Radiation processing of EPDM/PP blends

The effect of ionizing radiation on thermal oxidation of ethylene-propylene copolymer/polypropylene (EPDM/PP) was evaluated over the range of total gamma doses up to 250 kGy. The influence of irradiation dose on oxidation induction periods was investigated by oxygen uptake and thermal analysis on polymer samples containing various concentrations of components (100/0, 80/20, 40/60, 60/40, 20/80 and 100/0 w/w ). Drastic decrease in oxidation induction time was observed for low doses. The competition between crosslinking and scission has been examined on the basis of radical recombination on post-irradiation time. The influence of specimen formulations on oxidation induction time is discussed regarding to the contribution of antagonistic processes: crosslinking and oxidative degradation.     

Thermal stability of isotactic polypropylene modified with calcium carbonate nanoparticles

Thermal stability of isotactic polypropylene with or without calcium carbonate nanoparticles (nCaCO₃) was investigated by chemiluminescence under isothermal regime at 190 °C. Two kinds of nCaCO₃ particles, i.e., (neat and stearic acid-coated ones) were used. The contents of nCaCO₃ within the iPP/nCaCO₃ nanocomposites were 5, 10, 15, 20, and 25% w/w. Several parameters, i.e., oxidation induction time, oxidation half-time, maximum oxidation time, and oxidation rate were used to quantify the thermal stability of both the neat and the nCaCO₃-filled iPP systems. The contribution of nanoparticles on the progress of oxidation is discussed. It has been found that the concentration of nCaCO₃ increases the stability of systems when nanoparticles were covered, while the filler consisted of unmodified particles, the decrease in thermal strength with the increase in filler concentration was noticed.     

Radiation processing of polyolefin blends. I. Crosslinking of EPDM–PP blends

Radiation crosslinking of polymer blends containing the ethylene–propylene terpolymer (EPDM) and polypropylene (PP) was studied. Four binary systems with mixing ratios of 80/20, 60/40, 40/60, and 20/80 w/w and the individual components were γ‐processed. The development of the gel content formed in irradiated blends proved that the increase in PP concentration generated an increasing insoluble fraction. A linear dependence of the gel fraction on PP concentration was found. The optimal dose range for the efficient crosslinking of all EPDM/PP blends was 40–180 kGy. The use of PP customer waste was also examined. The thermal stability of the studied mixtures was assessed in order to state the contribution of the components to the radiation compatibilization of investigated polymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 982–987, 2000     

Kinetic effects of silica nanoparticles on thermal and radiation stability of polyolefins

The effects of γ-irradiation as the accelerated degradation procedure were analyzed for the evaluation of material stability. Low density polyethylene, polypropylene and ethylene–propylene terpolymer were studied in formulations with SiO₂ nanoparticles (2 and 5 wt%) or as neat materials. High energy irradiation (up to 100 kGy) has revealed a faster increase in the absorption of carbonyl band in comparison with the corresponding change in hydroperoxide band. The three studied materials present increased oxidation rates as the received energy transferred from incidental rays is enhancing, because the thermal regime of degradation depends on the structural characteristics, namely initial number of tertiary carbon atoms and unsaturation level. The fate of hydroperoxides as oxidation initiators is discussed.     

Photo- and thermal-oxidation of the nonwoven polypropylene fabric studied by FT-IR photoacoustic spectroscopy

The photo- and thermal-oxidation of a nonwoven polypropylene fabric was investigated using Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS). The infrared spectroscopic data indicate that alcohol, peroxide, aldehyde, ketone, carboxylic acid, and anhydride were formed as the products of the thermal oxidation and photooxidation of the polypropylene fabric. Ester was also formed during the thermal oxidation process. The thermal oxidation was accelerated after an initiation period. It was found that thermal oxidation occurred homogeneously between the surfaces of the fabric and its bulk. For the polypropylene fabric irradiated by ultraviolet (UV) radiation, however, the highest degree of oxidation occurred in the surface of the fabric facing the UV radiation source. It was also found that the UV radiation at 254 nm caused photooxidation of polyropylene. No photooxidation was observed in the fabric exposed to the UV radiation at 350 nm under the same conditions. © 1994 John Wiley & Sons, Inc.     

