Devulcanization of ethylene‐propylene‐diene polymer residues by microwave—Influence of the presence of paraffinic oil

Vulcanized rubbers are materials commonly used in various industrial applications. In this study, scraps of ethylene‐propylene‐diene rubber (EPDM‐r) from the automotive industry were submitted to different microwave exposure times (2–5 min). Samples of recycled rubber with (as received) and without (after extraction) paraffinic oil were analyzed. The devulcanized EPDM‐r was characterized by gel content, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The gel content indicated that the presence of paraffin oil in EPDM‐r affects the devulcanization process. The DSC analysis showed significant changes in the glass transition temperature (Tg). The Tg values for EPDM‐r decreased with an increase in the microwave exposure time. Furthermore, the presence of a thermal phenomenon characteristic of uncured material was observed. Sample degradation was studied through TGA, and the values for the activation energy (E_a) of the degradation process were determined using the Flynn‐Wall‐Ozawa method. For conversions up to 0.10, the E_a values of the EPDM‐r samples without oil decreased with an increase in the microwave exposure time. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Thermogravimetric analysis of methyl methacrylate‐graft‐natural rubber

The thermal degradations of methyl methacrylate‐graft‐natural rubber (MG) at different heating rates (B) in nitrogen were studied by thermogravimetric analysis. The results indicate that the thermal degradation of MG in nitrogen is a one‐step reaction. The degradation temperatures increase along with the increment of heating rates. The temperature of initial degradation (T₀) is 0.448B + 362.4°C, the temperature at maximum degradation rate, that is, the peak temperature on a differential thermogravimetric curve (T_p) is 0.545B + 380.7°C, and the temperature of final degradation (T_f) is 0.476B + 409.4°C. The degradation rate at T_p is not affected by B, and its average value is 48.9%; the degradation rate at T_f is not affected by B either, and its average value is 99.3%. The reaction order (n) is 2.1 and is not affected by B. The reaction activation energy (E) and the frequency factor (A) increase along with B, and the apparent reaction activation energy (E₀) is 254.6 kJ/mol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2952–2955, 2002     

Roles of Calcium,Zinc, Copper and Titanium Compounds on the Degradation of Polymers

In this article, the influences of the metallic filler content upon the thermal degradability of polymer composites such as initial degradation temperature, maximum degradation temperature and char content have been critically reviewed using thermogravimetric analysis. Besides that, the review on the relationship between activation energies of polymer/metal composites, which was obtained from various degrade models, and the content of metallic fillers have also been defined. Other thermal properties such as glass transition temperature (T_g) and melting temperature (T_m) have also been reviewed based on the evaluation of differential scanning calorimetry (DSC) analysis.     

Adhesion degradation of rubber and steel insert for conveyor belts

The problem of degradation of rubber in conveyor belts is very important because they incorporate a lot of rubber and have a high value. In the paper we have analyzed the situation of rubber conveyor belts reinforced with metal insertions because it was found that they can sometimes be obsolete pretty fast due to the degradation of the connection between the metal insertion and the rubber matrix. The theoretical study performed followed modeling the bond between the metal insert and the rubber matrix and obtained a relationship for calculating the rate of degradation n _d of the connection between the metal insertion and the rubber matrix. The evolution in time of the degradation of the connection between the metal insertion and the rubber matrix has also been established, and this was carried out during 2.5?years of use of a conveyor belt type ST 3150. To analyze the degradation of the rubber from the conveyor belt, rubber hardness was determined for seven distinct points on the belt thickness at intervals of 0.5?years and was also determined at the same intervals of time the evolution of specific resistance of tearing of the metal insertion from the rubber matrix.     

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     

Thermal degradation study of interpenetrating polymer network based on modified bismaleimide resin and cyanate ester

Interpenetrating polymer networks (IPNs) based on different ratios of a modified bismaleimide resin (BMI/DBA) and cyanate ester (b10) have been synthesized via prepolymerization followed by thermal curing. A systematic thermal degradation study of these new BMI/DBA‐CE IPN resin systems was conducted by thermogravimetric analysis at different heating rates both in N₂ (thermal stability) and in air (thermal‐oxidative stability). The cured BMI/DBA‐CE IPN resin systems show excellent thermal stability, which could be demonstrated by 5% weight loss temperature (T_5%) ranging between 409 and 423 °C, maximum decomposition rate temperature (T_max) ranging between 423 and 451 °C, and the char yields at 800 °C ranging from 37% to 41% in nitrogen at a heating rate of 10 °C min^?1. The apparent activation energy associated with the main degradation stage of the cured BMI/DBA‐CE IPN resin systems was determined using the Kissinger method. The obtained results provide useful information in drawing correlation between thermal properties and structure. © 2003 Society of Chemical Industry     

