Patent Application
20100160484
The present invention relates to a composition of matter for increasing the flexibility and durability of crystalline or semi-crystalline resins and polymers. In particular, the invention pertains to the plasticizing effect of xanthene-based molecular structures on curable resins or thermosetting polymers when incorporated into the polymer material.
The morphology of polymer molecules and ways that molecules are arranged in a solid are important factors in determining the properties of materials. From polymers that crumble to the touch because of their rigid or brittleness to those that exhibit good elastomeric properties, the molecular structure, conformation and orientation of polymers can have a major effect on the macroscopic properties of the material. The general concept of self-assembly enters into the organization of molecules on the micro and macroscopic scale as they aggregate into more ordered structures. Crystallization is an example of the self-assembly process, as is the organizational orientation of liquid crystals.
Conventional thermoplastic polymers, curable or thermosetting polymer resins and films, such as polypropylene, cyanoacrylates, or polystyrene, tend to be relatively and brittle. Manufacturers have over the years tried to develop or modify conventional thermoplastic materials to make them more pliable or “softer,” but few have had success. This need for a new material composition or method to modify the polymeric materials to increase their relative plasticity remains unsatisfied. The present invention provides a plasticizer composition to address this need.
The present invention pertains to a curable composition of matter having a semi-crystalline polymer and a compound with a xanthene-based molecular structure. The polymer has a minimal crystalline content of about 40% to about 55% by weight of the polymer. The compound with a xanthene-based molecular structure is present in an amount of up to about 4% or 5%. The composition exhibits a ratio in a range from about 1.3:1.8:1.0 to about 1.6:1.5:1.0, respectively of a mesophase: crystalline phase: amorphous phase when cured. It is believed that the xanthene molecular structure exhibits a major effect that inhibits the formation of crystalline solid or semi-crystalline mesomorphic state, which increases the amorphous nature of the solidified polymer. In other words, it contributes to a manifestation of classic plasticizer properties with a relatively higher percentage of an amorphous state. The presence of xanthene-based molecular structures can reduce the relative rigidity and brittleness of a piece of polymer substrate, and imparts a greater flexibility or pliability.
In another aspect, the invention pertains to a method of plasticizing a crystalline-phase-containing polymer. The method involves providing in a mixture a polymer with about 30% to about 70% crystallnlnity and a plasticizing agent having a xanthene-based molecular structure present in an amount of up to about 5 wt. %, but typically about 0.1 wt. % to about 2.2 wt. %, of total composition; agitating and heating the mixture to a temperature of up to about 95° C. or 100° C.; and then allowing the mixture to cool to about ambient room temperature. Depending on the nature of the polymer (e.g., melting or curing point), the mixture may be heated to a temperature between about 50° C. or 60° C. and about 70° C. or 85° C. The polymer initially can have a mesophase of about 50% or less.
The present invention also pertains to a flexible barrier coating for mammalian skin. The coating includes a crystalline or semi-crystalline polymer and a plasticizing agent having a xanthene molecular structure. The barrier coating exhibits a modulus of about 1.8×108 Pa to about 5.5×108 Pa. Such physical properties are beneficial when developing a coating for surfaces that tend to bend or flex, such as the skin of animals, in particular, mammalian skin to which product like a skin sealant is applied.
More typically, the coating has a modulus of about 2×108 Pa to about 4×108 Pa. Human test subjects reported a noticeable difference between the feel of a skin sealant containing a conventional cyanoacrylate composition and one containing the present modified formulation. The difference in tightness or clinging against the skin is measurable reduction in the degree to which the coating cracked and flaked during use.
In general, the present invention pertains to thermoplastic polymer compositions that are modified with a plasticizing compound containing a xanthene or xanthene-based molecular structure.
As used herein, the term “curable polymer” or “thermosetting material” refers to an organic macromolecule composed of a large number of monomers, the monomers have molecular weight that may range from about 95 daltons to about 150,000 or 200,000 daltons, which softens when exposed to heat and returns to its original condition when cooled to room temperature, such as cyanoacrylates.
