Synthesis of polymer materials by low energy electron beam. III. Effects of polymerization temperature in EB solid-state polymerization of semicrystalline urethane-acrylate film

In an electron beam (EB) polymerization of a urethane-acrylate prepolymer, the polymerization temperature greatly affected the structure and properties of the resulting gel film. Urethaneacrylate, which was synthesized by the reaction of poly(butylene adipate)diol, 4,4′-diphenylmethane diisocyanate, and 2-hydroxyethyl acrylate, was used as a prepolymer. The prepolymer was semicrystalline and showed a melting point in the region of 50–60°C. The maximum polymerization rate of the prepolymer was obtained when the prepolymer film was irradiated in the temperature range of 25–40°C. EB polymerization below the melting point (T_m) of the prepolymer produced semicrystalline polyurethane-acrylate gel films with a spherulitic texture. On the other hand, EB polymerization above the T_m destroyed the crystalline phase of the prepolymer to give transparent gel films. The gel film cured below the T_m had higher stress at yield, Young's modulus, and tensile strength than those cured above the T_m. Such temperature effects are attributed to whether or not the EB polymerization proceeds with retention of crystalline structure of the prepolymer.     

Syntheses and cured films properties of UV-autocurable BTDA-based multiacrylate resins

A series of UV-autocurable 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) and benzophenone tetracarboxylic acid (BTAc)-based multiacrylate resins containing pendant glycidyl methacrylate (GMA) or glycidyl acrylate (GA) and 2-hydroxyethyl acrylate (HEA) or 2-hydroxyethyl methacrylate (HEMA) were synthesized. The effects of the acrylic functional groups, the moles of GMA, and the molar ratio of HEMA/HEA on their properties were investigated. The prepared autocurable resins are cured rapidly when exposed to UV or sunlight radiation without addition of any photoinitiator or Photosensitizer and the acrylate-type resin resulted in a lower thermal curing temperature and a fast curing rate. Increasing the moles of GMA or the molar ratio of HEMA/HEA on reaction leads to a higher cross-linking density and resulted in film with a higher Young's modulus, breaking strength, and lower elongation. The methacrylate-type resin cured to a very hard, but brittle film with a higher Young's modulus and lower elongation. However, the acrylate-type resin cured to a hard tough film with a lower Young's modulus and higher elongation. The cured methacrylate-type resin results in a lower weight loss at temperature below 300°C due to a higher cross-linking density and lower residual weight percent at 600°C due to the lower percent of benzene rings in the resin. The film properties of the resins coated on steel plates were also investigated. © 1994 John Wiley & Sons, Inc.     

Ultraviolet-photocurable oligomer. II. Syntheses and cured film properties of ultraviolet-photocurable BTDA-based caprolactone multiacrylate oligomers

A series of ultraviolet (UV)-photocurable 3,3′4,4′-benzophenone tetracarboxylic dianhydride (BTDA)-based multiacrylate oligomers containing pendant glycidyl methacrylate (GMA) or glycidyl acrylate (GA) and caprolactone acrylate (Tone M-100) or caprolactone methacrylate (Tone M-201) were synthesized. The effects of the acrylic functional groups, the moles of GMA, and the molar ratio of Tone M-201 to Tone M-100 on their properties were investigated. The prepared photocurable oligomers were cured rapidly when exposed to UV or sunlight radiation without the addition of any extra photoinitiator or photosensitizer. The acrylate-type oligomer resulted in a lower thermal curing temperature and a fast curing rate. Increasing the moles of GMA or the molar ratio of Tone M-201/Tone M-100 on reaction led to a higher crosslinking density and resulted in film with higher Young's modulus, higher breaking strength, and lower elongation. The methacrylate type oligomer cured to a very hard but brittle film with higher Young's modulus and lower elongation. By contrast, the acrylate-type oligomer cured to a hard, tough film with lower Young's modulus and higher elongation. The film properties of the oligomers coated on steel plates were also investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1625–1634, 1997     

Preparation and properties of UV-autocurable BTDA-based polyurethane methacrylates