Thermooxidative degradation of natural rubber/clay composite

The clay is treated with a reducing agent and an acid so as to obtain a clay containing various metal components with a variable‐valence state. Then, the clay is coprecipitated with natural rubber (NR) latex to prepare a vulcanized NR/clay composite. The degradation process of the NR/clay composite under hot air condition was studied dynamically by using a Fourier transform infrared spectrometer attaching an in situ sample cell and was also investigated using the TGA method. The test result obtained from the infrared spectrometry indicated that under low decomposition temperature, the decomposition products of the test samples mainly are ethylene, low molecular olefinic hydrocarbon, and carbonyl compounds. As the decomposition temperature rises, the low molecular olefinic hydrocarbon content decreases, the olefine with longer chain is formed, and a lot of alkane decomposition products are formed at the same time. When the content of the metal components with a variable‐valence state in clay such as Cu, Mn, Co, and Fe increases, the oxidation products containing the carbonyl group, the olefinic hydrocarbon, and CO₂ in the decomposition product of the test sample also increase. The TGA result clearly shows a shoulder peak that appears by the side of the main peak on the DTG curve of NR/clay composite. With the increase in the content of metal components with variable‐valence state in clay, the initial degradation temperature of the test sample (T₀), the degradation peak temperature (T_p1), and the final degradation temperature (T_f1) in first‐stage reaction, as well as the degradation peak temperature (T_p2) and the last final degradation temperature (T_f) in second‐stage reaction of all the test samples more or less shift to the direction of low temperature; besides, the activation energy (E) of the reaction of the test samples more or less decreases. This means that the metal components with variable‐valence state promote the oxidative degradation of the clay–rubber masterbatch. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3809–3815, 2006     

Thermooxidative degradation of methyl methacrylate‐graft‐natural rubber

The thermooxidative degradation of methyl methacrylate‐graft‐natural rubber (MG) at different heating rates (B) has been studied with thermogravimetric analysis in an air environment. The results indicate that the thermooxidative degradation of MG in air is a one‐step reaction. The degradation temperatures increase with B. The initial degradation temperature (T_o) is 0.697B + 350.7; the temperature at the maximum degradation rate, that is, the peak temperature on a differential thermogravimetry curve (T_p), is 0.755B + 368.8; and the final degradation temperature (T_f) is 1.016B + 497.4. The degradation rates at T_p and T_f are not affected by B, and their average values are 46.7 and 99.7%, respectively. The maximum thermooxidative degradation reaction rate, that is, the peak height on a differential thermogravimetry curve (R_p), increases with B. The relationship between B and R_p is R_p = 2.12B + 7.28. The thermooxidative degradation kinetic parameters are calculated with the Doyle model. The reaction energy (E) and frequency factor (A) change with an increasing reaction degree, and the variational trends of the two kinetic parameters are similar. The values of E and A increase remarkably during the initial stage of the reaction, then keep relevantly steady, and finally reach a peak during the last stage. The velocity constants of the thermooxidative degradation vary with the reaction degree and increase with the reaction temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1227–1232, 2003     

Pulsed NMR study on the silica-filled rubber systems

Proton spin–spin relaxation time has been measured by the pulsed NMR technique for the bound rubbers extracted from both silica-filled polyisoprene and polybutadiene composites. Two relaxation times T_2t (short) and T_2l (long) are observed for all samples. They are ascribed, respectively, to the relaxation of the tightly and loosely bound rubber components. When the silica filled polybutadiene composite is heat treated at 120°C, loosely bound rubber is preferentially formed, which leads to the increase in the total bound rubber fraction in the composite. During the heat treatment of silica-filled polyisoprene composite, a part of the loosely bound rubber phase is transformed into tightly one, and simultaneously the chain mobilities of both phases become more constrained state. These changes are accompanied by the degradation of polyisoprene molecules probably due to the strong chemical interaction of silanol group and rubber molecules. At a prolonged heat treatment, the fraction of total bound rubber in the composite decreases as a result of the degradation of the loosely bound rubber molecules.     

