Initial Tack Research Articles

Polyisoprene grafted white carbon black reinforced polyisobutylene‐based pressure‐sensitive adhesives: Comprehensive enhancement of adhesive performances

AbstractNowadays, inorganic fillers are widely used to enhance pressure‐sensitive adhesives (PSAs), but inorganic fillers have problems with poor compatibility and agglomeration. Furthermore, these types of PSAs usually have an antagonistic effect: as the shear performance improves, the initial tack decreases. This severely limits the application of PSAs. Herein, white carbon black (WCB) grafted with polyisoprene (PI) was prepared and used to enhance polyisobutylene‐based PSAs, and the optimal reaction conditions of grafting were explored. The shear and peel strength of PSAs all increase with the increase of the mass fraction of fillers. When the filler content is less than 10 wt%, the initial tack of PSAs increases. When the filler content exceeds 10 wt%, the initial viscosity of PSAs decreases, but it is still far higher than that of the unmodified WCB‐reinforced PSAs system. In addition, the rheological performances of PSAs were tested, further exploring the role of particle grafting in PSAs.Highlights PSAs reinforced with white carbon black grafted with polyisoprene were prepared. The optimal conditions for modified white carbon black have been determined. The grafting fillers have improved all the performance of PSAs. The grafting of fillers significantly reduces the antagonistic effect of PSAs. Rheology was used to explore the effect of filler grafting in the PSAs.

A Study Into the Hot Tack and Cooled Seal Performance of Emerging Coated Papers for Primary Flexible Food Packaging

ABSTRACTIn response to the need to employ recyclable materials for food packaging, the resurgence of paper as a primary flexible packaging material is driven by consumer trust in paper and its renewable wood fibre composition, strengthened by a well‐established recycling infrastructure. A diverse range of coated papers and coatings has become accessible in the market, specifically tailored for applications in horizontal and vertical form‐fill sealing. Within the framework of the CORNET‐TETRA project HBC.2021.0288 REPAC2, a careful selection of 16 food‐grade coated papers and/or coatings, slated for introduction to the market either presently or within the next 2 years, has been undertaken. This study focused on evaluating the processing window for superior hot tack and cooled seal performance of coated papers, in relation with the composition of paper coatings as identified using Fourier transform infrared (FTIR) measurements, and their thermal softening or melting characteristics as identified through differential scanning calorimetry (DSC). Thermal behaviour in DSC thermograms is used to categorize the commercial coated papers into distinct classes. Class I papers, mainly with acrylic‐based coatings, exhibit high hot tack strengths (0.2–0.7 N/mm) and a glass transition temperature (Tg) close to the seal initiation temperature but do not considerably gain strength with further cooling. Class II papers are thermally inert in DSC with minimal thermoplastics, leading to weak seals. In contrast, classes III and IV, including wax‐based and polyolefin‐based or polyvinylalcohol‐based (PVOH) coatings, respectively, show low initial hot tack strengths that considerably increase upon adequate cooling. Particularly, the Class IV papers with polyolefin‐based coatings have well‐performing seals. Despite having relatively low hot tack strengths after cool times of 0.1 s, below 0.3 N/mm, high strengths can be obtained after adequate cooling with outliers reaching 0.74 and 1.14 N/mm. Additionally, the influences of seal parameters on seal performance were evaluated. The study reveals that cool time, seal pressure and, to a lesser extent, seal time significantly impact hot tack strength, consistent with prior research. The critical role of jaw temperature in heat conductive sealing is affirmed, as it dictates the efficacy of other seal parameters. Seal initiation occurs at 75°C for four papers, and nine others necessitate temperatures equal to or exceeding 100°C, with one paper only displaying seal initiation at 195°C. This variation highlights the requisite for tailored temperature windows for effective sealing of these papers. As such, deeper insights into the intricate interplay between coating composition, thermal properties and seal performance are obtained in order to support advances in sustainable packaging technology.

Adhesive and rheological properties of Polyisobutylene-based adhesives with different white carbon black fillers

Different types of white carbon black (WCB) and polyisobutylene (PIB) were mixed to prepare WCB/PIB-based adhesives, whose adhesive and rheological properties were emphatically studied. The effects of different preparation methods, particle sizes, and different mass fractions of WCB on the performance of adhesives were systematically investigated. According to the results, large particles make the adhesive have better initial viscosity and peel strength at a low mass fraction, while small particles show excellent shear strength and peel strength at a high mass fraction. In addition, WCB was modified with KH570 to improve the dispersibility and compatibility of WCB in the matrix. When the amount of KH570 added was 5 wt% and 10 wt%, the two different adhesives had the best adhesive performance. The modification of WCB increased the shear performance of adhesives by 1–2 times and the initial tack by 1–2 grades.