Evaluation of the oxidative stability of multiextruded polypropylene as assessed by physicomechanical testing and simultaneous differential scanning calorimetry–chemiluminescence

Common physicomechanical tests comprising impact strength, the melt flow index (MFI), and the yellowness index (YI) were used to study the thermooxidative stability of polypropylene (PP) following multipass extrusion. Differential scanning calorimetry (DSC) coupled with chemiluminescence (CL) monitoring was also used to assess the stability. Three PP formulations were studied: (i) PP‐1 containing 0.050% w/w of the phenolic antioxidant Irganox 1010^™, (ii) PP‐2 containing 0.028% w/w Irganox 1010, 0.056% w/w of the phosphite costabilizer Irgafos 168^™ and 0.014% w/w of the lactone processing stabilizer HP 136^™, and (iii) PP‐3 containing 0.050% w/w Irganox 1010 and 0.100% w/w of the phosphite Ultranox 641^™. All formulations contained 0.045% w/w of the hydrotalcite acid scavenger DHT‐4A^™. The results suggest that physicomechanical tests cannot reliably detect the small difference in the stability between PP‐2 and PP‐3 but can detect the larger difference between these and the less stable PP‐1. The oxidative induction time (OIT) determined by CL monitoring (i.e., CL– OIT) is consistent with the OIT determined by DSC but has better reliability. The CL–OIT data suggest that PP‐3 has superior oxidative stability to PP‐2 in the early stages of multipass extrusion. However, PP‐2 exhibits a better resistance to yellowing. A correlation between the CL–OIT data and each of the MFI and YI data was found. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 733–741, 2001     

Effect of electron radiation dose on oxidation of surface layers of polyethylene,polypropylene and poly(ethylene terephthalate) films

The results of oxidation of surface layers of irradiated films made of low-density polyethylene (LDPE), isotactic biaxially oriented polypropylene (BOPP) and poly(ethylene terephthalate) (PET) are discussed. The films were modified in the air atmosphere using a high-energy electron beam generated by a linear accelerator. Oxidation of surface layers of 3.7 nm thickness upon doses of up to 500 kGy was investigated by X-ray photoelectron spectroscopy. It was found that the extents of oxidation were ca. 22, 11 and 8% for BOPP, LDPE and PET, respectively.     

不同受阻胺光稳定剂改性聚丙烯耐光老化性能研究

分析了4种受阻胺光稳定剂在聚丙烯(PP)加工过程中的热稳定性,并研究其单一和复合使用对PP其光稳定性能和力学性能的影响。以失重率为10%时的热分解温度衡量受阻胺光稳定剂的热稳定性,结果表明,受阻胺光稳定剂的加入,使PP的光稳定性能增强;高低分子量受阻胺复合使用,可降低PP的黄变因数和羰基指数,增加其拉伸强度及冲击强度保持率;GW622、GW944和Tinuvin144复合使用效果最佳。     

Some special aspects of thermal ageing of isotactic polypropylene (measuring method: Isothermal long-term DTA)

Thermo-oxidative ageing processes were investigated in films (100 μm thick) made from isotactic polypropylene with different antioxidant concentrations between 0% and 0.1% using isothermal long-term differential thermal analysis (ILDTA). The end of the oven life of polypropylene coincided with the loss of mechanical properties which was confirmed by tensile tests at temperatures far below the crystallite melting range. Already prior to the beginning of autocatalytic decomposition, ILDTA experiments permits conclusions to be drawn on the thermal history of the specimens and statements made regarding the end of thermo-oxidative stability of the polymer, which is accompanied by a deterioration in the mechanical properties. In consequence of the correlation between oxidation time and antioxidant concentration the local antioxidant concentration in sheets or films can be measured by ILDTA. Thus, investigating the diffusion of an antioxidant in polypropylene using ILDTA is possible.     

