有机硅压敏胶粘剂的研究概况

介绍了有机硅压敏胶的性能特点及应用；综述了该胶种在国内外的研究开发的历史及现状，展望了有机硅压敏胶的发展前景。     

压敏胶与压敏制品的市场和技术动向(Ⅱ)

综述美国、西欧、日本、中国及台湾地区等国家或地区的压敏胶与制品的最近市场需求 ,和各类压敏胶与制品的开发和生产技术动向     

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.     

Probing the Near-Surface Composition Profile of Pressure Sensitive Adhesive Films with X-Ray Reflectivity

The composition of pressure sensitive adhesive films as a function of distance from the sample surface is probed with x-ray reflectivity. A two-component statistical copolymer with ethylhexylacrylate as the majority component and methylmethacrylate representing the minority component is chosen as a sample system. Different preparation protocols are employed to tailor the near-surface composition profile. In this context, doctor-bladed films exhibit a different near-surface composition as compared with solution cast samples. For the latter case, a small surface roughness can be ensured by either using slowly evaporating solvents or reducing the solvent evaporation speed by providing an appropriate atmosphere surrounding the drying solution. For freshly prepared samples, the use of non-polar solvents in combination with the corresponding solvent vapor atmosphere leads to a surface enrichment of ethylhexylacrylate whereas a humid environment, independent of the choice of solvent, favors enrichment of the more polar methylmethacrylate. We finally show that the installed composition profiles change with time and depend on the storage conditions.     

CALENDAR OF EVENTS

To elucidate the adhesion mechanism of carbon nanotubes (CNTs) designed to mimic natural contact surfaces in the gecko, their contact behavior was investigated using a scanning electron microscope (SEM) equipped with manipulation stages. The normal adhesion of CNTs increases in direct relation with a preload, which is true also for gecko setae. The CNT shear strength increases concomitantly with increasing CNT length, indicating that the length is an important factor enabling conformation to the surface roughness and enabling generation of a strong contact by side contact. Results revealed the CNT configuration and surface physics as important factors for synthetic gecko adhesion.     

A Practical Criterion for Rheological Modeling of the Peeling of Pressure Sensitive Adhesives

The transient extensional viscosity of non-crosslinked pressure sensitive adhesives (PSA's) and physically-crosslinked PSA's is measured and compared with theoretical predictions based on the linear viscoelastic (LVE) properties of the PSA's and the use of linear and quasi-linear constitutive equations. Based on a previously-derived expression for the relative contributions of individual relaxation modes of a polymeric material to its transient extensional viscosity, a criterion for whether large extensional deformations can be modeled on the basis of the LVE spectrum is proposed and evaluated for each PSA. The relevance to adhesion is demonstrated in peel tests, where the deformation of adhesive is quantified in images of the peel front under the assumption of uniaxial elongation and used to obtain theoretical peel forces in excellent agreement with measurements. This demonstrates the applicability of the criterion to the peeling process.     

新型绿色材料——脂肪族聚酯

近二十年来,人类正面临着在合成材料方面的挑战。一类以聚乳酸及其同系物为代表的、可生物降解的新型合成脂肪族聚酯则有可能成为21世纪的一种“绿色材料”。本文重点介绍了这类脂肪族聚酯的合成方法、性能特征及其应用前景。     

Relationship between the fracture energy and the mechanical behaviour of pressure-sensitive adhesives

Mechanical behaviours of two pressure-sensitive adhesives (PSAs) families, composed of elastomer copolymers or polyacrylate/acrylic copolymers, are characterised by peel tests. Fracture energy varies linearly according to the applied contact force between two levels, which depends on tackiness and cohesion of the PSA. Local fracture energies are measured by an original peeling system and they are related with the adhesive deformation. Mechanical behaviours of PSAs depend on their composition but majority of fracture energy is dissipated on the first millimetre near the bending zone where fibrils elongation is maximum. Observations of interfaces between PSAs and glass substrate underline that fracture energy varies linearly according to the contact area.     

High performance pressure sensitive adhesives by miniemulsion photopolymerization in a continuous tubular reactor

High solids content PU/(meth)acrylics latexes for application as pressure sensitive adhesives (PSAs) were successfully synthesized by miniemulsion photopolymerization in a continuous tubular reactor at room temperature. It was shown that the process is very flexible and the polymer microstructure can be widely changed by simply controlling the radical initiation using different photoinitiator types and concentrations and varying the incident light irradiance. PSAs presenting a whole spectrum adhesive properties were obtained, some of them having the desired and unusual combination of high work of adhesion and maximum shear adhesion failure temperature (SAFT > 210 °C). The adhesive properties were analyzed in terms of the molecular weight distribution of the whole sample measured by asymmetric flow field flow fractionation.     

