Radiation Cross-linking Process Research Articles

Theoretical study on the grafting reaction of maleimide containing 2-hydroxy-benzophenone onto polyethylene.

A theoretical study on the multi-channel hydrogen addition of maleimide containing 2-hydroxy-benzophenone onto polyethylene in ultra-violet (UV) radiation cross-linking process was carried out using density functional theory (DFT) method at the B3LYP/6-311 + G(d,p) level. The energetic information and the minimum energy path (MEP) are calculated for nine reaction channels. The electrophilic addition reactions at two positions in the target molecule (maleimide containing 2-hydroxy-benzophenone) were investigated, which are on the C atom of C = C groups and on the O atom of C = O groups. Frontier molecular orbitals (MOs) and natural bond orbital (NBO) charge population of the target molecule have been analyzed in detail. As a result, the reaction site of C in C = C group is more active than the site of O in C = O groups. The target molecule can be used as a multi-functional additive candidate. The predicted mechanism may provide a theoretical basis for the real application of cross-linked polyethylene (XLPE) high-voltage insulation cables.

New and novel stabilisation approach for radiation-crosslinked Ultrahigh Molecular Weight Polyethylene (XL-UHMWPE) targeted for use in orthopeadic implants

There is a substantial evidence to show that oxidative degradation has a negative impact on the properties and performance of radiation-crosslinked ultra high molecular weight polyethylene (XL-UHMWPE) used as articulating components in orthopaedic joint implants and is the primary cause for their premature failure. In general, high energy radiation is required not only for sterilising the articulating surfaces but also for crosslinking the polymer to improving its mechanical properties and wear resistance thus minimising the extent of formation of wear-particles which are implicated in the aseptic loosening and failure of the implant. To address the oxidative stability of the XL-UHMWPE bearing surfaces, the natural hindered phenol antioxidant, vitamin E, which has been approved by FDA for use in this application, is used to enhance the oxidation resistance of orthopaedic implants, e.g. in tibial bearings. Further, a purified grade of the commercial antioxidant Irganox 1010Ⓡ (pentaerythritol tetrakis(3-[3,5-di tertiary butyl‑4‑hydroxy phenyl]propionate) has also been FDA approved and used in some knee-based systems. In the case of vitamin E, its effectiveness as a potent free radical scavenger, however, presents some issues in respect of the polymer crosslinking process and the homogeneity of its distribution especially during manufacturing processes that involve the infusion of the vitamin into the polymer. The novel approach adopted in this study for the stabilisation of XL-UHMWPE bearing surfaces makes use of graftable polymer-reactive antioxidants (r-AOs) bearing a hindered phenol and also hindered amine moieties. Potentially, these r-AOs can be chemicaly grafted in-situ on the polymer backbone during the radiation-crosslinking process without the need for any additional manufacturing step. The results obtained have demonstrated a substantive stabilisation which can be achieved with these r-AOs. This was shown to be the case in all the XL-UHMWPE samples tested here which were manufactured according to a methodology typically used in the commercial production and crosslinking (by gamma- or electron-beam) of UHMWPE-based implants.

Theoretical study on the hydrogen addition reactions to bismaleimide in the ultra-violet radiation cross-linking process of polyethylene

Theoretical investigation on the multiple-channel addition reactions of hydrogen in polyethylene to bismaleimide in the Ultra-violet (UV) radiation cross-linking process is accomplished by density functional theory. Their energetic information of the nineteen reaction channels at B3LYP/6-311 + G(d,p) level is obtained. Two types of electrophilic addition reaction, one is the 4-position hydrogen in 4-methylheptane to C of C=C groups in bismaleimide and the other one is the 4-position hydrogen in 4-methylheptane to O of C=O groups in bismaleimide, are identified. The effects of introducing the heteroatom O and/or the benzene ring among both ends of the two maleimide rings have been evaluated. The results show that the addition reaction potential barrier height to O in C=O groups is lower than that of the C in C=C groups in the conjugative bismaleimide system.The founding of the addition reaction channel to O in C=O groups could clear further the mechanism of grafting bismaleimide to polyethylene.

