Effect of electron‐beam irradiation on poly(vinyl chloride)/epoxidized natural rubber blend: dynamic mechanical analysis

The irradiation‐induced crosslinking in 50/50 poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend was investigated by means of dynamic mechanical analysis. The influence of trimethylolpropane triacrylate on the irradiation‐induced crosslinking of PVC/ENR blends was also studied. The enhancement in storage modulus and T_g with irradiation dose indicated the formation of irradiation‐induced crosslinks. This is further supported by the decrease in tan δ_max and loss modulus peak. The compatibility of the blend was found to be improved upon irradiation. The Fox model was used to provide a further insight into the irradiation‐induced compatibility in the blend. Scanning electron microscopy studies on the cryofracture surface morphology of the blends as well as the homopolymer have been undertaken in order to gain more evidence on the irradiation‐induced crosslinking. © 2001 Society of Chemical Industry     

Irradiation Crosslinking of PVC/ENR Blend: A Comparative Study with the Respective Homopolymers

Electron beam initiated crosslinking on a 50/50 poly(vinyl chloride)/epoxidized natural rubber blend was studied in the absence and presence of 3 phr trimethylolpropane triacrylate (TMPTA). Comparative studies were made on PVC and ENR homopolymers. The samples were irradiated by using a 3.0 MeV electron beam machine at doses ranging from 20 to 200 kGy in air and room temperature. The changes in tensile strength, gel fraction and tan δ curves of the samples were investigated. The enhancement in tensile strength, gel fraction, glass transition temperature together with a concomitant decline tan δ peak revealed that under the irradiation conditions employed, the PVC/ENR blend crosslinked by electron beam irradiation. Addition of 3 phr TMPTA found to be effective in increasing the degree of crosslinking. Similar observations were also noted for the homopolymers PVC and ENR, implying that both PVC and ENR in the blend undergo crosslinking to a certain extent.     

Effect of trimethylolpropane triacrylate (TMPTA) on the properties of irradiated epoxidized natural rubber (ENR‐50), ethylene‐(vinyl acetate) copolymer (EVA), and an ENR‐50/EVA blend

The effect of trimethylolpropane triacrylate (TMPTA) monomer on the tensile properties, dynamic mechanical properties, and morphology of irradiated epoxidized natural rubber (ENR‐50), ethylene‐(vinyl acetate) copolymer (EVA), and an ENR‐50/EVA blend was investigated. The ENR‐50, EVA, and ENR‐50/EVA blend were irradiated by using a 3.0‐MeV electron‐beam apparatus at doses ranging from 20 to 100 kGy. The improvement of tensile properties and morphology with irradiation indicated the advantage of having irradiation‐induced crosslinks in these materials. Observation of the properties studied confirmed that TMPTA was efficient in enhancing the irradiation‐induced crosslinking of ENR‐50, EVA, and the ENR‐50/EVA blend. Addition of TMPTA improved the adhesion between the ENR‐50/EVA blend phases by forcing grafting and crosslinking at a higher irradiation dose (100 kGy). J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers.     

