Crosslinking of isocyanate functional acrylic latex with telechelic polybutadiene. II. Film formation/crosslinking

The mechanism of film formation and crosslinking in a poly(methyl methacrylate/n-butyl acrylate/TMI®) (PMBT) and amino-telechelic polybutadiene (PBD-NH₂) latex blend was studied. Films cast from the latex blends were ultramicrotomed and examined by transmission electron microscopy. The PBD-NH₂ was found to be located primarily at the surface of the PMBT particles due to a crosslinking reaction. Without the possibility of crosslinking (when TMI was absent in the acrylic copolymer), the PBD-NH₂ only formed segregated phases in the acrylic polymer matrix due to the incompatibility of the two polymers. While this PBD-NH₂ could be extracted with toluene, the PBD-NH₂ crosslinked at the PMBT particle surfaces was not extractable. FTIR results showed that the isocyanate groups in the PMBT were completely consumed when the PBD-NH₂ concentration was sufficiently high, indicating that the PBD-NH₂ had diffused and reacted inside the PMBT particles. Thus, the crosslinking reaction was considered to be the driving force for the diffusion of the PBD-NH₂ into the PMBT particles. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 977–984, 1998     

Crosslinking of isocyanate functional acrylic latex with telechelic polybutadiene. III. Application of a diffusion model

The diffusion and reaction of amino-telechelic polybutadiene (PBD-NH₂) in poly(styrene/n-butyl acrylate/TMI®) (PSBT) was studied. A monodisperse poly(St/BA/TMI) seed latex was prepared by semicontinuous emulsion polymerization. Two core/shell latices were also prepared semicontinuously, using the seed latex as the core and poly(St/BA) as the shell. These monodisperse latices were mixed with equivalent amounts of the telechelic PBD-NH₂ artificial latex before casting into films. The consumption of the TMI in these films was monitored by FTIR as a function of time and the NH₂/TMI ratio. The results showed that without the PSB shell, the PSBT particles (80 nm radius) could be penetrated by the PBD-NH₂ completely. A 24 nm PSB shell was found to act effectively as a barrier to preventing the penetration of the PBD-NH₂ inside the particles. This was consistent with previous TEM results, indicating that the crosslinking between the isocyanate in the PSBT particles and the amine in the PBD-NH₂ particles provided the driving force for the chain diffusion. A diffusion model was established for the PSBT/PBD-NH₂ system. Assuming steady-state diffusion, the effective diffusion coefficients were calculated based on the experimental data. This lead to the estimation of the surface coverage of the PBD-NH₂ on the PSBT particles in the latex films. A film formation and crosslinking mechanism was proposed for the PSBT/PBD-NH₂ latex blend system. In the absence of crosslinking reactions, the two incompatible polymers tended to completely phase separate during the film formation. However, with the crosslinking reactions, the PBD-NH₂ will be bound to the PSBT particle surfaces, forming a PSBT-PBD copolymer interphase. This interphase facilitates the diffusion of the PBD-NH₂ into the PSBT particles. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 985–993, 1998     

Effects of carboxyl group on the ambient self‐crosslinkable polyacrylate latices

Ambient curable carbonyl functional acrylic latices were synthesized by incorporating diacetone acrylamide as functional monomer into acrylic copolymer, adipic acid dihydrazide (ADH) was used as curing agent. In this work acrylic acid (AA) and acrylic acid homopolymer (PAA) were used to facilitate the crosslinking reaction. We found that the properties of latex film were different when use AA and PAA as the source of the carboxyl groups separately. The results from the characterization of carboxyl groups of the latex particles demonstrated that the distribution of the carboxyl group on the latex particle surface is optimal for the crosslinking reaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3948–3953, 2007     

API固化反应过程的特性研究

使用不同性能的多官能度异氰酸酯作为水性高分子异氰酸酯(API)胶粘剂的交联固化剂,当主剂与交联固化剂混合均匀时,考察了不同种类羧基丁苯(SBR)胶乳及不同性能的交联固化剂对胶粘剂在固化过程中的黏度、胶接剪切强度和固化速率的影响,探索了API胶粘剂的固化反应机制,并且利用差示扫描量热(DSC)法研究了API胶粘剂的固化反应速率随温度变化的规律。研究结果表明,SBR-1的适用期达到2h,最大剪切强度为5.5 MPa;交联固化剂的种类是影响API胶粘剂适用期和胶接性能的重要因素,环境温度和胶液调配后的放置时间是影响API胶粘剂固化反应速率的重要因素。     