Chemiluminescence study on HALS antioxidant activity in LDPE

Summary The kinetic study on thermal degradation of stabilised low density polyethylene by chemiluminescence investigations was performed. Four hindered amine light stabilisers, additive compounds, were used as thermal protector on polymer substrate. The experiments were carried out on the samples consisting of polyetylene and 0.25% (w/w) of hindered amine. Three temperatures (180, 190 and 200 °C) were selected for this assay allowing the calculation of the activation energy required for thermal oxidation of polyethylene matrix. A discussion on mechanistic aspects concerning the antioxidant efficiency of studied compounds is also presented.     

Improvement of Mechanical Properties of Jute Fibers-Polyethylene/Polypropylene Composites: Effect of Green Dye and UV Radiation

Jute-reinforced polyethylene (PE), polypropylene (PP) and mixture of PP/PE composites were prepared. It was found that 90% PP and 10% PE matrices based jute reinforced composites performed the better results. UV radiation at different intensities was applied both on matrices and jute. Mechanical properties of the irradiated jute- and matrices-based composites were found to increase significantly. Optimized jute fabrics were also treated with different concentrations of green dye (0.1–1%, w/w) with 2% K₂O₈S₂ in methanol solution for 2–8 min. A composite made of 0.5% green dye jute (5 min soaking time) and irradiated matrix showed the best mechanical properties.     

Inorganic–organic hybrid materials prepared from zirconium oxo‐clusters and 2‐hydroxyethyl methacrylate

This article describes the preparation and characterization of hybrid materials obtained from the polymerization of vinyl‐substituted zirconium oxo‐clusters [Zr₆O₄(OH)₄(OOCCH₂CHCH₂)₁₂(n‐PrOH)]₂·4(CH₂CHCH₂COOH) (Zr12) and 2‐hydroxyethyl methacrylate (HEMA). The zirconium oxo‐clusters serve as cross‐linking agents, forming a 3D network by means of the copolymerization of their vinylic ligands with HEMA. To optimize the conditions for cross‐linking, the polymerization was monitored with a differential scanning calorimeter. The resulting hybrid materials were also characterized using thermo‐mechanical techniques. There was evidence not only of a greater rigidity above T_g, but also of a better thermal stability for several hybrid formulations than for simple poly‐2‐hydroxyethyl methacrylate. After immersion in water, the hybrids containing 20 or 60% w/w zirconium oxo‐clusters also showed a stable behavior with an equilibrium swelling at about 27 and 18% w/w of water, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41568.     

Cure of epoxy novolacs with aromatic diamines. I. Vitrification,gelation, and reaction kinetics

The cure reaction of a commercial epoxidized novolac with 4,4' diaminodiphenylsulfone (DDS) was studied at constant cure temperatures in the range 120–270°C, as well as at constant heating rates (differential scanning calorimetry, DSC). Stoichiometric formulations did not attain complete conversion due to the presence of topological restrictions. The limiting conversion was x_max = 0.8. Samples containing an amine excess (≥ 20%) could be completely reacted, whereas this was not possible for formulations containing an epoxy excess. Samples containing a 20% amine excess showed the maximum value of the glass transition temperature (T_g230°C). Cure took place by epoxy-amine hydrogen reactions catalyzed by (OH) groups. A reactivity ratio of secondary to primary amine hydrogens equal to 0.2 was found. The activation energy was E = 61 kJ/mol, as arising from T_g versus time shift factors and time to gel measurements. A unique relationship between T_g and x could be obtained. Gelation took place at x_gel = 0.45 and the maximum T_g for the stoichiometric system was T_gmax = 215°C for x = 0.8. A conversion versus temperature transformation diagram was used to represent conditions where gelation, vitrification, degradation, and topological limitations took place. © 1993 John Wiley & Sons, Inc.     

