聚氨酯密封胶国外研究进展

介绍了国外在提高聚氨酯密封胶固化性、粘接性、弹性及耐候性等性能方面的研究成果 ,内容涉及单组分湿固化密封胶 (含硅烷改性单组分胶 )及普通双组分密封胶、含多硫化物的双组分聚氨酯密封胶     

Compression set property and stress–strain behavior during compression of polysulfide sealants

In this article, mechanical and compression set properties, swelling property, and stress–strain behavior during compression of polysulfide sealants based on different polysulfide resin were investigated. The results showed that molecular weight and cross‐linking agent of liquid polysulfide resin had significant influence on mechanical and compression set properties of the sealants. The sealants based on higher molecular weight polysulfide resin had higher mechanical properties. At the same time, lower cross‐linking agent in polysulfide resin produced lower cross‐link density and higher swelling property, which resulted in higher compression set value of the sealant. However, when different molecular weight polysulfide resins were used in the sealant simultaneously, the testing results indicated that the compression performance of the sealants was significantly enhanced, while mechanical properties of the sealants kept nearly unchanged. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polysulfide sealant compositions. II. Interactions between elemental sulfur and organosulfur compounds

Added sulfur in polysulfide aircraft sealants can become chemically bound to the polymer backbone. The chemical processes involved, and their effect on thermal performance of the resulting sealants, have been examined. Reactions of aliphatic thiols with sulfur and amine catalysts have been reinterpreted to include possible involvement of hydropolysulfide intermediates. When the procedure was applied to polysulfide liquid polymers, products with substantial levels of tri- and tetra-sulfide links were formed. ¹³C–NMR spectroscopy of model compounds enabled the assignment of chemical shifts associated with S₃ to S₅ links in the sulfur enriched polymers. Spectroscopic examination afforded no evidence for the presence of such species in commercial polysulfide liquid polymers. No obvious detrimental effects on elevated temperature performance of polysulfide sealants resulted from the incorporation of up to 1% sulfur into the polymer backbone. A higher degree of cure is achieved and this is associated with increased hardness and modulus, together with reduced extension as compared with untreated sealants. © 1994 John Wiley & Sons, Inc.     

环氧树脂硫化聚硫醚密封剂的性能研究

以液体聚硫醚橡胶作为密封剂的生胶、环氧树脂(EP)作为硫化剂,成功制备出一种综合性能良好的新型聚硫醚密封剂。结果表明:聚硫醚橡胶的热分解温度(296.4℃)高于聚硫橡胶(281.0℃),热循环后聚硫醚密封剂的拉伸强度变化率或断裂伸长率变化率(31%或42%)均低于聚硫密封剂(45%或64%),说明前者的耐高温性能优于后者;聚硫醚密封剂对多种基材表现出稳定的粘接性能,其常温剥离强度均超过7.5 kN/m(均为内聚破坏),并且其在60℃盐水/航空煤油双层液中浸泡7 d后仍为内聚破坏;聚硫醚密封剂受温湿度影响较小,其硫化速率较大,并且其硫化效果和加工性能良好。     

国内聚氨酯密封胶研究进展

介绍了国内在传统单组分湿固化密封胶、硅烷改性单组分密封胶、蓖麻油基及丁(腈)羟聚氨酯双组分密封胶提高性能方面的最新研究进展。     

Effect of filler on the compression set,compression stress–strain behavior,and mechanical properties of polysulfide sealants

In this work, investigations were made on the mechanical properties, stress–strain behavior during compression, swelling and compression set properties of polysulfide sealants at different carbon black and silicon dioxide loadings, and dynamic mechanical thermal analysis was also presented. The results reveal that carbon black filler indeed has significant effects on reinforcing mechanical properties of polysulfide sealants. Increasing carbon black loading improves the tensile strength of sealants promptly, but compression performance increases slowly. The simultaneous use of carbon black and silicon dioxide filler in polysulfide sealants hardly changes the tensile strength of sealants, whereas the ultimate elongation and compression performance of sealants are enhanced remarkably. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polymer hybrids from self‐emulsified PU anionomer and water‐reducible acrylate copolymer via a postcuring reaction

