Structure and mechanical properties of isotactic polypropylene and iPP/talc blends functionalized by electron beam irradiation

The structure and mechanical properties of isotactic polypropylene (iPP) functionalized by electron beam irradiation are investigated by differential scanning calorimetry, wide‐angle X‐ray diffraction, thermogravimetry, thermomechanical analysis, melt index and mechanical measurements. The experimental results show that the degree of crystallinity, the thermal degradation temperature and the dimensional stability increase with dose in the range 0–5 kGy. At 5 kGy, the initial and final degradation temperatures of the irradiated iPP are raised by 66 °C and 124 °C, respectively. The melt index increases with increasing dose. The mechanical measurements show that the stiffness of iPP is greatly enhanced by electron beam irradiation. A small dose of irradiation (0.75 kGy) can increase the Young's modulus to 1284 MPa compared with 1112 MPa for unirradiated iPP. Adding 10 % by weight of irradiated iPP powder into iPP/talc (70/20 % by weight) blends, changes the processing parameters significantly and makes the Young's modulus rise substantially. At a dose of 40 kGy the Young's modulus of iPP/talc blend jumps to 3611 MPa against the original 2201 MPa. © 2000 Society of Chemical Industry     

Thermal stability of electron beam-irradiated polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) was subjected to 1 MeV electron beam irradiation in air. The thermal stability and the degradation fragments of the irradiated polymer were studied in dependence on the radiation dose up to 4 MGy by thermogravimetric analysis coupled with mass spectrometry. The TGA results confirm the known decrease in the thermal stability of irradiated PTFE with increasing radiation dose. At the thermal degradation, CO₂, HF, and fluorocarbon fragments are evolved from the irradiated samples. CO₂ and HF are formed by decomposition of peroxy radicals up to 250°C. In addition, low molecular weight fluorocarbons are desorbed from the irradiated PTFE. At temperatures above 300°C, CO₂ is formed by the decarboxylation of radiation-induced COOH groups inside the PTFE. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2287–2291, 1997     

Surface modification of PTFE by 60Co γ-ray irradiation

Surface carboxyl groups were formed during the ⁶⁰Co γ-ray irradiation of poly(tetrafluoroethylene) (PTFE) in air. Fourier transform infrared spectroscopy enables the detection of surface carboxyl groups. The contact angles were used to calculate the dispersive and polar components of the surface free energy according to a two-liquid method. The γ-ray irradiation of PTFE mainly caused degradation of the polymer. The concentration of carboxyl groups, the wettability, the friction, and the dispersive and polar components of the surface energy and the crystallinity on PTFE surface were increased, while the particle size of PTFE decreased with increasing irradiation dose. A highly modified PTFE was used to reduce the aqueous liquid repellent properties of PTFE. A 20 kGy dose for modified PTFE surface was suitable in air additivity in antifriction, anticorrosion, antifouling, lubrication, and noise reduction coatings. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 435–441, 1998     

Radiation grafting of vinyl monomers onto poly(tetrafluoroethylene) powder produced by γ irradiation and properties of grafted poly(tetrafluoroethylene) filled low density polyethylene

Scrap poly(tetrafluoroethylene) (PTFE) was γ irradiated under an ambient atmosphere in order to produce extensive chain scission and oxidative degradation. After irradiation the PTFE was ground into a fine powder (2°‐PTFE) and grafted with styrene (St), vinyl acetate (VAc), and 4‐vinylpyridine (4‐VP) by using the direct irradiation technique. The grafted PTFE were then blended with low density polyethylene (LDPE). The study covered the characterization of irradiated PTFE and grafted 2°‐PTFE powder with various methods. Mechanical grinding was found to reduce trapped radicals formed during the irradiation process faster than the annealing process. Grafting on 2°‐PTFE was followed by gravimetric analysis, TGA, and the change in the particle size of the samples. Although we reached almost 20% grafting by weight in the St and 4‐VP monomers, VAc grafting was found to be maximum at around 8% by weight at the maximum absorbed dose. The addition of VAc grafted 2°‐PTFE into LDPE produced better final mechanical properties with a fine dispersion. However, as may be expected, the incorporation of the other two 2°‐PTFEs into LDPE showed low film quality and poor mechanical properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 816–826, 2001     

