Water‐soluble/dispersible cationic pressure‐sensitive adhesives. II. Adhesives from emulsion polymerization

In our previous work, we reported that cationic water‐soluble pressure‐sensitive adhesives (PSAs) could be synthesized in ethanol or methanol. These cationic water‐soluble adhesives would not cause a stickies problem during paper recycling and can be easily removed from the papermaking system by adsorbing on wood fibers. In this study we report the synthesis and application of water‐based cationic PSAs using miniemulsion polymerization. A redox initiator system of cumene hydroperoxide/tetraethylenepentamine was used to force interfacial polymerization. The end‐use properties of the PSAs were evaluated, and the repulpability of the PSAs in paper recycling was studied. It was found that the cationic PSA from miniemulsion polymerization itself was insoluble and nondispersible in water during the paper recycling process. However, if this water‐insoluble cationic PSA from miniemulsion was formulated with a water‐soluble cationic PSA made from ethanol, the solubility or dispensability of the former PSA in water was improved. The molecular weight and degree of crosslinking of the PSA polymer have significant effects on the properties and dispersability of PSA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 347–353, 2004     

Acrylic pressure‐sensitive adhesives with nanodiamonds and acid–base dependence of the pressure‐sensitive adhesive properties

A high performance and functional properties in pressure‐sensitive adhesives (PSAs) are attractive in fundamental and industrial fields. To control the performance of PSAs, nanofillers have been loaded into them. In this study, we focused on composites of acrylic PSAs and nanodiamonds (NDs). The loaded NDs reinforced the mechanical properties and increased the performance of the PSAs. NDs in a PSA formed a network structure. In this study, we revealed that the acidic–basic state was a key factor in the control of the dispersion of the NDs. When a PSA emulsions and ND aqueous dispersion was mixed under basic conditions, the composites demonstrated higher PSA properties (tack, holding, and peeling strength). We investigated the effect of the ND loading on the PSA properties from the viewpoints of the nanostructure and acid–base interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46349.     

A new and simple way of preparing polycation‐grafted fibrous cellulose

A new way of producing polycation‐grafted fibrous cellulose for its use as a retention aid in the papermaking process was conceived. It consists of adding, under intense stirring, to a cellulose fibers suspension at a basic pH a cationic polyacrylamide dissolved in water. As the cellulose fiber's surface is negatively charged because of its more or less acid groups, the cationic polymer adsorbs on it. The cationic‐grafted cellulose fibers are very similar to the cellulose fibers used in papermaking, since the polymer is (on a micrometer scale) homogeneously grafted on them as a film. It could so be used to increase the retention of the negatively charged fillers, fibers, and pigments during the process, without altering the properties of the resulting sheet of paper. The amount of polymeric grafts depends on the quantity of anionic groups on fiber's surface and varies monotonically with the grafting temperature and polyacrylamide's concentration in the blend. The grafted fibrous cellulose is well stable, even in drastic media and for lower M_w grafts, and the amount of grafted polymer also depends on the concentration and characteristics of fiber's suspension. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3149–3157, 2006     

PSA performances and viscoelastic properties of SIS‐based PSA blends with H‐DCPD tackifiers

Hotmelt pressure sensitive adhesives (PSAs) usually contain styrenic block copolymers like styrene–isoprene–styrene (SIS), SBS, SEBS, tackifier, oil, and additives. These block copolymers individually reveal no tack. Therefore, a tackifier is a low molecular weight material with high glass transition temperature (T_g), and imparts the tacky property to PSA. The SIS block copolymer with different diblocks was blended with hydrogenated dicyclopentadiene (H‐DCPD tackifier), which has three kinds of T_g. PSA performance was evaluated by probe tack, peel strength, and shear adhesion failure temperature. PSA is a viscoelastic material, so that its performance is significantly related to the viscoelastic properties of PSAs. We tested the viscoelastic properties by dynamic mechanical analysis and the thermal properties by differential scanning calorimeter to investigate the relation between viscoelastic properties and PSA performance. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 2839–2846, 2006     

