Photocrosslinking of halogen‐free flame‐retarded ethylene‐vinyl acetate copolymer by phosphorous‐nitrogen compound NP28

The photoinitiated crosslinking of halogen‐free flame‐retarded ethylene‐vinyl acetate copolymer (EVA) by the phosphorous‐nitrogen compound NP28 in the presence of photoinitiator and crosslinker and characterization of the related properties have been investigated by gel determination, heat extension test, thermogravimetric analysis (TGA), mechanical measurement, and thermal aging test. The photocrosslinking efficiency of EVA/NP28 blend and various factors affecting the crosslinking process, such as photoinitiator, crosslinker, NP28 content, and irradiation temperature, were studied in detail and optimized by comparison of gel content. The results show that the EVA/NP28 blend filled with 28.2 wt % NP28 with a thickness of 1.6 mm is homogeneously photocrosslinked to a gel content of above 80 wt % with 4.8 s UV‐irradiation under optimum conditions. The data from TGA, mechanical measurement, and thermal aging test give evidence that the thermal stability and mechanical properties of photocrosslinked EVA/NP28 blend are much better than those of the unphotocrosslinked one.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of a novel high‐oil‐absorbing resin

A high‐oil‐absorbing resin, which was a low crosslinking resin, was synthesized by conventional suspension copolymerization in this study. The effects of the monomer ratio, crosslinker, initiator, ratio of water to oil, and defined optimum reaction conditions were studied. The highest oil absorptivity of the resin was about 11.5 g/g in diesel and the oil‐absorption saturation time was 3 days when the best process conditions were as follows: ratio of styrene to ethylene–propylene–diene terpolymer = 40/60 w/w, amount of crosslinker divinylbenzene = 1.0 wt %, amount of benzoyl peroxide = 1.0 wt %; proportion of gelatin to calcium phosphate = 0.2 g/0.1 g, stirring speed = 500 r/min, and proportion of water to oil = 15 : 1. By using such methods as infrared spectroscopy, thermogravimetric analysis, and other methods, we studied the oil‐absorbing resin structure, oil‐absorption rate, oil‐absorption saturation time, and oil‐absorption rate twice. The oil‐absorbing resins were used repeatedly through the extraction of ethanol. The experiment results show little effect on the oil‐absorption properties. The oil‐absorption rate constant was evaluated for diesel, and the oil‐absorbing process obeyed the first‐order kinetics equation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of a Zr‐containing silicate‐based epoxy‐functional polymer nanocomposite system

As a continuation of efforts to explore the potential of certain types of polymer nanocomposites to be successful candidates as dental restoration/adhesion materials, a Zr‐containing and organically modified silicate‐based material system with epoxy functionality was prepared by use of a sol–gel synthesis method, and UV light‐ and visible light (VL)‐curing processes. Comparative influences of the synthesis and processing parameters on the mechanical, thermal, and microstructural/nanostructural properties of the system were detailed. Zr‐containing species proved to more effectively catalyze the epoxy polymerization/crosslinking reactions than those containing Ti. Incorporation of Zr into the nanocomposite network led to significantly advanced mechanical properties. An elastic (Young's) modulus value of 23 MPa was achieved. The system with relatively high Zr content was successfully obtained, which also had higher thermal stability. Overall observations and results suggested that Zr content, and the UV light‐ or VL‐curing process could be capitalized on to modify the structure, and to improve the final properties of these material systems, which indicated a prospective opportunity for this material system to be utilized in dental restoration/adhesion applications. POLYM. ENG. SCI., 55:792–798, 2015. © 2014 Society of Plastics Engineers     

Photocrosslinking of an ethylene–propylene–diene terpolymer and the characterization of its structure and mechanical properties

