Poly(Vinyl chloride)/plasticizer-mixture interactions—mixtures of various plasticizers of industrial importance

The Flory-Huggins interaction parameter, x, has been determined as a function of plasticizer composition, ?₂, for several ternary mixtures of poly(vinyl chloride) (PVC) and different pairs of plasticizers, selected mainly from the family of aliphatic esters. The method employed was the micro-determination of the apparent melting temperature of a PVC particle in excess plasticizer. In some systems X changed fairly gradually as a function of ?₂, while other systems exhibited a pronounced minimum in the X – ?₂ plots. Attention has been drawn to the similarity of this latter behavior to the well known co-solvency effect. The existence of such minima is of partical interest in plasticized PVC formulations.     

Poly(ε-caprolactone)-based additives: Plasticization efficacy and migration resistance

A family of poly(caprolactone) (PCL)-based oligomeric additives was evaluated as plasticizers for poly(vinyl chloride) (PVC). We found that the entire family of additives, which consist of a PCL core, diester linker, and alkyl chain cap, were effective plasticizers that improve migration resistance. The elongation at break and tensile strength of the blends made with the PCL-based additives were comparable to blends prepared with diisononyl phthalate (DINP), a plasticizer typically used industrially, and diheptyl succinate (DHPS), an alternative biodegradable plasticizer. Increasing concentration was found to decrease glass transition temperature (T_g) and increase elongation at break, confirming their role as functional plasticizers. We found that all of the PCL-based plasticizers exhibited significantly reduced leaching into hexanes compared to DINP and DHPS. The PCL-based plasticizers with shorter carbon chain lengths reduced leaching more than those with longer carbon chain lengths.     

Fusion behavior of plastisols of PVC studied by ATR-FTIR

The behavior of PVC plastisols during gelation and fusion was studied by the ATR-FTIR technique (Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy). DBP, DOP, and DIDP, three common phthalate plasticizers for PVC, were used in plastisols formulations. Three heating rates—5, 10 and 15°C/min—and formulations with different plasticizer concentrations were studied. The IR spectra of a plastisol coincides with the IR spectra of the plasticizer except for the bands at 1435 and 613 cm^?1 from the PVC (CH₂ wagging and C—Cl stretching, respectively). When the plastisol is heated, a progressive decrease of the plasticizer bands areas can be observed, while bands from PVC increase their intensity, probably because of the adsorption of the plasticizer by the resin. On cooling, the area of all bands follows the same path as when heating, but the paths separate at a certain temperature, showing the irreversible nature of this process. The analysis of the band at 1280 cm^?1 (C(O)—O from plasticizer) during heating and cooling, shows that the temperature of separation areas (T_s) takes place at temperatures coherent with plasticizer compatibility. Studies at different heating rates and different plasticizer content are in good agreement with results using other techniques, available in the literature.     

Performance relationships in PVC–plasticizer dry blending

The phenomenon of plasticizer acceptance by poly(vinyl chloride) (PVC) in hotprocess dry blending is examined via scanning electron microscopy, mercury intrusion porosimetry, and torque rheometer measurements. The effects of granule porosity, resin molecular weight, and synthesis recipe in PVC manufacture by the suspension process are related to the rate of plasticizer acceptance. For a PVC resin to dry blend, i.e., to become a free-flowing powder when mixed with plasticizer under hot-processing conditions, the resin granules must be porous. Porosity arises from interstices between primary PVC particles. At a given granule porosity, an increase in primary particle agglomeration adversely affects dry blend performance. At constant molecular weight and for resins manufactured by a given recipe, dry-blend performance is quantitatively described by granule porosity. With an increase in resin molecular weight, a greater granule porosity is required to maintain an equivalent dry-blend time (DBT). Accordingly, for most suspending agent recipes, DBT is dependent directly upon granule porosity and inversely upon molecular weight. However, if the suspending agent used in resin manufacture is an excessively rapid film former, dry-blend performance with molecular weight variation is dependent upon the suspending agent's concentration, not upon granule porosity, which must be adequate, nor upon the resin's molecular weight. An interfacial film-forming suspending agent enhances fusion of primary PVC particles at the suspension granule—water interface, increasing the granule's “pericellular membrane” thickness. This membrane, a PVC skin, does not significantly influence dry-blend performance with low- or intermediate-viscosity plasticizers. The particle skin does impede dry-blend rates with high-viscosity, poorly solvating plasticizers, but this effect can be negated in part by increasing the diameter of pore openings in the topographical skin. Dry blending occurs below the glass transition temperature (T_g) of PVC with low-viscosity plasticizers and above the T_g with high-viscosity, poorly solvating modifiers. The influence of resin and plasticizer variables indicates the dry-blend phenomenon to be a diffusion-controlled process. The rate of dry blending is dependent upon two mechanisms: (1) the rate of pore penetration—which exposes the plasticizer to a much greater surface area than if it remained exterior, encapsulating the granule—and (2) the rate of plasticizer diffusion into the PVC matrix.     

