Polymeric plasticizers for PVC

High molecular weight plasticizers can be used if they have a low T_g and are miscible with PVC. For example, linear polyesters exhibit miscibility with PVC when their [CH₂]/[COO] ratio is intermediate; in that range, as “miscibility window” has been found. However, the degree of miscibility of miscible polymer blends vary with the structure of the polymers involved and thier concentration. The miscibility of these systems is often assessed by the measurement of a single T_g as a function of composition. A careful examination of experimental data of polyester/chlorinated polymer blends, as well as the use of the free volume theory, indicates that several of these systems exhibit a cusp as a function of composition, which is characterized by a critical volume fraction and a critical temperature. Specific examples are given.     

Miscibility of poly(caprolactone)/chlorinated polypropylene and poly(caprolactone)/poly(chlorostyrene) blends

Poly(caprolactone) (PCL) was blended with poly(chlorostyrene) (PSCI) and chlorinated polypropylene (PPCl). A single glass transition temperature T_g was found for these mixtures, indicating their miscibility. PCL crystallizes in these blends when the chlorinated polymer content is not too high. Otherwise, T_g becomes higher than the melting point of PCL and the high viscosity of the medium hinders the crystallization. The miscibility of PCL/PPCI blends cannot be due to hydrogen bonding between the α-hydrogens of the chlorinated polymer and the carbonyl group of the polyester since PPCI does not have available a large number of α-hydrogens. It is suggested that a dipoledipole ? C?O…Cl? C? interaction is responsible for the observed miscibility phenomenon and that this interaction is probably also responsible for the miscibility between all other polyesterchlorinated polymer mixtures. Finally, it was observed that poly(α-methyl-α-n-propyl-β-propiolactone), poly(α-methyl-α-ethyl-β-propiolactone) and poly(valerolactone) are not miscible with PSCI or PPCl, despite the fact that they are miscible with poly(vinyl chloride).     

A study of aromatic polyester/chlorinated polymer blends

A large number of studies have been devoted in recent years to the miscibility behavior of linear polyesters with chlorinated polymers, including poly(vinyl chloride) (PVC), chlorinated PVC, chlorinated poly(ethylenes), and copolymers of vinylidene chloride (Saran). However, similar studies with aromatic polyesters are lacking. It is the purpose of this paper to compare the properties of blends made of poly(ethylene terephthalate), poly(butylene terephthalate) or poly(hexamethylene terephthalate) and of various chlorinated polymers. It is shown that a high concentration of chlorine atoms is required to achieve miscibility. Moreover, there is a “miscibility window” in terms of the carbonyl concentration of polyesters, immiscibility being found for carbonyl concentrations outside this window, A similar behavior was observed before for linear polyester/chlorinated polymer blends and for polyester/polycarbonate blends. Solid state small-angle light scattering experiments were also conducted to follow the morphology of the blends as a function of composition. Spherulites were found but their size vary with composition.     

Correlation between interactions, miscibility, and spherulite growth in crystalline/crystalline blends of poly(ethylene oxide) and polyesters

Crystalline/crystalline blend systems of poly(ethylene oxide) (PEO) and a homologous series of polyesters, from poly(ethylene adipate) to poly(hexamethylene sebacate), of different CH₂/CO ratios (from 3.0 to 7.0) were examined. Correlation between interactions, miscibility, and spherulite growth rate was discussed. Owing to proximity of blend constituents' T_g's, the miscibility in the crystalline/crystalline blends was mainly justified by thermodynamic and kinetic evidence extracted from characterization of the PEO crystals grown from mixtures of PEO and polyesters at melt state. By overcoming experimental difficulty in assessing the phase behavior of two crystalline polymers with closely spaced T_g's, this work has further extended the range of polyesters that can be miscible with PEO. The interaction parameters (χ₁₂) for miscible blends of PEO with polyesters [poly(ethylene adipate), poly(propylene adipate), poly(butylene adipate), and poly(ethylene azelate) with CH₂/CO = 3.0-4.5] are all negative but the values vary with the polyester structures, with a maximum for the blend of PEO/poly(propylene adipate) (CH₂/CO = 3.5). The values of interactions are apparently dependent on the structures of the polyester constituent in the blends; interaction strength for the miscible PEO/polyester systems correlate in the same trend with the PEO crystal growth rates in the blends.     

