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     

Morphological evolution and property changes of acrylate rubber/polyacetal thermoplastic vulcanizates during dynamic vulcanization process

A new type of thermoplastic vulcanizates (TPV) that is resistant to hot oil, high temperature, and aging was prepared using acrylate elastomer (ACM) and polyoxymethylene (POM) as raw materials. The phase transition process and micromorphology development of the blends with the change of dynamic vulcanization (DV) time, and to illustrate the effects of the phase transition and the degree of elastomer phase crosslinking on the macroscopic properties of TPV were investigated. It was shown that ACM crosslinking occurs continuously during 0–8 min of DV, whereas the phase inversion process occurs predominantly during 0–3 min. In contrast, the cross-section of the blends after phase inversion is flat, The constant elongation stress under small deformation, hardness, and permanent deformation after break are reduced, and the elongation at break, nonrelaxable modulus, and aging resistance are improved. The increase in the degree of vulcanization of the ACM phase resulted in a significant increase in the modulus of the blends under large deformation, an increase in the nonrelaxable modulus and relaxable modulus, an increase in the aging resistance, and a decrease in the elongation at tear were observed.     

炭黑品种对ACM/ECO并用胶性能的影响

研究炭黑品种对ACM/氯醚橡胶(ECO)并用胶硫化特性、物理性能、耐热老化性能、耐油性能和动态力学性能的影响.结果表明;炭黑品种对ACM/ECO并用胶的焦烧时间和正硫化时间影响不大;随着炭黑粒径的增大、结构度降低,ACM/ECO并用胶的拉伸强度、拉断伸长率、撕裂强度、压缩永久变形和耐油性能均有不同程度的下降;炭黑粒径对ACM/ECO并用胶的耐热老化性能和玻璃化温度影响不大,炭黑粒径大的并用胶tanδ值较大.     

EFFECT OF FIBER REINFORCEMENT ON THERMAL STABILITY AND SWELLING BEHAVIOR OF CR/NBR BLENDS

The effect of type, length, and denier of fibers on the thermal stability and swelling behavior of chloroprene/butadiene–acrylonitrile rubbers (CR/NBR) composites was investigated. The results reveal that Nylon 6 fibers improved mechanical properties, thermal stability, and swelling resistance in toluene of 50/50 CR/NBR blends. Of all fiber types investigated, the viscose fiber CR/NBR composite has the best swelling resistance in motor oil, whereas the polyester (PET) fiber composite has the best swelling resistance in brake fluid. The effect of Nylon 6 fiber loading up to 30 phr was tested in terms of mechanical properties of the composites and swelling in toluene and oils. Also, the reinforcement of white-filled blends were examined. Nylon 6 fiber loadings (15–30 phr) showed promising results, and the white-filled Nylon 6 composites showed a significant reinforcement with regard to mechanical properties and thermal stability.     

Polypropylene/natural rubber thermoplastic elastomer: Effect of phenolic resin as a vulcanizing agent on mechanical properties and morphology

The aim of this study is to characterize thermoplastic elastomers (TPEs) from polypropylene and natural rubber with and without phenolic resin as a vulcanizing agent. The blends containing 40–60 wt % of polypropylene were mixed in an internal mixer and pressed with a compression molding machine. TPEs without rubber vulcanization, named as unvulcanized thermoplastic natural rubber (uTPNR) were compared to TPEs containing dynamic vulcanized rubber, referred as vulcanized thermoplastic natural rubber (vTPNR). The uTPNRs illustrated cocontinuous phase morphology, whereas the vTPNRs displayed dispersed phase of vulcanized natural rubber. Tensile properties, tear strength, thermal ageing resistance, ozone resistance, tension set, hardness and swelling test in toluene, IRM 903 oil and engine oil were carried out according to ASTM. It was found that tensile and tear strength, hardness and tension set of the uTPNRs increased with increasing polypropylene content. Dynamic vulcanization improved tensile strength, elongation at break, tension set and degree of swelling of the TPEs, whereas hardness and tear strength did not show significant change after dynamic vulcanization. The vTPNRs exhibited higher ozone resistance and swelling resistance than the uTPNRs. Reprocessability of the vTPNRs was investigated and showed that tensile strength decreased at 20 and 30% and elongation at break decreased at 13 and 27% for the first and the third reprocessing respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ternary blends of acrylic rubber,poly(butylene terephthalate), and liquid crystalline polymer: Influence of interactions on thermal and dynamic mechanical properties