As used herein, a “plasticizer,” “plasticizing agent,” or “plasticizing compound” is an organic compound that is added to a curable resin monomer—which when cured forms a relatively high molecular weight polymer (i.e., ≧500 daltons, up to about 100,000 daltons), which can both facilitate processing and increase the flexibility of the final product by modifying the molecular bonds of the polymer. Typically, the polymer molecule is held together by secondary valence bonds. The plasticizer replaces some of these bonds with plasticizer-to-polymer bonds, thus aiding movement of the polymer chain segments.
As used herein, a “xanthene” or “xanthene-based” molecule refers to an unmodified xanthene molecule or a derivative compound with a xanthene ring structure, as shown below. Xanthene (CH2(C0H4)2O) (dibezopyran, tricyclic), a yellow organic heterocyclic compound, has the following chemical structure:
It is soluble in ether, and its melting point is 101-102° C. and its boiling point is 310-312° C. Xanthene is commonly used as a fungicide and is also a useful intermediate in organic synthesis. The xanthene molecule can be halogenated. Halogenated xanthene structures may include, for example, mono-bromo, di-bromo, tri-bromo, or tetra-bromo-fluorosceins; mono-fluoro, di-fluoro, tri-fluoro, or tetra-fluoro-fluorosceins; mono-iodo, di-iodo, tri-iodo, or tetra-iodo-fluorosceins; mono-chloro, di-chloro, tri-chloro, tetra-chloro-fluoroscein, and mixtures thereof. Additionally, mixed halogenated xanthenes structures such as tetra-bromo-tetra-chloro-xanthene (e.g., Drug and Cosmetic Red No. 27), are also contemplated.
Although some polymers may be completely amorphous, the morphology of most polymers is semi-crystalline. That is, they form a combination of crystalline and amorphous portions with the amorphous regions surrounding the crystalline areas. The mixtures of small crystals and amorphous material melt over a range of temperature instead of at a single melting point. The crystalline material tends to have highly ordered and regular structures formed by folding and stacking of the polymer chains. The amorphous structure, in contrast, shows no long range order, and have molecular chains are arranged randomly and in long chains which twist and curve around one-another, making large regions of highly structured morphology unlikely.
The highly ordered crystalline structure and amorphous morphology of certain polymer materials determine the differing behaviors of the polymer. An amorphous solid is formed when the chains have little orientation throughout the bulk polymer. The glass transition temperature (Tg) is the point at which the polymer hardens into an amorphous solid. The glass transition temperature of a polymer is an important factor in its physical properties and behavior for certain desired uses. As the temperature of a polymer drops below its Tg, the polymer behaves in an increasingly brittle manner; while, as the temperature rises above the Tg, the polymer becomes more viscous-like. In general, polymers with Tg values of well below room temperature (˜20° C.) define the domain of elastomers, and those with values above room temperature define rigid, structural polymers.
The Tg can influence the mechanical properties of the polymeric material; in particular, the response of the material to an application of a force, namely: elastic and plastic behaviors. Elastic materials will return to their original shape once the force is removed. Plastic materials will deform fluidly and not regain their shape. In plastic materials, flow is occurring, much like a highly viscous liquid. Most materials demonstrate a combination of elastic and plastic behavior, exhibiting plastic behavior after the elastic limit has been exceeded. For example, polyvinyl chloride (PVC) has a Tg of 83° C. making it good, for example, for cold water pipes, but unsuitable for hot water. PVC also will always be a brittle solid at room temperature. Adding a small amount of plasticizer to PVC can lower the Tg to about −40° C. This addition renders the PVC a soft, flexible material at room temperature, ideal for applications such as garden hoses. A plasticized PVC hose can, however, become stiff and brittle in winter. In this case, as in any other, the relation of the Tg to the ambient temperature is what determines the choice of a given material in a particular application.
