Carboxymethylated polysaccharide-based films as carriers for acrylic pressure-sensitive adhesives

A novel application of a biodegradable polysaccharide-based film as a pressure-sensitive acrylic adhesive carrier has been reported. For film preparation carboxymethyl derivatives of starch (CMS) and cellulose (CMC) have been used. Based on physicochemical tests results (solubility in water, moisture absorption, mechanical properties) the most promising CMS/CMC 50/50 wt% film was selected as a carrier for an acrylic pressure-sensitive adhesive tape. Prepared double-sided self-adhesive tapes were characterized by good tack 5 N/2.5 cm, peel adhesion 12 N/2.5 cm and shear strength 90 N/6.25 cm² at 20 °C. Such acrylic self-adhesive tapes could find application in the paper industry.     

Miscibility and Probe Tack of Acrylic Pressure Sensitive Adhesives—Acrylic Copolymer/Tackifier Resin Systems

Miscibility between acrylic copolymers and tackifier resins are investigated in terms of phase diagrams, and the probe tack of the blends are measured as a function of both temperature and rate of separation in order to obtain the master curves. It is found that the probe tack of the pressure sensitive adhesives are closely related to the miscibility between the components. The master curves of the miscible blends shift along the X(rate)-axis according to the change of T_g of the bulk materials with a gradual variation of the peak heights. However, those of the immiscible blends will not shift along the X(rate)-axis, but the magnitude will decrease with increase of a dispersed phase.     

Miscibility and mechanical properties of quaternized polysulfone/benzoyl guar gum blends

Novel blends from quaternized polysulfone (QPSF) and benzoyl guar gum (BGG) coded as QB with different contents (10–80 wt%) were prepared through solution casting method. Simultaneously, other kinds of blends were prepared from chloromethylated polysulfone (ClPSF) and BGG coded as ClB to compare the effects of the substituted groups on the miscibility and properties of the composite materials. The effect of BGG content on QB blends was investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atom force microscopy (AFM), differential scanning calorimetry (DSC) and tensile tests. The results revealed that QB blends had good or certain miscibility over the entire composition ratio of BGG to QPSF under study. Compared with ClB blends, QB blends exhibited stronger interfacial attraction and better phase mixing as a result of the relatively strong hydrogen bonding and the specific electrostatic interaction between QPSF and BGG. The occurrence of strong interaction between QPSF and BGG played a key role in improving the material performance. With an increase of BGG content in the blends, the tensile strength of QB blends increased from 33.1 to 44.3 MPa. Furthermore, the mechanical properties of QB-20 blend at different RH were also discussed. It was found that the composite properties changed considerably with moisture content, which attributed that water molecules had a great effect on the hydrogen bonding between the two polymers.     

Microsphere pressure sensitive adhesives—acrylic polymer/montmorillonite clay nanocomposite materials

In this study, the synthesis and characterization of acrylic polymer/montmorillonite (MMT) clay nanocomposite pressure sensitive adhesives (PSA) are presented. Different types and amounts of modified and unmodified montmorillonite clays were dispersed in ethyl acrylate (EA)/2-ethylhexyl acrylate (2-EHA) monomer mixture, which was then polymerized using a suspension polymerization technique. Polymerization was monitored in-line using attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy. The adhesion properties of the synthesized nanocomposite materials were determined using standard measurements of tack, peel and shear strength. Viscoelastic properties of dried adhesive films were analyzed using dynamic mechanical analysis (DMA). The results showed that the kinetics of suspension polymerization was independent of the addition of MMT clays. On the other hand, adhesive properties were strongly influenced by the type and the amount of MMT clay added. While peel strength and tack gradually decreased with higher amount of modified MMT clay, a substantial increase in shear strength was determined with a maximal value at 1 wt% of added MMT clay. Moderate influence on tack, peel and shear strength was observed when the unmodified type of MMT clay was used. DMA analysis showed an increase in storage modulus (G′) for adhesives synthesized with MMT clay addition, but no significant differences were determined between particular types of MMT clays. A decrease in tan δ value for adhesives with 1 wt% of added MMT clay was observed, which also concurs with higher shear strength and implies to the improved cohesion of adhesive.     

