Preparation of high‐performance damping materials based on carboxylated nitrile rubber: Combination of organic hybridization and fiber reinforcement

The dynamic mechanical properties denoted by storage modulus (E′) and loss factor (tan δ) of binary and ternary systems consisting of carboxylated nitrile rubber (XNBR) filled with organic hindered phenol compound 2,2′‐methylenebis(6‐tert‐butyl‐4‐methylphenol) (AO‐2246) or/and short carbon fiber (SCF) were investigated. DMA results of binary XNBR/AO‐2246 system showed that by addition of AO‐2246, the tan δ peak maximum of XNBR was remarkably increased up to 3.5, and its peak position was also significantly shifted to room temperature, demonstrating that XNBR/AO‐2246 composite is a promising damping material. Nevertheless, application of such XNBR/AO‐2246 composite is limited due to its relatively low E′ value above glass transition temperature. Therefore, to develop a high‐performance damping material with high tan δ peak and high modulus as well as controllable tan δ peak position, the combination of organic hybridization and fiber reinforcement were adopted. DMA analysis of various ternary XNBR/AO‐2246/SCF systems revealed that by introduction of SCF, the E′ value of XNBR/AO‐2246 was increased remarkably while the tan δ peak maximum was still higher than 2.5. Thus, a new type of XNBR‐based high‐performance damping material was developed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

New thermoplastic vulcanizate,composed of polypropylene and ethylene–vinyl acetate copolymer crosslinked by tetrapropoxysilane: evolution of the blend morphology with respect to the crosslinking reaction conversion

A thermoplastic vulcanizate (TPV) is tailored by a dynamic vulcanization process. TPVs can be processed as thermoplastics and have properties similar to conventional vulcanized rubbers. The main objective of our recent works was to tailor, by using the reactive extrusion process, a new TPV composed of polypropylene homopolymer (PP) as thermoplastic phase and ethylene–vinyl acetate copolymer (EVA) as elastomer phase, which is crosslinked by tetrapropoxysilane (TPOS) as crosslinking agent in the presence of dibutyl tin oxide (DBTO) as catalyst. Crosslinking is carried out through a transesterification reaction between the ester groups of EVA and the alkoxysilane groups of TPOS. This exchange reaction is catalyzed by DBTO at temperatures above 100 °C. The main advantage of this chemistry that it is non‐radical, and so prevent the degradation of PP, in comparison with crosslinking reactions using peroxides as initiators. Different reactive blends were prepared in the internal mixer of a Haake Plasticorder. In order to know how the crosslinking reaction has advanced, the EVA gel content and the volume swelling rate of the blend were measured. The aim of this study was to get a better understanding of the dispersion mechanism of EVA in the major phase during its dynamic vulcanization in the presence of PP in the minor phase. This paper deals with the correlation that exists between the evolution of the two‐phase blend morphology and the extent of the crosslinking reaction on the elastomer phase during the elaboration of a TPV. In particular, we showed that the correlation was almost the same for the elaboration of the TPV in the internal mixer of the Haake Plasticorder (discontinuous process) and in a twin‐screw extruder (continuous process). Copyright © 2004 Society of Chemical Industry     

Preparation and performance of high‐impact polystyrene (HIPS)/nano‐TiO2 nanocomposites

High‐impact polystyrene (HIPS)/nano‐TiO₂ nanocomposites were prepared by surface pretreatment of nano‐TiO₂ with special structure dispersing agent (TAS) and master batch manufacturing technology. The results show that when the nano‐TiO₂ content is 2%, the notched impact strength, tensile strength, and elastic modulus of HIPS/nano‐TiO₂ nanocomposites increased to a maximum. This result indicates that nano‐TiO₂ has both toughening and reinforcing effects on HIPS. The heat‐deflection temperature and flame‐retardance of HIPS/nano‐TiO₂ nanocomposites are also obviously improved as the nano‐TiO₂ content is increased. The nanocomposites manufactured by the two‐step method have better mechanical properties than that made by a one‐step method. HIPS/nano‐TiO₂ nanocomposites are also non‐Newtonian and pseudoplastic fluids. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 381–385, 2003     

