Preparation and rheological studies on the solvent based acrylic pressure sensitive adhesives with different crosslinking density

On the basis of synthesis of a series of solvent based acrylic pressure sensitive adhesives (PSAs) with different crosslinking density, the thermal and rheological properties were characterized. T_g values were increased after crosslinked with MDI, and the thermal stability was also improved. Rheological studies were performed via frequency sweep, amplitude sweep, temperature sweep patterns, respectively. The creep recovery properties were also researched. In this way, it was proved that the linear viscoelastic (LVE) range was elongated as the feeding MDI increased, the elastic modulus (G′) of the acrylic PSAs was obviously increased after crosslinked with MDI whereas hardly making any change to the viscous modulus (G″). In the frequency sweep pattern, the PSAs samples behave as pseudoplastic non-Newtonian fluid; and zero shear viscosity increased as the feeding MDI mass ratio was increased, after discussing the cross-over frequency (?^?) and the relaxation time t_R, it can be concluded that the addition of MDI would make for the improvement of the elasticity of the PSAs; in the temperature sweep pattern, it could be seen that the cross-over temperatures (where G″=G′) were 34 and 70 °C for the samples crosslinked with 0 wt% and 0.1 wt% MDI, respectively. When the mass ratio of MDI fed was higher than 0.1 wt%, even though the temperature increased to 120 °C, the samples remained elastic (G′>G″). In the creep recovery test, it was noteworthy that as the feeding ratio of MDI was increased, the creep recovery properties of the acrylic PSAs were substantially improved. And for the same sample, as the applied constant stress increased from 200 to 1000 Pa, the recoverable proportion of the materials was principally not changed in that all the experiments were carried out within the linear viscoelastic range of the samples. And the sample crosslinked with 0.5 wt% MDI shows the highest 180° peel stress.     

Optical properties and adhesion performance of optically clear acrylic pressure sensitive adhesives using chelate metal acetylacetonate

Optically clear acrylic pressure-sensitive adhesives (PSAs) with different co-monomers were synthesized. This study employed metal chelate aluminum acetylacetonate and zirconium acetylacetonate as curing agents. The optical properties of the acrylic PSAs were examined by UV–visible spectroscopy and a prism coupler. In addition, the adhesion performance was obtained by assessing the peel strength, the tack, and the shear adhesion failure temperature. The decrease in the adhesion performance may be related to a higher crosslinking density, which also resulted in a higher gel content.     

Rheological and adhesion properties of acrylic pressure‐sensitive adhesives

Different pressure‐sensitive adhesives (PSAs) based on acrylic monomers were synthesized under different reaction conditions. The synthesized PSAs have good adhesive properties and without leaving any residue can be easily peeled off from the surface of a substrate. The relationship between PSAs rheological behavior and its adhesion properties (e.g., peel, tack, and shear resistance) has been studied at constant adhesive thickness. The samples were examined for their surface energy and viscoelastic characteristics. It was observed that increase in reaction temperature and reaction time results in decreased storage modulus due to lowered molecular weight, which finally leads to lower elasticity of the PSA. While the storage (G′) and loss (G″) modulus of samples increase with increased initiator concentration, the elasticity of PSA is increased as well. High G″ at high frequency (100 Hz) represents high peel strength because of higher dissipation of viscoelastic energy during debonding. The tack values increase by lowering storage modulus at 1 Hz due to higher M_e. Shear values are increased by higher storage modulus at low frequency (0.1 Hz) due to hydrogen bonding of the different components. Some parallel investigations on the surface energy of the samples showed that they have different properties because of the nature of different monomeric units with their corresponding orientations. Our results reveal that the peel strength is not affected by surface energy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

丙烯酸酯类压敏胶的合成与性能研究

以丙烯酸丁酯（BA）、丙烯酸异辛酯（2-EHA）、醋酸乙烯酯（VAc）、丙烯酸（AA）、丙烯酸羟丙酯（HPA）为原料,乙酸乙酯为溶剂,过氧化苯甲酰为引发剂制备了五元共聚丙烯酸酯类压敏胶。考查了软单体组成、软硬单体配比、丙烯酸用量、丙烯酸羟丙酯加量、增粘树脂对压敏胶性能的影响。实验结果表明,当软单体m2-EHA：mBA=2：1、软硬单体的质量比为6：1、丙烯酸用量为5％、丙烯酸羟丙酯加量为8％、松香用量为5g时,压敏胶性能较佳。     

Molecular weight and crosslinking on the adhesion performance and flexibility of acrylic PSAs