Thermodynamics of the phase behaviour of poly(vinyl chloride)/aliphatic polyester blends

A series of linear aliphatic polyesters having $\text{CH}{}_2\text{COO}$ ratios in their repeat units from 2 to 14 have been examined for miscibility with poly(vinyl chloride). There is a window of structures in the middle of this spectrum where miscibility is observed. At the low end there is a very sharp boundary lying between $\text{CH}{}_2\text{COO}\text{= 3}$ and 4 dividing the polyesters which are immiscible with PVC from those which are miscible. At the high end the boundary is not so sharp but rather phase separation caused by a lower critical solution temperature occurs at progressively lower temperatures as $\text{CH}{}_2\text{COO}$ increases beyond 10. Thermodynamic interaction parameters for the miscible blends were obtained by analysis of the depression of the polyester melting point after correction for finite crystal thickness using the Hoffman-Weeks method. These results are compared with heats of mixing obtained directly using low molecular weight analogues of the polymers. The two results show very similar trends but are not quantitatively identical for reasons mentioned. A binary interaction model has been used to analyse the heat of mixing data, and it is concluded that there is a strong unfavourable intramolecular interaction between the -CH₂- and -COO- units in aliphatic polyesters which is an important factor in their miscibility with PVC and other polymers.     

Miscible polymer blends containing poly(vinyl chloride)

Polymer blends have received particular interest in the past several decades in both industrial and academic research. An initial survey of miscible polymer pairs (1) (1968) revealed 12 combinations. A later survey (2) (1979) noted approximately 180 miscible pairs. Today possibly over 500 miscible combinations have been noted in the open and patent literature (3). However, the vast majority of possible polymer blend combinations are not miscible (thus phase separated). A significant number of diverse polymer structures have been shown to exhibit miscibility with PVC. Several of these blends have been studied in detail and have shown specific interactions primarily involving the α-hydrogen and PVC (considered the proton donor in proton donor-proton acceptor hydrogen bonding type interactions). The blend of poly(?-caprolactone) with PVC illustrates this interaction and has been reported in many published papers. While polymer miscibility in PVC blends offers significant academic interest, industrial utility is also of considerable importance. The addition of low T_g, miscible polymers to PVC offers permanent plasticization. The addition of high T_g, miscible polymers to PVC yields the desired heat distortion temperature enhancement of rigid PVC. A specific example of permanent plasticization involves nitrile rubber blends which have been commercial since the early 1940's. This presentation will review the growing number of polymers noted to be miscible with PVC. The importance of specific interactions will be discussed.     

Weak interaction,marginal miscibility,and ring‐band spherulites in blends of poly(vinylidene fluoride) with polyesters

Fourier transform infrared (FTIR) spectroscopy, optical microscopy (OM), and differential scanning calorimetry (DSC) techniques were used to probe phase behavior and interactions in blends of poly(vinylidene fluoride) (PVDF) and polyesters [poly(trimethylene adipate) (PTA) and poly(pentamethylene adipate) (PPA)] of relatively low crystallizability. DSC thermal analysis and OM characterization proved that PVDF was miscible with PTA and PPA with a low lower critical solution temperature. Small negative values of the interaction parameters (χ₁₂ = ?0.13 for a PVDF/PPA blend) were obtained with the melting‐point depression method. FTIR spectroscopy results revealed that interactions between ? CF₂ of PVDF and the ? C?O group of the polyester were weak, in agreement with the thermal analysis results. An increase in the coarseness and/or ring‐band spacing further provided supportive evidence that miscibility did exist between the polyester and PVDF constituents in the blends. Pattern changes in ring‐band spherulites of the miscible blends further substantiated the favorable, though weak, interactions between the PVDF and polyester constituents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polyester–polycarbonate blends. V. Linear aliphatic polyesters

Polycarbonate blends with the linear aliphatic polyesters poly(ethylene succinate) (PES), poly(ethylene adipate) (PEA), poly(1,4-butylene adipate) (PBA), and poly(hexamethylene sebacate) (PHS) were prepared by solution casting. Blends containing PES, PEA, and PBA exhibited a single T_g by DSC and thus form a single, miscible amorphous phase with polycarbonate. However, blends containing PHS exhibited only partial miscibility. Crystallinity of the polyesters was reduced by mixing with polycarbonate; however, plasticization by the polyesters induced crystallization of the polycarbonate. Miscibility in these systems is the result of an exothermic heat of mixing stemming from an interaction of the carbonyl dipole of the ester group with the aromatic carbonate. The effect of polyester structure on miscibility with polycarbonate is interpreted by and correlated with heats of mixing obtained by direct calorimetry of low molecular weight liquid analogs of the polymers.     