Selectivity of Copper by Amine-Based Ion Recognition Polymer Adsorbent with Different Aliphatic Amines.

This paper investigates the selectivity of GMA-based-non-woven fabrics adsorbent towards copper ion (Cu) functionalized with several aliphatic amines. The aliphatic amines used in this study were ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). The non-woven polyethylene/polypropylene fabrics (NWF) were grafted with glycidyl methacrylate (GMA) via pre-radiation grafting technique, followed by chemical functionalization with the aliphatic amine. To prepare the ion recognition polymer (IRP), the functionalized amine GMA-grafted-NWF sample was subjected to radiation crosslinking process along with the crosslinking agent, divinylbenzene (DVB), in the presence of Cu ion as a template in the matrix of the adsorbent. Functionalization with different aliphatic amine was carried out at different amine concentrations, grafting yield, reaction temperature, and reaction time to study the effect of different aliphatic amine onto amine density yield. At a concentration of 50% of amine and 50% of isopropanol, EDA, DETA, TETA, and TEPA had attained amine density around 5.12, 4.06, 3.04, and 2.56 mmol/g-ad, respectively. The amine density yield decreases further as the aliphatic amine chain grows longer. The experimental condition for amine functionalization process was fixed at 70% amine, 30% isopropanol, 60 °C for grafting temperature, and 2 h of grafting time for attaining 100% of grafting yield (Dg). The prepared adsorbents were characterized comprehensively in terms of structural and morphology with multiple analytical tools. An adsorptive removal and selectivity of Cu ion by the prepared adsorbent was investigated in a binary metal ion system. The IRP samples with a functional precursor of EDA, the smallest aliphatic amine had given the higher adsorption capacity and selectivity towards Cu ion. The selectivity of IRP samples reduces as the aliphatic amine chain grows longer, EDA to TEPA. However, IRP samples still exhibited remarkably higher selectivity in comparison to the amine immobilized GMA-g-NWF at similar adsorption experimental conditions. This observation indicates that IRP samples possess higher selectivity after incorporation of the ion recognition imprint technique via the radiation crosslinking process.

Further discussion on the reaction behaviour of triallyl isocyanurate in the UV radiation cross-linking process of polyethylene: a theoretical study.

Further theoretical investigation on the reaction behaviour of triallyl isocyanurate (TAIC) in the UV radiation cross-linking process of polyethylene (PE) is accomplished by density functional theory for high voltage cable insulation materials. The reaction potential energy information of the 13 reaction channels at B3LYP/6–311 + G(d,p) level are identified. These have been explored that the TAIC take part in the reaction behaviour on ground state during UV radiation cross-linking process and TAIC intra-molecular isomerization reaction itself. In addition, the results show that the effect of multiplication and acceleration for the cross-linking reaction of trimethylopropane trimethacrylate (TMPTMA) would be better than that of TAIC. It has further clarified the reasons why UV radiation cross-linking reaction of PE had been initiated by benzophenone (Bp), and the TAIC or TMPTMA needed to take part. The results obtained in the present study could directly guide both the optimization of UV radiation cross-linking PE process and the development of the insulation material of high-voltage cable in real application.

Reducing the hydrocarbon gas diffusion and increasing the pressure-impact strength of fuel transfer pipelines for use in the automotive industry using radiation crosslinked polyamide 12

