Addition of Silica to Polyurethane Adhesives

The influence of the addition of silica (Aerosil-200) (5-25 wt%) to polyurethane adhesives on their adhesion properties with non-chlorinated and surface-chlorinated rubbers has been studied. The chlorinating agent was Trichloroisocyanuric acid (TIC) in 2-butanone solution at a concentration of between 1 and 9 wt%. In general, silica produced an increase in the adhesive viscosity and an improvement of green (immediate) peel strength (especially with chlorinated rubber). The best results were obtained for a silica content of 10-20 wt%. However, the addition of silica did not improve the peel strength after a thermal ageing process. Polyurethane adhesives containing silica undergo an improvement in their resistance to degradation by chlorine on the rubber surface. On the other hand, the chlorination of silica produces the rupture of Si-O bonds and the formation of Si-H and Si-Cl groups. Furthermore, the stirring speed (directly related to the dispersion) of silica into the adhesive is an important parameter which affects the viscosity and peel strength. A stirring speed of 1000 rpm gives the best silica dispersion.     

Hydrophobic or Hydrophilic Fumed Silica as Filler of Polyurethane Adhesives

Two hydrophilic and two hydrophobic fumed silicas of different characteristics were added to solvent-based polyurethane adhesives (PU). IR spectroscopy, contact angle measurements and rheology (viscosity measurements, determination of viscoelastic properties) were used to monitor the variation of properties of PU adhesives produced by addition of silica. Immediate (green) adhesion was determined by T-peel testing of halogenated synthetic rubber/PU adhesive/halogenated synthetic rubber joints. Silica addition produced a noticeable increase in the PU adhesive viscosity which can be related to the variation of viscoelastic properties. Viscosity of PU adhesives containing hydrophilic silica slightly increased with time after preparation; the increase was less significant in PU adhesives with hydrophilic silica. In the rheological studies, silica imparted shear thinning and negative thixotropy to PU adhesives due to a better dispersion of the silica in the polyurethane during shearing. The addition of silica produces an increase in the storage modulus (G') of PU adhesives, the values obtained being independent of the hydrophilic or hydrophobic nature of the fumed silica. The increase of G' and the changes in tan δ of PU adhesives containing silica corresponded to an improvement in the green adhesion properties of chlorinated rubber/PU adhesive/chlorinated rubber joints. In general, in disagreement with previous results,¹ the presence of silica did affect the properties of solvent-based PU adhesives, but these properties were not dependent on the type of silica (hydrophobic or hydrophilic) used in this study.     

Comparison of the Properties of Polyurethane Adhesives Containing Fumed Silica or Sepiolite as Filler

Fumed silica is a well-known mineral filler of epoxy and polyurethane adhesives. Although effective, the small particle size and the relative high cost of fumed silicas suggest the need for an alternative filler. In this study, the usefulness of adding a natural hydrated magnesium silicate (sepiolite) as a new filler in solvent-based polyurethane (PU) adhesive formulations has been demonstrated. The rheological and adhesion performance of the sepiolite-filled PU adhesive was compared with that in PU adhesives containing fumed silicas. The addition of a filler to PU adhesives provided an increase in viscosity, imparted thixotropy and pseudoplasticity to the adhesive solution, produced an increase in storage and loss moduli, and improved the rheology of the PU. The mechanical properties of adhesive films were increased by adding filler, mainly with fumed silica. On the other hand, the immediate T-peel strength of roughened or (roughened + chlorinated) styrene-butadiene rubber/PU adhesive joints was greatly improved in filled PU adhesives. The effects produced by adding sepiolite or fumed silica to the adhesives were very similar, although in general more noticeable in fumed silica filled PU due to the formation of hydrogen bonds between the filler and the solvent and/or the polyurethane (in sepiolite-filled adhesives, van der Waals forces seemed to be responsible for the interactions between the filler and the solvent and/or polyurethane).     

阴离子型水性聚氨酯胶粘剂的合成研究

文章以二异氰酸醣、聚醚二元醇、二羟甲基丙酸（DMPA）等为基本原料制备了一种稳定的聚醚型阴离子水性聚氨酯胶粘剂,分析了水性聚氨酯胶粘剂的制备条件、催化剂用量、增稠剂等因素对水性聚氨酯胶粘剂乳液、胶膜及剥离强度的影响。     

Study of Properties of One-Component Moisture-Curable Polyurethane and Silane Modified Polyurethane Adhesives

Abstract

In this paper, the curing behavior and adhesion properties of five kinds of polyurethane (PU) and silane modified polyurethane (SPU) adhesives were studied. Fourier transform infrared spectra showed that the adhesive Sikaflex-555 had an SPU structure and that the other four adhesives were one-component polyurethanes. The experimental results of curing behavior show that the tack-free times and curing rates of these adhesives were significantly affected by the relative humidity and the temperature. The adhesion of the SPU adhesive to glass sheet, zinc galvanized steel sheet and steel sheet was much better than that of PU adhesives. The tack-free times and curing rates of all the adhesives was measured during the 12 months of storage.     

