Increased 3HV Concentration in the Bacterial Production of 3-Hydroxybutyrate (3HB) and 3-Hydroxyvalerate (3HV) Copolymer with Acid-Digested Rice Straw Waste

Bacterial synthesis of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) copolymer [P(3HB-co-3HV)] using the hydrolysate of rice straw waste as a carbon source was affected by the composition of the hydrolysate, which depends highly on the rice straw pretreatment condition. Acid digestion with 2 % sulfuric acid generated larger production of P(3HB-co-3HV) than 6 % sulfuric acid, but 3HV concentration in the copolymer produced with 2 % acid hydrolysate was only 8.8 % compared to 18.1 % with 6 % acid hydrolysate. To obtain a higher 3HV mole fraction for enhanced flexibility of the copolymer, an additional heating was conducted with the 2 % acid hydrolysate after removal of residual rice straw. As the additional heating time increased a higher concentration of levulinic acid was generated, and consequently, the mole fraction of 3HV in P(3HB-co-3HV) increased. Among the conditions tested (i.e., 20-, 40-, 60-min), 60-min additional heating following 2 % sulfuric acid digestion achieved the highest 3HV mole fraction of 22.9 %. However, a longer heating time decreased the P(3HB-co-3HV) productivity, probably due to the increased intermediates concentrations acting as inhibitors in the hydrolysates. Therefore, the use of additional heating needs to consider both the increase in the 3HV mole fraction and the decrease in the P(3HB-co-3HV) productivity.     

Anti-biofilm Activity of Solvent-Cast and Electrospun Polyhydroxyalkanoate Membranes Treated with Lysozyme

Biofilms consist of groups of microorganisms that adhere to surfaces, such as wound and implant surfaces, making it difficult to prevent or remove their formation by antibiotic treatment, due to the innate resistance of the biofilm. Effective treatments of medical biofilms are limited. Polyhydroxyalkanoate (PHA) is a biodegradable and biocompatible polymer that is a suitable alternative to petroleum based polymers for use as a raw material for medical applications. In this study, membranes of the copolymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(HB-co-HHx)] containing different HHx monomer contents were used due to its porosity and flexibility, and different sheets were prepared by solvent-casting and electrospinning methods. The sheets were loaded with lysozyme in order to measure the maximum amount of protein adsorption and to examine the ability of immobilized enzyme to inhibit biofilm formation and detach previously established biofilms. Our results have shown maximum loading of 16.1 µg enzyme per 9.5 mm³ discs, and these sheets are effective for inhibiting biofilm formation. Also, lysozyme loaded, eletrospun sheets were observed to more effectively inhibit biofilm formation, as compared to solvent-cast sheets. Based on this study, P(HB-co-HHx) sheets are a suitable material for being used as a potential raw material for fabrication of wound dressings to be used in anti-biofilm treatments.     

Adsorption of Crystal Violet Dye from Aqueous Solution by Poly(Acrylamide-<Emphasis Type="Italic">co</Emphasis>-Maleic Acid)/Montmorillonite Nanocomposite

Poly(acrylamide-co-maleic acid)/montmorillonite nanocomposites, were synthesized via in situ polymerization with different maleic acid and MMT content. The capability of the hydrogel for adsorption of crystal violet (CV) was investigated in aqueous solutions at different pH values and temperatures. The pseudo-second-order kinetics model could fit successfully the adsorption kinetic data. The effects of maleic acid to acrylamide molar ratio (MA_R), weight percent of MMT (MMT%), the pH of medium and the solution temperature (T) on the CV adsorption capacity (q _e ) of adsorbents were studied by Taguchi experimental design approach. The results indicated that increasing the MMT% leads to a greater q _e . The q _e value of adsorbents increased also with increasing both MA_R and pH, while reduced when the temperature of medium increased. The relatively optimum conditions to achieve a maximum CV adsorption capacity for P(AAm/MA)/MMT adsorbents were found as: 0.06 for MA_R and 5 % of MMT%, medium pH = 7 and T = 20 °C.     

Comparison of three ornamental plants for phytoextraction potential of chromium removal from tannery sludge

Based on pre-experimentation, three ornamental plants, Mirabilis jalapa, Impatiens Balsamin (I. Balsamin) and Tagetes erecta L., were selected as target plants to study the phytoextraction of chromium (Cr) in tannery sludge irrigated with four treatments according to Cr concentration gradient [Control (CK); 20.50 × 10³ mg kg^?1 (T1); 51.25 × 10³ mg kg^?1 (T2); 102.50 × 10³ mg kg^?1 (T3)]. Results of pot experiments showed that the biomass of Mirabilis jalapa and Tagetes erecta L. had no significant differences among the four treatments, while I. Balsamin showed a decline trend in the biomass with the increase of Cr concentration, probably due to some extent to the poisoning effect of Cr under treatment T2 or T3. Mirabilis jalapa accumulated Cr concentration, with 408.97, 124.97, 630.16 and 57.30 mg kg^?1 in its roots, stems, leaves and inflorescence, respectively. The translocation factor and the bioaccumulation coefficient of Mirabilis jalapa are each greater than 1, indicating that Mirabilis jalapa has the strong ability to tolerate and enrich Cr by biological processes. Comparing accumulation properties of the three ornamental plants, in the amount and allocation, Mirabilis jalapa showed the highest phytoextraction efficiency and could grow well at the high Cr concentration. Our experiments suggest that Mirabilis jalapa is the expected flower species for Cr removal from tannery sludge.     

