不同扩链剂对PBS性能的影响

通过熔融溶液相结合的方法合成聚丁二酸丁二醇酯(PBS)预聚物。用异佛尔酮二异氰酸酯(IPDI)、六亚甲基-1,6-二异氰酸酯(HDI)和丁二酰氯(SUC)对PBS预聚体进行扩链改性。采用熔点仪测定PBS的熔点;采用傅里叶变换红外光谱仪对PBS的结构进行了表征;采用凝胶渗透色谱仪、热重仪和万能实验机测定了PBS的摩尔质量及其分布、热稳定性和力学性能;测定失重率,考察不同扩链剂对PBS降解性能的影响。结果表明:PBS扩链后摩尔质量均有显著提高,摩尔质量分布均小于扩链前;且断裂伸长率等力学性能和热分解温度等热性能也都有明显改善。但用不同扩链剂扩链后,PBS降解性能有较大区别。     

丙烯酸酯改性水性聚氨酯树脂合成工艺的研究

以异氰酸酯、聚醚多元醇及二羟甲基丙酸为主要原料,合成了水性聚氨酯预聚体(PU),并且经过扩链、交联、丙烯酸酯复合改性等反应制备了丙烯酸酯改性水性聚氨酯树脂(PUA)。结果表明:对水性聚氨酯进行扩链、交联及丙烯酸酯复合改性,可以使两者优异的性能有机地结合起来,能显著提高水性聚氨酯的拉伸强度、硬度、耐磨性、耐水耐醇性,从而使水性PUA分散乳液胶膜的性能得到明显改善,以满足水性PUA木器漆用的要求。     

三聚氰胺交联改性水性聚氨酯的制备及性能

以异佛尔酮二异氰酸酯和聚丙二醇(PPG-2000)为主要原料,以三聚氰胺为交联剂,采用预交联(产物记为MWPU)和后扩链(产物记为mWPU)两种交联方式合成三聚氰胺交联改性水性聚氨酯乳液,并与以三羟甲基丙烷(TMP)为交联剂制备的改性聚氨酯(产物记为TWPU)进行了对比。通过测量乳液粒径、红外光谱分析、热重分析、力学性能测试、吸液率计算,考察了交联剂种类、用量以及交联方式对改性乳液及其胶膜结构与性能的影响。结果表明,交联改性增大了乳液的平均粒径,提升了胶膜的铅笔硬度,拉伸强度、热稳定性和耐水性,但对附着力的影响不大。用三聚氰胺改性所得胶膜的性能优于用TMP改性,采用预交联方式改性优于后扩链方式。当交联度为5/20时,MWPU胶膜的拉伸强度达到13.45 MPa,硬段最大分解速率对应温度为351℃,软段最大分解速率对应温度达到404℃。     

UV固化环氧丙烯酸酯的增韧研究

对UV固化涂料中常用的环氧丙烯酸酯(EA)进行增韧改性,改善了其脆性大,柔韧性不足的缺点。首先合成一种含聚醚二元醇/聚己内酯二元醇链段的双酯扩链剂,并将其用于EA树脂的增韧改性,最后进行紫外光固化。研究结果如下:随着双酯扩链剂中聚二元醇的分子量的提高,改性EA的黏度、玻璃化温度、拉伸强度、拉伸模量均降低,弯曲性能获得提高;当分子量相近时,采用聚己内酯二元醇合成的扩链剂的增韧效果优于聚醚二元醇合成的样品。     

可生物降解聚乳酸的扩链研究进展

依据聚乳酸(PLA)分子的端羟基和端羧基结构特点,主要综述了近年来以有机小分子扩链改性PLA的方法、机理与应用,分别介绍了端羟基缩聚扩链剂、端羧基缩聚扩链剂以及其他扩链剂在改性PLA中的应用.其中端羟基缩聚扩链剂主要有多异氰酸酯、双环羧酸酐、二酰氯;端羧基缩聚扩链剂主要有二噁唑啉、双环氧化物、二元胺、二元醇.并且简要介绍了其他低聚物如聚乙二醇(PEG)、聚乙醇酸(PGA)、聚己二酸丁二醇酯(PBA)、聚丁二酸丁二醇酯(PBS)、聚占-己内酯(PCL)与PLA共聚提高其摩尔质量及改性方面的研究进展,最后对PLA的改性研究与应用做了进一步的展望.     