Water‐reducible acrylate copolymer is obtained from a free‐radical copolymerization of n‐butyl acrylate, acrylic acid, and methacrylic acid. Self‐emulsified aqueous‐based polyurethane (PU) anionomer is prepared by the conventional method. The latent curing agents (di‐ and triaziridinyl compounds, HDDA‐AZ and TMPTA‐AZ) are synthesized from the reaction of aziridine with hexandiol diacrylate and trimethylolpropane triacrylate, respectively. These two polymers and the latent curing agent are miscible in each other and become a single component and self‐curable polymer dispersion. The carboxyl ions of polymers not only stabilize the aqueous polymer dispersions but also serve the curing site toward latent curing agent in the drying process. These two polymers blend with a curing agent, which results in new polymer hybrid formation. These polymer hybrids have the improvements on performance properties and the cost/performance benefits. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3578–3587, 2003     

Curing of silylated polyurethane with BF3‐monoethylamine complex as moisture‐curable adhesives and their properties

Boron trifluoride monoethylamine complex (BF₃‐MEA) was evaluated as one of the curing catalyst, for the moisture‐curable adhesive based on the polyurethane end‐capped with trimethoxysilane (silylated polyurethane). BF₃‐MEA worked as the catalyst of condensation reaction of trimethoxysilyl groups in silylated polyurethane to give the corresponding networked polymer. The curing speed, the bond strength, and the heat resistance of the crosslinked adhesives with BF₃‐MEA were compared with dibutyltin dimethoxide. It was found that BF₃‐MEA was a good curing catalyst, which showed the same performance in the bond strength and remarkable advantages in the curing speed and the heat resistance, compared with organotin compound. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

高分子微球的合成及其在密封剂中的应用

以亲水性4-乙烯基吡啶(4-Vp)为微球的壳层单体、苯乙烯(St)为微球的核层单体,采用一步无皂乳液聚合法制备了PS-P4V P[聚苯乙烯-聚(4-乙烯基吡啶)]微球;然后在该高分子微球表面覆盖了一层有机硅,合成了有机-无机杂化PS-P4VP-Si[有机硅包覆的聚苯乙烯-聚(4-乙烯基吡比啶)]微球;最后分别将两种微球与聚硫橡胶共混,制备相应的聚硫密封剂。研究结果表明:PS-P4VP、PS-P4VP-Si微球大小均一,两者粒径分别为290 nm和350 nm;两种微球分别作为聚硫密封剂的填料,既能提升密封剂的性能,又能降低密封剂本身的密度(比常规密封剂降低了15%～20%);同时,这两种微球填充的聚硫密封剂具有艮好的耐热性能和耐介质性能,特别是PS-P4VP-Si微球的综合性能更优异。     

The effect of epoxy resin to reduce the compression set of polysulfide sealant

In this article, modified polysulfide sealants with lower compression set were prepared by a simple method of introducing the diglycidyl ether of bisphenol A resin (DGEBA epoxy resin) into sealants. The investigation on reactivity analysis and gel faction test verified that the incorporation of epoxy resin in sealants was just a blending process rather than copolyaddition with polysulfide resin. Stress–strain behavior during compression revealed that the epoxy resin could reduce the compression stress when the sealants were loaded to a certain strain, which effectively lessened crosslink breakages and benefited to compression resistance. Also the rigid phenyl structure in epoxy resin may retard incidental slide between polysulfide chains and prevent interchange reactions between disulfide linkages. The incorporation of 2 phr epoxy resin distinctly reduced compression set of polysulfide sealant from 28.3% to 11.2% after compressed 25% at 23°C for 1 day. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Single component self‐curable aqueous‐based PU system with new aziridinyl curing agent

The self‐emulsified aqueous‐based polyurethane (PU) consists of carboxyl group, which is an ionic center not only stabilizing the aqueous polymer dispersion but also serving as the curing site toward aziridinyl curing agent. Two new aziridinyl curing agents, HDI‐AZ and ADA‐AZ, are prepared from an addition reaction of aziridine to hexamethylene diisocyanate (HDI) and adipic acyl chloride (ADA), respectively. These curing agents are added separately into NCO‐terminated PU prepolymer before or after the water dispersion process. The resulting PU dispersion becomes a single component self‐curable aqueous‐based PU system. The cured PU is obtained from this single component PU dispersion on drying at ambient temperature. The improved PU properties demonstrate the feasibility of this convenient single component self‐curable aqueous‐based PU system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:1997–2007, 2004     

Optimized formulation of an oxidative curing system for liquid polysulfide sealants used in fuel tanks by D‐optimal design method

