Various properties of the components and adhesives were modelled. The compatibility of the components were successfully incorporated into an extended Fox equation to predict the glass transition temperature. The peel strength of the adhesive was modelled in terms of the rheological properties of elastic moduli and loss tangent values at different temperatures. A second model based upon the value of the loss tangent at room temperature was also broadly successful but deviations from predicted behaviour were observed which were attributable to failure of the adhesive joints by a mode not included in the model. The modulus of the adhesive was modelled on the basis of an extended mixture rule in which the extent of compatibility was identified by a parameter n. The value of n varied as a function of adhesive composition and temperature, indicating that the behaviour of the adhesives changed subtly as the compatibility of the phases changed. The value of the parameter could not be directly related to the morphology of the adhesive phases. Fourteen commercially available poly(ethylene-co-vinyl acetate) (EVA) copolymer samples were selected in which there was a systematic change in the melt index, amount of vinyl acetate, and degree of crystallinity. Various hot melt adhesives were made using these copolymers and a standard amount of wax and resin. The materials were examined using differential scanning calorimetry (DSC), oscillatory rheometry (both controlled strain and controlled stress), and transient (creep) rheometry. The adhesives were also investigated using a variety of industrial tests which included peel adhesion and tensile testing at four different rates, open and setting time, shear and peel stress resistance at elevated temperatures, and viscosity determination over a wide range of temperatures. Detailed thermal analysis and characterisation have provided a range of accurate and systematic data on all of the materials and in particular showed that the components of the adhesive did not merely act as a mechanical mixture but had a distinct compatibility. The controlled stress technique was found to more discriminatory than the controlled strain, due to the more precisely controlled heating and cooling of the sample during loading and evaluation. Other key differences between the techniques are attributable to the different thermal histories imposed upon the semi-crystalline adhesive components. Detailed analysis of the complex rheological curves showed several key factors. One of the most important was the modulus crossover temperature Tx which was shown to correlate well with the softening point of the adhesive, its open time, and the heat resistance under shear as determined by the shear adhesion failure temperature (SAFT). It was possible to construct a linear relationship between Tx and SAFT which allowed prediction of this key adhesive parameter. There was no significant relationship established between the softening point of an adhesive and its heat resistance, open time, or critical thermal characteristics, and the use of the softening point as a useful indicator of adhesive performance is contested. The open time was shown to be clearly influenced by the properties of the copolymer. The relationship between open time and melt index is complex and two competing mechanisms are thought responsible. These are the inability to fully wet the substrate for high molecular weights and resistance to complete substrate penetration by capillary effects for adhesives formulated with low molecular weight polymers. Both of these effects cause a reduction in open time. The cloud points of the adhesives were independent of the molecular weight but strongly affected by composition. Degree of crystallinity was also an influence at higher molecular weights. Cloud point correlated slightly with the onset of crystallisation as determined by DSC however differences are extremely small and the method was not deemed robust enough for widespread industrial application. Various properties of the components and adhesives were modelled. The compatibility of the components were successfully incorporated into an extended Fox equation to predict the glass transition temperature. The peel strength of the adhesive was modelled in terms of the rheological properties of elastic moduli and loss tangent values at different temperatures. A second model based upon the value of the loss tangent at room temperature was also broadly successful but deviations from predicted behaviour were observed which were attributable to failure of the adhesive joints by a mode not included in the model. The modulus of the adhesive was modelled on the basis of an extended mixture rule in which the extent of compatibility was identified by a parameter n. The value of n varied as a function of adhesive composition and temperature, indicating that the behaviour of the adhesives changed subtly as the compatibility of the phases changed. The value of the parameter could not be directly related to the morphology of the adhesive phases.

A cartonboard package is often sealed and closed with an adhesive – either a hot-melt adhesive (adhesives that are applied in a molten state on the cartonboard) or a dispersion adhesive (adhesives that are applied as water-based dispersions). This thesis focuses on the process of hot-melt gluing, and how material properties and process conditions affect the performance of the adhesive joint. Requirements vary depending on how the package is to be used. A package that is only supposed to protect the product during transport differs from one that is supposed to attract consumers and facilitate their use of the product. If a package has been opened, due to external or internal forces that cause a fracture in the adhesive joint, the consumer may choose another package instead. A fracture of the adhesive joint may occur in several different ways; for example, a cohesive fracture in the adhesive, an interfacial fracture between the adhesive and one of the cartonboard surfaces, and a cohesive fracture in the cartonboard. The traditional way of testing the adhesive joint is to subjectively evaluate the fibre tear after manually tearing the joint apart. The primary interest of this study has been to find an objective method that can characterise the adhesive joint – that is, its strength and joint characteristics. The work has principally concentrated on physical experiments where the Y-peel method has been evaluated and further developed, including the construction of a laboratory adhesive applicator. Adhesive joint failure is analysed and correlated to the force-elongation curve during Y-peel testing in order to explore various mechanisms of the failure. The force versus elongation curves are transformed into a force versus inelastic deformation curve for the adhesive joint. The inelastic deformation of the adhesive joint is defined as the inelastic opening of the adhesive joint perpendicular to the cartonboard surface. The dissipative descending energy has been used to characterise the adhesive joint. High descending dissipative energy showed high resistance against final failure of the joint. This correlates very well with the manual fibre-tear test. Characteristic force-elongation curves in Y-peel testing – that is, the shape of the curve – have been analysed, and four main failure modes have been identified. The finite element method has been used to predict mechanical behaviour in the ascending part of the force-elongation curve. When it comes to local behaviour, a high stiffness adhesive results in bending behaviour while a low results in shearing, but on a global scale, no big difference was detected on the ascending part of the force-elongation curve. The new laboratory adhesive applicator and finite element method can be used to objectively design the interaction between the adhesive and the cartonboard for a specific application. This can be achieved by modifying the cartonboard, the adhesive or the process parameters.