Structure–property relationship of electron‐beam‐modified EPDM rubber

Electron‐beam‐initiated grafting of trimethylolpropane triacrylate (TMPTA) onto the bulk ethylene propylene diene monomer (EPDM) was carried out with varying concentrations of TMPTA at a constant irradiation dose of 100 kGy and over a wide range of irradiation doses (0–500 kGy) at a fixed concentration (10%) of TMPTA. The rubber was also modified in the bulk by tripropylene glycol diacrylate (TPGDA, 10%) and tetramethylol methane tetraacrylate (TMMT, 10%) at an irradiation dose of 100 kGy. The modified rubbers were characterized by IR spectroscopy, crosslinking density measurements, and mechanical, dynamic mechanical, and electrical properties. The IR studies indicated increased peak absorbances at 1730, 1260, and 1019 cm⁻¹ due to increased 〉CO and C O C concentrations up to certain levels of TMPTA and irradiation dose. These are accompanied by an increase in the crosslinking density. The tensile strength of the samples increases gradually with increasing both the concentration of the monomer and radiation dose up to a certain level. The values of the modulus also increase at the expense of the elongation at break. An increase in the number of double bonds from two in the case of the diacrylate to four in the case of the tetraacrylate also brings about an increase in the tensile strength and moduli values. The elongation at break, however, decreases. The DMTA measurements indicate changes in the glass transition temperature, T_g, and tan δ_max on modification. The T_g shifts to a higher temperature with a simultaneous lowering of the tan δ_max values as the TMPTA level is increased. A similar trend is observed when the irradiation dose is increased and the nature of the monomer changes from di‐ to tetraacrylate. The dielectric loss tangent registers an increase on modification by irradiation of TMPTA while the permittivity is decreased. All the results could be explained on the basis of the structural modification and crosslinking density. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 323–337, 2000     

Electron beam irradiation of epoxidized natural rubber: FTIR studies

The effect of irradiation on the structure of epoxidized (50 %) natural rubber (ENR50) has been studied using Fourier transform infrared spectroscopy (FTIR). ENR50 was irradiated using a 3.0 MeV electron beam machine with doses ranging from 20 to 200 kGy. The influence of several additives such as trimethylolpropane triacrylate (TMPTA). Irganox®1010, and tribasic lead sulfate on the irradiation‐induced changes of ENR50 is investigated. Upon irradiation, ring opening of epoxide groups, and oxidation and crosslinking of residual double bonds occurred, leading to decreases in the intensities of epoxide and cis double bond bands and an increases in ether, furan and hydroxyl bands. Gel fraction and hardness values have been used to correlate changes in the structure of the rubber upon irradiation. The results show that the increase in gel fraction upon irradiation of pure ENR50 can be associated with irradiation‐induced crosslinking, ring opening side‐chain reactions of oxirane groups and oxidation at the cis‐double bonds. The addition of Irganox®1010 and tribasic lead sulfate inhibits irradiation‐induced reactions in ENR50 to a considerable extent. The importance of TMPTA in preventing intramolecular ring opening side‐chain reactions is also discussed. However, our studies do not reveal the exact nature of the irradiation‐induced reactions involved in ENR. © 2000 Society of Chemical Industry     

Irradiation crosslinking of PVC–ENR blend Effect of efficient radical scavenger

Abstract

The irradiation induced crosslinking of 50:50 poly (vinyl chloride)–epoxidised natural rubber (PVC–ENR) blend was studied in the presence of 0–1·5 pphr antioxidant Irganox 1010. The samples were irradiated using a 3·0 MeV electron beam machine at doses ranging from 20 to 200 kGy in air and room temperature. The gel fraction, tensile strength T _s, modulus at 100% elongation M ₁₀₀, elongation at break E _b, hardness, and resilience were used to follow the irradiation induced crosslinking of the blend. The decline in gel fraction, T _s, M ₁₀₀, hardness, and resilience and the concurrent increase in E _b with increasing antioxidant indicated the inhibition of irradiation induced crosslinking by the antioxidant used. The improvement in aging properties of the blend with the addition of the antioxidant is also reported. It was evident from FTIR that Irganox 1010 is involved in the stabilisation of the blend against irradiation induced degradation.     

Electron‐beam irradiation of poly(vinyl chloride)/epoxidized natural rubber blends in presence of trimethylolpropane triacrylate