Acrylic pressure sensitive adhesives (PSAs) are used in the production of flexible displays. Acrylic PSAs must have high flexibility and recovery to meet the industry demands for flexible displays. For these reasons, acrylic PSAs were designed to determine the effects of molecular weight and cross-linking on acrylic PSAs. Stress relaxation and creep tests were measured with dynamic mechanical analysis to identify the flexibility and recovery of the acrylic PSAs. The molecular weight and glass transition temperature of the PSAs were measured by gel permeation chromatography and differential scanning calorimetry. A texture analyzer was used to measure the adhesion performance of the acrylic PSAs. With increasing molecular weight, the adhesion performance increased, especially from 86 to 108 K molecular weight PSAs. This is due to the entanglement of the polymer chains. The stress and recovery of cross-linked acrylic PSAs was much higher than that of neat acrylic PSAs. This result is attributed to interactions between the polymer chains due to cross-linking.     

Crosslinked acrylic pressure sensitive adhesives. 3. Effect of adherend on film formation

The reaction of isocyanate in pressure sensitive adhesive (PSA) films adhered on to various adherends having different surface tensions was monitored by depth profiling using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy.In the latter stages of crosslinking reaction, unreacted isocyanate and its derivatives exist more in the bulk of the PSA than in the interfaces between PSA and adherends which are Teflon sheet and PE film having relatively lower surface tensions. In the case of using stainless steel having relatively higher surface tension as adherend, opposite segregation was observed compared to Teflon and PE.From X-ray photoelectron spectroscopy (XPS), it was revealed that N atoms exist more in surface than in bulk when stainless steel is used as adherend. We conclude that polyisocyanates migrate in the PSA film in order to minimize the magnitude of interfacial free energy between the PSA and the adherend, which leads to the change of surface tension of PSA film.     

Multifunctional propyleneimines-new generation of crosslinkers for solvent-based pressure-sensitive adhesives

This article describes work with the goal of crosslinking pressure sensitive acrylic adhesives (PSA) and a new generation of crosslinkers based on multifunctional propyleneimine derivates. Crosslinking of PSA is an established technology used in many industrial manufacturing processes. New applications and technical specifications stimulate the continuous development of new crosslinking agents with very interesting properties. These new crosslinkers influence physico-mechanical properties of acrylic PSA such as tack, peel resistance (adhesion) and shear strength (cohesion). The weak point of propyleneimine crosslinkers is their very short potlife.     

热塑性弹性体型热熔压敏胶的研究进展

介绍了热熔压敏胶用热塑性弹性体以及增粘树脂的特点、作用以及研究进展,并对热熔压敏胶的发展方向以及应用前景进行了展望。     

有机硅压敏胶的研究进展

主要从溶剂和固化形式两个方面总结了有机硅压敏胶近二十年来的研究进展情况,从中可以看出有机硅压敏胶正朝着环保(低VOC)、节能(低温固化)和功能化的方向发展。     

Novel pyridinium photoinitiators and their applications for the ultraviolet crosslinking of acrylic pressure‐sensitive adhesives

The demand for ultraviolet (UV)‐crosslinkable pressure‐sensitive adhesives (PSAs) has rapidly been increasing. A variety of different PSAs containing new photoreactive pyridinium derivatives have been evaluated for their effectiveness in improving adhesion and cohesion in UV‐crosslinkable PSAs. PSAs have been evaluated with respect to the tack, peel adhesion, and shear strength. This article summarizes the breakthrough technology used to achieve better performances in UV‐crosslinkable acrylic PSAs. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

热熔压敏胶的粘接性能和流变行为的关系

研究了热熔压敏胶初粘性、剥离强度与流变学行为之间的关系。研究发现,用温度扫描方法得到的流变曲线与压敏胶主曲线较为一致,因此可以将其转化为不同弛豫时间下的流变行为。通过调整液体树脂含量,设计出一系列橡胶平台模量保持相对不变的同时,具有不同玻璃化温度的压敏胶配方,其中玻璃化温度相同的压敏胶配方,具有基本相同的环形初粘力和剥离强度。     

Cellulose nanocrystals (CNCs) reinforced acrylic pressure- sensitive adhesives (PSAs) prepared via miniemulsion polymerization