Kinetic of epoxy resin formation by high‐performance liquid chromatography

This article is focused on the following of the cure of an epoxy resin by high‐performance liquid chromatography (HPLC) and the comparison of the data obtained with those obtained by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques usually employed for characterize curing processes. A reversed‐phase HPLC method with UV detection is developed to study the kinetic of the curing reaction of diglycidyl ether of bisphenol A (DGEBA) with 1,3‐cyclohexanebismethylamine (1,3‐BAC) at 60, 70, and 80°C, before and after gelation. The limits of quantification obtained permit the application of the proposed method until the last steps of the formation kinetic. HPLC and DSC analysis show a good correlation. The gel conversions obtained by HPLC and DMA agree well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 497–504, 2003     

Fine‐structure and physical properties of polyethylene fibers in high‐speed spinning. I. Effect of melt‐flow rate in the high‐density polyethylene

High‐density polyethylene (HDPE) fibers, obtained from a melt‐flow rate (g/10 min) of 11 and 28, was produced by a high‐speed melt‐spinning method in the range of take‐up velocity from 1 to 8 km/min and from 1 to 6 km/min, respectively. The change of fiber structure and physical properties with increasing take‐up velocity was investigated through birefringence, wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), a Rheovibron, and a Fafegraph‐M. With an increase in take‐up velocity, the birefringence showed a sigmoidal increase, which has distinct changes in the range of 1–5 km/min. Throughout the whole take‐up velocities, the birefringence of HDPE(11) was higher than that of HDPE(28). With increasing take‐up velocity, the crystalline orientation was transformed from a‐axis orientation to c‐axis orientation. These crystalline relaxations are confirmed by the tan δ peak of high‐speed spun HDPE fibers. The intensity of the crystalline relaxation peak decreases with increasing take‐up velocity in both HDPE(11) and HDPE(28). As above, the crystalline relaxation peaks shift to lower temperature with increasing take‐up velocity. With increasing take‐up velocity, the ultimate strain decreases while both specific stress and the initial modulus increase. The mechanical behavior may be closely related to, as investigated by birefringence, orientation of the amorphous region, etc., the take‐up velocity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1182–1195, 2000     

Influences of the grafting percentage of natural rubber‐graft‐poly(2‐hydroxyethyl acrylate) on properties of its vulcanizates

The graft copolymerization of 2‐hydroxyethyl acrylate (HEA) monomer onto natural rubber (NR) latex was successful using cumene hydroperoxide and tetraethylene pentamine as redox initiators. The grafting of poly(2‐hydroxyethyl acrylate) (PHEA) on the NR particles was confirmed by Fourier transform infrared spectroscopy, ¹H NMR spectroscopy and TEM. The NR‐g‐PHEA with various grafting percentages (0%, 8.7%, 14.3% and 18.7%) was compounded on a two‐roll mill with a sulfur vulcanization system. The effects of grafting percentage on the cure characteristics, dielectric properties, thermal properties and physical properties of NR‐g‐PHEA vulcanizates were investigated. It was found that increased grafting caused NR‐g‐PHEA vulcanizates to have reduced water contact angle, scorch time and cure time, while the dielectric constant and dissipation factor increased. The NR‐g‐PHEA vulcanizate with 8.7% grafting exhibited the highest delta torque (M_H ? M_L), crosslink density, tensile strength, moduli at 100%, 200% and 300% strains, and hardness, with insignificant loss of elongation at break in comparison to the other cases. © 2018 Society of Chemical Industry     

Effects of hygrothermally decomposed polyurethane on the curing and mechanical properties of carbon black‐filled epoxidized natural rubber vulcanizates

Hygrothermally decomposed polyurethane (HD‐PUR) was mixed up to 20 phr in epoxidized natural rubber (with 50 mol % epoxidation; ENR50) recipes, and the curing and mechanical behaviors were studied. Mechanical testing of the ENR50/HD‐PUR vulcanizates determined the tensile, tear, compression‐set, hardness, abrasion, hysteresis, and resilience properties. No significant changes were observed in the tensile properties with the incorporation of HD‐PUR. The ENR50 compounds showed an increase in compression set with increasing HD‐PUR content. Rubbers cured by a semi‐efficient vulcanization system gave the best overall performance. A further improvement in curing and mechanical properties was achieved by the carbon black grade N330 being replaced with a more active grade (N375). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2265–2276, 2002     

Effect of fillers and plasticizers on the performance of novel heat and oil‐resistant thermoplastic elastomers from nylon‐6 and acrylate rubber blends