Synthesis and evaluation of dioctyl 2,5-thiophenedicarboxylate as a potentially bio-based plasticizer for poly(vinyl chloride)

In this work, dioctyl 2,5-thiophenedicarboxylate (DOT), a potentially bio-based plasticizer, was synthesized and evaluated as an alternative to traditional petroleum-based plasticizers. The chemical structure of DOT was confirmed by FTIR and ¹H NMR. Besides, its plasticization effect on poly(vinyl chloride) (PVC) was investigated in detail, and dioctyl 2,5-furandicarboxylate (DOF) as well as dioctyl isophthalate (DOIP) with similar chemical structures were used as references. The DMA results showed that the glass transition temperature (T_g) of PVC/DOT, PVC/DOF, and PVC/DOIP was 45.1°C, 33.6°C, and 51.3°C, respectively, indicating that the plasticizing efficiency of DOT was better than that of DOIP but lower than that of DOF. However, the tensile test results exhibited that the elongation at the break of PVC/DOT was higher than that of PVC/DOF, which was attributed to the easy phase separation between DOF and PVC. In addition, DOT displayed the best volatility resistance and exudation resistance among the three plasticizers, attributed to its highest molecular weight. Moreover, the migration loss of DOT in non-polar solvents was much smaller than that of DOIP because of its stronger molecular polarity. In conclusion, DOT has good potential to replace traditional petroleum-based plasticizers and be used as a primary plasticizer for PVC.     

Characterization of 1,5‐pentanediol dibenzoate as a potential “green” plasticizer for poly(vinyl chloride)

1,5‐Pentanediol dibenzoate (PDDB) was evaluated as a potential “green” plasticizer for poly(vinyl chloride) (PVC) at concentrations ranging between 20 and 80 parts by weight per hundred parts of resin. The results of glass transition temperature (T_g) and tensile tests of PDDB blends with PVC were compared with those for blends of the commercial plasticizers di(2‐ethylhexyl) phthalate (DEHP), di(ethylene glycol) dibenzoate (DEGDB), and di(propylene glycol) dibenzoate (DPGDB) in PVC. The depression in T_g and the tensile properties were comparable for a PDDB/PVC blend at a fixed composition to those of blends with DEHP, DEGDB, and DPGDB. The PDDB was subjected to biodegradation using co‐metabolism by the common soil bacterium Rhodococcus rhodochrous (ATCC 13808). After 16 days of growth, nearly all of the PDDB was degraded, and only small amounts of transient, unidentified metabolites were observed in the growth medium during the experiment. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Automated microscopic technique for evaluating poly(vinyl chloride)–plasticizer compatibility

An automated microtechnique has been developed that permits a rapid, reproducible determination of the Flory–Huggins χ interaction parameters for poly(vinyl choloride)–plasticizer systems. It is a modification of the Anagnostopoulos method of determining an apparent melting temperature of a poly(vinyl chloride) (PVC) particle in excess plasticizer. A microscope equipped with a photodiode sensor is used to measure changes in the light transmitted through a plasticizer sample containing a PVC particle as the temperature is increased at a fixed rate, either 0.2 or 1.0°C/min. Data acquisition is done by computer so that minimal operator assistance is required. The apparent melting region is characterized by a sigmoidal change in the light transmitted through a fixed sample area. This curve allows an accurate, reproducible definition of the apparent melting temperature from which the χ parameter is easily derived. The values obtained for the interaction parameter of PVC with four plasticizers chosen from the phthalate and phosphate families are in good agreement with general trends of solvent quality. Separate experiments demonstrated that the overall transmittance profile reflects changes in both the size and the optical clarity of the PVC particle during heating. This leads to added features in the profile that reflect important diffusion and swelling characteristics for a given system. © 1994 John Wiley & Sons, Inc.     

