Antiplasticization and transition to marked nonlinear viscoelasticity in poly(vinyl chloride) (PVC)/poly-ε-caprolactone (PCL) blends

Measurements of mechanical damping (tan δ) in the temperature range of ?120° to +120°C at 110 Hz, of uniaxial tensile creep at 25.0° ± 0.5°C covering creep times from 10 to 1000 sec, and of impact strength at 21°C have been carried out for a series of physical PVC/PCL blends in the composition range of 0%–12% by weight of PCL in the blend. With increasing PCL content in the blend, the α-peak of PVC was shifted to lower temperatures and became broadened. The β-peak of PVC was also shifted to lower temperatures and was markedly suppressed. The tensile creep compliance of approximately linear viscoelasticity showed a maximum decrease of 10%, and the impact resistance was reduced 3.5 times when 5% and 12% by weight of PCL, respectively, was blended with PVC. There was also a considerable increase (25%) in stress level at which the transition from approximately linear to markedly nonlinear viscoelasticity occurred when up to 5% by weight of PCL was added to the PVC. These results are attributed to the antiplasticizing effect of PCL on PVC. They support the importance of β-mechanism in the stress-activated processes proposed to be responsible for the appearance of nonlinear viscoelasticity in glassy polymers, and they are in agreement with the pseudocrosslinking concept of antiplasticization. By comparing the antiplasticization behavior of PVC/PCL blends with that of PVC/DOA and PVC/DOS from reported data, it was possible to obtaing an idea of the level of compatibility in the PVC/PCL blends. The results suggest that PCL is partially compatible with PVC.     

Morphology and physical properties of SAN/NBR blends: The effect of AN content in NBR

Poly(styrene‐co‐acrylonitrile) (SAN), of which the content of acrylonitrile (AN) repeating unit is 32 wt % (SAN32), was blended with poly(butadiene‐co‐acrylonitrile) (NBR). The effects of AN repeating unit content in NBR on the miscibility, morphology, and physical properties of SAN32/NBR (70/30 by weight) blends were studied. Differential scanning calorimetry and the morphology observed by transmission electron microscopy showed that the miscibility between SAN32 and NBR was increased as the AN content in NBR was increased up to 50 wt %. The impact strength and some other mechanical properties of the blends had the maximum value when the AN content in NBR was 34 wt %. In the measurement of viscoelasticity at melt state, SAN32/NBR blends showed yield behavior at low shear rate, and this behavior was most evident when the AN content in NBR was 34 wt %. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1861–1868, 2000     

Compatibility and nonlinear viscoelasticity of polychloroprene/polyvinyl chloride blends with nitrile butadiene rubber as a compatibilizer

Miscible polychloroprene/polyvinyl chloride (CR/PVC) blends with nitrile butadiene rubber (NBR) as a compatibilizer were prepared. The effect of NBR on the compatibility between CR and PVC was mainly analyzed by studying the thermal behavior and the phase structure of CR/PVC blends. An obvious decrement in the T_g of PVC phase successfully provided an explanation for the compatibilization of NBR. Due to the improved compatibility between CR and PVC, the size of PVC particles in CR/PVC blends decreased a lot according to the scanning electronic microscopic images. The significant improvement of mechanical properties of CR/PVC blends was in good agreement with the better compatibility between CR and PVC phases. The softening effect of NBR on the nonlinear viscoelasticity of CR/PVC blends was also studied by RPA 2000. Temperature sweep test by RPA 2000, a less reported characterization method of T_g, was successfully applied to measure T_g of CR/PVC blends and study the compatibilization of NBR. The reason for better thermal stability and the thermal decomposition mechanism of CR/PVC blends were analyzed according to the results of TGA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42448.     

Gas permeation of polymer blends. II. Poly(vinyl chloride)/acrylonitrile–butadiene copolymer (NBR) blends

The transport behavior of He, O₂, N₂, and CO₂ in a series of PVC/NBR polymer blends with varying acrylonitrile (AN) content in the NBR component has been studied at 25° and 50°C. In addition, measurements of density, crystallinity, and thermal expansion coefficients were carried out. The transport behavior of these blends is similar to previous result for PVC/EVA.¹. With increasing AN content in NBR, the permeability (P) and diffusivity (D) of the permeants decreased while the activation energy for diffusion (E_D) increased. For the polymer blends, better additivity of permeability and diffusivity was observed with increasing AN content in the NBR component. The polymer blends also showed increasing volume contraction with increasing AN content in the NBR component. These effects have been discussed as due mainly to increased polymer–polymer interaction causing reduced segmental mobility and increased compatibility of the two polymers. The sorption values calculated from P/D ratios were largely irregular and fluctuated with the blend composition. They were less reproducible than other transport parameters, i.e., P and D measured separately. Several reasons for the irregular sorption behavior were proposed.     