In the crystallization process, it has been observed that relatively short chains organize themselves into crystalline structures more readily than longer molecules. Therefore, the degree of polymerization (DP) is an important factor in determining the crystallinity of a polymer. Polymers with a high DP have difficulty organizing into layers because they tend to become tangled. Low molecular weight polymers (short chains) are generally weaker in strength. Although they are crystalline, only weak Van der Waals forces hold the lattice together. This allows the crystalline layers to slip past one another causing a break in the material. High DP (amorphous) polymers, however, have greater strength because the molecules become tangled between layers. In the case of fibers, stretching to 3 or more times their original length when in a semi-crystalline state produces increased chain alignment, crystallinity and strength.
Also influencing the polymer morphology is the size and shape of the monomers' substituent groups. If the monomers are large and irregular, it is difficult for the polymer chains to arrange themselves in an ordered manner, resulting in a more amorphous solid. Likewise, smaller monomers, and monomers that have a very regular structure (e.g. rod-like) will form more crystalline polymers.
The cooling rate also influences the amount of crystallinity. Slow cooling provides time for greater amounts of crystallization to occur. Fast rates, on the other hand, such as rapid quenches, yield highly amorphous materials. Subsequent annealing (heating and holding at an appropriate temperature below the crystalline melting point, followed by slow cooling) will produce a significant increase in crystallinity in most polymers, as well as relieving stresses.
In most polymers, the combination of crystalline and amorphous structures forms a material with advantageous properties of strength and stiffness. According to the present invention, while in furtherance of the work described in U.S. patent applications Ser. Nos. 11/974,369, and No. 11/974,393, the content of which are incorporated herein by reference, we have discovered that xanthene or xanthene-based compounds can impart significant plasticizing properties to a variety of crystalline or semi-crystalline in curable resins or polymer materials with a crystalline level of more than about 5% or 7%. Examples of suitable xanthene-based compounds include xanthene dyes (e.g., xanthene base structure of fluorescein systems). Xanthene dyes are a class of dyes which includes fluoresceins, eosins, and rhodamines. They fall into three major categories: the fluorenes or amino xanthenes, the rhodols or aminohydroxyxanthenes, and the fluorones or hydroxyxanthenes. Lillie, H. J. C
Nonetheless, according to the present invention, not all xanthene-based structures function well as a plasticizer. We have found that xanthenes-based compounds with ketone or carboxylic acid analogues (e.g., xanthone and xanthene-carboxylic acid) do not work as well as others since they appear not to impart good plasticizing characteristics, but rather can make the polymer material very brittle, even worse than a control sample of the original polymer material.
The present invention can be adapted for use with a variety of semi-crystalline resins and polymers. The present xanthenes-based plasticizer can function well to modify the modulus of curable polymers that have relatively small monomer units with a molecular mass of up to about 95,000 or 10,000 atomic mass units (daltons). The monomer units can have a molecular mass of as low as about 95 or 100 daltons. More particularly, the monomer units may range in mass from about 200 or 300 daltons to about 85,000 or 90,000 daltons (±200-500 daltons). Typically, the monomer unit are about 500 daltons to about 70,000 daltons inclusive (e.g., ˜750-60,000 daltons, 900-50,000 daltons, or desirably about 1,000 to about 30,000 daltons). More typically, the monomer molecule may be in a mass range from about 2,000 or 5,000 daltons to about 17,000 or 20,000 daltons.
The present invention relates to a curable composition of matter comprising a semi-crystalline polymer with a minimal crystalline content of about 40% to about 55% by weight of the polymer, and a compound with a xanthene-based molecular structure in an amount of less than 2%. The composition exhibits a ratio of about 1.3:1.8:1.0 to about 1.6:1.5:1.0, respective of a mesophase:crystalline phase:amorphous phase when cured. In certain embodiments, the curable composition exhibits a ratio of about 1.45:1.64:1.0, respective of said mesophase:crystalline phase:amorphous phase when cured. The polymer contains a crystalline content of about 35% to about 45% crystalline phase, 35% to about 45% mesophase, about 23% to about 27% amorphous state. The mesophase and said crystalline phase are each reduced by an amount of about 10-50% relative to the percentage of mesophase and crystalline phase of an identical composition absent the compound with xanthene-based molecular structure.
