Viscosity and shear strength of natural‐rubber‐based adhesives in the presence of gum rosin and petroresin

The viscosity and shear strength of pressure‐sensitive adhesives based on natural rubber (standard Malaysian rubber grade L) were studied with gum rosin and petroresin as the tackifying resins. Effects of the concentration of the tackifying resin and the molecular weight of rubber on the two properties were systematically investigated. Toluene was used as the solvent throughout the study to prepare the adhesives. The viscosity and shear strength of the adhesives were determined with a rotary viscometer and a texture analyzer, respectively. For the shear test, a hand coater was used to coat the adhesives on the release paper substrate to provide coating thicknesses of 60 and 120 μm. The results indicated that the viscosity increased with the resin loading and molecular weight of rubber increasing. The viscosity of the adhesive prepared from petroresin had a higher value than that of the gum‐rosin‐based adhesive. The shear strength of the adhesives decreased gradually with increasing resin content for both tackifying resins and coating thicknesses, and this observation was attributed to the decrease in the cohesive strength due to the dilution effect of the resins. However, the shear strength passed through a maximum at a molecular weight of rubber of 8.5 × 10⁴ for both resins. The gum‐rosin‐based adhesive consistently showed higher shear strength than that of the petroresin/natural rubber adhesive because of the better cohesiveness and compatibility of the former system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of Blend Ratio and Testing Rate on the Adhesion Properties of Epoxidized Natural Rubber (ENR 25)/Styrene–Butadiene Rubber (SBR) Blend Adhesive

The effect of rubber blend ratio and testing rate on the adhesion properties of epoxidized natural rubber (ENR 25)/styrene–butadiene rubber (SBR) blend adhesive were studied using 40 parts per hundred parts of rubber (phr) of coumarone-indene resin as the tackifying resin. Toluene and poly(ethylene terephthalate) (PET) film were used as the solvent and substrate, respectively. A SHEEN hand coater was used to coat the adhesive on the PET substrate at 30, 60, 90, and 120 µm coating thickness. Viscosity was determined by a Brookfield viscometer whereas loop tack, peel strength, and shear strength were measured by a Llyod Adhesion Tester at various testing rates from 10 to 60 cm/min. Results show that viscosity increases gradually with % ENR 25. However, loop tack, peel strength, and shear strength of adhesives indicate a maximum value at 40% ENR 25, after which the adhesion properties decreases with further increase in % ENR 25. This observation is attributed to the varying degree of wettability which culminates at an optimum value of 40% ENR 25 blend ratio. In all cases, the adhesion properties increase with increasing coating thickness and rate of testing.     

A hot-melt pressure-sensitive adhesive based on styrene–butadiene–styrene rubber. The effect of adhesive composition on the properties

Hot-melt pressure-sensitive adhesives based on styrene-butadiene block copolymers with aliphatic and aromatic tackifying resins and plastifying oils have been analyzed. The importance of the resin structure in the compatibility with the block copolymer and the influence of the different paraffinic-naphthenic character of the oil in PSA performance have been shown. Ternary systems with a fixed polymer content (30%) and with variable resin and oil contents show a good miscibility over the whole range of compositions, and only one glass transition temperature was found in each composition. The relationship between chemical composition and bulk performance are expressed in terms of the visco-elastic behavior of the adhesives, measured by DMTA. It has been shown that at a given resin content there is a minimum on tan δ peak vs. temperature, the melt viscosities present a plateau region and the tack strength shows a maximum. An important conclusion is that phase separation is not a requirement for maximum tack; some restricted miscibility is enough, present in a few microdomains of the blend. © 1996 John Wiley & Sons, Inc.     

石油树脂对热熔胶、压敏胶粘接性能的影响

介绍了石油树脂的分类、增粘树脂的结构特点,国内外热熔胶、压敏胶用石油树脂发展,热熔胶对石油树脂的性能要求;论述了石油树脂与聚合物之间的相客性、石油树脂的软化点、熔融粘度等对热熔胶粘接性能的影响,展望了石油树脂的生产和发展方向.     

Morphology and Viscoelastic Behavior of Styrene-Diene Block Copolymers in Pressure Sensitive Adhesives

Linear (SDS) and radial (SD)_x block copolymers of styrene (S) and dienes (D=butadiene or isoprene), varying in composition and molecular weight, were formulated as pressure sensitive adhesives. The morphology of these compositions was determined by electron microscopy of ultra-thin sections and dynamic viscoelastic measurements were made at 35 Hz between -90° and + 140°C or higher. Pressure sensitive tack and holding power were determined and interpreted in terms of morphological and rheological properties.