Syntheses of several UV-autocurable methacrylourethanes and the effects of polyol type on their properties are investigated. Autocurable benzophenone tetracarboxylic dianhydride (BTDA)-based polyurethane methacrylates are prepared by addition reaction from benzophenone tetracarboxylic dianhydride (BTDA), 2,4-toluene diisocyanate (TDI), 2-hydroxyethyl methacrylate (HEMA), and polyol (polyethylene glycol, polydiethylene succinate, polydiethylene maleate, or polydiethylene hexamethylene-dicarbamate). Autocurable oligomers possess good pot life and are cured rapidly when exposed to ultraviolet (UV) radiation without the addition of photoinitiator. The different polyols are used to obtain wide range properties of cured films with a glass transition temperature (T_g) range of -10.5-5.5°C. Increasing the T_g of polyol shifts the dynamic mechanical storage modulus and loss factor of the cured film to high temperature. For practical application, oligomer is mixed with reactive monomers to bring the systems to a workable viscosity at room temperature. Among the monomers, the higher the composition of hydroxyethyl acrylate in the oligomer-monomer system, the higher the curing rate of the system as compared with neat oligomer. Moreover, increasing the chain length of dimethacrylate monomers results in a decrease in breaking strength from 160 to 140 kg/cm², in Young's modulus from 771 to 400 kg/cm², and in glass transition temperature from 18 to 6.5°C, while the elongation at breaking increases from 70 to 130%.     

Effects of reaction and cure temperatures on morphology and properties of poly(ester‐urethane)

Poly(ester‐urethane) was synthesized from poly(ethylene glycol adipate) (PEG) and 2,4‐toluene diisocyanate (TDI) to study the effects of reaction temperature and cure temperature on the crystallization behavior, morphology, and mechanical properties of the semicrystalline polyurethane (PU). PEG as soft segment was first reacted with TDI as hard segment at 90, 100, and 110°C, respectively, to obtain three kinds of PU prepolymers, coded as PEPU‐90, PEPU‐100, and PEPU‐110. Then the PU prepolymers were crosslinked by 1,1,1‐tris (hydroxylmethyl) propane (TMP) and were cured at 18, 25, 40, 60, and 80°C. Their structure and properties were characterized by attenuated total reflection Fourier transform infrared, wide‐angle X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis, and tensile testing. With an increase of the reaction temperature from 90 to 100°C, the crystallinity degree of soft segment decreased, but interaction between soft and hard segments enhanced, leading to the increase of the glass transition temperature (T_g) of soft domain and tensile strength. When the cure temperature was above 60°C, miscibility between soft and hard segments of the PEPU films was improved, resulting in relatively low crystallinity and elongation at break, but high soft segment T_g and tensile strength. On the whole, all of the PEPU‐90, PEPU‐100, and PEPU‐110 films cured above 60°C possessed higher tensile strength and elongation at break than that of the films cured at other temperatures. The results revealed that the reaction temperature and cure temperature play an important role in the improvement of the crosslinking structure and mechanical properties of the semicrystalline PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 708–714, 2006     

Preparation and properties of UV-autocurable BTDA-based epoxy-multiacrylate resins. Effects of the degree of polymerization and the epoxy type

A series of UV-autocurable epoxy-multiacrylate resins was synthesized, and the effects of degree of polymerization (DP) and epoxy type on their properties were investigated. These autocurable multiacrylate resins possess good pot life and are cured rapidly when exposed to ultraviolet (UV) without the addition of photoinitiator or photosensitizer. The curing rate of the autocurable resins was probably dependent on the number of abstractable hydrogen in epoxy resins. Stress-strain, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) were used to characterize the properties of cured multiacrylate resins. Increased crosslinking density of cured films improved tensile properties. Increasing the molar ratio of epoxy resin in the multiacrylate resins was found to decrease the effective acrylate concentration of resins and to depress crosslinking density of cured resins, which also resulted in an increased elongation at break but a decreased Young's modulus and breaking strength. Furthermore, the different structures of epoxy resins were used to give wide range properties of cured epoxy-multiacrylate resins with a glass transition temperature (T_g range from 74 to 102°C. The film properties of the multiacrylate resins coated on steel plates were also investigated.     