Improvement of corrosion protection of steel by incorporation of a new phosphonated fatty acid in a phosphorus-containing polymer coating obtained by UV curing

Six formulations containing diacrylate monomers (from 89 to 92.5% (w/w)) as well as a phosphonated methacrylate monomer (from 1 to 10% (w/w)) were prepared. All formulations were UV-cured and the corrosion performance of the resulting coatings applied onto a steel substrate was assessed by electrochemical impedance spectroscopy (EIS). It was first shown that the coatings containing phosphonic acid methacrylate (MAPC1(OH)₂) instead of methacrylate phosphonic dimethyl ester (MAPC1) presented higher corrosion protection related to the strong adhesive properties of phosphonic acid on the metal substrate. A minimum MAPC1(OH)₂ content of 2.5% was determined to provide the highest impedance values (best efficiency). Then, a new bio-based compound, i.e. phosphonic acid-bearing oleic acid (phosphonated fatty acid), was synthesized and added as an inhibitor to the formulations. In the presence of this compound, the corrosion protection was notably improved. The beneficial effect of phosphonated fatty acid was explained by its inhibitive action at the steel/coating interface and by the improvement of the barrier properties.     

Thermal stability of additivated isotactic polypropylene

Summary Isotactic polypropylene stabilised with fullerene [C60], its adduct with methyl levopimarate, carbon black, p-t-butylcalix[4]arene, p-t-butylcalix[6]arene, Irganox 1076 or Topanol OC was investigated by means of oxygen uptake method under isothermal (165^°C) and isobaric (normal pressure) conditions. Oxidation investigations were performed in air as degradation environment. Additive concentration was 0.25 % (w/w). Kinetic parameters, oxidation induction and oxidation rate are compared with similar characteristics of additive-free i-PP. Effect of γ-irradiation on thermal oxidation is also presented. Three γ-exposure doses (50, 100 and 150 kGy) were selected. The influence of radiation treatment on the efficiency of studied compounds and some mechanistic aspects are also presented. Received: 5 June 2002/Revised version: 10 August 2002/ Accepted: 12 September 2002 Correspondence to Traian Zaharescu     

Accelerated degradation of highly loaded polypropylene

The accelerated aging of six formulations of polypropylene highly loaded with calcium carbonate and containing a surfactant additive (stearic acid) as well as an ultraviolet (UV) stabilizer was studied. Degradation was followed by measuring mechanical properties (elongation percentage and impact resistance), the dynamic mechanical behavior and some chemical changes such as molecular weight and carbonyl group formation along with oxidation temperatures, found by chemiluminescence. The addition of 30 phr of filler to the polymer reduced the stability of the mixture, and the stearic acid used to treat the filler enhanced this effect considerably. On the other hand, the addition of the photostabilizer controlled to some extent such negative effects, though not completely. The most stable formulation was the polypropylene containing only the UV stabilizer.     

Amine-functionalized metal–organic frameworks/epoxy nanocomposites: Structure-properties relationships

Amine-functionalized MIL-101(Cr)-NH₂ metal–organic frameworks (MOF-N)/epoxy nanocomposites with Excellent cure label and high thermal stability were developed. Structure–property relationship was discussed by comparison of the cure state, thermal and viscoelastic behavior of epoxy nanocomposites containing pristine MOF or MOF-N applying differential scanning calorimetry (DSC), thermogravimetric analysis, and dynamic mechanical analysis. Epoxy containing 0.3 wt% MOF-N exhibited high glass transition temperature (T_g) of 96°C compared with 85°C observed for epoxy/MOF system. Thus, MOF-N played the role of catalyst in epoxy/amine curing reaction. Correspondingly, a lower activation energy was obtained based on cure kinetics modeling based on DSC measurements. Besides, incorporation of low amount (0.5 wt%) MOF-N induced an early-state resistance against decomposition, featured by 11°C rise in decomposition temperature at 5% weight loss. This was ascribed to the formation of porous metallic oxides during thermal decomposition of MOF-N in the epoxy system acting as a heat barrier, which increased the activation energy of decomposition. Amine-functionalization considerably prevented from further oxidation of the inner part of the matrix.     