The effect of polymer molecular weight and crosslinking reactions on the adhesion properties of microsphere water-based acrylic pressure-sensitive adhesives

In this work, the effect of polymer molecular weight and crosslinking reactions on the end-use properties of the microsphere water-based acrylic pressure-sensitive adhesives (PSA) is presented. Polymer molecular weight and polymer microstructure were regulated using different chain transfer agent (CTA) concentrations and by addition of a diacrylic monomer (MM). The adhesion properties of the synthesized PSAs were characterized via measurements of tack, peel adhesion and shear strength. The results of experiments have shown that the kinetics of suspension polymerization is relatively independent on the amount of CTA and MM. The amount of gel phase in the adhesive was reduced with increasing amount of CTA agent, and gel phase amount may be considered as a function of polymer molecular weight. With a combination of CTA and MM was possible to regulate the amount of formed gel phase in the adhesive, as well sol phase molecular weight. All of the measured adhesion properties strongly depend on molecular weight of the synthesized polymer and on the amount of gel phase. For adhesives synthesized solely with addition of CTA, tack decreased with lower polymer molecular weight and consecutively also with lower amount of gel phase. The same trend was also observed for peel strength measurements, whereas a cohesive failure was observed for adhesives with low amount of gel phase. A maximum value for tack and shear strength was observed at 80 wt% of gel phase. In case of syntheses with a combination of CTA and MM (amount of gel phase in range from 70 to 80 wt%), tack values were distributed in quite narrow range. On the other hand, peel strength values decreased in comparison with adhesives synthesized only with CTA, regardless to the equal amount of gel phase. Poor shear strength was observed for all adhesives synthesized by combination of CTA and MM.     

Contact time dependence of tack for crosslinked polyacrylic pressure-sensitive adhesives with two different molecular structures

The influence of molecular structure of pressure-sensitive adhesive on the wetting to adherend surface was investigated. For this purpose, crosslinked poly(n-butyl acrylate-acrylic acid) (A) and poly(2-ethylhexyl acrylate-acrylic acid) random copolymer (B) with an acrylic acid content of 5 wt% and various crosslinking degrees were used. Tack was measured by a probe tack test with a debonding rate of 10 mm/s and various contact times ranging from 3 to 30,000 s. The probe was made of stainless steel (SS). The tack increased with contact time and the degree of tack rising was B>A. The tack was A>B below the contact time of about 100 s, whereas it was B>A above 100 s. The order of molecular mobility was B>A from pulse nuclear magnetic resonance analysis, so the wettability to adherend surface became B>A. This is the reason why tack was B>A above 100 s. The interfacial tension at a water/toluene interface was decreased more effectively by A than B. This result indicates that the acrylic acid unit in A forms the interaction with the high energy surface such as SS in short contact time. The 2-ethylhexyl group is bulker than the n-butyl group. The bulky group promotes steric hindrance for the interaction of the acrylic acid unit. This seems to be the reason why tack was A>B below 100 s.     

Application of selected 2-methylbenzothiazoles AS cationic photoreactive crosslinkers for pressure-sensitive adhesives based on acrylics

Since their introduction half a century ago, acrylic pressure-sensitive adhesives have been successfully applied in many fields. They are used in self-adhesive tapes, label signs, marking films and protective films as well as in medical pharmaceutical applications for plaster, in dermal dosage systems and in a wide range of biomedical electrodes. In the last 15 years or so, the UV technology, especially UV-crosslinking, is well established in the market and allows the production of UV-crosslinkable pressure-sensitive adhesives (PSA) based on acrylics with interesting performance. So much so that the larger manufacturers of pressure-sensitive adhesive materials and their suppliers now use very expensive equipment to study pressure-sensitive adhesive behavior: tack, peel adhesion and shear strength. The balance between adhesive and cohesive strength after the crosslinking process is very important and critical for properties of acrylic PSA in form of self-adhesive films. In this work the cationic UV-crosslinking of acrylic PSA containing epoxy groups in their structure and additionally cationic photoinitiators based on 2-methylbenzothiazoles as photoreactive crosslinkers have been investigated using UV-lamp as ultraviolet sources. The investigated acrylic PSA were synthesized from 80 wt% of butyl acrylate, and 20 wt% of glycidyl methacrylate. The use of selected photoreactive crosslinkers: 1,5-bis[N,N׳-(2-methylbenzothiazolium)]pentane diiodide and 1,10-bis[N,N׳-(2-methylbenzothiazolium)]decane diiodide allows manufacturing of high quality PSA materials with interesting properties, such as high tack, high peel adhesion, and excellent shear strength.     

