Effect of trifunctional cross-linker triallyl isocyanurate (TAIC) on the surface morphology and viscoelasticity of the acrylic emulsion pressure-sensitive adhesives

Acrylic pressure sensitive adhesive (PSA) latexes were synthesized via a starved monomer-seeded semi-continuous emulsion polymerization process with butyl acrylate (BA), methyl methacrylate, acrylic acid (AA), 2-hydroxyethyl acrylate and trifunctional cross-linker, triallyl isocyanurate (TAIC). Influences of TAIC on the resultant latex and PSA properties were comprehensively investigated. The results indicated that latex particle size was independent of the amount of TAIC in the pre-emulsion feed, while the viscosity of the latex increased remarkably with TAIC content increased. Thermal gravimetric analysis result showed that the thermal stability of the polymers was improved significantly with the addition of TAIC. Besides, with the increase in TAIC content, gel content of the polymer increased significantly, while molecular weight between cross link points (M_c) and sol molecular weight (M_w, M_n) of the polymer decreased remarkably. Moreover, for the cross-linked adhesive film, the shear strength was improved greatly while at the sacrifice of loop tack and peel strength, when compared with the uncrosslinked counterparts. Finally, dynamic mechanical analysis and atomic force microscopy were also used to evaluate the viscoelastic properties and surface morphology of the acrylic emulsion PSA film, respectively.     

Synthesis and characterization of butyl acrylate/methyl methacrylate/glycidyl methacrylate latexes

The butyl acrylate (BA)/methyl methacrylate (MMA), and glycidyl methacrylate (GMA) composite copolymer latex was synthesized by seeded emulsion polymerization technique taking poly(methyl methacrylate) (PMMA) latex as the seed. Four series of experiments were carried out by varying the ratio of BA : MMA (w/w) (i.e. 3.1 : 1, 2.3 : 1, 1.8 : 1, and 1.5 : 1) and in each series GMA content was varied from 1 to 5% (w/w). The structural properties of the copolymer were analyzed by FTIR, ¹H‐, and ¹³C‐NMR. Morphological characterization was carried out using transmission electron microscopy (TEM). In all the experiments, monomer conversion was ～99% and final copolymer composition was similar to that of feed composition. The incorporation of GMA into the copolymer chain was confirmed by ¹³C‐NMR. The glass transition temperature (T_g) of the copolymer latex obtained from the differential scanning calorimetry (DSC) curve was comparable to the values calculated theoretically. With increase in GMA content, particles having core‐shell morphology were obtained, and there was a decrease in the particle size as we go from 2–5% (w/w) of GMA. The adhesive strength of the latexes was found to be dependent on the monomer composition. With increase in BA : MMA ratio, the tackiness of the film increased while with its decrease the hardness of the film increased. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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.     

Manipulation of chain transfer agent and cross-linker concentration to modify the performance of fluorinated acrylate latex pressure sensitive adhesive

Abstract

n-Dodecyl mercaptan (DDM) chain transfer agent and 1,6-hexanediol diacrylate (HDDA) cross-linker were used to manipulate latex properties in a monomer-starved seeded semi-continuous emulsion polymerization of butyl acrylate (BA), fluorine monomer dodecafluoroheptyl methacrylate (DFMA) together with acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA). The influences of both DDM and HDDA on the particle size of the latex, as well as on the gel content, thermostability (differential scanning calorimeter and thermal gravimetric analysis), surface properties (X-ray photoelectron spectra (XPS), contact angle analysis and atomic force microscopy), and viscoelasticity (N,N-dimethylacrylamide) of the polymer films were investigated. The results showed that the introduction of DDM and HDDA has no significant effects on the final particle size of the fluorinated pressure-sensitive adhesives (PSA) latexes. XPS analysis indicated that the fluoroalkyl groups had the tendency to enrich on the surface of the film. However, this enrichment of fluorine on the film surface was reduced after the introduction of HDDA, while increased with the addition of DDM. It was also found that the gel content, glass transition temperature (T_g), thermal stability, surface roughness, and modulus (G′, G?) of the fluorinated latex PSA were all increased with the introduction of HDDA. Nevertheless, opposite trends were observed for the latex after the addition of DDM. Finally, the effects of DDM and HDDA on the adhesive properties (i.e. loop tack, peel strength and shear strength) of the fluorinated latex PSA were also evaluated.     

