Polyester polyurethane elastomer adhesives were prepared from hydroxyl liquid natural rubber and modified poly(ethylene terephthalate) with polymeric MDI. The starting materials and PU adducts were ...characterized by FT-IR in transition and ATR modes. The effect of the amount of hydroxyl groups on modified rubber, types of modified PET, and NCO/OH ratios were studied by wood-to-wood adhesion shear strength. The chemical resistance and green strength of PU adhesives were also analyzed by lab shear test. It was found that the synthesized carboxyl terminated PET and modified rubber contained 50% hydroxyl content with polymeric MDI in optimized NCO/OH molar ratio (0.45:0.55:0.75 by mole) presented the highest wood adhesive shear strength and chemical resistance, and present 83% of its maximum strength within only 12h.
To determine the adhesion strength (measured as shear bond strength, SBS) of orthodontic brackets using two experimental silane-based primer systems and compare and contrast their effect.
Sixty ...acid-etched premolars were randomly assigned into 4 study groups (n=15). In group 1, brackets were bonded without primer but using Transbond XT adhesive; in group 2, Transbond XT primer was applied and bracket bonded; in group 3, an experimental silane-based primer of 1.0vol% of 3-acryloxypropyltrimethoxysilane (ACPS) was applied before bonding; in group 4, an experimental silane-based primer of 1.0vol% of ACPS+0.5% bis-1, 2-(triethoxysilyl) ethane (BTSE) was used. The adhesion strength (measured as shear bond strength) was recorded using a universal testing machine. Failure types were classified according to the Adhesive Remnant Index (ARI). Contact angles of the primers were measured on an enamel slab.
Data was analyzed by ANOVA and Tukey's multiple comparison post hoc analysis.
The mean adhesion strength results were high in group 4: 15.8±1.6MPa followed by group 3: 12.5±1.5MPa, group 2: 11.9±1.1MPa and the lowest in group 1: 08.1±0.7MPa. A significant difference in adhesion strength was observed between all the groups except for group 3 and group 4 (p<0.01).
The ARI score was distributed largely to 0 and 1. One instance of enamel fractures was recorded in group 1. The contact angle measurements suggested that the lowest value with the experimental primer containing (ACPS+BTSE) was, <5° followed by Transbond XT, 41.86±4.56°.
The experimental silane primer systems were hydrophilic in nature and demonstrated higher adhesion strength compared to traditional orthodontic primers.
This report presented a new generation of UV-crosslinking solvent-based pressure-sensitive adhesive (PSA) based on photoinitiator-grafted polystyrene-block-polybutadiene-block-polystyrene (SBS). The ...SBS, onto which the 4-maleimidobenzophenone (4-MBP) as photoinitiator was grafted, was used as the main component of a PSA. After the UV-crosslinking, a crosslinked structure was formed between polymer chains. FTIR showed that the photoinitiator monomer was successfully grafted onto the hydrophobic polymer. The grafting ratio could be facilely controlled by adjusting the feed amounts of the BPO initiators. The tests of adhesion properties indicated that the 180° peel strength, shear persistent adhesivity and tack property were in the useful range for biomedical applications.
One of the main problems in thin film transistor liquid crystal displays (TFT-LCD) is a phenomenon called “light leakage”, seriously affecting black–white contrast and color brightness. It occurs due ...to a thermal shrinkage of the polarizing film in TFT-LCDs, caused by a heat from the backlight unit. A pressure-sensitive adhesive (PSA) used for assembling of the polarizing film to the TFT-LCD panel can relieve the stress and minimize the light leakage. PSAs are designed specifically for a certain size LCDs, and cannot be used for another size LCD because of poorer light leakage. Obviously, there is a certain necessity to develop a universal PSA applicable simultaneously for LCDs with different sizes, such as mobile phones, digital cameras, navigation systems, computer monitors, HDTVs, etc.
In this paper, we introduced N-vinyl pyrrolidone as a comonomer to a conventional copolymer of butyl acrylate, acrylic acid, and 2-hydroxy ethyl methacrylate. It resulted in a higher elasticity modulus and a higher shrinkage resistance of the PSA. A significant reduction of the light leakage to some extend was observed at increase of the hardener content for 2.5 and 7
in samples. However, it was accompanied by deterioration of the peel strength below spec requirements. Lowering molecular weight of the polymers from 626,000 to 205,000
Da resulted in excellent light leakage of both small and large specimens. Dynamic mechanical analysis confirmed that zero light leakage was achieved through a synergy of two mechanisms: high modulus, i.e. resistance to thermo-induced shrinkage, and high stress relaxation of lower molecular weight polymers. The results of this work are perspective for creation of a universal PSA for polarizing film in TFT-LCDs of different sizes.
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.
Polymeric methylenebis(phenylisocyanate) resins prepared with
15N and
13C labeled functional groups allow the detection of urethane linkages to wood using solid-state NMR. Resins prepared with only
...15N do not reveal urethane formation because of urea and urethane nitrogen signal overlap. Likewise, resins having only
13C suffer from overlapping carbonyl signals. However, in the case of the doubly labeled isocyanate group,
15N causes narrowing that seems to provide partial resolution of the urethane and urea carbonyl carbons. Furthermore, the double label gives complimentary nitrogen and carbon spectra which are required for a complete interpretation. This method will be useful for the characterization of the adhesive mechanism in wood-based composites bonded with isocyanate resins.
The RC99 committee of the Japan Society for Mechanical Engineers conducted the benchmark tests on strengths of adhesive joints using different testing methods. The effects of joint configuration, ...loading mode, adherend yield strength and so on, on the strength and data scatter were investigated using two typical epoxy adhesives. The strengths obtained by various tests were compared with each other. The relationships among strengths of butt, single lap and double lap joints and fracture toughness were given. Thirteen member institutes of the committee participated in this project. The benchmark results allow us to recognize that the joint strengths are strongly affected by the curing process. The key to obtaining the appropriate joint strength, is precise temperature control inside the adhesive layer for curing. Toughened adhesives do not always give higher joint strengths than untoughened adhesives. The yield strength of adherends much affects the observed lap joint strength of adhesives.
Several techniques have been applied to the surface of polypropylene (PP) film to improve its adhesion properties: grafting of poly(acrylic acid) by peroxidation after either irradiation by γ-rays or ...activation by argon plasma, acrylic acid plasma polymerization and nitrogen plasma. A first evaluation of their efficiency was made by measuring the adhesion energy of a two-layer complex containing the modified PP film and an acrylic adhesive tape. Grafting of poly(acrylic acid) either by pre-irradiation or by argon plasma treatment did not give a satisfactory improvement of the adhesion. On the contrary, nitrogen as well as acrylic acid plasmas induced a peeling energy that was up to 10 times higher than the value obtained for an untreated PP film towards the acrylic adhesive tape. The adhesion of PP films was also tested on bilayer laminates with (a) an extrusion-oxidized polyethylene film and (b) a terpolymer film of ethylene, acrylic acid and acrylate. Good adhesion was achieved between nitrogen-plasma-treated PP film and the oxidized polyethylene film (600 J m
−2) as well as the terpolymer film (427 J m
−2). However, the poly(acrylic acid) plasma-deposited layer induced an improvement of the adhesion only with the preoxidized polyethylene film (390 J m
−2).
