Radiation vulcanization of natural rubber with polyfunctional monomers

This study presents the effect of the polyfunctional monomers (PFMs) triallylcyanurate (TAC), triallylisocyanurate (TAIC), trimethylolpropane trimethacrylate (TMPT), ethylene glycol dimethacrylate (EDMA) and zinc diacrylate (ZDA) on the mechanical properties of natural rubber (NR) crosslinked by electron beam (EB) processing. Dependence of mechanical properties and crosslink density on irradiation dose was determined from a dose range of 50 to 200 kGy. The control blends, obtained with benzoyl peroxide as curing agent, were prepared by blending on a laboratory roller and the control sample curing was accomplished on hydraulic press at 160 °C. The results showed an increase in mechanical properties and crosslink density due to the introduction of PFMs. Also, based on the comparison between EB irradiation and dibenzoyl peroxide vulcanization efficiency, the experimental results show that EB irradiation gave the best results.     

Effects of High-Energy Electron Beam Irradiation on the Properties of Flame-Retardant HDPE/EVA/Mg(OH)2 Composites

The mechanical properties of flame-retardant high-density polyethylene/ethylene vinyl-acetate copolymer/magnesium hydroxide (HDPE/EVA/Mg(OH)₂) composites for cable materials are usually poor due to the high loading of the filler. In this study, high-energy electron beam irradiation was applied to HDPE/EVA/Mg(OH)₂ composites in the presence of triallylisocyanurate, an irradiation sensitizer. The effects of high-energy electron beam irradiation on the properties of irradiated HDPE/EVA/Mg(OH)₂ composites were investigated through the measurements of gel content, limiting oxygen index, tensile testing, thermogravimetric analysis, and scanning electron microscope. The results showed that the thermal, mechanical and flame-retardant properties of the HDPE/EVA/Mg(OH)₂ composites were improved by using high-energy electron beam irradiation.     

Effect of surfactant and electron treatment on the electrical and thermal conductivity as well as thermal and mechanical properties of ethylene vinyl acetate/expanded graphite composites

This study presents an investigation of the electrical and thermal conductivities of composites based on an ethylene vinyl acetate (EVA) copolymer matrix and nanostructured expanded graphite (EG). To improve the EG dispersion in EVA, EG sheets were modified by treating them with the anionic surfactant sodium dodecyl sulphate (SDS) in water. The modified SDS‐EG platelets, after being filtered and dried, were melt‐mixed with EVA to prepare the composites. Finally, both EVA/EG and EVA/SDS‐EG composites were subjected to 50 kGy electron beam (EB) irradiation. SEM images confirm that the irradiated EVA/EG samples had improved interfacial adhesion, while the irradiated EVA/SDS‐EG samples showed even better interfacial adhesion. The gel contents of the irradiated samples without and with SDS treatment increased with increase in EG loading. The EVA/EG composites exhibited a sharp transition from an insulator to a conductor at an electrical percolation threshold of 8 wt %, but with SDS‐EG the electrical conductivity was extremely low, showing no percolation up to 10 wt % of filler. The EB irradiation had no influence on electrical conductivity. The thermal conductivity linearly increased with EG content, and this increase was more pronounced in the case of SDS‐EG, but decreased after EB irradiation. The thermal properties were little influenced by EB irradiation, while better polymer–filler interaction and better filler dispersion as a result of SDS treatment, and the EB irradiation initiated formation of a cross‐linked network, had a positive effect on the tensile properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42396.     

