Influence of the solids content on the properties of waterborne polyurethane dispersions obtained with polycarbonate of hexanediol

Waterborne polyurethane adhesives are an interesting alternative to the current solvent-borne polyurethane adhesives used in the industry. Different aliphatic waterborne polyurethane dispersions (PUDs) with different solids content were synthesised by reacting isophorone diisocyanate (IPDI) with a polycarbonate derived from hexanediol via the acetone method. The PUDs were characterised by Brookfield viscosity, pH, particle size, transmission electron microscopy (TEM) and solids content measurement. The dry polyurethane films were characterised by ATR-IR spectroscopy, plate–plate rheology, differential scanning calorimetry (DSC) and thermal gravimetry (TGA). Their adhesion was evaluated from T-peel tests of flexible PVC/waterborne polyurethane dispersion/flexible PVC joints and single lap-shear tests of aluminium/waterborne polyurethane dispersion/aluminium joints.The PUDs showed bimodal particle size distribution. The mean particle size of the PUDs decreased by increasing their solids content but the particle size distribution of the PUDs increased by decreasing their solids content. As the solids content increased the Brookfield viscosity of the PUDs increased due to lower mean particle size where particle crowding was favoured, the PUD having 44 wt% solids content was an exception (higher particle size but lower polydispersity). On the other hand, the increase in the solids content increased the hard segments content and the degree of phase separation of the polyurethanes. The greater the solids content of the polyurethanes, the lower their glass transition temperatures values and the lower the elastic moduli. Adhesive strength under peel stresses were not affected by the solids content in the polyurethanes but the single lap-shear strength values decreased by increasing the solid contents in the polyurethanes due to lower hard segments content.     

Influence of the hard-to-soft segment ratio on the adhesion of water-borne polyurethane adhesive

Three water-borne polyurethane dispersions were synthesised by the pre-polymer mixing process. Different hard segment contents in the polyurethanes were obtained by varying the diisocyanate/macroglycol (NCO/OH) molar ratio. A decrease in the NCO/OH ratio produced an increase in the mean particle size and in the pre-polymer viscosity, as well as a decrease in the molecular weight of the polyurethane. On the other hand, the lower the NCO/OH ratio, the more crystalline the polyurethane and the lower the resistance to flow at high temperature. Lower NCO/OH ratios improved the thermal degradation stability of the polyurethane. Finally, a high initial adhesion to PVC was obtained in all joints produced with the aqueous polyurethane dispersions and the final adhesion increased as the NCO/OH ratio in the water-borne polyurethane adhesive decreased.     

Incidence of the polyol nature in waterborne polyurethane dispersions on their performance as coatings on stainless steel

Three waterborne polyurethane dispersions derived from polyester, polyether and polycarbonate diols with molecular weight of 1000 Da were synthesized by the acetone method and used as coatings on stainless steel 304 plates. The properties of the dispersions and the polyurethane films were influenced by the polyol nature. The polyurethanes obtained with polyether or polyester showed higher degree of phase separation between the soft and the hard segment. The higher adhesive strength under shear stresses was obtained in the joints produced with the waterborne dispersion obtained with polycarbonate diol. The properties of the polyurethane coating obtained with polycarbonate diol on stainless steel 304 were significantly higher as compared with the others. Improved performance of coatings obtained with polycarbonate diol was ascribed to the higher polarity of the carbonate groups that contributed to additional hydrogen bond formation between soft segments with respect to those obtained with polyether or polyester     

阳离子型水性丙烯酸酯聚氨酯塑料涂料的研究

合成了阳离子型羟基丙烯酸酯树脂分散体(A组分),其与多异氰酸酯固化剂(B组分)配制的双组分水性聚氨酯涂料可用于ABS、PC/ABS、PC、PVC等塑料制件的表面涂装。研究了甲基丙烯酸-N,N-二甲氨基乙酯(DMAEMA)、丙烯酸羟乙酯(HEA)用量,硬单体甲基丙烯酸甲酯与软单体丙烯酸丁酯(MMA/BA)的质量比及A、B组分(NCO/OH)物质的量比对聚氨酯涂膜性能的影响,采用FT-IR和DSC对固化膜结构进行了表征。结果表明:DMAEMA用量为5%,HEA用量为15%,m(MMA)/m(BA)=2,n(NCO)/n(OH)=1.2~1.4可得到力学性能、耐水性、耐化学品性优秀的涂膜。     

