Polyfunctional Monomers Research Articles

Enhancement of graft yield and control of degradation during polypropylene maleation in the presence of polyfunctional monomer

AbstractFree‐radical initiated grafting of maleic anhydride (MAH)/polyfunctional acrylate (PFA) multimonomer system onto polypropylene (PP) via reactive extrusion was studied. The effects of PFA and initiator concentration on the grafting reaction were investigated. It was shown that PFA as a comonomer could greatly enhance MAH grafting degree, which increased monotonically as the molar ratio of PFA to MAH increased. The rheology test demonstrated that the viscosity of grafted PP was also promoted as more PFA was used. The formation of branched structure during the grafting process was proved by oscillatory shear rheological analysis. The mechanism of grafting in the presence of PFA was discussed, suggesting PFA had higher reactivity with PP macroradicals than MAH and therefore forming stabilized macroradicals, thus resulting in depression of β‐scission and favoring the formation of branched structure. Higher initiator concentration gave higher MAH grafting degree but more severe degradation. The mechanical properties of the grafted PP were comparable with those of unmodified PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The effects of electron beam irradiation on the thermal properties, fatigue life and natural weathering of styrene butadiene rubber/recycled acrylonitrile–butadiene rubber blends

The effects of electron beam (EB) irradiation on the thermal properties, fatigue life and natural weathering of styrene butadiene rubber/recycled acrylonitrile–butadiene rubber (SBR/NBRr) blends were investigated. The SBR/NBRr blends were prepared at 95/5, 85/15, 75/25, 65/35, or 50/50 blend ratios with and without the presence of a 3 part per hundred rubber (phr) of polyfunctional monomer, trimethylolpropane triacrylate (TMPTA). Results indicate that the crystallisation temperature ( T c) observed in polymeric blends is due to the alignment of polymer chains forming a semi-crystalline phase. Addition of TMPTA helps to align polymer chains through crosslinking. More crosslinking occurred between polymer blends with the help of TMPTA, upon irradiation. The improvement in fatigue life can also be associated with the stabilisation of SBR/NBRr blends upon irradiation and irradiation-induced crosslinking, which was accomplished with relatively low radiation-induced oxidative degradation in the presence of TMPTA. The tensile properties of both blends decreased over the periods of environmental exposure due to the effect of polymer degradation. After 6 months, the irradiated SBR/NBRr blends could not retain better retention [mainly with 25, 35 or 50 phr of recycled acrylonitrile–butadiene rubber (NBRr) particles] due to the samples becoming brittle over the long period of outdoor exposure.

Microstructure and properties of polypropylene/glass fiber composites grafted with poly(pentaerythritol triacrylate)

Isotactic polypropylene(PP)/glass fiber(GF) composites were modified by grafting polymerization of polyfunctional monomer, pentaerythritol triacrylate (PETA), in the presence of 2,5-dimethyl-2,5-di(tert-butylperoxy) hexane peroxide (DDHP) via melt extrusion. Fourier transform infrared spectroscopy (FTIR), melt strength test (MS), mechanical property test, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to characterize the microstructure and properties of the modified composites. The crystallization kinetics was investigated by Mo method while apparent activation energy of crystallization of the composites was determined by Kissinger method. The FTIR results showed that the acrylic polymers were grafted onto the polypropylene chains. The grafting made the melt strengths and the mechanical properties of the modified composites, and the interfacial adhesion between PP and glass fiber all enhanced. High melting and crystallization temperatures, high crystallization rate and large activation energy of crystallization were also obtained after grafting. In addition, the grafted acrylic polymers recovered the depressed crystallization of polypropylene and restrained α-β transition in fatigue experiment.

Effect of the Addition of Acrylic Monomers on Mechanical Properties of Patterns Applied in Negative-Type Photoresists

Typically, a negative-type photoresist consists of a polymer binder, polyfunctional monomer (or cross-linker), photo initiator, solvent, and additives. A series of acrylic monomers was prepared as cross-linkers using dipentaerythritol hexa-acrylate (DPHA) and blending monomers with n-butyl methacrylate (BuMA), benzyl methacrylate (BzMA), and acrylic-silica sol (Pro-1264), and the mechanical properties of patterns were studied. The elastic recovery and the compression of the patterns were measured using a dynamic ultra-micro-hardness tester. Patterns of the photo spacer were observed using a scanning electron microscope. Superior mechanical properties (elastic recovery, compression, and surface hardness) of the patterns and the optimum recipe could be obtained by adding 2 wt% of acrylic monomers (BuMA or BzMA or Pro-1264) to the photoresists when DPHA was fixed at 10 wt%. An inverted conical pattern was observed when 3 wt% of Pro-1264 was added to the photoresists when the transmittance of patterns worsened because of the low capacity of the interpenetration network.