Ultraviolet curing of liquid polysulfide thiourethane acrylate

A series of liquid polysulfide thiourethane acrylate prepolymers were synthesized by the reaction of liquid polysulfide with isocyanate and hydroxyethyl acrylate. With and without a combination of acrylic monomers, the prepolymers were cured with ultraviolet radiation. The films exhibited a higher soft‐segment glass‐transition temperature than metal oxide cured polysulfide. With the addition of a diluent, the tensile strength and modulus increased, whereas the ultimate elongation decreased. The polysulfide backbone, combined with the crosslink generated from the photopolymerization of acrylic, produced films with superior oil resistance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2358–2363, 2004     

Ultraviolet curable dry polymer films from emulsion polymers

Low levels of functional acrylic monomers were incorporated into a core‐shell acrylic copolymer by seeded emulsion polymerization. The increase in glass transition temperature, T_g, from DSC measurement has showed that although certain amount of crosslinking reactions have occurred during the polymerization and isolation of the copolymer, the dried copolymer films could undergo further curing by UV irradiation. The structure and amount of the functional monomer, concentration of photoinitiator, and the extent of UV exposure have exerted significant influence on the T_g of the dry copolymer films. Because of the relatively low level of incorporated unsaturation, there was no significant change in FTIR during the curing of the film. Further, crosslinking of the copolymer film induced by UV irradiation has significantly increased the resistance to swelling in alkaline solution, although the gel content remained the same. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2317–2322, 2006     

Carbazole‐based poly(aryl ether ketone) containing crosslinkable allyl groups on the side chains: synthesis,characterization and properties

This paper presents a feasible method for introducing crosslinkable groups into a polymer to achieve excellent chemical resistance and improved thermal stability. Here, 3,6‐bi(4‐fluorobenzenzoyl)‐N‐allylcarbazole, a novel allyl‐containing difluoroketone monomer, is synthesized and characterized. The resulting monomer is polymerized with phenolphthalein through the aromatic nucleophilic substitution reaction at 160 °C to provide the soluble poly(aryl ether ketone) (PAEK) with a pendant allyl group. The obtained PAEK is characterized using Fourier transform infrared spectroscopy, NMR and gel permeation chromatography. The crosslinking reaction of the polymer occurs at 270 °C, and it imparts excellent solvent resistance. DSC analysis shows that the glass transition temperature (T_g) of the cured polymer increases to 262–306 °C when the curing temperature is elevated or when the curing time is extended within certain limits. The rate of increase of T_g and the rate of the crosslinking reaction decrease as the curing time is extended under all of the investigated curing temperatures. The cured PAEKs possess good thermal stability with 5% weight loss temperatures up to 450 °C. The tensile strength and Young's modulus of the polymer film cured at 300 °C for 2 h are 65 MPa and 1.4 GPa, respectively. In addition, the polymer films before and after curing exhibit similar UV?visible absorption and blue light emission. © 2014 Society of Chemical Industry     

Mechanical and thermal properties of chitosan‐filled polypropylene composites: The effect of acrylic acid

The mechanical properties, morphology, and thermal properties of chitosan‐filled polypropylene (PP) composites have been studied. The effect of the chemical modification of chitosan by acrylic acid treatment was also investigated. Results showed that the tensile strength and elongation at break decreased but that the Young's modulus of the composites increased with increasing filler loading. Chemical modification of chitosan with acrylic acid improved the tensile strength and Young's modulus of the composites but reduced the elongation at break. Thermogravimetric analysis showed that the addition of chitosan improved the thermal stability of the PP/chitosan composites as compared to that of neat PP. Chemical modification of chitosan had a positive effect on the thermal stability of the composites. This change was attributed to improvement of the interfacial adhesion between the chitosan and PP matrix due to formation of a covalent bond between chitosan and acrylic acid. Meanwhile, differential scanning calorimetric analysis showed that the addition of filler did not significantly change the melting temperature (T_m) of the PP/chitosan composites. The degree of crystallinity of the composites decreased with the addition of chitosan. At a similar chitosan loading, the chemically treated PP/chitosan composites exhibited higher crystallinity than the untreated composites and exhibited slightly increased T_m. A scanning electron microscopy study of the tensile fracture surface of chemically treated PP/chitosan composites indicated that the presence of acrylic acid increased the interfacial interaction between chitosan and the polypropylene matrix. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Syntheses and properties of UV-autocurable BTDA-based polyester multiacrylates. II. Effect of polyol type and reactive monomer