An ethylene–propylene–diene terpolymer (EPDM) was photocrosslinked under UV irradiation with benzil dimethyl ketal (BDK) as a photoinitiator and trimethylolpropane triacrylate (TMPTA) as a crosslinker. The efficiency of the photoinitiated crosslinking system EPDM–BDK–TMPTA, various factors affecting the crosslinking process (the photoinitiator and crosslinker and their concentrations, the irradiation time, the temperature, the atmosphere and UV‐light intensity, and the depth of the UV‐light penetration), and the mechanical properties of photocrosslinked EPDM were examined extensively through the determination of the gel contents, infrared spectra, and mechanical measurements. EPDM samples 3 mm thick were easily crosslinked with a gel content of about 90% after 30 s of UV irradiation under optimum conditions. The photoinitiating system of a suitable initiator combined with a multifunctional crosslinker such as BDK–TMPTA enhanced the efficiency of the photocrosslinking reaction, especially by increasing the initial rate of crosslinking. The gel content of photocrosslinked EPDM, which was determined by the content of diene in EPDM, the depth of the UV‐light penetration, and the light intensity, played a key role in increasing the mechanical properties of the photocrosslinked samples in this work. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1837–1845, 2004     

Structure‐property relationship of substituted pyrrolidine functionalized CNT epoxy nanocomposite

Carbon nanotubes (CNTs) based polymer nanocomposites hold the promise of delivering exceptional mechanical properties and multifunctional characteristics. However, the realization of exceptional properties of CNT based nanocomposites is dependent on CNT dispersion and CNT‐matrix adhesion. To this end, we modified MWCNTs by Prato reaction to yield aromatic (phenyl and 2‐hydroxy‐4‐methoxyphenyl) substituted pyrrolidine functionalized CNTs (fCNT1 and fCNT2) and aliphatic (2‐ethylbutyl and n‐octyl) substituted pyrrolidine functionalized CNTs (fCNT3 and fCNT4). The functionalization of CNTs was established by Thermogravimetric analysis (TGA), Raman Spectroscopy, and XPS techniques. Optical micrographs of fCNT epoxy mixture showed smaller aggregates compared to pristine CNT epoxy mixture. A comparison of the tensile results and onset decomposition temperature of fCNT/epoxy nanocomposite showed that aliphatic substituted pyrrolidine fCNT epoxy nanocomposites have higher onset decomposition temperature and higher tensile toughness than aromatic substituted pyrrolidine fCNT epoxy nanocomposites, which is consistent with the dispersion results of fCNTs in the epoxy matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42284.     

Effects of crosslinking on the mechanical properties and biodegradability of soybean protein‐based composites

A green composite with good mechanical properties and acceptable biodegradability was developed using wood flour and soybean protein that was modified by thermal‐caustic degradation and chemical crosslinking with glyoxal and polyisocyanate (PMDI). Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) in combination with the traditional evaluations were employed to investigate the structure, morphology, and properties of the crosslinked soybean protein and the crosslinking‐modified wood/soybean protein composites to understand the effects of the crosslinker species on the mechanical properties, water resistance, and microbial biodegradation of soybean protein‐wood flour composites. The results indicated that the chemical crosslinking modification could improve the mechanical properties and water resistance but decrease the biodegradability of the wood/protein composite to a certain extent. Both glyoxal and PMDI alone as crosslinkers could not perfectly modify the soybean protein because of the high reactivity of PMDI and low crosslinking reactivity of glyoxal. The incorporation of glyoxal with PMDI could result in the desired crosslinking efficiency and good interfacial adhesion by compromising the advantages and disadvantages of glyoxal or PMDI alone as crosslinkers, which balanced the performances of the wood flour/soybean protein composite. The preferable combination crosslinker was composed of 50 wt % glyoxal and 50 wt % PMDI. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41387.     

