Microstructural Development of Uniaxial Stretched Anneal-Oriented Syndiotactic Polystyrene and its Blend with Poly (2,6-dimethyl-1,4-phenylene oxide): DSC,WAXD, SAXS and FTIR Studies

Studies have been done on strain-induced microstructure development in syndiotactic polystyrene (s-PS) and its blends with poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) in 70/30 and 50/50 compositions of stretched annealed samples. Wide-angle X-ray showed that crystal orientation is less in annealed blend samples compared to annealed pure s-PS for a higher draw ratio. It increases with annealing, and relaxation occurs after a certain annealing temperature at above 180° for both s-PS and s-PS/PPO 70/30 blends. No crystal orientation was observed in the blend of s-PS/PPO 50/50 stretched samples. Small angle X-ray scattering (SAXS) shows the inclusion of amorphous PPO chains in between s-PS crystals lamella. Fourier transform infrared (FTIR) spectroscopy shows that the s-PS molecular chain packing band at 905 cm^?1 is enhanced due to annealing in oriented samples and saturates to around 0.63. The crystal chain relaxation is lower than amorphous chains of s-PS. The molecular chains of amorphous PPO are less oriented into the blend matrix, whereas its relaxation is enhanced during heat treatment and reaches an optimum value after full relaxation. The different behaviors of orientation and relaxation of s-PS and PPO chains into the blend matrix produce superstructures.     

Thermal and photochemical degradation of PPO/HIPS blends

In general, polymer blends show a degradation behavior different from a simple combination of the individual components, making any forecast difficult without experiments. Interactions between polymers can sensibilize or stabilize the blend against degradation. In this work, the thermal and photooxidative degradation of blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) and high impact polystyrene (HIPS) have been studied under accelerated conditions. The extent of degradation was accompanied by infrared spectroscopy (FTIR) and Raman spectroscopy (FT‐Raman) and impact resistance and strain–stress testing followed its influence on the macroscopic properties of the blends. The results showed that HIPS and the blend containing 60 wt % of PPO are more susceptible to thermal and photochemical degradation, while the blends containing 40 and 50 wt % of PPO are more stable. Infrared and Raman spectroscopic analyses showed that the degradation of HIPS and its blends is caused not only by degradation of the polybutadiene phase. Effects of interactions, such as exchange of energy in excited state between the PPO and PS components of the polymeric matrix may also be responsible for the degradation and loss of mechanical properties of the PPO/HIPS blends. The chemical degradation directly affects the mechanical properties of the samples with photodegradation being more harmful than the thermal degradation at 75°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Structure and mechanical properties of uniaxially oriented films of syndiotactic polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends

The structure and mechanical properties of highly oriented films of a miscible blend of syndiotactic polystyrene and poly(2,6‐dimethylphenylene‐1,4‐oxide) (sPS/PPO) were studied in the composition range of sPS/PPO = 10/0 to 5/5. The oriented films were prepared by stretching the amorphous films of the blends. Wide‐angle X‐ray diffraction and polarized FTIR spectroscopy were used to analyze the amount of mesophase and molecular orientation. Drawing of the amorphous films of sPS and sPS/PPO blend induced a highly oriented mesophase. The mesophase content increases with increasing draw ratio and becomes nearly constant above a draw ratio of 3. Under the same draw ratio, the mesophase content decreases with increasing PPO content. The orientation function in the mesophase is as high as 0.95–0.99 irrespective of the composition and draw ratio. On the other hand, the orientation of molecular chains in the amorphous phase and mesophase increases with increasing draw ratio, and it decreases with increasing PPO content. The drawn films of pure sPS show high strength and high modulus in the drawing direction, but exhibit low strength in the direction perpendicular to the drawing. In the case of sPS/PPO = 7/3 blend, however, the ultimate strength in the perpendicular direction was dramatically improved compared with that of pure sPS and the ultimate strength in the parallel direction was similar to that for the oriented pure sPS. The improved mechanical properties in the sPS/PPO blends were discussed in relation to the structural characteristics of the sPS/PPO blend system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:2789–2797, 2004     