Effect of electron beam radiation on the performance of biodegradable Bionolle-jute composite

To study the radiation effect on the physical, thermal, mechanical and degradable properties of biodegradable polymer Bionolle (chemosynthetic polyester poly(1,4-butylene succinate)), Bionolle films prepared by compression molding process and were irradiated with electron beam (EB) radiation of different doses. Gel content was found to increase with increase of radiation dose. Tensile strength of Bionolle was enhanced when Bionolle film was exposed under 20 kGy radiation. The loss of tensile strength of both unirradiated and irradiated Bionolle is 70% and 8% due to thermal aging at 70°C for 30 days. Both irradiated and unirradiated films of Bionolle were subjected to different degradation test in compost (soil burial), enzyme and storage degradation both in outdoor and indoors conditions. The loss of weight due to soil (compost) degradation test decreased with increase of radiation dose. The loss of weights of irradiated samples were found to be very less within the first three months of compost degradation. After 120 days, tensile strength of the Bionolle films irradiated at 20 kGy and 100 kGy were 68 MPa and 40 MPa, respectively, compared to the value (30 MPa) of the unirradiated Bionolle samples. Loss of tensile strength of irradiated Bionolle due to storage degradation like in roof, ground and indoors was minimum compared to unirradiated Bionolle. The weight loss due to enzymatic degradation was found to be decreased with increase of radiation dose. The tensile strength of jute reinforced Bionolle composites (23 wt.-% jute content) irradiated at 20 kGy was found to be higher (22%) than that of an unirradiated composite.     

Functionalization of irradiated PTFE micropowder with methacryl‐ or hydroxy groups for chemical coupling of PTFE with different matrix polymers

This article describes the modification of electron beam irradiated polytetrafluoroethylene (PTFE) material (500 kGy) into a functionalised micropowder, bearing methacrylate or hydroxy groups. The aim of this work is to achieve compatibilization of modified PTFE in a variety of matrix polymers, such as elastomers and duromers. It is well known that irradiation of high molecular PTFE in the presence of air, followed by annealing with water vapor, leads to a functionalization of the PTFE micropowder, containing carboxylic acid groups. For sufficient stability of the coupling of the functional groups that are to be introduced via these acid groups, a transformation into amide groups is necessary, and can be performed by the reaction of the electron beam irradiated PTFE with ε‐caprolactam in the first step. The corresponding acid‐terminated PTFE–oligoamide is then reacted with functional epoxy monomers, like glycidol or glycidyl methacrylate, to obtain the functionalised PTFE micropowders (PTFE‐OH and PTFE‐MA). As the number of COOH groups in the electron beam irradiated PTFE is not very high, IR‐spectroscopic identification of the functional groups is not very distinct. To find evidence for the existence/reactivity of the additionally introduced functional groups, model reactions have been performed, where PTFE‐MA is reacted with methyl methacrylate/AIBN. IR spectroscopic analysis of the reaction products shows characteristic absorption bands of PMMA, indicating successful graft polymerization of PMMA to PTFE‐MA. For PTFE‐OH, reaction with cyclohexylisocyanate leads to a bisurethane adduct, which shows a strong urethane absorption in the IR spectrum. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2819–2824, 2006     

The irradiation impacts of high gamma doses on optical features and degradation of Makrofol DE 1-1