Preparation and characterization of all para‐position polysulfonamide fiber

Poly(4,4′‐diphenylsulfone terephthalamide) referred to as all para‐position polysulfonamide (all para‐position PSA) is a special kind of PSAs, copolymer s of 3,3′‐diaminodiphenylsulfone, 4,4′‐diaminodiphenylsulfone, and terephthaloyl chloride. However, with the increasing para‐structure content in the PSAs, the PSA shows very poor solubility in common amide‐type polar aprotic solvents and cannot be used for wet spinning. In this article, it was found that all para‐position PSA can be easily dissolved in N,N‐Dimethylacetamide (DMAc)/LiCl system, and then the all para‐position PSA fiber was prepared for the first time by wet spinning. The properties of all para‐position PSA pulps and fibers were investigated via Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy, thermal gravimetric analysis, dynamical mechanical analysis, X‐ray diffraction (XRD), and tensile strength testing. The tensile strength, elongation at break, and crystallinity of the resulting fiber were 4.4 cN/dtex, 15.9%, and 33.53%, respectively. The results indicated that all para‐position PSA fiber was a high‐temperature resistance fiber with better mechanical properties than common PSA fiber. The improved tensile strength of the fiber will expand its applications and may take place of Nomex in certain fields and become a new generation of flame retardant and high‐temperature resistant material. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Control of structure and tack properties of acrylic pressure‐sensitive adhesives designed by a polymerization process

Free radical emulsion polymerization of methyl methacrylate (MMA) and 2‐ethylhexyl acrylate (EHA) results in the synthesis of pressure‐sensitive adhesives (PSAs) with good tack properties. Management of both the copolymer composition and the polymerization process allows one to control the behavior of the PSA. Semicontinuous (SC) processes create polymer particles whose instantaneous composition is close to that of the feed particle The SC Mixture process (continuous feeding with comonomer blends) affords nearly homogeneous latex particles and PSA films. The SC Gradient process (separate feedings at inversely varying rates) affords heterogeneous particles and films. The Batch process leads to somewhat heterogeneous films, but the hard (MMA‐rich) microdomains are made compatible with their soft (EHA‐rich) matrix because of the assumed formation of tapered‐type copolymers. Tack measurements indicate the importance of the particle and film structures. Too much hardness or softness leads to unacceptable lacks of adhesion and cohesion, respectively. Homogeneous structures prove adequate, but their tack properties collapse with rising temperature. Heterogeneous structures, with extensive phase segregation, prove unsatisfactory because they lack adhesion and cohesion. Finally, the association of well‐balanced composition and compatible heterogeneity is the criterion for suitable PSA behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2749–2756, 2003     

The effect of borax‐modified starch on wheat straw‐based paper properties

This study was focused on the improvement of mechanical strength properties of wheat straw‐based paper through modification of wet‐end cationic starch with borax. Borax has been used extensively in many industrial applications for its unique physical and chemical properties. We investigated the strengthening effect of borax‐modified starch (BMS) as wet‐end paper strength additive on the mechanical strength properties especially the tensile strength of wheat straw‐based paper. Hand‐sheets made of typical wheat straw‐based papermaking furnish were investigated. Experimental results showed that BMS substantially increased the strength properties. Tensile index, elongation, tensile energy absorption, and wet tensile index were increased by 17%, 23%, 20%, and 21%, respectively. A short mill trial was also conducted on papermaking machine in which the impact of BMS on wheat straw‐based low grammage paper (<90 gsm) was investigated. The objective of mill trial was to reduce costly virgin softwood pulp content in wheat straw‐based paper recipe. Mill trial results showed similar trends in strength properties as in case of laboratory studies. Virgin softwood pulp was reduced from 30% to 25% in papermaking furnish. Furthermore, no sheet breaks were reported during trial which often happened due to poor strength of paper web. This study strongly suggests that modification of wet‐end cationic starch with borax holds a tremendous potential as wet‐end strength additive. It can provide significantly improved strength properties, reduction in softwood pulp costs, and better papermaking machine performance. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Crosslinking of pressure sensitive adhesive based on water‐borne acrylate

This publication shows how the kind of crosslinking agents and their contents influence important properties of acrylic based pressure‐sensitive adhesive (PSA) dispersions such as tack, adhesion and cohesion. Synthesized PSAs based on acrylic polymers, containing 2‐ethylhexyl acrylate, butyl acrylate, vinyl acetate, styrene and acrylic acid are used in the preparation of self‐adhesive dispersions used as coating of polyethylene foams and poly(vinyl chloride) and polyester foils. © 2003 Society of Chemical Industry     

Crosslinked acrylic pressure‐sensitive adhesives. I. Effect of the crosslinking reaction on the peel strength