Blends of SBS triblock copolymer with poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polystyrene mixture

Blends of styrene–butadiene–styrene (SBS) or styrene–ethylene/1‐butene–styrene (SEBS) triblock copolymers with a commercial mixture of polystyrene (PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) were prepared in the melt at different temperatures according to the chemical kind of the copolymer. Although solution‐cast SBS/PPO and SBS/PS blends were already known in the literature, a general and systematic study of the miscibility of the PS/PPO blend with a styrene‐based triblock copolymer in the melt was still missing. The thermal and mechanical behavior of SBS/(PPO/PS) blends was investigated by means of DSC and dynamic thermomechanical analysis (DMTA). The results were then compared to analogous SEBS/(PPO/PS) blends, for which the presence of a saturated olefinic block allowed processing at higher temperatures (220°C instead of 180°C). All the blends were further characterized by SEM and TGA to tentatively relate the observed properties with the blends' morphology and degradation temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2698–2705, 2003     

In situ compatibilization of PET/PS blends through reactive copolymers

Polymer blends of poly(ethylene terephthalate) (PET) and polystyrene (PS) are immiscible and incompatible, which has been well recognized. Styrene–glycidyl methacrylate (SG) copolymer has been synthesized by suspension polymerization and employed in this study as an in situ compatibilizer for the polyblends of PET and PS. This copolymer contains reactive epoxy functional groups that are able to react with PET end groups ? OH and ? COOH) under melt conditions to from SG-graft-PET copolymer. The presence of a small amount of phosphonium catalyst (200 ppm) accelerated the graft reaction and results in a better compatibilized blend. The compatibilized PET/PS blend has a smaller phase domain and higher viscosity than does the corresponding noncompatibilized blend. Mechanical properties of the compatibilized blends have also been improved significantly over the corresponding noncompatibilized blends. © 1993 John Wiley & Sons, Inc.     

Microheterogeneity in PPO/PS blends

Proton spin magnetization relaxation in the rotating frame is a simple exponential for poly(2,6-dimethylphenyleneether) (PPO) (23K)/polystyrene (PS) (9K) blends of various compositions; these blends are truly homogeneous at the spin-diffusion distance scale of a few nanometers. Blends of PPO with high molecular weight PS exhibit nonexponential decays for the PS component but exponential decays for the PPO component, indicating compositional fluctuation for PS. In some blends, the relaxations are nonexponential for both components. Three factors have been identified to promote microheterogeneity of nanometer dimensions: high polymer molecular weight, increase of temperature, and preparation of blend using solvent that induces crystallization of PPO such as toluene.     

Thermo-optical analysis of poly(2,6-dimethyl-1,4-phenylene oxide)/triblock styrene–butadiene–styrene copolymer blends

Blending of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO resin) with a triblock butadiene–styrene–butadiene copolymer (Kraton 101) monotonically increases the softening temperature of the latter as measured by TOA. The TOA transition temperatures of the styrene/PPO resin phases closely approximate those of polystyrene/PPO resin blends having the same styrene/aromatic ether unit compositions. Uniform mixtures of the styrene blocks with the poly(2,6-dimethyl-1,4-phenylene oxide) molecules is inferred.     

