J. Reyes - Academia.edu (original) (raw)
Papers by J. Reyes
The additives are intended to increase the lifetime of the polymers. However the exposition to nu... more The additives are intended to increase the lifetime of the polymers. However the exposition to nuclear radiations and the oxidative atmosphere storage induces chemical changes of the additives added to macromolecules which generate modifications in its physical and chemical properties that affect the stability of these materials. In this paper our attention is focused on the degradation processes induced by ageing and gamma irradiation on polystyrene/polypropylene (PS/PP) (80/20) blends with and without compatibilizer styrene-butadiene-styrene (triblock SBS) at 20wt%after 5 years of air storage irradiated with gamma rays from a 60Co source at a dose rate of 4.8 kGy/h and at a integral irradiation dose of 10, 25 and 50 kGy in the presence of air at room temperature (RT =298oK). The effect of ageing and gamma irradiation on the polymers studied was measured by electron spin resonance (ESR) spectroscopy 7 days after the gamma irradiation. The dependence of resonance line, Hpp, the reso...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2001
Electron spin resonance investigations on polycarbonate irradiated with uranium ions are reported... more Electron spin resonance investigations on polycarbonate irradiated with uranium ions are reported. The dependence of the resonance line parameters (line intensity, line width, double integral) on penetration depth and dose is studied. The nature of free radicals induced in polycarbonate by the incident ions is discussed in relation with the track structure. The presence of severe exchange interactions among free
Molecular Crystals and Liquid Crystals, 2004
We have exposed the Polypropylene + virgin-High Density Polyethylene + woodflour and Polypropylen... more We have exposed the Polypropylene + virgin-High Density Polyethylene + woodflour and Polypropylene + recycled-High Density Polyethylene + woodflour composites under gamma irradiation to integral doses from 10 to 70 kGy at the constant dose rate of 4.8 kGy/h. ESR Spectroscopy was carry out. The nature of free radicals after two days of air storage induced by gamma irradiation is
Materials for Biomedical Engineering, 2019
Abstract In this book chapter the authors give a complete vision of both natural and synthetic po... more Abstract In this book chapter the authors give a complete vision of both natural and synthetic polymeric materials used in a general sense, but mainly in the medical area. In addition explain the mechanisms the main failure mechanisms ultrahigh molecular weight polyethylene UHMWPE and background for this situation. Likewise, a visualization of the current and future biopolymers used in medicine is also given. Biopolymers are used in medicine in order to replace part of a living system. Chitosan, cellulose, DNA, RNA, bioplastics made from soya, starch, bio polyethylene, biopolyesthers, are interesting for medical applications. Moreover, polyamides (nylon 6/6) and polypropylene are disposed as suture material and as syringes. Medical grade UHMWPE, is the main material used clinically in orthopedics. Nanomaterials are currently used successfully in drug delivery applications. Nanobiomaterials are currently used successfully in drug delyvery applications. Natural biopolymers and bioplastics will be used in the future because they are biodegradable and environmentally sustainable.
Revista de la Facultad de Ingenieria
The present investigation has the purpose of characterize the ultra high molecular weight polyeth... more The present investigation has the purpose of characterize the ultra high molecular weight polyethylene (UHMWPE-Gur- 1050), irradiated at 100 and 50 kGy in argon atmosphere at 25ºC, and at a rate of 4.8 kGy/h; After that, they were stored in vitamin E at a concentration of 0.1 wt%. In order to obtain better properties for the use in orthopedics, the samples irradiated at 100 kGy where annealing at 120ºC and the ones at 50 kGy at 140ºC. The crosslinking predominant reactions, in the case of 140ºC remelting temperature, has a greater effect than at 120ºC, showing also greater hardness and resistance to compression, In spite of that they showed a 10% decreasing in the Young module. The FTIR analysis shows a lesser relation of carbonyl groups, related to the transvilidenes groups. It was not found the presence of oxidant species by means of UV and ESR spectroscopy. From the results, can be inferred that the UHMWPE, remelted at 140ºC is more appropriated for the design and manufacturing o...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
ABSTRACT Luminescence investigations on polycarbonate irradiated with accelerated uranium ions ar... more ABSTRACT Luminescence investigations on polycarbonate irradiated with accelerated uranium ions are reported. The dependence of luminescence spectra on the penetration length, deposited energy and dose and track radius is investigated. The luminescence spectrum has been assigned to phenyls. It is suggested that most phenyls are located within the latent track. The experimental results are in good agreement with data obtained by electron spin resonance spectroscopy.
