Shear strength of adhesively bonded polyolefins with minimal surface preparation

Interest in polyethylene and polypropylene bonding has increased in the last years. However, adhesive joints with adherends which are of low surface energy and which are chemically inert present several difficulties. Generally, their high degree of chemical resistance to solvents and dissimilar solubility parameters limit the usefulness of solvent bonding as a viable assembly technique. One successful approach to adhesive bonding of these materials involves proper selection of surface pre-treatment prior to bonding. With the correct pre-treatment it is possible to glue these materials with one or more of several adhesives required by the applications involved. A second approach is the use of adhesives without surface pre-treatment, such as hot melts, high tack pressure-sensitive adhesives, solvent-based specialty adhesives and, more recently, structural acrylic adhesives as such 3M DP-8005^® and Loctite 3030^®.In this paper, the shear strengths of two acrylic adhesives were evaluated using the lap shear test method ASTM D3163 and the block shear test method ASTM D4501. Two different industrial polyolefins (polyethylene and polypropylene) were used for adherends. However, the focus of this study was to measure the shear strength of polyethylene joints with acrylic adhesives. The effect of abrasion was also studied. Some test specimens were manually abraded using 180 and 320 grade abrasive paper. An additional goal of this work was to examine the effect of temperature and moisture on mechanical strength of adhesive joints.     

Lewis Pair Polymerization of Acrylic Monomers by N-Heterocyclic Carbenes and B(C6F5)3

This work has uncovered the first highly active and efficient Lewis pair polymerization (LPP) system based on N-heterocyclic carbene (NHC)/B(C₆F₅)₃ pairs for converting acrylic monomers into medium- to high-molecular weight polymers. The study has systematically examined steric and electronic effects of three 1,3-dialkyl(Me, ⁱPr, ^tBu)imidazol-2-ylidene NHCs on the LPP of three classes of acrylic monomers, including linear methyl methacrylate (MMA), cyclic biorenewable γ-methyl-α-methylene-γ-butyrolactone (_γMMBL), and difunctional allyl methacrylate (AMA). For MMA polymerization, IⁱPr is not only the most active (∼3× and ∼120× more active than IMe and I^tBu, respectively), but also the most effective NHC, especially under low NHC loading conditions. Kinetic results are consistent with a bimolecular, activated monomer propagation mechanism. In the case of the more reactive _γMMBL, the polymerization by NHC/B(C₆F₅)₃ in CH₂Cl₂ is extremely rapid, with all three NHCs achieving quantitative monomer conversion in 1 min and thus reaching a high turnover frequency of≥48,000 h⁻¹. The molecular weight (MW) of P_γMMBL can be tuned by adjusting the [_γMMBL]/[NHC] ratio, and thus high MW polymers with relatively narrow MW distributions can be readily synthesized (e.g., from M_n=1.41×10⁵ g mol⁻¹, Đ=1.08 to M_n=4.89×10⁵ g mol⁻¹, Đ=1.20). The LPP by NHC/B(C₆F₅)₃ is completely chemoselective, as demonstrated by the polymerization of AMA, which selectively polymerizes the conjugated vinyl group while leaving the non-conjugated vinyl group in the allyl moiety intact, thanks to its activated monomer propagation mechanism. The resulting PAMA is syndiotactic (rr=83 %), uncross-linked, and soluble in common solvents, thus suitable for further functionalization. This quantitatively chemoselective polymerization by NHC/B(C₆F₅)₃ should provide a facile, yet powerful, approach to functional acrylic polymers.     

Anaerobic Adhesive Cure Mechanism-I

Anaerobic adhesives are single-component acrylic adhesives which cure rapidly at or below room temperature when air is excluded, but they remain in an uncured stage over a long time when they are exposed to an adequate supply of air. Thus, anaerobic adhesives are widely used in retaining compounds for nuts and bolts, in sealants, and for impregnation. Recently, anaerobic adhesives have also been used in electrical and electronic applications because of their fast room temperature cure capability and their convenience.¹     

Anaerobic Adhesive Cure Mechanism-II

Anaerobic adhesives are single-component acrylic adhesives which cure rapidly at or below room temperature when air is excluded, but they remain in an uncured stage over a long time when they are exposed to an adequate supply of air. Thus, anaerobic adhesives are widely used in retaining compounds for nuts and bolts, in sealants, and for impregnation. Recently, anaerobic adhesives have also been used in electrical and electronic applications because of their fast room temperature cure capability and their convenience.     