Electron‐beam initiated crosslinking of poly(vinyl chloride)/epoxidized natural rubber blends, which contained trimethylolpropane triacrylate (TMPTA), was carried out over a range of irradiation doses (20–200 kGy) and concentrations of TMPTA (1–5 phr). The gel content increased with the irradiation dose and the TMPTA level, although the increase was marginal at higher doses and higher TMPTA levels. Blends containing 3–4 phr TMPTA achieved optimum crosslinking, which in effect caused the maximum tensile strength (TS) at a dose of 70 kGy. A further addition of TMPTA caused a decline in the TS above 40 kGy that was due to embrittlement, which is a consequence of excessive crosslinking and the breakdown of the network structure. The possible formation of a more open network as a result of the breakdown of the network structure was further confirmed by the modulus results. Dynamic mechanical analysis (tan δ curve) and scanning electron microscopy studies on samples irradiated at 0 and 200 kGy were undertaken in order to gain further evidence on the irradiation‐induced crosslinking. The plasticizing effect of TMPTA prior to irradiation and the formation of microgels upon irradiation were also discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1926–1935, 2001     

Irradiation Modification of PVC/NBR Blend

Electron beam initiated cross-linking on the 50/50 poly(vinyl chloride), PVC/acrylonitrile butadiene rubber, NBR blend was studied in the absence and presence of 4 phr trimethylolpropane triacrylate (TMPTA). The 50/50 NBR/PVC blend was prepared by mixing in a Brabender Plasticoder at 170°C. The blend was then irradiated by using a 3.0 MeV electron beam machine at doses ranging from 0 to 200 kGy in air and room temperature. The changes in gel fraction, tensile strength, hardness, impact strength, scanning electron micrographs and dynamic mechanical properties of the samples were investigated. The gel fraction results indicate that under the irradiation conditions employed, the PVC/NBR blend cross-linked by electron beam irradiation. The addition of TMPTA was found to be effective in the acceleration of the radiation-induced cross-linking. Gradual increases in mechanical properties with irradiation dose were observed before exhibiting a decline due to embrittlement as a consequence of excessive cross-linking at higher irradiation doses. The gradual changeover from ductile to brittle fracture due to the irradiation-induced cross-linking was evident from the SEM examination The increase in the storage modulus and T_g as well as the reduction in the damping peak with the increase in irradiation dose reveal that the enhancement in mechanical properties of NBR/PVC blends upon irradiation is due to the irradiation-induced cross-linking, as well as the improved interaction between NBR and PVC.     

Electron beam crosslinking of fluoroalkoxy,methoxyethoxyethoxy, and substituted phenoxy polyphosphazenes: Physical and chemical characterization and comparison to a thermally induced free radical process and ionic complexation

Electron beam, thermal free radical, and cationic complexation mechanisms have been employed to investigate crosslinking in selected polyphosphazenes. In polyphosphazenes functionalized with o‐allylphenol to facilitate free radical crosslinking, maximum crosslink density was achieved after 10 min at 130°C utilizing benzoyl peroxide as an initiator. Electron beam radiation was found to give an increased crosslink density with increased dose. The dose–crosslink density relationship observed for a aryloxyphosphazene terpolymer PPXP also was seen in poly[bis(2,2′‐(methoxyethoxy)ethoxy)phosphazene] (MEEP). However, with two lots of a fluoroalkoxyphosphazene an initial crosslink density was achieved at a lower electron beam exposure with no additional crosslink density observed with increasing dose. These measurements are observations of net crosslinking, which is the result of crosslinking processes balanced by chain scission processes. DSC revealed that neither thermal‐ nor electron beam‐initiated crosslinking cause any significant change in the T_g of the polymer. Metal ion complexation with MEEP consistently gave T_g values that were higher than MEEP. The T_g values measured for both MEEP and the lithium‐complexed MEEP were unaffected by electron beam irradiation. These data suggest the location of lithium complexation may be at the nitrogen lone electron pair on the backbone, representing a new mechanism of lithium complexation in phosphazenes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 55–66, 2000     

Gel,thermal, and X‐ray diffraction characterization of virgin,scrapped polyethylene and its blends