木材溶液制备聚氨酯胶粘剂的研究

研究了以苯甲基化木材溶液代替聚醚多元醇制备了聚氨酯胶粘剂，讨论了异氰酸酯用量、聚乙二醇用量、增塑剂用量及固化时间等对胶粘剂性能的影响，并获得了最佳的工艺条件。     

蓖麻油基多元醇改性聚氨酯胶黏剂的研究

以绿色可再生的蓖麻油(CO)和甘油为原料进行酯交换,然后将其产物(P-CO)与六氢苯酐(HHPA)进行酯化反应制备了蓖麻油基多元醇(P-HHPA-CO),将P-HHPA-CO和甘油代替传统的石油类多元醇,与异氟尔酮二异氰酸酯(IPDI)在无催化剂条件下合成了环保型脂肪族聚氨酯胶黏剂,并对不同NCO/OH摩尔比制备的聚氨酯胶黏剂涂膜进行了热重分析、差示扫描量热分析、拉伸力学性能测试、剥离及剪切强度测试。结果表明,制得的P-HHPACO羟值为219mg KOH/g;当摩尔比为1.3时,聚氨酯胶黏剂涂膜的T剥离强度达到399.2N/m;摩尔比为1.5时,剪切强度达到7.1N/mm²。     

鞋用水性聚氨酯胶粘剂制备及性能研究

作者通过复合的方法,制备了一种鞋用水性聚氨酯胶粘剂,并对该样品进行剥离强度、耐热、耐黄变、耐水解等一系列测试。测试结果表明,通过此方法制备的水性聚氨酯胶粘剂,其各项性能均已达到市场同类产品水平,在鞋厂具有一定的推广意义和研究意义。     

Nano-SiO_2/PU胶黏剂的制备及性能研究

文章采用硅烷偶联剂(KH550、KH560和KH570)改性纳米SiO2,并利用超声设备将其分散在聚醚二醇中,再加入TDI进行预聚反应,得到-NCO封端的预聚体。利用二乙烯三胺扩链得到A组分,加入固化剂B组分,制得醇溶型纳米SiO2/PU胶黏剂。并对改性后的胶黏剂进行了微观结构分析和性能测试。测试结果表明:经偶联剂改性后的纳米SiO2能够与聚氨酯达到很好的纳米尺度的复合,且掺杂SiO2后的聚氨酯胶黏剂剪切强度和耐水性进一步提高。     

Chemical Functionalization and Dispersion of Carbon Nanofibers in Waterborne Polyurethane Adhesives

Waterborne polyurethane adhesives (WBPU) reinforced with carbon nanofibers (CNFs), to make them also conductive to static electricity, were prepared and their properties were evaluated as a function of content (0.1–1 wt%). The incorporation of carbon nanofibers to waterborne polyurethane adhesives implies a great difficulty because of their tendency to form aggregates, which prevents an efficient dispersion. In this sense, it is necessary to insert functional groups on the surface of the nanofibers to improve their interaction with any polymer. In this research, the surfaces of carbon nanofibers were previously oxygenated by chemical functionalization to enhance their stability in waterborne polyurethane adhesives. The obtained results showed that the chemical treatment used to functionalize the carbon nanofillers was adequate, as well as the experimental procedure carried out for their incorporation into the polyurethane, since stable dispersions were obtained. Moreover, the addition of the nanofibers to the waterborne polyurethanes contributed to improving their rheological and viscoelastic properties, imparting an increase in the viscosity and changes in the crystallisation kinetics.     

湿固化聚氨酯热熔胶的研究近况及展望

叙述了湿固化聚氨酯热熔胶的特点、应用,重点介绍了它的主要组成及性能和近年来湿固化聚氨酯热熔胶的研究成果,并展望了其发展趋势。     

耐蒸煮软包装用聚氨酯胶黏剂的研制

耐蒸煮软包装用聚氨酯胶黏剂应用于制备需高温杀菌蒸煮的食品包装袋.为了满足耐蒸煮要求,提高胶黏剂的耐高温性、耐水解性,对胶黏剂的分子结构进行设计.通过环氧树脂与聚氨酯形成互穿网络结构,并在分子链中引入噁唑烷酮基团,提高了热稳定性;硅烷偶联剂的加入,提高了耐湿热粘接强度;所得胶黏剂与性能完全超过GB/F 10004-1998耐蒸煮复合膜、袋的要求(PA/CPP蒸煮前剥离力≥5.0N/15mm,蒸煮后剥离力≥4.0N/15mm),与日本同类产品性能相当.     