Photodegradation of some poly(vinyl chloride) (PVC) blends: PVC/ethylene-vinyl acetate (EVA) copolymers and PVC/butadiene-acrylonitrile (NBR) copolymers

Poly(vinyl chloride) (PVC) and its blends with polybutadiene-acrylonitrile (NBR) (containing 21.7 weight-percent acrylonitrile (AN), a heterogeneous two-phase system; and containing 41.6 weight-percent of AN, a homogeneous one-phase system) and with polyethylene-vinyl acetate (EVA) (containing 45 weight-percent of vinyl acetate (VA), a heterogenous two-phase system; and containing 65 weight-percent VA, a homogeneous one-phase system) were UV-irradiated (at 3500 Å UV-light (solar spectrum)). After UV irradiation the kinetics measurements were made of the formation of hydroperoxy (OOH) and carbonyl (CO) groups and the changes of mechanical properties: tensile strength, elongation to break, and impact energy. As a result of the photooxidative degradation of PVC blends, decreases of mechanical properties were observed. The effects are more severe in PVC/NBR blends, which contain unsaturated bonds (polybutadiene segments) than in the case of PVC/EVA. The phase structure plays an evident role on the UV degradation only of PVC/NBR blends. The photostability of PVC blends can be slightly improved by introducing Tinuvin P or Ni-chelates photostabilizers.     

Properties of ASA/SAN/NBR ternary blends: effect of AN content in NBR

Abstract

Nitrile–butadiene rubbers (NBRs) with different acrylonitrile (AN) contents were used to toughen acrylonitrile–styrene–acrylic terpolymer/styrene–acrylonitrile copolymer (ASA/SAN) blends. The properties of the ASA/SAN/NBR ternary blends were investigated via dynamic mechanical analysis, heat distortion temperature, Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). The effects of AN content in NBR on physical properties, heat resistance and morphology of the ternary blends were studied. Heat distortion temperature of the blends decreased with increasing AN content of NBR. The impact strength reached the maximum value when 20 phr NBR with 26 wt-%AN content was added. Images (SEM) were in accordance with results of mechanical properties.     

Electrical and mechanical properties of grafted and ungrafted polyacrylamide–rubber blends

A systematic dielectric and mechanical study was carried out on an ethylene propylene diene monomer (EPDM) and a nitrile rubber (NBR) blended with polyacrylamide (PAM). From the compatibility investigations, it was found that EPDM/PAM is incompatible while NBR/PAM is semicompatible. To overcome the problem of phase separation between rubber and PAM, PAM was grafted with two different monomers, acrylonitrile (AN) and acrylic acid (AA), and added with 10 phr to both EPDM and NBR. Poly(vinyl chloride) (PVC) was also added as a compatiblizing agent to both types of blend. It was concluded that the addition of either a grafted polymer or PVC to the rubber–plastic blend could improve to some extent the compatibility of such blends. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2053–2059, 1998     

Mechanical properties of PVC/SBR blends compatibilized by acrylonitrile-butadiene rubber and covulcanization

The mechanical properties of poly(vinyl chloride) (PVC)/styrene-butadiene rubber (SBR) blends compatibilized by acrylonitrile-butadiene rubber (NBR) were studied. A sulfur curing system was employed to crosslink the rubber of the blends. In the case of the blends without any curing agents, an increase in NBR content did not improve the tensile strength and elongation-at-break. However, a significant improvement in the mechanical properties was observed when NBR was added as a compatibilizer and the blend was vulcanized. In the PVC/NBR/SBR (50/10/40) blends, the tensile strength and elongation-at-break increased with an increase in sulfur concentration. This improvement was attributed to covulcanization between NBR and SBR. The fracture toughness of PVC/NBR/SBR (50/10/40) blends was characterized by the critical strain energy release rate, G_c. In the case of the PVC/NBR-29/SBR (50/10/40) blends, an increase in sulfur concentration resulted in a dramatic increase in G_c. However, the G_c value of PVC/NBR-40/SBR (50/10/40) blends decreased with an increase in sulfur concentration owing to the brittle behavior of one of the blend components—the PVC/NBR-40 (50/10) phase.     