Coatings prepared from waterborne polyurethane dispersions obtained with polycarbonates of 1,6-hexanediol of different molecular weights

Waterborne polyurethane dispersions (PUDs) were synthesized with polycarbonates of 1,6-hexanediol of different molecular weight (500–3000 Da) and their properties, adhesion (Hatch adhesion) and coatings on stainless steel properties (Pencil hardness, Persoz hardness, gloss at 60°, chemical resistance, yellowness index) were characterized. The hatch adhesion of the polyurethane coatings to stainless steel was very good and decreased slightly by increasing the molecular weight of the polycarbonate of 1,6-hexanediol. Both the Pencil and Persoz hardness values of the coatings increased by increasing the hard segments content in the polyurethane, i.e. by decreasing the molecular weight of the polycarbonate of 1,6-hexanediol, whereas the gloss and the yellowness index were lower for the coatings obtained with the polycarbonate of 1,6-hexanediol of molecular weight of 500 Da. Very good chemical resistance against ethanol for all polyurethane coatings on stainless steel plates was obtained but for long time of ethanol in contact with the coating surface the chemical resistance decreased, more markedly for the polyurethane coating obtained with the polycarbonate of 1,6-hexanediol of higher molecular weight. In summary, the segmented structure of the waterborne polyurethane dispersion determined the properties of the polyurethane coatings obtained from them.     

Synthesis and mechanical properties of bio-sourced polyurethane adhesives obtained from castor oil and MDI-modified cellulose acetate: Influence of cellulose acetate modification

In this study, cellulose acetate and castor oil have been used to synthesize new eco-friendly alternatives to traditional polyurethane adhesives. First, cellulose acetate (CA) was modified with diphenylmethane-4,4′-diisocyanate (MDI) at different NCO:OH molar ratios, ranging from 2 to 4.53, and then the resulting biopolymers were mixed with castor oil (CO) at 1:1 wt ratio. The fully cured bio-sourced adhesives were rheologically characterized by applying dynamic oscillatory torsional tests at different temperatures (from −30 up to 200 °C). Furthermore, their adhesion performance on stainless steel and poplar wood substrates was analyzed, by conducting standardized mechanical tests, namely single-lap shear and 180° peel strengths, at room temperature and 100 °C. Fourier transform infrared spectroscopy-attenuated total reflectance along with differential scanning calorimetry and thermogravimetric analysis were also performed. Above a critical NCO:OH ratio, a thermo-rheological simplicity was found within the whole temperature range considered, being able to apply the t-T superposition principle. However, an increase in the temperature led to a depletion in their mechanical performance, thus reducing their temperature range of application. Thermal and spectroscopic analysis corroborated the complete disappearance of free isocyanate during the first few days of curing, and a segmented structure, typical of polyurethanes. Optimum thermo-rheological behaviour and adhesion performance on wood and stainless steel of the bio-sourced polyurethanes studied were found for NCO:OH molar ratios higher than 3.5, which was related to the higher compatibility between hard and soft microdomains.     

双组分水性聚氨酯涂料的合成与表征

随着环境法规对涂料的挥发性有机化合物（VOC）含量的限制，高性能与低VOC含量相结合的双组分水性聚氨酯涂料成为涂料工业发展的趋势。采用三羟甲基丙烷（TMP）为扩链剂合成具有交联结构的水性聚氨酯分散体多元醇，与多异氰酸酯固化剂组成双组分水性聚氨酯涂料。研究发现双组分涂膜的机械性能和外观是由合成的水性聚氨酯多元醇的扩链剂（TMP）含量，中和度，中和工艺和双组分涂料的配比等决定的。当扩链剂含量为2％－4％，中和度为100％，NCO:OH=1．0－1．2时所得双组分水性聚氨酯涂膜外观好，快干，硬度高和施工方便。     