For pressure‐sensitive adhesives (PSAs) composed of poly(co‐ethyl acrylate‐2‐ethylhexyl acrylate‐2‐hydroxyethyl methacrylate) as a base resin and polyisocyanate as a crosslinker, the relationship between the crosslinking reaction and peel strength was investigated. A 90° peel test of cured PSA films under various storage conditions was carried out. At the same time, the isocyanate (NCO) consumption in these PSA films was monitored by attenuated total reflectance/Fourier transform infrared spectroscopy. The peel strength of the PSA compounded with the crosslinker decreased as the NCO groups were consumed. The elevation of the aging temperature promoted the crosslinking reaction and increased the decrement in the peel strength. The peel strength of noncrosslinked and crosslinked PSA films increased with the contact time. A high storage temperature made the increment in the peel strength increase. The addition of the crosslinker to the PSA films reduced the increment in the peel strength. Furthermore, PSA films with residual NCO groups possessed stronger peel strengths than fully cured films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1493–1499, 2003     

Melt versus solvent coating: Structure and properties of block–copolymer‐based pressure‐sensitive adhesives

Pressure‐sensitive adhesives (PSAs) composed of a styrene–isoprene–styrene triblock copolymer and a midblock‐associating resin were prepared via solvent and hot‐melt coating. The formulations and thermal histories up to the point of coating were identical, yet significant differences in the properties were observed as a function of the coating method. The solvent‐coated PSA showed superior shear holding power, and the hot‐melt‐coated PSA performed better in tack and peel tests. Two factors resulting from the processing conditions were responsible for these property differences. The quick cooling process occurring after hot‐melt coating led to a poorly defined microstructure and, therefore, less physical crosslinking. Rheological data for melt‐pressed and solvent‐cast PSA films confirmed these microstructural differences. The increased solubility of the tackifier in the solvent additionally created a composition gradient in the solvent coating. Annealing improved the long‐range order of both hot‐melt and solvent coatings, producing a body‐centered cubic microstructure identified by small‐angle X‐ray scattering. This microstructure improved the shear strength of both types of adhesive coatings, whereas the peel and tack properties of the solvent coatings remained inferior to those of the hot‐melt coatings because of differences in the surface compositions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3355–3367, 2002     

Molecular design for silane‐terminated polyurethane applied to moisture‐curable pressure‐sensitive adhesive

Moisture‐curable silane‐terminated polyurethanes (SPUs) served as pressure‐sensitive adhesive (PSA) were synthesized based on different soft‐segment materials, silanes and silane end‐capping ratios. Depending on peel strength, tack, and holding power, the characteristic properties for PSA, a proper scheme for the design of the PSA molecular structure could be selected. Completely end‐capped by silane and assembled by poly(propylene glycol), SPU films presented better properties. On the basis of comprehensive considerations, the anilinomethyltriethoxysilane was an excellent silane‐end capper for PSA. Otherwise, the obtained PSAs did not degrade below 250 °C. The glass transition temperature and hydrophobicity of SPU samples with different formulas were also investigated. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45292.     

Sustainable isosorbide‐based transparent pressure‐sensitive adhesives for optically clear adhesive and their adhesion performance

A biomass‐based isosorbide acrylate (ISA) was synthesized in a one‐pot reaction at low temperature with a quite slow dropwise technique using a syringe pump. Using the ISA monomer, UV‐cured transparent acrylic pressure‐sensitive adhesives (PSAs) composed of semi‐interpenetrating networks were prepared. The effect of ISA on the adhesion performance of the resulting acrylic PSAs was investigated by changing the ISA content, while fixing the mole ratio between 2‐ethylhexyl acrylate and 2‐hydroxyethyl acrylate in the PSAs. The prepared acrylic PSAs, with ISA content ranging from 3.2 to 14.3 mol%, were evaluated in terms of 180° peel strength, probe tack, static shear testing and optical properties. Increasing the ISA content in the acrylic PSAs improved the adhesion properties, such as 180° peel strength (0.25–0.32 N/25 mm), shear holding power (0.086–0.023 mm) and probe tack (1.21–2.26 N). Dynamic mechanical analysis indicated that ISA is a good candidate monomer, playing the role of adhesion promoter and hard monomer in the acrylic PSAs. © 2017 Society of Chemical Industry     