Study on the damping of EVM based blends

The mechanical and damping properties of blends of ethylene‐vinyl acetate rubber(VA content >40 wt %) (EVM)/nitrile butadiene rubber (NBR) and EVM/ethylene‐propylene‐diene copolymer (EPDM), both with 1.4 phr BIPB (bis (tert‐butyl peroxy isopropyl) benzene) as curing agent, were investigated by DMA. The effect of polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and dicumyl peroxide (DCP) on the damping and mechanical properties of both rubber blends were studied. The results showed that in EVM/EPDM/PVC blends, EPDM was immiscible with EVM and could not expand the damping range of EVM at low temperature. PVC was miscible with EVM and dramatically improved the damping property of EVM at high temperature while keeping good mechanical performance. In EVM/NBR/PVC blends, PVC was partially miscible with EVM/NBR blends and remarkably widened the effective damping temperature range from 41.1°C for EVM/NBR to 62.4°C, while CPVC mixed EVM/NBR blends had an expanded effective damping temperature range of 63.5°C with only one damping peak. Curing agents BIPB and DCP had a similar influence on EVM/EPDM blends. DCP, however, dramatically raised the height of tan δ peak of EVM/NBR = 80/20 and expanded its effective damping temperature range to 64.9°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of the composition of α-MSAN copolymer on the miscibility of PVC/α-MSAN blends

A series of α-methylstyrene, styrene, and acrylonitrile (α-MSAN) copolymers with different acrylonitrile (AN) contents were synthesized by altering α-MSt, St, and AN ratios with emulsion copolymerization method. By melt-blending these copolymers with PVC resin and di-isooctyl phthalate (DOP), PVC/α-MSAN, and PVC/α-MSAN/DOP blends were prepared. The miscibility and morphology of the blends were investigated by dynamic mechanical analysis (DMA) and scanning electron microscopy. The PVC is immiscible with SAN by melt-mixing, whereas PVC is miscible with α-MSAN (α-MSt/St = 1/1) if AN weight percent is within the window range of 20–25 wt %, and α-MSAN (not containing St) with 35 wt % AN is miscible with PVC even when they are blended by melt-mixing. Replacement of styrene with α-methylstyrene widens the miscibility window with PVC. The miscibility of PVC/α-MSAN blends is substantially improved with the increasing α-MSt content in α-MSAN copolymer containing identical AN content. When DOP was introduced into the PVC/α-MSAN (α-MSt/St = 1/1) blends, a single tan δ peak over room temperature in DMA detection is found as AN content in α-MSAN copolymer is within the range of 15–25 wt %, and SEM observation also shows that the blends are homogeneous. When the AN content in α-MSAN copolymer is over 35 wt %, the presence of DOP causes the phase domain extended. The phase domain size of the PVC/α-MSAN/DOP blends intensively depends on AN content in α-MSAN copolymer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of single-walled carbon nanotubes on morphology and mechanical properties of NBR/PVC blends

Dynamically vulcanized thermoplastic elastomer based on Nitrile butadiene-rubber (NBR)/PVC with functionalized single-walled carbon nanotubes (f-SWNTs) and non-functionalized single-walled carbon nanotubes (SWNTs) were prepared using a brabender internal mixer. Effects of two types of SWNTs (functionalized and non-functionalized) on morphology and mechanical properties of NBR/PVC blends were studied. Results showed that the mechanical properties of NBR/PVC/SWNTs nanocomposites improved with the increasing of SWNTs content and in particular with the increase of f-SWNTs content. Moreover, the enhancement of mechanical properties of NBR/PVC blends reinforced with functionalized SWNT was higher than that of NBR/PVC blends with non-functionalized SWNT. Dispersion of SWNTs and morphology of NBR/PVC/SWNT nanocomposites were determined by scanning electron microscopy and transmission electron microscopy (TEM) techniques. TEM images illustrated that f-SWNTs were dispersed uniformly in NBR/PVC matrix while non-functionalized SWNTs showed much aggregation. Dynamic mechanical thermal analysis of NBR/PVC/SWNTs nanocomposites was also studied. The outcomes indicated that in the case of f-SWNTs, the intensity of tan ?? peak was lower than that in the case of non-functionalized SWNTs. Meanwhile, the intensity of tan ?? peak reduced when the content of f-SWNTs was increased.     