Elasticity,tear strength,and strength of adhesion of soft PVC gels

An experimental study is described of the tensile modulus E of elasticity, tear strength G_c, and strength G_a of adhesion to a Mylar substrate, for PVC gels prepared with a wide range of PVC concentrations and with four different plasticizers. The modulus E, measured under quasiequilibrium conditions, was found to be approximately proportional to c³, where c is the volume concentration of PVC. The tensile behavior suggests that the molecular strands comprising the undiluted elastic network are relatively short, only about 26 C atoms long. G_c under threshold conditions was found to vary with c^2.25 and to be considerably larger than (about 10 X) the value expected for a molecular network of short PVC chains. This difference is attributed to yielding of crystallites before molecular rupture can take place. Adhesion of PVC gels to Mylar was relatively weak. Both the tear strength and strength of adhesion were strongly dependent upon rate of fracture propagation and temperature, in good accord with the WLF rate-temperature equivalence for simple glass-forming substances. Thus, the strength of PVC gels appears to be determined largely by the glass temperature of the composition, and not by the amount or type of plasticizer except insofar as they affect the glass temperature.     

DSC study of foamable poly (vinyl chloride‐co‐vinyl acetate) plastisols of different commercial plasticizers

In this article the characterization of the thermal behavior of foamable PVC (Poly (vinyl chloride)) plastisols from 20 different plasticizers has been studied by differential scanning calorimetry (DSC). The interactions between the resin and the plasticizer as well as the decomposition of the azodicarbonamide (ADC)—the chemical blowing agent (CBA) used—have been analyzed. The latter process is of crucial importance for the knowledge of plasticized PVC flexible foam formation. Clear effects of the chemical nature of the plasticizers and their molecular weight (M_w) have been observed, both in the interactions (swelling and early stages of gelation) between the resin and the plasticizer, as well as in the temperature of the ADC decomposition and the shape of the DSC peak. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of ketal group in castor oil acid-based plasticizer on the properties of poly(vinyl chloride)

Two castor oil acid esters containing a ketal or ketone group (KCL or CL), as alternative plasticizers for poly(vinyl chloride) (PVC), were prepared. The structures were confirmed by ¹H NMR and FTIR spectroscopies. The effects of the presence of a ketal or ketone group in these compounds on PVC plasticization were examined. The DMA and SEM results showed that both plasticizers were miscible with PVC and exhibited excellent plasticizing properties, compared to those of dioctyl phthalate (DOP). The PVC plasticized by KCL displayed a lower T_g value of 20.6 ° C, which was lower than that of PVC plasticized with DOP (22.3 ° C) and PVC plasticized with CL (40.5 ° C). Tensile tests indicated that PVC plasticized using KCL showed a 37% higher of elongation at break than PVC plasticized by CL and 30% higher than PVC plasticized by DOP. The plasticizing mechanism was also investigated. Moreover, exudation, volatility, and extraction tests, along with TGA indicated that the presence of ketal groups effectively improved the migration resistance of plasticizer and the thermal stability of PVC blends. Taken together, introducing ketal groups into plasticizer might be an effective strategy for improving its plasticizing efficiency.     

The fusion characteristics of PVC-plasticizer mixtures

Dry blends of a PVC resin with various plasticizer mixtures were processed at different temperatures to produce samples of different degrees of fusion. The ease of fusion increased with decreasing the solid-gel transition temperature (Tm) of the plasticizer mixture. Nevertheless. Tm was not necessarily a linear function of the individual concentration of plasticizers in the mixture. Therefore, the ease of fusion showed in some cases an optimum at a given concentration of the plasticizer mixture.     