Crosslinking polymerization of polyfunctional monomers by free radical mechanism

The crosslinked architectures based on diallyl maleate (DAM) obtained by suspension polymerization techniques have been studied. The influence of synthesis parameters on the structure of poly(diallyl maleate) [poly(DAM)] and copolymers of DAM with methyl methacrylate (MM) [poly(DAM-co-MM)] was also investigated. The effect of the diluents (n-butyl acetate or cyclohexanole) on the inner macroporous structure (apparent and skeletal density, pore volume, total porosity, cyclohexane uptake) has been studied. The experimental results showed that the values of the solvent uptake are strongly influenced by the diluent quantity as well as its solubility parameter.

The Effect of Electron Beam (EB) Irradiation in Presence of TMPTA on Cure Characteristics and Mechanical Properties of Styrene Butadiene Rubber/Recycled Acrylonitrile-Butadiene Rubber (SBR/NBRr) Blends

The effect of electron beam (EB) irradiation on the cure characteristics and mechanical properties of unirradiated and irradiated SBR/NBRr blends were investigated. The SBR/NBRr blends were prepared at 95/5, 85/15, 75/25, 65/35, and 50/50 blend ratio with and without the presence of a polyfunctional monomer, trimethylolpropane triacrylate (TMPTA). Results indicated that the scorch time t2, cure time t90 and minimum torque (ML) of irradiated SBR/NBRr blend decreased, but the maximum torque (MH) particularly at 35 and 50 phr of NBRr (recycled NBR) increased with the presence of TMPTA. The stress at 100% elongation (M100), hardness, cross-linking density and tensile strength (particularly after 15 phr of NBRr content) of irradiated SBR/NBRr blends increased after irradiation but the elongation at break (EB) and resilience decreased. The irradiated SBR/NBRr blends showed lower thermal stability than non-irradiated blends. Scanning electron microscopy proved the enhancement in tensile strength when more NBRr were added in SBR matrix where the irradiated surfaces demonstrate more irregularity with increasing crack branching (fracture planes are located at different heights) due to the increased of cross-linked density.

Influence of polyfunctional monomer on melt strength and rheology of long‐chain branched polypropylene by reactive extrusion

AbstractLong chain branching (LCB) were added to linear polypropylene (PP) using reactive extrusion in the presence of selected polyfunctional monomers (PFMs) and a peroxide of dibenzoyl peroxide (BPO). Fourier Transformed Infrared spectra (FTIR) directly confirmed the grafting reaction occurred during the reactive extrusion process. Various rheological plots including viscosity curve, storage modulus, Cole‐Cole plot, and Van‐Gurp plots, confirmed that the LCB structure were introduced into modified PPs skeleton after modification. In comparison with linear PP, the branched samples exhibited higher melt strength, lower melt flow index, and the enhancement of crystallization temperature. The LCB level in modified PPs and their melt strength were affected by the type of PFM used and could be controlled by the PFM properties and structure. PFMs with lower boiling points, such as 1, 4‐butanediol diacrylate (BDDA), could not produce LCB structure in modified PP skeleton. The shorter molecular chain bifunctional monomers, such as 1,6‐hexanediol diacrylate (HDDA), favored the branching reaction if their boiling points were above the highest extrusion temperature. And some polar groups, such as hydroxyl, in the molecule of PFM were harmful to the branching reaction, which might be attributed to the harm of the polarity of groups to the dispersion of PFM in PP matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Rheology and melt strength of long chain branching polypropylene prepared by reactive extrusion with various peroxides

AbstractLong Chain Branching Polypropylenes were prepared in an extruder by a melt grafting reaction in the presence of various peroxides and a polyfunctional monomer of 1,6‐hexanediol diarylate. Fourier Transformed Infrared spectra and the rheological characteristics indicated that the grafting reaction added long branched chains to linear polypropylene (PP). In comparison to the initial PP, the branched samples exhibited higher melt strength, lower melt flow index, and enhancement of crystallization temperature. The branching number of the modified samples agreed well with their melt viscoelasticity and the improved degree of their melt strength. The branching level in modified PPs could be controlled by the property and structure of the peroxide used. Peroxides with lower decomposition temperature and more stable radicals after decomposition promoted the branching reaction, leading to the modified PPs with higher branching level and melt strength. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