Properties of powdered associative alkali‐swellable acrylics thickeners synthesized by precipitation polymerization

Powdered alkali‐swellable acrylics thickener (ASAT) was synthesized by precipitation polymerization with acrylic acid (AA) and stearyl acrylate (SA) as monomer, allyl sucrose ether (ASE) as crosslink agent and lauroyl peroxide (LPO) as initiator in the solvent of ethyl acetate. The powders were normal distribution in the range 1–80 μm and showed sensitive to pH in water. Before pH 7, both of the viscosity and the light transmittance of the APAT emulsion increased with enhancing pH value. ASE and SA played an important role in the properties of ASAT. When the amount of ASE was increased, the crosslink degree in the ASAT molecule increased. As the result, the viscosity of its emulsion increased firstly and then decreased, but the light transmittance of the emulsion decreased monotonously. Introduction of SA led to formation of an associative ASAT. Therefore, both of the viscosity and light transmittance of ASAT emulsion increased firstly and then decrease with increasing the amount of SA. Meanwhile, the associative ASAT emulsion showed shear thinning behavior, good salt tolerate, and less sensitivity to temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40512.     

基于MasterCAM的压克力手板数控加工方法研究

利用MasterCAM软件,对压克力材料的灯罩手板进行了数控加工的程序编制和数控仿真。特别就装夹和加工操作过程进行了具体的描述,为在数控机床上加工非金属材料提供了有价值的参考。     

Reactive magnetron sputtering of indium tin oxide films on acrylics—Electrical resistivity and optical properties

The effects of processing parameters on the deposition rate lattice parameters, stoichiometric compositions, surface morphology, and bonding state of indium tin oxide (ITO) films on acrylics had been previously reported. This study was a continuation of the previous investigation and focused on the electrical resistivity and optical properties of ITO films. The electrical resistivity decreased and then increased with oxygen flow rate. This was due to the effects of oxygen vacancies and impurity scattering. The resistivity of ITO films decreased with the applied bias voltage and film thickness. The transmittance of visible light increased with the oxygen flow rate and decreased with film thickness. Films deposited at oxygen flow rates having low electrical resistivity also had higher infrared radiation (IR) reflectance.     

Polymeric surface coatings for use as leather finishes—Part I. Studies on synthesis and characterisation of urethane acrylate oligomers

Synthesis and characterisation bynmr spectroscopy of oligomers derived from 2-hydroxy ethyl acrylate (hea) and 2-hydroxy propyl methacrylate (hpma) and 1,6-bexamethylene diisocyanate (hdi) are briefly discussed.     

Microscopic assessment of the effect of saw-texturedPinus radiata plywood surface on the distribution of a film-forming acrylic stain

The micro-morphology of the wood-coating interface of saw-texturedPinus radiata plywood panels, which had been coated with a film-forming stain, was examined using a range of microscopic techniques. The surface appearance and tissue deformation characteristics of saw-textured plywood and the pattern of distribution of the applied coating were observed by combined light, confocal, and scanning electron microscopy. The saw-textured surface was highly irregular, with surface tissues greatly distorted, being bent, twisted, and occasionally detached, and showing extensive cell wall cracking. The applied coating conformed closely to the contours of the saw-textured surface, resulting in a highly variable film thickness. The film was thickest in the grooves and thinnest over the ridges, and in places discontinuous, particularly where wood cells protruded out of the wood surface. These and other salient features of the surface of saw-textured plywood are discussed in relation to the pattern of the applied acrylic stain topcoat.     

多元共聚丙烯酸酯压敏胶乳液的开发研究

研究了一种多元共聚丙烯酸酯压敏胶乳液,按照半连续乳液聚合法聚合而成,并讨论了软硬单体、功能单体、乳化剂的选择对乳液性能的影响。通过改变预聚单体乳化液数量来调节乳液的粘度以满足不同的涂布工艺的需要。