The compound with a xanthene-based molecular structure is present in the polymer matrix in an amount of about 0.01 wt. % up to about 2.0 wt. %. Typically, xanthene molecules or compounds with a xanthenies-based molecular structure are present from about 0.03 or 0.04 wt. % up to about 1.7 or 1.8 wt. %. More typically, the compound with a xanthene-based molecular structure is present at about 500 ppm (0.05 wt. %) to about 5000 ppm (0.5 wt. %). The semi-crystalline polymer has a vinylic functionalized monomer selected from: acrylate, cyanoacrylate, methacrylate, or styrene. In particular embodiments, the semi-crystalline polymer is a copolymer derived from one or more cyanoacrylate monomers or a blend of cyanoacrylate monomers. The cyanoacrylate can be an alkyl cyanoacrylate, wherein the alkyl group includes an ethyl, butyl, or propyl group. More specifically, the cyanoacrylate monomers may be selected from alkyl 2-cyanoacrylate, alkenyl 2-cyanoacrylate, alkoxyalkyl 2-cyanoacrylate, or carbalkoxyalkyl 2-cyanoacrylate, wherein the alkyl group may have 1 to 16 carbon atoms and may be methyl 2-cyanoacrylate, ethyl 2-cyanoacrylate, n-propyl 2-cyanoacrylate, iso-propyl 2-cyanoacrylate, n-butyl 2-cyanoacrylate, iso-butyl 2-cyanoacrylate, hexyl 2-cyanoacrylate, n-octyl 2-cyanoacrylate, 2-octyl 2-cyanoacrylate, 2-methoxyethyl 2-cyanoacrylate, 2-ethoxyethyl 2-cyanoacrylate and 2-propoxyethyl 2-cyanoacrylate.
The composition can be adapted to form a flexible barrier coating for a skin sealant. For example, the composition can be formed into a film with about 1 mm (±0.05 mm) thickness and cured, said composition exhibits, at a stress of 50,000 g/cm2, a deformation of at least 40% greater than an identical composition absent said compound with xanthene-based molecular structure.
According to an alternate embodiment, the invention can be an article of manufacture comprising curable polymers or thermoplastics. The curable polymer has a semi-crystalline polymer matrix incorporating a plasticizer composed of at least a xanthene molecule or a compound with a xanthene-based molecular structure, which can be present at about 500 ppm (0.05 wt. %) to about 5000 ppm (0.5 wt. %). In certain examples, the semi-crystalline polymer is a vinylic functionalized monomer selected from: acrylate, cyanoacrylate, methacrylate, or styrene. The semi-crystalline polymer can be a copolymer derived from one or more cyanoacrylate monomers or a blend of cyanoacrylate monomers, wherein the cyanoacrylate monomers are selected from alkyl 2-cyanoacrylate, alkenyl 2-cyanoacrylate, alkoxyalkyl 2-cyanoacrylate, or carbalkoxyalkyl 2-cyanoacrylate, wherein the alkyl group may have 1 to 16 carbon atoms and may be methyl 2-cyanoacrylate, ethyl 2-cyanoacrylate, n-propyl 2-cyanoacrylate, iso-propyl 2-cyanoacrylate, n-butyl 2-cyanoacrylate, iso-butyl 2-cyanoacrylate, hexyl 2-cyanoacrylate, n-octyl 2-cyanoacrylate, 2-octyl 2-cyanoacrylate, 2-methoxyethyl 2-cyanoacrylate, 2-ethoxyethyl 2-cyanoacrylate and 2-propoxyethyl 2-cyanoacrylate.