UV-curable siloxane-acrylate gel-copolymer electrolytes for lithium-based battery applications

Thermo-set membranes prepared by free-radical photo-polymerisation (UV-curing) could be an interesting alternative to the existing Li-ion battery polymer electrolytes. UV-curing takes place at room temperature and it is based on initiating a chemical polymerisation inside a liquid poly-functional monomer, containing a proper photo-initiator, using direct UV-irradiation to create a highly cross-linked solid film. The present communication illustrates the results obtained from the investigation of a class of polymeric networks prepared by incorporating siloxane-based monomers into a methacrylic-based polymer matrix. The gel-copolymer membranes were obtained in the form of flexible, easy to handle, translucent films by UV-irradiation of a mixture of monomers in the presence of a radical photo-initiator with the in-situ addition of an EC/DEC solution. The polymer electrolyte was prepared by swelling the obtained membrane in a LiTFSI-EC-DEC solution. The chemical and structural properties were characterised by real-time FT-IR, TGA, DSC, and their surface characteristics were assessed by dynamic contact-angle measurements. Electrochemical tests on ionic conductivity, stability and cyclability in lithium cells pointed out the importance of the co-polymerisation in the presence of siloxane acrylates which improved the interfacial properties of the gel-copolymer membranes. Good values of ionic conductivity were obtained even at ambient temperature.

Polymer networks with antibacterial activity by UV photopolymerization

AbstractThe crosslinking by radical UV photopolymerization of mixtures of acrylic oligomers added with 2,4,4′‐trichloro‐2′‐hydroxydiphenyl ether (TCDPE) allows to obtain polymer films which perform like hygienic coatings. The release of the bioactive compound from two types of acrylic networks obtained by UV crosslinking of polyfunctional monomers, namely, epoxy‐based and urethane‐based diacrylic oligomers, has been investigated. The photopolymerization process was influenced by biocide presence only at high biocide concentration, where the plasticizing effect of the biocide increased the double bond conversion. The kinetic curve of the photopolymerization was fitted by an Avrami‐like equation and the release of TCDPE from the networks into solutions of ethanol–water of different compositions was discussed on the base of the Fick's diffusion equation. The antimicrobial activity of the UV photopolymerized film has been tested by putting the coatings in contact with two types of colony‐forming bacteria, the Escherichia coli (Gram negative) and the Staphylococcus aureus (Gram positive). Strong hygienic performances toward the tested pathogens were observed for the urethane and epoxy films containing TCDPE in quantities as low as 0.1 wt %. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Biobased step-growth polymers in powder coating applications

Co- and terpolyesters based on 1,4:3,6-dianhydro-d-glucitol (isosorbide), 1,4:3,6-dianhydro-l-iditol (isoidide) and succinic acid were evaluated for their applicability in solvent-cast and powder coatings. These biobased polyesters have functionalities and Tg values in the appropriate range for such applications and were cross-linked using conventional curing agents. Introduction of poly-functional monomers such as glycerol and citric acid led to coatings with enhanced performance with respect to mechanical and chemical resistance, compared to formulations based on linear polymers. The curing behavior of these systems was investigated with DSC and rheological experiments. Formulations containing citric acid-modified polyester resins showed rapid curing, probably facilitated by anhydride formation at the chain ends. Hydroxy- as well as carboxylic acid-functional 1,4:3,6-dianhydrohexitol-based polyesters proved to be suitable materials for coating applications with respect to solvent resistance, impact resistance and hardness, with performance comparable to commercially available systems. Accelerated weathering experiments showed that functional groups such as hydroxyl groups, carboxylic acids, anhydrides and peroxides are formed during UV-exposure. The weathered coatings have reduced impact stability. On the other hand, the appearance of the coatings does not change significantly. Isosorbide-based coating systems appear to have similar weathering resistance as conventional terephthalic acid-based poly(ester urethane) coatings.

