Pressure sensitive adhesives with post-crosslinking ability based on acrylic dispersions obtained from solvent-borne copolymers

This work presents a novel aqueous dispersion prepared from a solvent-borne acrylic copolymer mixture containing carboxylic acid groups for the first copolymer and epoxy groups for the second copolymer. The aim of this work was to test the suitability of the presented dispersion for the preparation of pressure sensitive adhesives (PSA) with post-crosslinking ability. A monomodal particle size distribution was obtained and a successful coemulsification of both copolymers into one particle was proved, although the epoxy containing polymer did not bear carboxylic acid groups. Storage of the dispersion led to intraparticular crosslinking inside the particles, which produced an increase in the shear of the PSA. Post-crosslinking ability was shown for the PSA of the unaged and aged dispersions in the presence of 1-methylimidazole and led to a major increase in shear but did not lead to a considerable decrease in peel. Probe-tack enabled a fast detection of post-crosslinking because of the appearance of a plateau formation in probe-tack curves. The adhesive properties before and after crosslinking demonstrate the potential of the presented dispersion, which yields novel PSA for applications which need high shear but also sufficient peel.     

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.     

Pressure Sensitive Adhesives Based on Oleic Acid

Existing pressure sensitive adhesives (PSA) are mostly based on petrochemical‐based polymers. This study reveals a new class of bio‐based polymers that can be used as PSA. The polymers are hydroxyl‐containing polyesters from the step‐growth polymerization of epoxidized oleic acid (EOA), an AB‐type monomer containing both a carboxylic acid group (A) and an epoxy group (B). The monomer is derived from epoxidation of renewable methyl oleate followed by selective hydrolysis of the ester group. The polymers (PEOA) of EOA were characterized for their chemical structure and molecular weight. The PEOA after being cured with a very small amount of a crosslinking agent could serve as a PSA with high peel strength, high tack force, superior shear resistance, excellent aging resistance, and excellent thermal stability. The PSA contains 99 wt% of green renewable materials. The PSA were also characterized for their viscoelastic properties and thermal properties.     

Influence of selected photoinitiators on important properties of photoreactive acrylic pressure‐sensitive adhesives

Photoreactive solvent‐borne pressure‐sensitive adhesives are not commercially available in the market. The reason for it is that the UV‐initiated crosslinking has sense only in the case of solvent‐free self‐adhesive systems. Investigations conducted in Institute of Chemical Organic Technology have shown that the photoreactive solvent‐borne acrylic PSA are conventional crosslinked solvent‐borne acrylic PSA used as crosslinking agents typical metal chelates as titanium acetylacetonate (TiACA), aluminum acetylacetonate (AlACA) or thermal reactive crosslinker melamine‐formaldehyde resin Cymel 303 clear considered. The main purpose of the investigation was to study the influence of diverse photoinitiators on main properties, such as shrinkage, tack, peel adhesion, and shear strength of solvent‐based acrylic pressure‐sensitive adhesives. The interesting alternative to conventional photoinitiators is unsaturated photoinitiators described in this article. Following unsaturated photoinitiators were used: 4‐acryloyloxy benzophenone, 4‐acryloyloxyethoxy benzophenone, and 4‐acryloyloxybutoxy benzophenone. The influence of the crosslinking agents or crosslinking methods was determined in relation to the reaction time and to the concentration versus adhesion properties. The increase of photoinitiator concentration causes in the decrease of the shrinkage. Increasing the UV dose during the crosslinking of acrylic PSA film leads clearly to better shrinkage resistance. The best results of the lowest shrinkage value of 0.35% were given by using 4‐acryloyloxy benzophenone. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

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     

Reactive blending approach to modify spin‐coated epoxy film: Part I. Synthesis and characterization of star‐shaped poly(ϵ‐caprolactone)

