Two series of butyl acrylate (BA)/acrylic acid (AA)/2‐hydroxy ethyl methacrylate latexes were produced via starved seeded semi‐batch emulsion polymerization. The first series, five latexes with gel contents ranging from 0 to 75 wt.‐%, were generated by varying the amount of chain transfer agent (CTA, n‐dodecyl mercaptan) in the absence of cross‐linker. The second series, two latexes with gel contents of 49 and 74 wt.‐%, were obtained by manipulating the amount of CTA in the presence of a constant cross‐linker (allyl methacrylate) concentration. Latexes with similar gel contents, one from each series, were compared with respect to their microstructure, viscoelastic properties and pressure‐sensitive adhesive performance. At similar gel contents, latexes obtained in the absence of cross‐linker had larger sol polymer molecular weight ($\overline {M} _{{\rm w}} $ ) and molecular weight between cross‐linking points (Mc), compared to the latexes generated using both CTA and cross‐linker. The different microstructures of latexes with similar gel contents resulted in significantly different viscoelastic properties and shear strength of the pressure‐sensitive adhesive films cast from the latexes.
In a recent paper Destrade [1] studied surface waves in an exponentially graded orthotropic elastic material. He showed that the quartic equation for the Stroh eigenvalue p is, after properly modified, a quadratic equation in p2 with real coefficients. He also showed that the displacement and the stress decay at different rates with the depth x2 of the half-space. Vinh and Seriani [2] considered the same problem and added the influence of gravity on surface waves. In this paper we generalize the problem to exponentially graded general anisotropic elastic materials. We prove that the coefficients of the sextic equation for p remain real and that the different decay rates for the displacement and the stress hold also for general anisotropic materials. A surface wave exists in the graded material under the influence of gravity if a surface wave can propagate in the homogeneous material without the influence of gravity in which the material parameters are taken at the surface of the graded half-space. As the wave number k → ∞, the surface wave speed approaches the surface wave speed for the homogeneous material. A new matrix differential equation for surface waves in an arbitrarily graded anisotropic elastic material under the influence of gravity is presented. Finally we discuss the existence of one-component surface waves in the exponentially graded anisotropic elastic material with or without the influence of gravity. 相似文献
This paper studies the interface curing stresses between polymethyl methacrylate (PMMA) and composite by means of digital speckle correlation method (DSCM). A new method by combining DSCM with the marker points is developed to measure the interface curing stresses, and the measurement principle is introduced. The interface curing stresses between PMMA and composite with different curing bonding conditions are measured and analyzed, this indicates that the residual stress for furnace heating and furnace cooling is the smallest. Finally, the measurement error is discussed by means of finite element method, the influences of glass microsphere between adhesive and PMMA can be ignored. 相似文献
N-Dodecyl mercaptan (NDM) chain transfer agent and allyl methacrylate (AMA) cross-linker were used to manipulate latex properties in a starved seeded semi-batch emulsion polymerization of butyl acrylate (BA) and methyl methacrylate (MMA) or with a third monomer, acrylic acid (AA). Latexes with higher gel content and lower sol polymer molecular weight (Mw) were produced by adding only AMA. On the other hand, latexes with lower gel content and Mw were produced by adding only NDM. In addition, at a constant AMA concentration (0.2 phm), the addition of NDM (0.2 phm) decreased gel content, increased molecular weight between cross-linking points (Mc), and decreased Mw. Adding more NDM (to a total of 0.4 phm) further decreased the gel content, while decreasing the tested Mc and increasing Mw. It was also found that using higher concentrations of both AMA and NDM could produce latex with similar gel content, but smaller Mc and Mw, compared to the latex produced at lower concentrations of both NDM and AMA. Regarding the influence of AA, gel content was increased and Mw was significantly decreased with an increase in AA concentration and a decrease in MMA concentration. The performance of the latexes was evaluated for application as a pressure-sensitive adhesive (PSA). 相似文献
The synthesis, characterization, and testing of a range of novel bio‐inspired L‐DOPA‐derived poly(ester amide)s is presented, using a widely applicable, straightforward chemistry. A model system is used to study and establish the monomer and polymer synthetic protocols, and to provide a set of optimum reaction conditions. It is further shown that fully biobased L‐DOPA‐containing adhesive tapes can be fabricated, which are positively evaluated in terms of their adhesive properties. The newly developed synthetic protocol constitutes a versatile platform for accessing and tailoring a plethora of relevant structures, including a variety of potentially biocompatible poly(ethylene glycol)‐based materials.