Effect of N,N-dimethylacrylamide (DMA) on the comprehensive properties of acrylic latex pressure sensitive adhesives

Acrylic pressure sensitive adhesive (PSA) latexes were synthesized via a monomer-starved seeded semi-continuous emulsion polymerization process with butyl acrylate (BA), methyl methacrylate (MMA), N,N-dimethylacrylamide (DMA), acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) as monomers. Impacts of DMA on the resultant latex and PSA properties were comprehensively investigated. Results indicated that latex particle size was independent of the amount of DMA in the pre-emulsion feed with excessive and constant surfactant concentration. Latex viscosity increased with DMA concentration. It was also found that water resistance of acrylic latex PSA became worse by the presence of DMA, confirmed by water contact angle measurements. Besides, DSC results showed that as the amount of DMA increased, glass transition temperatures (T_g) of the polymers were elevated significantly. TGA results showed that thermal stability of PSA was improved with DMA as a co-monomer. Furthermore, as DMA amount increased, gel content slightly increased, while sol molecular weight (M_w, M_n) of the polymer decreased. Finally, with respect to the adhesive properties of the PSA, it was observed that loop tack initially increased and then decreased with the addition of DMA from 0 to 4 wt%, and the maximum value appeared at 1 wt%. Peel strength reduced, while shear strength improved with increased DMA concentration.     

Synthesis of HfB2 powders by mechanically activated borothermal reduction of HfCl4

HfB₂ powders were synthesized via a borothermal reduction route from mechanically activated HfCl₄ and B powder blends. Mechanical activation of the powder blends was carried out for 1 h in a high-energy ball mill using hardened steel vial and balls. Mechanically activated powders were subsequently annealed at 1100 °C for 1 h under Ar atmosphere. Then, purification processes such as washing with distilled water and leaching in HCl solution were applied for the elimination of the undesired boron oxide (B₂O₃) phase and the probable Fe impurity. The effect of boron amount on the microstructure of the resultant powders was investigated. The boron amount in the starting blends plays an important role in the formation of the HfO₂ phase. HfB₂ powders without any detectable HfO₂ were prepared by adding 20 wt% excess amount of boron. Microstructural analyses of the mechanically activated, annealed and purified powders were performed using X-ray diffractometer (XRD), particle size analyzer (PSA), stereomicroscope (SM), scanning electron microscope/energy dispersive spectrometer (SEM/EDS) and transmission electron microscope (TEM).     

Miscibility studies of hydroxypropyl cellulose/poly(vinyl pyrrolidone) in dilute solutions and solid state

The miscibility of hydroxypropyl cellulose (HPC) and poly(vinyl pyrrolidone) (PVP) blends in aqueous solutions was studied using viscosity, ultrasonic velocity, and refractive index techniques at 30°C. The interaction parameters ΔB, μ, and α calculated from viscosity using Sun and Chee methods indicated the miscibility of this blend. This was further confirmed by ultrasonic and refractive index results. The HPC/PVP blend films are prepared by solution casting method and are analyzed by differential scanning calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopic techniques that confirmed the complete miscibility. This miscibility is due to the strong intermolecular H-bonding interactions between  OH groups of HPC and CO groups of PVP. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Optical and thermo-mechanical properties of composite films based on fish gelatin/rice flour fabricated by casting technique

Packaging films based on fish gelatin-rice flour (FG-RF) at different blend ratios (FG-RF ≈ 10:0, 8:2, 6:4, 5:5 and 0:10, w/w) using 30% (w/w) glycerol as plasticiser were prepared and characterised. FG-RF composite films exhibited lower tensile strength (TS) and elongation at break (EAB), compared to FG film (P < 0.05). Higher water vapour permeability (WVP), but lower water solubility (WS) was obtained for FG-RF composite films having the increased proportion of RF (P < 0.05). Light transmission in ultraviolet (UV) and visible regions (200–800 nm) was lowered in all FG-RF composite films, indicating excellent light barrier characteristics. Based on FTIR spectra, significant changes in molecular structure and lower intermolecular interactions between FG and RF molecules were found in FG-RF (8:2) composite film. Thermogravimetric analysis indicated that FG-RF (8:2) composite film had only 7.61% (w/w) heat-stable mass residues in the temperature range of 50–600 °C. DSC thermograms suggested that FG-RF (8:2) composite film consisting of amorphous/microcrystalline layers of partially miscible aggregated junction zones and the coexisting two different order phases of unbound domains. SEM micrographs elucidated that FG-RF (8:2) composite film was rougher than FG film, but no signs of phase separation between film components were observed, thereby confirming their potential use as packaging material.     