Polystyrene-graft-acrylic acid as compatibilizer of polystyrene/nylon 6,6 blends

Preliminary investigations to study the feasibility of using polystyrene grafted with acrylic acid to blend polystyrene (PS) and nylon 6,6 (N66) have been done. The graft copolymer (PS-g-AA) was synthesized by reacting polystyrene with acrylic acid in the presence of a free radical initiator using the solid phase graft copolymerization technique. Binary blends of N66/PS and N66/PS-g-AA were synthesized by melt mixing. The formation of a (PS-g-AA)-co-N66 copolymer during the blend preparation has been desired. The blend morphologies were observed by scanning electron microscopy (SEM). Significant reductions in the domain sizes of the dispersed minor phase were observed when PS-g-AA instead of PS was incorporated into the blend. The tensile properties of the blends were investigated. The belnds containing PS-g-AA were found to be stiffer (higher modulus) and stronger (higher tensile strength) as compared to the blends containing PS. These results are due to the better miscibility and adhesion between nylon 6,6 and the graft copolymer. The results of the rheological measurement of these blends further supports the above result and also indicates an increase in the molecular weight distribution (MWD) of the blend when polystyrene was replaced by the graft copolymer. This increase in the MWD of the compatibilized blend can be attributed to above assumed copolymer formation between the graft copolymer and nylon 6,6 due to the reaction between the carbonyl group of the acrylic acid and the amide and the terminal amine groups of nylon 6,6.     

Blends of poly(2,6-dimethyl-1,4-phenylene oxide)/ poly(styrene-co-methacrylic acid)/ poly(ethyl methacrylate-co-4-vinylpyridine)

Summary The miscibility of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with poly(styrene-co-acrylic acid) (SAA) or poly(styrene-co-methacrylic acid) (SMA) containing respectively up to 22 mol % of acrylic or methacrylic acid was studied by Differential Scanning Calorimetry and viscosimetry. All PPO/SAA or PPO/SMA blends containing 60% or less by weight of PPO were miscible and showed only one glass transition temperature (Tg). Above 60% of PPO, two Tg's were however observed for the blends in which the acid content in the SAA or SMA reaches 20% or 12% by mole respectively; the higher Tg is slightly lower than the one of pure PPO, while the lower one corresponds to a miscible blend of lower content of PPO.A DSC study showed that depending on the blend ratio, two or three glass transition temperatures were observed when a copolymer of ethyl methacrylate containing 8 mol % of 4-vinylpyridine (EM4VP-8) was added to miscible PPO/SMA-12 blends. The PPO dissolution in the SMA-12 copolymer was affected by the specific interactions that occurred between this latter copolymer and the EM4VP-8.     

Blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 toughened by maleated polystyrene‐based copolymers: Mechanical properties,morphology, and rheology

Poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 (PPO/PA6 30/70) blends were impact modified by addition of three kinds of maleated polystyrene‐based copolymers, i.e., maleated styrene‐ethylene‐butylene‐styrene copolymer (SEBS‐g‐MA), maleated methyl methacrylate‐butadiene‐styrene copolymer (MBS‐g‐MA), and maleated acrylonitrile‐butadiene‐styrene copolymer (ABS‐g‐MA). The mechanical properties, morphology and rheological behavior of the impact modified PPO/PA6 blends were investigated. The selective location of the maleated copolymers in one phase or at interface accounted for the different toughening effects of the maleated copolymer, which is closely related to their molecular structure and composition. SEBS‐g‐MA was uniformly dispersed in PPO phase and greatly toughened PPO/PA6 blends even at low temperature. MBS‐g‐MA particles were mainly dispersed in the PA6 phase and around the PPO phase, resulting in a significant enhancement of the notched Izod impact strength of PPO/PA6 blends from 45 J/m to 281 J/m at the MBS‐g‐MA content of 20 phr. In comparison, the ABS‐g‐MA was mainly dispersed in PA6 phase without much influencing the original mechanical properties of the PPO/PA6 blend. The different molecule structure and selective location of the maleated copolymers in the blends were reflected by the change of rheological behavior as well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Blends of head-to-head polystyrene with poly(2,6-dimethyl-1,4-phenylene oxide)

Blends of head-to-head polystyrene and poly(2,6-dimethyl-1,4-phenylene oxide) were prepared and found to be miscible as judged by a single T_g. The measurements were carried out by d.s.c. and dilatometry. At high concentrations of PPO (> 80%) the mixture is on the threshold of incompatibility as indicated by the increase of the width of the transition step increase by d.s.c. and the increase of the free volume as calculated from dilatometric data. The thermal stability studies of head-to-head polystyrene-(HH-PS)-poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) blends by thermal volatilization analysis show two decomposition processes in the temperature range characteristic for both homopolymers. The temperature of the maximum rate of decomposition for PPO in the blend is slightly shifted towards lower temperatures as compared with pure PPO. This can be explained by assuming that the PPO degradation is induced by radicals formed during the decomposition of HH-PS.     