In this study, poly (n-butyl acrylate-co-2-ethyl hexyl acrylate) (P(nBA-co-2EHA)) pressure sensitive adhesives (PSAs) were successfully synthesized in the presence of cellulose nanocrystals (CNCs) via in-situ miniemulsion polymerization. First, the CNCs were prepared via acid hydrolysis of cellulose microcrystals (CMCs) at various temperatures, 42–54 °C, and characterized using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) apparatus. The results showed that hydrolysis of MCCs at 45 °C resulted in CNCs with a well-defined aspect ratio, average length of 206 nm and thickness of 3.9 nm, and the highest crystallinity. Adding further CNC to the copolymer adhesive enhanced the mean particle size of the composite latex and decreased the glass-rubber transition temperature (T_g) of the copolymer matrix. Molecular weights and viscoelastic properties of the resultant PSAs were determined using gel permeation chromatography (GPC) and dynamic mechanical thermal analysis (DMTA), respectively. Adhesion performance of the neat and reinforced PSAs containing 1–5 wt% CNCs was evaluated at room temperature. The results showed that the incorporation of CNCs up to 4 wt% in the copolymer adhesive increased the shear resistance by 518%, peel strength by 176% and probe tack by 13%, while further addition, 5 wt%, lowered the adhesion performance due to a lack of surface wettability.     

环氧化SDS型热熔压敏胶的制备及粘接性能研究

采用苯乙烯-丁二烯-苯乙烯(SBS)和苯乙烯-异戊二烯-苯乙烯(SIS)嵌段共聚物,并配合极性的环氧化SBS(ESBS)和环氧化SIS(ESIS)作为基体材料,制备了环氧化SDS(苯乙烯系热塑性弹性体)型热熔压敏胶。研究了ESBS和ESIS用量对压敏胶的初粘力、持粘力和在不同极性底材上剥离强度的影响。结果表明,随着ESBS和ESIS用量的增加,压敏胶的初粘力和持粘力下降,在聚乙烯(PE)上的剥离强度下降,但在聚氯乙烯(PVC)和不锈钢上的剥离强度先增加后下降。当ESBS和ESIS的质量份数均为20份时,压敏胶的初粘力和持粘力分别为23#和43.6 h,在PVC和不锈钢底材上的剥离强度分别达到0.82 N/mm和1.10 N/mm。     

Influence of polymer microstructure on the performance of post‐treated latex‐based pressure sensitive adhesives

Latex‐based butyl acrylate (BA)/acrylic acid (AA)/2‐hydroxyethyl methacrylate (HEMA) pressure sensitive adhesive (PSA) films with various microstructures were heated to improve their performance. The treated PSA films showed significantly better performance than original latex‐based PSA films with similar polymer microstructures. The effect of the heat treatment depended on the polymer microstructure of the untreated PSA films (or corresponding latices). Decreasing the amount of very small sol polymers (i.e., M_x < 2M_e) in gel‐free untreated PSA films, or both very small (i.e., M_x < 2M_e) and very large sol polymers (i.e., M_x > 20M_e) in gel‐containing untreated PSA films led to treated PSA films with significantly better performance. (Note: M_e is the molecular weight between two adjacent entanglement points in a polymer material.) In addition, simultaneously increasing the sol polymer molecular weight (M_w) as well as the size of the chain segments between two adjacent cross‐linking points (M_c) of the gel polymer in the original PSAs resulted in treated PSA films with better performance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of organoclay and chain-transfer agent on molecular parameters and adhesion performance of emulsion pressure-sensitive adhesives

Organoclay-reinforced pressure-sensitive adhesives (PSAs) based on poly(butyl acrylate-co-vinyl acetate-co-acrylic acid) were prepared in the presence of an organically modified montmorillonite, that is, Cloisite15A (C15A), via in situ batch emulsion polymerization. The effect of C15A and chain transfer agent (CTA) level on the molecular parameters and adhesion properties of resulting reinforced PSA were investigated. Small-angle X-ray scattering (SAXS), gel permeation chromatography (GPC), transmission electron microscopy (TEM), dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC) were used to determine the characteristics of the neat and reinforced PSAs. The adhesion test results showed that the incorporation of C15A up to 1 wt% considerably increased the peel strength, shear and probe tack due to increasing the entanglement density of the PSA copolymer, while further increase lowered the peal and tack properties. Interestingly, the addition of 0.25 wt% CTA in the presence of 1 wt% C15A silicate layers resulted in PSA nanocomposite with the highest peal strength and probe tack. Although the CTA remarkably decreased the shear resistance of the neat PSA, the existence of C15A layers or tactoids in the reinforced PSAs decreased the rate of shear resistance decay due to the good interaction between the C15A and adhesive copolymer chains.     