Glass transition behavior and miscibility in blends of poly(vinyl p-phenol) with two homologous aliphatic polyesters

New miscible blend systems comprised of poly(4-vinyl phenol) (PVPh) and a homologous series of polyesters of different CH₂/CO ratios (from 4.5 to 7) was discovered. Miscibility has been confirmed using differential scanning calorimetry, Fourier-transformed infrared spectroscopy, and scanning electron microscopy. The PVPh/polyesters blends investigated exhibited a single composition-dependent glass transition and homogeneous phase morphology, and they similarly exhibited a cusp in the T_g-composition relationships. This work further extended the range of aliphatic polyesters that are known to be miscible with PVPh. The Flory-Huggins interaction parameter (χ₁₂) or energy density (B) obtained from analysis of melting point depression for PVPh/PEAz and PVPh/PHS blends are of negative values. More interestingly, the specific interactions in the PVPh/polyester blends change with the corresponding different structures in the polyester component. For the PVPh/PHS blend whose polyester constituent possesses a lower carbonyl density in the main chain (average CH₂/CO ratio=7), the energy density B was found to be −1.17 cal cm⁻³. This value is significantly lower than those for either the PVPh/PEAz (CH₂/CO=4.5) blend system (B=−7.72 cal cm⁻³). Miscibility, specific interactions, and peculiar T_g-composition relationships in the blends of PVPh with selected homologous polyesters are discussed.     

Crystallization kinetics of thermosetting polymer blends of poly(ε‐caprolactone) and unsaturated polyester resin

A study has been made of the isothermal crystallization kinetics of poly(ε‐caprolactone) (PCL) in partially miscible crosslinked polyester resin (PER)/PCL blends by using differential scanning calorimetry (DSC). For comparison, miscible blends of PCL with uncured polyester resin, i.e., oligoester resin (OER), were also investigated. The overall crystallization rate of PCL remarkably decreased with the addition of amorphous component, OER or PER. The kinetic rate constant K_n decreased sharply for both the OER/PCL blends and the crosslinked PER/PCL blends with decreasing PCL concentration. The mechanism of nucleation and geometry of the growing PCL crystals was not remarkably affected by the incorporation of OER, but changed considerably with the addition of PER. However, the overall crystallization rate of PCL in the crosslinked PER/PCL blends was much higher compared with the corresponding uncured OER/PCL blends, which is attributable to the phase‐separated structure and the reduced miscibility in the crosslinked blends. According to the nucleation and growth theories, the nucleation process was considered to be the rate controlling step in the crystallization. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 322–327, 1999     

Phase behavior of blends of aliphatic polyesters with a vinylidene chloride/vinyl chloride copolymer

A series of aliphatic polyesters having CH₂/COO ratios from 2 to 14 in their repeat units were blended with a copolymer of vinylidene chloride containing 13.5% by weight of vinyl chloride. Blends of polyesters having CH₂/COO < 4 did not form completely miscible amorphous phases, whereas polyesters having CH₂/COO ≥ 4 did form completely homogeneous amorphous phases for all temperatures below the decomposition point except for the polyester with CH₂/COO = 14 which showed reversible phase separation on heating, i.e., lower critical solution temperature behavior. Interaction parameters were estimated by melting point depression and by analog calorimetry. The behavior reported here is qualitatively similar to that reported earlier for blends of aliphatic polyesters with poly(vinyl chloride), polyepichlorohydrin, polycarbonate, styrene–allyl alcohol copolymers, and the hydroxy ether of bisphenol A.     

Miscibility of C60-end-capped poly(ethylene oxide) with poly(vinyl chloride)

The miscibility of blends of single [60]fullerene (C₆₀)-end-capped poly(ethylene oxide) (FPEO) or double C₆₀-end-capped poly(ethylene oxide) (FPEOF) with poly(vinyl chloride) (PVC) has been studied. Similar to poly(ethylene oxide) (PEO), both FPEO and FPEOF are also miscible with PVC over the entire composition range. X-ray photoelectron spectroscopy showed the development of a new low-binding-energy Cl2p doublet and a new high-binding-energy O1s peak in FPEO/PVC blends. The results show that the miscibility between FPEO and PVC arises from hydrogen bonding interaction between the α-hydrogen of PVC and the ether oxygen of FPEO. From the melting point depression of PEO, FPEO or FPEOF in the blends, the Flory-Huggins interaction parameters were found to be −0.169, −0.142, −0.093 for PVC/PEO, PVC/FPEO and PVC/FPEOF, respectively, demonstrating that all the three blend systems are miscible in the melt. However, the incorporation of C₆₀ slightly impairs the interaction between PEO and PVC.     