According to another aspect, the invention discloses a method of plasticizing a crystalline-phase-containing polymer. The method comprises: providing in a mixture a polymer with about 30% to about 70% crystallinity and a plasticizing agent having a xanthene-based molecular structure present in an amount of up to about 2.2 wt % or 2.4 wt %, more typically up to about 1.75 or 1.8 wt. %, of total composition; agitating and heating said mixture to a temperature of up to about 85° C.; and then allowing the mixture to cool to about ambient room temperature. Typically, the mixture is heated to a temperature of between about 50° C. and 80° C. (e.g., about 60° C. or 70° C.). Structurally, the polymer should contain a mesophase of greater than 33% or 35% of the polymer matrix. In certain curable polymner materials the mesophase can be between about 37% or 40% up to about 55% or 60% or 75%.
In yet another aspect, the present invention can be adapted to create a flexible barrier coating that can be applied to mammalian skin without the shortcomings of conventional films, such as cracking and spalling of an inelastic dried film layer when subjected to skin movement. The present barrier coating includes a crystalline or semi-crystalline polymer and a plasticizing agent having a xanthlene molecular structure, said barrier coating exhibiting a modulus of about 1.8×108 Pa to about 5.5×108 Pa. Typically, the flexible barrier coating has a modulus of about 2×108 Pa to about 4×108 Pa.
The present plasticizer material can be incorporated into the formulation of a variety of products that contain alkyl-cyanoacrylates, with an alkyl chain ranging from C2 to C12.
A. Methyl and butyl-cyanoacrylates
As illustrated in the accompanying figures, curable resins, such as methacrylates or epoxy materials, which are modified with pure xanthene or halogenated xanthene molecules exhibit relatively good resistance to stress-strain, behavior. Strain of a polymer sample is expressed as a percentage (x %) of a sample's original length dimension. The polymer sample modified with xanthene can withstand nearly twice the amount of strain as that experience by a control resin sample before it fractured. In other words, if the control sample is able to withstand up to about 5% or 6% strain before breaking, the xanthene-doped polymer sample is able to withstand up to about 10% to 12% strain before tearing. In contrast, curable polymer materials that are doped with ketone and carboxylic acid analogues of xanthene (i.e., xanthone, xanthenic acid) appear not to exhibit a similar enhanced plasticizing effect. A polymer sample incorporating xanthone molecules is only slightly better than the control sample in being able to adapt to a strain load before breaking. Moreover, the polymer sample incorporating xanthenic acid molecules become too brittle even to remove from the surface of a mold.
In certain examples, the polymer is an alkyl cyanoacrylate selected from a group including, for example alkyl 2-cyanoacrylate, alkenyl 2-cyanoacrylate, alkoxyalkyl 2-cyanoacrylate, and carbalkoxyalkyl 2-cyanoacrylate. The cyanoacrylates also may be selected from, for instance, methyl 2-cyanoacrylate, ethyl 2-cyanoacrylate, n-propyl 2-cyanoacrylate, iso-propyl 2-cyanoacrylate, n-butyl 2-cyanoacrylate, iso-butyl 2-cyanoacrylate, hexyl 2-cyanoacrylate, n-octyl 2-cyanoacrylate, 2-octyl 2-cyanoacrylate, 2-methoxyethyl 2-cyanoacrylate, 2-ethoxyethyl 2-cyanoacrylate and 2-propoxyethyl 2-cyanoacrylate. The alkyl group of the cyanoacrylate has 1 to 16 carbon atoms. More desirably the alkyl group has 1 to 6 or 8 carbons. It is observed that unmodified xanthene molecules can reduce the relative melting point for both the crystalline phase and mesophase of the polymer, which results in an extension of the plasticizing effect.