丙烯酸酯改性水性聚氨酯的合成及应用研究

以异氰酸酯、聚醚多元醇及二羟甲基丙酸(DMPA)为主要原料,合成了水性聚氨酯(WPU)预聚体;然后采用扩链、交联和丙烯酸酯复合改性等方法制备了丙烯酸酯改性水性聚氨酯(PUA)。结果表明:水性PUA具有丙烯酸酯和聚氨酯(PU)的双重优点,而且其低温成膜性较好、综合性能较优、成本及VOC含量较低;由PUA配制的木器漆,其主要性能均达到HG/T36082-1999标准。     

改性聚氨酯包膜剂的合成与性能研究

用环氧树脂和淀粉改性聚氨酯用作肥料包膜剂。以聚醚多元醇、异氰酸酯、扩链剂、环氧树脂和淀粉等为原料,用溶液聚合法合成了改性聚氨酯弹性体。研究了环氧树脂和淀粉对材料力学性能和降解性的影响,对比了改性材料的缓释和降解等性能。     

PBS及其共聚物扩链前后降解性能研究

通过熔融溶液相结合的方法,合成PBS及P(BS-co-1,2-PS)共聚物,用IPDI做扩链剂对其进行扩链合成,并对其进行降解性能试验.采用熔点仪测定了聚酯的熔点,并采用GPC测定了聚酯的摩尔质量及其分布,并测定失重率,得到影响降解性能的因素.实验结果表明;随着聚合物分子链的增长,熔点逐渐降低;而熔点越低,其降解性能越好.聚酯的摩尔质量越高,降解过程越难进行.     

生物降解性塑料PBS的研究进展

介绍了聚丁二酸丁二醇酯(PBS)的合成工艺,包括溶液聚合法、熔融缩聚法、扩链法等;阐述了PBS的改性途径,包括共混改性、共聚改性、交联改性等;概述了PBS的应用及产业化进程;对PBS的发展前景进行了展望。     

聚硫聚脲的合成与改性及其应用

简单介绍了液体聚硫橡胶的发展与性能,合成了以液体聚硫橡胶为软段,2,5-二氨基．3,6-二甲硫基甲苯(E300)扩链的聚硫聚脲和紫外光固化的聚硫聚脲两种聚硫聚合物,并介绍了用侧链含氨基的聚二甲基硅氧烷对这两种聚硫聚脲聚合物进行表面改性,例举了聚硫聚脲改性聚丁二烯聚脲、增韧环氧树脂胶粘剂和增强聚硫密封胶等的应用。     

Cross-linked amino acid-containing polyanhydrides for controlled drug release applications

Cross-linked amino acid-containing polyanhydrides based on N-trimellitylimido-β-alanine (TMA-ala) or N-trimellitylimido-glycine (TMA-gly) and sebacic acid (SA) were synthesized by copolycondensation using 1,3,5-benzenetricarboxylic acid (BTC) prepolymer as a cross-linking agent. Differential scanning calorimetric (DSC) studies of the insoluble copolymers revealed only one sharp melting transition, indicating their cross-linked and/or randomly copolymeric structure. These cross-linked polymers can degrade completely into water-soluble molecules such as amino acids and natural fatty acid, which can be further metabolized by the body. This is an improvement over the photo-cross-linked polyanhydrides reported in the literature, whose cross-links hydrolyze to poly(methacrylic acid), a non-degradable and non-metabolizable macromolecule with limited biocompatibility. The cross-linked polymers were mixed with p-nitroaniline (PNA) and compressed into discs. In vitro degradation and solute release into physiological media were quantified for up to 70 h. Results showed that, relative to their linear counterparts, cross-linking has little effect on the degradation and solute release of these specific polymers.     

HDI trimer based fluorine containing urethane methacrylates for hydrophobic photocured coatings

In this work, hexamethylene diisocyanate (HDI) trimer based two urethane methacrylates were synthesized by reacting 2-hydroxyethyl methacrylate (HEMA) and a fluoroalcohol with HDI trimer. Due to the high viscosity of the fluorinated methacrylates, they were applied onto glass substrates after mixing with tripropylene glycol diacrylate (TPGDA). The performance of the fluorinated resins were compared to a fluorine free HDI trimer based trimethacrylate. The TPGDA diluted formulations were better in terms of surface wettability than the neat resins. TPGDA diluted fluorinated resins exhibited a water contact angle of 109°± 2. All coatings exhibited high surface hardness (4H and 5H) and good adhesion.     