To effectively modify the properties of an epoxy, branched oligomers were synthesized from ?‐caprolactone (CL) and end‐functionalized to realize network precursors that can be reactively blended with the epoxy. The ring‐opening polymerization (ROP) of the CL in the presence of polyglycerol (PGL) initiator (3.9 and 9.1 mol %) and Sn(II) 2‐ethylhexanoate catalyst yielded oligomers with hydroxyl end‐groups, which were converted to carboxylic acid functionality by reaction with succinic anhydride. The functionalized oligomers had a four‐armed structure and the molecular weight of the oligomers could be controlled by the ratio of CL to PGL in the feed. To achieve an adequately crosslinked network in the reactive blending, a dual‐catalyzed reaction scheme was employed. First the oligomer was incorporated into the epoxy matrix in an imidazole‐catalyzed reaction and then the crosslinking was completed with an acid‐catalyzed ROP of the residual epoxies. Investigations showed that toughened coatings could be prepared from the inherently brittle epoxy through proper choice of the blending ratio of oligomer to epoxy. The blending increased surface hydrophobicity at high concentrations of functionalized oligomer, but did not have an adverse effect on the inherently advantageous endothelial cell spreading. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3677–3688, 2006     

Preparation and cured properties of diallyl phthalate resin modified with epoxy resin and allyl ester compound having carboxylic acid

An epoxy resin was blended with a diallyl phthalate resin to improve the adhesive properties and the fracture toughness. A compatibilizer was used to reduce the decrease in heat resistance. An allyl ester compound [1,4‐diallyloxycarbonyl‐2,5‐benzenedicarboxylic acid (DAPY)], which reacted with the diallyl phthalate resin and epoxy resin to have allyl groups and carboxylic acids on the end of the molecular chain, was synthesized as a compatibilizer by the reaction of pyromellitic dianhydride with allyl alcohol. These blends were cured with dicumyl peroxide and triethylamine. By modification with the epoxy resin and DAPY, the lap shear adhesive strength to steel increased up to about 3 times that of the diallyl phthalate resin. These results suggest that the secondary hydroxyl group generated by the addition reaction of the epoxy resin and DAPY and the secondary hydroxyl group existing in the molecular chain of the epoxy resin formed hydrogen bonds with the hydroxyl group of water existing on a metal surface, and as a result, the adhesive strength to metal such as steel increased. The fracture toughness of the diallyl phthalate resin was increased by modification with the epoxy resin. The reason for this result was that the flexibility increased because the crosslinking density became small by modification with the epoxy resin. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Adhesion property of crosslinked epoxidized (natural rubber)/(acrylonitrile‐butadiene) rubber blend adhesives in the presence of petro resin tackifier

Loop tack, peel strength, shear strength, and morphology of (benzoyl peroxide)‐cured epoxidized natural rubber (ENR 25)/(acrylonitrile‐butadiene) rubber (NBR) blend adhesive were investigated by using petro resin as the tackifying resin. Benzoyl peroxide loading varied from 1 to 5 parts by weight per hundred parts of resin (phr), whereas the petro resin loading was fixed at 40 phr. A SHEEN hand coater was used to coat the adhesive on the polyethylene terephthalate substrate at 30 μm and 120 μm coating thicknesses. (ENR 25)/NBR adhesive was crosslinked at 80°C for 30 min prior to the determination of adhesion strength by a Lloyd adhesion tester operating at 10–60 cm/min. Results show that maximum loop tack and peel strength occur at 2 phr of benzoyl peroxide loading, whereby optimum cohesive and adhesive strength are obtained. However, shear strength increases with increasing benzoyl peroxide concentration, an observation that is associated with the steady increase in the cohesive strength. Scanning electron microscopy micrograph shows that little adhesive remained on the substrate at 0 phr compared with 2 phr of benzoyl peroxide loading, indicating that crosslinking increases the peel strength of the adhesive. In all cases, the adhesion properties increase with coating thickness and testing rate . J.VINYL ADDIT. TECHNOL., 24:93–98, 2018. © 2015 Society of Plastics Engineers     

Preparation and characterization of polysiloxane‐modified epoxy resin aqueous dispersions and their films