Rheological and adhesion properties of acrylic pressure‐sensitive adhesives

Different pressure‐sensitive adhesives (PSAs) based on acrylic monomers were synthesized under different reaction conditions. The synthesized PSAs have good adhesive properties and without leaving any residue can be easily peeled off from the surface of a substrate. The relationship between PSAs rheological behavior and its adhesion properties (e.g., peel, tack, and shear resistance) has been studied at constant adhesive thickness. The samples were examined for their surface energy and viscoelastic characteristics. It was observed that increase in reaction temperature and reaction time results in decreased storage modulus due to lowered molecular weight, which finally leads to lower elasticity of the PSA. While the storage (G′) and loss (G″) modulus of samples increase with increased initiator concentration, the elasticity of PSA is increased as well. High G″ at high frequency (100 Hz) represents high peel strength because of higher dissipation of viscoelastic energy during debonding. The tack values increase by lowering storage modulus at 1 Hz due to higher M_e. Shear values are increased by higher storage modulus at low frequency (0.1 Hz) due to hydrogen bonding of the different components. Some parallel investigations on the surface energy of the samples showed that they have different properties because of the nature of different monomeric units with their corresponding orientations. Our results reveal that the peel strength is not affected by surface energy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Evaluation of disposable diaper construction hot melt pressure‐sensitive adhesives using blends of olefinic block copolymer and amorphous polyolefin polymers—Adhesive performance,sprayability, and viscoelastic characteristics

Pressure‐sensitive adhesives (PSAs) used in disposable diaper construction have been formulated using blends of olefinic block copolymer (OBC) and an ethylene–propylene (PE‐PP) amorphous polyolefin (APO) polymer, with three different unsaturated hydrocarbon resins (with varying aromatic content), and also with two different saturated aliphatic hydrocarbon resin (with varying cycloaliphaticity). The viscoelastic properties of theses PSA formulations were studied using dynamic mechanical analysis (DMA). Viscosity profiles at five different temperatures were generated to better understand the application window for the resulting adhesive formulation. Rheology master curves were generated using time–temperature–superposition analysis and correlated with the processability characteristics. Adhesives used in disposable diaper construction were applied between a polyethylene backing and a nonwoven substrate with an air‐assisted spiral spray application technique on an Acumeter Spray Coater. After the adhesive was applied, peel adhesion testing on the samples was performed. It has been observed that the OBC/PE–PP‐based disposable diaper construction PSA has a lower application temperature along with wider tolerance for hydrocarbon resin chemistries, especially for the saturated aliphatic resin‐based PSA formulations. Based on the coating parameters used, it has been learned that the adhesive formulations seem to show a higher shear rate at the nozzle, but Reynolds number calculated indicated no major turbulence occurring at the nozzle during spraying. Very good spray patterns were obtained for the olefinic polymer‐based PSA formulations. Disposable diaper construction article showed good adhesive peel properties, especially for the adhesive formulations containing saturated aliphatic hydrocarbon resin, which were comparable to the SBS‐based control. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3311–3318, 2013     

Recent synthetic approaches and emerging bio‐inspired strategies for the development of sustainable pressure‐sensitive adhesives derived from renewable building blocks

In this review, we provide a bird's eye view of recent developments in the field of pressure‐sensitive adhesives (PSAs) derived from renewable monomeric building blocks. This emerging research field has been driven by increasing sustainability requirements in the adhesive industry and bridges the gap existing between highly optimized petroleum‐based synthetic PSA systems, which display superior performance but lack biobased content, and historical PSAs derived from naturally occurring biopolymers (e.g., starch and natural rubber), which provide more environmentally friendly bonding solutions but have inherent technical limitations that prevent their more widespread implementation in today's technically demanding applications. We critically reviewed a representative (and exhaustive) survey of recent synthetic approaches to the development of biobased PSAs from the academic (articles) and industrial (patents) literature categorized in two families: chain‐growth and step‐growth polymerization routes. Finally, we draw a parallel between renewable synthetic PSAs and nature's self‐adhesive glues, highlighting how the synergy between green chemistry and biomimetic concepts could inspire the emergence of a new generation of smart, synthetic, biobased PSAs with differentiated properties that approach the ones that are found in the natural world and with a wide spectrum of potential applications in the industrial and medical sectors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40669.     

Improvement in wettability of pressure‐sensitive adhesive on silicon wafer using crosslinking agent with siloxane groups

Acrylic copolymers are prepared by radical polymerization of 2‐ethylhexyl acrylate, ethyl acrylate, and acrylic acid followed by crosslinking to manufacture the pressure‐sensitive adhesives (PSAs) for silicon wafer protection. Both higher reliability and wettability are required for the protective acrylic PSAs in the semiconductor processing applications. The siloxane linkages are introduced in the acrylic PSAs via crosslinking with siloxane‐containing crosslinking agent to modify the thermal and wetting properties of PSAs efficiently. The more efficient formation of crosslinked network structure was achieved with higher content of tetra‐functional crosslinking agent, and the surface energy of PSAs decreased significantly with increasing the content of siloxane linkage resulting in the improved areal wetting rate. The thermal stability of PSAs was also improved significantly by incorporation of siloxane linkages. The adhesion properties such as peel strength and probe tack of acrylic PSAs decreased significantly by increasing the content of either crosslinking agent or siloxane linkage. The acrylic PSA with siloxane group showed both satisfactory wetting and clean debonding properties for the optimal protection of thin silicon wafers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