Cationic photopolymerization of oxetane‐functionalized hyperbranched polymers

An aliphatic–aromatic pehenolic hyperbranched starting material (HBP‐OH) with phenolic end groups was 85% functionalized by a Mitsunobu reaction with oxetane groups (OXT‐HBP). This new hyperbranched polyester was used, at a concentration of 5–20 wt %, as an additive for the cationic photopolymerization of a commercial oxetane‐based resin, 4,4′‐bis[(3‐ethyl‐3‐ethyl‐3‐oxetanyl) methoxymethyl]biphenyl (OXBP). HBP‐OXT acted as a multifunctional crosslinker, copolymerizing with the oxetane ring of the OXBP resin, reacting through chain transfer with the remaining phenolic OH groups, or doing both. The result was an increase in the glass‐transition temperature due to the increase in the crosslinking density. An increase in the weight residue at a high temperature was found in the presence of HBP‐OXT and was attributed to the presence of phenolic groups, which are commonly used as antioxidant additives. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 293–299, 2005     

Application of phase dispersion–crosslinking synergism on recycling commingled plastic wastes

A tetra‐component blend, consisting of low‐density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), and polystyrene (PS), was studied as a model system of commingled plastic wastes (LDPE/PVC/PP/PS, mass ratio: 70/10/10/10). Effects of chlorinated polyethylene (CPE), ethylene–propylene–diene monomer (EPDM), styrene–butadiene–styrene (SBS), and their mixture (CPE/EPDM/SBS, mass ratio: 2/2/2) on the mechanical properties and morphology of the system were investigated. With addition of several elastomers and their mixture, the tensile strength of the blends decreased slightly, although both the elongation at break and the impact strength increased. Among these elastomers, EPDM exhibited the most significant impact modification effect for the tetra‐component blends. SBS and the mixture have a good phase‐dispersion effect for the tetra‐component blend. By adding a crosslinking agent [dicumyl peroxide (DCP)], the mechanical properties of the tetra‐component blends also increased. When either SBS or the mixture was added to the blend together with DCP, the probability that the crosslinking agent (DCP) would be at the interface improved because of the phase‐dispersion effect of SBS. Therefore, more co‐crosslinked products will form between LDPE and other components. Accordingly, remarkable improvement of the interfacial adhesion and hence the mechanical properties of the tetra‐component blends occurred. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2947–2952, 2001     

Characterization and gas permeation properties of UV‐cured fluorine‐containing telechelic polyimide membranes with a crosslinker

The characterization and gas permeation properties of ultraviolet (UV)‐cured fluorine‐containing telechelic polyimide membranes and end‐capped with a crosslinker with acryloyl groups were investigated. Membrane formation property was improved by the addition of crosslinker by using UV irradiation. The densities of UV‐cured membranes were almost similar to each other, and high gel fraction was shown on the UV‐cured membranes. This result suggests that the crosslinker promotes crosslink reaction at the polymer chain ends and does not induce appreciable membrane densification. Furthermore, the gas permeability of the UV‐cured membranes was higher than that of the membrane without the crosslinker. The higher gas permeability is due to the new crosslink structure formed at the polymer chain ends, which was promoted by the crosslinker after UV irradiation, but did not induce appreciable membrane densification. The use of a BEI crosslinker in the telechelic polyimide membranes promoted the crosslink reaction and increased the H₂ selectivity because H₂ permeability was not sensibly affected by the crosslink reaction. POLYM. ENG. SCI., 54:1089–1099, 2014. © 2013 Society of Plastics Engineers     

Reworkable UV curing materials

Novel UV curing materials which became soluble in solvents by photo/thermal degradation were studied. Three types of systems were designed and prepared, i.e. (a) base polymer/crosslinker blended system, (b) functionalized polymer system, and (c) multifunctional acrylate monomer system. In the base polymer/crosslinker blended system, as a crosslinker, multifunctional epoxy compounds containing tertiary esters of carboxylic acid or sulfonate ester units were synthesized and used in combination with polyvinylphenol. Functionalized polymers bearing epoxy units and thermally degradable linkages in the side chain were prepared. Furthermore, multifunctional methacrylate or acrylate monomers bearing acetal linkages in a molecule were prepared. Photocrosslinking and thermal decrosslinking of those materials were studied.     

