Fumaric Acid as a Promoter of Adhesion in Vulcanized Synthetic Rubbers

The addition of dicarboxylic acids to polyurethane adhesives, to improve their adhesion to vulcanized synthetic rubbers, may cause the degradation over time of the adhesives. To avoid the degradation of polyurethane adhesives, this study proposes a surface treatment on vulcanized synthetic rubbers with carboxylic acid solutions instead of adding them to the adhesives. In all the styrene-butadiene rubbers studied, a great improvement in adhesion to polyurethane adhesives has been obtained. The nature of the solvent used to disperse the fumaric acid over the surface, as well as the nature of the rubber, determined the effectiveness of the surface treatment. The use of fumaric acid solutions provided optimum results when the surface of the rubber was slightly roughened. The increase in the adhesion properties of styrene-butadiene rubbers, treated with fumaric acid, has been attributed to an increase in the degree of the surface roughness and to an enhancement in the surface energy (due to the elimination of abhesive substances on the surface of the rubber and to the formation of C-O groups by surface oxidation). The effectiveness of the surface treatment on rubbers with fumaric acid in the adhesion of styrene-butadiene rubbers has been compared with those produced by other common treatments, such as halogenation and roughening. In general, T-peel strengths obtained in the rubbers treated with fumaric acid were similar to those obtained through halogenation and were always higher than those obtained through roughening. Therefore, surface treatment of styrene-butadiene rubbers with fumaric acid can be considered as an alternative method to chemical treatments currently used, especially in the footwear industry.     

Weak Boundary Layers in Styrene-Butadiene Rubber

In this paper two kinds of weak boundary layers (WBL) in synthetic vulcanized styrene-butadiene rubber are described.

i) WBL produced by the presence of antiadhesion compounds of the rubber formulation (zinc stearate, microcrystalline paraffin wax). These WBL cannot be effectively removed by solvent wiping, whether followed by washing with an ethanol/water mix or not. Although this treatment allowed a significant removal of zinc stearate, the paraffin wax concentration on the surface was not greatly reduced, thus, poor adhesion of rubber was obtained. Chlorination with small amounts of ethyl acetate (EA) solutions of trichloro isocyanuric acid (0.5-5 wt% TCI/EA) and/or an extended halogenation treatment increased the adhesion strength and effectively eliminated the zinc stearate from the rubber surface. If an additional heat treatment (50°C/24h) of the chlorinated rubber was also carried out, the WBL was more effectively eliminated and the resulting adhesion was independent of the amount of chlorination agent applied to the rubber surface. Furthermore, this heat treatment favoured the elimination of WBL in the untreated rubber and also contributed to the removal of WBL produced by an excess of halogenation agent.

ii) WBL created by an excess of chlorination agent applied to the rubber surface. The excess of chlorination agent produced lack of adhesion in the rubber because there was significant damage of the rubber surface and a non-rubber surface layer was formed (mainly due to oxidized, chlorinating agent residues and cyanuric acid), which contributed to the formation of WBL. To avoid the creation of WBL, a postchlorination treatment of rubber with a solution of 25 wt% ethanol in water followed by a vacuum-drying process produced excellent results. The effectiveness of this treatment relied on combining an adequate degree of chlorination with no external surface deterioration of the rubber by the excess of chlorination agent.     

Weak Boundary Layers in Styrene-Butadiene Rubber

In this paper two kinds of weak boundary layers (WBL) in synthetic vulcanized styrene-butadiene rubber are described.

i) WBL produced by the presence of antiadhesion compounds of the rubber formulation (zinc stearate, microcrystalline paraffin wax). These WBL cannot be effectively removed by solvent wiping, whether followed by washing with an ethanol/water mix or not. Although this treatment allowed a significant removal of zinc stearate, the paraffin wax concentration on the surface was not greatly reduced, thus, poor adhesion of rubber was obtained. Chlorination with small amounts of ethyl acetate (EA) solutions of trichloro isocyanuric acid (0.5–5 wt% TCI/EA) and/or an extended halogenation treatment increased the adhesion strength and effectively eliminated the zinc stearate from the rubber surface. If an additional heat treatment (50°C/24h) of the chlorinated rubber was also carried out, the WBL was more effectively eliminated and the resulting adhesion was independent of the amount of chlorination agent applied to the rubber surface. Furthermore, this heat treatment favoured the elimination of WBL in the untreated rubber and also contributed to the removal of WBL produced by an excess of halogenation agent.

