SAN Chains Research Articles

Correlation between non‐isothermal crystallization kinetics and morphology in poly(ε‐caprolactone)/poly(styrene‐co‐acrylonitrile) blends considering the blend phase behavior: Effects of poly(ε‐caprolactone) molecular weight

AbstractNon‐isothermal crystallization of poly(ε‐caprolactone) (PCL) in semi‐crystalline/amorphous PCL/poly(styrene‐co‐acrylonitrile) (SAN) blends with lower‐critical solution temperature (LCST) phase behavior at temperatures higher than the beginning of PCL crystallization has been studied and quantitatively modeled using different kinetics models. Near‐ and off‐critical PCL/SAN blends were prepared by using two different PCL molecular weights. The kinetics model results verified that the samples containing PCL with higher molecular weight have lower crystallinity and faster crystallization behavior, while adding amorphous SAN chains to PCL retards the crystallization process. A lower crystallization activation energy was relatively required for higher molecular weight, PCL‐2, in off‐critical PCL/SAN blends. However, the easier crystallization with higher degree of crystallinity was attained in near‐critical P80S20 blend containing PCL with lower molecular weight, indicating a shift of the LCST phase diagram of the PCL/SAN blend to higher temperatures by increasing the PCL molecular weight.

Effects of selective distribution and migration of poly(methyl methacrylate)-grafted nanoclays on the phase behavior of poly(methyl methacrylate)/poly (styrene-co-acrylonitrile) blends

The effect of selective distribution and migration behavior of two kinds of poly (methyl methacrylate)-grafted nanoclays (PMMA- g -clay) on the phase behavior of PMMA/poly (styrene- co -acrylonitrile) (SAN) blends is investigated. The grafting ratios of our two modified nanoclays are similar, but their grafting density and grafted chain lengths are different, resulting in their different initial locations and subsequent migration behaviors in the blend matrix. The PMMA- g -clay(d) nanosheets (NSs) with relatively dense and short chains are always distributed at the interfacial region and further form the percolation networks to block the concentration fluctuation and retard the domain coarsening of blend matrix more remarkably, while the PMMA- g -clay(s) NSs with relatively sparse and long chains are distributed at first in the SAN-rich domains and subsequently move slowly to the interfacial region, resulting in their inhibition of the phase separation for PMMA/SAN blend from retarding SAN chains’ viscous diffusion to their gradual interfacial aggregation for stabilizing the morphology. The variation of storage modulus for three systems in low frequency and long-time regimes are also affected by different selective distributions of two grafted clay NSs in PMMA/SAN blend matrix. • The compatibilization effects of two clay nanosheets grafted with different length and grafting density of PMMA chains were compared. • The two nanosheets have the same thermodynamically stable location but different migration behaviors. • Both the two nanosheets hardly affect the phase coarsening of polymer blend at the early stage of the spinodal decomposition. • The inhibition effects of the two nanosheets are different at intermedium and late stages.

Investigation on the effect of GMA-graft structure in SAN-g-GMA-coSt on inter-phase behavior, thermal stability, and mechanical properties of PC/SAN/GO nanocomposites

In this study, the effect of simultaneous presence of graphene oxide (GO) nanoparticles and styrene-assisted glycidyl-methacrylate-grafted SAN copolymer (SAN-g-GMA-coSt), as a compatibilizer, on inter-phase behavior, microstructure, thermal, and mechanical properties of PC/SAN blends was investigated. First, the structure of GMA-grafts on the surface of the SAN copolymer was adjusted to improve the compatibility of the blend components. The role that processing conditions play in grafting efficiency was comprehensively studied by FTIR and H-NMR techniques. The results indicated that the optimized SAN-g-GMA-coSt contained grafted sequences consist of 5 GMA molecules dispersed in every 387 carbons of the straight SAN chains. This structure of GMA-grafts reduced phase separations of the blend components and the size of droplets. GO localization in the system, controlled by two-step mixing method, was studied theoretically and the prediction was confirmed by the experimental results. The DSC and DMTA thermograms illustrated that the inter-phase region expanded probably by interactions between functional groups on the surface of GO and the epoxy section of GMA. In addition, thermogravimetric and mechanical results indicated that incorporation of nanoparticles in the presence of SAN-g-GMA-coSt increased the residual mass (char yield) at 600 C and tensile strength of nanocomposites by 55% and 37%, respectively.