S2841 Ileo-Rectal Anastomotic Defect Treated Twice With Endoscopic Tack Suture System and Stenting

Introduction: The endoscopic tack suture system is a novel technique that includes a through the scope (TTS) suture-based device that was recently designed for the closure of large and irregular defects in the gastrointestinal tract. Choice of closure device depends on the location, size, and working space around the defect. Over-the-scope clips (OTSC) and endoscopic suturing devices require withdrawal of the scope to load and are harder to maneuver through smaller spaces such as strictures. The TTS tack suturing system prevents the need to withdraw the scope and can be deployed in very small spaces. We present a case of a recurrent post-surgical leak leading to wound dehiscence and enterocutaneous fistula of an ileorectal anastomosis associated with a stenosis requiring the tack suture device and stenting for closure. Case Description/Methods: A 60-year-old woman was admitted after a recent subtotal colectomy with ileo-colonic anastomosis for a large adenoma that was unable to be resected endoscopically. She developed a pelvic abscess and wound dehiscence. She underwent exploratory laparoscopy with resection of the anastomosis with end-ileostomy creation. She later underwent open ileostomy reversal with ileo-rectal anastomosis and drain placement. Output continued from both the drain and the midline incision. Colonoscopy showed a large defect in the ileo-rectal anastomosis that was 40% circumferential with significant stenosis. The tack suturing system was employed after argon plasma coagulation (APC) and a fully covered esophageal stent was deployed across the defect (Figure A). During repeat colonoscopy, the initial tack and suturing device was found to be in place on the ileal mucosa, but two tacks had dislodged from the colonic mucosa. An improved small, well defined, round defect was found at the anastomosis (Figure B). The defect was again treated with APC, tack suturing, and stent placement with subsequent resolution of symptoms (Figure C). Discussion: This case highlights the novel tack suturing system which ultimately prevented this patient from undergoing further operations and requiring a colostomy. The tack suture system is an ideal tool for defect closure in tight spaces where OTSC or endoscopic suturing are too bulky. Mahmoud et al. conducted the first and only multi-center study describing the feasibility and safety of the endoscopic tack suturing device in the clinical setting and found successful closure of defects in approximately 90% of cases.Figure 1.: (A) Tack placement following APC at anastomotic defect. (B) Initial tack suture with 2 tacks dislodged from colonic mucosa and small improved defect in anastomosis. (C) Tack placement for closure of persistent defect.

High holding power of acrylic emulsion PSA with sorbitan nonionic surfactants and cross-linker

Since traditional nonyl phenyl type nonionic surfactants have been known as destructive to the ecosystem, sorbitan nonionic surfactants (Tween 20, 40, 60 and 80) were used to make acrylic emulsion type pressure sensitive adhesives (PSA), and the type of effects they have on the adhesive properties were investigated. Also, their adhesive properties were compared with those synthesized using traditional nonyl phenyl nonionic surfactant (NP 40). As a result, PSA made using Tween60 showed higher initial tack and peel strength and a much higher holding power than those properties made using NP 40 at room temperature. PSA made by Tween 60, and cross-linked by DGEBA (Bisphenol A diglycidyl ether) and phenyl aziridine, exhibited over 12 h of holding power at 150 °C, and showed a holding state up to 180 °C during a SAFT test (Shear Adhesion Failure Temperature).

Quantifying the kinetics and morphological changes of the fusion of spheroid building blocks