In situ synthesis and properties of hydrogenated rosin/polyacrylate composite miniemulsions-based pressure sensitive adhesives

Hydrogenated rosin/polyacrylate composite miniemulsions-based pressure sensitive adhesives were synthesized by in situ miniemulsion polymerization method. The effect of HR amount on the monomer conversion rate, particle size and its polydispersity, coagulum rate, Zeta potential, and stability of the composite miniemulsions were studied, the effect of HR and crosslinker amount on the adhesion properties of the composite latex films were also investigated, and the composites were characterized by differential scanning calorimetry (DSC) and gel permeation chromatograph. The results showed that with HR amount increasing, the monomer conversion rate decreased, and the absolute value of Zeta potential and the molecular weight of the sol in the composite latex films also decreased, while the particle size and its polydispersity were almost unaffected. DSC analysis indicated that HR had relative good compatibility with polyacrylate. However, excess HR amount led to the decrease of the centrifugal stability and storage stability of the composite miniemulsions. Furthermore, with HR amount increasing, the ball tack of the latex films increased gradually, 180^o peel strength first increased and then decreased, and holding force decreased constantly. When HR amount exceeded 10 wt%, the failure style changed from interface failure to cohesion failure. The crosslinker CX-100 was helpful for the improvement of 180^o peel strength and holding force. When HR and CX-100 amount were 10 and 0.6 wt%, the ball tack, 180^o peel strength, and holding force were 9 #, 8.9 N/25 mm, and 178 h, respectively.     

Preparation and Adhesion Property of a Low Temperature Cross-Linkable Vinyl Acetate-Acrylate Copolymer Latex

The functional acrylate monomer (FAM) containing an amino group was synthesized by using glycidyl methacrylate (GMA) and ammonia. FAM was then copolymerized with Vinyl acetate and other acrylate monomers by emulsion copolymerization. The cross-linkable latex was obtained by adding a set content of glutaraldehyde to the earlier copolymer emulsion. The FT-IR results show that the cross-linking reaction between amino and aldehyde groups is detected during the curing process of copolymer. The glass transition temperature (T_g) of the copolymer can be evidently increased from ?16.2 to ?8.7°C as the FAM alters from 0 to 10%. T-peel strength of the polyethylene-polyethylene (PE-PE) packaging films laminated by products was studied. The results show peel strength dramatically increases with the cross-linking density at room temperature, and still reaches 2.5 N·15 mm^?1 even at 60°C, which can satisfy the application requirement enough.     

Synthesis,characterization, reactivity ratios by nuclear magnetic resonance spectroscopy,and application of (2,5‐Dichlorophenyl acrylate‐co‐glycidyl methacrylate) polymers as adhesives for the leather industry

2,5‐ Dichlorophenyl acrylate (DPA)‐co‐glycidyl methacrylate (GMA) polymers having five different compositions were synthesized in 1,4‐dioxane using benzoyl peroxide as a free‐radical initiator at 70 ± 0.5°C. Using ¹H‐NMR spectroscopy, the composition of the two monomers in the copolymers was calculated by comparing the integral values of the aromatic and aliphatic proton peaks. The reactivity ratios were calculated by Fineman–Ross (r₁ = 0.31 and r₂ = 1.08), Kelen–Tudos (r₁ = 0.40 and r₂ = 1.15), and extended Kelen–Tudos (r₁ = 0.39 and r₂ = 1.16) methods. The nonlinear error‐in‐variables model was used to compare the reactivity ratios. The copolymers were characterized by ¹H and proton decoupled ¹³C‐NMR spectroscopes. Gel permeation chromatography was performed for estimating the M_w and M_n and M_w/M_n of the poly(DPA) and copolymers (DPA‐co‐GMA: 09 : 91 and 50 : 50). Thermal stability of the homo‐ and copolymers was estimated using TGA [poly(DPA) > DPA‐co‐GMA (50 : 50) > DPA‐co‐GMA (09:91)], while DSC was utilized for determining the glass transition temperature. T_g increased with increased DPA content in the copolymer. The 50 : 50 mol % copolymer was chosen for curing with diethanolamine in chloroform. The cured resins were tested for the adhesive properties on leather at different temperatures (50, 90, 100, and 110°C). The resin cured at 50 °C exhibited a maximum peel strength of 1.6 N/mm, revealing a good adhesive behavior. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1167–1174, 2006     

