Blends Of PS Research Articles

Controllable specific interactions and miscibility in polymer blends, 2. A brief description of the main results

AbstractIn this paper, we briefly report the main results of our work on the effect of introducing specific interaction on the miscibility of otherwise immiscible polymer blends. A strong proton‐donating unit (CF3)2(OH)C‐ was incorporated into polystyrene (PS(OH)). A series of blends of PS(OH) with one of polyacrylates such as PBA, PMMA, PEMA and PBMA was studied. The infrared spectra of the blends present convincing evidence of the formation of hydrogen bonding. The frequency shift of the OH stretching band due to H‐bonding is independent of the structure and composition of the hydroxyl‐containing polymers, but clearly dependent on those of the counterpolymers. Both excimer and nonradiative energy transfer (NRET) fluorescence techniques have proved effective for monitoring the variation of the degree of molecular interpenetration with the density and strength of the hydrogen bonds in the blends. TEM observations reveal clear and regular variation in the morphology of the blends with the content of hydroxyl‐containing groups. The morphological features of this kind of blends are almost controllable since the structure and/or amount of the introduced groups forming hydrogen bonding are readily adjusted in chemistry. NRET and viscosity measurements of solutions of polyacrylate and PS(OH) with relatively high hydroxyl contents in toluene provide evidence of the intermolecular complexation. In addition, the effect of introducing simultaneously crosslinking and intermolecular hydrogen bonding into blends of PS and PBA on miscibility was studied. It is concluded that single phase IPN can be prepared, but much higher content of the proton donor is needed in comparison with the blends of the corresponding linear polymers. The interlocking structure of the networks appears unfavourable to forming miscible IPN.

Thermal and photochemical stability of polystyrene and its blends with polyvinyl chloride

The influence of some irregularities in PS and PVC chains on their thermal stability was investigated. UV irradiation caused an increase in the content of these irregularities in the polymers. It was found that the presence of carbonyl groups and crosslinking of the polymer chains hamper the thermal dehydrochlorination of PVC and the total decomposition of both polymers. Weak peroxy linkages and conjugated double bonds decrease the temperature of total decomposition of PS and PVC blends

Morphology of HDPE/(PEC/PS) blends modified with SEBS copolymers

AbstractIn this study, immiscible blends of HDPE and an amorphous glassy polymer were compatibilized with styrene‐hydrogenated butadiene block copolymers. The glassy phase consisted of either pure PS or a miscible blend of PS and polyether copolymer (PEC); PEC is similar to poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). The morphology of these two‐phase mixtures depended on physical characteristics of the components and the method of fabrication. Suitable copolymers increased the degree of dispersion and minimized heterogeneities resulting from the inherent incompatibility of the individual phases. Further reduction in the phase size and increased adhesion between the components of modified blends were achieved by increasing the composition of PEC in the glassy phase. It was concluded that favorable exothermic mixing between PEC and PS endblocks of the copolymers provided an additional driving force for compatibilization. Results from dynamic mechanical thermal analysis suggests that penetration by the copolymers into the homopolymer phases is not complete.

Approach to the composition dependence of the glass transition temperature of compatible polymer blends, 2 The effect of local chain orientation

AbstractIn a previous publication a new concept has been presented for the composition dependence of the glass transition in compatible polymer blends. The concept starts with the idea that besides conformational energy barriers, contacts due to interaction are responsible for both conformation and “free” volume distribution. In accordance with the Flory‐Huggins lattice theory, the contact probability has been related to the volume fraction of the components, corrected for the different volume expansion coefficients. The concept accounts for both chainspecific and interaction‐specific contributions. It is concluded that local chain orientation due to the increased hetero‐contact interaction may explain the observed molecular weight influences on the composition dependence of Tg of polymer blends. Using experimental data for poly(vinyl methyl ether)‐polystyrene (PVME‐PS) blends it is shown that this local chain orientation due to hetero‐interaction is extremely strong in blends of the low molecular weight PS with high MW PVME. Thus, apparently, the stiffer component is dominating the Tg behaviour of compatible polymer blends.

Glass-transition temperatures of PVME - PS blends: Influence of the molecular weight of PS

Glass-transition temperatures of compatible PVME/PS blends show, beside the well-known composition dependence, a predominant influence of the molecular weight of the blend components, mainly that of PS. This influence can be reproduced by an extended Gordon-Taylor equation only. The values, however, of the parameters of the extended Gordon-Taylor equation show molecular specific correlations.

Thermally induced phase separation in poly(styrene-co-para(ortho)- -bromostyrene)-PPO and PS blends

Thermally induced phase separation in the initially compatible blends of poly(styrene-co-para-bromostyrene), poly(S-co-p-BrS), and poly(styrene- -co-ortho-bromostyrene), poly(S-co-o-BrS), with PPO and with PS was studied by DSC. It was found that the blends of PPO with copolymers containing 47 mole % or less of o-BrS have shown no phase separation after annealing at temperatures up to 573 K. By annealing PPO blends with copolymers containing p-BrS, phase separation for the blends containing 54 mole % or more of p-BrS was observed. Initially compatible PS-poly(S-co-p-BrS) (18 mole % of p-BrS or less) and PS-poly(S-co-o-BrS) (36 mole % of o-BrS or less) have shown no phase separation after annealing at temperatures up to 573 K.