Spherical nanoparticle effects on the lower critical solution temperature phase behavior of poly(ε‐caprolactone)/poly(styrene‐co‐acrylonitrile) blends: Separation of thermodynamic aspects from kinetics

ABSTRACTThe effects of spherical nanosilica particles on the lower critical solution temperature (LCST) phase diagram of poly(ε‐caprolactone) (PCL)/poly(styrene‐co‐acrylonitrile) (SAN) blends are investigated by using isochronal dynamic temperature sweep tests at different cooling rates. A stronger dependency of the rheologically determined phase‐transition points on the cooling rate is observed in the presence of nanoparticles, which results from the large contribution of entropic surface tension of chains in the Gibbs free energy of mixing and much slower rate of PCL/SAN phase dissolution. By alleviating the effects of kinetic factors, it is found that the drop in the LCST‐type phase boundary of PCL/SAN blends by adding nanofiller is more apparent than real. However, the closest LCST phase diagram to the real steady‐state thermodynamic diagram shows an unexpected shift to lower temperatures by adding nanosilica. The migration of nanosilica particles to the SAN domains especially at lower cooling rates in the dynamic measurements is the most likely explanation of these observations. The findings that prove the profound impact of kinetic factors in dynamic temperature measurements are reached in a hybrid system, wherein the SAN chains are preferentially absorbed on the surface of a nanofiller having very small primary particle size. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48679.

Selective location and migration of poly(methyl methacrylate)- grafted clay nanosheets with low grafting density in poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends

The location and migration of poly (methyl methacrylate)-grafted clay (clay-g-PMMA) nanosheets with low grafting density in a phase-separated polymer blend of poly (methyl methacrylate)/poly (styrene-co-acrylonitrile) (PMMA/SAN) was investigated. The grafting density and molecular weight for grafted PMMA chains on the surface of clay nanosheets was about 0.04 chains/nm2 and 7.8 × 104, respectively, indicating that the grafted chains might exhibit the mushroom-like distribution. With phase separation of PMMA/SAN blend matrix, the well-dispersed clay-g-PMMA nanosheets in the blend matrix were first located in the SAN-rich phase and then gradually migrated to the interface between PMMA and SAN. The first abnormal location of modified clay in the blend matrix might be attributed to the favorable interaction between clay-g-PMMA and SAN induced by the miscibility of grafted PMMA/surrounding SAN chains and the unfavorable interaction between clay-g-PMMA and PMMA without any interpenetration of grafted and matrix chains. The enhanced miscibility between grafted PMMA and surrounding SAN just began to be destroyed after being annealed for a long time, resulting in the final migration of clay-g-PMMA to the interface of PMMA/SAN (thermodynamic equilibrium state).

Effect of grafted graphene nanosheets on morphology evolution and conductive behavior of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends during isothermal annealing.

A facile method was developed for directly grafting poly(methyl methacrylate) (PMMA) to graphene oxide (GO) without surface modification, with the resultant insulating PMMA-g-GO nanosheets further reduced in situ to give conductive grafted reduced graphene oxide (RGO) nanosheets. The effect of PMMA-g-RGO nanosheets on the morphological evolution and conductive behavior of partially miscible blends of poly(methyl methacrylate)/poly (styrene-co-acrylonitrile) (PMMA/SAN) upon annealing above their phase-separation temperature was investigated using phase-contrast microscopy (PCM) with a real-time online digital picoammeter. With phase separation of the blend matrix, the well-dispersed PMMA-g-RGO nanosheets in the homogeneous matrix preferentially migrated to the SAN-rich phase and showed remarkably little aggregation. Surface grafting of PMMA-g-RGO might inhibit the aggregation of nanosheets in the blend matrix and weaken the retardation effect of nanosheets on the morphology evolution of the blend matrix. Furthermore, the percolation behavior of dynamic resistivity for ternary nanocomposites was attributed to the formation of a PMMA-g-RGO conductive network in the SAN-rich phase. The activation energy of conductive pathway formation was closer to the activation energy of flow for PMMA than that of SAN.

