Chantara Thevy Ratnam

Stabilization of poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends

Abstract In order to improve the positive effect of irradiation, the stability of poly (vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends was studied with particular attention to stabilization of the PVC phase. Stability of 70/30 PVC/ENR blends was studied by examining evidence from brabender torque-time curves, tensile strength, yellowness index, hardness and gel fraction. The observation on the trend shown in the above properties has confirmed that among the common PVC stabilizers employed in this studies, tribasic lead sulfate is efficient in stabilizing PVC/ENR blends as well as enhancing the blend properties upon irradiation. Addition of zinc octoate proved to play a major role in providing good color retention and radiation stability to the blends although the improvement on the blend properties through irradiation was found to be relatively low. Studies also revealed that the initial stability of the blend during processing is of prime importance in order to further stabilize the blends upon irradiation. Possible stabilization of the blends by oxirane group present in ENR is also discussed. ©

Modification of PVC/ENR blend by electron beam irradiation: effect of crosslinking agents

Abstract In order to improve the mechanical properties of PVC/ENR blends, they were irradiated by using a 3.0 MeV electron beam machine with doses ranging from 20 to 200 kGy. Changes in mechanical properties of the blends with increasing irradiation dose were investigated. In an attempt to maximize the beneficial effect of irradiation, the influence of multifunctional acrylates (MFA) such as TMPTA, HDDA and EHA on the 70/30 PVC/ENR blend was investigated. The properties studied include hardness, gel fraction, tensile strength, elongation at break and glass transition temperature. The results revealed that all mechanical properties increased with increasing irradiation dose with exception of elongation at break. The enhancement in blend properties was further improved by addition of MFA. This is attributed to the increase in crosslink density. The steady increase in gel fraction with irradiation dose and the shifting of the irradiation those towards a lower value to achieve 70% gel fraction upon addition of MFA has provided evidence for significant increase in crosslink density. Among the MFA employed in this studies, TMPTA was found to render highest mechanical properties to the blend with irradiation. Thus, TMPTA can be useful as an efficient crosslink enhancer to PVC/ENR blends. Results from Fourier transform infrared spectroscopy (FTIR) indicated radiation-induced crosslinks formed in PVC/ENR blends sensitized by TMPTA. The single glass transition temperature obtained confirms that the blend remains miscible upon irradiation with the presence of TMPTA. The changes in blend properties upon irradiation with the addition of acrylated polyurethene (PU) oligomer are also presented in this paper.

Electron beam irradiation of epoxidized natural rubber

Abstract The effect of irradiation on ENR50 was studied with particular attention to irradiation-induced crosslinking. ENR50 was irradiated by using a 3.0 MeV electron beam machine with doses ranging from 20 to 200 kGy. The influence of several additives such as TMPTA, Irganox1010 and tribasic lead sulfate on irrradiation-induced crosslinking of ENR50 was investigated. The gel fraction, Ts, M100, Eb, hardness and Tg were used to follow the irradiation-induced crosslinking of the rubber. Results revealed that the increase in gel fraction upon irradiation of pure ENR50 could be associated with both irradiation-induced crosslinking as well as ring opening side chain reaction of oxirane group. The observation on the trend shown in the properties studied confirmed that TMPTA is efficient in enhancing the irradiation-induced crosslinking of ENR50. The addition of Irganox1010 and tribasic lead sulfate found to inhibit irradiation-induced crosslinking of ENR50 to considerable extent. This influence of stabilizing additives in particular, antioxidant, was observed to be more prominent at lower doses. The importance of TMPTA in preventing ring opening side chain reactions as well as the role of the stabilizing additives in introducing free chain ends are also discussed. However studies did not reveal the exact nature of irradiation-induced reactions involved in ENR.

The effect of electron beam irradiation on the tensile and dynamic mechanical properties of epoxidized natural rubber

The effect of irradiation on the tensile and dynamic mechanical properties of ENR50 (ENR: epoxidized natural rubber) was investigated. 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), Irganox1010 and tribasic lead sulfate (TBLS) on the irradiation-induced changes of ENR50 was investigated. The general improvement on the tensile, as well as dynamic mechanical properties with irradiation indicates the formation of irradiation-induced crosslinks. An appreciable increase in Tg is observed with irradiation while the enhancement in stress at break is found to be marginal. This observation agrees well with the relatively small increase in storage modulus occurred beyond the Tg of the irradiated ENR. This in return reveals that only a small degree of crosslinking is achieved through irradiation. Based on these factors it can be inferred that the gradual increase in Tg upon irradiation of ENR50 could be associated with the occurrence of irradiation-induced ring opening side chain reaction of the oxirane group and irradiation-induced oxidation at the cis double bond along with the irradiation-induced crosslinking. From the observation in the properties studied it confirms that TMPTA is efficient in enhancing the irradiation-induced crosslinking of ENR50. The addition of Irganox1010 and TBLS are found to impart considerable stability to ENR50, although the antioxidant did cause some inhibition of crosslinking. The acceleration of crosslinking by the TMPTA as well as the inhibition of crosslinking the added stabilizing additives were further confirmed by using gel fraction data. However, the studies did not reveal the exact nature of irradiation-induced reactions involved in ENR.