Surface/interfacial changes during polyurethane crosslinking: A spectroscopic study. V *

Crosslinking reactions and stratification processes in polyurethane films were investigated using attenuated total reflectance (ATR) FTIR spectroscopy. The HDI trimer levels near the film–substrate (F–S) interface appear to increase at the early stages of reactions, and after reaching a maximum, decrease. This is attributed to solvent depletion and subsequent film shrinkage, thus causing local NCO concentration changes. At the later stages of crosslinking reactions, stratification of the 1,6-hexamethylene diisocyanate (HDI) trimer occurs, with higher concentration levels at shallower penetration depths from the F–S interface. At the same time, NCO-containing groups assume preferentially parallel orientation to the F–S interface. On the other hand, H-bonded carbonyl groups tend to orient themselves in a perpendicular direction. Quantitative analysis indicates that at extended reaction times the amount of H-bonded CO groups at shallower penetration depths increases and their orientation tends to be more random, which is correlated with migration toward the F–S interface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2045–2054, 2001     

Perfume‐containing polyurea microcapsules with undetectable levels of free isocyanates

Core‐shell polyurea microcapsules with a 40% fragrance load were prepared by interfacial polymerization of guanidine and a technical polyisocyanate prepolymer containing mainly the biuret trimer derived from hexamethylene di‐isocyanate (HDI). Residual free polyisocyanates were still present at a level slightly above 100 mg NCO functional group per kg as determined by liquid chromatography hyphenated with tandem mass spectrometry of HDI and of its biuret trimer. This level was decreased by a factor of about 10 when the polymerization process was allowed to proceed for a longer time and by a factor of about 500 when guanidine or NaOH were added to the microcapsule suspension to act as scavengers. In these cases, polyisocyanate conversion was observed to proceed for about one month when the microcapsules were stored at room temperature before reaching a plateau at a level below 1 mg NCO/kg. Overall, ammonia was the most efficient polyisocyanate scavenger as no residual HDI biuret trimer and only less than 2 μg NCO/kg as HDI were detected at the end of the process, a level which had dropped below the limit of detection of 0.25 μg NCO/kg after about 40 days of aging at room temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

扩链剂结构对脂肪族水性PU性能的影响

以六亚甲基二异氰酸酯(HDI)和聚环氧丙烷醚二醇(PPG)为主要原料,二羟甲基丙酸(DMPA)为亲水性扩链剂合成了聚氨酯预聚体,再经过不同小分子扩链剂扩链、乳化制备水性聚氨酯(WPU)乳液,然后与自制交联剂HM交联成膜.研究了不同扩链剂对聚氨酯乳液稳定性及涂膜力学性能的影响.结果表明,以脂肪族二醇扩链的WPU乳液的外观好于芳香族二酚,而芳香族二酚扩链的WPU涂膜力学性能优于脂肪族二醇.     

Polymerization of aqueous lactic acid to prepare high molecular weight poly(lactic acid) by chain-extending with hexamethylene diisocyanate

In order to synthesize the high molecular weight poly(lactic acid) [PLA], Hexamethylene diisocyanate [HDI] was used as a chain extender connecting the terminal group of polymers. Poly(lactic acid) of high molecular weight, 76000 (M_W) and 33000 (M_n), was obtained by using antimony trioxide catalyst after chain-extending with HDI. Without chain-extending, the molecular weight of PLA was about 7000 (M_n). T_m in the 2nd-scan DSC thermogram was not found when PLA was chain-extended with HDI. In order to check the degree of crystallization of polymers, annealing of these polymers was carried out at 120 °C. Peaks of XRD (X-Ray Diffraction) were sharpened as the duration of annealing was lengthened. The analysis of polymers reacted with HDI by ¹H-NMR showed the broad peaks at 1.32 and 3.14 ppm assigned to HDI units. The molecular weight of polymers increased with the increase in the mole ratio of-NCO/-OH.     