Polymer Degradation and Stability, 2003
Electron spin resonance investigations on collagen irradiated with protons are reported. The reso... more Electron spin resonance investigations on collagen irradiated with protons are reported. The resonance spectra were assigned to a convolution of lines due to $ CH 2-CH 2 residues and peroxy radicals. Raising the temperature of the sample (in air), the concentration of $ CH 2-CH 2 residues decreases while, the concentration of peroxy radicals increases due to the denaturation induced enhancement of the oxidation process. An increase in the apparent intensity of the recorded spectrum has been observed around 100 C and ascribed to the release of adsorbed water molecules.
Polymer Degradation and Stability, 2001
In this work, the thermal degradation of PP blends with previously treated sisal fiber (10mm), an... more In this work, the thermal degradation of PP blends with previously treated sisal fiber (10mm), and γ irradiated in air at different doses (10, 25, 50, 60, 70 kGy), is studied. The treatment to which sisal fibers were previously submitted were: (a) the addition of a coupling agent (Silane A-172), 1% by weight, (b) a chemical treatment at different times
Materials Research Innovations, 2001
The effect of the gamma-irradiation on the mechanical properties of the composites, Polypropylene... more The effect of the gamma-irradiation on the mechanical properties of the composites, Polypropylene (PP), PP+high density Polyethylene (HDPE), PP+ HDPE+wood flour, where HDPE is virgin and recycled, was studied. This paper discusses the behavior of the composites after exposure to various doses of gamma irradiation (1–7 MRads) in the presence of oxygen. The dependence of mechanical properties on the integral
Ciencia, 2006
In ves ti ga cio nes me dian te es pec tros co pía de re so nan cia pa ra mag né ti ca elec tró n... more In ves ti ga cio nes me dian te es pec tros co pía de re so nan cia pa ra mag né ti ca elec tró ni ca en la de gra da ción de la mez cla PS/PP (80/20) 30wt% SBS con 0,1% Recy clos tab 811, irra dia da con ra yos gamma, des pués de 4 años de al ma ce na mien to en at mós fe ra de oxí ge no Ernesto Da vid son 1 *, Jacobo Re yes-Ro me ro 2 , Delfín Mo ron ta 3 y Rosalba Scia ma nna 3
Interciencia
The effects of gamma rays (50 and 100kGy), storage in vitamin E 0.1%, and annealing heat treatmen... more The effects of gamma rays (50 and 100kGy), storage in vitamin E 0.1%, and annealing heat treatment at 130°C on the medical grade ultra high molecular weight polyethylene (UHMWPE- Gur-1050) were studied after irradiation and storage at 24°C, by measuring the mechanical properties of wear, hardness and compression, the gel fraction, the Fourier transform infrared (FTIR), ultraviolet (UV) and electron spin resonance (ESR) spectroscopies and the thermal analysis of differential scanning calorimetry (DSC). The medical grade UHMWPE is a material widely used for implants in orthopedics. Results show that the experimental conditions improve the properties of the material as a result of the stabilization and recombination of free radicals by the effect of ¿-tocopherol, reaching an optimal crosslinking of 34.5% at 100kGy. Significant improvements were found, of 17% in volumetric wear resistance and 21% in the friction coefficient, respectively, and of ~17% in hardness. FTIR and near UV show a...
Polymer Degradation and Stability, 2001
The aim of this work was to analyze by means of simple mathematical models the effect of differen... more The aim of this work was to analyze by means of simple mathematical models the effect of different integral doses of g irradiation on the mechanical properties of blends of polypropylene (PP) with virgin and recycled high density polyethylene (v-HDPE, r-HDPE), with and without woodflour-type filler. Analysis of the results at an integral irradiation dose between 0 and 50 kGy shows that crosslinking predominates in the PP/v-HDPE blend whereas degradation is predominant in the PP/r-HDPE blend, due to the characteristics of the recycled material. For the 50-70 kGy interval, both blends (PP/v-HDPE, PP/r-HDPE) suggest the possibility of competing processes, chain breaking being the most marked in the PP/r-HDPE blend. For the 0-50 kGy range in the blends with woodflour, the behavior of the PP/v-HDPE/woodflour composite was more complex since the polynomial equations are of third order for both tensile properties analyzed: Young's modulus and elongation at break. The behavior of the PP/r-HDPE/woodflour composite is complex suggesting simultaneous crosslinking and degradation. Both composites show a bimolecular process within the 50-70 kGy range which signifies a second-order dependence.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
The effect of gamma irradiation on the tensile behavior of the polystyrene/polypropylene (PS/PP) ... more The effect of gamma irradiation on the tensile behavior of the polystyrene/polypropylene (PS/PP) blend (80/20) without and with styrene-butadiene-styrene (SBS) points to a deterioration of the mechanical properties of the blends due to the scission and crosslinking reactions resulting from irradiation. A kinetic analysis of the behavior of mixtures of PS/PP with SBS shows that a radiation dose between 70 and 400 kGy, the dominant process is the chain scission meanwhile at higher doses appear a competitive mechanisms (chain scission and crosslinking) with a sensitive decrease of the properties in the break point.