Polysiloxane‐modified epoxy resin aqueous dispersions were prepared by the reaction of amino‐polysiloxane (APS) with a graft epoxy resin that was synthesized with a diglycidyl ether of bisphenol A type epoxy resin and styrene/acrylic acid. The measurements of the epoxy values and FTIR spectra confirmed that this reaction really took place. The modified aqueous dispersion exhibits high viscosity, small particle size, and nearly the same surface tension as the unmodified one. Therefore, this indicates that the siloxane segments could be encapsulated into graft epoxy resin particles during the water dispersion process. For APS‐modified films, the thermal stability and water resistance are remarkably enhanced. Furthermore, lowering of the hardness and surface tension for these films was also observed and the surface composition was measured by X‐ray photoelectron spectroscopy. The experimental data indicate that the siloxane segments easily migrate onto the surface during the film formation process and finally enrich on the surface of the APS‐modified film. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 880–885, 2005     

Simultaneous ultrasonication‐assisted internal mixing to prepare MWCNTs‐filled epoxy composites with increased strength and thermal conductivity

The uniform dispersion of carbon nanotubes in epoxy resin is one of the key factors to achieve the composites with desirable mechanical and physical property enforcement. However, the widely used dispersion methods have their own respective limitations in pursuing satisfactory nanotube dispersion. Herein, a new dispersion approach, based on the synergetic effect of combining high speed internal mixing with running simultaneously continuous ultrasonication treatment, has been proposed. The dispersion of nanotubes was carried out in a high speed internal mixer, consisting of twin kneading block structured rotors and an integrated ultrasonic horn, which was intercalated into the central position between the twin rotors. At first, the FEM simulation was conducted to optimize the kneading element assembly and illuminate the geometry influence of the ultrasonic horn intercalation on the mixing flow. Afterwards, to confirm the feasibility of the approach, pristine MWCNTs (P‐CNTs), oxidation modified MWCNTs (M‐CNTs) and M‐CNTs/multilayer graphene nanoplatelets (MGPs) hybrid are dispersed into epoxy resin. The dispersion of each sample in its liquid epoxy state is investigated under transparent optical microscopy. More characterizations, including SEM, TG/DTA, tensile test, and thermal conductivity measurements, were conducted on the cured composites. Competitive reinforcements on mechanical tensile property and thermal conductivity were observed. Especially, at a 1.5 wt% M‐CNTs/MGPs hybrid content, the composite mechanical tensile strength and thermal conductivity were 47% and 30% higher than those of neat epoxy. This preliminary study demonstrates the feasibility and practicability of the proposed approach to achieving good MWCNTs dispersion and distribution in epoxy resin. POLYM. COMPOS., 37:870–880, 2016. © 2014 Society of Plastics Engineers     

The rheological modification of talc‐filled polypropylene by epoxy‐polyester hybrid resin and its effect on morphology,crystallinity, and mechanical properties

Reactive mixing of polypropylene (PP) and talc with epoxy‐polyester resin was preformed using a corotating twin screw extruder, and the rheology, morphology, crystallization behavior, and mechanical properties of composites were evaluated. The melts of composites mixed with resin exhibited yield stress and the variation of viscosity against frequency can be approximated in two lines with various slopes. The measurement of the suspension viscosity can be used to characterize the microstructural state of dispersion. Empirical formula was used to relate viscosity with particle concentration, and the analysis showed that the maximum volume fraction increases by using small amount of epoxy resin in the formulations. The morphological study of composites by scanning electron microscopy revealed that the use of resin improved the dispersion of talc in PP, which leads to the arrangement of talc platelets in the direction of flow even close to wall of the mold. The differential scanning calorimetry showed that the epoxy resin suppressed the nucleation effect of talc on PP while the degree and rate of crystallization increased. The compatibilization by maleic anhydride‐grafted polypropylene showed a noticeable increase in tensile strength of composites reactively mixed with epoxy resin. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Butyl Acrylate/Vinyl Acetate Emulsion‐Based Pressure‐Sensitive Adhesives: Empirical Modelling of Final Properties

