Oligomeric fluorinated additives as surface modifiers for solid polymers

Successful modification of the surface properties of solid polymers was obtained by the adsorption of appropriate partially fluorinated oligomers at polymer/air and polymer/substrate inter faces during the formation of these interfaces. These additives, in concentrations of 0.25 percent, effectively lowered the critical surface tension of wetting, γ_c, of such polymers as polystyrene, poly(methylmethacrylate), and poly(vinylidene chloride) copolymers by as much as 26 dyn/cm. The obtained low γ_c values of 14 dyn/cm correspond to surfaces containing closely packed CF₃ and CF₂ groups. Adhesion of additive-containing polymer films to various substrates was demonstrated to be a function of additive diffusion to the polymer/substrate interface, its subsequent adsorption and molecular orientation at that interface, and the surface energy of the substrate. The fluorinated additive molecules also have the advantage of being sufficiently mobile in the solidified polymer to reach and repair the interfaces.     

Hyperbranched aromatic polyesters: From synthesis to applications

During the last two decades, hyperbranched polymers have become the focus of interdisciplinary research, and received considerable attention due to their unique chemical and physical properties as well as their potential applications. As an important class of hyperbranched polymers, aromatic hyperbranched polyesters have attracted increased interest and are intensively studied because of their excellent thermal stability, chemical resistance, and mechanical properties. This article reviews the developments in synthesis, modifications, and applications of aromatic hyperbranched polyesters.     

Photocuring of cycloaliphatic epoxy formulations using polyesters with multiarm star topology as additives

Multiam star polyesters were synthesized by growing poly(ε‐caprolactone) (PCL) arms from hyperbranched polyesters cores of different molecular weight and used as polymeric modifiers in UV‐curable cationic formulations based on a biscycloaliphatic epoxy resin. The effect of the multiarm stars on the curing kinetics has been investigated by real‐time FTIR. The thermal‐mechanical properties of the photocured thermosets have been studied with calorimetry and dynamomechanical and thermogravimetric analysis. Impact strength tests have been performed to assess their effect on the toughness of the cured materials. An accelerative effect of these modifiers has been observed as a consequence of the participation of the hydroxyl groups of the modifiers in the cationic curing of the epoxy resin. A modest increase in toughness accompanied by a decrease in the glass transition are observed, as a consequence of the incorporation of the modifiers into the network structure, leading to homogeneous, in situ reinforced materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40005.     

Critical surface tension of blends of thermosetting fluorochemical methacrylate polymers with thermosetting hydrocarbon acrylate polymers

Critical surface tensions (γ_c) for blends of thermosetting fluorochemical methacrylates and thermosetting acrylate polymers are measured in their cured thermoset condition. Values of γ_c depend on (1) the nature of the fluorochemical side chain and (2) the ratio of fluorochemical containing polymer to hydrocarbon polymer. The minimum value for γ_c is found to occur at a fluorocarbon to hydrocarbon polymer ratio of 0.10 to 0.001. At higher and lower ratios (>0.1 and <0.001), the value for γ_c increased. Thus, certain blends of fluorochemical methacrylate copolymer with hydrocarbon acrylate copolymer give lower γ_c than either the hydrocarbon acrylate or the fluorochemical methacrylate copolymer.     

Marine paint fomulations: Conducting polymers as anticorrosive additives

Within coating technology, there is increasing interest in the development of efficient anticorrosive additives able to replace the conventional inorganic anticorrosive pigments usually added to paints, which may have detrimental effects on both environment and health. A number of recent studies have evidenced that the modification of a paint formulation by the addition of a low concentration of conducting polymer (0.2–0.3%, w/w) increases significantly the protective properties of the coating. Here we focus on the principles of anticorrosive additives based on conducting polymers for marine paints. The article reviews the most important findings achieved in recent studies. The relevant factors that are determinant for the anticorrosive protection imparted by conducting polymers, as the doping level, the miscibility with paint, the electrochemical stability, etc., are discussed in detail.     