The characterizations of virgin and scrapped polyethylene samples (VPE and SPE) and VPE/SPE blends were studied using different analytical techniques. The obtained data regarding crosslink density demonstrated that the radiation‐induced crosslinking of VPE, SPE, and VPE/SPE samples increased as a result of increasing irradiation dose, blending VPE with SPE, and loading the VPE/SPE blend with trimethylol propane triacrylate (TMPTA). The use of differential scanning calorimetry technique was aimed at revealing the effect of sample composition (VPE, SPE, and VPE/SPE) and also the effect and type of irradiation on the melting temperature (T_m) and the heat of transformation (ΔH_f). The melting temperature and heat of transformation increased with increasing either irradiation dose or loading the polymeric samples with TMPTA. In addition, the application of thermogravimetric analysis (TGA) was used to study the degradation characteristics of the polymeric samples in terms of onset temperature (T_i), temperature at maximum weight loss (T_s), and activation energy (E_a). The TGA results showed that the irradiation (EB and γ‐rays) and loading of polymeric samples with TMPTA led to a thermally stable polymeric matrix with higher T_i, T_s, and E_a values. The blank SPE sample or those blend rich in SPE matrix were highly thermally stable than that blank VPE one. The X‐ray diffraction investigation illustrated that VPE samples undergoes phase transformation between orthorhombic, monomclinic, and/or hexagonal as a result of irradiation. POLYM. COMPOS. 27:709–717, 2006. © 2006 Society of Plastics Engineers     

Thermal and mechanical properties of electron beam irradiated poly(vinyl chloride)/polystyrene blends

The effect of electron beam irradiation on the thermal and mechanical properties of poly(vinyl chloride)/polystyrene (PVC/PS) blends and PVC/PS blends containing epoxidized natural rubber (ENR) was studied. The thermogravimetric analysis study showed that the thermal decomposition of the plasticized PVC individual polymer goes through two stages, whereas PS decomposes through one stage. However, the temperature of the maximum rate of reaction (T_max) of PS is much higher than that for PVC and their blends. Meanwhile, the T_max was found to increase with increasing PS ratios in the blend. The thermal stability of PVC/PS blends was greatly increased after electron beam irradiation in comparison with unirradiated blends. Moreover, the addition of ENR to PVC/PS increased the thermal stability. On the other hand, the mechanical properties in terms of tensile strength and elongation at break of PVC/PS blends are lower than pure PVC polymer because of the immiscibility. However, the addition of ENR to the PVC/PS (80/20) blend increased the elongation at break from 114 to 321% associated with a small effect on the tensile properties. These behaviors were supported by structure morphology studies observations, which indicate an improvement in the interfacial adhesion between the phases. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Irradiation modification of PVC/ENR blend: effect of TBLS content

The effect of a poly(vinyl chloride) stabilizer, namely, tribasic lead sulfate (TBLS), on the irradiation modification of 50/50 poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend, was investigated with a particular attention to inhibition of irradiation-induced crosslinking. The blends were prepared by mixing in a Brabender Plasticoder with the incorporation of 2, 3, and 5 phr (parts per hundred of total resin) TBLS. They were then irradiated using a 3.0 MeV electron accelerator with doses ranging from 0 to 200 kGy. The gradual fall in tensile strength, gel fraction, hardness, and resilience of the irradiated blend with the increase in TBLS content implied the inhibition of crosslinking by the stabilizer. The reduction in crosslink density with the addition of TBLS was further evidenced from the decline in T _gwith a concomitant increase in tan δ maxima with the increase in TBLS content.     

Mechanical Properties and Thermooxidative Aging of a Ternary Blend,Pvc/Enr/Nbr,Compared with the Binary Blends of Pvc

In the quest to improve the thermooxidative aging of the poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend, nitrile rubber (NBR) was incorporated into the blend to yield a ternary blend of PVC/ENR/NBR. A Brabender Plasticorder with a mixing attachment was used to perform the melt mixing at 150°C and 50 rpm followed by compression molding. The mechanical properties, dynamic mechanical properties, and thermooxidative aging behavior of the ternary blend were compared with those of the binary blends (i.e., PVC/ENR and PVC/NBR). It was found that the ternary blend exhibits mechanical properties which are superior to those of PVC/ENR. A single glass transition temperature (T _g) obtained from dynamic mechanical analysis coupled with synergism in the modulus and some other mechanical properties indicate that PVC, ENR, and NBR form a single phase (miscible system) in the ternary blend. Di-2-ethyl hexylphthalate (DOP) plasti-cizer improves the aging resistance of the blends generally, whereas the presence of CaCO₃ as a filler only imparts minor influences on the properties and aging resistance of the blends.     