Enhancement of polyvinyl chloride (PVC)/epoxidised natural rubber (ENR) blend properties by electron beam irradiation: effect of antioxidants

Abstract The effects of 3 different types of antioxidants; a hindered phenol, a phosphite and a hindered amine light stabilizer (HALS) on the radiation-induced crosslinking and oxidative degradation of 70 30 polyvinyl chloride (PVC)/epoxidised natural rubber (ENR) blend with a crosslinking agent were studied. The gel fraction, tensile strength, elongation at break, modulus and hardness were used to follow the irradiation-induced crosslinking and oxidative degradation of the blend. Results on mechanical properties implied that the hindered phenol is an effective antioxidant for the investigated PVC/ENR blend system. The modulus and hardness results revealed that addition of antioxidant to the blend favours the formation of free ends in the crosslinked network upon irradiation. The Fourier transform infrared spectroscopy analysis indicated that the radiolysis products of hindered phenol at 60 kGy induce post irradiation reaction in PVC/ENR blends. However, studies did not reveal the exact nature of the radiolysis product responsible.

Surface Plasma Modification of LLDPE for Biomedical Applications

Linear low density polyethylene (LLDPE) surface was modified by water plasma treatment to functionalized with oxygen-containing functional groups and to improve wettability. The LLDPE surface was treated at 10 and 20 W discharge power at various exposure times. A laboratory scale Megatherm radio frequency (RF) plasma apparatus that operates at 27 MHz was used to generate the water plasmas. Comparative studies were also made on LLDPE by using Argon plasma discharge followed by exposure to oxygen. The changes in chemical structure of the LLDPE polymeric chain upon plasma treatment were characterized by FTIR and XPS techniques. The selectivity of trifluoroacetic anhydride (TFAA) toward hydroxyl groups is used to quantify the hydroxyl groups formed on the polymer surface upon plasma treatment. The surface wettability of the samples was evaluated by measuring water contact angle of the samples before and after modification. In an attempt to understand the effect of surface modification of polymers on organopolysiloxane coating, selected samples were coated with SIGMACOTE. After exposition to the plasma discharge a decline in water contact angle were observed. FTIR and XPS measurements indicate an oxidation of degraded polymeric chains and creation of hydroxyl, carbonyl, ether, ester and carboxyl groups. Chemical derivatization with TFAA of water plasma treated polymer surfaces has shown that under the conditions employed, a very small (less than 5%) of the oxygen introduced by the water plasma treatment was present as hydroxyl group. The XPS results revealed that, under the plasma condition utilized, the surface modification of LLDPE using water plasma improves the wetting of polysiloxane onto the LLDPE surface.

Electron Beam Irradiation of EVA/ENR Blend

ABSTRACT The effect of irradiation on a 50/50 ethylene vinyl acetate/epoxidized natural rubber blend was studied. The 50/50 ethylene vinyl acetate/epoxidized natural rubber blend was prepared by mixing in a Brabender Plasticoder at 120°C. The blend was then irradiated by using a 3.0 MeV electron beam machine at doses ranging from 20 to 100 kGy in air and room temperature. The dynamic mechanical properties, tensile properties, hardness, and gel fractions of the blends were measured. It was found that the tensile strength, modulus, and hardness of the blend increased with irradiation with a concomitant decline in elongation at break. Results on the gel fraction revealed that under the irradiation conditions employed, the EVA/ENR blend crosslinked by electron beam irradiation. The addition of TMPTA and Surlyn ionomer was found to be effective in increasing the degree of crosslinking.

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

Electron-beam irradiation of poly(vinyl chloride)/epoxidized natural rubber blend in the presence of Irganox 1010

Abstract The effect of irradiation on a 50/50 poly(vinyl chloride)/epoxidized natural rubber blend was studied in the presence of 0–1.5 phr Irganox 1010. The blend was irradiated by using a 3.0 MeV electron beam machine at 0, 100 and 200 kGy irradiation doses. The results on the gel fraction and tensile strength revealed the inhibition of the irradiation-induced crosslinking by the Irganox 1010. The dynamic mechanical analysis and scanning electron microscopic studies further confirmed these observations. The consumption of the Irganox 1010 during irradiation and the stability offered by the antioxidant against irradiation-induced oxidative degradation was evident from FTIR analysis. The retention in the tensile strength upon ageing at 70°C/168 h suggests that the addition of 0.5 phr Irganox 1010 is essentially sufficient to provide stability to the blend with minimum loss in mechanical properties during irradiation.

Modification of PVC/ENR blends by electron beam irradiation

The effects of electron irradiation, with doses ranging from 20 to 100 kGy on the physical properties of poly(vinyl chloride)/epoxidised natural rubber blends (PVC/ENR50 blends) were investigated. The enhancement in tensile strength, elongation at break, hardness, and aging properties of the blends have confirmed the positive effect of irradiation on the blends. Crosslinking of the ENR50 phase proved to play a major role in the improvement of mechanical properties of blends. The results also revealed that at any blend composition the enhancement in properties depends on the irradiation dose which controls the degree of radiation-induced crosslinking. The single glass transition temperature obtained confirms that the blends remain miscible upon irradiation. Die Wirkung von Elektronenbestrahlung mit Dosen zwischen 20 und 100 kGy auf die physikalischen Eigenschaften von Blends aus Polyvinylchlorid (PVC) und epoxidiertem Naturkautschuk (ENR50) wurde untersucht. Steigerungen der Zugfestigkeit, der Bruchdehnung, der Harte und der Alterungseigenschaften bestatigen den positiven Einflus der Bestrahlung. Die Vernetzung der ENR50-Phase spielt eine grose Rolle bei der Verbesserung der mechanischen Eigenschaften. Die Ergebnisse zeigen auch, das bei jeder Blendzusammensetzung die Eigenschaftsverbesserungen von der Strahlendosis abhangen, mit der sich der Grad der strahleninduzierten Vernetzung kontrollieren last. Auch nach Bestrahlung sind die Blends mischbar, was sich in einer einzigen Glasubergangstemperatur ausert.