UV curable pressure‐sensitive adhesives for fabricating semiconductors. I. Development of easily peelable dicing tapes

In order to develop easily peelable dicing tapes from diced wafers, UV curing of various pressure‐sensitive adhesives (PSAs) was studied. After UV irradiation, the adhesive strength of a PSA composition including a diacrylourethane oligomer (UDA) decreased drastically compared with other compositions. Because of network formation via UV irradiation, this composition had a greater volume contraction that might yield microvoids at the interface between the adhesive and the wafer, resulting in the loose adhesion. Its storage modulus increased up to about 1000 times that before UV curing, which was due to the crosslinking of the UDA component. It was suggested that the increased crosslinking density and the high internal coagulant energy of the UDA backbone structure caused a remarkable decrease of the adhesive strength. Furthermore, it was ascertained that the UV‐irradiated UDA adhesives left few residual deposits on the wafer released from the tape. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 436–441, 2003     

Polymer‐Cationic Surfactant Interaction: 1. Surface and Physicochemical Properties of Polyvinyl Alcohol (PVA)‐S‐Alkyl Isothiouronium Bromide Surfactant Mixed Systems

Surface properties of polyvinyl alcohol (nonionic polymer) and three synthesized cationic surfactants, namely, S‐alkyl isothiouronium bromide at different mole fractions of 1:9, 3:7, 5:5, 7:3, and 9:1, were investigated. The values of the surface parameters were discussed according to the type of interaction between the cationic surfactant and type of polymer studied. The S‐alkyl isothiouronium bromide surfactant molecules are positively charged molecules, and the PVA chains contain hydroxyl groups that are partially negatively charged centers. The comparison between the surface properties of the individual cationic surfactants and their mixture with PVA polymer showed that the mixed systems have some advantages over the individual cationic surfactants.     

Preparation and performance of a transparent poly(3,4‐ethylene dioxythiophene)–poly(p‐styrene sulfonate‐co‐acrylic acid sodium) film with a high stability and water resistance

Poly(p‐styrene sulfonate‐co‐acrylic acid sodium) (PSA) from the copolymerization of acrylic acid sodium and p‐styrene sulfonate monomers were used to dope poly(3,4‐ethylene dioxythiophene) (PEDOT) to generate PEDOT–PSA antistatic dispersions. Compared to those of the PEDOT–poly(p‐styrene sulfonate sodium) (PSS), the physical and electrical properties of the PEDOT–PSA conductive liquids were much better. The PEDOT–PSA films possessed a better water resistance without a decrease in the conductivity. The sheet resistance of the PEDOT–PSA–poly(ethylene terephthalate) (PET) films was about 1.5 × 10⁴ Ω/sq with a 100 nm thickness, the same as the PEDOT–PSS–PET films. The transmittance of the PEDOT–PSA–PET films exceeded 88%. Furthermore, the environmental dispersity of the PEDOT–PSA antistatic dispersion was apparently improved by the dopant PSA so that the stability was extraordinarily promoted. Meanwhile, the water resistances of the PEDOT–PSA–PET and PEDOT–PSA films were also enhanced. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45163.     

Viscoelastic and adhesive properties of single‐component thermo‐resistant acrylic pressure sensitive adhesives

Poly(butyl acrylate‐vinyl acetate‐acrylic acid) based acrylic pressure sensitive adhesives (PSAs) were synthesized by solution polymerization for the fabrication of high performance pressure sensitive adhesive tapes. The synthesized PSAs have high shear strength and can be peeled off substrate without residues on the substrate at temperature up to 150°C. The PSAs synthesized in the present work are single‐component crosslinked and they can be used directly once synthesized, which is convenient for real applications compared to commercial multi‐component adhesives. The results demonstrated that the viscosity of the PSAs remained stable during prolonged storage. The effects of the preparation conditions such as initiator concentration, cross‐linker amount, organosiloxane monomer amount and tackifier resin on the polymer properties, such as glass transition temperature (T_g), molecular weight (M_w), surface energy and shear modulus, were studied, and the dependence of the adhesive properties on the polymer properties were also investigated. Crosslinking reactions showed a great improvement in the shear strength at high temperature. The addition of tackifier resin made peel strength increase compared to original PSAs because of the improvement of the adhesion strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40086.