International Journal of Polymeric Materials and Polymeric Biomaterials, 1994
Electron spin resonance investigations of the thermo-oxidative degradation of trans-polypentename... more Electron spin resonance investigations of the thermo-oxidative degradation of trans-polypentenamer rubbers, containing various stabilizers, are reported. The dependence of the resonance line parameters on the degradation time and temperature as well as the effect of various stabilizers on the resonance line are studied in detail. The activation energies for the generation of free radicals, the reaction order for the overall
Composite Structures, 2005
The aim of the present work was the recycling of rubber from automobile tyre treads, as a partial... more The aim of the present work was the recycling of rubber from automobile tyre treads, as a partial substitute of fine aggregates in concrete. Composites obtained were characterized by destructive and non-destructive testing, in order to find a liable application. According to results obtained, it was found that when weight proportion increased and particle size of scrap rubber decreased (0.59 and 0.29 mm), flow and density of composite in the fresh state decreased, as well as compressive strength and splitting tensile strength in the dry state. Previous treatment of rubber with NaOH and silane (A-174) did not produce significant changes on compressive strength and splitting tensile strength of composites, when compared to the untreated rubber-concrete composite. On the other hand, from the behavior showed by the ultrasonic pulse velocity with time, one can infer that the addition of rubber decreased this variable, being the effect more notorious when rubber content increased. This was due to the greater volume that rubber occupies, as well as water absorption. It can be concluded that the ultrasonic pulse velocity was relatively independent of particle size and coupling agent employed.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
Electron spin resonance investigations on the free radicals generated in polystyrene by gamma irr... more Electron spin resonance investigations on the free radicals generated in polystyrene by gamma irradiation, in the temperature range 300-460 K, are reported. Assuming the competition between first and second order recombination processes, the isothermal decay of free radicals has been accurately fitted. It is proved that both the first and the second order isothermal reaction rates are well described by a Vogel-Fulcher-Tamman-Arrhenius equation.
The additives are intended to increase the lifetime of the polymers. However the exposition to nu... more The additives are intended to increase the lifetime of the polymers. However the exposition to nuclear radiations and the oxidative atmosphere storage induces chemical changes of the additives added to macromolecules which generate modifications in its physical and chemical properties that affect the stability of these materials. In this paper our attention is focused on the degradation processes induced by ageing and gamma irradiation on polystyrene/polypropylene (PS/PP) (80/20) blends with and without compatibilizer styrene-butadiene-styrene (triblock SBS) at 20wt%after 5 years of air storage irradiated with gamma rays from a 60Co source at a dose rate of 4.8 kGy/h and at a integral irradiation dose of 10, 25 and 50 kGy in the presence of air at room temperature (RT =298oK). The effect of ageing and gamma irradiation on the polymers studied was measured by electron spin resonance (ESR) spectroscopy 7 days after the gamma irradiation. The dependence of resonance line, Hpp, the reso...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2001
Electron spin resonance investigations on polycarbonate irradiated with uranium ions are reported... more Electron spin resonance investigations on polycarbonate irradiated with uranium ions are reported. The dependence of the resonance line parameters (line intensity, line width, double integral) on penetration depth and dose is studied. The nature of free radicals induced in polycarbonate by the incident ions is discussed in relation with the track structure. The presence of severe exchange interactions among free
Molecular Crystals and Liquid Crystals, 2004
We have exposed the Polypropylene + virgin-High Density Polyethylene + woodflour and Polypropylen... more We have exposed the Polypropylene + virgin-High Density Polyethylene + woodflour and Polypropylene + recycled-High Density Polyethylene + woodflour composites under gamma irradiation to integral doses from 10 to 70 kGy at the constant dose rate of 4.8 kGy/h. ESR Spectroscopy was carry out. The nature of free radicals after two days of air storage induced by gamma irradiation is
Materials for Biomedical Engineering, 2019
Abstract In this book chapter the authors give a complete vision of both natural and synthetic po... more Abstract In this book chapter the authors give a complete vision of both natural and synthetic polymeric materials used in a general sense, but mainly in the medical area. In addition explain the mechanisms the main failure mechanisms ultrahigh molecular weight polyethylene UHMWPE and background for this situation. Likewise, a visualization of the current and future biopolymers used in medicine is also given. Biopolymers are used in medicine in order to replace part of a living system. Chitosan, cellulose, DNA, RNA, bioplastics made from soya, starch, bio polyethylene, biopolyesthers, are interesting for medical applications. Moreover, polyamides (nylon 6/6) and polypropylene are disposed as suture material and as syringes. Medical grade UHMWPE, is the main material used clinically in orthopedics. Nanomaterials are currently used successfully in drug delivery applications. Nanobiomaterials are currently used successfully in drug delyvery applications. Natural biopolymers and bioplastics will be used in the future because they are biodegradable and environmentally sustainable.