The main aim of this study was to reduce the rate of daily hydrocarbons (HC) released into the atmosphere from polyamide-based automotive fuel transfer system pipes due to diffusion using radiation processing technology. The second aim of this study was to improve the pressure level and impact strength of these pipelines. In order to manage these aims, layer by layer extruded pipelines constructed from different types of thermoplastic materials (i.e. PA6, EVOH and radiation crosslinkable 5% 1,3,5-triallyl-1,3,5-triazin-2,4,6(1H,3H,5H)-trion (TAIC) containing PA12 (Creamid-12)) were irradiated using γ-rays (up to 100 kGy) at room temperature to carry out a radiation-induced crosslinking process. The mechanical properties of the samples were evaluated using tensile and cold impact tests. Sol-gel analysis of the irradiated samples was performed to determine the gel content, gelation dose and chain scission/crosslinking ratio. The Charlesby–Pinner and Charlesby–Rosiak equations were used for our calculations. The change in the HC diffusion of the crosslinked pipes was measured using a sealed housing for evaporative determination (SHED) device. An improvement in the pressure resistance was observed for the samples under an increasing fluid pressure using a blasting test device. The SHED results showed that the gas permeability value is reduced ~1.9 fold in the 65 kGy irradiated fuel transfer pipelines. The blasting test results indicate that the average pressure resistivity of the 65 kGy irradiated and 76.5% cross-linked pipe samples was ~19% greater than that observed for the unirradiated samples. The results of this study show that the radiation cross-linking process is an excellent strategy to reduce the daily hydrocarbon emissions from new generation fuel transfer pipelines.

Theoretical study on the grafting reaction of maleimide and its derivatives to polyethylene in the UV radiation cross-linking process

Theoretical investigation on the reactions of the maleimide and its derivatives in the UV radiation cross-linking of polyethylene is accomplished by density functional theory. The reaction potential energy surface information of 12 reaction channels is determined at the B3LYP/6-311+G(d,p) level. The highest occupied molecular orbital-lowest unoccupied molecular orbital energy gaps, ionization potentials, and electron affinities of the maleimide and its derivatives are obtained. The calculated results show that the maleimide and its derivatives can be grafted to polyethylene chain during the UV radiation process. In addition, the calculated results also show that the reaction energy barrier of 1,8-bismaleimidotriethylene glycol grafted to polyethylene is lower than that of N-phenylmaleimide, and 1,8-bismaleimidotriethylene glycol can be used as cross-linking agent. The bismaleimide grafted to polyethylene can also be used as space charge inhibitor. This survey for dual function additive is expected to provide reliable information for the development of UV radiation cross-linking polyethylene process and high-voltage insulation cables exceed 500 kV in real application.

Theoretical Study on the Grafting Reaction of Maleimide to Polyethylene in the UV Radiation Cross-Linking Process.

Theoretical investigation of the reaction of graft maleimide to polyethylene in the UV radiation cross-linking process is accomplished at the B3LYP/6-311+G(d,p) level for high-voltage cable insulation materials. The reaction potential energy surface of the nine reaction channels is identified. The results show that the N,N′-ethylenedimaleimide can connect two 4-methylheptane molecules and act as the cross-linking agent. The calculated reaction potential barrier of forming 4-methylheptane radical by maleimide is higher than that of maleic anhydride. The study is expected to provide a basis for optimizing the UV radiation cross-linking polyethylene process and development more than 500 kV high-voltage cable insulation materials in practical applications.

Mechanical Properties Changes of Irradiated Thermoplastic Elastomer.

Some polymers need a cross-linking agent for the controlled cross-linking process of polymers with a tendency to degradation during the radiation cross-linking process. While, on the other hand, other polymers do not need a cross-linking agent—predominantly there are cross-linking polymers. The Thermo-Plastic Elastomer (TPE) that was used belongs to this group of predominantly cross-linking polymers; however, this agent is added because of faster reaction times and smaller irradiation doses. Microindentation–tensile and tensile impact tests were carried out on a thermoplastic sample—with, and without, a cross-linking agent. Small changes were measured between these materials at low radiation doses, (up to 66 kGy); nevertheless, at higher doses, the influence of the cross-linking agent on the mechanical properties is significant.