Effects of Photodegradable o‐Nitrobenzyl Nanogels on the Photopolymerization Process

A series of partially photodegradable o‐nitrobenzyl nanogels (NBNG) with different caged functional groups (COOH, OH, SH) are prepared and compared with a nondegradable nanogel as additives in photocurable materials. Photoinduced nanogel network disruption and photoinitiated polymerization of infiltrating and dispersing monomer could be controlled independently. In triethylene glycol dimethacrylate (TEGDMA), o‐NBNGs that release a COOH or OH functional group upon photodegradation of the o‐nitrobenzyl crosslinker, the reduced chemical crosslinking density of the nanogel network allows greater penetration of monomer into the partially degraded nanogel network, which results in an increase in volumetric shrinkage and polymerization stress. In contrast, the formulation of o‐NBNGs with caged SH groups also can be photodegraded but is able to rebuild the chemical crosslinking through thiol‐based chain transfer reactions when photocured as a dispersion in TEGDMA. As such, it behaves like a photo‐inert nanogel. Dynamic thermomechanical analysis and testing by three‐point bending further confirms the photoinduced crosslink density variation influences mechanical properties of the final polymer networks. This work demonstrates the inherent properties of the nanogel network and the type of crosslinking can alter the performance of the photocured resin while a separate photochemical process can be used to regulate photoinduced polymerization.     

UV‐curable methacrylic epoxy dispersions for cationic electrodeposition coating

UV‐curable epoxy dispersions were prepared for cationic electrodeposition coating. Sequential reactions were used to introduce methacrylate groups to the epoxy‐amine polymer as coupling agents to the multifunctional acrylates. The molecular weight values of the prepared epoxy‐amine polymer were M_n = 2800 and M_w = 4300. The neutralized epoxy‐amine polymer containing photoinitiator with or without multifunctional acrylate (pentaerythritol triacrylate, PETA) could be dispersed into a stable dispersion without any phase separation. The size of the particles in these epoxy dispersions was approximately 77.7 nm, and increased with the incorporation of PETA. The electrodeposition process was introduced to the prepared epoxy dispersions, and the electrodeposited films were cured by UV irradiation after a 10‐min flash off at 80°C. Studies of the kinetics using photo‐DSC revealed that the crosslinked films containing PETA gave a higher conversion rate than those without PETA, resulting in better resistance to methyl ethyl ketone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5566–5570, 2006     

Improvement in wettability of pressure‐sensitive adhesive on silicon wafer using crosslinking agent with siloxane groups

Acrylic copolymers are prepared by radical polymerization of 2‐ethylhexyl acrylate, ethyl acrylate, and acrylic acid followed by crosslinking to manufacture the pressure‐sensitive adhesives (PSAs) for silicon wafer protection. Both higher reliability and wettability are required for the protective acrylic PSAs in the semiconductor processing applications. The siloxane linkages are introduced in the acrylic PSAs via crosslinking with siloxane‐containing crosslinking agent to modify the thermal and wetting properties of PSAs efficiently. The more efficient formation of crosslinked network structure was achieved with higher content of tetra‐functional crosslinking agent, and the surface energy of PSAs decreased significantly with increasing the content of siloxane linkage resulting in the improved areal wetting rate. The thermal stability of PSAs was also improved significantly by incorporation of siloxane linkages. The adhesion properties such as peel strength and probe tack of acrylic PSAs decreased significantly by increasing the content of either crosslinking agent or siloxane linkage. The acrylic PSA with siloxane group showed both satisfactory wetting and clean debonding properties for the optimal protection of thin silicon wafers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

New method for fabricating an α‐fetoprotein affinity monolithic polymer array

Bisphenol A based epoxy acrylate (BABEA), a commercial UV‐curable material, was introduced as a crosslinker for the fabrication of an epoxy‐functionalized monolithic polymer array through UV‐initiated copolymerization with glycidyl methacrylate as the functional monomer and poly(ethylene glycol) 200 as the porogen. Scanning electron microscopy images showed that the monolithic poly(bisphenol A based epoxy acrylate‐co‐glycidyl methacrylate) [poly(BABEA‐co‐GMA)] exhibited a well‐controlled skeletal and well‐distributed porous structure. The α‐fetoprotein (AFP) immunoaffinity monolithic polymer array prepared by the immobilization of AFP on epoxy‐functionalized monolithic arrays was used as an immunosensor for chemiluminescent AFP detection. X‐ray photoelectron spectroscopy results indicate that the AFP antibody was successfully immobilized on the monolithic poly(BABEA‐co‐GMA) array. With a noncompetitive immune‐response format, the proposed AFP immunoaffinity array was demonstrated as a low‐cost, flexible, homogeneous, and stable array for AFP detection. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41792.     

