved due to the improvement of the adhesivity of TPU film.

Effect of adding different silane coupling agents on metal friction and wear in mixing process

AbstractThe function of silane coupling agent in rubber mixing field is to combine inorganic matrix with rubber organic matrix. Silica is commonly used in the rubber mixing field to strengthen rubber. The size and amount of silica aggregates in the mixing process are important factors affecting the wear of the mixing chamber. The wear of the mixing chamber would lead to a increasing gap between the mixer chamber and the rotor, which caused the mixing efficiency reducing. It also affected the dispersion effect, then affected the mechanical and physical properties of the vulcanized rubber. In this paper, the effects of rubber compound on metal friction and wear were studied by using four silane coupling agents commonly used in rubber mixing field. The experiment was carried out at 15°C, and the attention should be paid to drying during sample preparation to avoid the deviation of the experiment caused by hydrolysis of silane coupling agent. The results showed that silanization reaction occured between silica and silane coupling agent in the mixing process. The mixing temperature was usually maintained at 145 to 155°C for 1 min in the mixer, and the silanization reaction rate was the fastest during this time. We took this rubber compound as the research object and studied the friction and wear of the rubber compound on the mixing chamber in the mixing process. The products of the silylation reaction are alcohol and water. This paper studies the corrosion and abrasion of the mixing chamber by water at high temperatures. In the mixing process, abrasive wear was the main wear form, but the corrosion wear caused by high temperature steam still occupied a large proportion.

The effect of additional photochemical treatments on the bonding of silanized CAD/CAM ceramic restorations after water-storage.

The development of dental CAD/CAM system has made metal-free ceramic restorations more available to patients. Silane coupling treatment is an essential clinical process to achieve reliable and good adhesion with silica-based indirect restoratives. However, long-term water-storage causes the hydrolysis of silane coupling agents and decreases the bond strength. The aim of this study was to examine the effect of additional treatments including photochemical treatments on silane coupling performance in ceramic restorations. The influence of water-storage periods (1d: one day, 1m: one month, and 3m: three months) for the silanized surface of CAD/CAM ceramic restorations was also investigated. In addition, bonding reliability was evaluated as a qualitative measure in order to characterize the bond strength of CAD/CAM restorations. The micro-tensile bond strength (μ-TBS) was measured to explore the benefits of additional photochemical treatments (UV: ultraviolet and VL: visible light irradiations) on silanized surfaces, compared to non-additional treated (CO) and dry heating (DR) conditions. In the CO specimens, μ-TBS decreased in the order of 1d > 1m > 3m. However, in DR, UV, and VL additional treatments, no significant differences could be observed in the 1d, 1m, and 3m groups. The Weibull modulus and 10% failure probability values of the UV and VL specimens were inclined to be significantly greater than those of CO specimens, regardless of the water-storage period. These findings reveal that additional photochemical treatments had a successful effect to improve the bond strength and bonding reliability of the CAD/CAM restorations, when compared to CO and DR conditions.

Superhydrophobic conjugated microporous polymers grafted silica microspheres for liquid chromatographic separation

Vigorously developing new high performance liquid chromatography (HPLC) stationary phases to meet the versatile separation requirements is still an important issue in the field of analytical chemistry. Conjugated microporous polymers (CMPs) are a new type of three-dimensional network porous material with high specific surface area, good chemical stability and superhydrophobicity. Herein, we firstly report the synthesis and applications of CMPs@SiO2 material for HPLC stationary phase. The CMPs@SiO2 material can be in situ fabricated via Sonogashira coupling of 1,3,5-triethynylbenzene and 1,4-diiodobenzene on the surface of spherical silica. The morphology and physicochemical properties of the synthesized stationary phase material were investigated by a series of characterization methods. Due to the superhydrophobic nature of the CMPs@SiO2 material, the packed CMPs@SiO2 HPLC column displays ultrastrong chromatographic retention and can be used for separation of both hydrophobic and hydrophilic compounds with good selectivity. Significantly, CMPs@SiO2 column can be performed for separation with pure acetonitrile as the eluent. Thus, the new column was successfully exploited for monitor and analysis of the hydrolysis of silane coupling agents. Furthermore, based on its oleophilicity, this report firstly utilized the CMPs@SiO2 material to identify and analyze the quality of cooking oils through one-step enrichment and subsequent HPLC separation. We will further exploit to fabricate versatile CMPs-based stationary phases, highlighting their potential applications in different separation scopes.

Preparation and Application of the Hydrophilic Amino-Silicone Softener by Emulsion Polymerization

The amino poly-siloxane was modified with self-made polyether silicones by the crafts of emulsion polymerization. We studied the emulsifier, the dosage of emulsifier initiator, polyether/silane coupling agent, pH value. There are some results of the research indicated in the following. First, there are many factors for the hydrophilic amino-silicone softener both on the polymerization process and the performance, such as the proportion and amount of emulsifier, initiator dosage, the mass ratio of the polyether and hydrogen silicone oil, the choice of silicone coupling agent, and the ratio and dosage of polyether silicones silane coupling agent. Second, the amount of hydrogen of the hydrogen silicones and the choice of catalyst are the key points on the synthesis of polyether silicones. The amount of hydrogen should be low and the catalyst must be economical and efficient and its introduction should be small and times, other more the holding time is not too long. The next one is that, in the process of hydrolysis of silane coupling agent, we need some acid to adjust pH value, or they will be broken down. The most important one but not the last is that the epoxy group can improve the products low-temperature supple and the persistence of the finishing fabric, furthermore it can reduce yellowing and has a good stability of the inorganic salt, however, it will be destroyed if the reaction temperature for epoxy is too high. What’s more, it is very economical and environmental that the process of emulsion is simple and with less emulsifier.

