M. S. Sánchez-Adsuar

Influence of the composition on the crystallinity and adhesion properties of thermoplastic polyurethane elastomers

Abstract Crystallinity and adhesion properties of nine thermoplastic polyurethanes (TPUs) prepared by varying the hard-to-soft segments ratio, the molecular weight of the macroglycol (related to the size of the soft segments) and the chain extender size and nature (i.e. hard segments length and morphology) were studied. TPUs structure was characterised using 1 H Nuclear Magnetic Resonance ( 1 H NMR), and their properties were studied using Differential Scanning Calorimetry (DSC) and Wide Angle X-ray Diffraction (WAXD). TPUs were used as raw materials of solvent-based adhesives. The adhesion properties were measured from T-peel tests of solvent-wiped polyvinyl chloride (PVC)/polyurethane adhesive joints. It was found that the composition of the TPUs influenced their structure and properties. An increase in the hard segments content in the TPUs reduced the degree of phase separation and the organisation of their structure, resulting in less crystalline polymers with worse adhesion properties.

Surface modification of synthetic vulcanized rubber

Surface modifications produced by treatments (mainly halogenation) of synthetic vulcanized styrene-butadiene rubber (SBR) leading to increased adhesion properties with polyurethane adhesives have been studied. T-peel tests, scanning electron microscopy (SEM), advancing contact angle measurements, infra-red (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and differential scanning calorimetry (DSC) were used to analyze the nature of surface modifications produced in the rubber. Although some surface heterogeneities were created, physical treatments (ultrasonic cleaning, solvent wiping, abrasion) did not noticeably increase the adhesion strength because certain abhesive substances (e.g. zinc stearate, paraffin wax) cannot be removed from the rubber surface by such treatments. Chemical treatment (chlorination) was carried out using ethyl acetate solutions of trichloroisocyanuric acid (TCI) (1,3,5-trichloro-1,3,5-triazine-2,4,6-trione). Chlorination of SBR with trichloroisocyanuric acid produced a si...

Properties of Polyurethane Elastomers with Different Hard/Soft Segment Ratio

Abstract Three polyurethane elastomers (PU) containing different hard/soft (h/s) segment ratios were prepared. The PUs were characterized using Gel Permeation Chromatography (GPC), DSC, Wide Angle X-ray Diffraction (WAXD). Dynamic Mechanical Thermal Analysis (DMTA), and Stress-controlled rheometry. The surface properties were evaluated from contact angle measurements. The PUs were used as raw materials for solvent-based adhesives, whose adhesion properties were measured from T-peel tests of solvent-wiped polyvinyl chloride (PVC)/polyurethane adhesive joints. The increase in the amount of h/s segment ratio affected the structure and morphology of the PUs, reducing the degree of phase separation and the extent of the secondary interactions between polymer chains. The h/s segment ratio determined the thermal, mechanical, rheological and adhesion properties of the PUs.

Weak Boundary Layers in Styrene-Butadiene Rubber

Abstract In this paper two kinds of weak boundary layers (WBL) in synthetic vulcanized styrene-butadiene rubber are described. i) WBL produced by the presence of antiadhesion compounds of the rubber formulation (zinc stearate, microcrystalline paraffin wax). These WBL cannot be effectively removed by solvent wiping, whether followed by washing with an ethanol/water mix or not. Although this treatment allowed a significant removal of zinc stearate, the paraffin wax concentration on the surface was not greatly reduced, thus, poor adhesion of rubber was obtained. Chlorination with small amounts of ethyl acetate (EA) solutions of trichloro isocyanuric acid (0.5–5 wt% TCI/EA) and/or an extended halogenation treatment increased the adhesion strength and effectively eliminated the zinc stearate from the rubber surface. If an additional heat treatment (50°C/24h) of the chlorinated rubber was also carried out, the WBL was more effectively eliminated and the resulting adhesion was independent of the amount of chlor...

Properties of elastomeric polyurethanes obtained with ϵ-caprolactone macroglycol

Abstract Three elastomeric polyurethanes were obtained by reacting MDI (diphenylmethane-4,4′-diisocyanate) with ϵ-caprolactone macroglycols of different molecular weight (1000–3000 daltons); the chain extender used was 1,4-butane diol. The increase in the molecular weight of the macroglycol modified the degree of phase separation and the interactions between the hard and soft domains in the polyurethane structure. The properties of elastomeric polyurethanes were studied by using Gas Permeation Chromatography, FTIR spectroscopy, DSC, DMTA, rheology (stress-controlled rheometer), contact angle measurements, and T-peel strength tests. The use of low molecular weight macroglycol produced polyurethane with small crystallinity, relatively higher T g and reduced softening enthalpy. Therefore a poor degree of phase separation was produced and reduced mechanical and viscoelastic properties were obtained. On the other hand, a high molecular weight macroglycol improved the degree of phase separation producing better mechanical, viscoelastic and thermal properties in the polyurethanes. Furthermore, the increase in molecular weight of macroglycol increased the adhesion of PVC/polyurethane adhesive joints and further changed the locus of failure.