Effect of propyleneimine external cross-linker on the properties of acrylate latex pressure sensitive adhesives

Acrylate pressure sensitive adhesive (PSA) latexes were synthesized via a starved monomer seeded semi-batch emulsion polymerization process with butyl acrylate (BA), methyl methacrylate (MMA), acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA). These PSA polymers were then cross-linked with trifunctional propyleneimine external cross-linker (SAC-100) to study the cross-linking reaction between carboxylic group of the polymer chain and cross-linking agent. It was found that cross-linking provided a significant influence on the film formation process based on the result of SEM analysis. In addition, with the increase of SAC-100 content, the gel content of the polymer increased significantly, while molecular weight between cross-link points (M_c) and the sol molecular weight (M_w, M_n) of the polymer decreased remarkably. The TGA result showed that the addition of the external cross-linker can enhance the thermal stability of the latex film. Moreover, for the cross-linked adhesive film, the shear strength was improved greatly while at the sacrifice of loop tack and peel strength, when compared with the uncross-linked counterparts. Besides, dynamic mechanical analysis (DMA) was also used to evaluate the viscoelastic properties of the acrylate emulsion PSA film.     

Modification research on the peel strength of the acrylate emulsion pressure‐sensitive adhesives

Pressure‐sensitive adhesives (PSAs) were produced with latexes synthesized via starved semibatch emulsion polymerization processes with butyl acrylate, three different kinds of hard monomers [styrene (St), methyl methacrylate, and 2‐phenoxy ethyl methacrylate (SR340)], acrylic acid, and 2‐hydroxy ethyl acrylate. The management of both the copolymer composition and the polymerization process allowed us to control the behavior of the PSAs. For the acrylate latexes, the types of hard monomers and their contents, the concentration of buffer [bicarbonate (NaHCO₃)], and three kinds of semibatch processes were manipulated to modify the polymer properties. The performance of the PSA films cast from these latexes was evaluated by the peel strength. The results show that the PSA prepared with St exhibited the highest peel strength among the three hard monomers, and the latex synthesized by SR340 showed the largest gel content compared with the other two hard monomers. With increasing buffer, the latex particle size increased, and the peel strength initially increased to a maximum and then decreased. Nevertheless, the stability of the latexes decreased with increasing buffer concentration. In addition, the effects of the three kinds of semibatch processes on the peel strength of the PSA were also evaluated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40095.     

Properties of UV-curable solvent-free pressure sensitive adhesive

In this study, the effects of methyl methacrylate (MMA), trimethylolpropane triacrylate (TMPTA), difunctional silicone urethane acrylate oligomer, and UV-dose on the adhesive properties of UV-curable pressure-sensitive adhesives (PSAs) were investigated, for further optimizing the adhesive properties to meet the requirements on high holding power and low peel strength. The results illustrated that increasing the MMA content decreased the peel strength and improved the holding power. The variation of TMPTA content from 1 to 10 wt% significantly enhanced the holding power from 1?h to above 120?h. The gel fraction increased with increasing TMPTA content. This increment was caused by the cross-linking of TMPTA after UV exposure. The peel strength of UV-curable PSAs was reduced to zero when oligomer content was more than 40 wt%, whereas the holding power was significantly enhanced from 5?h to above 120?h as the oligomer content increased up to 70 wt%. When the UV-dose increased, the peel strength decreased and the holding power increased. Therefore, UV-curable PSAs with very low peel strength and high holding power above 120?h were successfully synthesized and they possessed desirable features which could be fabricated to meet the specific requirements for industrial applications.     