Miscibility and PSA Performance of Acrylic Copolymer and Tackifier Resin Systems

The influence of miscibility of an acrylic PSA and several tackifier resin systems upon PSA performance was investigated. When the acrylic copolymer and the resins were blended in various proportions, three types of mixing state were found: miscible system, partially miscible system and immiscible system. In the case of miscible systems, PSA performance (tack, peel strength and shear resistance) depended upon the viscoelastic properties of the PSA. In the case of completely immiscible systems, the above PSA performance depended primarily upon the viscoelastic properties of a continuous matrix phase, and the separated resin phase acted as a kind of filler. In the case of partially miscible systems, the PSA performance changed discontinuously at the resin concentration where phase separation occurred. It suggests that the phase structure of a PSA greatly influences the PSA's performance.     

Miscibility and PSA Performance of Acrylic Copolymer and Tackifier Resin Systems

The influence of miscibility of an acrylic PSA and several tackifier resin systems upon PSA performance was investigated. When the acrylic copolymer and the resins were blended in various proportions, three types of mixing state were found: miscible system, partially miscible system and immiscible system. In the case of miscible systems, PSA performance (tack, peel strength and shear resistance) depended upon the viscoelastic properties of the PSA. In the case of completely immiscible systems, the above PSA performance depended primarily upon the viscoelastic properties of a continuous matrix phase, and the separated resin phase acted as a kind of filler. In the case of partially miscible systems, the PSA performance changed discontinuously at the resin concentration where phase separation occurred. It suggests that the phase structure of a PSA greatly influences the PSA's performance.     

Miscibility of poly(2,6-dimethyl-1,4-phenylene oxide)/poly(vinyl pyrrolidone) blends

The miscibility of blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and poly(vinylpyrrolidone) (PVP) was studied by differential scanning calorimetry (DSC) through the analysis of the glass transition temperature Tg. The dependence of Tg with the annealing temperature was determined for PPO and PVP samples of different molecular weights. The phase diagrams for blends containing three different PVP samples were established. Blends of PPO and PVP were found to be miscible for composition lower than 30% and higher than 65% of PVP. A inmiscibility window between 30 and 65% of PVP is also described.     

Mechanistic studies in tackified acrylic emulsion pressure sensitive adhesives

Twenty‐three wt % aqueous tackifier dispersion based on glycerol ester abietic acid (T_g = 64°C, M_w = 940) was added to emulsion polymer 50/32/15/3 poly(2‐ethyl hexyl acrylate‐co‐vinyl acetate‐co‐dioctyl maleate‐co‐acrylic acid) pressure sensitive adhesive (PSA). From these latices, 25 μm thick films were cast. The films were dried at 25°C for 24 h or at 121°C for 5 min. Dynamic mechanical analysis (DMA) of the films included measuring elastic modulus (G′) and damping factor (tan δ). Under the above drying conditions, the films did not produce significant differences in their DMA and PSA properties as measured by loop tack, peel, and shear holding power. DMA of the tackified acrylic film showed thermodynamic miscibility between the tackifier and polymer regardless of the drying conditions. Microgels formed during emulsion polymerization of the acrylic PSA brought inherent weakness to the tackified film properties. In the neat acrylic PSA film, these discrete networks entangled with the uncrosslinked chains while in the tackified film, these networks could not form entanglements due to the increased molecular weight between entanglements for the uncrosslinked chains. This lack of network entanglements caused shear holding power of the tackified acrylic PSA film to be 4× lower than that of the neat acrylic PSA film. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1965–1976, 2000     

Pressure Sensitive Adhesive Properties and Miscibility in Blends of Poly(vinyl ethylene-co-1,4-butadiene) with Hydrogenated Terpene Resin

The pressure sensitive adhesive (PSA) properties of two samples of poly(vinyl ethylene-co-1,4-butadiene) (V-BR) (vinyl content: 47.4 and 60 wt%) blended with hydrogenated terpene resin (CLEARON P125) were measured on blend compositions having CLEARON P125 contents (by weight) of 10%, 30% and 50%. The maximum values of 180° peel adhesion, rolling ball tack and probe tack were observed with a V-BR/CLEARON P125 70/30 blend, whereas the maximum values of holding power were obtained with a 50/50 V-BR/CLEARON P125 blend. In these blends, the miscibility between V-BR and CLEARON P125 was confirmed by means of SEM, DSC and light scattering. The influences of surface tension and dynamic mechanical properties on PSA properties were investigated. The surface tension values were essentially the same in all the V-BR/CLEARON P125 blends. Minimum values of storage modulus G' and loss modulus G' at room temperature in V-BR/CLEARON P125 blends were obtained with a 70/30 blend. Thus, it is believed that in V-BR/CLEARON P125 blends, 180° peel adhesion and tack are related to the dynamic mechanical properties.     

