Effect of electron beam radiation on tensile and viscoelastic properties of styrenic block copolymers

The effect of electron beam (E‐beam) radiation on a series of styrenic block copolymers (SBCs) was investigated. These SBCs included newly developed poly(styrene‐block‐isoprene/butadiene‐block‐styrene) (SIBS), poly(styrene‐block‐butadiene‐block‐styrene) (SBS), and poly(styrene‐block‐isoprene‐block‐styrene) (SIS). The tensile properties, stress relaxation, molecular weight, and dynamical mechanical properties were studied. Generally, the crosslink density and tensile moduli of SBCs increased with increasing of E‐beam radiation dose. The tensile strength of SIBS and SIS was shown to first decrease at lower E‐beam radiation dose (<120 kGy) and then increase at higher radiation dose (>190 kGy). The tensile strength of SBS was significantly decreased at high E‐beam radiation dose (>190 kGy). This was attributed to the differences between entanglement before E‐beam radiation and the homogeneity of the crosslink network after exposure. POLYM. ENG. SCI., 54:2979–2988, 2014. © 2014 Society of Plastics Engineers     

电子束辐射硫化的原理及应用

介绍电子束辐射硫化技术的原理和辐射剂量对橡胶物理性能的影响。与传统化学硫化工艺相比,电子束辐射硫化工艺可提高胶料耐老化性能,且硫化速度加快。以全钢和半钢子午线轮胎过渡层胶料为例,使用电子束辐射预硫化可减小过渡层胶料厚度或取消过渡层,在节省轮胎生产成本的同时,还可提高轮胎的均匀性和高速性能。     

Formation of polymeric microspheres using electron beam radiation

Polymeric particulates are currently being produced by a variety of different techniques. This new approach illustrates the formation of cross-linked polymeric microspheres by incorporating trimethylolpropane propoxylate triacrylate (a radiation-sensitive monomer) into a polyaphron system and exposing it to electron beam radiation. Polyaphrons are essentially a collection of droplets encapsulated in a very thin aqueous film dispersed in a aqueous matrix. This film gives extreme stability to the system, which allows for extremely high dispersed-phase concentrations. The formation of polyaphrons requires the presence of a surfactant in both the dispersed (monomer) and continuous (aqueous) phases. The effects of monomer-phase concentration, monomer- and acqueous-phase surfactant concentration, aqueous-phase surfactant type, and preparation temperature were studied to gain an understanding of the conditions that promote the formation of polymeric microspheres with a narrow size distribution. Polymeric microspheres ranging from 2 to 40 microns in diameter were formed with monomer concentrations as high as 67 vol % without any aphron bridging occurring or need for agitation to keep the monomer-phase dispersed in the aqueous matrix. In addition, the ability to reduce the wettability of the microspheres is demonstrated through incorporation of a polymerizable fluorinated acrylate in the dispersed phase.     

Effect of chemical composition upon the radiation and electron beam resist behaviors of vinyl polymers

Chemical composition effects upon polymer electron energy absorption and radiation chemistry have been identified to develop resist design criteria. By use of Bethe's theory for electron scattering in solids, chemical incorporation of higher atomic-numbered substituents is predicted to decrease energy absorption and increase scattering. Incorporation of chlorine or fluorine into vinyl polymers at the possible substituent sites is empirically found to have a large effect upon radiation G (scission) and G (crosslink) values. G (scission) values determined for several copolymers over a large range of compositions are found to vary linearly with composition. In contrast, G (crosslink) values are found to be generally less than those predicted from a linear extrapolation between the homopolymer values. Electron beam resist behavior is found to correlate well with the G_s/G_x ratio.     

Effect of electron beam radiation on mechanical and electrical properties of poly(ethylene-co-vinyl acetate)

Ethylene-vinyl acetate (EVA) copolymer (12% vinyl acetate content) is subjected to electron beam irradiation using trimethylolpropane trimethacrylate (TMPTMA) as a radiation sensitizer. Mechanical and electrical studies of these irradiated samples show that the strength properties (tensile strength, elongation at break) are increased with radiation dosage up to an optimum radiation dose and sensitizer level above which the properties begin to deteriorate. Crosslinking of the polymer takes place on irradiation which is attributed to an increased gel content with increasing radiation dose. Compared to the original samples both dielectric constant and dielectric loss factor decrease for samples subjected to irradiation.     