Comparison of thermoset soy protein resin toughening by natural rubber and epoxidized natural rubber

Fully bio‐based soy protein isolate (SPI) resins were toughened using natural rubber (NR) and epoxidized natural rubber (ENR). Resin compositions containing up to 30 wt % NR or ENR were prepared and characterized for their physical, chemical and mechanical properties. Crosslinking between SPI and ENR was confirmed using ¹H‐NMR and ATR‐FTIR. All SPI/NR resins exhibited two distinctive drops in their modulus at glass transition temperature (T_g ) and degradation temperature (T_d ) at around ?50 and 215 °C, corresponding to major segmental motions of NR and SPI, respectively. SPI/ENR resins showed similar T_g and T_d transitions at slightly higher temperatures. For SPI/ENR specimens the increase in ENR content from 0 to 30 wt % showed major increase in T_g from ?23 to 13 °C as a result of crosslinking between SPI and ENR. The increase in ENR content from 0 to 30 wt % increased the fracture toughness from 0.13 to 1.02 MPa with minimum loss of tensile properties. The results indicated that ENR was not only more effective in toughening SPI than NR but the tensile properties of SPI/ENR were also significantly higher than the corresponding compositions of SPI/NR. SPI/ENR green resin with higher toughness could be used as fully biodegradable thermoset resin in many applications including green composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44665.     

Chitosan and N‐carboxymethylchitosan: I. The role of N‐carboxymethylation of chitosan in the thermal stability and dynamic mechanical properties of its films

Chitosan (degree of deacetylation of 90.2%) and N‐carboxymethylchitosan (N‐CMCh) (degree of substitution of 18.5%) were analyzed using thermogravimetric analysis in order to determine their thermal stability. Also, their films were evaluated using scanning electron microscopy (SEM) and mechanical and dynamic mechanical analysis (DMA). Both polymers showed a thermal degradation peak at T_m ～ 250 °C, with T_onset and weight loss of 175 °C and 62% and 190 °C and 35% for chitosan and N‐CMCh, respectively. N‐CMCh showed a second thermal degradation peak at T_m = 600 °C, with an additional weight loss of 25%. Kinetic thermal analysis showed a slower process of degradation at 100 °C for N‐CMCh compared with chitosan, and an activation energy 13 times higher for the former, confirming the higher stability of N‐CMCh. Analysis of chitosan and N‐CMCh films showed that the latter support a high tension, with lower elasticity, and, as revealed by DMA, N‐CMCh has a more compact film structure, with a crossing arrangement of N‐CMCh fibers, as compared with the chitosan films which were determined from SEM analysis to have fibers in one direction only. Copyright © 2006 Society of Chemical Industry     

Investigation of thermal behavior of poly(2‐hydroxyethyl methacrylate‐co‐itaconic acid) networks

The thermal behavior of poly(2‐hydroxyethyl methacrylate) [PHEMA] homopolymer and poly(2‐hydroxyethyl methacrylate‐co‐itaconic acid) [P(HEMA/IA)] copolymeric networks synthesized using a radiation‐induced polymerization technique was investigated by differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The glass‐transition temperature (T_g) of the PHEMA homopolymer was found to be 87°C. On the other hand, the T_g of the P(HEMA/IA) networks increased from 88°C to 117°C with an increasing amount of IA in the network system. The thermal degradation reaction mechanism of the P(HEMA/IA) networks was determined to be different from the PHEMA homopolymer, as confirmed by thermogravimetric analysis. It was observed that the initial thermal degradation temperature of these copolymeric networks increased from 271°C to 300°C with IA content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1602–1607, 2007     

Toughening of thermoset green zein resin: A comparison between natural rubber-based additives and plasticizers

Zein-based brittle thermoset green resin was toughened using sorbitol, natural rubber fibers (NRF), and epoxidized natural rubber fibers (ENRF). NRF and ENRF were electrospun directly into zein slurry. Chemical, thermal, and mechanical properties of zein resin containing NRF (Zein/NRF) and ENRF (Zein/ENRF) were compared with those of sorbitol-plasticized zein. NRF was found to be immiscible in zein and Zein/NRF resins showed two distinct glass transition temperatures (T _g), whereas Zein/ENRF specimens showed significant increases in both T _g and degradation temperature (T _d) due to crosslinking between zein and epoxidized natural rubber. ENRF was more effective in enhancing fracture toughness of zein than NRF or sorbitol. Increased ENRF loading to 15 wt % showed significant increase in toughness with minimal decreases in strength and Young's modulus. Sorbitol and NRF were unable to improve the toughness of zein resin significantly. Environment-friendly zein/ENRF resin with higher fracture toughness developed in this study would be suitable in many applications including green composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48512.     