B. Skin Study and Elastic Modulus of Skin
An application of the present invention can be in the healthcare or medical arena. In recent years, coatings containing cyanoacrylates have been developed to help reduce the incidence of surgical site infections. The coating is applied to a clean area of a patient's skin to immobilize microbes that may be present before the surgeon makes an incision through the coated area. An example of a composition for such a coating or a skin sealant is detailed in Table 1, below. Unfortunately, because of the rigid nature of cyanoacrylate films, the skin sealant tends typically to become inflexible and brittle when dried on the patient's skin. When encountering the natural bending and flexing of the body, the brittleness of the coating causes the coating to easily crack and spall off.
An unexpected benefit of incorporating xanthenes dyes, which provide a colorant that would allow visual indication to a user for both coverage and cure of the skin sealant, is that, when cured the cyanoacrylate film exhibited a greater degree of flexibility than an identical cyanoacrylate composition absent the xanthene dye. The greater flexibility of the polymer film leads to reduced cracking and flaking of the cured skin sealant.
In particular embodiments, the plasticizer may be incorporated in a polymeric skin sealant for surgical or other applications. An example of such a sealant is I
I
In clinical trials, human volunteers had a coating of I
The visco-elastic properties of human skin have been reported in the literature. It is a difficult system to measure due to the property is due to a combination of the components of human skin (collagen, elastin and ground substances). Results indicate that maximum thickness of human skin is reached when an individual is around the age of 40 years. Standardized skin extensibility decreases with age and has to be considered in relation to the total water content. The literature has several studies to determine the elastic modulus of human skin; the values obtained cover a range which was attributed to the particular method of analysis used. Of specific interest was the method of Graham and Holtz which obtained a value of 1.8×107 Pa (Pascal). The current I
Using 4,5-dibromofluorescein (Aldrich Chemical Co., Milwaukee Wis.) dissolved into an I
X-ray diffraction (XRD) results show that the dry I
The incorporation of a xanthene-based structure in the normally rigid polymer matrix increased by at least 10% the amount of amorphous content in the polymer. The plasticizing agent also decreases the relative amount of mesomorphic state in the polymer, in which a significant fraction of has a molecular arrangement intermediate between crystalline solid and amorphous phases, which under X-ray diffraction analysis appears like “liquid crystals.”
This section describes the experiments to investigate xanthene compounds to determine the role of the substituents and the structure itself plays on this plasticizer effect.
Alkyl cyanoacrylates [R(COR′)C═CH2] where the alkyl group is between C1 to C12. Monomer molecular weights (MW) range from about 86 to about 192.
Alkyl cyanoacrylates are used as “Superglue” (ethyl and methyl cyanoacrylates), skin sealants (butyl cyanoacrylates), and surgical suture and organ repair adhesives (octyl cyanoacrylates).
Alkyl cyanoacrylates cure to become solids quite efficiently resulting in a solid substance with very high molecular weight where all the monomer is polymerized/crosslinked. The final molecular weight of the cured substance depends on the amount of monomer used or present at the beginning, therefore it is difficult to give a final molecular weight as it depends on the amount of monomer used.
The samples were analyzed on a TA Instruments DSC 2920 Modulated DSC (Standard Cell) using the following experimental procedure: Approximately 5 mg, cut from a random place of the respective materials, were run in the temperature interval −125° C. to 220° C. with a heating/cooling rate of 10° C./min in an inert gas (N2) atmosphere.
The film samples were analyzed on an X-ray diffractometer D-max Rapid from Rigaku Corp. equipped with a two dimensional (2-D) position sensitive detector. The measurements were executed in transmission geometry and Cu Kα radiation (λ=1.5405 Angstrom). The results were corrected for background and air scattering.
The film samples with thicknesses in the range 30μ-60μ were analyzed on a Rheometrix Solids Analyzer DMTA V. The measurements were executed at room temperature in a frequency sweep mode (1 Hz to 10 Hz) by increasing the loads until the failure of the materials.