In this work, the effective parameters in liquid polysulfide curing system were optimized by D ‐optimal design method. Five main components in the formulation, carbon black, vulcanizing agents (MnO₂, Na₂Cr₂O₇, and PbO₂), CaCO₃, fumed silica, and chlorinated paraffin, were selected. Mechanical and chemical properties of the samples were investigated. The results showed that tensile strength, hardness, viscosity, and optimum cure time (t₉₀) presented a suitable coordination with reduced quadratic model. For elongation at break and swelling tests, reduced two‐factor interaction (2FI), and for peel strength, a linear model showed the best correlation. To achieve the desirable properties for liquid polysulfide sealants used in fuel tanks, an optimized amount of the above components in the formulation were used. Finally, MnO₂ curing system, compared with Na₂Cr₂O₇ and PbO₂, was selected as the best choice. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of telechelic dithiol oligomers containing sulfur atoms-moisture barrier properties

The aim of this work was to synthesize new polysulfide materials from butadiene, styrene, isoprene, and methacrylate monomers and to study their moisture vapor permeability. For this purpose, a series of telechelic dithiol polysulfide oligomers were prepared by a polycondensation reaction between dianionic species of the corresponding monomer and sulfur or by reduction of the resulting cyclic polysulfide polymers. This last process was followed by ¹H-NMR and elemental analysis. It was established that the scission of the polysulfide linkages to thiol end groups was fastest with the greatest number of sequential sulfur atoms. The thiol reactivity was used to prepare cured materials from the liquid oligomers and manganese dioxide: Networks were obtained from butadiene dithiol oligomers, whereas chain extension occurred for the others. Infrared analysis suggests that the reticulation reaction results from thiol addition to the double bond. The moisture vapor transmission test applied to these different materials showed that these new compounds present good moisture barrier properties.     

Isocyanate‐Free Curing of Glycidyl Azide Polymer with Bis–propargylhydroquinone

Bis‐propargylhydroquinone (BPHQ) is an alkyne functionalized isocyanate‐free curing agent for hydroxyl terminated azido polymers. Conventionally, glycidyl azide polymer (GAP) is cured by isocyanate based curatives, which are toxic and hygroscopic in nature. The reaction between hydroxyl end group of GAP and isocyanate is highly sensitive to moisture causing voids in the propellant, leading to poor mechanical properties. Herein, an alternate approach was adapted to exploit 1,3‐dipolar cycloaddition reaction between azido group of GAP and the triple bond (–C≡CH) of BPHQ without catalyst at 50 °C forming triazole crosslinked polymer. The curing behavior of GAP‐BPHQ system was studied by rheological method and based on the results the gel time was determined. In addition, the reaction between GAP and BPHQ was carried out with various GAP/BPHQ ratios (0.9 to 2.5) and effects on mechanical properties of resulting triazole polymers were investigated. Post curing hardness of GAP‐BPHQ binder system was tested by surface Shore‐A hardness measurement. The compatibility of BPHQ with energetic oxidizers such as ammonium dinitramide (ADN) and hydrazinium nitroformate (HNF) were also studied by differential scanning calorimetery (DSC) technique and showed good compatibility. The activation energy (E _a) of cured GAP‐BPHQ binder was evaluated by DSC using Ozawa and Kissinger methods and are found to be 33.55 and 33.16 kcal mol^–1, respectively. The advantage of this curing system between GAP and BPHQ is unaffected by moisture as compared to isocyanate based urethane systems and also no need to control humidity during the processing of propellant. The experimental results reveal that triazole crosslinked polymer system could be a better choice to develop novel energetic binder systems for explosives as well as propellants composition with improved performance and eco‐friendly nature.     

聚硫中空玻璃密封胶的性能及生产工艺

概述了中空玻璃密封胶的性能要求，及现有各种中空玻璃密封胶的特性。介绍了聚硫中空玻璃密封胶的配方组成和生产工艺，并就其性能特点与其他密封胶进行了比较。概述了中空玻璃密封胶的发展趋势。     

改性聚硫橡胶的研究及制备

用过量的甲苯二异氰酸酯(TDI)与不同分子量的聚醚(PPG)反应,首先形成有活性端基(-NCO)的聚氨酯预聚体。加入液态聚硫橡胶(LP3),经过催化剂的催化反应生成改性聚硫橡胶,用丁苄酯,通过分子设计,合成出了具有良好性能又能应用于中空玻璃的新型改性聚硫橡胶。用红外光谱鉴定了其物质结构,并作固化试验测定其固化后的硬度,及其黏度等一系列性能,最终确定甲苯二异氰酸酯与聚醚的比率为2∶1(摩尔比);预聚体、液态聚硫橡胶和溶剂的比为1∶1∶1(质量比)。通过于原来的中空玻璃密封胶比较,其具有很好的性能且成本很低。     