The induced impacts of high doses of gamma irradiations on the optical features of the Makrofol DE 1-1 detector were studied in the ultraviolet and visible range (from 270 to 500 nm). Makrofol DE 1-1 detector specimens were irradiated separately for different doses from 200 to 1000 kGy; step 200. The optical absorbance spectra of the pristine Makrofol DE 1-1, as well as the irradiated gamma-ray samples display two main features: (i) A redshift with further gamma-ray irradiation doses from 200 to 1000 kGy. This redshift can be ascribed to irradiation-induced defects in polymer material. (ii) A remarkable increment in the optical absorbance for irradiated Makrofol DE 1-1 specimens compared to the pristine one. This increment can be ascribed to the creation of some electronic levels within the forbidden gap resulting from the irradiation process. Moreover, this absorbance increment was employed to assess the degradation percent produced by gamma-ray irradiations. The degradation percent of the Makrofol DE 1-1 increased from 31.73% at 200 kGy to 78.08% at 1000 kGy. The optical band gap, Fermi level and metallization criterion showed decrement behaviors with further doses of gamma-ray irradiations. Also, the percent of changes in optical band gap values were employed to evaluate the degradation of Makrofol DE 1-1 under gamma-ray irradiations. This percent augmented from 15.19% at 200 kGy to 20.25% at 1000 kGy proving the obvious degradation of Makrofol DE 1-1 under gamma-ray irradiations. On the other hand, the number of carbon atoms per cluster, linear and nonlinear refractive indices showed increasing behaviors with further doses of gamma-ray irradiations.     

Radiation modification of functional properties in PVC/mica electrical insulations

Summary The effects of γ-irradiation on poly(vinyl chloride) blended with fillers (plasticizer, lead stabilizer and mica) are presented. Mechanical and electrical investigations were carried out on samples that received doses of maximum 160 kGy. The results on tensile strength, volume resistivity and loss factor prove that poly(vinyl chloride) may be used as electrical insulator after short γ-exposure. Because mica plays a role of absorbent for hydrochloric acid formed by PVC degradation, favorable properties are obtained for dose up to 120 kGy. The volume resistivity decreases constantly while tan δ remains unchanged for a large frequency range (10²–10⁵ cps). Mica content of 14% induces a decrease in unirradiated PVC of one order of magnitude. After irradiation at 160 kGy volume resistivity increases of about five times relative to 40 kGy irradiated samples. At 150 kGy tensile strength decreases only with 10%, and elongation at break presents a light modification in the selected dose range. The largest differences between the maximum current values obtained for applied doses are presented by PVC with the highest concentration of mica (14%). At 40 kGy, when the degradation becomes relevant, the dipoles are not efficiently trapped by mica and the current does not attend a steady state for a long period (more than half an hour). For higher doses the steady-state current is reached after only 1–3 minutes, due to crosslinking. Some considerations concerning the consequences of high energy exposure of poly(vinyl chloride) on electrical behaviour are presented.     

Degradation by Electron Beam Irradiation of Some Composites Based on Natural Rubber Reinforced with Mineral and Organic Fillers

Composites based on natural rubber reinforced with mineral (precipitated silica and chalk) and organic (sawdust and hemp) fillers in amount of 50 phr were obtained by peroxide cross-linking in the presence of trimethylolpropane trimethacrylate and irradiated by electron beam in the dose range of 150 and 450 kGy with the purpose of degradation. The composites mechanical characteristics, gel fraction, cross-linking degree, water uptake and weight loss in water and toluene were evaluated by specific analysis. The changes in structure and morphology were also studied by Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. Based on the results obtained in the structural analysis, possible mechanisms specific to degradation are proposed. The increasing of irradiation dose to 450 kGy produced larger agglomerated structures, cracks and micro voids on the surface, as a result of the degradation process. This is consistent with that the increasing of irradiation dose to 450 kGy leads to a decrease in crosslinking and gel fraction but also drastic changes in mechanical properties specific to the composites’ degradation processes. The irradiation of composites reinforced with organic fillers lead to the formation of specific degradation compounds of both natural rubber and cellulose (aldehydes, ketones, carboxylic acids, compounds with small macromolecules). In the case of the composites reinforced with mineral fillers the degradation can occur by the cleavage of hydrogen bonds formed between precipitated silica or chalk particles and polymeric matrix also.     