ii) WBL created by an excess of chlorination agent applied to the rubber surface. The excess of chlorination agent produced lack of adhesion in the rubber because there was significant damage of the rubber surface and a non-rubber surface layer was formed (mainly due to oxidized, chlorinating agent residues and cyanuric acid), which contributed to the formation of WBL. To avoid the creation of WBL, a postchlorination treatment of rubber with a solution of 25 wt% ethanol in water followed by a vacuum-drying process produced excellent results. The effectiveness of this treatment relied on combining an adequate degree of chlorination with no external surface deterioration of the rubber by the excess of chlorination agent.     

Surface modification of synthetic vulcanized rubber

Surface modifications produced by treatments (mainly halogenation) of synthetic vulcanized styrene-butadiene rubber (SBR) leading to increased adhesion properties with polyurethane adhesives have been studied. T-peel tests, scanning electron microscopy (SEM), advancing contact angle measurements, infra-red (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and differential scanning calorimetry (DSC) were used to analyze the nature of surface modifications produced in the rubber. Although some surface heterogeneities were created, physical treatments (ultrasonic cleaning, solvent wiping, abrasion) did not noticeably increase the adhesion strength because certain abhesive substances (e.g. zinc stearate, paraffin wax) cannot be removed from the rubber surface by such treatments. Chemical treatment (chlorination) was carried out using ethyl acetate solutions of trichloroisocyanuric acid (TCI) (1,3,5-trichloro-1,3,5-triazine-2,4,6-trione). Chlorination of SBR with trichloroisocyanuric acid produced a significant improvement in T-peel strength, due to the contribution of mechanical (surface roughness, microcracks), thermodynamical (increase of polar contribution to the surface energy) and chemical (removal of abhesive substances, creation of polar groups) rubber surface modifications. The strong adhesion between the chlorinated SBR surface and the polyurethane adhesive was due to the presence of oxidized species of >C=O, -C-OH and -COR type. Chlorination of SBR is a fast reaction which needs only a small concentration of chlorination agent (< 1 wt% TCI/ethyl acetate) to produce high adhesion levels. An increased amount of TCI facilitated the chlorination reaction progressing from the exterior to the internal rubber bulk; however, although a thicker layer of chlorinated rubber created no further increase in adhesion strength was obtained.     

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.     

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.     

疏水性二氧化硅气凝胶的常压制备与表征

采用溶胶-凝胶技术,以正硅酸乙酯为有机前驱体,三甲基氯硅烷为改性剂,在常压下干燥制备出疏水性二氧化硅(SiO2)气凝胶,同时采用密度测量、比表面积和孔径分布仪、扫描电镜、热重分析仪对SiO2气凝胶进行表征。文章重点研究反应物配比和表面修饰对SiO2气凝胶性能的影响。结果表明,采用正硅酸乙酯、水、乙醇体积配比为25︰6︰80和三甲基氯硅烷的正己烷溶液表面修饰合成的SiO2气凝胶性能质量较好。     

Influence of the nature and formulation of sty rene-butadiene rubber on the effects produced by surface treatment with trichloroisocyanuric acid

The nature and formulation of two synthetic sulfur-vulcanized styrene-butadiene rubbers affected the extent, but not the nature, of the surface modification produced by halogenation with different amounts (1-7 wt%) of trichloroisocyanuric acid (TCI) solutions in ethyl acetate. R1 rubber had a low oil and plasticizer content, whereas R2 rubber contained a smaller amount of styrene than R1, and a relatively significant amount of oil and plasticizer. Chlorination of the rubbers decreased their tensile strength (more markedly in R2) without noticeable changes in elongation at break, and heterogeneities and cracks were created on the rubber surface (mainly in R2). The surface modifications were not influenced by the manner in which the post-chlorination agent was removed (air or vacuum). Chlorination with TCI created C-Cl, C-O, and COO- moieties on the rubber surface which were responsible for its enhanced acid-base contribution to the surface energy. The extent of chlorination was more extensive in R1 (the rubber with a smaller butadiene content). The surface modification was less effective for R2, due to its noticeable amount of oil and plasticizer. On the other hand, when the chlorination was carried out with 7 wt% TCI, removal of the excess of the post-chlorination agent in vacuum prevented the formation of weak boundary layers (due to isocyanuric acid + mechanically damaged surface) in the treated surfaces. The nature and formulation of the rubber determined the thickness of the weak boundary layer (thinner in R1). On the other hand, a relatively deep penetration (at least 10 nm) of the chlorination agent into the rubber bulk was produced.     