Influence of selected photoinitiators on important properties of photoreactive acrylic pressure‐sensitive adhesives

Photoreactive solvent‐borne pressure‐sensitive adhesives are not commercially available in the market. The reason for it is that the UV‐initiated crosslinking has sense only in the case of solvent‐free self‐adhesive systems. Investigations conducted in Institute of Chemical Organic Technology have shown that the photoreactive solvent‐borne acrylic PSA are conventional crosslinked solvent‐borne acrylic PSA used as crosslinking agents typical metal chelates as titanium acetylacetonate (TiACA), aluminum acetylacetonate (AlACA) or thermal reactive crosslinker melamine‐formaldehyde resin Cymel 303 clear considered. The main purpose of the investigation was to study the influence of diverse photoinitiators on main properties, such as shrinkage, tack, peel adhesion, and shear strength of solvent‐based acrylic pressure‐sensitive adhesives. The interesting alternative to conventional photoinitiators is unsaturated photoinitiators described in this article. Following unsaturated photoinitiators were used: 4‐acryloyloxy benzophenone, 4‐acryloyloxyethoxy benzophenone, and 4‐acryloyloxybutoxy benzophenone. The influence of the crosslinking agents or crosslinking methods was determined in relation to the reaction time and to the concentration versus adhesion properties. The increase of photoinitiator concentration causes in the decrease of the shrinkage. Increasing the UV dose during the crosslinking of acrylic PSA film leads clearly to better shrinkage resistance. The best results of the lowest shrinkage value of 0.35% were given by using 4‐acryloyloxy benzophenone. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Loading the polyol carbonization agent into clay nanotubes for the preparation of environmentally stable UV‐cured epoxy materials

The halloysite nanotubes (HNTs) were loaded with pentaerythritol (PER). The as‐prepared composite (HNT‐P) and ammonium polyphosphate (APP) was subsequently added to the UV‐curable epoxy resins, giving a new flame‐resistant system. Loading of the hydrophilic PER into HNT can reduce the moisture absorption in the UV‐curable epoxy resins. The flame retardancy was evaluated by means of the cone calorimeter and limit oxygen index test. The results showed that the flame retardancy of the modified epoxy resin was greatly improved with an obvious decrease in both the heat release and smoke release. Moreover, it was revealed that HNT could catalyze the reaction of APP and PER, and the burning surface of the epoxy resin should be covered by the polyphosphoric‐HNT intumescent char layer. We have measured the moisture sorption and dynamic mechanical properties of the UV‐cured epoxy resins. As compared to the use of the simple mixture of PER and HNT, the use of the HNT‐P nearly kept the storage modulus at about 1809 Mpa and reduced the moisture absorption by 58.2 wt % at 40 °C. The results proved that the addition of the HNT‐P obtained lower moisture absorption and higher stability of the mechanical properties than adding the simple mixture. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45045.     

Monohydroxy‐hydrazone‐functionalized thermally crosslinked polymers for nonlinear optics

The synthesis and properties of six hydrazone‐functionalized crosslinked polymers possessing stable nonlinear optics (NLO) properties are presented. First, a series of six hydroxy‐functionalized, NLO‐active hydrazone chromophores were synthesized. These chromophores were then grafted via its hydroxy functionality on an epoxy polymer to obtain the six NLO‐active soluble prepolymers. The grafting reaction yielded multiple secondary hydroxyl sites, which were used for further crosslinking by formulation of the prepolymer with a blocked polyisocyanate crosslinker. This formulation was spin‐coated on glass slides to form 2–2.5 μ thick defect‐free transparent films. The films were corona‐poled above their glass‐transition temperatures to align the chromophores in a noncentrosymmetric fashion and were simultaneously cured. The thermal characteristics of the second‐order nonlinearity of the six polymers were compared to illustrate the key structure–property relationships underlying the performance of the films in terms of NLO activity and thermal stability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 770–781, 2004     