Effect of electron beam radiation on the mechanical and thermal properties of poly(4-methylpentene-1)

The changes in the mechanical and thermal properties of electron-beam-irradiated PMP of two different molecular weights (〈M_w〉 = 9.2 × 10⁵, 〈M_w〉 = 1.8 × 10⁶) have been studied. Electron beam (EB) irradiation was performed either in a nitrogen or air atmosphere to a maximum dosage of 40 Mrad. Stress–strain behavior of the irradiated materials show that the lower molecular weight polymer is more affected within this dose range than the higher molecular weight material. The modulus of both PMP materials (at 23°C), however, was not affected by EB. Moreover, it was observed that by increasing radiation dose up to 10 Mrad the occurrence of yielding disappeared in the case of the lower molecular weight system but was still found in the high molecular weight material up to 20 Mrad. The elongation at break of both PMP materials was systematically decreased by increasing the dose level. The rate of stress–relaxation of irradiated samples increased as dosage increased. It is believed that oxidative degradation is promoted as a result of irradiation which induces chain scission. This result was confirmed by GPC analysis which showed that, by increasing radiation dose, the molecular weight systematically decreased. DSC measurements used to investigate the changes in thermal properties showed that the melting temperature and heat of fusion decreased as the dose increased. An interesting feature of the DSC studies was the presence of an endothermic doublet in the melting behavior that transformed into a single peak following irradiation.     

高密度聚乙烯电子束辐射交联的研究

用高能电子束辐射技术研究了添加敏化剂季戊四醇三丙烯酸酯(PETA)和抗氧剂300的高密度聚乙烯(HDPE)体系的辐射交联效应.通过测定试样辐射后交联度、拉伸强度、直角撕裂强度等性能,考察了辐射剂量、w(PETA)和 w(300)对 HDPE辐射交联的影响;并用差示扫描量热法和热重分析研究了HDPE辐射后的结晶性和热稳定...     

Effect of electron beam irradiation on the dielectric properties of fluorocarbon rubber

Terpolymeric fluorocarbon rubber (68 wt.-% fluorine, 1.4 wt.-% hydrogen) was subjected to electron beam irradiation using 1,1,1-trimethylolpropane triacrylate (TMPTA), tripropylene glycol diacrylate (TPGDA), and pentaerythritol tetracrylate as radiation sensitizers. Compared to the original sample both the dielectric constant and the dielectric loss factor decrease for samples treated to a certain dose level, beyond which there is an increase. Similar improvement in dielectric properties is observed at relatively higher levels of TMPTA, owing to the increased degree of crosslinking. Among the various polyfunctional monomers used as radiation sensitizers, both the dielectric constant and the dielectric loss factor are higher for systems based on TPGDA due to the reduced crosslink density.     

Grafting of butyl acrylate and methyl methacrylate on butyl rubber using electron beam radiation

Being nonpolar in nature, butyl rubber (IIR) has poor compatibility toward polar polymers and fillers. It can be improved by grafting polar substrates on the butyl elastomer. Radiation‐induced polymer processing is getting increasing interest, as it leads to new and improved polymers with desirable and interesting properties. In this investigation, electron beam radiation has been used to graft methyl methacrylate (MMA) and butyl acrylate (BA) on IIR. This process has several advantages over conventional grafting processes such as cationic polymerization (which needs very low temperature and stringent reaction conditions) and solution radical polymerization (which often needs solvent removal and recycling). The grafted polymers were characterized by using ¹H NMR, IR, TGA, and SEM analysis. The degree of grafting increases with a decrease in irradiation dose as well as with an increase in monomer concentration. It was observed that there was a decrease in intrinsic viscosity in irradiated IIR samples, indicating the chain scission. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1340–1346, 2006     

Effect of electron beam radiation on structural changes of trimethylol propane trimethacrylate,ethylene vinyl acetate,and their blends