Structure and Properties of Reactive Extruded Ethylene-block-co-Polypropylene: Influence of Dicumyl Peroxide and Divinylbenzene

The reaction of an ethylene-block-co-polypropylene (co-PP) with a polyfunctional monomer—divinylbenzene (DVB)—in the presence of dicumyl peroxide (DCP) was performed in a single screw extruder. It was found that the chain structure of co-PP was significantly influenced by the DVB concentration when the DCP content was fixed. Without DVB, degradation of co-PP chains, induced by DCP, mainly occurred. But when DVB was incorporated, reactions of crosslinking and branching prevailed in the system. The crystallization temperature of the modified co-PP was enhanced and the number of spherulites was increased, accompanied with a decrease of the spherulite size, due to the branched and crosslinked structure. The essential work of the fracture (EWF) method was adopted to characterize the fracture performance of the modified co-PP. The specific essential work of fracture, we, first decreased gradually to a minimum, and then climbed with increasing DVB concentration, which might be attributed to the variations of the length of the DVB segment (LDS) acting as the crosslinking node and the spherulite size of co-PP. The specific, nonessential work of fracture, β wp, of the modified co-PP was elevated to some extent with an increasing concentration of DVB. It was speculated that the crosslinked and branched structures favored stress transfer among molecular chains and spherulites, which was beneficial to the enlargement of the plastic deformation zone.

Enhanced radiation crosslinking of carboxymethylated chitosan in the presence of acids or polyfunctional monomers

Carboxymethylated chitosan (CMCt) hydrogels were synthesized by γ-ray radiation-induced crosslinking in the presence of acids or polyfunctional monomers. Compared with that of CMCt hydrogels synthesized without additives, the gel fraction was improved and the gelation dose was decreased obviously after incorporating acids or polyfunctional monomers into CMCt hydrogels. The diffusion behavior of water in the CMCt gels prepared at different conditions was Fickian diffusion, and the swelling of the CMCt gels displayed characteristic pH sensitivity, which was analyzed by fluorescence molecular probes. Preliminary mechanism of radiation-induced crosslinking of CMCt in the presence of acids or polyfunctional monomers was discussed based on the FTIR and sol–gel analysis. Furthermore, it was found that CMCt hydrogels were hydrodegradable with high temperature (>60 °C), and incorporating polyfunctional monomers into the CMCt hydrogels also could improve the thermal stability of the CMCt hydrogels obviously.

Radiation‐induced crosslinking and mechanical properties of blends of poly(lactic acid) and poly(butylene terephthalate‐co‐adipate)

AbstractBlends of poly(L‐lactic acid) (PLLA) and poly (butylene terephthalate‐co‐adipate) (PBTA) were prepared at ratios of 50 : 50, 60 : 40, and 80 : 20 by melt blending in a Laboplastomill. Improved mechanical properties were observed in PLLA when it was blended with PBTA, a biodegradable flexible polymer. Irradiation of these blends with an electron beam (EB) in the presence of triallyl isocyanurate (TAIC), a polyfunctional monomer, did not cause any significant improvement in the mechanical properties, although the gel fraction increased with the TAIC level and dose level. Irradiation of the blends without TAIC led to a reduction in the elongation at break (Eb) but did not show a significant effect on the tensile strength. Eb of PBTA was unaffected by EB radiation in the absence of TAIC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Preparation and properties of nano-silica modified negative acrylate photoresist

A series of silica modified photoresists had been successfully developed through incorporation of a particular nanoparticles suspension. Free radical polymerization was employed to synthesize the binder, an acrylate copolymer resin of benzyl methacrylate, methacrylic acid and 2-hydroxyethyl methacrylate, of the photoresist. The acid value, viscosity, molecular weight and thermal properties of the formed binders were measured. Then, surface-modified silica particles prepared by the sol–gel method were introduced to the photoresist. Because the modified silica particles contained considerable amount of reactive double bonds (C C) on their surfaces, they would react with the polyfunctional monomers in the photoresist to form an organic–inorganic nanohybrid. Fourier transform infrared spectrometer was used to analyze the evolution of chemical bonds at various stages of the preparation process. Thermal analyses including thermal gravimetric analyzer, differential scanning calorimeter and thermo-mechanical analyzer were used to evaluate the level of enhancement on thermal and dimensional stabilities of the photoresist due to silica incorporation.

Crosslinking of Polyolefin Foam. III. Increasing Low-Density Polyethylene Foam Production Efficiency by Incorporation of Polyfunctional Monomers

The effect of introducing polyfunctional monomers into dicumyl peroxide (DCP) crosslinking systems for low-density polyethylene (LDPE) is considered. Effects are characterised as a function of relative concentrations in solid, melt and foamed states. The monomers selected were diallyl phthalate (DALP), trimethylolpropane trimethacrylate (TMPTMA) and triallyl cyanurate (TAC). It is shown that TAC promotes network formation more efficiently than TMPTMA and DALP allowing a considerable reduction in DCP concentration to attain a specific gel content. A TAC concentration of approximately 0.5% was most cost-effective. Crosslinking promotion efficiency was shown to be in the order TAC > DALP > TMPTMA. Polyfunctional monomers containing allyl groups appeared to be significantly more effective than methacrylates and the efficiency improved with increasing functionality. Compression moulding of LDPE foams of similar density showed that the cycle time could be reduced using a DCP/TAC system compared with DCP alone.