The ternary blends of acrylate rubber (ACM), poly(butylene terephthalate) (PBT), and liquid crystalline polymer (LCP) were prepared by varying the amount of LCP but fixing the ratio of ACM and PBT, using melt mixing procedure. The influence of interactions on thermal and dynamic mechanical properties of the blends was investigated over the complete composition range. The techniques applied were Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry (TG), and dynamic mechanical analysis (DMA). The FTIR spectroscopy analysis showed reduction in the intensity of the peak corresponding to epoxy groups of ACM with increasing heating time at 290°C. This implies that there is a chemical reaction between the epoxy and end groups of PBT and LCP. Glass transition temperature (T_g) and melting temperature (T_m) of the blends were affected depending on the LCP weight percent in the ACM/PBT blend, respectively. This further suggests the strong interfacial interactions between the blend components. In presence of ACM, the nucleating effect of LCP was more pronounced for the PBT phase. The thermogravimetric study showed improved thermal stability for the blends with the increasing LCP content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3904–3912, 2006     

Distribution of carbon black in natural rubber/acrylic rubber blends

Distributions of carbon black in 30/70% (w/w) natural rubber (NR)/acrylic rubber (ACM) blends were investigated as a function of the carbon black content and type using a dynamic mechanical thermal analysis (DMTA) technique. Two different types of carbon black (N220 and N330) were used, and 10–50 phr carbon black was compounded to the rubber blends. From the DMTA thermograms of various blends, the weight fractions of carbon black in the NR and ACM phases were calculated. Carbon black was unevenly distributed in the rubber blend. It preferred to migrate into the NR phase, regardless of the amount of carbon black that was used. By increasing the carbon black content, the weight fraction of carbon black in the NR phase decreased whereas that in the ACM phase increased. A change in the type of carbon black from N220 to N330 significantly decreased the weight fraction of carbon black in the NR phase, but it was not sufficiently strong to affect the tensile properties and hardness of the rubber blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:248–256, 2006     

Phase behavior study of chitosan/polyamide blends

Blends of chitosan with strongly crystalline polyamides (nylon-4 and nylon-6) and weakly crystalline polyamides (caprolactam/laurolactam and Zytel®) were investigated. Phase behavior, morphology, interactions with water, mechanical properties, and catalytic reactivity were studied. Films were made from formic acid solutions with the chitosan concentrations ranging from 5% to 95% (w/w). The 80% deacetylated chitosan is in the salt, neutral, or copper chelate form. All the blends have higher relative water contents than does the pure chitosan. Dry neutral chitosan shows a relaxation centered at approximately 90°C which is attributed to local motion. The phase behavior of the blends is influenced by preparation conditions such as the drying temperature. Characterization of blends by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) suggests partial miscibility of chitosan with nylon-4 and lack of miscibility in the remaining cases. Blending with nylon-4 enhances mechanical properties with marked antiplasticization in blends containing 90% chitosan. Catalytic activity of the chitosan is enhanced by blending with nylon-4. Salt and neutral forms of chitosan appear to be equally effective. © 1996 John Wiley & Sons, Inc.     

Swelling of porous ethylvinylbenzene–divinylbenzene copolymers and the stability of the pore structure

A series of porous ethylvinylbenzene–divinylbenzene (EVB–DVB) copolymers with DVB contents ranging from 22.0 to 98.4% were prepared using various amounts of toluene as the inert diluent, and studies were made on the copolymers as to their swelling properties, the stability of their pore structure, and the relationship between swelling in nonsolvents and variations in their pore structure. The swelling experiments showed that the ethanol regains of the copolymers were closely related to the course of phase separation, and the increases in both the DVB content and the volume fraction of monomers in the organic phase resulted in enhanced capacity of the highly crosslinked copolymers to keep swelling in solvents having extremely small affinity for these copolymers. The variations in pore structure, sometimes quite considerable, for copolymers pretreated with different solvents were observed even at DVB content up to 98.4% and further studies showed that a consistent relationship existed between pore volume variation and volume swelling ratio in ethanol for toluene modified copolymers.     

Ternary nylon-6/rubber/modified rubber blends: Effect of the mixing procedure on morphology, mechanical and impact properties

Ternary polyamide-based blends have been prepared by adding to nylon-6 (PA6) an ethylene-propylene random copolymer (EPM) and the same EPM functionalized by inserting onto its backbone maleic anhydride groups (EPM-g-SA). Two kinds of processing have been used: (a) one-step mixing in which the three components were simultaneously introduced in the mixer; (b) two-step mixing in which the two rubbers EPM and EPM-g-SA were separately premixed before the final mixing with PA6. Also binary PA6/EPM-g-SA blends have been prepared to compare their properties with those of the ternary one.

Mechanical tensile characterization at room temperature and impact Izod tests at different temperatures as well as a morphological analysis of smoothed samples have been performed on all the blends. It has been shown by a model reaction that both in binary and ternary blends an EPM-g-PA6 graft copolymer is formed, which acts as an interfacial agent between the rubbery dispersed phase and the polyamide matrix. The blends obtained by the one-step mixing showed a gross morphology and a very poor impact resistance, whereas the ones prepared by the two-step mixing exhibited very fine morphologies and excellent impact performances. In addition, as shown at least in the case of one ternary blend, there seems to be good morphological stability of these materials after a second processing. This has been attributed to the influence of the interfacial agent formed during the melt mixing of the two premixed rubbers with PA6.     