Several families of UV-autocurable benzophenone tetracarboxylic dianhydride (BTDA)-based polyester multiacrylate oligomers containing pendant glycidyl methacrylate (GMA) were synthesized and the effects of acrylic functionality and polyol type on their properties were investigated. The obtained autocurable oligomers possess good pot life and are cured rapidly when exposed to ultraviolet (UV) radiation without the addition of photoinitiator or photosensitizer. Different polyols were used to obtain wide range properties of cured multiacrylate oligomers with a glass transition temperature (T_g) range of 84–130°C. A further modification of the multiacrylate oligomers was obtained by mixing them with reactive monomers having different molecular structure and methacrylic functionality.     

Synthesis and properties of ultraviolet/moisture dual‐curable polysiloxane acrylates

Ultraviolet (UV)/moisture dual‐curable polysiloxane acrylates (PSAs) were prepared from N,N‐bis[3‐(triethoxysilyl)propyl]amine (G402) and ethoxylated trimethylolpropane triacrylate (EB160) through Michael addition. The obtained prepolymers were characterized by ¹H‐NMR and FTIR. The rheological behavior of the prepolymers exhibited the properties of a Bingham fluid and the apparent viscosity was directly correlated with molecular weight. The photocuring kinetics of PSA were studied using photo‐DSC and all the polymerization conversions were high. With increasing content of tertiary amine in the prepolymer, the photocuring rate in air increased as well. The moisture‐curing kinetics of the prepolymers was studied using FTIR. It was found that the curing mechanism may be described as the transforming of Si O C into Si O Si structure, which was consistent with the theoretical expectation. DSC and TGA were used to characterize the glass‐transition temperatures and the thermomechanical stability of the prepolymers. Measurements of physical properties showed excellent gloss, impact strength, and high electric resistance for both UV‐ and moisture‐cured films, but poor adhesion for UV‐cured films and lower hardness for moisture‐cured films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 846–853, 2005     

A dynamic mechanical study of the curing reaction of an unsaturated polyester

The curing process of an unsaturated polyester was followed by employing the dynamic spring analysis (DSA) technique attached to the Rheovibron viscoelastometer. The storage and loss moduli and the gel times of the resin with various concentrations of initiator (methyl ethyl ketone peroxide) were determined at several temperatures. The activation energy for the curing process studied was about 40 kJ/mol. Temperature effects on films partially cured below the ultimate glassy transition temperature (T_g) were studied similarly using the tensile mode on the Rheovibron from room temperature to 120°C. Two modulus peaks were observed upon heating and these were independent of precure conditions. The lower temperature peak was the result of continued curing and the higher temperature peak was attributed to the glassy relaxation of the cured product. The DSA technique were found to be useful for characterization of the curing process and the results showed good qualitative agreement with those obtained by tensile measurements using cast films when the shapes of the curves were compared.     

Preparation and surface characteristics of low-temperature curing fluorinated cathodic electrodeposition coating