Tissue fusion, whereby two or more spheroids coalesce, is a process that is fundamental to biofabrication. We have designed a quantitative, high-throughput platform to investigate the fusion of multicellular spheroids using agarose micro-molds. Spheroids of primary human chondrocytes (HCH) or human breast cancer cells (MCF-7) were self-assembled for 24 h and then brought together to form an array comprised of two spheroids (one doublet) per well. To quantify spheroid fusogenicity, we developed two assays: (1) an initial tack assay, defined as the minimum amount of time for two spheroids to form a mechanically stable tissue complex or doublet, and (2) a fusion assay, in which we defined and tracked key morphological parameters of the doublets as a function of time using wide-field fluorescence microscopy over a 24 h time-lapse. The initial tack of spheroid fusion was measured by inverting the micro-molds and centrifuging doublets at various time points to assess their connectedness. We found that the initial tack between two spheroids forms rapidly, with the majority of doublets remaining intact after centrifugation following just 30 min of fusion. Over the course of 24 h of fusion, several morphological changes occurred, which were quantified using a custom image analysis pipeline. End-to-end doublet lengths decreased over time, doublet widths decreased for chondrocytes and increased for MCF-7, contact lengths increased over time, and chondrocyte doublets exhibited higher intersphere angles at the end of fusion. We also assessed fusion by measuring the fluorescence intensity at the plane of fusion, which increased over time for both cell types. Interestingly, we observed that doublets moved and rotated in the micro-wells during fusion and this rotation was inhibited by ROCK inhibitor Y-27632 and myosin II inhibitor blebbistatin. Understanding and optimizing tissue fusion is essential for creating larger tissues, organs, or other structures using individual microtissues as building parts.

Adsorption Property of Silicone Rubber Sticking Chuck for OLED Glass Substrate

Manufacturing process of OLED contains adsorption-desorption process of glass substrate. There are several adsorption methods of glass substrate such as atmospheric pressure, vacuum and electrostatic adsorption. However, these methods are very complex to connect system. Therefore, the adsorption method using silicone rubber based sticking chuck was proposed in this study. Three types of silicone rubbers having 0, 19.3 and 32.2 wt% of fluorine were used and their mechanical properties, surface energies and adsorption properties were examined. According to the results σ300 and hardness increased with increasing fluorine contents, but elongation was decreased. Also, fluorosilicone rubber containing 32.2 wt% of fluorine showed the lowest surface tension, among three types of rubber and resulted in the highest initial tack with glass substrate. After the adsorption-desorption test of 300,000 cycles was performed, the adsorption force of S-1 (silicone rubber) decreased largely from 2.34 to 0.73 MPa. However, the S-3 (fluorosilicone rubber having 32.2 wt%. of fluorine) decreased only from 3.15 to 2.24 MPa. From this study, we obtained the valuable equations related to long term durability of silicone based sticking chuck. Finally the transfer of silicone rubber to glass substrate with the adsorption-desorption process was not occurred and this phenomenon was examined by UV-Visible spectroscopy.

Synthesis and Properties of IPDI-TMP Waterborne Curing Agent

The waterborne curing agent was prepared by reaction of isophorone diisocyanate (IPDI), polyethylene glycol single methyl ether(MPEG) and trimethylol propane (TMP). The synthesis process of curing agent were monitored by Fourier transform infrared (FTIR) spectroscopy, and initial tack, peel strength, heat aging resistance, shear strength, creep resistance of all samples with different curing agent content were measured. The results showed that the curing agent dispersed well as an incorporated state in the waterborne polyurethane. The water and ethanol absorption decreased with increasing curing agent content, the peel strength was significantly increased up to 6.7 N/mm.

Mechanical constraint effect on residual stress and distortion in T-fillet welds by three-dimensional finite element analysis

Severe local heating and the mechanical constraints caused by the initial tack welding or clamping of parts to be arc-welded create undesirable residual stress or distortion in the parts. A three-dimensional model using a finite element method has been developed for the analysis of T-fillet welds with initially different tack-welded types. The temperature-dependent material properties, linear strain hardening, and Von-Mises yield criterion were applied in an uncoupled thermal and mechanical analyses, and the heat source of the weld has been modeled by a combination of volumetric and surface heat flux. The reliability of the modeling procedure has been verified with temperature, displacement, and residual stress measurements found in the literature and from experiments. The results show that the residual stresses and the extent of distortion are influenced by the type of constraint. The residual stress could be reduced but at the expense of enhanced distortion.