辐照交联PVC／EVA共混物的形态结构与性能

以电子束为辐照源，以三羟甲基丙烷三丙烯酸酯（TMPTA）单体为交联敏化剂，对聚氯乙烯与乙烯－醋酸乙烯共聚物（EVA）的共混物进行辐照交联。采用红外吸收光谱、扫描电镜方法分析了添加改性EVA的共混物形态结构。通过凝胶含量、力学性能的测定，得到结论：EVA共聚物与PVC共混可以促进PVC辐照交联，改性EVA促进效果更明显；辐照剂量增大、体系凝胶含量增加，力学性能及热延伸性能提高，但辐射剂量高于5Mrad之后，体系降解程度明显增加。     

Synthesis and swelling characteristics of poly(4‐vinylpyridine) gels crosslinked by irradiation

The effect of irradiation under vacuum on thermal properties and swelling behavior on poly(4‐vinylpyridine) (P4VP) was investigated. The gel percentage in the irradiated P4VP films was determined by Soxhlet extraction. UV spectroscopy was also used to determine sol percentage, which decreased as the radiation dose increased. The changes in thermal properties, such as glass‐transition temperature (T_g), were followed by differential scanning calorimetry before and after Soxhlet extraction. The gels prepared after irradiation were characterized with respect to their swelling properties and network structures. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2609–2614, 2001     

Polymer electrolyte membranes prepared by EB‐crosslinking of sulfonated poly(ether ether ketone) with 1,4‐butanediol

Crosslinked sulfonated poly(ether ether ketone) (SPEEK) membranes were prepared through the electron beam (EB)‐irradiation crosslinking of SPEEK/1,4‐butanediol under various irradiation conditions and used as a proton exchange membrane (PEM) for fuel cell applications. The crosslinked membranes were characterized by gel fraction, a universal testing machine (UTM), dynamic mechanical analysis (DMA), and small‐angle X‐ray scattering (SAXS). The gel fraction of the crosslinked membranes was used to estimate the degree of crosslinking, and the gel fraction was found to be increased with an increase of the crosslinker content and EB‐absorbed dose. The UTM results indicate that a brittle EB‐crosslinked membrane becomes more flexible with an increase in the crosslinker content. The DMA results show that the EB‐crosslinked membranes have well‐developed ionic aggregation regions and the cluster T_g of membranes decrease with an increase in the 1,4‐butanediol crosslinker content. The SAXS results show that the Bragg and persistence distance of crosslinked membranes increase with an increase in the crosslinker content. The proton conductivities of the EB‐crosslinked membranes were more than 9 × 10^?2 S/cm. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41760.     

Comparison of thermoset soy protein resin toughening by natural rubber and epoxidized natural rubber

Fully bio‐based soy protein isolate (SPI) resins were toughened using natural rubber (NR) and epoxidized natural rubber (ENR). Resin compositions containing up to 30 wt % NR or ENR were prepared and characterized for their physical, chemical and mechanical properties. Crosslinking between SPI and ENR was confirmed using ¹H‐NMR and ATR‐FTIR. All SPI/NR resins exhibited two distinctive drops in their modulus at glass transition temperature (T_g ) and degradation temperature (T_d ) at around ?50 and 215 °C, corresponding to major segmental motions of NR and SPI, respectively. SPI/ENR resins showed similar T_g and T_d transitions at slightly higher temperatures. For SPI/ENR specimens the increase in ENR content from 0 to 30 wt % showed major increase in T_g from ?23 to 13 °C as a result of crosslinking between SPI and ENR. The increase in ENR content from 0 to 30 wt % increased the fracture toughness from 0.13 to 1.02 MPa with minimum loss of tensile properties. The results indicated that ENR was not only more effective in toughening SPI than NR but the tensile properties of SPI/ENR were also significantly higher than the corresponding compositions of SPI/NR. SPI/ENR green resin with higher toughness could be used as fully biodegradable thermoset resin in many applications including green composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44665.     