The bending of polymers under tension as related to a deep drawing process

Two engineering plastics, an acrylonitrile-butadiene-styrene resin (ABS resin, Cycolac MS) and a rigid polyvinyl chloride resin (PVC resin, Dacovin 2082) were investigated to determine the effects of cold working. In particular, the “bending under tension” stress system of a deep drawing process was considered. The object was to determine the effect of the blank-holder pressure, the ratio of the punch radius to the material thickness, the speed of deformation and the temperature of deformation. The stress-strain characteristics of the deformed and undeformed material were markedly different. Upper yield points were lower in the deformed specimens, the tensile strengths were decreased by 10 to 15% and the %-elongation at break was higher—up to double the values for underformed specimens. An analysis indicated that these effects can be attributed to non-homogeneous yielding. The results also indicated that crazing plays an important role in permitting an ABS material to permanently conform to a radius with no geometric constraints.     

Liquid crystalline polymers as additives to enhance the device properties of low molecular mass liquid crystals

Magnetic and electric fields have been used to determine the splay (k₁₁) and bend (k₃₃) elastic constants in a series of polymer/monomer liquid crystal solutions using the well known Freedericksz transition technique. Measurements have been carried out as a function of concentration and temperature. The polymer used was a smectogenic polysiloxane side chain liquid crystal with both cyanobiphenyl and benzoate ester side groups. The monomeric solvent was the nematogen 4-n-pentyl-4′-cyanobiphenyl. All of the solutions studied were nematogenic up to a concentration of 40% w/w. It has been shown that k₁₁, k₃₃ and $\text{k}{}_{33}\text{k}{}_{11}$ all decrease with increasing polymer concentration and that at high enough concentrations $\text{k}{}_{33}\text{k}{}_{11}$ tends to become independent of temperature. The implications of these results are discussed in terms of the performance of the most common liquid crystal display, i.e. the twisted nematic device.     

Photoinduced tension of polymers

Photoirradiation of polymer films at constant length induced a fast tension reduction (time scale: seconds) followed by slow tension buildup (time scale: minutes). Immediately after irradiation, fast tension buildup was followed by slow tension decay. Cycles were repeatable without significant hysteresis loss. The amplitude of both phenomena are intensity-dependent in the ultraviolet–visible spectral regions; both phenomena are thermal rather than photochemical effects. Light-absorbing chromophores in the polymer structure, or in additives such as dyes, lead to absorption of light and internal conversion into heat. The classical, rapid thermal expansion (or contraction) on heating (or cooling) leads to the fast relaxation (or buildup) of tension. The elastic, entropic response of the sample with its longer relasation time leads to slow buildup (or decay) of tension. Fast and slow responses are observed sequentially with film of extensively crosslinked Riston photopolymer resist or with Kapton polymide film, whereas, in experiments with latex rubber, the rubbery behavior dominates.     

Migration of additives in polymers

The effects influencing the migration of different small molecular materials in polyethylene (PE) were studied. A decrease in weldability experienced after storage of the polymer at ambient and elevated temperatures was proved to be a result of migration of low molecular mass components of the polymer and some type of lubricants to the surface. Studies of different sorbitol fatty acid esters used as antifog agents in PE revealed that their mobility depends on the length of the hydrocarbon chain, while the antifog performance is influenced by the ratio of the OH groups to the hydrocarbon chain length.     

Surface properties of a segmented polyurethane containing amphiphilic polymers as additives

Two different types of amphiphilic polymers were used as surface-modifying additives to a polyetherurethane, Pellethane 2363–75D, which has T_g close to room temperature. The additives used were a segmented polyetherurethane designated Pol C, and Pluronics PE6800 and PE9400, i.e., triblock copolymers of propylene oxide and ethylene oxide. Pol C was prepared from poly(ethylene glycol), methylene diphenylene diisocyanate, and a fatty acid monoglyceride. The properties of the blends were investigated in their unhydrated state and after water immersion at 23°C and 80°C. Surface composition, water absorption, and leakage of additives to the aqueous phase have been studied. From ESCA and contact angle measurements it was concluded that Pol C was enriched in the surface layer of the matrix material after water immersion at 80°C. The Pluronics showed less effects on the surface properties of the matrix material, probably because of their high water solubility. © 1994 John Wiley & Sons, Inc.     