Reactive polytetrafluoroethylene/polyamide 6 compounds. II. Study of the reactivity with respect to the functionality of the polytetrafluoroethylene component and analysis of the notched impact strength of the polytetrafluoroethylene/polyamide 6 compounds

The formation of block copolymers as a result of an in situ chemical reaction during the reactive extrusion of electron‐beam‐irradiated polytetrafluoroethylene (PTFE) and polyamide 6 (PA) was detected indirectly with differential scanning calorimetry and Fourier transform infrared. As expected, the content of the block copolymers in the compound increased as the irradiation dose was increased. The notched impact strength showed an increase in the PTFE/PA compounds produced with highly irradiated PTFE. This behavior is discussed in the context of the degree of dispersion of the PTFE phase (as reported in part I of this series) and the adhesion changed by the in situ reaction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1317–1324, 2005     

电子束辐照降解氯苯类废水

氯苯类是重要的有机污染物,采用常规处理方法难以降解。利用束流为1mA、电子束能量为1 5MeV的高能电子束辐照处理氯苯、邻,间,对 二氯苯、1,2,4 三氯苯5种氯苯类化合物的模拟废水。辐照剂量分别为35、70、105、140、210kGy。实验表明,电子束能够降解氯苯类废水,邻二氯苯、间二氯苯、对二氯苯、氯苯降解率为50%时所需剂量分别为:38、35、46、206kGy。相同剂量下各化合物的降解率顺序为:氯苯<二氯苯<1,2,4 三氯苯,辐照降解过程中氯离子的质量浓度增加,辐照后溶液呈强酸性,pH=2～3。     

Properties of biodegradable hydrogels prepared by γ irradiation of microbial poly(ϵ-lysine) aqueous solutions

Poly(?-lysine) (PL) hydrogels have been prepared by means of γ irradiation of PL produced by Streptomyces albulus in aqueous solutions. When the dosage of γ irradiation was 70 kGy or more and the concentration of PL in water was 1–7 wt %, transparent hydrogels (opaque hydrogels for 1–3 wt % PL concentration) could be produced. In the case of 70 kGy of γ irradiation and 5 wt % PL concentration, the specific water content (wt of absorbed water/wt of dry hydrogel) of the PL hydrogel was approximately 160. Specific water contents of PL hydrogels decreased markedly with an increase in the dosage of γ irradiation. The specific water contents were increased with an increase in PL concentration in the irradiated solution. This result indicates the presence of a radical scavenger in the PL solution. Swelling equilibria of PL hydrogels were measured in water or in aqueous solutions of various pHs or concentrations of NaCl, Na₂SO₄, and CaCl₂. Under acid conditions, the PL hydrogel swelled due to the ionic repulsion of the protonated amino groups in the PL molecules. The degree of deswelling in electrolyte solution was smaller than that of other ionic hydrogels [poly(γ-glutamic acid), poly(acrylic acid) etc.]. In addition, the enzymatic degradations of PL hydrogel were studied at 40°C and pH 7.0 in an aqueous solution of the neutral protease [Protease A (Amano)] produced from Aspergillus oryzae. The rate of enzymatic degradation of the respective PL hydrogels was much faster than the rate of simple hydrolytic degradation. The rate of enzymatic degradation decreased with the increase in γ-irradiation dose during preparation of the PL hydrogel. © 1995 John Wiley & Sons, Inc.     

Energetic polymer subjected to high energy radiation

PolyNIMMO is regarded as an energetic polymer. It consists of a nitrated ester group and an ether linkage. When polyNIMMO is subjected gamma radiation up to doses of 250 kGy there is no evidence of degradation, however, at higher levels of gamma radiation up to 750 kGy structural changes in the polyNIMMO backbone were observed [Polymer 44 (2003) 7617-7624]. These observations were based on polyNIMMO which was gamma irradiated in the bulk phase [Polymer 44 (2003) 7617-7624; Polymer 42 (2001) 7711-7718]. The results presented in investigation are from polyNIMMO which has been irradiated in solution. PolyNIMMO dissolved in halogenated and aromatic solvents was found to undergo structural changes when subjected to doses of gamma radiation up to 250 kGy. An increase in molecular weight and glass transition temperature was observed with the formation of water and an aldehyde. End chain linking together with hydrogen abstraction of the pendant methyl group were the two suggested reaction schemes.     