Room Temperature Curing Epoxy Adhesives for Elevated Temperature Service, Part II: Composition, Properties, Microstructure Relationships

Low temperature curing epoxy formulations for elevated temperature service have been previously developed and studied (Part I¹). Balanced performance with respect to shear and peel properties have been obtained for a system composed of a tetra and trifunctional epoxy blend crosslinked by a mixture of multifunctional amine and an amino-terminated elastomer. In continuation of the previous study, the present one is aimed at investigation the effect of substitution of difunctional epoxy resin and curing agent for trifunctional ones on the developing microstructure and resulting mechanical properties. Furthermore, a new type of amino-terminated-acrylonitrile (ATBN) and an epoxy-terminated silane were included in the present investigation. Experimental results show that while reduction in the overall functionality of the reactants results in a lower lap shear strength, it gives rise to enhancement in peel strength. The same effect was observed when the new ATBN was used. Thermal analysis of the polymerization processes, taking place during curing of the various low temperature curing formulations, indicates that the curing activation energies are appreciably lower compared with high temperature curing systems. Addition of silane, ATBN and substitution of the multifunctional amine curing agent by a lower functional one, resulted in a moderate increase in the activation energy. The basic formulation, comprising a tetra- and trifunctional resin blend and a multifunctional amine and ATBN crosslinking mixture, developed a typical two-phase matrix-rubber microstructure. A third phase was observed when the trifunctional epoxy resin or the multifunctional curing agent was substituted by lower functional ones. A similar three-phase morphology was obtained when the epoxy-terminated silane was added to the basic treta- and trifunctional reactant system.     

Solvent‐stable UV‐cured acrylic polysulfone membranes

A systematic investigation of the effect of the presence of acrylate resin on polysulfone‐based membranes was performed with the aim of obtaining chemically stable crosslinked membranes without affecting their flux performances. The membranes were prepared via UV curing of the polymer dope followed by a non‐solvent‐induced phase separation process. Two different acrylic monomers were investigated and their amount was varied in the polymer dope, to study the influence of concentration on final results. High crosslinking degrees were achieved by irradiating the solution for one minute. Morphological investigations of the active surface and of the cross‐sections of the fabricated membranes showed that the typical porosity of ultrafiltration membranes was obtained starting from solutions containing a low amount of crosslinker (10 wt%), which is consistent with the water flux values which were comparable to that of the pristine polysulfone membrane. High concentrations of crosslinker resin in the initial polymer dope produced denser membranes with lower permeability. High rejection of 27 nm particles (>90%) was measured for all samples having measurable flux. The addition of the crosslinker allowed one to obtain stability in various solvents without affecting the flux and rejection performance of the porous membranes. © 2016 Society of Chemical Industry     

Polymers of norbornenyl‐4‐phenol: Dissolution rate characteristics,positive tone photo‐patterning,and polymer properties

Vinyl addition norbornene polymers with phenol pendent groups are obtained by methanolysis of the 4‐acetoxyphenyl norbornene polymer. Thin films of this polymer blended with additives such as norbornene polymers with hexafluoroalcohol pendent groups and diazonaphthoquinone compounds result in linear dissolution in tetramethylammonium hydroxide developer. Good resolution, positive tone patterns are obtained from image‐wise exposure of thin films of blends of the diazonaphthoquinone additives with both phenol pendent norbornene homopolymer and with norbornene copolymers with both phenol and hexafluoroalcohol pendent groups. Properties such as transparency, dielectric constant, chemical, and thermal resistance were determined for cured copolymer compositions containing an epoxy crosslinker. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44952.