Polymer blends containing poly(vinylidene fluoride). Part III: Polymers containing ester,ketone, or ether groups

To further investigate the nature of the specific interaction leading to the miscibility of poly(vinylidene fluoride), PVF₂, with certain oxygen containing polymers, blends of PVF₂ with poly(ε-caprolactone), PCL, with poly(vinyl methyl ether), PVME, and with poly(vinyl methyl ketone), PVMK, were prepared. PVMK/PVF₂ blends were found to be miscible while blends of PVME/PVF₂ and PCL/PVF₂ were found not to be miscible. These results show that the specific interaction with PVF₂ involves mainly the carbonyl group rather than the entire ester group. The relative effectiveness of having this group in the chain or pendant to it is not yet resolved.     

Phase behavior of binary mixtures of oligomeric styrene/allyl alcohol copolymers and aliphatic polyesters

The phase behavior of binary mixtures of copolymers containing varying amounts of styrene and allyl alcohol (SAA) with a wide range of aliphatic polyesters has been examined. All of the copolymers and most of the polyesters had low molecular weights in the oligomeric range; hence, entropy effects were a significant factor in the observed phase behavior. The polyesters employed had CH₂/COO ratios over the entire range from 2 to 12. The SAA copolymers were completely miscible with polyesters in the middle of this range based on the observation of a single composition-dependent glass transition for these mixtures. Upper critical solution temperature behavior was observed for blends of SAA copolymers with polyesters having ratios of CH₂/COO immediately on either side of this optimum region of Polyester structure. Complete immiscibility was noted for blends with polyesters having CH₂/COO ratios at either extremity of the range examined. Interaction parameters were deduced from either melting point depression data or the cloud point observations and correlated with the structure of the components.     

Interactions of chlorinated polyolefins with ethylene‐propylene copolymers and their relevance to painted TPOs

An experimental and theoretical investigation of the phase behavior of blends of aliphatic polyesters, possessing diferent methylene content and chlorinated polypropylenes (PP‐Cl), containing 26, 32 and 65 wt% chlorine, respectively, has been performed. A window of miscibility was found only for the PP‐C165; however, this was sufficient to apply a binary interaction model of phase behavior in polymers and allow for an estimation of the segmental interaction parameters that define the overall polymer pair interaction. Complete immiscibility was found in all blends of polyesters containing PP‐C126 and PP‐C132; a result consistent with model calculations. A number of simplifications have been made concerning the structures of polymers and assumptions have been made to apply the theoretical model. The segmental interaction parameters obtained have been extended to estimate the thermodynamic interaction in blends of polyolefins and chlorinated polyolefins and then used to calculate the relevant interfacial thicknesses. These results have been compared with information presented in the literature.     

Preparation and characterization of starch/polycaprolactone blend

To make starch/polycaprolactone (PCL) blend with high miscibility, starch was chlorinated (starch‐Cl) by using methanesulfonylchloride (CH₃SO₂Cl) in dimethylformamide (DMF) prior to blending. Starch‐Cl/PCL blends were prepared by the mixing between starch‐Cl and PCL solutions under various conditions. To study the change of structure, thermal and physical characteristics of starch‐Cl/PCL blend, FTIR, DSC, SEM, and solvent resistance were measured. By blending starch‐Cl and PCL, a chemical reaction occurred partially in blend (FTIR result); thereby, the miscibility (DSC and SEM results) and solvent resistance were increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1716–1723, 2004     

Influence of intramolecular specific interactions on phase behavior of epoxy resin and poly(ε-caprolactone) blends cured with aromatic amines

Two aromatic amines were used as the curing agents to prepare the thermosetting blends of epoxy and poly(ε-caprolactone) (PCL). When cured with 4,4′-methylenebis(2-chloroaniline) (MOCA), the thermosetting blends are miscible in the amorphous state in the entire composition, which was evidenced by the behavior of single, and composition-dependent glass transition temperatures (T_g's) in terms of thermal analysis. Fourier transform infrared spectroscopy (FTIR) showed that there are the intermolecular specific interactions (viz. hydrogen bonding) between the component polymers. However, the 4,4′-diaminodiphenylsulfone (DDS)-cured epoxy forms the immiscible blends with PCL. The blends displayed a typical reaction-induced phase separation morphology. The phase behavior seems to be more than the expected since it was ever proposed that there would be the intermolecular specific interactions between amine-cured epoxy and PCL, which would fulfill the miscibility of the systems. To interpret the phase behavior, we investigated that the miscibility and intermolecular specific interactions in the blends of model compounds and linear homologues of epoxy with PCL. It was observed that in MOCA-cured blends there were much stronger intermolecular specific interactions than in DDS-cured counterparts. The weaker intermolecular specific interactions between DDS-cured epoxy and PCL resulted from the formation of the intramolecular hydrogen bonding interactions within DDS-crosslinked epoxy, which were involved with the sulfonyl groups and the secondary hydroxyls. The intramolecular association could suppress the formation of the strong intermolecular hydrogen bonding interactions between carbonyls and hydroxyls of amine-cured epoxy, which are sufficient to fulfill the homogenization of the system during the in situ polymerization. Therefore, the presence of the intramolecular specific interactions between sulfonyl and hydroxyl groups was taken as the origin of phase-separated morphology for DDS-cured blends of epoxy with PCL.     