The effects of various fillers (SRF black, silica, and clay) and plasticizers (dibutyl phthalate and dioctyl phthalate) on the mechanical, dynamic mechanical, and rheological properties and on the heat and oil resistance of the thermoplastic elastomeric reactive blends of nylon‐6 and acrylate rubber (ACM) were investigated. The mixing torque behavior of the blends in Brabender Plasticorder shows reduced extent of interaction between the two component polymers in the presence of both fillers and plasticizers. Silica‐filled blends show the highest viscosity increment due to the possibility of reaction between its surface silanol groups and the reactive epoxy groups present in the ACM chain during melt‐blending operation. Though the addition of fillers reduces the processability of the blends, it improves the extensibility as well as the tension set properties of the blends. The mechanical integrity and the damping characteristics of the blends are also improved with the addition of fillers; the latter is evidenced from the dynamic mechanical thermal analysis of the blends. The tensile strength and hardness of the filled blends remain practically unchanged after ageing at 175°C for 72 h and, also, the oil swell does not change appreciably with the addition of fillers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1490–1501, 1999     

Studies on damping properties of P(MMA‐AN)/P(EA‐nBA) LIPNs

Using a two‐stage emulsion polymerization method, a series of poly(methyl methacrylate‐acrylonitrile)/poly(ethyl acrylate‐n‐butyl acrylate) [P(MMA‐AN)/P(EA‐nBA)] latex interpenetrating polymer networks (LIPNs) were synthesized by varying AN content, ratio of network I/network II, crosslinker content, and introducing chain transfer agent. The damping properties of the LIPNs were investigated using a Rheovibron Viscoelastometer. The results indicates that a suitable content of AN can improve the damping properties of the LIPNs. Three kinds of fillers were incorporated into the LPINs, respectively, to measure the change in the damping properties. Mica and TiO₂ both increased the damping properties of the LIPNs over the wide temperature range. For TiO₂‐filled LIPNs, it was observed that the tan δ values exceeded 0.4 over 112.6°C temperature range from −50 to 72.6°C. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 722–727, 2000     

Synthesis and characteristics of thermoplastic elastomer based on polyamide‐6

A new class of polyether amide thermoplastic elastomers (TPAE) was synthesized via a three‐step polymerization route. In the first step a binary carboxyl terminated polyamide‐6 (PA6) with relatively low number‐average molecular weight was prepared via a caprolactam hydrolytic ring‐opening process. 4,4′‐Diphenylmethane diisocyanate (MDI) was reacted with the PA6 to produce PA6–MDI hard segments in the second step. Chain extension of the hard segments with poly(tetramethylene glycol) was the last step to furnish a series of new TPAEs. Structural characterization, physical properties and the effects of reaction conditions on the properties of the copolymer were investigated by infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy and other analytical techniques. Possible side reactions and phase separation are reported. Copyright © 2011 Society of Chemical Industry     

A modeling and experimental study of the influence of twist on the mechanical properties of high‐performance fiber yarns

Little data exist on how twist changes the properties of high‐performance continuous fiber yarns. For this reason, a study was conducted to determine the influence of twist on the strength and stiffness of a variety of high‐performance continuous polymeric fiber yarns. The materials investigated include Kevlar 29®, Kevlar 49®, Kevlar 149®, Vectran HS®, Spectra 900®, and Technora®. Mechanical property tests demonstrated that the initial modulus of a yarn monotonically decreases with increasing twist. A model based on composite theory was developed to elucidate the decrease in the modulus as a function of both the degree of twist and the elastic constants of the fibers. The modulus values predicted by the model have good agreement with those measured by experiment. The radial shear modulus of the fiber, which is difficult to measure, can be derived from the regression parameter of experimental data by the use of the model. Such information should be useful for some specialized applications of fibers, for example, fiber‐reinforced composites. The experimental results show that the strength of these yarns can be improved by a slight twist. A high degree of twist damages the fibers and reduces the tensile strength of the yarn. The elongation to break of the yarns monotonically increases with the degree of twist. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1938–1949, 2000     

Mechanical and dynamic mechanical thermal properties of heat‐ and oil‐resistant thermoplastic elastomeric blends of poly(butylene terephthalate) and acrylate rubber

Poly(butylene terephthalate) (PBT) and acrylate rubber (ACM) were melt‐blended in a Brabender Plasticorder at 220°C and 40 rpm rotor speed. The blends were dynamically vulcanized by the addition of hexamethylenediamine carbamate (HMDC) during the melt‐blending operation in the Brabender. Dynamic mechanical thermal analysis (DMTA) of the blends suggests a two‐phase morphology of the blends with two separate T_g 's for both components. The blends were also compatibilized by the addition of a dibutyl tin dilaurate (DBTDL) catalyst, which enhanced the extent of the transesterification reaction between the two polymers. The transreaction results in softer blends with higher elongation properties. The above blends also show very good oil and heat resistance at elevated temperatures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1001–1008, 2000     