The degradation of guayule rubber and the effect of resin components on degradation at high temperature

Degradation of pure guayule rubber and rubber in the presence of stearic, oleic, linoleic, and linolenic acid, has been studied at high temperatures (from 150°C to 600°C) using thermogravimetric analysis (TGA). On-line mass spectrometric analysis of the products of decomposition has also been done to understand the mechanism of degradation. Degradation of rubber starts around 230°C in air and 330°C in nitrogen. Presence of acids changes the onset of degradation, because of low decomposition temperature of the acids. In the derivative curve, there is one T_max for degradation in nitrogen; two for rubber; and three for rubber containing acids are observed for degradation in air. The activation energy of degradation, as observed by isothermal kinetics, in the 1–10% weight loss region, is 225 kJ/mol in nitrogen and 167 kJ/mol in air. In the 10–100% region, however, the activation energy of degradation measured by the Freeman and Carroll method using dynamic thermogravimetry, is 239 kJ/mol in both nitrogen and air atmosphere. The main products of pyrolysis in inert atmosphere are propylene, propane, isobutylene, methyl butene, isoprene, 2,3-dimethyl cyclopentene, octene, 2,4-dimethylcyclohexene, dipentene, etc. Isoprene is found to be the most abundant. Fragments having m/e values of 136, 121, 107, 93, 79, and 53 are also produced in large quantities. The ratio of concentration of dipentene to isoprene increases marginally with temperature. The concentration of other fragments however increases drastically with temperature. The additives have no effect on the nature of products obtained. The conversion to different fragments depends upon the temperature of degradation and the stability of intermediate products. All smaller molecules are obtained from either dipentene or isoprene. A mechanism of formation of these products has been suggested.     

New fluorescent monomers and polymers displaying an intramolecular proton‐transfer mechanism in the electronically excited state. III. Thermogravimetric stability study of the benzazolylvinylene derivatives

Six fluorescent benzazolylvinylene derivatives were studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and related molecular parameters. The thermal stability was determined in terms of the steps of degradation and its fitting parameters, such as maximum degradation rate (R_max), maximum degradation rate temperature (T_Rmax), degradation temperature range, which is related to the half‐width at half‐height values (Γ), and the kinetic parameters: activation energy (E_a), pre‐exponential factor (A), and reaction order (n) obtained by Barrett's method. Different organic substitutes and heteroatoms do not play a fundamental role in the thermal behavior of the studied dyes. The compensation effect between pre‐exponential factor and activation energy was confirmed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 495–500, 2006     

Latex-assisted functionalized multi-walled carbon nanotube-reinforced elastomeric nanocomposites with enhanced mechanical performance

ABSTRACT

Functionalized multi-walled carbon nanotube (f-MWCNT)-reinforced elastomeric blend nanocomposites were developed through co-coagulation of natural rubber and poly (butadiene rubber) latex blends followed by efficient dispersion of f-MWCNT by using high-speed mechanical perturbation and probe ultrasonication. A systematic variation of f-MWCNT loading revealed superior mechanical properties up to certain loading level of nanofillers. Abrasion resistance was found to be affected by blend composition and nanofiller loading. The thermogravimetric analysis further revealed the thermal degradation behavior of the nanocomposites. Overall, our study has established the potential to develop high-performance elastomeric nanocomposites by using f-MWCNT, efficient dispersion technique, and appropriate process parameters.     

