Water-based Pressure-sensitive Adhesives Research Articles

Development and Evaluation of Novel Water-Based Drug-in-Adhesive Patches for the Transdermal Delivery of Ketoprofen.

The objective of this study was to develop novel water-based drug-in-adhesive pressure-sensitive adhesives (PSAs) patches for the transdermal delivery of ketoprofen, employing poly(N-vinylpyrrolidone-co-acrylic acid) copolymer (PVPAA) and poly(methyl vinyl ether-alt-maleic anhydride) (PMVEMA) as the main components. The polymers were crosslinked with tartaric acid and dihydroxyaluminium aminoacetate using various polymer ratios. Ketoprofen was incorporated into the PVPAA/PMVEMA PSAs during the patch preparation. The physicochemical properties, adhesive properties, drug content, release profile, and skin permeation of the patches were examined. Moreover, the in vivo skin irritation and skin adhesion performance in human volunteers were evaluated. The patches prepared at a weight ratio of PVPAA/PMVEMA of 1:1 presented the highest tacking strength, with desirable peeling characteristics. The ketoprofen-loaded PVPAA/PMVEMA patches exhibited superior adhesive properties, compared to the commercial patches, because the former showed an appropriate crosslinking and hydrating status with the aid of a metal coordination complex. Besides, the permeated flux of ketoprofen through the porcine skin of the ketoprofen-loaded PVPAA/PMVEMA patches (4.77 ± 1.00 µg/cm2/h) was comparable to that of the commercial patch (4.33 ± 0.80 µg/cm2/h). In human studies, the PVPAA/PMVEMA patches exhibited a better skin adhesion performance, compared with the commercial patches, without skin irritation. In addition, the patches were stable for 6 months. Therefore, these novel water-based PSAs may be a potential adhesive for preparing drug-in-adhesive patches.

A sequential design approach for in situ incorporation of cellulose nanocrystals in emulsion-based pressure sensitive adhesives

Cellulose nanocrystals (CNCs) are naturally-sourced nanoparticles that can be used to modify polymers and provide exceptional mechanical properties to nanocomposite materials. In this study, CNCs were incorporated into water-based pressure sensitive adhesives (PSAs) via in situ semi-batch emulsion polymerization to improve PSA properties. A sequential design approach was used to improve CNC/poly(n-butyl acrylate/vinyl acetate) nanocomposite PSAs. In the first part of the design, the effects of acrylic acid (AA) and anionic surfactant sodium dodecyl sulfate (SDS) were examined in the presence of 0.5 wt% CNCs (based on polymer mass). While the SDS was crucial to maintaining latex stability, its excessive addition led to a decrease in PSA performance, namely tack and peel strength. The AA comonomer was pivotal in improving the shear strength of the PSAs, especially in the presence of CNCs. In all cases, the addition of CNCs led to improved PSA shear strength. In the second part of the design, the addition of 1-dodecanethiol (NDM) as a chain transfer agent (CTA) with CNC levels up to 1 wt% led to an improvement in tack and peel strength but at the cost of diminishing the shear strength. Generally, the addition of CNCs improved PSA performance. Thus, to maximize the impact of CNCs on PSA properties, a careful balance of SDS (for latex stability), AA (to improve shear strength) and NDM (to improve tack and peel strength) are needed.

Passivation of pressure sensitive adhesive stickies by addition of acrylic fibers to OCC pulp before papermaking

This study investigated the addition of acrylic fiber to old corrugated container (OCC) pulp as a possible means of overcoming adverse effects of water-based pressure sensitive adhesives during manufacture of paper or paperboard. Such adhesives can constitute a main source of stickies, which hurt the efficiency of the papermaking process and make tacky spots in the product. The highest amount of acrylic fiber added to recycled pulps generally resulted in a 77% reduction in accepted pulp microstickies. The addition of acrylic fibers also increased pulp freeness, tear index, burst strength, and breaking length, though there was a reduction in screen yield. Hence, in addition to controlling the adverse effects of stickies, the addition of acrylic fibers resulted in the improvement of the mechanical properties of paper compared with a control sample.

Wetting Agents - boon or bane?