Deformation behavior of HDPE/(PEC/PS)/SEBS blends

Immiscible blends of high density polyethylene (HDPE) and an amorphous glassy phase consisting of either pure polystyrene (PS) or a miscible blend of PS and a polyether copolymer (PEC) were compatibilized with various amounts of a styrene-hydrogenated butadiene block copolymer (SEBS). PEC is structurally similar to poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). Using a liquid displacement stress dilatometer, the volume change of samples during uniaxial mechanical straining was determined and related to the various modes of deformation. Blends were fabricated by both injection and compression molding. Miscible PEC and PS blends were found to undergo a craze to shear yielding transition between 40 and 60% PS, which occurred at higher PS concentrations as SEBS was added. Blends with a HDPE matrix and a dispersed glassy phase showed reduced volume dilatation on adding SEBS, indicating better interfacial adhesion between the incompatible blend components. Increases in the sample volume were substantially less in blends with a PEC/PS glassy phase instead of pure PS, suggesting more effective compatibilization by the SEBS copolymer in blends with PEC. This trend is presumed to stem from an exothermic heat of mixing between the PS endblocks of SEBS and the PEC-rich phases in the blend. Microscopic evidence of the improved adhesion and modes of deformation agrees with the results obtained by dilatometry. The volume dilatation of compression-molded materials do not seem to be similarly affected by the composition of the glassy phase which may reflect morphological differences between injection-and compression-molded blends.     

Mechanical properties of HDPE/(PEC/PS)/SEBS blends

Various amounts of a styrene-butadiene-based triblock copolymer (SEBS) was used to compatibilize immiscible blends of high density polyethylene (HDPE) and an amorphous glassy phase consisting of either pure polystyrene (PS) or a miscible blend of PS and a polyether copolymer (PEC). PEC is structurally similar to poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). Mechanical properties were determined for blends fabricated by injection and compression molding. The inherently brittle two-phase HDPE/(PEC/PS) blends show significant increases in ductility and impact strength resulting from addition of SEBS. These improvements coincide with a slight loss in modulus and yield strength. If the amount of HDPE and SEBS is held constant, impact strength and ductility increase with the amount of PEC in the glassy phase. These trends evidently result from the added ductility of glassy phases containing PEC and perhaps from better interfacial adhesion in blends after adding SEBS. The latter stems from the thermodynamic miscibility between PEC and PS endblocks of SEBS which provide an enthalpic driving force for compatibilization. Differences between the properties of compression and injection-molded blends can be attributed to the degree of crystallinity and orientation induced during molding.     

Relation between strain hardening and wear resistance of polymers

The friction and abrasive wear of blends of polystyrene (PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) were measured. The coefficient of friction decreases only slightly with an increasing PPO fraction, while the abrasive wear decreases largely upon the introduction of increasing amounts of PPO. It is clearly shown that the abrasive wear resistance of the PS/PPO blends increases with an increasing strain hardening modulus of the blend. The wear rate change between 20 and 40 wt % PPO is ascribed to a transition in the failure mechanism from predominantly brittle to predominantly tough. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2689–2692, 2004     

Synthesis, thermal properties, and specific interactions of high Tg increase in poly(2,6-dimethyl-1,4-phenylene oxide)-block-polystyrene copolymers

We have synthesized a series of block copolymers of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene (PPO-b-PS copolymer) by atom transfer radical polymerization. The PS content in these copolymer systems was determined by using infrared spectroscopy, thermal gravimetric analysis, and solution and solid-state NMR spectroscopy; good correlations exist between these characterization methods. DSC analyses indicated that the PPO-b-PS copolymers have higher glass transition temperatures than do their corresponding PPO/PS blends. Our FTIR and solid-state NMR spectroscopic analyses suggest that the PPO-b-PS copolymers possess stronger specific interactions that are responsible for the observed relatively higher values of T_g. We found one single dynamic relaxation from the dynamic mechanical analysis, which implies dynamic homogeneity exists in the PPO-b-PS copolymer; this result is consistent with the one single proton spin-lattice relaxation time observed in the rotating frame [T_1ρ(H)] during solid state NMR spectroscopic analysis. In addition, the 2D FTIR spectroscopy reveals evidence for the stronger interactions between segments of PPO and PS through the formation of π-cation complexes.     