Viscoelastic properties of extrusion cast sheets of natural and synthetic aliphatic polyesters

The objective of this study was to determine the viscoelastic properties of natural (starch and protein) blends and synthetic biodegradable aliphatic copolyester blends. Blends of natural and synthetic biodegradable poly(butylene succinate) were cast into sheets using a coathanger die and then subjected to stress relaxation and creep tests at various temperatures. The natural content was varied at 10%, 30%, and 50% by weight. In some formulations a small (5% by weight) amount of compatibilizer was added. The materials were blended using a twin screw‐extruder, pelletized, and sheeted using a coathanger die. The decay of stress upon the imposition of constant strain showed two regions, an exponential and power law; the stresses relaxed sharply at the initial stage and then decayed at a reduced rate for the duration of the experiment. The addition of compatibilizers increased the time required for the stress to relax compared to uncompatibilized blends of the same composition. Similarly, as the natural content increased the time taken to relax to a specified stress level decreased. Increased temperature enhanced the relaxation process. The initial strain of the creep curves was affected by the natural content; the higher the natural content, the lower the initial strain for the samples upon imposition of a constant stress. Similarly, the presence of compatibilizer in the blend reduced the initial strain for samples containing the same natural content. As the natural content of the blend decreases, the time required to attain the plateau compliance is reduced. The equilibrium compliance increased with temperature. These behaviors are described in terms of blend morphology. The empirical Struik and power law models can be used to fit the compliance data well. POLYM. ENG. SCI., 45:1452–1460, 2005. © 2005 Society of Plastics Engineers     

Toughness,dynamic mechanical property,and morphology of polyvinylchloride/acrylonitrile‐styrene‐butyl acrylate blends

Acrylonitrile‐styrene‐butyl acrylate (ASA) graft copolymers with different acrylonitrile (AN) contents, the core‐shell ratio, and tert‐dodecyl mercaptan (TDDM) amounts were synthesized by seed emulsion polymerization. Polyvinylchloride (PVC)/ASA blends were prepared by melt blending ASA graft copolymers with PVC resin. Then the toughness, dynamic mechanical property, and morphology of the PVC/ASA blends were investigated. The results indicated that the impact strength of the PVC/ASA blends increased and then decreased with the increase of the AN content in poly(styrene‐co‐acrylonitrile (SAN) copolymer, and increased with the increase of the core‐shell ratio of ASA. It was shown that brittle‐ductile transition of PVC/ASA blends was dependent on poly(butyl acrylate) (PBA) rubber content in blends and independent of AN content in SAN copolymer. The introduction of TDDM made the toughness of PVC/ASA blends poor. Dynamic mechanical analysis (DMA) curves exhibited that PVC and SAN copolymers were immiscible over the entire AN composition range. From scanning electron microscopy (SEM), it was found that the dispersion of ASA in PVC/ASA blends was dependent on the AN content in SAN copolymer and TDDM amounts. J. VINYL ADDIT. TECHNOL., 22:43–50, 2016. © 2014 Society of Plastics Engineers     

Compatibility of poly(butadiene‐co‐acrylonitrile) with poly(L‐lactide) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

Poly(L ‐lactide) (PLLA) and poly(3‐hydrobutyrate‐co‐3‐hydroxyvalerate) (PHBV) were blended with poly(butadiene‐co‐acrylonitrile) (NBR). Both PLLA/NBR and PHBV/NBR blends exhibited higher tensile properties as the content of acrylonitrile unit (AN) of NBR increased from 22 to 50 wt %. However, two separate glass transition temperatures (T_g) appeared in PLLA/NBR blends irrespective of the content of NBR, revealing that PLLA was incompatible with NBR. In contrast, a single T_g, which shifted along with the blend composition, was observed for PHBV/NBR50 blends. Moreover NBR50 suppressed the crystallization of PHBV, indicating that PHBV was compatible with NBR50. Decrease of both elongation modulus and stress at maximum load was less significant and increase of elongation at break was more pronounced in PHBV/NBR50 blends than in PLLA/NBR50 blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3508–3513, 2004     