Although additives are the smallest component of an adhesive formulation, they have a significant influence on its overall properties. The impact of additives is often in inverse proportion to the amount of additive used. Whether an additive is boon or bane depends primarily on the overall formulation of the adhesive in question. In order to find out in more detail about the effect of additives and, in this case, wetting agents in particular, extensive studies were carried out using water-based pressure-sensitive adhesives.

An instrumented mixer setup for making tackifier dispersions used to make pressure-sensitive adhesives

Water-based pressure-sensitive adhesives (PSAs) are made by combining a tackifier dispersion and a polymer latex. During the process of making the tackifier dispersion, the system initially forms a water-in-oil emulsion, and then inverts to an oil-in-water one as more water is continuously added with constant agitation. To better understand the process, an instrumented mixer setup was constructed to simulate the manufacturing process, and agitation was provided by an inner impeller and an outer impeller. Several variables were monitored in situ. They are the electrical resistance of the emulsion, torque exerted on the inner impeller, agitation speeds of both impellers, power consumption of both impellers and the flow rate of feeding water. Our measurements showed that torque reached a maximum at phase inversion, and this was verified by direct measurements of viscosity during the process. Simultaneously electrical resistance measurements monitored the chemical changes as well as phase inversion. Experiments showed that under a certain low water feeding flow rate, there appeared to be an intermediate agitation speed at which the phase inversion occurred the earliest. This, from the industrial standpoint, is really favorable due to both time and energy efficiency. Furthermore, this intermediate agitation speed also corresponded to a better quality product. All this information may be used for optimizing this process in the future.

Optimizing the Monomer Composition of Acrylic Water-Based Pressure-Sensitive Adhesives To Minimize Their Impact on Recycling Operations

Results are reported on a study of the variables controlling the impact that acrylic water-based pressure-sensitive adhesive (PSA) has on paper recycling operations. Surface, bulk, and performance properties of 25 commercial acrylic water-based PSAs were characterized and compared against their laboratory-measured screening removal efficiencies. No correlation was discernible. However, the results did indicate that the use of both vinyl acetate and acrylic acid monomers produced adhesives that readily fragment during repulping operations, resulting in little or no removal via screening. Study of a model system developed to further examine this phenomenon demonstrated that replacing these monomers with those possessing greater hydrophobicities, gauged here with their octanol−water distribution coefficients, produced a substantial increase in measured removal efficiencies. The improvements correlate with the wet tensile strengths of water-soaked adhesive films. The measured dependency of removal efficiencie...

Viscoelastic behaviour of water-based pressure sensitive adhesives (PSAs)

Water-based pressure sensitive adhesives (PSA) obtained by emulsion polymerization have peculiar characteristics compared with their solvent counterparts. In particular they contain significant amount of microgels, permeated by uncrosslinked molecules, and generate micronetworks after film formation. Viscoelastic characterisation of three PSAs, both in the linear limit and in uniaxial elongation is reported in this paper. Modelling of tensile stress-strain curves is proposed, based on a network theory accounting for the presence of entanglements (Ball et al. Polymer, 1981, 22, 1010–1018). A rate-dependence of some of the physical parameters of the model is introduced in order to describe experimental data.

The Influence of Surfactants on the Peel Strength of Water-based Pressure Sensitive Adhesives

In order to study the effect of surfactants on the adhesive properties, peel measurements were performed with two series of model polymers of ethylhexylmethacrylate (PEHMA), the first prepared by emulsion polymerization with four anionic surfactants, and the second by post-adding the same surfactants to a surfactant-free latex. Cohesive fracture is observed at low peel rates; the peel strength depends on the bulk mechanical properties and is independent of the emulsifier. A transition to another type of separation occurs at higher peel rates, which seems to be an interfacial failure by visual inspection. Surface analytical studies, however, give evidence that this “interfacial” failure is, in fact, a mixed failure, leaving traces of the polymer on the substrate surface. The peel rate at this transition as well as the peel strength at mixed fracture are influenced by the surfactants. Large differences were observed between the four surfactants as well as between both series of polymers, leading to the conclusion that the surfactants have a different mobility within the film. This is also reflected by a different aging behaviour of the films.