Non-contact percolation of unstable graphene networks in poly(styrene-co-acrylonitrile) nanocomposites: Electrical and rheological properties

Poly (styrene-co-acrylonitrile) (SAN)/chemically reduced graphene oxide (CRG) nanocomposites were prepared using a coagulation method. Due to the presence of SAN molecules that prevented CRG sheets from aggregation during reduction, CRG sheets were dispersed homogeneously in SAN. The electrical and rheological properties of the nanocomposites were systematically investigated to elucidate the structure of CRG electrical and rheological networks. With the incorporation of CRG sheets, both the electrical and rheological properties of the nanocomposites were remarkably changed. At higher CRG concentrations, the nanocomposites became electrically conductive and exhibited solid-like behaviors. According to the scaling power law, the electrical networks were constructed at a percolation threshold of 0.17 vol % compared to the rheological networks at 0.10 vol %. This discordance is attributed to the intrinsic difference in the network structure. Though both electrical and rheological networks were constructed through a non-contact mode, the rheological networks required SAN chains as bridges, while electrical networks did not. The CRG networks showed instabilities in both physical and chemical structure. Upon thermal annealing at 190 °C, the networks underwent self-improvement through disordering and thermal reduction of CRG sheets.

Influence of Molecular Weight of SAN on Rheological and Mechanical Properties of ABS-plastics

Abstract Rheological and mechanical properties of acrylonitrile-butadiene-styrene polymers (ABS) prepared via bulk polymerization depending on the molecular weight (Mw) of styrene-acrylonitrile copolymer (SAN) have been investigated. The tendencies of attaining the yield stress at steady-state shear flow and approaching to the “plateau” region of storage modulus at low frequencies in oscillatory tests were observed. Both these phenomena are induced by formation of the structural skeleton consisting of polybutadiene (PB) particles arranged in the SAN-matrix. Growth of Mw of SAN leads both to increase of the “plateau” value of storage modulus at low frequencies and the yield stress. This fact can be explained by the influence of Mw of SAN chains grafted onto PB particles on structure formation in ABS melts because of a redistribution of the ratio particle-particle / particle-matrix interactions. The elongational viscosity of ABS melts is a power function of Mw of SAN matrix. The power index of this function increases with the polymer straining that reflects orientation of SAN chains with their length increase. The strain-hardening index of ABS melts increases considerably with increase of SAN matrix Mw. However, it does not depend on presence of PB particles in the material. It means that the value of this index is governed by orientation effect in the SAN matrix. The impact strength of the investigated ABS samples is interrelated with rheological characteristics of ABS melts as well as Mw of SAN. The dependence of impact strength on Mw can be explained by increasing role of orientation effects of SAN chains with Mw increase in the copolymer fibrils connecting the walls of crazes formed at impact action.

Application of styrene‐acrylonitrile random copolymer–polyarylate block copolymer as reactive compatibilizer for polyamide and acrylonitrile‐butadiene‐styrene blends