Polyester Polyol-Based Polyurethane Adhesive; Effect of Treatment on Rubber Surface

Polyester polyols were synthesized using vegetable oil fatty acids having different characteristics (mainly in terms of hydroxyl functionality) and epoxy resin, using triethylamine as a catalyst. Polyols were characterized by the FTIR spectroscopy. Polyurethane adhesives were synthesized from it and used in bonding rubber. Treatment of sulphuric acid on the non-polar styrene butadiene rubber (SBR) surface was studied for the bond strength improvement via an increase in wettability of the rubber surface. Wettability was found by measuring the contact angle using Goniometer. Bond strength was evaluated by a 180° T-peel test. The surface modification and mode of bond failure were studied by Scanning Electron Microscopy (SEM). The synthesized polyurethane adhesives were compared with the commercial adhesive.     

MEK wiping prior to chlorination to improve the adhesion of vulcanized SBR rubber containing paraffin wax

In this study, it was shown that the degree of effectiveness produced by halogenation with trichloroisocyanuric acid (TCI) was influenced by previous methyl ethyl ketone (MEK) wiping of a synthetic vulcanized styrene-butadiene rubber (R2) surface. The MEK wiping of the R2 rubber surface prior to chlorination with TCI removed the paraffin wax layer from the surface, which favoured the chlorination and oxidation reactions of the rubber. Chlorination with TCI decreased the contact angle values (increased the wettability) mainly due to the creation of C–Cl and C=O moieties, as well as roughness. The amount of these chemical moieties increased when the MEK wiping was applied prior to chlorination, so higher degrees of chlorination and oxidation were obtained on the R2 rubber surface. T-peel strength values increased more markedly if the MEK wiping was carried out before chlorination with TCI, in agreement with the higher degree of modifications produced in the R2 rubber surface. In fact, a cohesive failure in the R2 rubber was obtained in the adhesive joint produced with MEK wiped + TCI chlorinated R2 rubber.     

Studies on adhesion of polyethylene. Part I. Influence of functionality and phase transfer catalyst

Low-density polyethylene (LDPE) has been oxidized using phase transferred permanganate as an oxidant. The resulting surface modifications have been characterized by different methods and the consequent adhesion promotion has been characterized in terms of contact angle and peel strength measurements. From contact angle measurements using water and formamide liquid drops, reversible work of adhesion, and thence γ^p _s and γ-^d _s, the contributions of polar and dispersion components, respectively, have been calculated. The polar contributions increased in each oxidized LDPE relative to untreated LDPE and the surface energies also increased appreciably. The adhesion strengths between aluminium and untreated LDPE, as well as those between aluminium and oxidized LDPEs, have been examined by peel strength measurements. We found that the adhesion strength increased about 8-28 times in the case of oxidized LDPEs. Maximum strength was observed when benzyl triphenyl phosphonium permanganate was the oxidant. Both the peel force and the thermodynamic work of adhesion increase sharply with an increase in the carboxyl content, the total number of oxo groups, and the combined CO and COOH content. The dependence of these quantities on carbonyl content is either weak or even follows a reverse trend. It is proposed that the adhesion proceeds primarily through hydrogen bonds involving carboxyl group and/or coordinative bond formation between aluminium and epoxy and/or hydroperoxo groups.     

The Mechanisms of Peeling of Uncross-Linked Pressure Sensitive Adhesives

We analyze the peeling properties of an uncross-linked pressure sensitive adhesive. 90° peeling master curves on Pyrex^TM and PMMA (polymethylmetacrylate) are constructed The shift coefficients a_T are compared with the ones obtained from rheometrical shear tests.

With our machine, the peeling front is kept fixed, enabling us to observe the mechanisms of deformation of the adhesive. We count four different mechanisms of peeling in cohesive failure, and three in interfacial peeling (the last being unstable); they correspond to various slopes that we identify. The flow patterns at slow reduced velocities are two-dimensional. Then they undergo transitions to three-dimensional periodic complex flows, due to instabilities in the flow of thin adhesives. Interpretation of these peeling master curves are discussed in terms of rheology and physico-chemistry. It appears necessary to take into account the elongational properties of the adhesive, as well as the surface energy properties, to predict adhesion.     