Use of gradient,critical, and two‐dimensional chromatography in the analysis of styrene‐ and methyl methacrylate‐grafted epoxidized natural rubber

The growing number of heterogeneous polymeric species that are being synthesized places increasing demands on existing analytical techniques. Although size‐exclusion chromatography (SEC) has established itself as a powerful analytical tool, it has its limits when complex polymers, e.g., graft copolymers, must be analyzed. In this case, complementary techniques such as gradient HPLC and liquid chromatography at critical conditions (LCCC) are more favorable. The present study describes the synthesis and analysis of methyl methacrylate‐ and styrene‐grafted epoxidized natural rubber by different chromatographic techniques. The grafting efficiency was evaluated by gradient HPLC under normal and reversed phase conditions. Methyl methacrylate‐grafted ENR50 was further analyzed by LCCC, where separation of the rubber and grafted rubber occurred according to chemical composition but was independent of the molar mass of the methyl methacrylate homopolymers. This was followed by the combination of LCCC and SEC, where separation was achieved in two dimensions. Relevant deductions were made of both the chemical composition distribution and the molar mass distribution of the functional groups of methyl methacrylate‐grafted ENR50. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2530–2538, 2003     

The influence of aggregate type on the physical and mechanical properties of high‐performance concrete subjected to high temperature

This paper presents the results of an experimental study on the behaviour of high‐performance concretes after high temperature exposure. The high temperature exposure is related to the potential risk of fire, and mechanical properties analysis is needed afterwards to assess the residual strength of the material. The results presented in the paper show the properties evolution of four concretes made with four different aggregate types: basalt, granite, dolomite and riverbed gravel. The mix compositions allow comparisons, because the cement paste and mortar compositions and their volumes remain the same for all the four concretes. Moreover, the aggregate particle size distribution was chosen to be quasi identical so that this factor does not affect the concrete behaviour. The decrease of tensile strength value with the increase of temperature is more pronounced than compressive strength reduction thus, the exponential and power function equations were proposed to describe f_tT–f_cT relationship. The change of modulus of elasticity in relative values is similar, although the initial values of modulus are different and correspond to the aggregate type. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of components (acrynitril and acrylate acid) on damping properties of poly(styrene‐acrynitril)/poly(ethylacetate‐n‐butylacrylate) latex interpenetrating polymer networks

A series of poly(styrene‐acrynitril)/poly(ethylacetate‐n‐butylacrylate) latex interpenetrating polymer networks (LIPNs) have been synthesized by varying the content of AN and the distribution of acrylate acid. The damping temperature range of the LIPNs was broadened and the damping value increased distinctly when the content of acrynitril was 10%. In low or high temperature range, the damping value of the LIPNs would have a different level of increase with the different distribution of AA in both the networks. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 821–826, 2002; DOI 10.1002/app.10350     

New optically active poly(amide–imide–urethane) thermoplastic elastomers derived from poly(ethylene glycol diols), 4,4′‐methylene‐bis(4‐phenylisocyanate), and a diacid based on an amino acid by a two‐step method under microwave irradiation

A new class of optically active poly(amide–imide–urethane)s (PAIUs) was synthesized via a two‐step diisocyanate route under microwave irradiation. In these reactions, 4,4′‐methylene‐bis(4‐phenylisocyanate) was reacted with bis(p‐amido benzoic acid)‐N‐trimellitylimido‐L ‐leucine and poly(ethylene glycol diol)s (PEGs), such as PEG‐400, PEG‐600, PEG‐1000, and PEG‐2000, to furnish a series of new PAIUs. The effects of different reaction conditions, such as the method of preparation (polyol or acid chain extension), the prepolymerization step (NCO‐terminated oligoamide or NCO‐terminated polyether polyol), the irradiation time and power, the reaction solvent, the soft‐segment length, and the presence or absence of reaction catalysts (e.g., triethylamine, pyridine, and dibutyltin dilaurate), on the properties of the copolymers, including the solubility, viscosity, and thermal behavior, were investigated. The resulting multiblock copolymers had inherent viscosities of 0.15–0.53 dL/g. These multiblock copolymers were optically active, thermally stable, and soluble in amide‐type solvents. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1781–1792, 2005     

Mechanical properties and structure of high‐density polyethylene samples prepared by injection molding with low‐frequency vibration