Hyperbranched polymers in cationic photopolymerization of epoxy systems

Mixtures of epoxy resins in the presence of epoxy hyperbranched polymers (HBP), in the range of 5–15 wt%, were investigated in the cationic photocuring process. No significant differences in rate of polymerization or final epoxy groups conversion were observed. At low concentration, HBP acts as plasticizer and causes a decrease of the glass transition temperature of the epoxy matrix and of the E′ value. At higher concentration (about 15 wt%), two T_g values are evident, indicating a biphasic structure of the system. The SEM analysis of the fracture surface of the samples confirms a particulate structure with separate HBP domains interconnected to the epoxy matrix. In all the samples investigated, a clear increase of the impact resistance was observed, resulting either from the plasticization effect or from the particulate structure induced by the presence of the HBP resin.     

Hyperbranched polyesters with carboxylic acid functional groups for the inhibition of the calcium carbonate scale

Scale deposits exist widely in industrial water‐cooling systems and oil‐production systems, causing severe damage to the equipment. The most effective way to prevent the formation of scale has been to use an inhibitor. The use of a hyperbranched polymer as an inhibitor, however, has rarely been reported. In this study, we prepared a hydroxyl‐terminated hyperbranched polyester (HBPE–OH) with trimethyloypropane as the core and 2,2‐bis(hydroxymethyl)propionic acid as an AB₂ monomer. The HBPE–OH was then modified with succinic anhydride to obtain the carboxyl‐terminated hyperbranched polyester (HBPE–COOH). The effects of the dosage, Ca²⁺ concentration, pH value, and temperature of the system on the inhibition efficiency were investigated when HBPE–COOH was used as an inhibitor of calcium carbonate (CaCO₃) scale. HBPE–COOH acted as a good antiscaling inhibitor for CaCO₃; when the polyester concentration was 200 mg/L, the scale inhibition rate exceeded 70%. Scanning electron microscopy and X‐ray powder diffraction demonstrated that the mechanism of inhibition was the disturbance of the growth of the crystals and modification of the crystal morphology by the hyperbranched polyester. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46292.     

Novel modified cellulosic polymers as drilling fluid additives with improved properties

Novel modified cellulosic polymers with amphoteric character were prepared by grafting 2-dimethylaminoethyl methacrylate (DM) and 4-vinylbenzene sulphonic acid sodium salt (VB) onto sodium carboxymethylcellulose (NaCMC), and characterized by IR and composition analyses. Their properties as drilling-fluid additives in oilfields were investigated with respect to shale inhibition, filtration control and viscosity enhancement. It is found that the grafting of DM enhances the shale-inhibition effectiveness and that the grafting of VB increases the tolerances to salt and temperature. Different from commonly used anionic and cationic polymeric additives, the modified cellulosic polymer with suitable structural parameters has both good shale-inhibition and mud properties. © 1999 Society of Chemical Industry     

Silicone polymers as foam control agents

Over the last decade, the European detergent industry has made tremendous strides to meet the everchanging demands of both consumers and regulatory bodies for improved detergent formulations. This has resulted in changes to almost every component of the traditional formulation, from the active system and the builder system to special nondetergent benefits. However, the magnitude of most of these improvements is dependent on effective foam control throughout the wash cycle, because European washing machines are lather intolerant. Optimum detergency can be achieved only when foam is controlled and the fabric is immersed in the wash liquor. In order to implement these formulation changes, the industry has sought improved foam control systems that are more effective than the traditional soap system. One such system is based on polydimethyl siloxane polymers. With proper formulation, these polymers provide performance over a wide temperature range and in a broad range of novel detergent formulations. Equally important is that they function at very low addition levels, thereby creating the formulation latitude for the inclusion of other wash active materials. The performance of these foam control agents in the detergent formulation is dependent on the method of incorporation. It is only with the advent of suitable processing techniques that such materials have become cost-effective ingredients in new European detergent formulations. Finally, they represent a safe alternative as exhaustive testing over the past 30 years has established these materials as essentially innocuous and free of any significant toxicity.     