PVC手套涂层用水性聚氨酯的研制

以六次甲基二异氰酸酯(HDI)、异佛尔酮二异氰酸酯(IPDI)和聚醚PPG等为原料,通过丙酮法合成了PVC手套涂层用高强度、高伸长率水性聚氨酯乳液,探讨了n(NCO)/n(OH)、n(IPDI)/n(HDI)和后扩链剂乙二胺对水性聚氨酯性能的影响,并对水性聚氨酯乳液进行了冻融稳定性测试。结果表明,当n(NCO)/n(OH)=4.5、n(IPDI)/n(HDI)=1.5:1时,后扩链剂用量为0.7 g时,制备的水性聚氨酯具有良好的低温涂层稳定性,胶膜的拉伸强度24.61 MPa,伸长率达到663.5%,且手套在70℃、72 h内壁不粘连。     

Characterization of thermoplastic polyurethane adhesives with different hard/soft segment ratios containing rosin as an internal tackifier

Three thermoplastic polyurethanes (TPUs) containing different hard/soft (h/s) segment ratios (1.05-1.4) were prepared using the prepolymer method. MDI (diphenylmethane-4,4′diisocyanate) and polyadipate of 1,4-butanediol (M _w = 2440) were allowed to react to produce the prepolymer. To provide the polyurethanes with high immediate adhesion to different substrates, a rosin + 1,4-butanediol mixture (1 : 1 equivalent%) was used as chain extender (TPU-Rs). These TPU-Rs had two types of hard segments: (i) Urethane hard segments, produced by reaction of the isocyanate and the 1,4-butanediol, and (ii) Urethan-amide hard segments, produced by reaction of the isocyanate and the carboxylic acid functionality of the rosin. The TPUs and TPU-Rs were characterized using FTIR spectroscopy, gel permeation chromatography, differential scanning calorimetry, stress-controlled plate-plate rheology, stress-strain measurements, and Brookfield viscosity. The TPUs and TPU-Rs were used as raw materials to prepare solvent-based polyurethane adhesives, the adhesion properties of which were obtained from T-peel tests on PVC/polyurethane adhesive/PVC joints. The addition of rosin as an internal tackifier increased the average molecular weight, more markedly in the TPU-Rs containing higher hard/soft segment ratios, but the elastic and viscous moduli decreased. An increase in the hard/soft segment ratio of the TPU-Rs retarded the kinetics of crystallization (which was determined by the soft segment content in the polyurethane), and increased the immediate T-peel strength in PVC/polyurethane adhesive/PVC joints (which was determined by the urethan-amide hard segments). Furthermore, addition of rosin to the polyurethanes decreased the final adhesion, although always reasonably high peel strength values were obtained.     

水性双组分聚氨酯涂料的研制及性能研究

探讨了含羟基聚丙烯酸酯分散体、多异氰酸酯固化剂、n-NCO／n-OH配比、固化时间和干燥条件,以及催化剂用量对水性双组分聚氨酯涂膜性能的影响,同时对水性双组分聚氨酯涂料的活化期进行了研究。     

阴离子型水性聚氨酯和阳离子型水性聚氨酯的合成及分析

以甲苯二异氰酸酯（TDI）和聚酯二醇等为基本原料,在NCO／OH比例及反应物量相同的情况下,分别合成了阴离子型水性聚氨酯和阳离子型水性聚氨酯。对它们进行了红外光谱分析、热重分析、粒径分析、吸水率测定和力学测试。结果表明：合成的阴离子水性聚氨酯无残余的-NCO,粒径、吸水率小于阳离子型水性聚氨酯,拉伸强度、断裂伸长率大于阳离子型水性聚氨酯,耐水性强于阳离子型水性聚氨酯。     

The influence of the NCO/OH ratio and the 1,6-hexanediol/ dimethylol propionic acid molar ratio on the properties of waterborne polyurethane dispersions based on 1,5-pentamethylene diisocyanate