The influence of latex blend composition on crosslinking and mechanical properties

Model reactive latices were synthesized by semicontinuous emulsion copolymerization of n‐butyl methacrylate and acetoacetoxyethyl methacrylate or dimethylaminoethyl methacrylate. The two functional latices were then blended in various ratios to study the influence of blend composition on crosslinking and mechanical properties of the resulting films. Crosslinking was quantified through swelling measurements. It was found that the crosslink density increased with increasing amounts of acetoacetoxy‐functional polymer. In addition, the crosslink density exhibited two maxima, at 30/70 and 70/30 (acetoacetoxy‐functional latex/amino‐functional latex) blend compositions. The mechanical properties of the films were quantified by dynamic mechanical analysis (DMA). It was shown that optimal mechanical properties occurred when the particles packed most efficiently at the 30/70 and 70/30 blend compositions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3774–3779, 2007     

Elastomeric films from structured latexes

A model structured latex that is capable of forming a self-curable elastomeric film under mild temperature conditions was developed. In this model latex system, a small amount of dimethyl meta-isopropenyl benzyl isocyanate (TMI®) was copolymerized with n-butyl acrylate (BA) onto poly(butadiene-co-styrene) [(P(Bd-S)] seed latex particles. In the final stage of the film formation process, the latex particles coalesce with each other, and interdiffusion of PBA-based polymer chains in the shell layers of adjacent structured particles occurs. At this stage, the isocyanate groups in the P(BA-TMI) shell layer would begin to crosslink by either a moisture-cure reaction via trace amounts of water remaining in the latex film or by a post-added crosslinker that contains amine groups. Improved elastomeric properties of the latex film are expected from this kind of “interphase” crosslinking structure. However, latex films prepared from the model P(Bd-S)/P(BA-TMI) core/shell latexes were cracked and brittle, which was explained by the formation of a highly crosslinked/grafted core/shell interphase zone. Saturation of the residual double bonds in the P(Bd-S) seed latex particles by hydrogenation was found to be an effective way to reduce the development of the interphase zone and the degree of crosslinking during the second-stage polymerization. An elastomeric film with good mechanical and anti-aging properties was formed from this hydrogenated-P(Bd-S)/P(BA-TMI) structured latex. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1143–1152, 1997     

Natural rubber–styrene butadiene rubber latex blends: Time-dependent rheological behavior and film formation

This article focuses mainly on the effect of maturation time on the rheological behavior of unvulcanized natural rubber (NR)–styrene butadiene rubber (SBR) latex blends. Viscosity shows a composition-dependent behavior with maturation time. It was found that there is a marginal decrease in viscosity for all the systems with maturation time except for the 70/30 NR–SBR blend. In this blend, there is a sharp decrease in viscosity with maturation time. This is associated with the exchange of stabilizers with one another until an equilibrium is reached; that is, all the particles of the blend are stabilized with random mixture of stabilizers. The structural build up observed in 70/30 NR–SBR blend was found to be diminished as the maturation time increases. At equilibrium, there is no further exchange of stabilizers. The behavior of this blend has been explained with the help of a schematic model. The effects of blend ratio and surface active agents on the viscosity were also studied. In addition, the time-dependent flow behavior of prevulcanized latex blends was evaluated as a function of vulcanizing systems and prevulcanization time. There is a regular increase in viscosity with prevulcanization time. However, after 3 h, the viscosity of almost all blends levels off, indicating that the curing reaction is complete within this time. Finally, the morphological changes occurred during film formation of the blends were studied using scanning electron microscopy. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1473–1483, 1998     

环氧乳液与含氟乳液的拼混研究

运用种子乳液聚合法制备了固含量(固体质量分数)为45%的含氟乳液;运用后乳化法制得了环氧乳液。ATR-FTIR测试表明环氧乳液与含氟乳液进行了有效的拼混。运用KrussK12型动态表面能分析仪测试了含氟涂膜对水和十六烷的接触角,对影响拼混乳液涂膜性能的因素如环氧树脂及其固化剂的比例、氟原子含量、成膜基材材质、成膜温度等进行了探讨研究。结果表明制备的含氟拼混乳液性能良好。     