Domain structure and miscibility studies of blends of styrene–butadiene–styrene block copolymers (SBS) and styrene–glycidyl methacrylate statistical copolymers (PS‐GMA) using SAXS and DMTA

The domain structure and miscibility in the solid state of a series of blends of styrene‐butadiene‐styrene (SBS) block copolymers and styrene‐glycidyl methacrylate (PS‐GMA) statistical copolymers with varying molecular weights and compositions were studied using small angle X‐ray scattering and dynamic mechanical thermal analysis. Depending on the molecular characteristics of each component, different types and degrees of solubilization of PS‐GMA in SBS were found which, in addition to the initially SBS phase morphology, lead to materials with multiphase domain morphologies with differences in size and structure. The degree of solubilization of PS‐GMA into the PS domains of SBS was found to be higher for blends containing PS‐GMA with lower molecular weight (M_w = 18 100 g mol^?1) and lower GMA content (1 wt%) and/or for SBS with higher PS content (39 wt%) and longer PS blocks (M_w = 19 600 g mol^?1). Localized solubilization of PS‐GMA in the middle of PS domains of SBS was found to be the most probable to occur for the systems under study, causing swelling of PS domains. However, uniform solubilization was also observed for SBS/PS‐GMA blends containing SBS with composition in the range of a morphological transition (PS block M_w = 19 600 g mol^?1 and 39 wt% of PS) causing a morphological transition in the SBS copolymer (cylinder to lamella). Copyright © 2006 Crown in the right of Canada. Published by John Wiley & Sons, Ltd     

Low corrosion optically clear adhesives for conducting glass: I. Effects of N,N‐diethylacrylamide and acrylic acid mixtures on optically clear adhesives

This study designs less corrosive optically clear adhesives (OCAs) with good rework properties, where copolymer and glycidyl methacrylate (GMA) are cured by ultraviolet to form OCAs. The copolymer are synthesized by using N,N‐diethylacrylamide (DMA), acrylic acid (AA), and 2‐ethylhexyl acrylate. The DMA and AA could form acid–base interaction and therefore lower the corrosion on metallic substrate caused by AA. Copolymer is applied in OCAs, as different adhesive properties are presented. In terms of the adhesive property of OCAs, the peel strength, shear strength, and transmittance property are decreased when the GMA concentration is increased. The tack and haze are enhanced accordingly. After 7 days' standing at 60 °C and 90% RH, OCAs have no obvious corrosion on the conductive glass circuits, and there is no residue after peeling off. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46277.     

Grafting of glycidyl methylacrylate onto chlorinated polypropylene and its bonding to aluminum flake

Glycidyl methacrylate (GMA) was grafted onto chlorinated polypropylene (CPP) in the molten state using benzoyl peroxide (BPO) in the presence of styrene (St) as a comonomer. The differential scanning calorimetry (DSC) results indicated that the thermodynamic curve of unpurified grafted CPP was different from the purified, and showed a new broad endothermic peak at 100°C, which may be attributed to the glass transition temperature (T_g) of remained copolymer of GMA and St. Furthermore, transmission electron microscope (TEM) showed that there were two‐phase structures in the grafted CPP. Because the grafted CPP was to be used as a hot melt adhesive, so the influence of initiator concentration, monomer concentration, and reaction temperature on peel strength was investigated. The experiment results showed that a higher degree of grafting was obtained by using two kinds of monomers, such as GMA and St. Increasing the monomer concentration led to an initial rapid increase in the peel strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2515–2521, 2007     

Poly(methyl acrylate-co-methyl methacrylate)/montmorillonite nanocomposites fabricated by soap-free emulsion polymerization

The exfoliated poly(methyl acrylate-co-methyl methacrylate)/montmorillonite (MMT) nanocomposite latex solutions fabricated by soap-free emulsion polymerization were able to cast into a film. The films were transparent and ductile unless more than 5 wt% of MMT was incorporated. With the MMT content higher than 5 wt%, the inflammable residuals of nanocomposites after combustion could preserve their original film profile acting like an inflammable scaffold. Moreover, as 20 wt% MMT was incorporated, the yield strength of the films was increased up to 20 times and Young’s modulus up to 2,000 times. However, the water vapor permeability coefficient of the films was only decreased down to its half value. This unexpected behavior of permeability was associated with the decrease of T _g as the content of MMT was increased, owing to the large difference of the reactivity ratios between methyl acrylate and methyl methacrylate monomers and their differential absorption to the MMT during copolymerization.     