A high degree of tack resulted only when the tackifying resin was compatible with the polydiene segments of the block polymer and incompatible with the polystyrene segments, provided also that the polydiene-tackifier phase was the continuum with the polystyrene phase forming spherical domains. All effective tackifying resins raised the glass transition temperature (T_g) of the rubbery phase, but plasticized the polymer at temperatures well above T_g Polystyrene domain connectivity was found to lead to diminished tack in block polymers containing more than 30% styrene, a result of decreased creep compliance on the time scale of the bonding process and failure to achieve full contact with the substrate. For adhesives not limited by contact, tack increased with the loss modulus of the adhesive on the time scale of the debonding process. Holding power (shear resistance) increased with polymer styrene content and molecular weight, the polystyrene domain structure effectively inhibiting viscous flow at temperatures sufficiently below T_g of the styrene blocks.     

Tack and Shear Strength of Adhesives Prepared from Styrene-Butadiene Rubber (SBR) Using Gum Rosin and Petro Resin as Tackifiers

Tack and shear strength of styrene-butadiene rubber (SBR)-based pressure-sensitive adhesive were studied using gum rosin and petro resin as the tackifiers. The concentration of the tackifying resin was varied from 0 to 100 parts per hundred parts of rubber (phr). Toluene was used as the solvent throughout the experiment. The rolling ball technique was used to measure the tack of the adhesive, whereas, shear strength was determined by a TA-HDi Texture Analyser. Results show that the tack of the adhesive increases with increasing tackifier loadings for both tackifier systems. However, shear strength indicates the reverse behavior with increasing resin content, an observation which is attributed to the decrease in cohesive strength as the tackifier concentration is increased. Both tack and shear strength of the adhesives increases with molecular weight of SBR. Adhesive containing petro resin consistently exhibits higher values than the gum rosin system due to better wettability and compatibility in the former system.     

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     

Rheological properties of hot melt pressure-sensitive adhesives based on styrene--isoprene copolymers. Part 1: A rheological model for [sis-si] formulations

The viscoelastic properties of hot melt pressure-sensitive adhesives (HMPSA) based on formulations of block copolymers and tackifying resins have been studied in detail, through the variation of the complex shear modulus, G*, as a function of frequency, y . In this first article, we analyze the individual behavior of the components of HMPSA blends: (1) the two copolymers, styrene-isoprene (SI) diblock copolymer and styrene-isoprene-styrene (SIS) triblock copolymer and (2) two tackifying resins. The viscoelastic behavior of the overall formulation is also presented. We have mainly studied the effects of (1) the molecular characteristics of the SI and SIS copolymers and (2) the composition of the blends (mainly the effect of SI content, S content in SIS and SI, resin content) on the viscoelastic properties. A theoretical approach based on concepts of molecular dynamics leads to a model which describes reasonably well the linear viscoelastic properties of individual components and their formulations. Our systematic study can be used to design new copolymer molecules which can mimic the rheological behavior and end-user properties of regular formulations at room temperature.     

Micromechanisms of Tack of Soft Adhesives Based on Styrenic Block Copolymers

The tackiness of model soft adhesive layers based on styrene‐isoprene‐styrene block copolymers and a tackifying resin were investigated with a flat‐ended cylindrical steel probe. The contact between the probe and the adhesive was maintained for 1 s at a nominal pressure of 1 MPa before being detached at a constant velocity. The effect of resin content, probe velocity during debonding and temperature were systematically investigated. Failure was initiated by two main mechanisms: an interfacial cavitation at low debonding rates, giving relatively low adhesion energies, and a bulk cavitation process at higher debonding rates, which gave much higher adhesion energies. In both cases failure occurred at the end by interfacial detachment of fibrils. The characteristic probe velocity where the transition between these two mechanisms took place was controlled primarily by the linear viscoelastic properties of the adhesives. However, the important quantitative parameters obtained from a tack test, i.e., the maximum debonding stress and the adhesion energy, could not be predicted by the linear viscoelastic properties of these adhesives alone.     

Dependence of adhesion property of acrylonitrile‐butadiene rubber‐based adhesive on zinc oxide concentration

Viscosity and adhesion properties of acrylonitrile‐butadiene rubber (NBR)‐based pressure‐sensitive adhesive were investigated by using zinc oxide as the filler. The zinc oxide loading was varied from 10 to 50 parts by weight per hundred parts of rubber (phr). Coumarone–indene resin, toluene, and polyethylene terephthalate were used as the tackifying resin, solvent, and coating substrate, respectively. Viscosity of the adhesive was measured by a Brookfield viscometer, whereas the loop tack, peel strength, and shear strength were determined by a Lloyd adhesion tester operating at 10 to 60 cm/min. Results show that viscosity increases with zinc oxide loading because of the concentration effect. Loop tack and peel strength pass through a maximum value at 20 phr of zinc oxide concentration, whereas the optimum zinc oxide loading for shear strength is 30 phr. This observation is attributed to the effect of varying degrees of wettability and compatibility of the adhesive on the substrate. In all cases, the adhesion properties of adhesives increase with coating thickness and testing rates. J. VINYL ADDIT. TECHNOL., 23:241–246, 2017. © 2015 Society of Plastics Engineers     