<p>Hot-melt adhesives have been commercially available for a long time and they are used in a wide range of applications. The adhesive performance is governed by the adhesive material property as well as the application conditions for each type of substrate. In order to achieve a good bond between the adhesive and the designated substrate, both wetting ability and open time of the adhesive material have to be considered. Three commercial hot-melts were used in this study in order to examine the relationship between the material property and the adhesive performance. The thermal properties of the materials were obtained through Differential Scanning Calorimetry while Dynamic Analysis (DA) described their viscoelastic behaviour, and the hysteresis loop helped to characterize the flow regime from which the application conditions for the adhesive could be chosen. The adhesive performance was evaluated in term of the force required to break the bond between the adhesive and the substrate through a series of standardized pull-off tests. The effect of the time-temperature trade-off on the adhesive performance by varying the application temperature as well as prolonging the available bond-formation time was also examined. In most cases, the adhesive performance improved with extended open time. However, improved adhesive performance was also shown to be the response of shorter Maxwell characteristic time which was evaluated from the DA data. By providing the characteristic time as a linkage, a relationship between the adhesive performance and the material properties could be established. These results also offer a basis for the formulation of adhesives using structure-property parameters derived from DA.</p> / Master of Applied Science (MASc)

Hot melt adhesives (HMA) are a class of adhesives that, unlike solvent-or waterborne counterparts, do not contain organic solvents or other carriers, and are produced and subsequently applied in a molten state. The main components of HMA are polymers, tackifying resins, and a plasticiser. HMA offer a more environmentally friendly option of adhesive materials.  This study was undertaken to investigate the performance of plasticisers based on renewable resources in HMA. Historically, mineral oil-based plasticisers have been used with great success in HMA formulations, offering a performance benchmark. This work selected suitable alternatives from renewable resources, ranging from fully renewable to fully conventional compositions. During the production stage, the compatibility of such plasticisers with the rest of the HMA formulation was studied while rheological methods were used to investigate the impact of different plasticisers on the properties of the final HMA. Adhesive properties were also assessed by loop tack and peel tests on polyethylene terephthalate (PET) and stainless steel (SS) substrates.   It was shown that some of the studied materials from renewable resources could offer a suitable component in the design of a biobased plasticiser, whose performance matched conventional plasticisers, while the ratio of the biobased fraction was up to 70 % and possibly even higher. The findings of this work show the potential of biobased alternatives in making HMA with a higher degree of sustainability. / Smältlim är en klass av lim som, till skillnad från lösningsmedels-eller vattenburna motsvarigheter, inte innehåller organiska lösningsmedel eller andra bärare, och som produceras och appliceras därefter i smält tillstånd. Huvudkomponenterna i HMA är polymerer, klibbgivande hartser och en mjukgörare. smältlim erbjuder ett mer miljövänligt alternativ för limmaterial. Denna studie genomfördes för att undersöka prestandan hos mjukgörare baserade på förnybara resurser i HMA. Historiskt har mineraloljebaserade mjukgörare använts med stor framgång i HMA-formuleringar, vilket ger ett prestandariktmärke. Lämpliga alternativ valdes ut från förnybara resurser, allt från helt förnybara till helt konventionella kompositioner. Under produktionsstadiet studerades kompatibiliteten av sådana mjukgörare med resten av smältlimsformuleringen medan reologiska metoder användes för att undersöka olika mjukgörares inverkan på egenskaperna hos det slutliga limmet. Vidhäftningsegenskaperna utvärderades också genom loop tack test och peel test på polyetylentereftalat (PET) och rostfritt stål (SS) substrat. Det visades att en del av de studerade materialen från förnybara resurser kunde erbjuda en lämplig komponent i designen av en biobaserad mjukgörare, vars prestanda matchade konventionella mjukgörare, medan förhållandet mellan den biobaserade fraktionen var upp till 70 % och möjligen ännu högre. Resultaten av detta arbete visar potentialen hos biobaserade alternativ för att göra HMA med en högre grad av hållbarhet.