Protective effect of the phenyl group in γ‐irradiated compatible blends of poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile)

AbstractThe sensitivity to radiation of mixtures of poly(methyl methacrylate) (PMMA) and polystyrene‐co‐acrylonitile) (SAN) was studied over the entire range of composition. Polystyrene‐co‐acrylonitrile, like polystyrene, is highly resistant to ionizing radiation, having a small Gx value for crosslinking (0.077) and an even smaller Gs value for main chain scission (0.055). In contrast, PMMA degrades readily under irradiation (with Gs = 1.2). In γ‐irradiated blends, the behavior of each polymer is largely influenced by the presence of the other component. Gel formation in SAN is impeded by PMMA, as a result of a decrease in Gx, and a concomitant increase in the ratio Gs/Gx. Flexural strength measurements, along with molecular weight determinations by gel permeation chromatography, demonstrated that SAN had a marked protective effect on PMMA by decreasing Gs (chain scission). This protective effect was not observed in earlier experiments with PMMA–PS blends, in spite of its chemical similarity to the system PMMA–SAN. The difference in behavior between PMMA–PS and PMMA–SAN may be explained on the basis of polymer compatibility. PMMA and SAN form a compatible pair, whereas PMMA and PS are incompatible; thus the short range protective effect of the phenyl groups in PS is inhibited.

Polymer blends—IV: Solid phase dispersants synthesized by a mechanochemical procedure

Copolymers have been synthesised by processing polyethylene/polystyrene (PE/PS) and polyethylene/poly(vinylchloride) (PE/PVC) blends in an internal mixer in the presence of radical generators. Solid phase dispersants (SPDs) were obtained by this procedure which, when incorporated into physical blends of PE and PS or PE and PVC respectively, improved the strength of the composites. They were found to be inferior to rubber-based copolymers in improving toughness.

NMR characterization of intermolecular interactions for polymers, IV. Intermolecular interactions of low molecular weight analogues for compatible blends of polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

AbstractThe intermolecular interaction, IMI, leading to the compatibility of polystyrene, PS, and poly (2,6‐dimethyl‐1,4‐phenylene oxide), PPO, has been identified by analyzing the IMI of the model compounds of low molecular weight; cumene, styrene oligomer, 2,6‐dimethyl phenol, and its trimer. The IMI has been detected and identified applying Rummens' method for the analysis of the solvent‐induced changes in NMR chemical shifts. The results indicate that the driving force in the formation of the compatible blend of PS and PPO is the π‐hydrogen bond between the electrodeficient methyl groups in PPO and π‐orbitals in PS. There were no indications that n‐hydrogen bonds are formed between ring hydrogens of PS and the oxygen in PPO.

Étude ultrasonore de mélanges diphasiques de polyéthylène basse densité et de polystyrène atactique

Ultrasonic experiments have been performed on two-phase polymer blends (low density polyethylene/polystyrene). The damping coefficient goes through a maximum and the velocity through a minimum for a 60% PS blend. The excess of damping may be attributed to a scattering of the waves by particles or by the presence of voids in the blends.

The influence of viscosity and dispersion of incompatible polymers on fibre formation in their blends

The features of fibre formation in blends of incompatible polymers, during melt-extrusion through capillaries, have been studied, using linear PE and PS blends, as a function of component viscosities, blend preparation conditions and shear stress. It was shown that fibre formation was achieved between defined limits of shear stress, depending on the ratios of viscosities of the fibre forming polymer and the polymer acting as the dispersing medium. Continuous fibres were obtained with a diameter of a few micrometers over a wide shear stress range with viscosity ratios of unity or less, in blends containing the dispersed phase. Fibre formation did not occur at higher viscosity ratios (tens of units) of the components.

Rheological properties of a polyethylene-polystyrene blend

The rheological properties of binary blends of suspension PS and low-density PE have been studied over a wide range of temperatures. Treatment of the temperature dependence of the viscosity in terms of the Vogel-Tamman equation has shown that the effect which is observed when the terminal phase separation occurs in the system, namely, a sharp reduction in the viscosity of PS at a very small PE concentration, is related to an increase in the free volume in the blend. It is suggested that the change in the glass temperature of PS when small amounts of PE are introduced into it is connected with a change in the conditions under which relaxation processes occur in the system.

Blends of PVC, PE, and PS modified by chlorinated polyethylene (CPE) and dicumyl peroxide (DCP)

Blends of PVC, PE, and PS modified by chlorinated polyethylene (CPE) and dicumyl peroxide (DCP)

Degradation of polymer mixtures. IX. Blends of polystyrene with polybutadiene

AbstractThe degradation of cis‐1,4‐polybutadiene, polystyrene, and blends of PB and PS has been studied by thermogravimetry, thermal volatilization analysis, and differential scanning calorimetry. Volatile products have been investigated and separated by subambient TVA and characterized spectroscopically. In the degradation of the blends, there is no change in the nature of the volatile products of degradation, but the rate of degradation of the PS component is markedly reduced. The PB component is the first to break down, and during the initial period of degradation of the PB, the PS degradation is apparently inhibited. It is suggested that some of the volatile products of decomposition of PB, most notably 4‐vinylcyclohexene, may diffuse into the PS phase in the blend and act as radical inhibitors.