Studies of polyester/chlorinated poly(vinyl chloride) blends

Chlorinated poly(vinyl chloride) (CPVC) was solution blended with poly(caprolactone) (PCL), poly(hexamethylene sebacate) (PHMS), poly(α-methyl-α-n-propyl-β-propiolactone) (PMPPL), poly(valerolactone) (PVL), poly(ethylene adipate), poly(ethylene succinate) and poly(β-propiolactone). From calorimetric glass transition temperature (T_g) measurements, it is concluded that CPVC is miscible with polyesters having a CH₂/COO ratio larger than three (PCL, PHMS, PMPPL and PVL). The Gordon-Taylor k parameter was also calculated and found equal to 1.0 and 0.56 for PCL/CPVC and PHMS/CPVC blends, respectively. From these values, it is concluded that CPVC gives a stronger interaction with polyesters than poly(vinyl chloride) due to its larger chlorine content.     

Miscibility and crystallization behavior of biodegradable blends of two aliphatic polyesters. Poly(3-hydroxybutyrate-co-hydroxyvalerate) and poly(ε-caprolactone)

Biodegradable polymer blends of poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(ε-caprolactone) (PCL) blends were prepared with the ratio of PHBV/PCL ranging from 80/20-20/80 by co-dissolving the two polyesters in chloroform and casting the mixture. Differential scanning calorimetry (DSC) and optical microscopy (OM) were used to investigate the miscibility and crystallization of PHBV/PCL blends. Experimental results indicated that PHBV showed no miscibility with PCL for PHBV/PCL blends as evidenced by the existence of unchanged composition independent glass transition temperature and the biphasic melt. Crystallization of PHBV and PCL was studied with DSC and analyzed by the Avrami equation by using two-step crystallization in the PHBV/PCL blends. The crystallization rate of PHBV at 70 °C decreased with the increase of PCL in the blends, while the crystallization mechanism did not change. In the case of the isothermal crystallization of PCL at 42 °C, the crystallization rate increased with the addition of PHBV, and the crystallization mechanism changed, too, indicating that the crystallization of PHBV at 70 °C had an apparent influence on the crystallization of PCL at 42 °C.     

Polymorphic and miscibility behavior in crystalline/crystalline blends of poly(pentamethylene terephthalate) with poly(heptamethylene terephthalate)

BACKGROUND: The phase behavior of blends of semicrystalline aryl polyesters with long methylene segments (? (CH₂)_n? with n = 5 or 7) in the repeat units has not been much studied. Thus, crystalline/crystalline blends comprising monomorphic poly(pentamethylene terephthalate) (PPT) and polymorphic poly(heptamethylene terephthalate) (PHepT) were prepared and the crystal growth kinetics, polymorphism behavior and miscibility in this blend system were probed using polarized‐light optical microscopy, differential scanning calorimetry and wide‐angle X‐ray diffraction. RESULTS: The PPT/PHepT blends of all compositions were first proven to be miscible in the melt state or quenched amorphous phase, whose interaction strength was determined (χ₁₂ = ? 0.35), showing favorable interactions and phase homogeneity. Although the spherulites of neat PPT and PHepT could exhibit ring bands at different crystallization temperature (T_c) ranges (100–110 and 50–65 °C, respectively), the spherulites of PPT/PHepT (50/50) blend became ringless in the range 50–110 °C. Growth analysis and polymorphic behavior in the crystalline phases of the blends provided extra evidence for the miscibility between these two crystalline polymers. Spherulitic growth rates of PPT in the PPT/PHepT blends were significantly reduced in comparison with those of neat PPT. In addition, miscible blending of a small fraction of monomorphic PPT (20 wt%) with polymorphic PHepT altered the crystal stability and led to the originally polymorphic PHepT exhibiting only the β‐crystal form when melt‐crystallized at all values of T_c. CONCLUSION: The highly intimate mixing in polymer chains of crystalline PPT and PHepT causes significant disruption in ring‐band patterns and reduction in crystallization rates of PPT as well as alteration in the polymorphic behavior of PHepT. Copyright © 2009 Society of Chemical Industry