Comparison of tack of pressure-sensitive adhesives (PSAs) at different temperatures

Pressure-sensitive adhesives (PSAs) have applications in the fields of packaging, joining, wound care, and personal care. Depending on the application of the PSA, different performance tests are carried out when new products are developed or the quality of the existing products is checked. Tack is the property of an adhesive that enables it to form instant bond on the surface under light pressure. The tack of a PSA strongly depends on the way the bond is created. Parameters such as the bonded area, contact time and the nature of tack materials all affect the tack force measured. In the development of any PSA, it is desirable to correlate the performance related properties such as tack and peel strength to the rheological behaviour. Finding these correlations would make it possible to evaluate the performance of a PSA using its rheological characteristics. In this investigation we have studied the influence of rheological behaviour of three different PSAs on their tackiness. The three different PSAs used in this study are a low molecular weight rosin ester, high molecular weight rosin ester, and dicyclopentadiene. Various rheological properties such as viscosity, phase angle, and elastic and viscous moduli are measured versus the frequency and temperature. Also the tack properties at various removal speeds and temperatures are evaluated. Analysis of the results indicates different performances of the three PSAs which could be related to their rheological properties, especially the phase angle, at different frequencies and temperatures. The PSA with high molecular weight rosin ester is more sensitive to temperature changes and showed drastic changes in tackiness from high temperature to low temperature. On the other hand, rosin ester with low molecular weight is less sensitive to temperature changes. © 2010 VSP.

Statistical modelling of the rheological and mucoadhesive properties of aqueous poly(methylvinylether-co-maleic acid) networks: Redefining biomedical applications and the relationship between viscoelasticity and mucoadhesion

Poly(methylvinylether-co-maleic acid) (PMVE/MA) is commonly used as a component of pharmaceutical platforms, principally to enhance interactions with biological substrates (mucoadhesion). However, the limited knowledge on the rheological properties of this polymer and their relationships with mucoadhesion has negated the biomedical use of this polymer as a mono-component platform. This study presents a comprehensive study of the rheological properties of aqueous PMVE/MA platforms and defines their relationships with mucoadhesion using multiple regression analysis. Using dilute solution viscometry the intrinsic viscosities of un-neutralised PMVE/MA and PMVE/MA neutralised using NaOH or TEA were 22.32 ± 0.89 dL g-1, 274.80 ± 1.94 dL g-1 and 416.49 ± 2.21 dL g-1 illustrating greater polymer chain expansion following neutralisation using Triethylamine (TEA). PMVE/MA platforms exhibited shear-thinning properties. Increasing polymer concentration increased the consistencies, zero shear rate (ZSR) viscosities (determined from flow rheometry), storage and loss moduli, dynamic viscosities (defined using oscillatory analysis) and mucoadhesive properties, yet decreased the loss tangents of the neutralised polymer platforms. TEA neutralised systems possessed significantly and substantially greater consistencies, ZSR and dynamic viscosities, storage and loss moduli, mucoadhesion and lower loss tangents than their NaOH counterparts. Multiple regression analysis enabled identification of the dominant role of polymer viscoelasticity on mucoadhesion (r > 0.98). The mucoadhesive properties of PMVE/MA platforms were considerable and were greater than those of other platforms that have successfully been shown to enhance in vivo retention when applied to the oral cavity, indicating a positive role for PMVE/MA mono-component platforms for pharmaceutical and biomedical applications.

Design of binary polymeric systems containing ɩ-carrageenan and hydroxypropylcellulose for use in cataract surgery.

This study describes the design and characterisation of the rheological and mechanical properties of binary polymeric systems composed of 2-Hydroxypropylcellulose and ɩ-carrageenan, designed as ophthalmic viscoelastic devices (OVDs). Platforms were characterised using dilute solution, flow and oscillatory rheometry and texture profile analysis. Rheological synergy between the two polymers was observed both in the dilute and gel states. All platforms exhibited pseudoplastic flow. Increasing polymer concentrations significantly decreased the loss tangent and rate index yet increased the storage and loss moduli, consistency, gel hardness, compressibility and adhesiveness, the latter being related to the in-vivo retention properties of the platforms. Binary polymeric platforms exhibited unique physicochemical properties, properties that could not be engineered using mono-polymeric platforms. Using characterisation methods that provide information relevant to their clinical performance, low-cost binary platforms (3% hydroxypropylcellulose and either 1% or 2% ɩ-carrageenan) were identified that exhibited rheological, textural and viscoelastic properties advantageous for use as OVDs.