Effect of crosslinkers on adhesion properties of electron beam curable polyurethane pressure sensitive adhesive

Polyurethane (PU) based pressure-sensitive adhesive (PSA) using monofunctional urethane acrylate (MFUA) and difunctional urethane acrylate (DFUA) has been cured using electron beam (e-beam) irradiation. The effect of varying e-beam doses on the adhesion properties viz. peel adhesion, shear adhesion and initial tack of PSA has been studied. Effect of various crosslinkers viz. methylene diphenyl di-isocynate (MDI), isophorone di-isocynate (IPDI) and triallyl isocynurate (TAIC) on adhesion properties as well as on moisture vapor transmission rate (MVTR) and gel content of the PSA has also been studied. It was observed that with increasing dose and concentration of crosslinkers all the adhesion properties viz. peel adhesion, shear adhesion strength and initial tack were increased and reached a plateau, and then a decline was observed with further increasing of the dose and crosslinkers concentration. Similarly, MVTR decreased and the gel content increased with increasing dose of electron beam.

Effect of tackifier and crosslinkers on electron beam curable polyurethane pressure sensitive adhesive

Polyurethane based pressure sensitive adhesive using monofunctional urethane acrylate and difunctional urethane acrylate has been made using electron beam irradiation. The effect of varying electron beam doses on the adhesion properties viz., peel adhesion, shear adhesion and initial tack has been studied. Effect of tackifier and crosslinkers viz., polymeric methylene diphenyl diisocynate, carbodiimide modified methylene diphenyl diisocynate and triallyl cynurate on adhesion properties as well as on moisture vapor transmission rate and gel content of the polyurethane based pressure sensitive adhesive has also been studied. It was found that with increasing dose, tackifier and crosslinkers concentration, all the adhesion properties viz., peel adhesion, shear adhesion strength and initial tack were increased upto a certain dose, concentration of tackifier and crosslinkers, reached a plateau and then levelled off with further increasing the dose, tackifier and crosslinkers concentration. Similarly, moisture vapor transmission rate was decreased and the gel content increased with increasing dose of electron beam.

Development of a Starch Adhesive for Corrugated Board under Room Temperature

The use of starch as a renewable and biodegradable adhesive is becoming increasingly attractive because of the environmental concerns about the industrial wastes generated from petroleum products and the growing awareness of the potential deleterious consequences of greenhouse gas emissions from these activities. Starch adhesive is most extensively used in corrugated board industry because of the abundant supply, low cost, renewability, biodegradability, and ease of chemical modifications. Starch adhesive has great effect on the performance, production technology and manufacturing cost of the corrugated board. It is of great importance to develop starch adhesive with stable properties, high performance, good viscosity, fast curing speed to meet the market requirement. In this paper, oxidation of starch by sodium hypochlorite under aqueous alkaline conditions with the aid of the catalysis of nickel sulphate at room temperature was investigated. The effects of sodium hypochlorite loading and caustic soda dosage on the properties of the starch adhesive were examined. Optimization of starch oxidation is desirable to achieve the highest initial tack and bonding strength. The optimum synthesis condition was obtained. Under the optimum condition, Under the optimum condition, 98.7% of the initial tack and 11.4 N/25 mm of the bonding strength were obtained respectively.. The modified starch adhesive showed great potential for industrial application.

Adhesion Properties of Urea-Melamine-Formaldehyde (UMF) Resin with Different Molar Ratios in Bonding High and Low Moisture Content Veneers

ABSTRACT The objective of this research was executed to investigate the effect of molar ratio of formaldehyde to urea and melamine (F/(U+M)) of urea-melamine-formaldehyde (UMF) resin on bonding high and low moisture content veneers. For that purpose, UMF resin types with 5 different F/(U+M) molar ratios (1.45, 1.65, 1.85, 2.05, and 2.25) synthesized were used in present study. First, their curing behavior was eval-uated by differential scanning calorimetry. Second, their adhesion performance in bonding high and low moisture content veneers was evaluated by probe tack and dry and wet shear strength tests. Curing temper-ature and reaction enthalpy decreased with the increase of F/(U+M) molar ratio. And the dry and wet shear strengthsof plywood manufactured from low moisture content veneers were higher than thoseof plywood manufactured from high moisture content veneers. Also, the maximum initial tack force on the low mois-ture content veneer was higher than that on the high moisture content veneer. Keywords : urea-melamine-formaldehyde resin, adhesion performance, moisture content, veneer

Environment-friendly adhesives for surface bonding of wood-based flooring using natural tannin to reduce formaldehyde and TVOC emission