Transport of organic solvents through coir-fiber-reinforced natural rubber composites: a method for evaluating interfacial interaction

Use is made of the transport of organic solvents such as benzene, toluene and xylene to understand the interfacial interaction in cross-linked coir-fiber-reinforced natural rubber composites. Attempts were made to analyze the interfacial bonding in the composites containing coir fibers subjected to different chemical treatments. Based on experiments, a probable mechanism of transport is suggested. The diffusion coefficient and solubility in the rubber compound–solvent system have been evaluated. The swelling of composites containing untreated and NaOH-treated coir increased initially with fiber loading, but decreased at higher levels of fiber loading. But the swelling of composites which contained coir fiber treated with solutions of NaOH, toluene diisocyanate and natural rubber decreased gradually with fiber loading. It was also found that the swelling of this composite was the least. This is due to the high interfacial interaction between the fiber and the matrix which resists the uptake of organic solvents. It was seen that silica was not a necessary constituent of the bonding system for coir fiber reinforced natural rubber composites.     

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     

Preparation of N-methylol nylon-6 membranes for pervaporation of ethanol-water mixtures

N-methylol nylon 6 membranes were prepared by reacting nylon-6 with formaldehyde. Elemental analysis, used to analyze the composition of modified membranes, showed that the degree of substitution increased with formaldehyde content in the reaction solution. The modified nylon-6 membranes exhibited a high affinity to ethanol. Pervaporation results for the separation of ethanol-water mixtures showed that these membranes were water-selective, indicating that the diffusion property is the dominant factor. An N-methylol nylon-6 membrane with 33% degree of substitution showed the best membrane performance. In order to control the swelling of N-methylol nylon-6 membranes in the feed solutions of high ethanol content, thermal crosslinking was applied at 180°C for different times. It was found that heat treatment of 10 minutes gave the optimal permselectivity. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 855–863, 1997     

Trifluoroethanol/chloroalkane mixtures: Excellent novel solvents for aliphatic polyamides

Certain mixtures of TFE/CHCl₃ were found to be excellent solvents for aliphatic polyamides such as nylon-6, nylon-66, nylon-11, nylon-12, nylon-69, nylon-610, and nylon-612. Intrinsic viscosities were measured and Mark–Houwink coefficients determined for nylon-6/TFE/CHCl₃, indicating TFE-rich mixtures to be better solvents than TFE alone. Similar results were obtained for TFE/CH₂Cl₂. Four ternary phase diagrams were constructed for nylon-6/TFE/chloroalkanes, of which the ones with CHCl₃ and CH₂Cl₂ are the most interesting. In the nylon-6/TFE/CHCl₃ diagram higher nylon-6 solubility in TFE-rich mixtures and a biphasic region in the CHCl₃-rich compositions are evident. In the TFE/CH₂Cl₂ system, the higher dissolution of nylon-6 is observed, but no biphasic regions are detected. In certain solvent compositions and/or polymer concentrations the polymer is incompletely soluble, making the phase diagrams rather complicated. Observed thermodynamic excess properties appear to relate to the quality of TFE/chloroalkanes as solvents for nylon-6. Studies on swelling of nylon-6 networks immersed in TFE/CHCl₃ show a behaviour previously described by Krigbaum and Carpenter for a general case where the formation of contracts between molecules of the two solvents is discouraged and their preferential solvation of the polymer is, therefore, encouraged. The phenomena observed in this work can be qualitatively explained as arising from antagonistic interaction of TFE molecules with chloroalkane ones. The presence of the polyamides in solution reduces such contacts, enchancing the dissolution of the polymer in the (TFE-rich) solvent mixtures.     

Binary blends of nylons with ethylene vinyl alcohol copolymers: Morphological,thermal, rheological,and mechanical behavior

Binary blends of ethylene vinyl alcohol copolymers, containing 62 (EVOH-62) and 71 (EVOH-71) mole percent vinyl alcohols, with nylons (nylon-6, nylon-6/12, and nylon-12) have been prepared from melt mixing in a twin screw compounding machine. Morphological, thermal, rheological, and mechanical properties were determined. EVOH-62/nylon-6 and EVOH-71/nylon-6 blends showed homogeneous phase morphologies in the nylon-6-rich region, and fine phase separations (c.a. 2 × 10^?7 m) in the EVOH-rich region. Melting point depression, positive deviations in viscosity and flexural modulus, and negative deviation in impact strength from the simple additive rule were generally observed. And the results were possibly interpreted in terms of compatibility and increased nylon/EVOH interactions over the nylon/nylon interactions. On the contrary, clean phase separations in large domains were observed from EVOH-71/nylon-6/12 and EVOH-71 /nylon-12 blends. Fibrillation was also obtained from EVOH rich blends. Probably due to the incompatible nature of these blends, yield at low rate of shear and a mechanical property drop were also observed.     