Evaluation of the effects of biobased plasticizers on the thermal and mechanical properties of poly(vinyl chloride)

Blends were prepared of poly(vinyl chloride) (PVC) with four different plasticizers; esters of aconitic, citric, and phthalic acids; and other ingredients used in commercial flexible PVC products. The thermal and mechanical properties of the fresh products and of the products after 6 months of aging were measured. Young's modulus of the PVC blends was reduced about 10‐fold by an increase in the plasticizer level from 15 to 30 phr from the semirigid to the flexible range according to the ASTM classification, but a 40‐phr level was required for PVC to retain its flexibility beyond 6 months. At the 40‐phr level, tributyl aconitate performed better than diisononyl phthalate (DINP) or tributyl citrate, in terms of lowering Young's modulus, both in the fresh materials and those aged for 6 months. The effects of the four plasticizers on the glass‐transition temperature (T_g) were similar, with T_g close to ambient temperature at the 30‐ and 40‐phr levels in freshly prepared samples and at 40–60°C in those aged for 6 months. The thermal stability of the PVC plasticized with DINP was superior among the group. Overall, tributyl aconitate appeared to be a good candidate for use in consumer products where the alleged toxicity of DINP may be an issue. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1366–1373, 2006     

Novel branched poly(ɛ‐caprolactone) as a nonmigrating plasticizer in flexible PVC: Synthesis and characterization

A series of hyperbranched poly(?‐caprolactone) (HPCLs, denoted as D_X) with different molecular weights were synthesized by the copolymerization of GPCL (PCL initiated by glycidol) and succinic anhydride. The chemical structure of D_X was characterized by ¹H‐NMR gel permeation chromatography and inherent viscosity, and D_X was used as the plasticizer for poly(vinyl chloride) (PVC) compared to traditional plasticizer di‐(ethylhexyl) phthalate (DEHP). The thermal properties, morphology, mechanical properties, and migration stabilities of PVC films were explored with differential scanning calorimetry, thermogravimetric analysis, scanning electron microscope, tensile, and migration tests. PVC/D₁ exhibited the best plasticization efficiency up to 107%, with enhanced tensile strength (18.5 MPa) and ultimate elongation (416%) compared to PVC/DEHP (11.5 MPa and 375%, respectively). PVC/D₁ exhibited remarkably high plasticization efficiency as compared to PVC/DEHP at a plasticizer concentration of PVC below 40 wt %. Moreover, the migration test for PVC/D_X films exhibited minimal plasticizers migration even at very harsh conditions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46542.     

Epoxidation of modified natural plasticizer obtained from rice fatty acids and application on polyvinylchloride films

In recent years, much research effort has been driven to develop alternative plasticizers for medical and commodity plastic materials. In this study, a modified natural plasticizer, synthesized by esterification of rice fatty acids, was modified by epoxidation with peroxy acid generated in situ. Two natural epoxidized plasticizers were obtained, using peracetic acid (NP‐Ac) and peroctanoic acid (NP‐Oc) as reagent. PVC films after addition of these natural epoxidized plasticizers presented fairly good incorporation and plasticizing performance, as demonstrated by results of mechanical properties, T_g values (as shown by DSC), optical microscopy, exudation, and migration tests, FTIR and X‐ray diffraction obtained for plasticized PVC films. NP‐Ac plasticizer presented enhanced plasticizing performance compared with NP‐Oc, probably due to a higher epoxidation degree obtained in the reaction with peracetic acid. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of liquid plasticizers on crystallization of PCL in soft PVC/PCL/plasticizer blends