Synthesis and study of cooligomers of p-isopropenylphenyl λ-chlorobutyrate with styrene

Free-radical cooligomerization of a new polyfunctional monomer, p-isopropenylphenyl λ-chlorobutyrate, with styrene was studied.

Combined Effects of Microwaves, Electron Beams and Polyfunctional Monomers on Rubber Vulcanization

Thispaperpresents comparative results obtained by conventional vulcanization with benzoyl peroxide (CV-BP), separate electron beam vulcanization (EB-V) and simultaneous electron beam and microwave vulcanization (EB+MW-V) applied to two kind of rubber samples: EVA (ethylene vinyl acetate) rubber-sample (EVA-sample) and EPDM (ethylene-propylene terpolymer) rubber-sample (EPDM-sample). The EVA-samples contain 61,54% EVA Elvax 260, 30.77% carbon black, 1.85% TAC (triallylcyanurate) polyfunctional monomer and 5.84% filler (zinc oxide, stearic acid, polyetylen glycol and antioxydant). The EPDM-samples contain 61.54% EPDM Nordel 4760, 30.77% carbon black, 1.85% TMPT (trimethylopropane trimethacrylate) polyfunctional monomer and 5.84% filler (zinc oxide, stearic acid, polyetylen glycol and antioxydant). The rubber samples designedfor different vulcanization methods were obtainedfrom raw rubber mixtures, as compressed sheets of 2 mm in the polyethylene foils to minimize oxidation. For EB and EB+MW treatments the sheets were cut in rectangular shape 0.15 x 0.15 m2. The physical properties of samples obtained by CV-BP, EV-V and EB+MW-V methods were evaluated by measuring the tearing strength, residual elongation, elongation at break, tensile strength, 300% modulus, 100% modulus, elasticity and hardness. The obtained results demonstrate an improvement of rubber several properties obtained by EB and EB+MW processing as compared to classical procedure using benzoyl peroxide.

Carcinogen adsorbent prepared from DNA complex by gamma-ray irradiation

The effects of gamma-ray irradiation on aqueous solutions of chub mackerel chromatin, salmon milt DNA with CoCl2, mixtures of DNA with Type A gelatin, bovine serum albumin (BSA), CM-chitosan, carboxymethyl cellulose (CMC) and Catinal (hydroxyethyl-cellulose, O-[2-hydroxy-3-(trimethyl ammonio)-propyl], chloride) and DNA in the presence of polyfunctional monomers with the aim to insolubilize DNA for preparing a novel carcinogen adsorbent have been studied. Among those, precipitates or inhomogeneous gel consisting of cross-linked DNA were prepared from the samples of aqueous DNA in the presence of CoCl2 at low irradiation dose, around 10 Gy, and bulk homogeneous gels were successfully prepared from aqueous mixtures of DNA with gelatin, BSA, CMC and Catinal in a limited range of irradiation doses. Gel fraction and swelling ratio of the gels were measured. Adsorption of a carcinogen, acridine orange, was also examined for the gels. From the experimental results, the optimum conditions for preparing insolubilized homogeneous DNA gels were determined.

Influence of radiation temperature on the crosslinking of nitrile rubber by electron beam irradiation

Nitrile rubber with 18% acrylonitrile content in presence and absence of polyfunctional monomers like trimethylolpropane triacrylate (TMPTA), tripropyleneglycol diacrylate (TPGDA), tetramethylolmethane tetraacrylate (TMMT) and m-phenylene bismaleimide was subjected to electron beam irradiations at different temperatures. The structural changes with different doses of radiations were investigated with the help of FTIR spectroscopy (in the ATR mode), dynamic mechanical thermal analysis and sol–gel analysis. There was a decrease in the concentration of olefinic groups for this elastomer on radiation at high temperature as compared to the room temperature. The increase in crosslinking at elevated temperature was also revealed by the increase in % gel content and dynamic storage moduli with radiation dose. The lifetime of spurs, an important criterion for overlapping of spurs, was determined for both grafted and ungrafted nitrile rubber using a mathematical model. The ratio of scissioning to crosslinking for nitrile rubber was determined using Charlesby–Pinner equation. The mechanical properties were studied and the tensile strength was found to increase with grafting of polyfunctional monomers on irradiation at high temperature.