Miscibility and fracture energy of probe tack for acrylic pressure-sensitive adhesives: acrylic copolymer/tackifier resin systems

The relationship between the miscibility of acrylic pressure-sensitive adhesive (PSA) and the fracture energy (W) (Jm⁻²) of the probe tack was investigated, wherein the master curve of W was compared with that of the maximum force (σ_max) (gf) of the probe tack. It was ascertained that W of acrylic PSA was closely related to the miscibility between the components (acrylic copolymer and tackifier resin). In the case of the miscible blend system, the master curve of W shifted toward the lower rate side and, at the same time, the magnitude decreased as the tackifier resin content increased. The degree of the shift of W was extremely smaller than that of σ_max. In the case of the immiscible blend system, the master curve of W remarkably decreased as the tackifier resin content increased, which suggests the fact that W of the PSA depended on the dynamic mechanical properties of the matrix phase and that the resin-rich phase acted as a kind of filler, thus reducing the practical performance. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 581–587, 1998     

Hydrogen bonding interactions and miscibility studies of poly(amide)/poly(vinyl pyrrolidone) blends containing mangiferin

Miscibility studies of amorphous poly(amide)/poly(vinyl pyrrolidone) (PA/PVP) blends containing a crystalline phytochemical called “mangiferin” have been carried out using differential scanning calorimetry, Fourier transformed infrared spectroscopy and polarized optical microscopy. The binary blends of PA/PVP prepared from dimethylsulfoxide solutions were found to be completely miscible showing a systematic movement of a single glass transition temperature over the entire composition range. The FTIR study indicated the occurrence of cross-hydrogen bonding interactions between PA and PVP, which may be responsible for complete miscibility of the PA/PVP pair. Moreover, cross-hydrogen bonding promotes miscibility in binary blends of PA/mangiferin and PVP/mangiferin. However, the addition of mangiferin to PA/PVP blends has resulted in liquid-liquid phase separation between PA/mangiferin and PVP/mangiferin phases due to the preferential affinity of mangiferin to PVP than to PA. With increasing mangiferin concentration, liquid-liquid phase segregations occur between PA + mangiferin and PVP + mangiferin phases in addition to the solid-liquid phase transition of mangiferin crystals. Lastly, a ternary morphology phase diagram of the PA/PVP/mangiferin blends was established, which exhibited various coexistence regions such as isotropic, liquid + liquid, liquid + crystal, liquid + liquid + crystal, and solid crystal regions.     

Adhesion performance of PSA–clay nano-composites by the in-situ polymerization and mechanical blending

The synthesis and characterization of acrylic polymer/Na-montmorillonite (Na-MMT) clay nano-composites pressure sensitive adhesives (PSA) are researched. The PSA/clay nano-composites were synthesized by in-situ emulsion polymerization and mechanical blending. And then, different amounts of nanoclay were dispersed in 2-ethylhexyl acrylate (2-EHA)/n-butyl acrylate (BA)/methyl methacylate (MMA)/acrylic acid (AA) monomer mixture, which was synthesized using in-situ emulsion polymerization technique. Morphological observation was carried out using X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). Viscoelastic properties of PSA/clay nano-composites were analyzed using advanced rheometric expansion system (ARES). The adhesion performances of synthesized PSA/clay nano-composites were determined by measurements of peel strength, probe tack and shear adhesion failure temperature.     

A Viscometric Study of the Miscibility Behaviour of Poly(N-Vinyl Pyrrolidone) Blends

The miscibility behaviour of blends of poly(N-vinyl pyrrolidone) (PVP) with poly(vinyl chloride) (PVC), poly(vinyl acetate) (PVAc) and vinyl chloride–vinyl acetate (VCVAc) copolymer has been investigated on the basis of a viscometric approach. PVP is found to be miscible with PVC over the entire composition range, as is evident from the high values observed for the intrinsic viscosity of transfer. This is further supported by the single glass transition temperature observed in differential scanning calorimetry studies of the blend films. Blends of PVP with VCVAc copolymer exhibit microphase separation which is shown clearly in the scanning electron micrographs of the films. PVAc/PVP blends show interaction only at low PVAc contents, but in general are immiscible. © of SCI.