In this work, poly(ε-caprolactone) (PCL) and liquid plasticizer were combined used to plasticize poly(vinyl chloride) (PVC), and the possibility of using PVC/PCL/plasticizer blends to fabricate soft PVC with enhanced migration resistance was investigated. Through partial replacement of liquid plasticizers in soft PVC by equal quantity of PCL, flexibility was maintained while extraction loss of plasticizer by organic solvent was reduced significantly. Furthermore, crystallization of PCL in PVC/PCL/plasticizer blends with low PCL content was observed, and crystallization rate of PCL was found to be influenced by plasticizer contents and structures. For instance, crystallization rate of PCL in PVC/PCL/diisononyl phthalate (DINP) (100/40/100) was 3.7 times faster than in PVC/PCL/DINP (100/40/80), while crystallization rate of PCL in PVC/PCL/dioctyl adipate(DOA)(100/40/100) was 8.3 times faster than in PVC/PCL/diisononyl cyclohexane-1,2-dicarboxylate (DINCH) (100/40/100). Low-field ¹H NMR test manifested that different crystallization rate of PCL in PVC/PCL/plasticizer blends with different plasticizer structures was triggered by difference in plasticizers' compatibility with PVC, that is, the number of interaction point between PVC and plasticizers. It is concluded that PCL crystallization favored by liquid plasticizers in PVC/PCL/plasticizer blends was induced by interaction competition between PVC/plasticizer and PVC/PCL. As plasticizer content increases or its compatibility with PVC decreases, interaction competition becomes more intense and consequently faster crystallization of PCL occurs. Thus, to obtain soft PVC products with improve migration resistance while avoiding PCL crystallization, the total content of plasticizer (including both liquid plasticizer and PCL) should be lower than 66 phr (40 wt %). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48803.     

Characterization of PVC cable insulation materials and products obtained after removal of additives

Organic solvents cyclohexane, dichloromethane, hexane, and tetrahydrofuran were tested to separate the dioctylphthalate (DOP) as plasticizer from the poly(vinyl chloride) (PVC)‐based materials. It was found that the efficiency of ultrasound‐enhanced hexane extraction of the DOP from PVC is 70% and the efficiency of the separation of the DOP and other compounds from the PVC by dissolution in THF followed by subsequent precipitation was 98–99%. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to characterize the thermal behavior of PVC materials before and after extraction of plasticizers. It was found that during heating in the range 20–800°C the total mass loss measured for the nontreated, extracted, and precipitated PVC samples was 71.6, 66.6, and 97%, respectively. In the temperature range 200–340°C, the release of DOP, HCl, and CO₂ was observed by simultaneous thermogravimetry (TG)/FTIR. The effect of plasticizers on thermal behavior of PVC‐based insulation material was characterized by DSC in the range ?40–140°C. It was found that, concerning the PVC cable insulation material before treatment, the value of the glass transition temperature (T_g) was 1.4°C, whereas for the PVC sample extracted by hexane, the value of T_g was 39.5°C and for the PVC dissolved in THF and subsequently precipitated, the value of T_g was 80.4°C. Moreover, the PVC samples after extraction of plasticizers, fillers, and other agents were tested to characterize their thermal degradation. The TG and FTIR results of chemically nontreated, extracted, and precipitated samples were compared. The release of DOP, HCl, CO₂, and benzene was studied during thermal degradation of the samples by FTIR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 788–795, 2006     

Succinate-based plasticizers: Effect of plasticizer structure on the mechanical and thermal performance of poly(vinyl chloride) plastic formulations

A new family of succinate-based plasticizers, consisting of molecules with a linear alkyl chain capped with n-alkyl succinates on both ends, was evaluated as potential bio-based plasticizers for stiff polymers. The influence of the central and side alkyl chain lengths on the mechanical and thermal properties as well as the migration behavior of poly(vinyl chloride) (PVC)/plasticizer blends was evaluated. The central chain length had the greatest influence on plasticizer performance, with shorter chains leading to blends with higher stress at break and surface hardness, whereas long chains produced softer blends. An optimum chain central length of five carbon atoms was observed, with longer chains leading to reduced compatibility and exudation of the plasticizer at higher plasticizer concentrations. The entire family of plasticizers performed comparably or better than the commercial plasticizer di(2-ethylhexyl) phthalate (DEHP) when incorporated into the blend at concentrations of 20–60 parts per hundred resin (phr). Overall, the succinate-based plasticizers/PVC blends all exhibited equal or improved tensile properties (by up to 77%), surface hardness (reduced by up to 43%), glass transition temperature (reduced by up to 11°C), and migration into organic media (reduced by up to 38%) when compared with blends with DEHP at 40 phr.     