To better understand the formation of different crystal structures and improve the mechanical properties of high‐density polyethylene samples, melt vibration technology, which generally includes shear vibration and hydrostatic pressure vibration, was used to prepare injection samples. Through melt vibration, the crystal structure changed from typical spherulites of the traditional injection sample to obviously orientated lamellae of vibration samples. Sizes and orientation degrees of lamellae were different according to different vibration conditions. Crystallinity degrees of vibration samples increased notably. Therefore, the tensile strength of vibration samples increased with increasing vibration frequency and vibration pressure, whereas elongation of vibration samples decreased during the first stage and then continued to increase as the vibration frequency increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 818–823, 2005     

Dynamic mechanical properties in blends of poly(styrene‐b‐isoprene‐b‐styrene) with aromatic hydrocarbon resin

The damping properties in blends of poly(styrene‐b‐isoprene‐b‐styrene) (SIS) and hydrogenated aromatic hydrocarbon (C₉) resin were investigated by dynamic mechanical analysis. SIS exhibited two independent peaks of loss factor (tan δ) corresponding to the glass transition of polyisoprene (PI) and polystyrene (PS) segments, respectively. The addition of hydrogenated C₉ resin had a positive impact on the damping of SIS. With the increasing softening point and content of the resin, the main tan δ peak shifted to higher temperatures and the useful damping temperature range was broadened. Addition of mica or PS was found to widen the effective damping range evidently in the high‐temperature region, especially when PS was mixed in the solid state. It was concluded that the dispersed PS domains played a role of reinforcing fillers at low temperatures and served as a polymer component with a tan δ peak due to its glass transition at the high temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4157–4164, 2006     

New film‐forming aromatic poly(amide‐imide)s containing isoindoloquinazolinedione unit in the backbone. 2. Physical properties of the film cast from poly(biphenylphthalicdianhydride‐oxydianiline‐4,4′‐diamino‐3′‐carbamoyl‐benzanilide) [poly(BPDA‐ODA‐DACB)]

New aromatic poly(amide‐imide) films containing isoindoloquinazolinedione unit in the backbone chain were directly obtained by thermal cyclization of the prepolymer of poly(amic acid‐carbonamide) type, i.e., poly(biphenylphthalic dianhydride‐oxydianiline‐4,4′‐diamino‐3′‐carbamoyl‐benzanilide) [poly(BPDA‐ODA‐DACB)]. The films, before heat treatment, exhibited the tensile strength of 30 ≈ 40 MPa and the tensile modulus of 1.3 ≈ 1.9 GPa. After heat treatment, the strength and modulus increased to 135 ≈ 150 MPa and 2.6 ≈ 2.7 GPa, respectively. The films remained transparent throughout the thermal treatment. The cyclized films were much more chemically resistant to alkali than the commercial products such as “Kapton” film and “P84” film, while thermal properties were comparable. The isoindoloquinazolinedione unit induced in the chain backbone on the heat treatment of the films was considered to be a major factor responsible for the superior physical properties of the films. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 118–123, 2000     

New manganese catalyzed regiocontrolled synthesis of poly(2,5‐dialkyl‐1,4‐phenylene oxide)s

A new catalyst system is developed for regiocontrolled synthesis of poly(2,5‐dialkyl‐1,4‐phenylene oxide)s by oxidative coupling polymerization of 2,5‐dialkylphenol. The treatment of the α‐benzoin oxime with manganese chloride in methanol under basic condition led to the formation of manganese benziloxime complex in which α‐benzoin oxime was converted to benziloxime and coordinated to manganese as bidentate ligands. The polymerizations were conducted in toluene using manganese benziloxime complex and dibutylamine in a continuous flow of oxygen, and the structures, properties of the catalyst, and polymers were studied by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). The catalyst showed high regioselectivity and reasonably good yields to afford the poly(2,5‐dimethyl‐1,4‐phenylene oxide)s with 1,4‐C‐O linkage structure which possessed melting point higher than the poly(p‐phenylene sulfide) or type II liquid crystalline polymer. The regioselectivity was enhanced when employing molecular sieves‐supported manganese catalyst system at 90°C and the crystallinity of poly(2,5‐dimethyl‐1,4‐phenylene oxide)s was estimated by wide‐angle X‐ray scattering (WAXS) and DSC. The crystallinity was calculated about 23.7% and a heat‐reversible melting and crystallization behavior occurred at 327.8 and 306.8°C, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009