Crosslinked acrylic pressure‐sensitive adhesives. II. Effect of humidity on the crosslinking reaction

The effect of humidity during storage on the crosslinking reactions of isocyanate groups was investigated with attenuated total reflectance Fourier transform infrared spectroscopy with pressure‐sensitive adhesives composed of poly[ethyl acrylate‐co‐(2‐ethylhexyl acrylate)‐co‐(2‐hydroxyethyl methacrylate)] as a base resin and polyisocyanate as a crosslinker. A peak‐resolving analysis of the amide II region revealed four bands. According to an analysis of the Fourier transform infrared spectra of the model compounds, these four bands were assigned to free urethane linkages, hydrogen‐bonded urethane linkages, free urea linkages, and hydrogen‐bonded urea linkages. As expected, storage under humid conditions led to the formation of free and hydrogen‐bonded urea linkages corresponding to the promotion of isocyanate consumption. Peak resolution of the amide II region was found to be a reasonable way of monitoring urethane and urea linkages during crosslinking reactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3039–3045, 2003     

Explanation of tackifier effect on the viscoelastic properties of polyolefin‐based pressure sensitive adhesives

The effects of three tackifiers on the glass transition temperature, terminal relaxation time, plateau modulus, and steady shear viscosity of polyolefin‐based pressure‐sensitive adhesives (PSAs) were investigated. Free volume theory and the Gordon‐Taylor equation are used to explain the special effects of tackifiers on the glass transition temperature of the PSA systems. The plateau modulus and zero shear viscosities were determined from which entanglements and monomeric friction coefficients were calculated. The terminal relaxation time (related to the whole molecular chain relaxations) was calculated from the plateau modulus and zero shear viscosity. Explanations were offered as to why tackifiers have “paradoxical” effects on the viscoelastic properties of the polyolefin‐based PSA, such as increasing the glass transition temperature but decreasing the plateau modulus of the base polymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Preparation and adhesion performance of transparent acrylic pressure sensitive adhesives for touch screen panel

Transparent acrylic pressure sensitive adhesives (PSAs) comprised semi-interpenetrated structured polymer networks were prepared with different co-monomer compositions. Emphasis was placed on the effect of functional groups in the co-monomer including morpholine and tetrahydrofurane moieties in the typical acrylic PSA formulation. The synthesized acrylic PSA syrups were characterized and the optical properties of the acrylic PSA film were also examined by ultraviolet–visible spectroscopy, haze meter, and prism coupler. Acrylic PSAs exhibit high transparency in the visible wavelength region. Adhesion performance was measured by the peel strength, cohesion strength, and probe tack tests. With increasing 4-acryloyl morpholine monomer concentration in the acrylic PSAs, the peel strength, cohesion strength, and probe tack increased.     

Rheological and physical characterization of pressure sensitive adhesives from bio‐derived block copolymers

Over the past decade, the development of various monomers and polymeric materials from renewable natural resources has received increasing attention. Soybean oil, as one of the most abundant vegetable oils, has been widely used in recent studies. To enhance the reactivity of pure soybean oil, it can undergo through different processes such as acrylation and epoxidation. In this article, we investigated the viability of polymerized acrylated epoxidized soybean oil (PAESO) in the composition of pressure sensitive adhesives (PSAs). We studied the physical and rheological properties of PSAs composed of poly(styrene‐b‐AESO), and five different tackifiers and three plasticizers. To verify the compatibility of the tackifiers with the biopolymer, a library of 15 PSAs was prepared through solvent blending method and tested by differential scanning calorimetry. The viable formulations were then prepared through hot‐melt blending and characterized using 180° peel tester, and advanced rheometric expansion system. Results showed that the combination of an ester of hydrogenated rosin and a high solvating plasticizer with the synthesized biopolymer indicated best performance relative to other formulations. The comparison of this candidate with its petroleum‐based counterpart containing SIS demonstrates promising potential of the material to perform as well as commercialized PSAs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46618.     

Crosslinked acrylic pressure‐sensitive adhesives. I. Effect of the crosslinking reaction on the peel strength

For pressure‐sensitive adhesives (PSAs) composed of poly(co‐ethyl acrylate‐2‐ethylhexyl acrylate‐2‐hydroxyethyl methacrylate) as a base resin and polyisocyanate as a crosslinker, the relationship between the crosslinking reaction and peel strength was investigated. A 90° peel test of cured PSA films under various storage conditions was carried out. At the same time, the isocyanate (NCO) consumption in these PSA films was monitored by attenuated total reflectance/Fourier transform infrared spectroscopy. The peel strength of the PSA compounded with the crosslinker decreased as the NCO groups were consumed. The elevation of the aging temperature promoted the crosslinking reaction and increased the decrement in the peel strength. The peel strength of noncrosslinked and crosslinked PSA films increased with the contact time. A high storage temperature made the increment in the peel strength increase. The addition of the crosslinker to the PSA films reduced the increment in the peel strength. Furthermore, PSA films with residual NCO groups possessed stronger peel strengths than fully cured films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1493–1499, 2003