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.     

无卤阻燃硅溶胶改性水性聚氨酯的研究

以聚醚(N -210)、异佛尔酮二异氰酸酯(IPDI)为基本单体,一缩二乙二醇(EX)为扩链剂,二羟甲基丙酸( DMPA)为亲水扩链剂,制备出固含量为30％的水性聚氨酯(WPU)乳液.采用机械分散的方式将纳米硅溶胶按计量加入到WPU乳液中,得到一系列硅溶胶改性的WPU乳液.研究表明,硅溶胶在WPU中分散得比较均匀,硅溶...     

聚乙二醇对碳酸化法白炭黑的表面改性研究

以石灰窑气和水玻璃碳酸化法制备白炭黑为研究体系,用表面活性剂聚乙二醇(PEG)原位有机湿法改性,以提高白炭黑同聚合物胶料的亲和性。在85℃,原料配比(水玻璃与水体积比)1∶5,二氧化碳浓度40%,通气速率60 mL/min和搅拌速率180 r/min的实验条件下反应2 h,考察了不同相对分子量的PEG对改性后白炭黑产率和性能的影响,改性效果顺序是聚乙二醇PEG(6 000)>PEG(10 000)>PEG(20 000)。还考察了PEG相对添加量对改性后的白炭黑的产率以及性能的影响,PEG(6 000)相对添加量30%较为适宜。     

Sorption of Acid Dyes onto Silica Modified with Cetyltrimethylammonium Cations

The sorption behavior of acid dyes onto cetyltrimethylammonium bromide (CTAB)- modified silica as a function of pH in the aqueous medium was studied. Single- and multi-solute sorption equilibria of orange Ⅱ(OR), phenol red (PR) and Eriochrome Black T (EBT) were studied at pH 3, unbuffered water pH and pH 11. Sorption behavior of EBT could not be conducted at pH 3 due to its aggregation in acidic medium. All the reaction conditions, experimental protocols and techniques remained the same throughout the sorption process. Sorption isotherms for single-solute system were fitted by the Langmuir model, while Langmuir competitive model (LCM) and the ideal adsorbed solution theory (IAST) coupled with Langmuir model (IAST/Langmuir) were used for the prediction of multisolute competitive sorption. Sorption affinities influenced by the factors like physical interactive forces between the molecules of CTA on silica and sorbate, structural limitations of the dyes based on their geometrical arrangement were investiga     

磺化硅胶催化水杨酸O-酰化反应的研究

研究了以磺化硅胶为固体酸催化剂,催化水杨酸与乙酸酐合成乙酰水杨酸的O-酰化反应条件。实验结果表明,磺化硅胶对O-酰化反应表现出良好的催化活性,水杨酸与乙酸酐摩尔比1∶2,磺化硅胶0.4g,水浴温度70°C,反应时间35min,乙酰水杨酸平均收率可达81.8%。     

磺化硅胶催化合成乙酸正丙酯的研究

磺化硅胶是一种以化学键键合而成,性能稳定的固体酸催化剂。实验以磺化硅胶为催化剂,乙酸和正丙醇为原料合成了乙酸正丙酯。以单因素法分别考察了酸醇摩尔比、反应时间、催化剂用量以及催化剂的重复使用次数对酯化率的影响。最佳合成条件为：n（乙酸）∶n（正丙醇）=1∶1,回流时间为60 min,催化剂用量为反应物总质量的1.2%,反应的酯化率可达93.4%,催化剂重复使用10次后的酯化率仍达81.1%。研究结果表明：磺化硅胶对乙酸正丙酯的合成具有良好的催化活性。     