AbstractStyrene‐acrylonitrile random copolymer (SAN) and polyarylate (PAr) block copolymer were applied as a reactive compatibilizer for polyamide‐6 (PA‐6)/acrylonitrile‐butadiene‐styrene (ABS) copolymer blends. The SAN–PAr block copolymer was found to be effective for compatibilization of PA‐6/ABS blends. With the addition of 3.0–5.0 wt % SAN–PAr block copolymer, the ABS‐rich phase could be reduced to a smaller size than 1.0 μm in the 70/30 and 50/50 PA‐6/ABS blends, although it was several microns in the uncompatibilized blends. As a result, for the blends compatibilized with 3–5 wt % block copolymer the impact energy absorption reached the super toughness region in the 70/30 and 50/50 PA‐6/ABS compositions. The compatibilization mechanism of PA‐6/ABS by the SAN–PAr block copolymer was investigated by tetrahydrofuran extraction of the SAN–PAr block copolymer/PA‐6 blends and the model reactions between the block copolymer and low molecular weight compounds. The results of these experiments indicated that the SAN–PAr block copolymer reacted with the PA‐6 during the melt mixing process via an in situ transreaction between the ester units in the PAr chain and the terminal amine in the PA‐6. As a result, SAN–PAr/PA‐6 block copolymers were generated during the melt mixing process. The SAN–PAr block copolymer was supposed to compatibilize the PA‐6 and ABS blend by anchoring the PAr/PA‐6 and SAN chains to the PA‐6 and ABS phases, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2300–2313, 2002

Chain Relaxation Time in ABS Polymer Melts.

Nonlinear relaxation modulus G(t, γ) was examined for two types of ABS polymers, the ABS-T(1) system containing agglomerated network of rubber particles and the ABS-T(3) system in which the rubber particles were randomly dispersed. Both systems exhibited fast and slow relaxation processes, the former reflecting the relaxation of the SAN chains and the latter being attributed to motion of the network and/or dispersed rubber particles. The relaxation modulus of the chains, Gchain(t,γ), was evaluated by subtracting the modulus for the slow process from the G(t,γ) data. This Gchain(t,γ) exhibited the time-strain separable damping, and its longest relaxation time τg-SAN was attributed to the entanglement relaxation of the SAN chains grafted on the rubber particles. For the ABS-T(1) system, τg-SAN rapidly increased with the volume fraction of the gel components φgel (@ volume fraction of the particles) for small φgel (< 0.2) and then leveled off at larger φgel (≥ 0.2). This behavior was related to rapid increase and saturation of the entanglement density for the grafted SAN chains on full development of the tightly connected network occurring at small φgel. In contrast, the τg-SAN of the ABS-T(3) system increased gradually with φgel, reflecting gradual increase of the entanglement density for the SAN chains grafted on the randomly dispersed rubber particles. Thus, the difference in the dispersion state of the rubber particles in the ABS-T(1) and ABS-T(3) systems naturally resulted in the difference in the entanglement relaxation time of the grafted SAN chains.

Nonlinear Stress Relaxation of ABS Polymers in the Molten State

Large deformation, nonlinear stress relaxation behavior was examined in the molten state for two types of ABS polymers, with one type containing well-dispersed rubber particles and the other, agglomerated rubber particles. These different morphologies were accomplished by adjusting the chemical composition of poly(styrene-co-acrylonitrile) (SAN) grafted on the rubber particles, such that the acrylonitrile content of the grafted SAN is equal to or different from that of the matrix SAN. The time-strain separability was found for the nonlinear relaxation of the matrix/grafted SAN chains in those ABS polymers. In the ABS polymer containing randomly dispersed rubber particles, the damping function h(γ) of the SAN chains was more strongly dependent on the strain γ than h(γ) of the pure matrix SAN chains. This difference was attributed to the filler effect in that ABS polymer. In contrast, in the ABS polymers containing networks of the agglomerated rubber particles, the SAN chains exhibited less γ-dependent h(γ)...

Reactive Compatibilization of SAN/EPR Blends. 2. Effect of Type and Content of Reactive Groups Randomly Attached to SAN

Kinetics of the poly(styrene-co-acrylonitrile)/poly(ethylene-co-propylene) (SAN/EPR) interfacial reaction has been varied by changing both the average number of reactive groups per SAN chain and the content of reactive SAN in the SAN phase, while keeping constant the overall SAN/EPR composition, i.e., 75/25 w/w. For this purpose, reactive SAN chains containing 0.004, 0.028, 0.049, and 0.078 mol/wt % of either primary amine or carbamate (an amine precursor) have been synthesized, and the content of reactive SAN in the SAN phase has been changed from 2.5 to 73.33 wt %. It appears that the number and type of reactive groups attached onto SAN affect not only the extent of the compatibilization reaction but also the compatibilization capability of the in situ formed graft copolymer in a strong dependence on molecular weight and molecular architecture.