Time–temperature–transformation cure diagrams of phenol–formaldehyde and lignin–phenol–formaldehyde novolac resins

In this study, the time–temperature– transformation (TTT) cure diagrams of the curing processes of several novolac resins were determined. Each diagram corresponded to a mixture of commercial phenol–formaldehyde novolac, lignin–phenol–formaldehyde novolac, and methylolated lignin–phenol–formaldehyde novolac resins with hexamethylenetetramine as a curing agent. Thermomechanical analysis and differential scanning calorimetry techniques were applied to study the resin gelation and the kinetics of the curing process to obtain the isoconversional curves. The temperature at which the material gelled and vitrified [the glass‐transition temperature at the gel point (_gelT_g)], the glass‐transition temperature of the uncured material (without crosslinking; T_g0), and the glass‐transition temperature with full crosslinking were also obtained. On the basis of the measured of conversion degree at gelation, the approximate glass‐transition temperature/conversion relationship, and the thermokinetic results of the curing process of the resins, TTT cure diagrams of the novolac samples were constructed. The TTT diagrams showed that the lignin–novolac and methylolated lignin–novolac resins presented lower T_g0 and _gelT_g values than the commercial resin. The TTT diagram is a suitable tool for understanding novolac resin behavior during the isothermal curing process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Relationship between viscoelastic properties and gelation in the epoxy/phenol‐novolac blend system with N‐benzylpyrazinium salt as a latent thermal catalyst

A study of viscoelastic properties and gelation in epoxy/phenol‐novolac blend system initiated with 1 wt % of N‐benzylpyrazinium hexafluoroantimonate (BPH) as a latent cationic thermal initiator was performed by analysis of rheological properties using a rheometer. Latent behavior was investigated by measuring the conversion as a function of curing temperature using traditional curing agents, such as ethylene diamine (EDA) and nadic methyl anhydride (NMA) in comparison to BPH. In the relationship between viscoelastic properties and gelation of epoxy/phenol‐novolac blend system, the time of modulus crossover was dependent on high frequency and cure temperature. The activation energy (E_c) for crosslinking from rheometric analysis increased within the composition range of 20–40 wt % phenol‐novolac resin. The 40 wt % phenol‐novolac (N40) to epoxy resin showed the highest value in the blend system, due to the three‐dimensional crosslinking that can take place between hydroxyl groups within the phenol resin or epoxides within the epoxy resin involving polyaddition of the initiator with BPH. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2299–2308, 2001     

Structural development in ion‐irradiated poly(ether ether ketone) as studied by dielectric relaxation spectroscopy

Structural alterations to amorphous poly(ether ether ketone) (PEEK) produced by ion irradiation (11.2 MeV H⁺ and 25.6 MeV He²⁺ ions) were investigated by dielectric relaxation spectroscopy. The analysis in terms of the Havriliak–Negami (HN) equation and the scaling model showed an increase in the intermolecular correlation with increasing irradiation dose. The dynamic fragility index (m) was estimated from Vogel–Fulcher–Tammann analysis. Ion irradiation not only elevated the glass‐transition temperature (T_g) but interestingly decreased m of the PEEK chains around T_g. This was due to increasing polar interaction and better packing efficiency of the irradiated samples compared with those of amorphous PEEK. The average size of the cooperative rearranging region decreased in line with decreasing m and indicated an increase in the rigid amorphous phase fraction after irradiation. The analysis of the direct‐current conductivity confirmed that there was a strong coupling between the macroscopic ion transport and concerted segmental motion. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39929.