电子束辐照交联PVC/EVA共混物的研究

以丙烯酸酯类多官能团不饱和单体为交联敏化剂，采用电子束对聚氯乙烯(PVC)与乙烯—酸酸乙烯共聚物(EVA)的共混物进行辐照交联。研究了VA质量分数、交联敏化剂种类及用量、辐照剂量、EVA用量对共混物凝胶质量分数、力学性能以及热延伸性能的影响。结果表明：EVA共聚物能促进PVC的辐照交联，增加共混体系的凝胶质量分数，改善其力学及热延伸性能；EVA共聚物中VA质量分数增大，共混体系的凝胶质量分数增大，力学及热延伸性能改善更明显。     

Vinyl acetate content and electron beam irradiation directed alteration of structure,morphology, and associated properties of EVA/EPDM blends

A series of ethylene vinyl acetate/ethylene–propylene diene elastomer (EVA/EPDM) blends with four types of EVAs with various vinyl acetate (VA) content, are prepared without and with crosslinker, trimethylol propane triacrylate (TMPTA). These are irradiated by electron beam (EB). As the VA content increases, the gel content, i.e., degree of crosslinking of EVA/EPDM blends, is increased. With increase in VA content, the modulus and tensile strength are decreased but elongation at break is increased due to increase in amorphousness. On EB irradiation, modulus and tensile strengths are increased but at the cost of elongation at break. Crystallinities of all blends are decreased with increase in VA and EB crosslinking. The thermal stability of EVA/EPDM blend is decreased with increase in VA content but increased after EB irradiation. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) show that with increase in VA content the miscibility of two polymers keeps on increasing, which even become more after EB irradiation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43468.     

Physicochemical properties of irradiated and loaded LDPE films with polyfunctional monomers

Polyfunctional monomers (PFMs), namely, trimethylol propane trimethacrylate (TMPTMA), trimethylol propane triacrylate, ethylene glycol dimethacrylate, and diethylene glycol diacrylate were blended with low‐density polyethylene (LDPE) and exposed to different doses of EB irradiation. Fourier transform infrared and ultraviolet and UV–vis spectroscopy of the unirradiated, irradiated, unloaded, and PFMs‐loaded LDPE films were studied under various irradiation doses up to 300 kGy. The degree of crosslinking and oxidative degradation, as measured by the spectroscopic parameters, were dependent on both the irradiation dose and the type of loaded PFMs. For all of the loaded monomers, the extent of crosslinking increased at different rates as a function of irradiation dose. TMPTMA monomer was the most efficient in enhancing the crosslinking of LDPE films compared to the other loaded monomers. However, the unloaded LDPE film showed the least extent of crosslinking. In addition, the EB‐radiation‐induced changes, such as trans‐vinylene formation, a decrease in vinyl and vinylidene unsaturation; and carbonyl double‐bond formation and change in crystallinity were correlated. The importance of these results on the prediction of the role of polyfunctional monomers in the production of crosslinked polymers is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2025–2035, 2003     

Synthesis of substituted fatty oxathiolanes and thioethers from an allylic oxo fatty acid ester

Substituted oxathiolane and thioether derivatives have been synthesized from an allylic oxo fatty acid ester. The reaction of methyl 4-oxo-trans-2-octadecenoate with 3-mercaptopropan-1,2-diol (1-thioglycerol) affords methyl 4-(3′-hydroxymethyl-1′,4′-oxathiolane)-2(3)-(O-mercaptopropan-1″,2″-diol)-octadecanoate (II), methyl 4-oxo-2(3)-(O-mercaptopropan-1′,2′-diol)-octadecanoate (III), methyl 4-(3′-hydroxy-l′,5′-oxathiane)-2 (3)-(S-mercaptopropan-1″,2″-diol)-octadecanoate (IV), methyl 4-oxo-2(3)-(S-mercaptopropan-1′, 2′diol)-octadecanoate (V) and methyl 4-(3′-hydroxymethyl-1′, 4′-oxathiolane)-2(3)-(S-mercaptopropan-1″, 2″-diol)-octadecanoate (VI). Structures of the individual reaction products have been established on the basis of spectral data and microanalyses.     