The effect of electron beam irradiation at different radiation doses (2, 5, 10, 15, and 20 Mrad) on trimethylol propane trimethacrylol propane trimethacrylate (TMPTMA), ethylene vinyl acetate (EVA, 12% vinyl acetate content), and their blends (0.5, 1, 1.5, 2, 2.5, 3, and 5 parts/100 parts EVA) was investigated. An IR study showed some residual unsaturations retained in irradiated pure TMPTMA, while in blends all unsaturations were used up at a very early stage of irradiation. The concentration of the carbonyl group due to air oxidation increased in pure EVA and blends, but it reached a maximum at the 1.5-part TMPTMA level and 5-Mrad dose. some ether linkages were formed during irradiation in pure EVA and the blends, although in pure EVA the concentration of ether linkages reached a maximum at the 2-Mrad dose and then decreased and in the blends it increased with an increase in radiation dose. Gel content showed an increasing trend with an increase in radiation dose, but it increased marginally with TMPTMA level. A blend of EVA with 1 part TMPTMA produced more gel than pure EVA at the same irradiation dose. © 1996 John Wiley & Sons, Inc.     

Influence of silica and electron beam radiation on the properties of a high vinyl styrene-butadiene-styrene block copolymer

Radiation crosslinking of polymers has gained importance over conventional crosslinking because the system is fast, pollution free and relatively simple. In high energy electron beam curing, which is one of the radiation curing methods, the material to be cured is bombarded with electrons of specified energy to produce free radials. These radicals unite to give rise to chemical crosslinks. In the process, some unwanted chain scission may also occur. The mechanical properties of such electron beam crosslinked systems can further be improved by the incorporation of nanosilica. In this work, a high vinyl (~50%) S-B-S block copolymer incorporated with varying doses of specific hydrophilic nanosilica was irradiated with electron beam at 25 and 50 kGy. Mechanical properties were studied and compared with that of the unirradiated system. The influence of a silane coupling agent was also investigated. Morphological studies were done to understand the dispersion of nanosilica in the polymer matrix. Relatively moderate amounts of nanosilica along with an optimum dose of the coupling agent were found to be effective in improving the properties. Rheological properties were also studied in details to understand the possibility of recycling the polymer.     

Electrical conductivity and infrared radiation performance of SiC-CNT composite ceramics

SiC ceramic is an excellent infrared source material that can be used in a wide range of fields, like infrared heating, night vision and communication, but its poor electrical properties limit it. In this work, carbon nanotubes (CNTs) were selected as conductive phase filler, and SiC-CNT composite ceramics were prepared by SPS method. The effects of CNT content on the microstructures, electrical properties and infrared radiation performance of the composites were studied. The introduction of CNT effectively reduced the height of Schottky barrier at grain boundary, thus weakening the grain boundary effect, reducing the grain boundary resistance, further weakening the nonlinear characteristics and bulk resistivity of the composite ceramics. When the content of CNT was 1 wt%, electrical percolation was achieved, and the bulk resistivity of SiC ceramics dropped by nearly 3 orders of magnitude. The preferred orientation distribution of CNT made the bulk resistivity perpendicular to the pressure direction R_⊥ always lower than that parallel to the pressure direction R_//. The sample with 5 wt% CNT assumed linear conductivity characteristics, with bulk resistivity in different direction of 16.5 Ω cm (R_//) and 11.8 Ω cm (R_⊥), respectively. CNT addition slightly increased the infrared radiation performance of SiC ceramics, and the sample with 5 wt% CNT possessed the highest total emissivity of 0.675. The excellent electrical conductivity and infrared radiation performance of SiC-CNT composite ceramic confirmed this class as a promising infrared source material.     