Revista de la Facultad de Ingenieria
The present investigation has the purpose of characterize the ultra high molecular weight polyeth... more The present investigation has the purpose of characterize the ultra high molecular weight polyethylene (UHMWPE-Gur- 1050), irradiated at 100 and 50 kGy in argon atmosphere at 25ºC, and at a rate of 4.8 kGy/h; After that, they were stored in vitamin E at a concentration of 0.1 wt%. In order to obtain better properties for the use in orthopedics, the samples irradiated at 100 kGy where annealing at 120ºC and the ones at 50 kGy at 140ºC. The crosslinking predominant reactions, in the case of 140ºC remelting temperature, has a greater effect than at 120ºC, showing also greater hardness and resistance to compression, In spite of that they showed a 10% decreasing in the Young module. The FTIR analysis shows a lesser relation of carbonyl groups, related to the transvilidenes groups. It was not found the presence of oxidant species by means of UV and ESR spectroscopy. From the results, can be inferred that the UHMWPE, remelted at 140ºC is more appropriated for the design and manufacturing o...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
ABSTRACT Luminescence investigations on polycarbonate irradiated with accelerated uranium ions ar... more ABSTRACT Luminescence investigations on polycarbonate irradiated with accelerated uranium ions are reported. The dependence of luminescence spectra on the penetration length, deposited energy and dose and track radius is investigated. The luminescence spectrum has been assigned to phenyls. It is suggested that most phenyls are located within the latent track. The experimental results are in good agreement with data obtained by electron spin resonance spectroscopy.
Polymer Degradation and Stability, 2003
Electron spin resonance investigations on collagen irradiated with protons are reported. The reso... more Electron spin resonance investigations on collagen irradiated with protons are reported. The resonance spectra were assigned to a convolution of lines due to $ CH 2-CH 2 residues and peroxy radicals. Raising the temperature of the sample (in air), the concentration of $ CH 2-CH 2 residues decreases while, the concentration of peroxy radicals increases due to the denaturation induced enhancement of the oxidation process. An increase in the apparent intensity of the recorded spectrum has been observed around 100 C and ascribed to the release of adsorbed water molecules.
Polymer Degradation and Stability, 2001
In this work, the thermal degradation of PP blends with previously treated sisal fiber (10mm), an... more In this work, the thermal degradation of PP blends with previously treated sisal fiber (10mm), and γ irradiated in air at different doses (10, 25, 50, 60, 70 kGy), is studied. The treatment to which sisal fibers were previously submitted were: (a) the addition of a coupling agent (Silane A-172), 1% by weight, (b) a chemical treatment at different times
Materials Research Innovations, 2001
The effect of the gamma-irradiation on the mechanical properties of the composites, Polypropylene... more The effect of the gamma-irradiation on the mechanical properties of the composites, Polypropylene (PP), PP+high density Polyethylene (HDPE), PP+ HDPE+wood flour, where HDPE is virgin and recycled, was studied. This paper discusses the behavior of the composites after exposure to various doses of gamma irradiation (1–7 MRads) in the presence of oxygen. The dependence of mechanical properties on the integral
Ciencia, 2006
In ves ti ga cio nes me dian te es pec tros co pía de re so nan cia pa ra mag né ti ca elec tró n... more In ves ti ga cio nes me dian te es pec tros co pía de re so nan cia pa ra mag né ti ca elec tró ni ca en la de gra da ción de la mez cla PS/PP (80/20) 30wt% SBS con 0,1% Recy clos tab 811, irra dia da con ra yos gamma, des pués de 4 años de al ma ce na mien to en at mós fe ra de oxí ge no Ernesto Da vid son 1 *, Jacobo Re yes-Ro me ro 2 , Delfín Mo ron ta 3 y Rosalba Scia ma nna 3
Interciencia
The effects of gamma rays (50 and 100kGy), storage in vitamin E 0.1%, and annealing heat treatmen... more The effects of gamma rays (50 and 100kGy), storage in vitamin E 0.1%, and annealing heat treatment at 130°C on the medical grade ultra high molecular weight polyethylene (UHMWPE- Gur-1050) were studied after irradiation and storage at 24°C, by measuring the mechanical properties of wear, hardness and compression, the gel fraction, the Fourier transform infrared (FTIR), ultraviolet (UV) and electron spin resonance (ESR) spectroscopies and the thermal analysis of differential scanning calorimetry (DSC). The medical grade UHMWPE is a material widely used for implants in orthopedics. Results show that the experimental conditions improve the properties of the material as a result of the stabilization and recombination of free radicals by the effect of ¿-tocopherol, reaching an optimal crosslinking of 34.5% at 100kGy. Significant improvements were found, of 17% in volumetric wear resistance and 21% in the friction coefficient, respectively, and of ~17% in hardness. FTIR and near UV show a...