Relevance of polyurethane configuration on adhesion properties

Abstract Five one-component solvent-based adhesives (series C) prepared from e-polycaprolactone polyurethane (PU) polymers were used to join unchlorinated and chlorinated synthetic vulcanized styrene-butadiene rubber. PU films were characterized by infra-red (i.r.) spectroscopy, differential scanning calorimetry (d.s.c.), wide angle X-ray diffraction (WAXD), gel permeation chromatography (g.p.c.) and advancing contact angle measurements. T-peel tests in styrene-butadiene rubber/PU/styrene-butadiene rubber joints were carried out. The experimental results obtained allowed a distinction of PU films of series C according to their different configuration, i.e. the relative fraction and distribution of hard to soft segments: (i) PU with a relatively low hard/soft segment ratio (C1, C2, C4); and (ii) PU with a relatively high hard/soft segment ratio (C3, C5). A correlation, which was different for unchlorinated and chlorinated rubber, between advancing contact angle measurements, hard/soft segment ratio and T-peel strength of rubber/PU joints was found. For chlorinated rubber/PU adhesive/chlorinated rubber joints, the PU films with the highest surface energy produced the highest T-peel strenght. Furthermore, an interaction between the carboxylic and chlorinated groups on the chlorinated rubber surface and the polyester and/or urethane groups of PU was probably produced, in such a way that the highest T-peel strength corresponds to the polyurethane with the highest relative amount of soft segments.

Rheological characterization of thermoplastic polyurethane elastomers

The relationship between the rheological properties and composition of eight thermoplastic polyurethane elastomers (TPUEs) was evaluated using a stress-controlled rheometer. The composition of the TPUEs was changed by varying the OH/NCO ratio, the chain extender and the molecular weight of the macroglycol used in the synthesis. A high molecular weight macroglycol and a low OH/NCO ratio improved the rheological properties of the TPUEs due to the formation of longer or more abundant soft segments, respectively. The nature of the chain extender influenced the rheological properties to a lesser extent. © 2000 Society of Chemical Industry

Structure, composition, and adhesion properties of thermoplastic polyurethane adhesives

The composition and hard segment content of 13 commercial thermoplastic polyurethane elastomers (TPUs) were obtained using 1H-nuclear magnetic resonance (1H-NMR). The properties of the TPUs were studied using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), dynamic mechanical thermal analysis (DMTA), and contact angle measurements. Solventbased adhesives were prepared by dissolving the TPUs in 2-butanone. Films of the TPUs were obtained by solvent evaporation, and their properties were studied. Adhesion properties were determined from T-peel tests on solvent-wiped poly(vinyl chloride) (PVC)/polyurethane adhesive joints. The influence of the segmented structure on the properties of the TPUs was assessed. The increase in the hard segment content in TPUs favoured the incompatibility (i.e. reduced phase separation) between hard and soft domains. TPUs with a high hard segment content had a low crystallinity, a low wettability, and a high joint strength. The storage and loss moduli obtained using DMTA decreased as the hard segment content in the TPUs increased. Furthermore, the TPUs prepared using ε-polycaprolactone as the macroglycol had a slower crystallization rate than those prepared using the polyadipate of 1,4-butanediol or the polyadipate of 1,6-hexanediol. The increase in the length of the hydrocarbon chain of the macroglycol improved both the rheological and the thermal properties of the TPUs. Finally, TPUs prepared using MDI as the isocyanate showed a higher crystallinity and a higher degree of crosslinking than those prepared using TDI.

Characterization of Thermoplastic Polyurethanes Prepared Using Different Macroglycols

Abstract Three polyurethane elastomers (PUs) were prepared using macroglycols of different nature (varepsilon-polycaprolactone, polyadipate of 1,6-hexanediol) and length of the hydrocarbon chain (polyadipate of 1,4-butanediol, polyadipate of 1,6-hexanediol). The PUs were characterized using Gel Permeation Chromatography, Differential Scanning Calorimetry, Wide X-ray angle Diffraction, Dynamic Thermal Mechanical Analysis, stress-controlled rheometry and stress-strain experiments. The surface properties were evaluated from contact angle measurements. The PUs were used as raw materials for solvent-based adhesives, whose adhesion properties were measured from T-peel strength of plasticized poly(vinyl chloride) (PVC)/polyurethane adhesive joints. The use of polyadipate of 1,6-hexanediol produced a polyurethane with high crystallinity (i.e. poor rheological and mechanical properties) and enhanced interactions between soft segments. Low adhesion was obtained in joints produced with this polyurethane and a cohesi...

Improved Adhesion Properties of Polyurethane Adhesive Containing Fumaric Acid

Abstract Different amounts (0.5–3 wt%) of fumaric acid (FA) were added to a solvent-based polyurethane (PU) adhesive. Addition of FA produced a decrease in viscosity and changed the rheological and viscoelastic properties of the liquid PU adhesive, which was more marked upon increasing the time after the adhesive was prepared and more noticeable for high amounts of FA. According to molecular weight distribution, differential scanning calorimetry, thermal mechanical analysis and thermogravimetry measurements, the addition of FA seemed to produce a reaction with the polyurethane (possibly an acid-catalyzed transesterification reaction) which resulted in chain cleavage, disruption of polyurethane crystallinity and a loss of physical properties. These modification in PU structure did not affect the surface energy value of the PU adhesive although the T-peel strength of roughened rubber/PU adhesive/roughened rubber joints increased when the PU adhesive contained FA. This improvement was due to the removal of a...