Viscoelastic and adhesive properties of polystyrene-hydrogenated (3,4-polyisoprene and 1,4-polyisoprene)-polystyrene and polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate-based HMPSA

In the current study, hot melt pressure sensitive adhesives (HMPSA) were prepared by blending polystyrene-hydrogenated (3,4-polyisoprene and 1,4-polyisoprene)-polystyrene (HYBRAR7311), polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate (LA2250), tackifier, and other additives in an internal mixer. The compatibility of LA2250, HYBRAR7311, and glycerol rosin ester was investigated on the basis of transparency, differential scanning calorimeter, and scanning electron microscope. The results indicated that glycerol rosin ester was compatible with HYBRAR7311 and LA2250, while HYBRAR7311 was only partly compatible with LA2250. Besides, styrene-ethylene-butene-styrene block copolymers grafted MALEIC ANLYDRIDE was used as compatibilizer added into HMPSA. Although it increased the compatibility and shear strength yet the tack and peel strength were sharply decreased. Simple variable method was used to study the effect of main components on the tack, peel strength, and shear strength of HMPSA. The relationship between adhesive properties and viscoelastic properties of HMPSA was studied via dynamic mechanical analysis. The investigation showed that the smaller storage modulus at low frequency (0.01–0.1?1/s), the larger the tack. Peel strength was found proportional to G′′(f₁)/G′(f₂)(f₁?=?32.03?1/s, f₂?=?0.07?1/s). Similarly, the effect of this blend on damping performance and substrate on peel strength of HMPSA was investigated which was found excellent in this case. The peel strength of polypropylene was larger when HYBRAR7311 content was more than LA2250. However, the peel strength of polycarbonate and polyethylene glycol terephthalate was larger when LA2250 content was more than HYBRAR7311. Furthermore, the mechanical properties of HYBRAR7311/LA2250 HMPSA were found to be superior to the one-polymer HMPSA.     

Poly(glycidyl methacrylate‐co‐3‐thienyl‐methylmethacrylate) based working electrodes for hydrogen peroxide biosensing

BACKGROUND: Hydrogen peroxide biosensors based on Poly(glycidyl methacrylate‐co‐3‐thienylmethylmethacrylate)/ Polypyrrole [Poly(GMA‐co‐MTM)/PPy] composite film were reported. Poly(GMA‐co‐MTM) including various amounts of GMA and MTM monomers was synthesized via the radical polymerization. Enzyme horseradish peroxidase (HRP) was trapped in Poly(GMA‐co‐MTM)/PPy composites during the electropolymerization reaction between pyrrole and thiophene groups of MTM monomer, and chemically bonded via the epoxy groups of GMA. Analytical parameters of the fabricated electrodes were calculated and are discussed in terms of film electroactivity and mass transfer conditions of the composite films. RESULTS: The amount of electroactive HRP was found to be 1.25, 0.34 and 0.213 µg for the working electrodes of Poly(GMA_30%‐ co‐MTM_70%)/PPy/HRP, Poly(GMA_85%‐co‐MTM_15%)/PPy/HRP and Poly(GMA_90%‐co‐MTM_10%)/PPy/HRP, respectively. Optimal response of the fabricated electrodes was obtained at pH 7 and an operational potential of ? 0.35 V. It was observed that effective enzyme immobilization and electroactivity of the composite films could be changed by changing the ratios of GMA and MTM fractions of Poly(GMA‐co‐MTM) based working electrodes. CONCLUSION: The amount of electroactive enzyme increases with increasing MTM content of the final copolymer. High operational stabilities of the biosensors can be attributed to the strong covalent enzyme linkage via the epoxy groups of GMA due to preventing enzyme deterioration and loss. A more convenient microenvironment for mass transfer was provided for the electrodes by higher GMA ratios. It is observed that mass transfer is dominated by the mechanism of electron transfer to obtain effective sensitivity values. This work contributes to discussions clarifying the problems regarding the design parameters of biosensors. Copyright © 2011 Society of Chemical Industry     