The influence of the amounts of acrylic acid, chain transfer agent and anionic stabilizer on polymer microstructural properties and final adhesive performance of BA/VAc emulsion‐based PSAs on stainless‐steel and high‐density polyethylene substrates was investigated using a Box‐Behnken experimental design for 15 runs. The resulting data were empirically modelled. For each final adhesive property (i.e., loop tack, shear and peel strength), different models were found to fit the data. Similar models for loop tack and peel strength were found to be adequate for different PSA thicknesses on the same substrate. AA and SDS had significant effects on loop tack as did the AA‐SDS and CTA‐SDS two‐factor interactions. Quadratic peel strength models were found to adequately describe the data for SS substrate cases with a noticeable absence of any interaction parameters. The shear strength models were similar regardless of the substrate or thickness of the adhesive (e.g. in all models, AA and CTA, as well as their second‐order interactions, were the significant factors).     

Nanoparticle dispersed resins and composites under quasi‐static loading: Shear plugging behavior

Experimental studies are presented on the quasi‐static shear plugging behavior of nanoparticle dispersed materials viz symmetric balanced cross‐ply laminates made using unidirectional E‐glass fabric with epoxy resin, and neat epoxy resin. The nanoparticles used are nanosilica and multiwalled carbon nanotube for E‐glass/epoxy and nanosilica for epoxy resin. The effect of nanoparticle dispersion on shear plugging strength was evaluated. Shear plugging strength was enhanced up to 10.5% for E‐glass/epoxy and up to 17.0% for neat epoxy resin on addition of nanoparticles. Shear plugging strength of nanoparticle dispersed composites decreased with an increase in specimen thickness. POLYM. COMPOS., 37:3411–3415, 2016. © 2015 Society of Plastics Engineers     

Development of high‐performance epoxy/clay nanocomposites by incorporating novel phosphonium modified montmorillonite

Novel organoclays were synthesized by several kinds of phosphonium cations to improve the dispersibility in matrix resin of composites and accelerate the curing of matrix resin. The possibility of the application for epoxy/clay nanocomposites and the thermal, mechanical, and adhesive properties were investigated. Furthermore, the structures and morphologies of the epoxy/clay nanocomposites were evaluated by transmission electron microscopy. Consequently, the corporation of organoclays with different types of phosphonium cations into the epoxy matrix led to different morphologies of the organoclay particles, and then the distribution changes of silicate layers in the epoxy resin influenced the physical properties of the nanocomposites. When high‐reactive phosphonium cations with epoxy groups were adopted, the clay particles were well exfoliated and dispersed. The epoxy/clay nanocomposite realized the high glass‐transition temperature (T_g) and low coefficient of thermal expansion (CTE) in comparison with those of neat epoxy resin. On the other hand, in the case of low‐reactive phoshonium cations, the dispersion states of clay particles were intercalated but not exfoliated. The intercalated clay did not influence the T_g and CTE of the nanocomposite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Molecular parameters and their relation to the adhesive performance of emulsion acrylic pressure‐sensitive adhesives. II. Effect of crosslinking

Acrylic emulsion pressure‐sensitive adhesive (PSA) films generally have much lower shear holding power than that of their solvent‐borne counterparts for the same peel and tack. This is due to their discrete microgel morphology in the film. In contrast, film cast from solution‐polymerized acrylic PSA forms a continuous network as a result of crosslinking acrylic acid and aluminum acetyl acetonate (AAA) in the film following the solvent evaporation. Novel acrylic emulsion PSA was made by copolymerizing ≤1 wt % isobutoxy methyl acrylamide (IBMA) in the polymer backbone. The IBMA grafted the linear portion of the acrylic polymer with the microgels upon heating the film, which resulted in a significant increase in the shear holding power. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2558–2564, 2001     

Adhesion behavior of natural rubber‐based adhesives crosslinked by benzoyl peroxide