TCY/TRA复合硫化体系对ACM/ECO共混胶性能的影响

分别采用TCY/TRA和TCY/NA-22两种硫化体系硫化 ACM/ECO共混胶.研究了不同硫化体系、TCY用量和TRA用量对ACM/ECO共混胶的硫化特性,力学性能、耐热老化性能、耐油性能和高温压缩xxx永久变形性能的影响.结果表明,TCY/TRA硫化体系能使ACM/ECO共混胶实现共硫化;其用量为1.5份/1.5份...     

Effect of Waste Tire Dust (WTD) Size on the Mechanical and Morphological Properties of Polypropylene/Waste Tire Dust (PP/WTD) Blends

Waste tire dust (WTD) of mechanically reclaimed scrap tires was blended with polypropylene (PP) in five different compositions to prepare PP/WTD blends. Three series of blends with three different sizes of WTD (250–500 µm, 500–710 µm, and 710 µm–1 mm) were prepared in a Haake Rheomix Polydrive R 600/610 at a temperature of 180°C and a rotor speed of 50 rpm for 9 min. The results show that at the same blending composition, the PP/WTD blends with fine WTD size require higher equilibrium torque and exhibit higher values of tensile strength, Young's modulus, and elongation at break (E_b) than that of blends with coarser WTD size. The swelling index of the PP/WTD blends reveals that the blends with fine WTD size have better swelling resistance in both oil and toluene than all blends with coarser WTD. Scanning electron microscope (SEM) observation indicates that the PP/WTD blends with the finest WTD size exhibit better PP/WTD adhesion than blends with coarse WTD sizes.     

Dynamic Vulcanization of Thermoplastic Elastomers Based on Poly(Epichlorohydrin-Co-Ethylene Oxide) and Polypropylene

Summary Unvulcanized and dynamically vulcanized blends of poly(epichlorohydrin-co-ethylene oxide) elastomer and polypropylene have been prepared by melt mixing in an internal mixer. The solvent resistance, morphology, dynamic mechanical and mechanical properties of these blends were studied with special reference to the effect of the crosslinking agent content. The swelling behaviour shows that the blends, with and without dynamic vulcanization, present excellent resistance to solvents ASTM A, B, C and D, at room temperature. Morphology study by scanning electron microscopy of the cryofractured surface and analysis of the dynamic mechanical properties of the system indicate that the uncrosslinked blend is immiscible and form a two-phase structure, where the rubber phase was dispersed as domains in the continuous polypropylene matrix. The mechanical properties of the crosslinked blends do not improve by increasing the doses of crosslinking agent.     

ACM/NBR共混胶性能的研究

探究了共混比对丙烯酸酯橡胶/丁腈橡胶(ACM/NBR)共混胶的硫化特性、力学性能、耐热老化性能、耐油性能、高温压缩永久变形性能和低温性能的影响。研究表明,采用TCY/S/促进剂的硫化体系时,在ACM中并用少量的NBR可以显著地提高硫化速度,最高扭矩也随着NBR用量的增加而增加,并用5 phr NBR后,共混硫化胶的拉伸强度与纯ACM硫化胶相比,提高了近17%,但NBR的并用量由5 phr增加到25 phr时,硫化胶的力学性能变化不大。随着NBR用量增加,共混硫化胶的耐热老化性能和耐油性能均变差,但高温压缩永久变形减小,耐寒性有较大改善。     

Compatibilization of SBR/NBR blends using chemically modified styrene‐co‐butadiene rubber Part 2. Effect of compatibilizer loading

The present work focuses on the compatibization of styrene‐co‐butadiene rubber (SBR)/acrylonitrile‐co‐butadiene rubber (NBR) blends with dichlorocarbene modified styrene‐co‐butadiene rubber (DCSBR) as a function of concentration of compatibilizer and composition of the blend. FTIR studies, differential scanning calorimetry and dynamic mechanical analysis reveal molecular level miscibility in the blends in the presence of compatibilizer. The formation of interfacial bonding is assessed by analysis of swelling behaviour, cure characteristics, stress–strain data and mechanical properties. These studies show that the compatibilizing action of DCSBR becomes more prominent as the proportion of NBR in the blend increases. The resistance of the vulcanizate towards thermal and oil ageing improved with compatibilization. The change in technological properties is correlated with the crosslink density of the blends assessed from swelling and stress–strain data. © 2001 Society of Chemical Industry