Samples are analyzed using X-ray diffraction, and exhibited three large intensity peaks representing the three phases of the polymer material. A crystalline phase is represented by an intensity peak between about 17-20, an amorphous phase is represented by a peak in the range of about 10-17, and a mesophase is a peak in a range of about 4-8.
Comparison of the accompanying X-ray diffraction curves for an experimental polymer sample and a control sample containing the xanthenes-based plasticizing agent shows that the amorphous concentration increases from an original intensity of about 4-6 counts in the control to about double at 10-12 counts in the experimental sample. Correspondingly, incorporation of a xanthene-based compound in the polymer results in a decrease of the mesophase content by about 5-7 or 10 units. The crystalline phase and mesophase of the polymer each is reduced by about 20%, 22%, or 25% up to about 45% or 50%. The X-ray diffraction intensity of the crystalline phase is reduced by about 3,000 to about 5,000 counts and mesophase by about 6,000 to about 10,000 counts.
An inspection of
TABLE 2 summarizes the ratios of the intensities of the mesomorphic peaks divided by the intensities of the respective amorphous halos.
From Table 2, one can see that the clear material (Sample 1-1) and the material containing violet pigment (Sample 1-4) are characterized with ratios larger than 1, while the materials containing the pigment Orange 5 exhibit ratios less than 1. This is an indication that the materials containing the Orange 5 additive exhibit a lower mesophase content in comparison to Samples 1-1 and 1-4.
To investigate the possible effect of the mesophase content on the mechanical properties of the materials DMA tests were performed. In
Curable polymer resins in a liquid form are spread on microscopic slides. After drying at room temperature, the resulting films were removed with razor blade. Sample 2-3 was very brittle and developed small cracks in the process of removal from the microscopic slide; hence, DMA tests on Sample 3-3 were unsuccessful.
Using a DMA instrument, specimens are tested to ascertain the effect of additives on the mechanical response of I
To obtain a better understanding of the differences in the phase structures of the I
When dry, the I
A comparison of the XRD and DMA results shows that a correlation between the mesophase content and the mechanical response. The polymer materials containing the highest levels of mesophase are more brittle than the specimens containing xanthene-based molecular structures. The results show that a polymer having a crystallinity content of 45%, such as a cyanoacrylate polymer solid by itself or containing violet 2 exhibited the most brittle physical properties—highest dynamic modulus and shortest amount of elongation at break. Conversely, a cyanoacrylate solid containing 4′,5′-dibromofluorescein (DBF) exhibits the most ductile behavior—lowest dynamic modulus and greatest amount of elongation at break; hence, 4,5′-dibromofluorescein is a strong plasticizer of cyanoacrylate formulations.
Xanthene show good plasticizing properties in various kinds of cyanoacrylate resins.
We blended dichlorofluorescein into a commercial superglue formulation (Krazy glue, Elmer's Products Inc. Columbus Ohio). A 5000 ppm of a dichloro-fluorescein compound is mixed into the superglue and the properties of the cured films are compared to control films of the base polymer formulation.
The superglue films exhibited higher stress-strain tolerances than the I
Ten 1-gram samples of superglue (Krazyglue, Elmer's Products, Inc., Columbus Ohio) containing ethyl cyanoacrylate are prepared. Test and control samples, respectively, with and without dichloroflurescein in the formulation were cured on microscope slides. Dichloroflurescein was present in the test samples at a concentration of 5000 ppm. The xanthenes dye-containing samples are observed to be relatively more flexible (i.e., plasticized) when compared to control samples. It appears that the alkyl group has no effect on the ability of the xanthenes to plasticize alkyl cyanoacrylates.
The present invention has been described both generally and in detail by way of examples and the figures. Persons skilled in the art, however, can appreciate that the invention is not limited necessarily to the embodiments specifically disclosed, but that substitutions, modifications, and variations may be made to the present invention and its uses without departing from the spirit and scope of the invention. Therefore, changes should be construed as included herein unless the modifications otherwise depart from the scope of the present invention as defined in the following claims.