Fluorinated cationic cathodic electrodepositing (CED) resins were synthesized by copolymerization of several acrylic monomers including Zonyl. Water dispersible cationic blocked-diisocyanate (denoted as TId) was also synthesized from isophorone diisocyanate (IPDI), cationic triethanolamine (TEOA), and dimethylpyrazole as the cross-linker for the low temperature curing at 90–120 °C. The emulsion stability of the cationic fluorinated CED resin was improved by ionization of the cross-linker TId, showing a mean particle diameter of 140–150 nm and a narrow distribution. 0.5 wt% of curing catalyst dibutyltin dilaurate (DBTL) was enough to accelerate the curing reaction and the gel content of the TId cured fluorinated CED film was higher than 90 wt% after being cured at 130 °C for 40 min. The contact angle and XPS spectrum of the CED film demonstrated that the surface enrichment of C–F₂ and C–F₃ groups effectively reduced the surface tension of the fluorinated CED coating and its surface tension γ_sv is even lower than 15 mN m⁻¹ for PTFE. The preheating of the CED film above T_g but below curing temperature promoted this surface enrichment of the fluorinated groups. Thermal fragmentation of the fluorinated side chains in the CED resins was successfully avoided due to using TId for low temperature curing.     

Synthesis and characterization of uv-curable acrylated urethane prepolymers,I. Effects of reactive diluents and relative humidity on physical properties

A UV-curable acrylated urethane prepolymer was synthesized from tolylene-2,4-diisocyanate (TDI), a polyether polyol (Arcol 1131) and endcapped with 2-hydroxyethyl methacrylate (HEMA) by addition reaction in the presence of dibutyltin dilaurate as catalyst. UV curing was performed with either diethylene glycol diacrylate or thiodiethylene glycol diacrylate as reactive diluent. The effects of reactive diluent types, their concentrations and the humidity of environment on mechanical properties of cured films were investigated. Changes in the tensile strength, elongation and Young's modulus values of the cured films upon addition of reactive diluents with different concentrations were related to the effect of the diluent on the crosslinking density of cured films. The increase of relative humidity from 50 to 95% caused a decrease of tensile strength and Young's modulus values of cured films. It is proposed that the decrease of these physical properties in high relative humidity is due to the formation of hydrogen bonding in polymer chains caused by water molecules.     

Effect of chemical structure of allyl ethers on polymerization and properties of multifunctional acrylate systems

Allyl ether resins with various chemical structures and degrees of functionality were used as promoters and cross-linkers for polymerization of acrylic oligomers at room temperature in air. Thin films were prepared to allow monitoring of polymerization via disappearance of acrylate and allylic unsaturation by FTIR. The effect of air upon curing of films was investigated; excluding air from the surface of the film had a much greater effect than did addition of allyl ether. In air, the curing rate and extent of cure were found to be dependent upon molecular weight M_n and degree of functionality of the allyl compounds. At high allyl monomer concentrations, homopolymerization of the allyl groups occurred. The mechanical properties (tensile strength, Young's modulus, and elongation at break) of films were evaluated on an Instron, whereas viscoelastic properties, transition temperatures, and cross-link densities of polymer bars were studied by dynamic mechanical analysis and relaxation measurements. The study showed that addition of highly functional allyl ethers combines the advantages of an air-curable system with those of highly cross-linked materials, allowing ultimate properties to be tailored.     

Effect of addition of nanosized UV absorbers on the physico-mechanical and thermal properties of an exterior waterborne stain for wood

This study describes the effects of the addition of inorganic nanosized UV absorbers on physico-mechanical and thermal properties of an exterior commercial acrylic-based waterborne stain for wood. Electronic microscopy and water vapor (WV) permeability measurements were performed to characterize the free films of the acrylic stain and resulting nanocomposite coatings. An accelerated weathering method was used to evaluate aging behavior of the coatings on wood through appearance, T_g, abrasion resistance, adhesion strength, hardness and Young's modulus changes. In addition to improving the protection against UV, the doped TiO₂ and silica-coated ZnO nanoparticles in powder form have improved the abrasion resistance and barrier effect against water vapor diffusion of the acrylic stain. For most of nanocomposite coatings, the addition of ZnO hydrophilic nanoparticles in predispersed form has resulted in a decrease in WV permeability, while the adhesion strength and abrasion resistance of those coatings were negatively affected. The addition of ZnO nanoparticles has decreased the T_g of the acrylic stain. Finally, the accelerated weathering has induced an increase in T_g, hardness, Young's modulus (stiffness) and an increase in apparent adhesion strength and abrasion resistance of the coatings. The T_g values of the aged nanocomposite coatings were lower than that of unmodified acrylic stain.     