Effect of Testing Rate on Adhesion Properties of Benzoyl-Peroxide-Cured ENR 25/NBR Blend Adhesive Using Gum Rosin and Coumarone-Indene Resin as Tackifiers

Dependence of adhesion properties of benzoyl-peroxide-cured epoxidized natural rubber (ENR 25)/acrylonitrile-butadiene rubber (NBR) blend adhesive on testing rate was systematically studied. Coumarone-indene resin and gum rosin were used as tackifiers. Toluene was used as solvent throughout the study. The SHEEN hand coater was used to coat the adhesive on polyethylene terephthalate at 30 and 120 µm coating thickness. The adhesion properties were measured by a Lloyd adhesion tester operating at different rates of testing. Results showed that the loop tack, peel strength, and shear strength increased with increasing testing rate, an observation that was attributed to the viscoelastic nature of adhesive. In all cases, the adhesion properties of the adhesives also increased with increasing coating thickness.     

JH－3橡胶型压敏胶的研究

介绍了以天然橡胶和丁苯橡胶为主体材料，以烃类树脂为增粘剂压敏胶的制备，并研究了丁苯橡胶、树脂、填料及其它助剂对压敏胶性能的影响。     

The viscoelastic properties of rubber–resin blends. I. The effect of resin structure

Blends of elastomers with the proper concentration of appropriate low molecular weight resins exhibit performance as pressure sensitive adhesives. Viscoelastic properties, which may be related to adhesive performance, were measured on 1:l blends of rubber and resin using a mechanical spectrometer. Significant differences in viscoelastic properties were observed depending upon the resin structure. On plots of G′ and tan δ vs. temperature, the addition of a compatible resin produces a pronounced shift of the tan δ peak to a higher temperature and reduces the modulus in the rubbery plateau. An incompatible resin results in a minor shift in the tan δ peak of the elastomer along with the appearance of a second peak at higher temperature, attributed to a second phase which is predominantly resin. Also, the modulus is increased in the rubbery plateau. A polystyrene resin, M_w about 900, is shown to be incompatible with natural rubber but compatible with styrene–butadiene rubber. A cycloaliphatic poly(viny1 cyclohexane) resin, M_w about 650, prepared by hydrogenating the polystyrene resin, is compatible with natural rubber, but incompatible with styrene-butadiene rubber. An alkyl-aromatic poly(tert-butylstyrene) resin, M_w about 850, which is intermediate in aromaticity between the aromatic polystyrene resin and the cycloaliphatic poly(viny1 cyclohexane) resin, is compatible with both natural rubber and styrene-butadiene rubber. Therefore, the structure of the resin is very important in adjusting the viscoelastic properties of a rubber–resin blend to achieve pressure sensitive adhesive performance.     

Influence of Aging on Autohesive Tack of Brominated Isobutylene-co-p-methylstyrene (BIMS) Rubber in the Presence of Phenolic Resin Tackifier

The role of phenolic resin tackifier on autohesive tack of brominated isobutylene-co-p-methylstyrene (BIMS) rubber was studied by a 180° peel test with particular reference to aging. Phenolic resin showed very little effect on the unaged tack of BIMS rubber. The tack strength of the rubber/resin mixture marginally increased at 1 phr resin concentration, beyond which it decreased. Based on the data on the compression creep, maximum tensile stress, and viscoelastic properties of the rubber/resin mixtures, phenolic resin did not enhance the interfacial viscous flow behavior of the rubber/resin mixtures. The results from dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) confirmed the existence of a phase-separated morphology in the rubber/resin blends even at low resin concentration. Upon aging at 100°C for 36 h, the rubber/resin blend containing 1 phr of phenolic resin showed further increase in tack strength which was attributed to migration of the tackifier to the rubber surface and the changes in the compression creep, viscoelastic behavior, and maximum tensile stress of the rubber/resin mixtures. This is also a function of aging time. Surface energy analysis by contact angle measurement, Fourier Transform Infrared Spectroscopy (FT-IR/ATR) studies, and surface roughness measurement by atomic force microscopy (AFM) elucidate the enrichment of the phenolic resin on the rubber surface upon aging and the mechanism of enhanced tack strength.     