Effect of compatibilization on the performance of biodegradable composites using cotton fiber waste as filler

The usefulness of cotton waste as a source of reinforcing fibers for the preparation of cost‐effective and biodegradable composites has been investigated. Biodegradable polyester (bionolle 3020) is melt‐compounded together with cotton fibers. Maleic anhydride‐grafted bionolle (bionolle‐g‐MA) is used as a compatibilizer. The grafting reaction is carried out in an intensive mixer in the presence of dicumyl peroxide as initiator. The effects of fiber and compatibilizer content as well as graft content are evaluated by mechanical property measurements and scanning electron microscopy. The compatibilizer improved all mechanical properties significantly. Moreover, the water absorption and swelling of composites decreased, while the thermal stability increased slightly. Also, the biodegradation of the polyester bionolle 3020, as well as that of its composites with cotton fibers, were studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1825–1835, 2003     

Focused ion beam processing for transmission electron microscopy of composite/adhesive interfaces

Although most transmission electron microscope (TEM) investigations were carried out using conventional ultramicrotomy, they were limited to the tooth/adhesive resin interface and were difficult to accomplish for the resin-composite interface. Some of these limitations have been overcome with the introduction of focused ion beam (FIB) milling. Therefore, the objective of the study was to compare different composites/adhesive interfaces using FIB/TEM technique. Cylindrical cavities were prepared in extracted human molar teeth. The restored cavities were divided into four groups: (1) One-step self-etch Scotchbond Universal (SBU; 3M ESPE, USA), (2) all-in-one Xeno-V⁺ adhesive (X5P; DENTSPLY, Germany), (3) two-step etch-and-rinse Prime and Bond NT (PNT; DENTSPLY, Germany) that were restored with Filtek Supreme Ultra Universal composite (3M ESPE, USA), and (4) teeth restored with the two-step self-etch Filtek Silorane adhesive (SSA; 3M ESPE, USA) that were restored with its corresponding Filtek Silorane composite (3M ESPE, USA). All specimens were cross-sectioned and subjected to FIB preparation followed by composite/adhesive interfacial TEM examination. The TEM findings were variable and ranged from concentrated clusters of nanoparticles to phase separation of adhesive components and large osmotic blisters. The osmotic blisters in all-in-one adhesives appeared to be influenced by the presence of water and the solvent’s vapor pressure in the cavity. In conclusion, FIB/TEM is a powerful tool allowing the study of biomaterials interaction in situ. The absence of residual water in the adhesives may reduce osmotic blistering that, in turn, may improve the reactivity of the resin monomers, as well as interfacial bonding.     

Effect of electron beam irradiation on polyacrylonitrile precursor fibers and stabilization process

The electron beam was imposed on the polyacrylonitrile precursor fibers before the fibers were stabilized. The effect of electron beam irradiation on the chemical structure, transverse section, and surface morphology and thermal properties of the fibers in the process of stabilization was characterized by the use of Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and differential scanning calorimeter, respectively. A parameter η = I(C?N)/[I(C?N) + I(C?N)] was defined to evaluate the extent of cyclization in the stabilization process. The kinetic parameters, viz. activation energy (E) and pre‐exponential factor (A) of the stabilization reactions, were calculated by Kissinger method. FTIR analysis indicated that the cyclization of nitrile groups was initiated at room temperature by electron beam irradiation. The transformation of C?N groups to C?N ones was accelerated in the process of stabilization. The extent of cyclization of the stabilized fibers was increased. SEM analysis indicated that irradiation could also decrease the internal and surface defects of the stabilized fibers treated at 300°C. The activation energy of cyclization reaction was reduced from 302 to 280 kJ/mol and 260 kJ/mol through 100 and 200 kGy electron beam irradiation, respectively. The reaction temperature range was expanded, and the exothermic rate was slowed down in the process of stabilization, which was the reason why the stabilized fibers have improved cyclization degree and less internal defects. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of electron radiation on dyed PET and PA 66 substrates

PET and PA 66 fabrics were dyed with different disperse dyes under regular conditions. The dyed fabrics were irradiated with 180 kV electron radiation. It was observed that increasing radiation doses led to increasing total color differences dE if compared to the unirradiated materials. These color differences are mainly caused by two types of reactions. First by the reversible formation of dye radicals, which can be reoxidized (in air) to the original dye molecules, and second by the irreversible reaction of dye molecules with the fiber polymer. The latter reaction causes a permanent change of the color of the fabric, which can be kept low with the proper irradiation conditions. The decision whether or not this change can be tolerated depends on the further use of the textile.     