Investigation of flame retardancy in EVA

Strategies for fire retarding ethylene vinyl acetate copolymer (EVA) in electrical cable insulation by means of halogen‐free systems were explored. Attempts to increase char yield, promoting crosslinking of double bonds either created by deacetylation of vinyl acetate units or by dehydrogenation of ethylene sequences in EVA were carried out. Pd catalysed dehydrogenation was unsuccessful, whereas oxidative dehydrogenation seems promising as shown by using thermally decomposing KMnO₄. On the other hand organic peroxides failed to increase the rate of crosslinking of deacetylated units. Better results were obtained with the addition to EVA of an intumescent system which is a combination of melamine phosphate and phosphate‐phosphonate substituted trimethylamine. EVA was shown to play a substantial role in the intumescence phenomenon. Copyright © 2000 John Wiley & Sons Ltd.     

Phase transition in swollen gels

Summary The dynamic mechanical behaviour of 4% aqueous solutions and networks of poly (N, N-diethylacrylamide) and copolymers of diethylacrylamide with sodium methacrylate (MNa) (molar ratio x_MNA=0–0.05) swollen in water was measured in the temperature range 20–80 °C. With increasing temperature, at T_c polymer chains collapse from random coil to more compact globular conformations. While in the region of coil conformations (T > T_c) the mechanical behaviour of solutions has a liquid-like character (the loss modulus G″ is higher than the storage modulus G′ for a constant frequency ω=1 Hz), in the region of globular conformations (T > T_c) a heterogeneous physical network is built in solutions, and the mechanical behaviour has a solid-like character (G′ > G″). In networks the collapse is reflected in an increase of storage modulus G′; the magnitude of this increase decreases with ionization. The dependence of the loss modulus G″ on the temperature of solutions and networks allows us to conclude that the magnitude of losses in the collapsed state is affected rather by x_MNa (the modulus G″ increases with increasing ionization) than by the heterogeneous structure of the samples.     

Derivatization of keto fatty acids: V. Synthesis and characterization of 1,3-dioxolanes

The synthesis of substituted 1,3-dioxolanes from oxo fatty acid esters using 1,2-propanediol is described. This reagent, besides forming dioxolanes, also converts the methyl ester to the 2′-hydroxy propyl ester. Methyl 10-oxoundecanoate gives 2′-hydroxy propyl 10-(2″-methyl ethylene dioxolane) undecanoate (Ia, 75%) as a major product. Methyl 9-oxooctadecanoate reacts similarly and yields 2′-hydroxy propyl 9-(2″-methyl ethylene dioxolane) octadecanoate (IIb, 60%), along with the minor products (IIa, IIc). Methyl 2-oxooctadecanoate, after prolonged refluxing, affords only 2′-hydroxy propyl 2-(2″-methyl ethylene dioxolane) octadecanoate (IIIa) in 70% yield. Structures of each reaction product were established on the basis of elemental analysis, IR, NMR and a study of mass spectrometry.     

Effect of interphase interactions on the dielectric behaviour of polycarbonate/poly(styrene-co-acrylonitrile) blends

Summary Frequency and temperature dependences of the complex permittivity ɛ^* (=ɛ′−i ɛ″, ɛ′ is the real and ɛ″ imaginary component, respectively) were investigated for blends of polycarbonate/poly(styrene-co-acrylonitrile) (PC/SAN). In the blends, two α-processes corresponding to the main transitions of PC and SAN were found; for SAN at concentrations c _SAN≥ 20 wt% and for PC for c _PC≥ 40 wt%. The Havriliak-Negami shape parameters describing the frequency dependence of ɛ′ and ɛ″ are virtually independent of temperature and composition. Slight shift of temperature or frequency positions of α-processes found for blends from those found for neat polymers with composition of blends indicated partial miscibility of components. The concentration dependences of ɛ′ and ɛ″ at low frequencies and high temperatures could be described with the B?ttcher equation from which it followed that percolation threshold takes place for SAN inclusions at c _SAN≈ 30 wt%. Both the reduced dielectric strength ΔɛT and the reduced Onsager term O _t/c _SAN (or O _t/c _PC) in dependence on the blend composition could be qualitatively described by the B?ttcher equation as well. Received: 5 January 2000/Revised version: 22 March 2000/Accepted: 22 March 2000     