1,5-Pentamethylene diisocyanate, a novel aliphatic diisocyanate formed from bio-based 1,5-pentamethylenediamine, has been used as a hard segmented material to synthesize polyurethane. In this study, several waterborne polyurethane (WPU) dispersions have been successfully prepared by a prepolymer process from 1,5-pentamethylene diisocyanate poly(polyether) with different NCO/OH ratios and 1,6-hexanediol (HDO)/dimethylol propionic acid (DMPA) molar ratios. The Fourier transfonn infrared (FTIR) spectra, thermogravimetric analysis, differential scanning calorimetry, X-ray diffiraction, and a mechanical tensile test were used to investigate the structures, thermal stability, phase separation, crystallinity, mechanical properties, and adhesive performance of the WPU dispersions. The FTIR results indicate that the degree of hydrogen bonding and the numbers of urea groups increase as the NCO/OH ratio and HDO/DMPA molar ratio increase. Furthermore, the phase separation increases and the thermal stability decreases as the NCO/OH ratio increases or the HDO/DMPA molar ratio decreases. Finally, WPU3.0-2.4 (NCO/OH = 3, HDO/DMPA = 2.4) exhibits a maximum tensile strength and shear strength, pointing to its possible use as an adhesive. These results could provide a very valuable reference for industrial applications of WPU.     

NCO含量对水性聚氨酯乳液性能影响的研究

以自制聚酯多元醇和过量的2,4一甲苯二异氰酸酯为原料进行预聚反应,合成含异氰酸酯端基的预聚体,再以二羟甲基丙酸为亲水剂,引入二元醇进行扩链反应,制备了水性聚氨酯。研究了残留NCO含量及NCO／OH比值对乳液合成及性能的影响。研究认为控制NCO／OH比值在2．0～2．5之间,残留NCO含量在3．0％～3．5％之间时,制备的乳液性能最佳。     

高固含量水性聚氨酯分散体的合成

引　言水性聚氨酯是水溶型、水分散型和水乳化型聚氨酯的统称 .水性聚氨酯与溶剂型相比较 ,具有生产、运输和使用安全 ,不污染环境的优点 ,在涂料、黏合剂和皮革涂饰剂等方面的应用备受重视[1] ,成为近 10年来全世界的研究热点 .水性聚氨酯的弱点是其制成的涂料和涂饰剂的机械性能、耐水性不如溶剂型聚氨酯 .克服这些弱点 ,是近年来各国研究者努力的方向[2 ] .在改善水性聚氨酯性能方面有大量研究报道 ,诸如降低亲水基团含量 ,增大乳液粒径 ,采用强力机械分散增加乳液贮存稳定性 ,改善乳液对涂膜基材表面的润湿性、黏附力等等[3] .但很少见…     

水性聚氨酯／丙烯酸酯分散液的制备及其对酚醛树脂的改性

采用自乳化法制备水性聚氨酯／丙烯酸酯（PU／PA）分散液,考查了二羟甲基丙酸用量、nNCO／nOH（R值）、交联剂、封端剂、中和剂、环氧树脂用量及丙烯酸酯用量对聚氨酯／丙烯酸酯分散液稳定性的影响。将此分散液与酚醛树脂共混,制备出改性酚醛树脂胶粘剂。结果表明,聚氨酯／丙烯酸酯分散液的加入使酚醛树脂的常温和高温粘接强度显著增加。     

Comparative Properties of Hydrophilic and Hydrophobic Fumed Silica Filled Two-Component Polyurethane Adhesives