环氧改性丙烯酸乳液涂料的研制

采用三元复合乳化剂体系和核壳乳液聚合工艺,制得环氧树脂改性的苯丙乳液。研究了乳化剂、反应温度、环氧树脂的用量、三乙烯四胺固化剂对环氧改性苯丙乳液综合性能的影响,确定了适宜的反应条件和配方。     

自交联含氟乳液与水性环氧树脂共混乳液自分层的研究

为制备出高性能、低成本的含氟树脂,在优选出环氧固化剂的基础上,将含氟乳液与环氧乳液共混,研究了共混乳液间表面张力差、共混工艺、GMA(甲基丙烯酸缩水甘油酯)用量对共混树脂自分层的影响。控制好这些影响因素,利用光电子能谱(XPS)、差示量热扫描(DSC)对共混乳胶膜进行了表征、分析。结果表明,成膜时树脂会产生自分层,表层富集含氟树脂,底层则以环氧树脂为主,中间依靠两种树脂中的反应基团形成过渡层,这样得到的涂膜具有优异的表面性能和良好的附着性能,经一次涂装就能达到底表合一的效果,乳胶膜的附着力达到了1级。该研究成果已顺利通过中试。     

高分子附聚法制备超大粒径聚丁二烯胶乳

以自制丙烯酸胶乳为高分子附聚剂,以粒径300nm聚丁二烯胶乳(PBL-0700)为起始胶乳,采用高分子附聚法制备了500～600nm超大粒径聚丁二烯胶乳(目标胶乳),考察了附聚剂加入量、放置时间、后稳定剂的加入、附聚温度等因素对目标胶乳粒径的影响,确定了高分子附聚法超大粒径聚丁二烯胶乳制备工艺。     

质感型水包水多彩涂料的彩粒稳定性研究

选用亲水性异氰酸酯作为固化剂,硅酸镁锂作为保护胶,以分散体型羟基丙烯酸树脂和聚丙烯酸弹性乳液复配得到分散相,利用硅酸镁锂层间可交换的阳离子与羟乙基纤维素中的羟基之间的“凝胶化”反应,同时辅以羟基丙烯酸树脂与亲水性固化剂的交联作用来制备综合性能优异的质感型水包水多彩涂料。实验结果表明：当乳液复配比在 1∶4且掺量为 30%,固化剂的—NCO与羟基树脂的—OH物质的量之比为 1∶2,高浓度保护胶溶液掺量为 4%时,所制备的彩粒具有强度适中、色彩饱满度高、抗渗色能力较强,施工喷涂顺畅、无流挂,体系贮存稳定等特点,解决了水包水多彩涂料在生产和施工过程中常常出现的彩粒渗色、彩粒易破碎、喷涂均匀性欠佳等问题。     

高羟基含氟丙烯酸乳液的合成及性能研究

以丙烯酸酯类单体作为原料,以过硫酸钾为引发剂,采用预乳化半连续乳液聚合方式合成了高羟基丙烯酸乳液,并在后期补加氧化还原体系引发剂,提高了单体的转化速率。系统地研究了乳化剂用量、羟基单体、氟单体、硅单体含量等因素对涂膜性能的影响。最后,将制备的丙烯酸羟基组分同水性固化剂配制成双组分水性丙烯酸聚氨酯清漆,并分析清漆的性能。     

Agglomeration of polybutadiene latex by highly carboxylated functional microspheres

Polybutadiene latex (PBL) was agglomerated by highly carboxylated core-shell agglomerating agents, which contained carboxyl groups in the shell polymer [core monomers (methyl methacrylate, n-butyl acrylate, and ethyl acrylate)/shell monomer (acrylic acid)]. The effects of different parameters upon the particle size of agglomerated PBL were investigated, namely, agglomeration time, amount of agglomerating agent, pH of dispersion medium, amount of acrylic acid and combination of core monomers. The particle growth mechanism was also examined. © 1999 Society of Chemical Industry     