Effect of crosslinking monomers on the performance of electron beam-induced biodegradable Bionolle–rubber blends

To find out the better crosslinking monomer for vulcanization of natural rubber under electron beam (EB) radiation, the dry rubber was masticated with different polyfunctional monomers like TMPTA, NVP, and ethylene glycol diacrylate of different numbers of CH₂ CH₂ O group, such as 1G, 3G, 7G, and 10 G. The masticated films were irradiated with different doses under EB at 10 kGy/pass. The highest tensile strength (25 MPa) of the rubber was observed in the presence of TMPTA (3phr) at 150 kGy dose. The gel content of the rubber increased with an increase of dose. Bionolle was mixed with the masticated rubber containing 3 phr TMPTA at different proportions; films of these blends along with Bionolle were irradiated under EB with different doses. The concentration of rubber in Bionolle and radiation dose were optimized. The elastomer with 5% masticated showed the highest tensile strength (62 MPa). The gel content of the blends was found to increase with an increase of radiation dose as well as rubber concentration in Bionolle. The elastomers or blends were found to possess good thermal properties. The elastomers exhibited a much lower loss of tensile strength due to the thermal aging compared with pure Bionolle. The elastomers sustained their original shape for 300 min at 180°C, whereas Bionolle sustained its shape for only 3 min at 120°C under the same load (50 g). Among all the elastomers, 5% rubber containing elastomer was found to be better in all respects. It was observed from scanning electron microscopy and differential scanning calorimetry studies that 5% rubber is well mixed with Bionolle. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 799–807, 2001     

不同胺基CO2固体吸收剂的热稳定性能

为应对温室效应对全球气候的影响,CO₂的捕集和封存(carbon capture and storage,CCS)技术成为近年来的研究热点.我国能源消费结构以煤为主,煤燃烧排放的CO₂约占我国CO₂排放总量的82%^[1],主要用于发电.因此研究燃煤电站烟气中脱除CO₂的技术具有重要意义.     

Improving Thermal Stability and Electrical Insulation of Gamma‐Irradiated Silicone Rubber Nanocomposites

Room temperature vulcanized silicone rubber (RTVSR) nanocomposites were prepared by mixing of surface‐modified montmorillonite nanoclay or nano fumed silica, or both of them with RTVSR to improve thermal stability, electrical insulation, and flame retardant. Their tensile strength, elongation, swelling, and solubility properties at different doses of gamma radiation were investigated to study the effect of gamma radiation on the properties of the nanocomposites. The thermal stability, flammability properties, and volume resistivity of the nanocomposites were also investigated. The nanocomposite which containing fumed silica has the best thermal, mechanical properties, electrical insulation and fire retardancy. The thermal characteristics, namely, T_onset, T_10%, T_comp, and T_max, of the nanocomposite sample containing fumed silica were 22, 23, 13, and 11 °C higher than those of the blank, respectively. The tensile strength (TS) increased when the radiation dose was increased up to 100 kGy, but elongation, swelling, and solubility decreased when the radiation dose was increased up to 150 kGy. It can be generally concluded that the nanocomposites containing fumed silica and irradiated to 100 kGy are characterized by having outstanding mechanical, thermal, fire retardant, and electrical insulation properties and hence, they may have wide industrial applications as good thermal and electrical insulating materials. J. VINYL ADDIT. TECHNOL., 26:354–361, 2020. © 2019 Society of Plastics Engineers