Two fumed silicas, one hydrophilic and another hydrophobic, were added to a two-component polyurethane (PU) adhesive and their properties compared. The filled polyurethanes were characterized by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and water and diiodomethane contact angle measurements. The adhesive strength was evaluated from single lap-shear tests of solvent wiped stainless steel/polyurethane adhesive joints. The fumed silicas were well-dispersed in the polyurethane matrix as bundles of nanometric spherical silica particles. However, some micron size agglomerates of fumed silica appeared in the filled polyurethane. The addition of fumed silica favoured the degree of phase separation between the hard and the soft segments in the polyurethane. The polyurethanes were not fully cured under the conditions used in this study and the addition of fumed silica inhibited the curing reaction; the extent of the curing reaction was not affected by the hydrophilic or hydrophobic nature of the fumed silica. The filled polyurethanes were further cured during DSC experiments and this was noticed by the appearance of the melting of the hard segments and the displacement of the second glass transition to a higher temperature. On the other hand, the addition of fumed silica increased the wettability and the surface energy of the polyurethane; this increase was mainly due to an increase in the polar component of the surface energy. The increase in surface energy is somewhat more marked in the case of the hydrophilic silica filled polyurethane, indicating that the polarity of the fumed silica affected the surface properties of the polyurethane. Finally, the addition of the hydrophilic fumed silica increased the adhesion of the filled polyurethane adhesive to stainless steel which was in agreement with the higher surface energy of the hydrophilic fumed silica filled polyurethane.     

Synthesis and characterization of waterborne polyurethane dispersion from glycolyzed products of waste polyethylene terephthalate used as soft and hard segment

Waste polyethylene terephthalate (PET) bottles were collected, cleaned and then depolymerized by glycolysis with neopentyl glycol (NPG) and dipropylene glycol (DPG), in the presence of N-butyl titanate catalyst. The product, named glycolyzed oligoesters, obtained through the depolymerization, were employed respectively in hard segment and soft segment in the synthesis of novel waterborne polyurethane dispersions (PUDs) via a simple and environmentally benign process. In addition, a polyurethane dispersion without glycolyzed oligoesters was synthesized as a comparison. The bulk structure of PET glycolyzed oligoesters and PUDs films were characterized by Fourier transform infrared spectroscopy (FT-IR), H-nuclear magnetic resonance (¹H NMR) and Gel permeation chromatography (GPC). The results illustrated that glycolyzed oligoesters were successfully introduced into the hard and soft segment of the polyurethanes. Furthermore, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to investigate the thermal properties of the PET glycolyzed oligoesters and PUDs films. The results showed that the thermal resistance of waterborne polyurethanes obtained with glycolyzed oligoesters increased due to lower degrees of phase separation. X-ray diffraction indicated that all synthesized polyurethanes exhibited reduced degrees of orientation. Due to the balance between hard-/soft-segment of the waterborne polyurethane dispersions, the formulations containing glycolyzed oligoesters within the hard segment sections of the polyurethanes provided the best performance.     

稳定水性聚氨酯分散液的合成研究

以聚酯、聚醚混合低聚物二醇为原料 ,采用二级扩链技术[1] 合成了阴离子分散液 ,并研究了聚酯二醇/聚醚二醇、NCO/OH等因素对其性能的影响 ;当原料为 PBA/PEG=(1～ 4)∶ 1 ,NCO/OH=(1 .5～ 1 .8)∶ 1时能够得到黏度、硬度、柔韧性、吸水率、拉伸强度、断裂伸长率、分散性、机械稳定性等综合性能优良的分散液。     

双重改性水性聚氨酯分散体的合成及应用

以异氰酸酯、聚己内酯二元醇、环氧树脂E-51、二羟甲基丙酸和蓖麻油为主要原料制备了环氧树脂和蓖麻油双重改性的水性聚氨酯分散体。结果表明,当NCO与OH摩尔比为1.3、DMPA添加质量分数为4%~6%、三乙胺中和度为80%时,所得涂膜铅笔硬度H,耐水性72 h无异常,满足了水性木器面漆的性能要求。     

阴离子水性聚氨酯的合成及性能研究

采用甲苯二异氰酸酯、聚醚二元醇和二羟甲基丙酸为主要原料,用预聚体方法合成了阴离子聚醚型水性聚氨酯乳液。探讨了NCO/OH（R值）对水性聚氨酯性能的影响。结果表明,R值为1.4时得到的阴离子聚醚型水性聚氨酯乳液及涂膜性能较好。