Adhesive behavior of polyurethane‐based materials

The role of prepolymer on the interfacial strength of polyurethane‐based assemblies is examined for two hydroxyl‐terminated (telechelic) polybutadienes, R45M and R45HT. Although it is known that both prepolymers lead to very different adhesive behavior, the reasons that explain this are not understood. In this study, we show that two main effects have to be considered: the length of the free chains, which can diffuse across the interface during the formation of the joint and the relative reactivity of the various hydroxyl groups of the chains and chain extenders with the isocyanate. The R45M chains are more efficient connectors than the R45HT chains. Migration of chain extenders and isocyanate over large distances creates a thick interphase where physical crosslinks appear. This interphase is thicker for R45M‐based polyurethane showing the role of the chain reactivity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 665–671, 2000     

高耐水性自交联丙烯酸酯弹性乳液的研究

使用羧基官能单体甲基丙烯酸，自交联剂N－羟甲基丙烯酰胺（N－MA）和助交联剂的丙烯酸β-羟乙酯（HEA）合成了微交联弹性丙烯酸酯乳液，其乳液涂膜的耐水性明显提高。     

水性环氧树脂涂料固化机理的研究

以自制水性环氧树脂固化剂与自制的E型非离子型水性环氧树脂乳胶混合,于室温下固化交联,观察固化效果与涂膜性能,探究其固化机理,并提出固化模型,以期指导固化剂的结构设计。利用粒径分析、激光共聚焦显微镜(LSCM)、透射电镜(TEM)、扫描电镜(SEM)、原子力显微镜(AFM)等测试方法,对其固化过程和固化效果进行了表征。结果表明:固化剂胶粒吸附于水性环氧树脂胶粒表面,随水分挥发,二者相互扩散、融合、交联,但扩散快于交联,最终固化均匀完全,涂膜致密均一。     

Investigation on the film surface and bulk properties of fluorine and silicon contained polyacrylate

A series of fluorine and silicon acrylic latexes have been prepared from acrylic monomers, 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA) and vinyltriethoxysilane (VTES) via emulsion polymerization. Morphology and particle size distribution were evaluated by transmission electron microscopy (TEM) and dynamic light scattering (DLS) methods. Surface properties of latex films were investigated in terms of ATR-FTIR spectrometry, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and water resistance measurement. It is indicated that fluorine content at the surface of fluorosilicone acrylic film decreased as the film forming temperature was increased. A high temperature favored silicon condensation at the film surface, which limited migration ability of fluorine chains. Fluorine segment contributed to surface hydrophobicity while silicon component was beneficial to improve water repellency of the film bulk. Silicon containing particles were more difficult to coalesce than fluorine acrylic particles due to the rigid crosslinked network derived from silanol crosslinking.     

Improvement of Physicochemical Properties of Rubber Blends Between Nonirradiated and Irradiated Rubber Latexes by Radiation Vulcanization

Abstract

Nonirradiated natural rubber latex (NRL) and irradiated (12 kGy) rubber latex were blended in ratios of 100:0, 85:15, 65:35, 50:50, 35:65, 15:85, and 0:100 (v/v) to improve properties of the rubber latex. The blends were irradiated using different irradiation doses (0–20 kGy) in the presence of a radiation vulcanization accelerator (RVA), normal butyl acrylate (n-BA). The physicochemical properties of the nonirradiated latex, irradiated latex, and blend films were determined after leaching with distilled water. It was observed that the tensile strengths of the blend films increases with an increase in the content of the irradiated proportion and radiation doses. The composition of the blends and the doses of radiation were optimized. The maximum tensile strength (31.41 MPa) was found for the 50:50 composition of the blend with a 5 kGy radiation dose. The 100:0 blends, when irradiated, give the highest tensile strength (27.69 MPa) with 12 kGy but a 15:85 nonirradiated blend gives the tensile strength of 26.18 MPa.     

纳米SiO_x补强天然乳胶膜抗剪切机理的研究

使用合适表面处理剂,通过剪切、搅拌混合和超声波处理,制备了高浓度n—SiOx分散悬浮液;在合适的剪切强度下,将分散悬乳液按n-SiOx质量分数为2.0%均匀分散在天然乳胶中,制备了n-SiOx补强型天然乳胶膜试样。乳胶膜直角撕裂强度测试结果和扫描电子显微镜图像分析表明,n-SiOx粒子较好地分散在天然乳胶中,能与乳胶分子链形成较为牢固的整体结构,其剪切强度较白炭黑试样提高了52.32%;n-SiOx悬浮液浓度是实验的主要影响因素,超声波分散时间、25G工作头转速和均质分散时间次之。