Surface Hydrophilic Modification of Polypropylene Fiber by Hydrolysis of Silane Coupling Agent

Silane coupling agent is applied to modify polypropylene fiber. The modification effectively transfers the hydrophobic surface of polypropylene fiber to hydrophilic surface. Results from FT-IR, SEM and contact angle meter suggest that that the surface functional groups, the morphology and hydrophilia of polypropylene fiber is changed during the hydrolysis reactions of silane coupling agent. The modification process not only improve the surface hydrophilia of polypropylene fiber, but also convert the smooth surface of unmodified fibers to rough surface of modified fibers which gives stronger interface bonding force between fiber and substrate in the field of composite applications.

Decay-like fracture mechanism of silicone rubber composite insulator

In recent years, a new kind of abnormal fracture phenomena of composite insulator occurred in high voltage transmission lines in several countries, which was totally different from brittle fracture and normal fracture. According to the general characteristic features of the fracture, this type of failure was named decay-like fracture of composite insulator by the author. In this paper, a decay-like fractured composite insulator was investigated and microscopic physic-chemical properties of decay-like fractured Fiber Reinforced Plastic (FRP) core rod were analyzed. Scanning Electron Microscope (SEM), Thermal Gravimetric Analysis (TGA) and Fourier Transform Infrared (FTIR) Spectroscopy methods were employed to explain the microscopic morphology characteristics and chemical component changes of decay-like fractured composite insulator, and to further explain the reasons for the name of decay-like fracture in terms of crisp and decay-like. The main microscopic feature of decay-like fracture is the degradation and deterioration of the epoxy resin matrix in FRP rod. The mechanism of decay-like fracture of composite insulator could be summarized as follows. Due to the liquids penetration into the sheath-core interface, hydrolysis of silane coupling agent with bad quality leads to poor adhesion strength and interface voids, which results in distortion of electric field at the sheath-core interface. Under the combined action of damp condition and high electric field, discharge and current appear along the FRP rod surface. Epoxy resin matrix is eroded in the presence of discharge and current, and then is soften, melt, evaporated. Meanwhile, ion-exchange and hydrolysis process happen between glass fibers under the combined action of mechanical stress and nitric acid produced by discharge in the presence of moisture. Fiber-resin interface in FRP rod is separated owing to the erosion of epoxy resin. The degradation direction of the decay-like fracture is from outside to inside of FRP rod, and the interface between silicone rubber sheath and FRP rod is confirmed to be the initial deterioration area of the decay-like fracture. The criterion to distinguish the differences between the decay-like fracture, brittle fracture and normal fracture depends on whether the epoxy resin matrix is degraded and deteriorated or not.

Plasma induced surface coating on carbon nanotube bundles to fabricate natural rubber nanocomposites

Carbon nanotube bundles (CNTB) with one-dimensional orientation arrangement structure were grafted a layer of polyacrylic acid (PAA) through plasma induced polymer grafting in this study. Thus, we blended these modified CNTB (CNTB-PAA) into natural rubber (NR) matrix through the silane in-situ modification-dispersion technique achieved by mechanical blending method. In this process, carboxyl groups in large quantities distributed in the surface of CNTB-PAA could be subjected to dealcoholization reaction with silicon hydroxyl (Si-OH) generated from the hydrolysis of silane coupling agent (Si69), and a single sulfur bond of Si69, meanwhile, could participate in the curing reaction of rubber. The ultimate nanocomposites had a significantly decreased network effect of fillers and an improved interfacial bonding between CNTB and rubber matrix. The tensile and dynamic-mechanical tests revealed a strong enhancement in the tensile stress and a marked reduction in the dynamic hysteresis loss of the nanocomposites.

Raman studies of the hydrolysis of silane coupling agents

Raman spectroscopy has been used to characterize silane coupling agents in the bulk, in aqueous solution and on glass fiber surfaces. The state of hydrolysis of the coupling agent can be verified and the kinetics of the hydrolysis followed with Raman spectroscopy. Unhydrolyzed silanes can be detected on glass surfaces when the coating process is carried out at a stage when the hydrolysis is incomplete.

Glass‐Catalyzed hydrolysis of silane coupling agents

AbstractSilane coupling agents containing organo‐functional and alkoxy groups are applied to glass fiber reinforcements from an acid solution commercially. It is found that finely divided soda glass suspended in a methanol‐water solution of various silanes promotes hydrolysis without the presence of an acid catalyst. When acid is present in addition to the glass, as in commercial application baths, rate of hydrolysis is lower than with either acid or glass alone. There is evidence that basic glass components catalyze hydrolysis. Further work under commercial application conditions is indicated.