Effect of polyurethane molecular weight on the properties of polyurethane–poly(butyl methacrylate) hybrid latex prepared by miniemulsion polymerization

Polyurethane (PU) prepolymer was first prepared via introducing double bonds on‐to the PU chains, and then polyurethane–poly (butyl methacrylate) (PU–PBMA) hybrid latex was prepared via miniemulsion polymerization. Transmission electron microscopy, Differential scanning calorimeter (DSC), Fourier transform infrared, and dynamic mechanical analysis were adopted to characterize the hybrid latex and its coating film. Both the coating property and the miscibility of PU–PBMA emulsion have been greatly improved through introducing double bonds into PU prepolymer. With an increase in the molecule weight of PU (M_PU), the increase in the particle size of PU–PBMA emulsion was observed plus decreases in the stability of the hybrid latex and conversion of methacrylate. Besides, as M_PU increased, the final dried coating film of the hybrid latex showed decreased water resistance, weakened miscibility, and improved mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of glycidyl methacrylate content and addition sequence on the acrylic latexes with carboxyl groups

Acrylic latexes with epoxy and carboxyl groups have been synthesized via a two-stage emulsion polymerization process. Different contents of glycidyl methacrylate (GMA) were introduced by three addition modes to copolymerize with methyl methacrylate, butyl acrylate, acrylic acid (AA) in the presence of K₂S₂O₈. To obtain stable latexes, NaHCO₃ was employed as a buffer to compensate for the acidity from the thermal dissociation of K₂S₂O₈, and triethylamine was used to neutralize the carboxyl acid from AA. The results showed that the stable latexes with core/shell structure were synthesized by this method, and higher GMA content or addition at earlier stage led to forming the latexes with higher content of coagulum and bigger sized particles. During the formation of films, the polymer epoxy groups underwent the crosslinking reaction with carboxyl acid. When the GMA content increased or GMA was introduced at a later stage, high crosslinking extent was formed in the films. As a result, the crosslinking provided the films with improved water resistance, chemical resistance, tensile strength, hardness, abrasion resistance, and thermal stability.     

Miniemulsion vs. conventional emulsion polymerization for pressure-sensitive adhesives production

A systematic study of the production of poly(2-ethyl hexyl acrylate/methyl methacrylate/acrylic acid) pressure-sensitive adhesives (PSAs) via conventional emulsion and miniemulsion polymerization was carried out in order to discern and compare the influence of copolymer composition, chain transfer agent (CTA) and surfactant concentrations on the kinetics and microstructure of the resulting adhesive films. The results showed that miniemulsion polymerization proceeded solely under droplet nucleation for a certain set of initial reaction conditions. The miniemulsion-based latexes presented a polymer microstructure that was different to that found in latexes produced by conventional emulsion polymerization, as observed in the frequency master curves and PSA performance analysis. Batch miniemulsion polymerization was able to produce films with entanglement densities (M_w/M_e) from 2 up to 11, which were strongly correlated with loop tack, peel strength and shear strength. Conversely, under the same reaction conditions, batch conventional emulsion polymerization was only able to produce M_w/M_e ratios below 2.     

High breakdown strength and low loss of polystyrene-block-poly(methyl methacrylate)/Poly(vinylidene fluoride) composites for energy storage application

Poly(vinylidene fluoride) (PVDF) composite films were prepared by introducing polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) into PVDF matrix. Uniform dispersion and good compatibility of PS-b-PMMA in matrix were observed, which was helpful for high breakdown strength (E_b). The composite film with 9 wt% PS-b-PMMA showed the maximum E_b of 522 kV/mm and the high discharged energy density (U_e) of 10.1 J/cm³, which were 1.7 times and 2.6 times higher than pure PVDF, respectively. Besides, a charged-discharged efficiency (η) of 88% was much higher than pure PVDF at 300 kV/mm, which was beneficial to energy storage.