The loop tack, peel, and shear strength of crosslinked natural rubber adhesive were studied using coumarone‐indene and toluene as the tackifying resin and solvent, respectively. The concentration of benzoyl peroxide‐the crosslinking agent—was varied from 1 to 4 parts per hundred parts of rubber (phr). A SHEEN hand coater was used to coat the adhesive on the polyethylene terephthalate substrate at various coating thickness. Loop tack, peel, and shear strength were measured by a Llyod adhesion tester operating at 30 cm min^?1. Result shows that loop tack and peel strength of the adhesive increases up to 2 phr of benzoyl peroxide concentration after which it decreases with further benzoyl peroxide content. This observation is attributed to the optimum crosslinking of natural rubber where optimum cohesive and adhesive strength occurs at 2 phr peroxide loading. However, for the shear strength, it increases with increasing benzoyl peroxide concentration where higher rate of increase is observed after 2 phr of peroxide content, an observation which is associated to the steady increase in cohesive strength of crosslinked rubber. In all cases, the adhesion properties of adhesives increase with increase in coating thickness. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Research on starch‐g‐polyvinyl acetate and epoxy resin‐modified corn starch adhesive

A new corn starch adhesive modified by starch‐g‐polyvinyl acetate (starch‐g‐PVAc) and epoxy resin is described in this study. Starch‐g‐PVAc is used as high cohesive energy component to improve the dry shear strength of the starch adhesive. Although the epoxy resin, which can easily crosslink with the oxidized starch, is used as water‐resistant component to improve the wet shear strength. Because there is no chemical reaction happening between polyvinyl acetate and epoxy resin, both the dry shear strength and the wet shear strength of the corn starch adhesive are notably increased. Considering all the related factors, the optimum of the modification is achieved when the dosage of starch‐g‐PVAc and epoxy resin is 70% of the oxidized starch latex with m(Ep): m(starch‐g‐PVAc) = 1:2. That is, the epoxy resin is 23% in mass fraction and starch‐g‐PVAc 47% in mass fraction. The dry shear strength is 4.50 MPa, and the wet shear strength is 2.51 MPa. The modified corn starch has a broad prospect in the application of plywood industry. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers     

Increased flexural modulus and strength in SWNT/epoxy composites by a new fabrication method

A new method for preparing SWNT/epoxy nanocomposites has been developed which involves high shear mixing of the epoxy resin and SWNT and heat treating the mixture prior to introducing the hardener. The glass transition temperature of the epoxy resin is unaffected by the presence of nanotubes. An improvement of 17% in flexural modulus and 10% in flexural strength has been achieved at 0.05 wt% of nanotubes. These improvements in flexural modulus and strength are attributed to good dispersion of the nanotubes and grafting of epoxy resin to SWNT by an esterification reaction.     

Proper finishing treatments for sun‐protective cotton‐containing fabrics

To enhance both the performance and ultraviolet‐protection properties of cotton‐containing fabrics, attempts have been made to use poly(carboxylic acid)s as non‐formaldehyde durable‐press finishing agents alone or in combination with certain additives followed by posttreatment with metal salt solutions. Furthermore, simultaneous dyeing and resin finishing in the presence of triethanolamine hydrochloride (TEA · HCl) or citric acid (CA) as a reactive additive along with different anionic or cationic dyestuffs have been examined. The results reveal that the ester crosslinking of cotton‐containing fabrics in the absence or presence of chitosan (5 g/L), β‐cyclodextrin (20 g/L), or choline chloride (20 g/L) as an additive results in an improvement in the fabric resiliency as well as the ultraviolet‐protection properties. The extent of the improvement is determined by the type of poly(carboxylic acid), type of additive, type of substrate (i.e., cotton or cotton/polyester blend), and pretreatment history (i.e., grey, bleached, or bleached and mercerized). The posttreatment of easy‐care finished fabric samples with a copper acetate solution (5 g/L) results in a dramatic improvement in the ultraviolet‐protection factor, especially with bleached cotton, grey cotton/polyester blend, and bleached cotton/polyester fabric samples, regardless of the additive. Simultaneous dyeing and resin finishing with Reactive Black 5 and Direct Violet 31, in the presence of TEA · HCL as a reactive additive, or with Basilene Red PB, in the presence of CA as a reactive additive, result in a sharp increase in both the depth of shade and the ultraviolet‐protection values, regardless of the substrate. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1024–1032, 2005