Evaluation of natural rubber latex-based PSAs containing aliphatic hydrocarbon tackifier dispersions with different softening points—Adhesive properties at different conditions

Natural rubber latex-based water–borne pressure sensitive adhesives (PSAs) have been formulated with three aliphatic hydrocarbon water-based dispersions (varying softening points) at two different resin addition levels (25% and 50%). Time–temperature superposition analysis using WLF approximations for adhesive peel has revealed that the adhesives formulated with 50% resin addition level show good adhesive behavior. It has also been determined from time–temperature superposition analysis that peel force increases systematically with softening point and peel rate. Correlation of viscoelastic behavior with adhesive properties suggests that at least 50% resin addition level is needed to bring the natural rubber-based formulations into PSA criteria as defined by Dahlquist and others. Adhesive property evaluations performed on a high surface energy substrate (stainless steel) and low surface energy substrate (LDPE) suggested that optimum tack, peel and shear properties at room temperature were obtained for a formulation containing a higher softening point dispersion (95 °C) at 50% resin addition level. Adhesive peel and tack tend to follow softening point trends as well. A 25% tackifier dispersion addition level did not provide any significant adhesion. Humid aging (50 °C and 100% relative humidity) evaluations of the water–borne adhesives seem to correlate well with the room temperature adhesive property observations.     

Water-based polymers as pressure-sensitive adhesives—viscoelastic guidelines

Water-based polymers have been widely used as pressure-sensitive adhesives (PSAs). This article addresses the fundamental viscoelastic parameters that govern PSA performance. The viscoelastic behavior of polymers before and after resin tackification is investigated. Commercial acrylic, CSBR, natural rubber emulsion polymers, and low M_W petroleum-based hydrocarbon resins with various softening points are used to demonstrate the tackification effects. Basic guidelines for selecting the appropriate polymer/resin system to achieve the target performance are given. © 1995 John Wiley & Sons, Inc.     

Preparation and Properties of Styrene-Ethylene-Buthylene-Styrene Hot Melts

Abstract

Hot melt-type adhesives were prepared by mixing Styrene-Ethylene-Buthylene-Styrene (SEBS) rubber with various tackifying resins. Thermal and peeling properties measured on the resulting blends show that it is indeed possible to produce a working SEBS-based solvent-free adhesive by properly combining the properties of the corresponding components in the formulation.     

Rheological Study on Tack of Pressure-Sensitive Adhesives

It is pointed out that the tack of pressure-sensitive adhesives should be expressed in terms of rolling friction coefficient f of the adhesives. Values of f were determined by both rolling ball and pulling cylinder experiments, and the dependence of f upon viscoelastic properties and thickness of the adhesives was studied. The experimental results were interpreted by the model theory previously proposed. It is also shown that the tack of pressure-sensitive adhesives by the conventional ball tack tests corresponds to f measured at the velocity ranging from v ∼ 10 to v ∼ 10² cm/sec.     

Adhesion properties of benzoyl peroxide crosslinked epoxidized natural rubber (ENR 25)‐based pressure‐sensitive adhesives

Adhesion properties of crosslinked (epoxidized natural rubber)‐based adhesives were studied by using coumarone‐indene, benzoyl peroxide, and toluene as tackifying resin, crosslinking agent, and solvent, respectively. The adhesion properties were measured by a Lloyd Adhesion Tester operating at 30 cm min^?1. Results show that loop tackiness and peel strength pass through a maximum value at 1 phr (parts by weight per hundred parts of resin) of benzoyl peroxide concentration, an observation that is attributed to the optimum crosslinking of epoxidized natural rubber whereby optimum cohesive and adhesive strength are obtained. However, shear strength increases with increasing benzoyl peroxide concentration wherein the higher rate of increase is observed between 0 and 1 phr of benzoyl peroxide content. This observation is associated with the steady increase in cohesive strength as crosslinking is increased. In all cases, the adhesion properties of adhesives increased with increasing coating thickness. J. VINYL ADDIT. TECHNOL., 22:8–12, 2016. © 2014 Society of Plastics Engineers     

A Physical Model to Predict the Thermomechanical Behaviour of Hot-Melt Adhesives

The paper presents a model that allows one to calculate the linear viscoelastic behaviour (complex shear modulus as a function of frequency) and thermomechanical behaviour (complex shear modulus as a function of temperature) of various formulations of hot-melt adhesives containing a polymeric base, a tackifying resin and a crystalline wax. The model takes into account the nature and molecular weight distribution of the polymer, the glass transition temperatures of the polymer and the resin, and the crystallinity of the added wax. A computer program has been derived from the model to simulate the thermomechanical behaviour of the formulations from their composition. It fits, with a reasonable accuracy, the experimental data. The model has been tested for two polymeric bases (EVA and EBA) and two different tackifying resins.