Reactivity of functional SAN toward coreactive EPR‐g‐MA at planar interface

The grafting kinetics of reactive poly(styrene-co-acrylonitrile) (SAN) onto EPR-g-MA was studied under isothermal conditions, at the planar interface of an SAN/ethylene-propylene rubber (EPR) bilayer film in relation to the type of reactive groups, NH2 versus carbamate (which is an amine precursor), attached to SAN. The amount of SAN chemically bound to EPR chains at the interface was estimated by selectively washing off the unreacted SAN chains before X-ray photon spectroscopic analysis of the released surface. It is clear that the mutual reactivity of the reactive groups, i.e., the NH2–MA pair versus the carbamate–MA pair, has a decisive effect on the amount of SAN that reacts with EPR-g-MA at the interface. In case of SAN-carb, the grafting reaction is controlled by the thermolysis of the carbamate groups into primary amines. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3682–3689, 2000

Long-time relaxations in rubber-modified polymer systems

Linear and nonlinear viscoelastic properties were measured in the molten state for several model ABS polymers with different rubber particle contents. Linear viscoelastic functions for ABS polymers can be separated in two parts. One is a relaxation associated with the entanglement of matrix SAN chains and the other comes from the particle-particle interactions of rubber particles. This relaxation depends strongly on the degree of dispersion of rubber particles. The second-plateau modulus appeared at low frequency with samples in which rubber particles agglomerate. While, the second-plateau modulus was not observed with samples in which rubber particles are finely dispersed. Matching of AN content between grafted and matrix SAN and optimum graft density form a finely dispersed system. Large deformation relaxation measurements revealed that the damping of ABS polymers having a good dispersion of particles become stronger with an increase in rubber content. This strong damping can be explained by a layered structure. The very long relaxation was found for higher rubber content, when the neighboring grafted SAN chains contact with each other.

Reactivity of functional SAN toward coreactive EPR-g-MA at planar interface

The grafting kinetics of reactive poly(styrene-co-acrylonitrile) (SAN) onto EPR-g-MA was studied under isothermal conditions, at the planar interface of an SAN/ethylene-propylene rubber (EPR) bilayer film in relation to the type of reactive groups, NH 2 versus carbamate (which is an amine precursor), attached to SAN. The amount of SAN chemically bound to EPR chains at the interface was estimated by selectively washing off the unreacted SAN chains before X-ray photon spectroscopic analysis of the released surface. It is clear that the mutual reactivity of the reactive groups, i.e., the NH 2 -MA pair versus the carbamate-MA pair, has a decisive effect on the amount of SAN that reacts with EPR-g-MA at the interface. In case of SAN-carb, the grafting reaction is controlled by the thermolysis of the carbamate groups into primary amines.

Miscibility in thermoplastic polyurethane elastomer/poly(styrene-co-acrylonitrile) blends

Blends of a thermoplastic polyurethane (TPU) with poly(styrene-co-acrylonitrile) (SAN) were investigated by differential scanning calorimetry (DSC) and dielectric spectroscopy. Blends were prepared by kneading. A shift of the glass transition temperatures ( T g ) and specific heat increments ( ΔC p ) at the T g have shown that SAN dissolves more in the TPU-rich phase than TPU in the SAN-rich phase. From dielectric measurements it could be concluded that the relaxation processes in the TPU/SAN blends occur at the same temperatures as the relaxation processes in pure components, which suggests that the motions of TPU chains are decoupled from the motions of SAN chains. The addition of TPU to SAN copolymer causes a plasticizing effect at very low concentrations.