Specific characteristics of infrared spectra of irradiated γ-polypropylene

Nonvolatile products have been identified that arise through γ-irradiation in isotactic polypropylene by Fourier transform infrared (FTIR) analysis. The γ-irradiation was performed in the air with doses varying between 20 and 1200 kGy, for a dose rate of 800 Gy/h. The contour lines of FTIR absorption bands of carbonyl groups at different region of the cross section of an irradiated sample have been determined. The carbonyl groups arise from the concentration of esters or ketones, carboxylic acids, and γ-lactones, but their structure is different for different doses. We have also investigated the degradation of irradiated polypropylene by using FTIR mappings. Dust particles of irradiated brittle polypropylene have also been studied. The gel fraction has been determined for different doses of irradiation, and the relation between the moment of the appearance of the gel and disappearance of the carbonyl groups has been made evident. © 1996 John Wiley & Sons, Inc.     

Gamma irradiated orange peel for Cr(VI) bioreduction

This work presents the γ irradiation (600–3500 kGy) and acid hydrolysis onto orange peel for hexavalent chromium removal. SEM, AFM, TGA-DSC, FTIR, and UV-Vis showed that γ rays enhance degradation and cleavage of orange peel cellulose polymeric chains, increasing the presence of reducing sugars after acid hydrolysis (0.1552 g/g biomass, 3500 kGy). Bioreduction kinetics of Cr(VI) using both solid and solubilized liquid fractions of γ irradiated biomass showed a direct correlation between the applied dose and Cr(VI) removal, reaching 100% of Cr(VI) reduction at pH 2 and 3500 kGy. Cr(VI) reduction is explained as a function of hydrolyzed reducing sugar oxidation.     

A new approach for the preparation of chitosan from γ‐irradiation of prawn shell: effects of radiation on the characteristics of chitosan

Chitosan is a biodegradable polymer composed of randomly distributed β‐(1,4)‐linked D ‐glucosamine (deacetylated unit) and N‐acetyl‐D ‐glucosamine (acetylated unit). It is produced commercially by deacetylation of chitin, which is the structural element in the exoskeleton of crustaceans (such as crabs and shrimps) and the cell walls of fungi. In the work reported, we developed a facile technique for the preparation of chitosan by irradiating prawn shell at various intensities from 2 to 50 kGy. It was observed that γ‐irradiation of prawn shell increased the degree of deacetylation (DD) of chitin at a relatively low alkali concentration during the deacetylation process. Among the various irradiation doses applied to prawn shell, a dose of 50 kGy and 4 h heating in 50% NaOH solution yielded 84.56% DD while the chitosan obtained from non‐irradiated prawn shell with the same reaction conditions had only 74.70% DD. In order to evaluate the effect of γ‐irradiation on the various physicochemical, thermomechanical and morphological properties, the chitosan samples were again irradiated (2–100 kGy) with γ‐radiation. Molecular weight, DD, thermal properties with differential scanning calorimetry and thermogravimetric analysis, particle morphology by scanning electron microscopy, water binding capacity (WBC), fat binding capacity (FBC) and antimicrobial activity were determined and the effects of various γ‐radiation doses were assessed. The DD, WBC, FBC and antimicrobial activity of the chitosan were found to improve on irradiation. It was obvious that irradiation caused a decrease of molecular weight from 187 128 to 64 972 g mol^?1 after applying a radiation dose of 100 kGy which occurred due to the chain scission of chitosan molecules at glycosidic linkages. The decrease of molecular weight increased the water solubility of the chitosan, the extent of which was explored for biomedical applications. Copyright © 2012 Society of Chemical Industry     

Properties of melt processable PTFE/PEEK blends: The effect of reactive compatibilization using electron beam irradiated melt processable PTFE