Mobility of additives in ethylene polymers

Summary Diffusion rate of different additives was studied in ethylene polymers. The measured values were evaluated on the basis of the free-volume theory. It was concluded from the results that the rate of diffusion is primarily determined by the fractional free-volume of the noncrystalline phase of the polymer, as well as the specific volume of the additive.This work was supported by Grant No. OTKA 1/2-1790 from the National Scientific Research Foundation of Hungary.     

Aliphatic polyesters as models for relaxation processes in crystalline polymers: 1. Characterization

Syntheses and characterization of poly(pentamethylene pimelate), poly(1,6 hexamethylene adipate), poly(1,6 hexamethylene sebacate) and poly(2,5 hexamethylene adipate) are described. The first three are semicrystalline and the last completely amorphous. Dilatometry is used to establish volume-temperature curves (in both the solid and liquid regions in the first three). Liquid densities at 25°C are respectively 1104, 1096, 1033 and 1076 kg m^?3. Powder and fibre X-ray diffraction patterns on poly(pentamethylene pimelate) and poly(hexamethylene adipate) are indexed as monoclinic (a = 0.614, b = 0.737, c = 1.716 nm, β = 54.6°) and orthorhombic (a = 1.008, b = 0.732, c = 0.1683 nm), respectively. Under the assumption of 2 and 4 chains/cell, respectively, these lead to crystal densities of 1198 and 1222 kg m^?3, respectively, for these two polymers. The density of poly(1,6 hexamethylene sebacate) is known from the literature. Differential scanning calorimetry is used to establish crystal heats of fusion for the first three polymers as 151, 151, and 134 kJ kg^?1, respectively. The melting and crystallization temperatures of poly(1,6-hexamethylene adipate) are measured as a function of pressure up to 275 MPa. The heat of fusion derived from these data and the density data using the Clausius-Clapeyron equation is 167 kJ kg^?1.     

Hyperbranched polyesters with internal and exo‐presented hydrogen‐bond acidic sensor groups for surface acoustic wave sensors

Three hyperbranched aromatic polyesters carrying both internal and exo‐presented hydrogen‐bond acidic phenol, carboxylic acid, or mixed phenol/acetoxy groups were coated onto 500 MHz surface acoustic wave (SAW) sensor platforms, and sensor responses to the nerve agent simulant dimethyl methylphosphonate (DMMP) and the explosives simulant dinitrotoluene (DNT) were studied. All three hyperbranched polyesters gave strong responses to DMMP, and the hyperbranched polyester carrying carboxylic acid groups gave a particularly strong response. The hyperbranched polyester carrying phenol groups gave the best response to DNT of the three polymers studied. The DMMP and DNT responses of the three hyperbranched polyesters were also compared with hyperbranched SAW sensor polymers carrying exo‐presented phenolic sensor groups only, and also with linear SAW sensor polymers carrying phenolic sensor groups. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of catalyst on the reactive processing of polyesters with epoxy-functional polymers

The objective this work was to determine the effects of selected polyester catalysts on the reaction of a polyester with epoxy functional polymers. Polyesters containing various catalyst metals were melt blended with either an ethylene-co-glycidyl methacrylate or a styrene-co-glycidyl methacrylate copolymer. The viscosities of the blends were monitored as a function of mixing time using torque rheometry. In addition, the molecular weight distributions of selected samples were analyzed using gel permeation chromatography. Both the torque rheometry and the gel permeation chromatography results indicate that the polyester reacts with epoxy functional polymers. This reaction occurs under conditions and at processing times which are readily obtainable in conventional melt processing equipment. Furthermore, the reaction kinetics of polyesters with glycidyl methacrylate copolymers are dramatically affected by the nature of the catalyst system used to prepare the polyester. Under the conditions used, antimony catalysts are particularly effective at promoting the reaction between polyesters and the epoxy functionality and the activity of the catalysts studied appears to decrease in the following order: antimony > gallium > tin ? titanium > germanium. Manipulation of the polyester catalyst system may offer a method to control the extent of reaction obtained in reactive processing of polyesters with epoxy functional compounds.