Reactive compatibilization of the poly(butylene terephthalate)–EVA blend by maleic anhydride. II. Correlations among gel contents,grafting yields,and mechanical properties

Correlations among the degree of crosslinking of ethylene vinyl acetate copolymer (EVA), the grafting yield of maleic anhydride (MAH) onto EVA, and the mechanical properties of the blends of poly(butylene terephtalate) (PBT) with EVA‐g‐MAH were investigated. The EVA was functionalized by melt grafting reaction in the presence of MAH and dicumyl peroxide (DCP) using a plasticorder. The grafting yield of MAH was increased by increasing the concentration of MAH and DCP. The flexural strength of PBT–EVA‐g‐MAH blends depends on both the grafting yield of MAH and the degree of crosslinking of EVA, while the crosslinked parts of EVA‐g‐MAH hindered rather than improved the tensile strength regardless of the increase of the grafting yield of MAH. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1305–1310, 2003     

Effect of electron beam irradiation and vinyl acetate content on the physicochemical properties of LDPE/EVA blends

The radiation‐induced crosslinking, compatibility, and surface modification of low density polyethylene/ethylene vinyl acetate blends (LDPE/EVA) were investigated. The structural and physical properties were characterized in terms of gel content, hot set, mechanical properties, contact angle, and surface free energy. The highest crosslink density was obtained at 20 wt % of EVA. Gel content of LDPE/EVA blends was increased with increasing irradiation dose, vinyl acetate (VA), and EVA contents. The hot set results are consistent with the gel content data. Mechanical testing showed that the tensile strength of samples increased with increasing irradiation dose up to 180 kGy, whereas the elongation at break was decreased with increasing irradiation dose. Contact angle measurements showed that the surface hydrophillicity of LDPE blend was increased with increasing irradiation dose and contents of both VA and EVA. The surface free energy was greatly dependent on irradiation dose and content of both VA and EVA. The total surface free energies of different LDPE formulations were in the range 17.25–32.51 mN/m, in which the polar (^pσ) and disperse (^dσ_s) values were within the range 16.52–26.6 and 0.9–5.91 mN/m, respectively. In conclusion, electron beam irradiation and blending LDPE with EVA improved the wettability or adhesion properties of LDPE/EVA blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of organic peroxides on the morphology and properties of EVA/Cloisite 15A nanocomposites

This article describes the effect of the presence of organic peroxides on the morphology and properties of ethylene vinyl acetate copolymer (EVA)/Cloisite 15A nanocomposites. The results show that the presence of dicumyl peroxide (DCP) or dibenzoyl peroxide (DBP) during the preparation of EVA/Cloisite 15A clay nanocomposites gives rise to intercalated, exfoliated, or mixed morphologies, which are not normally observed for samples prepared in the absence of organic peroxides. In the absence of clay, both DCP and DBP initiate de‐acetylation and chain scission of EVA chains, but the influence of DBP is more pronounced. The presence of clay inhibits the initiation of EVA degradation by DCP free radicals, which can be observed in the higher tensile strength values for DCP treated samples, as well as in the de‐acetylation step in the TGA curves. DBP has a more significant influence on the polymer degradation, and this gives rise to reduced thermal stability and mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dynamic mechanical study of the transition from swollen particles to hydrogel caused by neutralization