Kinetics and mechanisms of catalyzed and noncatalyzed reactions of OH and NCO in acrylic polyol–1,6‐hexamethylene diisocyanate (HDI) polyurethanes. VI

Fourier transform infrared spectroscopy was used to study the kinetics of noncatalyzed and catalyzed polyurethanes. These studies show that for noncatalyzed acrylic polyol–hexamethylene diisocyanate (HDI) trimer reactions, the reactions between OH and NCO of HDI exhibit second‐order kinetics, with first‐order kinetics with respect to NCO and OH. On the other hand, when dibutyltin dilaurate (DBTDL) is used as a catalyst in acrylic polyol–HDI trimer reactions, the reaction rate is first order with respect to NCO and 0.5 order in OH and DBTDL concentrations. A mechanism for the catalyzed acrylic polyol–HDI trimer crosslinking reactions is proposed and it appears that an equilibrium involving associations between OH and DBTDL exists, resulting in the formation of an active anion, which interacts with NCO to generate polyurethanes. To further verify this mechanism, the influence of acidity on the reaction rate constant was investigated. When the acidity of the system is increased, retardation of urethane formation occurs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2322–2329, 2002     

Enhancement of physical properties of thermoplastic polyether-ester elastomer by reactive extrusion with chain extender

The branched thermoplastic polyether-ester elastomer (TPEE) and diisocyanate compound was melt extruded in an effort to enhance melt viscosity for the blow moulding process. The chain-extended TPEE was prepared with melt condensation of a branched TPEE and 4,4′-diphenylmethane diisocyanate (MDI) for enhancement of the molecular weight of TPEE. The effects of MDI contents as a chain extender on melt, thermal, mechanical and rheological properties of the chain-extended TPEE were investigated. By using a solution and melt viscosity analysis, the chain-extended TPEE was found to be an enhancement of molecular weight and a lightly cross-linked structure. The intrinsic viscosity (IV) increased and melt flow index (MI) decreased with an increasing amount of MDI due to the reaction between the hydroxyl end groups of TPEE and isocyanate groups of MDI. The chain-extended TPEE does not lead to an important drop in elongation at break. The tensile strength and the tear strength are characterized by a significant increase, compared with a branched TPEE. The storage modulus, loss modulus and the complex viscosity of the chain-extended TPEE were also higher. The modified Cole–Cole plots revealed that the chain-extended TPEE shows a higher elasticity than the branched TPEE. The chain-extended TPEE has more suitable melt and rheological properties for the blow moulding processes.     

Thiourethane thermoset coatings from bio‐based thiols

Three bio‐based thiols were synthesized via the thermal thiol‐ene reactions between sucrose soya ester (SSE) and multifunctional thiols; then, thiourethane coatings were produced from these thiols and their coating properties were studied. A series of high bio‐renewable content thiol oligomers were synthesized according to the previously reported thermal thiol‐ene reaction. Fourier transform infrared spectra (FTIR) confirmed the complete consumption of the double bonds in SSE, and gel permeation chromatography confirmed the formation of high‐molecular‐weight oligomers. The viscosity of these oligomers remained low due to their compact and branched structures. Thermoset thiourethane coatings were prepared from these thiol oligomers and polyisocyanate trimer resins with dibutyltin diacetate as the catalyst. FTIR spectra confirmed the formation of the thiourethane group. However, coatings based on isophorone diisocyanate (IPDI) polyisocyanate resin showed a lower degree of cure because of the decreased resin mobility due to the rigid cyclohexane ring. Generally, all the coatings showed good adhesion to aluminum panels, and had high gloss. However, they exhibited low tensile strength, modulus and chemical resistance due to the flexibility of the fatty acid chain. Coatings based on more rigid IPDI‐based polyisocyanate showed higher T_g, hardness and direct impact resistance compared with the hexamethylene‐diisocyanate (HDI) based polyisocyanate counterparts. Thermogravimetric analysis results showed that coatings based on mercaptanized soybean oil have better thermal stability than those from di‐pentene dimercaptan or glycol di‐3‐mercaptopropionate. Two T_g values were found by both differential scanning calorimetry and dynamic mechanical thermal analysis of thiourethanes from HDI‐based polyisocyanate and di‐pentene dimercaptan or glycol di‐3‐mercaptopropionate based oligomers due to phase separation resulting from the poor compatibility between HDI‐based polyisocyanate and the respective oligomers. Copyright © 2011 Society of Chemical Industry     

双季铵碱催化HDI三聚反应动力学研究

以双季铵碱为催化剂,采用溶液聚合工艺对HDI进行三聚反应,气相色谱测定三聚反应体系中游离HDI的含量,研究了HDI三聚反应的动力学规律。结果表明,HDI三聚反应过程的前期反应阶段为三级反应,动力学方程为γ1=kc3,k=1.71×10-5h-1。