Experimental assessment of the thermodynamic theory of the compositional variation of Tg: PVC systems

The glass-transition temperatures (T_g's) and specific heats (C_p) of poly(vinyl chloride) (PVC) and PVC plasticized with 5–120 phr di(2-ethylhexyl) adipate (DOA) and tri(2-ethylhexyl) trimellitate (TOTM) have been determined by differential scanning calorimetry (DSC). Measured T_g's were compared to predictions by the Couchman and Karasz (C–K) thermodynamic theory, three related empirical equations, and a new equation obtained from the C–K relation by assuming the product T_gΔC_p to be constant. It was found that the T_g's of the PVC/TOTM mixtures are adequately predicted only by the C–K and the derivative relation. The T_g's of the PVC/DOA mixtures follow a sigmoidal or cusp-like dependence on plasticizer composition as has been observed for some other PVC/plasticizer mixtures. In this case, the approximation afforded by the C–K or derivative equations is still superior to the empirical models over a wide composition range. Dynamic mechanical analysis of the PVC/DOA mixtures suggests that the DSC transitions may consist of two overlapping phase transitions. The reported sigmoidal composition dependence of the DSC T_g's may therefore result from the measured T_g's being weighted towards the temperature corresponding to the predominant dynamic mechanical transition (i.e., the high T_g phase at low plasticizer concentrations and the low T_g phase at high plasticizer concentrations). In such cases of partial phase separation, the C–K or the derivative equation may be used to estimate the composition of the two phases at each overall plasticizer concentration.     

Synthesis of difuran diesters from furfural,and their evaluation as plasticizers for polyvinyl chloride

The compounds 1,1-bis[5-(2-ethylhexyl, 2-octyl, hexyl, and butyl)carboxylate-2-furyl)ethane, and 5,5′-dihexylcarboxylate-2,2′ bifuran were synthesized from furfural and characterized for their plasticizing abilities toward polyvinyl chloride (PVC) by dynamic mechanical thermal analyses (DMTA) with di-(2-ethylhexyl)phthalate (DOP)as the standard of reference. DMTA gave values for the depression of the glass-transition temperature (T_g) per mass fraction of plasticizer, and it also yielded a set of parameters, relative to those of DOP, which describe the compatability of the furan diesters with PVC. These values are compared to those of DOP and furan diesters incorporating only one furan ring in the molecular structure, which have previously been tested by this method. The difuran plasticizers are less efficient in lowering T_g than the monofuran plasticizers or DOP, with 1,1-bis[5-(2-octyl)carboxylate-2-furyl]ethane the least efficient and 1,1-bis(5-hexylcarboxylate-2-furyl)ethane the most efficient. On average the compatability toward PVC is better than that of DOP, and similar to that of analogous monofuran structures. © 1995 John Wiley & Sons, Inc.     

Efficiency of plasticization of PVC by higher-order di-alkyl phthalates and survey of mathematical models for prediction of polymer/diluent blend Tg's

Presently, a suitable theory to predict the T_g vs. composition relationship for a given polymer-plasticizer blend, based on detailed molecular structure and molecular energitics considerations, is not available. In particular, the plasticizer efficiency parameter, k, which is uniquely defined at low-to-moderate diluent concentrations, and is an essential variable in the Mauritz-Storey theory of the diffusion of large molecules in amorphous polymers in the rubbery state, must always be determined by experiment. In this work, k was determined by DSC for PVC that was plasticized over a range of concentrations with a number of higher branched and linear di-alkyl phthalates. The results will be used in our plasticizer diffusion theory as well as provide guidance in the future development of a general mathematical model for predicting k. It was seen that k decreased with increasing molecular weight for both the linear and branched phthalates. For a given molecular weight, the branched phthalates have higher k values than the linear structures. These results have been rationalized in terms of the additional free volume created by the inefficiency of packing polymer chains about these large penetrant molecules. The DSC scans also implied an increasing degree of microstructural heterogeneity with increasing plasticizer concentration. Finally, relationships between plasticizer diffusion coefficient in the rubbery state and the plasticized T_g were established for low-to-moderate diluent concentration for three of the plasticizers studied by utilizing experimental diffusion data from our earlier work on these systems.