Self-healable MnO2-cured polysulfide sealant and the effect of fillers on its self-healing ability

MnO₂-cured polysulfide sealants have been widely used in various industrial fields and the effects of MnO₂ and three fillers on their mechanical behavior, thermal property and self-healing ability were focused on in this paper. Under a moderate thermal stimulus, the tensile strength can be significantly restored due to the dynamic exchange of disulfide bonds in polysulfide segments. The residue of a small dosage of thiol promotes the healing process of polysulfide sealants. After healing at 75°C for 48 h, the tensile strength of 2 wt% MnO₂ cured sealant is restored to more than 90%. Then, this sealant is modified with three fillers to enhance the tensile strength, however, the addition of fillers hinder the healing process to some extent. Significantly, the sealant modified with 2.5 wt% TiO₂ can perform a certain enhancement without sacrificing the healing mechanical properties. These outcomes are helpful for the development of MnO₂-cured polysulfide sealants toward sustainable industrial applications.     

Development of halogen‐free flame‐retardant thermoplastic elastomer polymer blend

Ethylene‐propylene diene rubber (EPDM) and isotactic polypropylene (iPP) blends have widest industrial applications that require a degree of flame retardancy. Halogen‐free intumescent technology based on phosphorous salt is a significantly advanced approach to make the polymer flame‐retardant. Both ammonium polyphosphate and ethylenediamine phosphate are important intumescent compounds. Their combination with carbonific and spumific agents were studied in binary blends of EPDM/PP. The polymer system was vulcanized online during melt mixing. Intumescent flame‐retardant polymer systems exhibit good flame‐retardancy with optimum comparable physiomechanical, electrical, and fluid resistance properties, including lower smoke emission, which is essential to protect people because the visibility remains unaffected in the event of fire. Pronounced charring and intumescent effect appear to enhance the flame‐retardancy of the polymers. Possible expected intumescent mechanism is proposed based on the nonpyrolysis mechanism for the flame‐retarded polymer and the intumescent components. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 407–415, 2004     

A novel bio‐based phthalonitrile resin derived from catechin: synthesis and comparison of curing behavior with petroleum‐based counterpart

The development of bio‐based thermosetting resins with good thermal stability can potentially afford sustainable polymers as replacements for petroleum‐based polymers. We report a practical route to a novel catechin‐based phthalonitrile resin precursor (CA‐Ph), which contains free phenolic hydroxyl groups that result in ‘self‐curing’ at elevated temperatures to afford a thermostable polymer. Comparison of the performance of this CA‐Ph resin with that of a conventional petroleum‐based bisphenol A phthalonitrile resin (BPA‐Ph; containing 5 wt% of the curing agent 4,4′‐diaminodiphenylsulfone) revealed that CA‐Ph exhibits a lower melting point and curing temperature. Cured CA‐Ph resin retains 95% of its weight at 520 °C under a nitrogen atmosphere, which compares favorably with results obtained for BPA‐Ph resin that retains 95% of its weight at a lower temperature of 484 °C. Kinetic results indicated that the curing reactions of both CA‐Ph and BPA‐Ph systems follow an autocatalytic mechanism. These results suggest that catechin is a useful bio‐based feedstock for the preparation of self‐curing and thermally stable phthalonitrile resins for advanced technological applications. © 2017 Society of Chemical Industry     

汽车风挡玻璃用密封胶的结构与性能研究

研究了三种汽车风挡玻璃用单组分PU(聚氨酯)密封胶和SPU(硅烷改性聚氨酯)密封胶。采用红外光谱(FT-IR)、凝胶渗透色谱(GPC)法分析了三种密封胶的结构和相对分子质量,并对其固化行为、粘接性能和力学性能等进行了研究。结果表明:相对湿度越大(或固化温度越高),则三种密封胶的表干时间越短且固化速率越大;在三种密封胶的储存过程中,其表干时间和固化速率变化不大,稳定性较好;SPU密封胶与基材的粘接性能优于PU密封胶;PU密封胶的拉伸强度(≥8.2 MPa)和撕裂强度(19 N/mm)均优于SPU密封胶的拉伸强度(5.8 MPa)和撕裂强度(13 N/mm)。