Acetyl-protected cytosine and guanine containing acrylics as supramolecular adhesives

Hydrogen bonding among nucleobase pairs serves as an efficient noncovalent interaction for designing supramolecular polymers with desired properties for pressure sensitive adhesives. Michael addition yielded acetyl-protected cytosine/guanine containing acrylic monomers with flexible spacers between the hydrogen bonding units and the acrylic backbone. Free radical polymerization of nucleobase-containing monomers afforded acetyl-protected cytosine/guanine homopolymers and random copolymers with n-butyl acrylate. Nucleobase incorporation significantly affected thermal, thermomechanical, rheological, morphological properties, and adhesive performance of polyacrylates. Guanine/cytosine-containing copolymers each exhibited a single glass transition (T_g) that increased with increasing nucleobase content. Self-association of acetyl cytosine and acetyl guanine units converted low T_g polyacrylates to physically crosslinked networks with mechanical integrity. Solution casting acetyl guanine-containing copolymers with 8 mol% or higher guanine content yielded free-standing films with microphase-separated morphologies. Acetyl cytosine-containing copolymers with 15 mol% or more cytosine formed free-standing films with less microphase-separation compared to the guanine copolymers. ¹H NMR titration experiments established a 1:1 binding stoichiometry between acetyl cytosine and acetyl guanine monomers in CDCl_3, similar to guanine-cytosine association. However, the acetyl protecting group hindered the formation of triple hydrogen bonding, resulting in double hydrogen bonding between acetyl cytosine and acetyl guanine with an intermediate binding strength comparable to their self-associations. Acetyl guanine-containing copolymers with 3 mol% acetyl guanine exhibited higher peel strength on stainless steel and higher extended service frequency range compared to cytosine-containing copolymers and various pressure sensitive adhesive controls.     

压敏胶粘剂的技术发展

对水基（ 丙烯酸酯乳液） 、热熔型和射线固化型３ 类环境友善的压敏胶粘剂近几年国内外的主要技术发展进行了介绍和评述。     

Interfacial Energy and Adhesion between Acrylic Pressure Sensitive Adhesives and Release Coatings

The interfacial adhesive behavior between acrylic pressure sensitive adhesive-like networks (PSA-LNs) and poly(vinyl N-alkyl carbamate) release coatings was studied using a contact mechanical method and peel tests. Surface energy and interfacial energy were directly measured in JKR tests using a novel sample construction. The surface energy of the poly(vinyl N-alkyl carbamates) was found to be around 20 mJ/m². Interfacial energies between PSA-LNs and the release coatings were found to be quite high - between 7 and 24 mJ/m². Changes in adhesion dynamics were governed by acid-base interactions between the carbamate in the release coating and the acid groups in the PSA-LN. The length of the alkyl chain in the release coating moderated this effect. We also found a correlation between fundamental adhesion energy and peel strength. Examination of this phenomenon provides a basis for understanding the poor storage stability of PSA tapes made using alkyl carbamates and acid-containing PSAs.     

Interfacial Energy and Adhesion between Acrylic Pressure Sensitive Adhesives and Release Coatings

The interfacial adhesive behavior between acrylic pressure sensitive adhesive-like networks (PSA-LNs) and poly(vinyl N-alkyl carbamate) release coatings was studied using a contact mechanical method and peel tests. Surface energy and interfacial energy were directly measured in JKR tests using a novel sample construction. The surface energy of the poly(vinyl N-alkyl carbamates) was found to be around 20 mJ/m². Interfacial energies between PSA-LNs and the release coatings were found to be quite high – between 7 and 24 mJ/m². Changes in adhesion dynamics were governed by acid-base interactions between the carbamate in the release coating and the acid groups in the PSA-LN. The length of the alkyl chain in the release coating moderated this effect. We also found a correlation between fundamental adhesion energy and peel strength. Examination of this phenomenon provides a basis for understanding the poor storage stability of PSA tapes made using alkyl carbamates and acid-containing PSAs.     

Enzyme-catalyzed Polyester Synthesis

Abstract

Enzyme-catalyzed polymer synthesis has gathered many scientists around a major topic such as the synthesis of polyesters by enzyme catalysis. Since the mid 80′s indeed, it is commonly accepted and experimented that lipases in particular are able to catalyze reverse reactions when they are used in organic media (less data are reported on esterases or proteases). Transposed to polymer chemistry, these pioneering results led to the definition of numerous reaction systems leading to the formation of polyesters. Thus AA + BB and AB + AB-type polycondensations as well as lactones and macrolides polymerizations have been achieved in various organic solvents. In this article, the creation of aliphatic, unsaturated and aromatic polyesters is reviewed with a special attention paid to the equilibria between linear chains and rings.     

Surface Energy and Adhesion Studies on Acrylic Pressure Sensitive Adhesives

The surface energy and adhesion dynamics of pressure sensitive adhesives-like networks (PSA-LNs) as mimics for PSAs were studied using JKR-based contact mechanics and peel tests. Acrylic acid (AA) was co-polymerized with 2-ethyl hexyl acrylate (2-EHA) and 1,6-hexane diol diacrylate (HDDA) to create PSA-LNs. The measured surface energy (27 to 31 mJ/m²) was sensible as surmised from their structure. Acrylic acid content increases the surface energy, threshold adhesion energy and adhesion hysteresis of PSA-LNs. Measurements of adhesion dynamics showed a dependence of adhesion energy to the 0.6–0.8 power of crack speed, depending upon the model chosen for analysis of the data. When compared with actual pressure-sensitive adhesive tape peel tests, the adhesion dynamics data predicted the peel strength. This study shows a direct relationship between threshold adhesion energy, crack propagation mechanics and peel strength measurements.