Summary The copolymer of 2-(2-carboxybenzoyloxy)ethyl methacrylate (CEM) with butyl methacrylate (BMA) (BMA/CEM = 40/60 wt.) and terpolymers CEM/BMA/ 2-hydroxyethyl methacrylate (HEMA) ((BMA + HEMA)/CEM = 40/60 wt.; HEMA/BMA = 35/5, 30/10, 20/20 and 10/30) were prepared by emulsion radical copolymerization in water in the presence of sodium dodecyl sulfate and their dynamic mechanical behaviour was investigated as a function of the degree of neutralization α. Main attention was devoted to the transition from swollen particles to physical gel with increasing degree of neutralization and to the structure of formed hydrogels. From the results it followed: (a) the transition from swollen particles to the gel state occurs in a narrow neutralization interval at α∼ 0.45 for BMA/CEM copolymer; increasing the HEMA content shifts the transition to lower α values; (b) with increasing shear strain γ, the hydrogels passed from the gel to liquid state and this transition at the critical strain γ_c, was reversible; (c) junctions in the gel state are probably formed by the hydrophobic interactions of the ends of CEM units which form clusters and the junction concentration is independent of the HEMA content and degree of neutralization α; (d) increasing degree of neutralization α and the HEMA content (increasing polarity of the system) stabilizes the junctions and the critical γ_c values increase; (e) the values of the low-strain storage G′₀ and loss G″₀ moduli together with critical strains γ_c did not depend on angular frequnecy ω in the interval 10⁻¹− 10 rad/s. Received: 5 January 2000/Accepted: 23 May 2000     

Soil wetting agents from fatty nonionic tertiary amides: “Aromatic adducts without aminoester”

Tertiary amides RCONR'K, where K is a hydroxy function and R,R′ are aliphatic and/or aromatic groups, were oxyethylated to adducts containing 5, 10, 15, and 20 moles of ethylene oxide. The hydroxy function K was derived from CH₂CHR″OH,-(CH₂)_yOH, or (CH₂CH₂O)_zH, where R″ is methyl, ethyl, or octyl, y is 4 or 6 methylenes, and z is 2 or 3 ethoxy groups. Structural variations in R,R′ and K permitted the oxyethylation of aromatic amides with minimal aminoester formation. When K was diethoxy and R,R′ were linear aliphatic groups, no aminoester accompanied oxyethylation. Minimal aminoester formed when R,R′ were mixed aliphatic/ aromatic or when R was phenethyl and R′ aromatic. For aromatic amides where K was dior triethoxy, large aminoester concentrations accompanied oxyethylation. For aromatic amides where K was (CH₂)₄OH or (CH₂)₆OH smaller aminoester concentrations were observed. For branched alphatic amides where R″ is methyl, ethyl, or octyl, aminoester concentration remained at the level found where R″ is hydrogen. The increasing size of R″ decreased solubility and Draves wetting times. The adducts of this study were wetting agents for Idylwild hydrophobic soil and cotton skeins. The availability of aromatic substrates should permit formulation of soil wetting agents with greater stability to biodegradation than would be expected with aliphatic substrates.     

Degradation of poly(D,L‐lactic acid)‐b‐poly(ethylene glycol)‐b‐poly(D,L‐lactic acid) copolymer by electron beam radiation

This article investigates the effects of electron beam (EB) radiation on poly(D ,L ‐lactic acid)‐b‐poly (ethylene glycol) copolymer (PLA‐b‐PEG‐b‐PLA). The copolymer films were EB irradiated at doses from 0 to 100 kGy. The degradation of these films was studied by measuring the changes in their molecular weight, mechanical and thermal properties. The dominant effect of EB radiation on PLA‐b‐PEG‐b‐PLA is chain‐scission. With increasing irradiation dose, recombination reactions or partial crosslinking may occur in addition to chain scission. The degree of chain scission G_s and crosslinking G_x of sample are calculated to be 0.213 and 0.043, respectively. A linear relationship is also established between the decreases in molecular weight with increasing irradiation dose. Elongation at break of the irradiated sample decreases significantly, whereas its tensile strength decreases slightly. The glass transition temperature (T_g) is basically invariant as a function of irradiation dose. Thermogravimetric analysis shows that its thermal stability decreases with increasing dose. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of electron beam irradiation on (waste tire dust)‐filled ethylene vinyl acetate in the presence of bisphenol a diglycidyl ether