Polymer Degradation and Stability, 2001
The aim of this work was to analyze by means of simple mathematical models the effect of differen... more The aim of this work was to analyze by means of simple mathematical models the effect of different integral doses of g irradiation on the mechanical properties of blends of polypropylene (PP) with virgin and recycled high density polyethylene (v-HDPE, r-HDPE), with and without woodflour-type filler. Analysis of the results at an integral irradiation dose between 0 and 50 kGy shows that crosslinking predominates in the PP/v-HDPE blend whereas degradation is predominant in the PP/r-HDPE blend, due to the characteristics of the recycled material. For the 50-70 kGy interval, both blends (PP/v-HDPE, PP/r-HDPE) suggest the possibility of competing processes, chain breaking being the most marked in the PP/r-HDPE blend. For the 0-50 kGy range in the blends with woodflour, the behavior of the PP/v-HDPE/woodflour composite was more complex since the polynomial equations are of third order for both tensile properties analyzed: Young's modulus and elongation at break. The behavior of the PP/r-HDPE/woodflour composite is complex suggesting simultaneous crosslinking and degradation. Both composites show a bimolecular process within the 50-70 kGy range which signifies a second-order dependence.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
The effect of gamma irradiation on the tensile behavior of the polystyrene/polypropylene (PS/PP) ... more The effect of gamma irradiation on the tensile behavior of the polystyrene/polypropylene (PS/PP) blend (80/20) without and with styrene-butadiene-styrene (SBS) points to a deterioration of the mechanical properties of the blends due to the scission and crosslinking reactions resulting from irradiation. A kinetic analysis of the behavior of mixtures of PS/PP with SBS shows that a radiation dose between 70 and 400 kGy, the dominant process is the chain scission meanwhile at higher doses appear a competitive mechanisms (chain scission and crosslinking) with a sensitive decrease of the properties in the break point.
International Journal of Polymeric Materials and Polymeric Biomaterials, 1994
Electron spin resonance investigations of the thermo-oxidative degradation of trans-polypentename... more Electron spin resonance investigations of the thermo-oxidative degradation of trans-polypentenamer rubbers, containing various stabilizers, are reported. The dependence of the resonance line parameters on the degradation time and temperature as well as the effect of various stabilizers on the resonance line are studied in detail. The activation energies for the generation of free radicals, the reaction order for the overall
Composite Structures, 2005
The aim of the present work was the recycling of rubber from automobile tyre treads, as a partial... more The aim of the present work was the recycling of rubber from automobile tyre treads, as a partial substitute of fine aggregates in concrete. Composites obtained were characterized by destructive and non-destructive testing, in order to find a liable application. According to results obtained, it was found that when weight proportion increased and particle size of scrap rubber decreased (0.59 and 0.29 mm), flow and density of composite in the fresh state decreased, as well as compressive strength and splitting tensile strength in the dry state. Previous treatment of rubber with NaOH and silane (A-174) did not produce significant changes on compressive strength and splitting tensile strength of composites, when compared to the untreated rubber-concrete composite. On the other hand, from the behavior showed by the ultrasonic pulse velocity with time, one can infer that the addition of rubber decreased this variable, being the effect more notorious when rubber content increased. This was due to the greater volume that rubber occupies, as well as water absorption. It can be concluded that the ultrasonic pulse velocity was relatively independent of particle size and coupling agent employed.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
Electron spin resonance investigations on the free radicals generated in polystyrene by gamma irr... more Electron spin resonance investigations on the free radicals generated in polystyrene by gamma irradiation, in the temperature range 300-460 K, are reported. Assuming the competition between first and second order recombination processes, the isothermal decay of free radicals has been accurately fitted. It is proved that both the first and the second order isothermal reaction rates are well described by a Vogel-Fulcher-Tamman-Arrhenius equation.