二缩水甘油二甘醇胺封端的聚氨酯型深冷胶黏剂的合成、表征及其性能研究

采用一种新方法来提高环氧封端聚氨酯固化速率和室温以上拉伸剪切强度.先以二甘醇胺和环氧氯丙烷为原料,氢氧化钠溶液作为催化剂合成了二缩水甘油二甘醇胺(DGDGA),并用FT-IR,MS对其结构进行了表征.再以自制的DGDGA对异氰酸酯封端的聚氨酯预聚体进行封端,合成了具有高反应活性的缩水甘油胺型聚氨酯(GAPU),用FT-...     

Influence of the Chemical Structure of Urethane-Based Thickeners on the Properties of Waterborne Polyurethane Adhesives

To analyse the parameters that influence the thickening mechanism of waterborne polyurethane adhesives, different hydrophobically modified ethoxylated polyurethane based thickeners (HEUR) were used. The thickeners were characterized by proton nuclear magnetic resonance (¹H-NMR) and gel permeation chromatography (GPC). The thickened adhesive solutions were characterized by flow rheology, pH, particle size measurements, solids content, and confocal microscopy. The thickened solid adhesive films were characterized by ATR-IR spectroscopy, parallel plate rheology, dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC). The adhesion was measured by a T-peel test of leather/polyurethane adhesive/SBR rubber joints. The addition of the different HEUR thickeners increased the viscosity of the polyurethane dispersion to different degrees. Furthermore, whereas the un-thickened polyurethane dispersion showed a Newtonian rheological behaviour, a shear-thinning rheological behaviour was observed in the thickened dispersions due to thickener-thickener and polyurethane-thickener interactions. The viscosity of the thickened polyurethane adhesive solutions increased with the degree of hydrophobicity and the molecular weight of the thickener. The addition of different thickeners increased the pH values due to the ionic adsorption, which is one of the interactions that contribute to the thickening mechanism of the polyurethane thickeners, besides hydrogen bonding and van der Waals hydrophobic interactions (micelles). The entanglement of the thickened polyurethane adhesives was studied by confocal microscopy. Although the addition of the thickeners did not affect the thermal properties of the polyurethanes, the T-peel strength of leather/adhesive/SBR rubber joints was influenced by the rheological properties of the thickened adhesives.     

UV treatment of synthetic styrene-butadiene-styrene rubber

The effectiveness of the treatment with ultraviolet light (UV) on several polymeric surfaces has previously been established. In this study, a low pressure mercury vapour lamp was used as a source of UV radiation for the surface treatment of a difficult-to-bond block styrenebutadiene-styrene rubber (S6), the treatment time ranging from 10 s to 30 min. The UV-treated S6 rubber surfaces were characterized by contact angle measurements (ethylene glycol, 25°C), ATR-IR spectroscopy, XPS, Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). T-peel tests on UV-treated S6 rubber/polyurethane (PU) adhesive/ leather joints (before and after ageing) were carried out to quantify adhesion strengths. The UV treatment of S6 rubber produced improved wettability, the formation of C—O, C=O and COO^- moieties, and ablation (removal of a thin rubber layer from the surface). The extent of these modifications increased with increasing treatment time. The extended UV treatment produced greater surface modifications, as well as the incorporation of nitrogen moieties at the surface. Furthermore, noticeable ablation of S6 rubber surface occurred. Peel strength values increased with increased treatment time of UV treatment of S6 rubber. Also, with increasing treatment time, the adhesive joints showed different loci of failure: adhesional failure for the as-received and 2 min-UV treated S6 rubber/polyurethane adhesive/leather joints changed to mixed failure (cohesive in the treated S6 rubber + adhesional failure) for the 30 min-UV treated S6 rubber/polyurethane adhesive/leather joint.     

聚醚-聚酯型水性聚氨酯胶粘剂的合成

文章以聚醚二元醇、聚酯二元醇为软段,以甲苯二异氰酸酯、1,4-丁二醇等为硬段,采用两步法合成水性聚氨酯胶粘剂。研究了亲水基团的含量、异氰酸酯基(-NCO)与羟基(-OH)的摩尔比、聚醚/聚酯二元醇复配比例等对水性聚氨酯胶粘剂性能的影响。结果表明:亲水性基团含量1.5%～1.7%,异氰酸酯基与羟基的摩尔比为1.13～1.27,聚醚/聚酯复配比例为25/75～35/65时所合成的胶粘剂对BOPP/PET软包装复合材料有较佳的粘结性能。