丁腈橡胶/聚氯乙烯共混胶

探讨了丁腈橡胶(NBR)中的结合丙烯腈质量分数、NBR／聚氯乙烯(PVC)(质量比,下同)、增塑剂邻苯二甲酸二辛酯(DOP)用量、PVC聚合度对NBR／PVC共混胶性能的影响,研究了NBR／低聚合度PVC共混胶的力学性能及加工流动性能。结果表明,随着NBR中结合丙烯腈质量分数的增加,NBR／PVC共混胶的耐油性能明显增强,力学性能也相应有所改善;NBR／PVC为80／20～60／40时．NBR／PVC共混胶的综合性能较好;DOP用量对NBR／PVC共混胶性能的影响不大;聚合度为700的PVC更适合于生产NBR／PVC共混胶,其力学性能、加工流动性能、耐老化性能与德国Bayer公司生产的牌号为Perbunan NT／VC3470B的NBR／PVC共混胶相当。     

Influence of molecular weight on some properties of poly(vinyl chloride)

Several fractions obtained from a large-scale fractionation and several unfractionated PVC polymers and blends have been processed both as rigid and plasticized compounds. The latter have been studied by stress–strain, creep, and recovery tests. The recoverable character of the creep results show that a relatively stable network must be present in the samples. The crosslink density is little influenced by molecular weight, as shown by the modulus and compliance results. On the contrary, the ultimate tensile properties depend strongly on molecular weight, which is interpreted as evidence that the stability of the crosslinks increases with increasing chain length of the polymers.     

Effect of NBR partitioning agent on the mechanical properties of PVC/NBR blends and investigation of phase morphology by atomic force microscopy

Poly(vinyl chloride) (PVC)/acrylonitrile–butadiene rubber (NBR) blends with different types of partitioning agent were obtained through melt blending. The samples were characterized according to the viscosities properties, torque rheometry and mechanical resistance as tensile testing, tear strength, and hardness. The morphology and phase imaging were studied using an atomic force microscopy operating in tapping mode (TMAFM). It was observed that the PVC/NBR blends with PVC as partitioning agent showed an increase in the tensile stress and Young’s modulus compared to the PVC/NBR blends with calcium carbonate as partitioning agent. The morphology of the blends examined by TMAFM evidenced the effect of the partitioning agent as obtained with other techniques.     

Mechanical Behavior of Polyacetal and Thermoplastic Polyurethane Elastomer Toughened Polyacetal

In view of the high potential of polyacetal (polyoxymethylene, POM)/thermoplastic polyurethane (TPU) elastomer blends in engineering applications, greater emphasis is placed on long-term properties of these blends. Though the creep behavior of pure viscoelastic polymers has been extensively studied and the temperature effect within the linear viscoelastic range has been explained on the basis of time–temperature superposition principle, only a little information is available about these blends. This work was carried out in pursuit of workable theories for actual engineering applications with their applicability defined, and secondly, to seek comprehension of the physical mechanisms which control the manifestation of nonlinear viscoelastic behavior in these blends. Validity of an equation of the type ? = ?° + ?⁺ tⁿ has been analyzed. The blends creep more than POM and the tendency to creep increases as the TPU content increases. It is found that n is a constant for a given blend and is independent of stress over the stress range considered. For all the blends, ?° is approximately a linear function of stress, whereas ?⁺ is a nonlinear function of stress irrespective of the composition of the blend. Monotonic tension tests have been carried out at three different strain rates and both POM and blends are found to be rate sensitive. Activation volume of POM and its blends with TPU has been evaluated and is found to increase as stress increases, in both cases.     

Study on compatibilization-crosslinking synergism in PVC/LDPE blends

Influences of nitrile rubber (NBR, acrylonitrile content 33.5 – 36.5 wt.-%) on the structure and mechanical properties of poly(vinyl chloride) (PVC)/low density polyethylene (LDPE) blends and its synergism with crosslinking agent have been studied. The addition of NBR to the blend is accompanied by a decrease in domain size and improvements in mechanical properties of the blend. When dicumyl peroxide (DCP) is added to the blend together with NBR, good synergism is caused and mechanical properties will improve dramatically. It is concluded that NBR can promote the phase dispersion of PVC and LDPE and their interfacial adhesion. Then, the probability of DCP existing at the interface will increase and more co-crosslinked products will form. Therefore, compatibilization and crosslinking are both exerted sufficiently.