Orientation and miscibility of poly(ε-caprolactone)/poly(styrene- co-acrylonitrile) mixtures

The relationship between orientation and miscibility in polymer blends has been investigated for blends of poly(ε-caprolactone)/poly(styrene- co-acrylonitrile) (PCL/SAN), containing from 23 to 38 wt% acrylonitrile. The miscibility of the blends was characterized by d.s.c. whereas the strain-induced orientation of both PCL and SAN chains, in blends containing between 2% and 20% PCL, was measured by Fourier transform infra-red ( FTi.r.) dichroism. PCL orientation was observed in miscible matrices but not in immiscible SAN matrices, indicating that the miscibility leads to the orientation, and the maintenance of orientation, of the minor chain component, despite the fact that flexible chains are involved. In contrast, the major component, SAN, exhibits a similar orientation in the different PCL/SAN systems, and is little influenced by the addition of PCL. The results are discussed in terms of miscibility, chain entanglements, friction coefficients and chain flexibility.

Orientation and relaxation in uniaxially stretched poly(methyl methacrylate)-poly(styrene- co-acrylonitrile) compatible blends

The orientation and relaxation of both polymer chains in compatible blends of poly(methyl methacrylate)-poly(styrene- co-acrylonitrile) (PMMA-SAN) have been studied using Fourier transform infra-red spectroscopy. The influence of strain rate and stretching temperature on orientation have been measured. In these blends, where inter-chain interactions are almost nonexistent, both polymers orient differently over the whole concentration range, with the PMMA chains being always more oriented than the SAN chains. Orientation relaxation master curves have also been established. A change in molecular weight between entanglements does not seem to be the main factor influencing orientation and relaxation, but use of the monomeric friction coefficient, which reflects local mobility and interactions, as a scaling factor allows one to obtain two general master curves which are representative of the overall behaviour of the PMMA and SAN chains in their compatible blends.

Star‐shaped condensation polymers: Synthesis, characterization, and blend properties

AbstractA series of ϵ‐caprolactone linear and star polymers were prepared and characterized in order to determine the effect of the star architecture (i.e., star number and arm length) on the morphology of these semicrystalline polymers. A spherulitic morphology was found in all the polymers investigated. However, for six arm stars containing low degrees of polymerization, it appears that the star core dominates its morphological behavior (presumably due to its relatively high volume fraction). The star core effects, however, are markedly reduced in star polymers were the arms contain higher degrees of polymerization.The impact of the star core was further explored by investigating several poly(ϵ‐caprolactone) (PCL):styrene–acrylontrile copolymers (SAN) blends. In all instances, miscible blends were the result because a single compositionally dependent glass‐transition temperature (Tg) was observed. A moderate elevation in the Tg of the star‐shaped polymers does occur, however, compared to their linear analogs. This effect is presumably due to the inability of the SAN chains to completely mix with all segments of star structure. © 1993 John Wiley &amp; Sons, Inc.

Rheological behavior of blends of poly(methyl methacrylate) (PMMA) and poly(acrylonitrile-stat-styrene)-graft-polybutadiene (ABS)

The rheological behavior of blends of poly(methyl methacrylate) (PMMA) and poly(acrylonitrile-stat-styrene)-graft-polybutadiene (ABS) was investigated using a cone-and-plate rheometer. The rheological properties measured were shear stress (σ12), viscosity (η), and first normal stress difference (N1) as functions of shear rate (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma$ \end{document}) in steady shearing flow, and storage modulus (G′) and loss modulus (G″) as functions of frequency (ω) in oscillatory shearing flow. It has been found that the rheological behavior of blends of ABS and PMMA was very similar to that of blends of poly(styrene-stat-acrylonitrile) (SAN) and PMMA, in that N1 in logarithmic plots of N1 versus σ12, and G′ in logarithmic plots of G′ versus G″, vary regularly with blend composition. This has led us to conclude that the rubber particles that are grafted on an SAN resinous matrix in ABS resin plays only a minor role in influencing the compatibility of ABS/PMMA blends, and that the SAN chains attached to the surface of rubber particles, and the SAN matrix phase, play a major role in compatibilizing ABS resin with PMMA.