磺化硅胶催化合成乙酸正辛酯的研究

磺化硅胶是一种以化学键键合而成,性能稳定的固体酸催化剂。文章以冰醋酸和正辛醇为原料,磺化硅胶为催化剂,合成了乙酸正辛酯,并获得了最佳合成条件:n(乙酸)∶n(正辛醇)=1∶1.2,回流时间为50 min,催化剂用量为反应物总质量的0.8%,乙酸正辛酯的酯化率可达97.5%,催化剂重复使用5次后的酯化率仍达91.1%。磺化硅胶对乙酸正辛酯的合成具有良好的催化活性。     

磺化硅胶催化合成乙酸正丁酯的研究

磺化硅胶是一种以化学键键合而成,性能稳定的固体酸催化剂。本文以冰醋酸和正丁醇为原料,磺化硅胶为催化剂,合成了乙酸正丁酯,并获得了最佳合成条件:催化剂用量为反应物总质量的1.0%,n(乙酸)∶n(正丁醇)=1∶1.5,回流时间为45 min,乙酸正丁酯的酯化率可达98.5%,催化剂重复使用10次后的酯化率仍达81.3%。磺化硅胶对乙酸正丁酯的合成具有良好的催化活性。     

不同养护条件下含石英玻璃地质聚合物砂浆的变形行为

为阐明典型活性组分（无定型SiO2）在地质聚合物中的作用行为和效应,探索地质聚合物体系中碱-集料反应评价方法,研究常温（23℃）和38℃湿气养护（相对湿度〉95%）、80℃在1 mol/L NaOH溶液浸泡及150℃在10%（质量分数）的KOH溶液压蒸下,含石英玻璃集料地质聚合物砂浆的变形行为,采用扫描电镜、电子散射能谱研究产物的组成和微观结构。结果表明：4种养护条件下,特别是在传统普通硅酸盐水泥（OPC）体系所规定的养护条件和龄期内,含石英玻璃集料地质聚合物砂浆没有发生有害膨胀;但是随养护条件不同,地质聚合物基体和石英玻璃可能经历不同的化学反应过程,进而导致不同的变形行为,特别是在高温且有外碱介入时,地质聚合物基体在后期会产生膨胀效应。不宜采用单一的适于OPC体系的高温、高碱快速检测混凝土碱-集料反应的检测方法来评价地质聚合物体系中的碱-集料反应行为。     

Adsorption/Desorption of Hg(II) on FDU-1 Silica and FDU-1 Silica Modified with Humic Acid

Incorporation of humic acid in the FDU-1 mesoporous silica improved Hg(II) adsorption and did not destroy the ordered network, providing surface area of 500 m² g^?1, pore volume of 0.9 cm³ g^?1, and mean pore diameter of 10 nm. Carboxylic and phenolic groups increased the affinity by forming surface complexes with Hg(II). Isotherms (25.0 ± 0.1°C) were fitted to the Freundlich equation, exhibiting K_f values that increased with pH and 1/n that decreased to values < 1 with the heterogeneity of sites. Hg(II) desorption in 0.10 mol L^?1 acetic acid was lower than 10%, suggesting that chemisorption processes govern the Hg(II) removal.     

硅胶负载磷钨酸催化合成丁酸戊酯的研究

以硅胶负载磷钨酸为催化剂研究丁酸戊酯的合成反应,确定了最佳反应条件：催化剂用量2.0/0.2 mol丁酸,醇酸摩尔比为2：1,反应时间为2 h.研究结果表明该催化剂催化效果好,反应条件温和,方法简便,酯化率可达96%,而且催化剂可重复使用.     

用1，10－二氮杂菲分光光度法测定沉淀法白炭黑中的铁含量

提出并研究了使用１，１０－二氮杂菲分光光度法测定沉淀法白炭黑中铁含量的分析方法。其具体步骤为：首先用氢氟酸处理试样，使沉淀法白炭黑（二氧化硅）转化成四氟化硅气体逸出。而后在ｐＨ为４～５条件下，用盐酸羟胺处理剂将残留液中的三价铁离子还原成二价铁离子，加入１，１０－二氮杂菲显色剂（与二价铁离子反应可生成橙红色络合物），再用分光光度法测定其中的铁含量。实验表明，本方法原理可靠，分析步骤简便，抗铜、锰离子干扰性强，精密度与准确度较高。