Theoretical study on the reaction of maleic anhydride in the UV radiation cross-linking process of polyethylene

Theoretical investigation on the reaction of maleic anhydride (MAH) in the UV radiation cross-linking process of polyethylene as high voltage cable insulation materials is accomplished at B3LYP/6-311 + G(d,p) level. The reaction potential energy information of 10 reaction channels is identified. The results show that the UV radiation cross-linking reaction of polyethylene is initiated by benzophenone, and the multi-functional crosslinker triallyl isocyanurate (TAIC) is needed to take part in the cross-linking process. The behavior of grafting the polar group MAH onto the polyethylene is explored in detail at atomic and molecular levels during UV radiation cross-linking process. The investigation is expected to provide reliable information for optimizing polyethylene UV radiation cross-linking process and for the development of the insulation material of high-voltage cable exceed 500 kV in real applications.

Theoretical study on the reaction of triallyl isocyanurate in the UV radiation cross-linking of polyethylene

Herein, a theoretical investigation on the reaction potential energy surface information of triallyl isocyanurate (TAIC) in the UV radiation cross-linking process of polyethylene is conducted at the B3LYP/6-311+G(d,p) level for the production of high voltage cable insulation materials.

The Behaviour of Cross-Linking Filled PA66 by Micro-Indentation Test

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Micro-mechanical changes in the surface layer of glass-fiber filled PA 66 modified by beta radiation were measured by the Depth Sensing Indentation - DSI method on samples which were non-irradiated and irradiated by different doses of the β - radiation. The specimens were prepared by injection technology and subjected to radiation doses of 0, 33, 66 nad 99 kGy. The change of micro-mechanical properties is greatly manifested mainly in the surface layer of the modified polypropylene where a significant growth of micro-hardness values can be observed. Indentation modulus increased from 1.8 to 3.0 GPa (increasing about 66%) and indentation hardness increased from 87 to 157 MPa (increasing about 80%). This research paper studies the influence of the dose of irradiation on the micro-mechanical properties of semi-crystalline polyamide 66 filled by 30% glass fiber at room temperature. The study is carried out due to the ever-growing employment of this type of polymer.

Theoretical study on the reaction mechanism in the UV radiation cross-linking process of polyethylene

The grafting of the valerophenone as voltage stabilizer to the polyethylene molecule chain is possible in the UV radiation cross linking process. This is useful for preparing insulation cables of high voltage up to 500 kV in real application.

Micromechanical Properties of Glass-Filled Polyamide 6

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Micromechanical changes in the surface layer of glass-filled PA-6 modified by beta radiation were measured by instrumented test of microhardness. The specimens were prepared by injection technology and subjected to radiation doses of 0, 66, 99, 132 kGy. Measurements of microhardness showed considerable changes of behavior of surface layer in middle as well as high radiation doses with higher values of indentation hardness and stiffness.

Micromechanical Properties of Thermoplastic Elastomer (TPE-E)

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Micromechanical changes in the surface layer of Thermoplastic elastomer (TPE-E) modified by beta radiation were measured by instrumented test of microhardness. The specimens were prepared by injection technology and subjected to radiation doses of 0, 66, 99, 132 kGy. Measurements of microhardness showed considerable changes of behavior of surface layer in middle as well as high radiation doses with higher values of indentation hardness and stiffness.

Influence of Content of Crosslinking Agent on the Micromechanical Properties of Glass-Filled Polyamide 6

The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Some types of polymers do not cross-link during radiation crosslinking but degrade. In order to create 3D net in the polymer structure it is necessary to add a crosslinking agent. The specimens were prepared by injection technology with the TAIC crosslinking agent at 0, 1, 2 and 3 %. The changes of micromechanical properties of the surface layer were measured by instrumented microhardness test. It was found that micromechanical properties of the surface layer of the tested polyamide changed.