For the first time, blends of melt processable polytetrafluoroethylene (MP PTFE) with polyetheretherketone (PEEK) in the MP PTFE/PEEK ratio of 100/0, 80/20, 50/50, 20/80, and 0/100 w/w were prepared and characterized. MP PTFE/PEEK blends are attractive materials due to the combination of low coefficient of friction and universal chemical resistance of MP PTFE with good wear resistance and mechanical strength of PEEK while maintaining high thermal stability of both. Miscibility, phase morphology, and mechanical properties of the new MP PTFE/PEEK blends were investigated. To improve their end‐use properties, an attempt of reactive compounding with the electron beam irradiated MP PTFE (e‐beam MP PTFE) was made. The reactive compounding was done in two steps, that is, the preparation of a masterbatch (MB) consisting of e‐beam MP PTFE/PEEK (50/50 w/w) and subsequent melt blending of MP PTFE/PEEK with varying concentrations of MB. The e‐beam irradiation of MP PTFE carried out in air atmosphere and at room temperature with a dose of 50 kGy results in its chain scission associated with formation of ? COF and ? COOH functional groups. Such modified MP PTFE can be used to compatibilize MP PTFE/PEEK blends. Reactive compatibilized blends exhibit improved phase morphology and mechanical properties. Especially for MP PTFE/PEEK 50/50 blends, a great improvement of almost 250% in strain at break, 40% in stress at break, and more than 600% in toughness was achieved. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal analysis of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) irradiated under vacuum

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) was irradiated by ⁶⁰Co γ‐rays (doses of 50, 100 and 200 kGy) under vacuum. The thermal analysis of control and irradiated PHBV, under vacuum was carried out by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The tensile properties of control and irradiated PHBV were examined by using an Instron tensile testing machine. In the thermal degradation of control and irradiated PHBV, a one‐step weight loss was observed. The derivative thermogravimetric curves of control and irradiated PHBV confirmed only one weight‐loss step change. The onset degradation temperature (T_o) and the temperature of maximum weight‐loss rate (T_p) of control and irradiated PHBV were in line with the heating rate (°C min^?1). T_o and T_P of PHBV decreased with increasing radiation dose at the same heating rate. The DSC results showed that ⁶⁰Co γ‐radiation significantly affected the thermal properties of PHBV. With increasing radiation dose, the melting temperature (T_m) of PHBV shifted to a lower value, due to the decrease in crystal size. The tensile strength and fracture strain of the irradiated PHBV decreased, hence indicating an increased brittleness. Copyright © 2004 Society of Chemical Industry     

Reactive polytetrafluoroethylene/polyamide compounds. I. Characterization of the compound morphology with respect to the functionality of the polytetrafluoroethylene component by microscopic and differential scanning calorimetry studies

Compounds of electron‐beam‐irradiated polytetrafluoroethylene (PTFE) and polyamide (PA) were produced by reactive extrusion. During extrusion, both a breakdown process of the PTFE agglomerates and a chemical reaction between PTFE and PA took place. The morphology of the compounds was characterized with differential scanning calorimetry using fractionated crystallization, with atomic force microscopy and scanning electron microscopy, and with dynamic light scattering. The particle size of the dispersed PTFE phase decreased as the irradiation dose increased. A simple theoretical model of the breakdown process of PTFE agglomerates was made for the discussion of the development of the observed degree of dispersion. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1308–1316, 2005     

Radiation–chemical modification of PTFE in the presence of graphite

PTFE with a 15% addition of graphite was subjected to irradiation using an electron beam of 10 MeV energy with absorbed doses of 26, 52, 78, 104, and 156 kGy. The effect of electron‐beam irradiation on the mechanical, sclerometic, and tribological properties, the crystallinity degree, and the morphology of the polymer surface was examined. It was found that the modification through irradiation entailed a gradual increase in the degree of crystallinity, which had a direct influence on the mechanical properties. An increase in the hardness, Young's modulus, and compressive strength of the polymer irradiated with an electron beam was also demonstrated. The electron‐beam irradiation reduced the value of components of the work‐of‐indentation, showing the growing resistance to deformation. An analysis of the scratch test parameters showed a reduced depth of penetration of the indenter into the material, proportionally to the irradiation value, at relatively constant values of the scratch depth after scratching load removal. A stereometric analysis of the scratch traces on the material allowed to determine coefficients of the wear micromechanism, β, and resistance to wear, W_β. It was found that after irradiation (especially with a dose of 4 × 26 kGy), a significant quantity of the material showed traces of ploughing, which meant a positive effect on the wear mechanism. The value of the wear resistance coefficient W_β for PTFE subjected to the absorbed irradiation dose increased intensively, which portended a significant reduction of the tribological wear compared to the nonirradiated material. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42348.