Compatibility of poly(p-fluorostyrene-co-o-fluorostyrene) with poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene

The compatibility of blends prepared from random copolymers of p-fluorostyrene and o-fluorostyrene with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and blends of the copolymers with polystyrene (PS) has been examined using differential scanning calorimetry. It was found that compatibility in these systems depends on copolymer composition: copolymers containing from 10 to 38% of p-fluorostyrene are miscible with PPO in all proportions. The thermally induced phase separation in these systems was also studied and the existence of lower critical solution temperatures (LCST) was established for all compatible blends. The copolymers were found to be incompatible with PS regardless of composition.     

HDPE/sPS共混体系结构与性能的研究

用2种分子量不同的苯乙烯-(乙烯/丁烯)-苯乙烯三嵌段共聚物(SEBS)和一种苯乙烯-b-乙烯/丁烯(SEB)两嵌段共聚物为增容剂,对高密度聚乙烯(HDPE)/间规聚苯乙烯(sPS)共混物进行增容.采用扫描电镜(SEM)及拉伸试验研究了增溶剂的分子量及结构对共混物形态结构及力学性能的影响.结果表明:3种增容剂SEBS(SEB)均可有效地降低sPS分散相的尺寸并增加HDPE/sPS共混物的界面强度,从而提高其力学性能.sPS 的掺入可以显著提高HDPE的耐热性能.     

Compatibility of some fluorosubstituted styrene polymers and copolymers in blends with poly(2,6-dimethyl-1,4-phenylene oxide) and with polystyrene

Blends of poly(p-fluorostyrene) (PpFS), poly(o-fluorostyrene) (PoFS), poly(styrene-co-p-fluorostyrene) (SP46), poly(styrene-co-o-fluorostyrene) (SO49), with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and with polystyrene (PS), have been prepared by compression molding of coprecipitated polymers. Compatibility of these systems has been studied by differential scanning calorimetry. Detection of one or two glass transition regions was used to classify the blends as compatible or incompatible. Homopolymers of pFS and oFS were found to be incompatible with PPO and PS. The SP46 copolymer and SO49 copolymer were compatible with PPO in all proportions.     

Photo-energy transfer in polystyrene-polyphenylene oxide blends

Examination of the fluorescence intensities and lifetimes of xylenol, poly(2,6-dimethyl phenylene oxide) and polystyrene shows that energy transfer between these components is very efficient both in dilute solution and in solid blends. Quenching of excited polystyrene by poly(2,6-dimethyl phenylene oxide) is accompanied by stabilization against photo-oxidative degradation.     

Improvement of the dispersion degree in incompatible polystyrene/poly(n-butylmethacrylate) blends by the graft poly(2,6-dimethyl-1,4-phenylene oxide) on poly(n-butylmethacrylate)

Summary Using optical and electron microscopy it is evidenced that the introduction of graft copolymer poly(2,6-dimethyl-1,4-phenylene oxide) on poly (n-butylmethacrylate) improves substantially the degree of dispersion in the incompatible polymer blend polystyrene/poly (n-butylmethacrylate). The action of the copolymer is attributed-besides the mutual dissolution of the PBMA sequences — to the compatiblity between the PPO-grafts and the PS component of the blend. This is supported by the Tg data which show that the Tg of the PS in the blend is influenced by the present graft copolymer. The observed decrease of the Tg is explained by the concomitant admittance in the PS phase of the PBMA backbone together with the PPO grafts.