The objective of this research was to develop environment-friendly adhesives for face fancy veneer bonding of engineered flooring using the natural tannin form bark in the wood. The natural wattle tannin adhesive were used to replace UF resin in the formaldehyde-based resin system in order to reduce formaldehyde and volatile organic compound (VOC) emissions from the adhesives used between plywoods and fancy veneers. PVAc was added to the natural tannin adhesive to increase viscosity of tannin adhesive for surface bonding. For tannin/PVAc hybrid adhesives, 5%, 10%, 20% and 30% of PVAc to the natural tannin adhesives were added. tannin/PVAc hybrid adhesives showed better bonding than the commercial natural tannin adhesive with a higher level of wood penetration. The initial adhesion strength was sufficient to be maintained within the optimum initial tack range. The standard formaldehyde emission test (desiccator method), field and laboratory emission cell (FLEC) and VOC analyzer were used to determine the formaldehyde and VOC emissions from engineered flooring bonded with commercial the natural tannin adhesive and tannin/PVAc hybrid adhesives. By desiccator method and FLEC, the formaldehyde emission level of each adhesive showed the similar tendency. All adhesives satisfied the E1 grade (below 1.5mg/L) and E0 grade (below 0.5mg/L) with UV coating. VOC emission results by FLEC and VOC analyzer were different with the formaldehyde emission results. TVOC emission was slightly increased as adding PVAc.

Tensile properties and adhesion of water-absorbing hydrogels based on ternary poly(N-vinyl pyrrolidone)/poly(ethylene glycol)/poly(methacrylic acid-co-ethylacrylate) blends

Rubber-like elasticity and pressure-sensitive adhesion of ternary blends of high-molecularweight poly(N-vinyl pyrrolidone) (PVP) with oligomeric poly(ethylene glycol) (PEG) of molecular weight 400 g/mol and a co-polymer of methacrylic acid with ethylacrylate (PMAA-co-EA) is due to formation of a interpolymer hydrogen bonded complex. In the ternary blend, PVP is present in a greater amount and acts as a film-forming polymer (FFP). As each short chain of PEG bears two terminal hydroxyl groups, which are capable of forming hydrogen bonds with the carbonyl groups in PVP repeat units, PEG behaves as a reversible carcass-like cross-linker (CLC) between long PVP macromolecules. In addition, the PMAA-co-EA forms a ladder-like interpolymer complex with PVP via hydrogen bonding of carboxyl groups and serves as a ladder-like cross-linker (LLC) of PVP. Adhesion behavior, mechanical properties and water-absorbing capacity of PVP/PEG/PMAA-co-EA blends are functions of blend composition. The CLC (PEG) endows pressure-sensitive adhesion to PVP blends, acting simultaneously as PVP plasticizer, as well as enhancer of cohesive strength. While the PVP/PEG inter-polymer complex is soluble in water, the LLC (PMAA-co-EA) provides insolubility and swellability, increasing further the cohesive strength of the blend composition. At high LLC concentrations, the blends lose their initial tack but become tacky upon water uptake. In this way, ternary PVP/PEG/PMAA-co-EA blends combine tack, typical of conventional hydrophobic pressure-sensitive adhesives, with the capability to adhere to highly hydrated substrates, typical of bioadhesives.

Initial tack and viscoelastic properties of MF/PVAc hybrid resins used as adhesives for composite flooring materials

The initial tack and viscoelastic properties of blends of melamine–formaldehyde (MF) resin and poly(vinyl acetate) (PVAc) emulsion on decorative veneer and plywood surfaces were investigated using a texture analyzer and dynamic mechanical thermal analysis (DMTA) at room temperature with respect to the 'open time', the time delay between applying an adhesive to a surface and contacting that surface with the other material. We determined and compared the effects of PVAc content, at 0, 30, 50, 70 and 100 wt%, in blends with MF resin. As PVAc is curable at room temperature, PVAc markedly affected the initial tack, as well as DMTA results. The degree of 'tack' was determined quantitatively based on the probe tack data. As the adhesion in an engineered flooring should be achieved in 2–3 min, the acceptable tack range is between 100 and 200 g. From the DMTA results, i.e., the tan δ max values, the maximum loss modulus (E&Prime) and the rigidity (ΔE) of MF/PVAc blends at room temperature, it was found that tan δ and loss modulus (E&Prime) increased with increasing MF resin content. Moreover, the rigidities of the 70:30 and 50:50 MF/PVAc blends were higher than those of the other blends, especially in comparison with the pure 100% PVAc and 100% MF. We conclude that the initial tack correlates with the MF/PVAc blend ratio during the adhesion process at room temperature.