Effect of maleated polypropylene on the performance of polypropylene/cellulose composite

Composites consisting of a polypropylene (PP) and highly crystalline cellulosic microfibers were prepared by melting mixing with the maleic anhydride grafted polypropylene (MAPP) as a compatibilizer. The results show that even with addition of a small amount of MAPP, the mechanical properties of the composites improved dramatically. The improvement is attributed to stronger interfacial adhesion caused by esterification between anhydride groups of MAPP and hydroxyl groups of cellulose, although the number of the ester bonds is too few to be detected by FT‐IR spectroscopy. It was also found that tensile strength and Young's modulus increased with the increasing MAPP contents in the composites, and the optimum MAPP content is about 10 wt% for the composite with cellulose content of 30 wt%. SEM indicated that the interfacial adhesion between cellulose fibers and PP improved in MAPP‐containing composites. The DSC results showed that MAPP has little effect on melting and crystallization temperatures of PP in the composites. POLYM. COMPOS., 26:448–453, 2005. © 2005 Society of Plastics Engineers     

双氰胺对复合材料耐湿热性能的影响

介绍了双氰胺对环氧,碳纤维布复合材料耐湿热性能的影响．     

非离子表面活性剂对阳离子复合杀菌剂杀菌性能的影响

在棕榈油乙氧基化物(NOE-Pn)(n=3,6,9,12和14)质量浓度为50 mg/L的条件下,通过研究其EO加合数(n)对由双癸基二甲基甲酸铵(DDAF)、双烷基(碳数8~10)二甲基氯化铵(D8-10)、聚六亚甲基双胍盐酸盐(IB)、双癸基甲基羟乙基氯化铵(DEQ)和十二烷基二甲基苄基氯化铵(1227)5种阳离子表面活性剂复合组成的杀菌剂(阳离子复合杀菌剂,总质量浓度为140 mg/L,其中m(DDAF)∶m(D8-10)∶m(IB)∶m(DEQ)∶m(1227)=3∶2∶3∶3∶3)杀菌性能的影响,结果发现杀菌时间为20 min的条件下在n=9时(NOE-P9),对阳离子复合杀菌剂的影响最小,与脂肪醇聚氧乙烯(9)醚(AEO9)基本一致。在阳离子复合杀菌剂中引入非离子表面活性剂NOE-P9、AEO9和烷基糖苷(APG0810)以及阴-非离子表面活性剂脂肪醇聚氧乙烯(9)醚羧酸(AE9C),发现其对白色念珠菌的影响较大。在此基础上,对比了提高杀菌剂的总质量浓度至180 mg/L和延长杀菌时间至1 h的杀菌效果。结果发现浓度的提高使得杀菌性能略有增强;延长杀菌时间可以明显提升复合体系的杀菌效果,尤其是非离子表面活性剂质量浓度较低时,对金黄色葡萄球菌和大肠杆菌的杀灭对数值均大于6。     

Unique stimuli responsive characteristics of electron beam synthesized bacterial cellulose/acrylic acid composite

The formation and swelling behavior of bacterial cellulose/acrylic acid hydrogel prepared from aqueous mixture consists of 20 : 80 (v/v) acrylic acid (AAc) and 1% bacterial cellulose dispersion under accelerated electron beam was investigated. Gel fraction of hydrogel increased with the increasing dose suggesting a denser composite at 50 kGy compared to 35 kGy. SEM photomicrographs revealed a homogenous pores distribution at higher dose with pore sizes ranging from 1 to 5 μm. Hydrogel synthesized at lower dose of electron beam exhibited higher swelling ability and the degree of swelling increased as the pH of surrounding medium increased and it reached the optimum swelling at pH 7. While swelling of the hydrogel decreased with the increasing ionic strength of solution, swelling at different temperatures ranging from 25 to 50°C revealed a unique character where the hydrogel shrunk at 37°C. Moreover, hydrogel synthesized at higher dose exhibited a higher degree of swelling in methanol with respect to water. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010