Cure Kinetics and Thermal Property of Bisphenol-S Epoxy Resin and Phthalic Anhydride

Abstract

The cure kinetics of bisphenol-S epoxy resin (BPSER) and curing agent phthalic anhydride, with N,N-dimethyl phenzylamine as an accelerator, were studied by means of differential scanning calorimetry (DSC). Analysis of DSC data indicated that an autocatalytic behavior showed in the first stages of the cure. The autocatalytic behavior was well described by the model proposed by Kamal including two rate constants, k1 and k2, and two reaction orders, m and n. The overall reaction order, m + n, is in the range 2～3. The activation energies for k1 and k2 were 111.69 and 80.47 KJ/mol, respectively. Diffusion control was incorporated to describe the cure in the latter stages. The glass transition temperatures (T_gS) of the BPSER/anhydride samples isothermally cured partially were determined by means of torsional braid analysis (TBA). and the results showed that the reaction rate increased with increasing T_g in terms of the rate constant, but decreased with increasing conversion. The T_g of completely cured BPSER/anhydride system is about 40 K higher than that of BPAER. The thermal degradation kinetics of this system was investigated by thermogravimetric analysis (TGA). It illustrated that the thermal degradation of the BPSER/phthalic anhydride has n-order reaction kinetics.     

Surface functionalization of polypropylene‐bearing isocyanate groups in solid state and their cyclotrimerization with diisocyanates

Solid‐state graft polymerization of 3‐isopropenyl‐α,α′‐dimethylbenzene isocyanate (TMI) onto the surface of polypropylene beads was carried out in a triethylborane/oxygen redox system. Chemical structures were characterized using attenuated total reflectance–Fourier transform infrared spectroscopy. Results showed that TMI was successfully grafted because of the appearance of an ? NCO absorption peak at 2255 cm^?1. The emergence of oxygen and nitrogen elements detected by EDS and XPS also demonstrated the existence of isocyanate group on PP‐grafted. The grafting ratio of TMI to polypropylene was examined using 9‐(methylamino‐methyl)anthracene (MAMA) as an intermediate substance. The fluorescent property of MAMA before and after reaction was characterized to guarantee interaction between MAMA and isocyanate. Thermal properties were examined using differential scanning calorimetry–thermogravimetric analysis. Results indicated that melting temperature (T_m) of pure PP was 168^oC, while the PP‐grafted decreased to 164^oC. Meanwhile, decomposition temperature (T_d) decreased with increased grafting ratio for about 8 to 15^oC; however, when styrene was introduced, T_m increased probably because of the stabilizing effect on macromolecular radicals and the suppression effect on chain degradation. Besides, the cyclotrimerization of isocyanates on the grafted polymer chain was further conducted to prepare thermally stable isocyanurate composite materials, remedying the T_d loss of PP‐g‐TMI by improving for 10^oC appropriately. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42186.     

Novel HDPE/ground tyre rubber composite materials obtained through in‐situ polymerization and polymerization filling technique

Novel hybrid materials composed by a high density polyethylene (HDPE) matrix and powdered rubber coming from scrap tyres (ground tyre rubber [GTR]) were prepared. Two methods were followed: ethylene was polymerized by a metallocene catalyst (Cp₂ZrCl₂/methylaluminoxane) in the presence of a toluene dispersion of the filler (in‐situ polymerization); and the ethylene was polymerized out after supporting the aluminum‐based co‐catalyst onto the rubber particles surface (polymerization filling technique). The experimental conditions were varied in order to achieve the best catalyst productivity. All the synthesized composites were characterized in order to investigate the occurrence and the extent of interactions between HDPE macromolecular chains and the GTR components and their effects onto the final properties, by comparison with a composite where GTR was included into the matrix through blending in the melt. Scanning electron microscopy, atomic force microscopy, and solvent extractions were performed to this aim. The amount of thermoplastic matrix bonded to the filler was determined, and the extracted polymer was characterized by size exclusion chromatography and differential scanning calorimetry. Finally, stress–strain behavior of the composites obtained, respectively, by catalytic polymerization and melt mixing was compared. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40313.     

Synthesis of polyundecamethylene 2,6‐naphthalamide as semiaromatic polyamide‐containing naphthalene ring

A novel engineering plastic polyundecamethylene 2,6‐naphthalamide (PA11N) was prepared via a reaction of 2,6‐naphthalene dicarboxylic acid and 1,11‐undecanediamine through a three‐step procedure. The structure of synthesized PA11N was characterized by elemental analysis, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance (¹H‐NMR). The thermal behaviors were determined by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The solubility, water‐absorbing capacity, and mechanical properties of PA11N have also been investigated. Melting temperature (T_m), glass transition temperature (T_g), and decomposition temperature (T_d) of PA11N are 294, 139, and 493°C, respectively. The results show that the heat resistance and mechanical properties of PA11N are near to those of polynonamethylene terephthalamide, and PA11N is a promising heat‐resistant and processable engineering plastic. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010