Comparative study of radiation effect on rubber–carbon black compounds

Acrylonitrile butadiene rubber (NBR) and ethylene–propylene diene monomer (EPDM) rubber compounds have been prepared without and with 50phr contents of high abrasion furnace carbon black (HAF). Cure characteristics, namely, minimum (Ml) and maximum torque (Mh), scorch time (ts2), the optimum cure time (tc90) and the cure rate index (CRI) have been investigated. Prepared compounds have been subjected to gamma radiation doses up to 200kGy to induce radiation crosslinking and degradation process under atmospheric conditions. Mechanical and physical properties, namely, tensile strength (TS), elongation at break (Eb), hardness (Sh-A), Flory–Huggins parameter (χ), the crosslink density (ν) and the molecular weight of the rubber between two crosslinks (M‾c) have been followed up as a function of irradiation dose. The morphology investigations of prepared compounds were carried out using SEM micrograph. The results obtained indicate that improvement to irradiation has been attained in different properties of carbon black reinforced NBR and EPDM rubber compounds with respect to unloaded ones.

Sieciowanie i degradacja uwodornionego kauczuku butadienowo-akrylonitrylowego pod wplywem promieniowania elektronowego. Wplyw zawartosci zwiazanego akrylonitrylu

Influence of polarity of hydrogenated butadiene-acrylonitrile rubber (HNBR) on its crosslinking and radiation degradation was investigated. HNBR samples differing in bounded acrylonitrile (AN) content (34, 39 or 43 wt. %)(denoted with the symbols H34, H39 and H43, respectively) (Table 1) were irradiated with 10 MeV electron beam. Doses varied from 20 to 300 kGy. The following properties have been determined: Mooney-Rivlin elasticity constant (2C 1 N - Fig. 2), sol content (S - Fig. 3 and 4), radiation crosslinking efficiency (E) and gel dose (D g ) (Table 2). It was found HNBR undergoes radiation crosslinking and its network density is directly proportional to the dose (D). Bounded acrylonitrile content does not influence the processes of HNBR crosslinking and degradation. Ratio of scission acts (p) and crosslinking acts (q) has been determined using Charlesby-Pinner equation [equation (3)]. It has been found that the process of HNBR radiation crosslinking was accompanied with moderate degradation of the chains (p/q = 0.05-0.10, Table 2) going probably according to (3-scission mechanism. Relative intensity of absorption band at 810 cm - 1 related to >C=CH 2 end groups (Table 3) was determined by internal reflection spectroscopy (IRS).

With radiation crosslinking of engineering plastics into the next millennium

Abstract Much basic research has been done on the crosslinking behaviour of so-called “engineering plastics”. Up to now the industrial conversion to actual manufacture of multifunctional electronic components has gained ever increasing importance in the plastics industry and will continue to do so in the coming years. Examples of this are SMD (surface mounted device) technology, and 3D-MID (3-dimensional moulded interconnected devices) technology. These techniques require materials with high short-term temperature stability. In this paper it will be discussed which engineering plastics are significant for the radiation crosslinking process, for both technical and commercial reasons. The main topics will be the crosslinking behaviour of Polybutylenterephthalate (PBT) and Polyamide (PA). The importance and the challenges to the irradiation industry, as well as practical applications, will be shown.

Radiation crosslinking of poly(N-vinylimidazole) in aqueous solution in the presence of N,N′-methylene-bis-acrylamide

The effect of N, N′-methylene-bis-acrylamide (MbAA) concentration on the process of radiation crosslinking of poly( N-vinylimidazole) (PVI) in aqueous solutions of the polymer was investigated. Radiation doses range from 0.24 to 2.20 kGy for a polymer with a molecular weight M w =251,000 and at 8% w/v concentration with added crosslinking agent in the concentration range 0.1–1.0% w/v. For each irradiated sample extractions for definite periods of time were carried out. The kinetics curve of releasing sol fraction were drawn and absorption spectra of these fractions were recorded. The percent of sol fraction decreases with increasing radiation dose and MbAA concentration. Within the range of doses and MbAA concentrations used, the percent of sol fraction ranged from 23.9 to 54.0%. On the basis of the gel-sol analysis the gel doses ( D ∗) were determined. For 1% MbAA and 0.1% MbAA these doses are D ∗=0.026 kGy and D ∗=0.130 kGy respectively. From the values of the gel doses the radiation yield of crosslinking [ G( x)] was calculated. The radiation yields are relatively high and vary from G( x)=10 to 54.