Mechanical and thermal properties of epoxy resins with reversible crosslinks

The tensile properties: Young's modulus, ultimate tensile strength, ultimate elongation, the glass transition temperature, and the dynamic mechanical properties (dynamic shear modulus (G'), loss tangent (Tan δ)), of three epoxy resins (Epon 828, Epon 836, Epon HPT 1071) cured with the disulfide-containing crosslinking agent—4.4-dithiodianilme (DTDA) have been characterized. The results show that DTDA is a satisfactory crosslinking agent for the epoxide resins that have been studied as compared to the well-known curing agent methylene dianiline (MDA). There are no significant differences between the properties of Epon 828 cured with DTDA at stoichiometric ratio (2:1) and Epon 828 cured with DTDA at small amine excess ratio (1.75:1). The glass transition temperature of the cured tetrafunctional epoxy resin Epon HPT 1971 (235°C) is significantly higher than that of difunctional epoxy resins such as Epon 828 (T_g–175°C), but the product is too brittle to be used without plasticizer.     

Syntheses and properties of urethane prepolymers and their corresponding crosslinked films

Trimethylol propane (TMP), polyglycol (PG), and toluene diisocyanate (TDI) were reacted in various molar ratios to produce TMP–TDI–PG–urethane prepolymers and then mixed with equivalent isocyanate generator (Desmodur AP-Stable) in a mixture of m-cresol and naphtha to give polyurethane varnishes which finally became crosslinked films by the casting method. The mechanical properties and viscoelasticities of the PG-modified and PG-free polyurethane crosslinked films and the practicability of magnet wires coated with them were studied in this article. Three different PGs used in this experiment were polyethylene glycol, PEG(#400), polypropylene glycols, PPG(#1000) and PPG(#2000). In the case of adding PEG(#400) for modification, strength at break increased but elongation did not change. Meanwhile, glass transition temperature (T_g) shifted to lower temperature with increasing molar ratio. In the case of adding PPG(#1000) and PPG(#2000) for modification, the samples changed their mechanical properties from hard and brittle to soft and tough. With increasing molar ratios, strength at break initially increased and then decreased gradually, and elongation varied a lot and was consistently contrary to strength at break. T_g occurred at two regions: one at high temperature above 100°C for small molar ratios and the other at low temperature below 100°C for high molar ratios. Besides, for all PG-modified polyurethane crosslinked films, strength at break showed a local maximum at TMP/TDI/PG = 1/1/0.5, which indicated their homogeneous structures. The molar ratios of PG-modified urethane prepolymers, which are suitable for manufacturing practical magnet wires according to testing method JIS-C-3211, are as follows: TMP/TDI/PPG(#100) = 1/1/0.15–0.35 and TMP/TDI/PPG(#2000) = 1/1/0.10. PEG(#400)-modified magnet wires were not accepted on the aging test. The properties of crosslinked films of practical magnet wires are generally as follows: strength at break at 200–700 kg/cm², elongation less than 41%, and T_g at 100–200°C.     

Compatibilization and property characterization of polycarbonate/polyurethane polymeric alloys

Semi‐crystalline dendritic poly(ether‐amide)s were synthesized by modifying hydroxyl end‐groups of dendritic poly(ether‐amide) with aromatic urethane acrylate and octadetyl isocyanate. The ratio of these modifiers can adjust the final properties of products to fulfill the requirements of UV‐curable powder coatings. These UV‐curable semi‐crystalline dendritic poly(ether‐amide)s have a T_g in the range of 41–45°C and a T_m of around 120°C. Their thermal behavior and semi‐crystalline properties were studied by DSC and XRD. The photopolymerization kinetics was investigated by Photo‐DSC. The residual unsaturation, thermal stability, and hardness of the UV‐cured films were also studied. The obtained results show that these semi‐crystalline dentritic poly(ether‐amide)s may be used as prepolymers in UV‐curable powder coating systems. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 287–291, 2003