The effect of bisphenol A diglycidyl ether (BADGE) and electron beam (EB) irradiation on the properties of waste tire dust (WTD) ‐filled ethylene vinyl acetate (EVA) has been studied. The EVA/WTD ratio was fixed to 80:20, whereas the BADGE concentration varied from 1 to 5 wt%. The samples were then irradiated using a 3.0‐MeV EB machine at 50 kGy to 200 kGy at increments of 50 kGy. All the samples were subjected to various mechanical, physical, and thermal tests. Prior to irradiation, the mechanical properties of the composites show a gradual decrease with increasing BADGE concentration. Such observation is attributed to the plasticizing effect of the BADGE, as indicated by the reduction in mixing torque and a 14% increase in the elongation at break with the addition of 5 wt% BADGE. Results of gel fraction indicated that BADGE did not accelerate the irradiation‐induced crosslinking of EVA/WTD composites. The scanning electron micrographs and tan δ curves of EVA/WTD composites showed evidence that the addition of BADGE and EB irradiation of the EVA/WTD improves the compatibility of the composite. The overall results revealed that the irradiated EVA/WTD composite without BADGE gives a better enhancement in mechanical properties compared with the composites incorporated with the BADGE. J. VINYL ADDIT. TECHNOL., 23:172–180, 2017. © 2015 Society of Plastics Engineers     

Polymer diffusion and mechanical properties of films prepared from crosslinked latex particles

Wedescribe energy transfer (ET)measurements to follow polymer diffusion, as well as oscillatory dynamic mechanical measurements and tensile measurements, on films prepared from structured and unstructured latex particles consisting of a copolymer of butyl methacrylate and butyl acrylate with a T_g of 20°C. Structure was introduced in the form of a low level (1 mol%) of crosslinking, using seeded semi-continuous emulsion polymerization to control the locus of the crosslinking agent in the particles. Linear dynamic mechanical measurements showed the G′ and G″ were sensitive to the particle morphology, with particular sensitivity exhibited by the elastic modulus G′. The tensile properties were less sensitive to particle morphology; sufficient polymer diffusion occurs during film formation for the films to acquire strength and toughness. As expected, crosslinking increases strength but decreases elongation to break. Some interesting compromises could be found through control of the location of the crosslinked regions of the film. Dept. of Chemistry, 80 St. George St., Toronto, Ont., Canada M5S 3H6. F-27470 Serquigny, France.     

Violation of the power-law dynamic mechanical behaviour at the gel point threshold in non-stoichiometric epoxide systems

Summary The dynamic mechanical behaviour of fully cured off-stoichiometric epoxy systems prepared from poly(oxypropylene)diamine (Jeff D-400) or -triamine (Jeff T-403) and diglycidyl ether of Bisphenol A (DGEBA) with initial ratios of reactive amine (NH₂) and epoxide (E) groups, r _H= (2[NH₂])/[E] ranging from 2.4 to 4.3 was investigated in the gelation threshold region. The evolution of the dynamic behaviour of two stoichiometric samples with r _H= 1 with reaction time, t _r , was also studied. The critical ratios for gelation, r ^c _H, of fully cured samples were determined from extraction experiments (r ^c _H= 2.54 for Jeff D-400/DGEBA and r ^c _H= 4.15 for Jeff T-403/DGEBA systems, respectively). For both stoichiometric critical gel (CG) structures obtained by changing the curing time t _r , a power-law rheological behaviour (G′∼ G″∼ωⁿ, G′ and G″ are the storage and loss moduli, respectively, ω is angular frequency and n is a critical exponent) with the loss tangent, tan δ= G″/G′ independent of frequency, was found. On the other hand, both CG off-stoichiometric systems with r ^c _H ratios show a small dependence of tan δ on ω, so that the critical power-law behaviour is not exactly obeyed. More complex CG structure in these samples, formed due to differences in the structure growth process, was suggested to account for violation of the power-law behaviour. Received: 4 December 1998/Accepted: 10 March 1999