Kinetic Analysis of the Temperature Effect on Polyhydroxyalkanoate Production by <Emphasis Type="Italic">Haloferax mediterranei</Emphasis> in Synthetic Molasses Wastewater

Haloferax mediterranei is an extremely halophilic archaeon that is able to synthesize polyhydroxyalkanoate (PHA) in high salt environment with low sterility demand. In this study, a mathematical model was validated and calibrated for describing the kinetic behavior of H. mediterranei at 15, 20, 25, and 35 °C in synthetic molasses wastewater. Results showed that the production of PHA by H. mediterranei, ranging from 390 to 620 mg h^?1 L^?1, was strongly dependent on the temperature. The specific growth rate (µ _max), specific substrate utilization rate (q _max), and specific decay rate (k _d) of H. mediterranei increased with temperature following Arrhenius equation prediction. The estimated activation energy was 58.31, 25.59, and 22.38 kJ mol^?1 for the process of cell growth, substrate utilization, and cell decay of H. mediterranei, respectively. The high temperature triggered the increased PHA storage even without nitrogen limitation. Thus, working at high temperatures seems a good strategy for improving the PHA productivity of H. mediterranei.     

Biodegradation of Natural Rubber and Natural Rubber Products by <Emphasis Type="Italic">Streptomyces</Emphasis> sp. Strain CFMR 7

The rubber degrading activity of Streptomyces sp. CFMR 7 whose whole genome sequence was recently determined was tested with non-vulcanized fresh latex and common vulcanized rubber products such as latex glove, latex condom and latex car tyre. The degradation activity was unequivocally demonstrated by scanning electron microscopy with respect to microbial colonization efficiency, disintegration of rubber material and biofilm formation after 3, 6 and 9 months of inoculation. Fourier transform infrared spectroscopy comprising the attenuated total reflectance analysis on these inoculated products revealed insights into the biodegradation mechanism of this strain whereby, a decrease in the number of cis -1,4 double bonds in the polyisoprene chain, the appearance of ketone and aldehyde groups formation indicating an oxidative attack at the double bond of rubber hydrocarbon. In the presence of strain Streptomyces sp. CFMR 7, gel permeation chromatography analysis revealed a significant shift of the molecular weight distribution to lower values. Clear decrease in the molecular weight was observed over 3, 6 and 9 months of cultivation on fresh latex samples compared to other vulcanized products. No shift in the molecular weight distribution was observed for non-inoculated control. These results clearly showed that Streptomyces sp. CFMR 7 was able to cleave the carbon backbone of poly (cis -1,4-isoprene). Although this strain was able to degrade both non-vulcanized and vulcanized rubber products, faster degradation was obtained with natural rubber and rubber products with low complexity.     

Accelerated Stability Testing of a Polyherbal Transdermal Patches Using Polyvinyl Alcohol and Hydroxypropyl Methylcellulose as a Controlling Polymer Layer

The present work was to evaluate the stability potential of (E)-4-(3,4-dimethoxyphenyl)but-3-en-l-ol (Compound D) in polyherbal transdermal patches. The polyherbal formulation composed of the rhizomes of Zingiber cassumunar and Curcuma longa, leaves and stems of Cymbopogon citratus, rind and leaves of Citrus hystrix fruit, and leaves of Acacia rugata and Tamarindus indica. Polyvinyl alcohol and hydroxypropyl methylcellulose were used as a matrix film, and glycerine was used as a plasticizer. Stability testing was established for 6 months under accelerated conditions as according to International Conference on Harmonisation guidelines. Mechanical properties, moisture uptake, swelling ratio, and in vitro studies were evaluated. New Zealand white rabbits were used as the animal model. Results obtained after 6 months showed that the polyherbal transdermal patches were stable, with a good mechanical properties and hydrophilicity. In vitro study kinetics for active Compound D fitted to the Higuchi model for both release and skin permeation. The transdermal patch containing polyherbal formulation was safe to apply on the skin without irritation. Thus, transdermal patches containing this polyherbal formulation had good stability potential, with no irritation on application.     

Microbial Degradation of UV-Pretreated Low-Density Polyethylene Films by Novel Polyethylene-Degrading Bacteria Isolated from Plastic-Dump Soil

Eleven effective low-density polyethylene (LDPE)-degrading bacterial strains were isolated and identified from landfill soil containing large amounts of plastic materials. The isolates belonged to 8 genera, and included Pseudomonas (areroginosa and putida), Sphingobacterium (moltivorum), Delftia (tsuruhatansis), Stentrophomonas (humi and maltophilia), Ochrobacterum (oryzeae and humi), Micrococcus (luteus), Acinetobacter (pitti), and Citrobacter (amalonaticus). Abiotic degradation of LDPE films by artificial and natural ultraviolet (UV)-exposure was analyzed by FT-IR spectroscopy. LDPE films treated with UV-radiation were also inoculated with the isolates and biofilm production and LDPE degradation were measured. Surface changes to the LDPE induced by bacterial biofilm formation were visualized by Scanning Electron Microscopy. The most active bacterial isolate, IRN19, was able to degrade polyethylene film by 26.8?±?3.04% gravimetric weight over 4 weeks. Analysis of 16S rRNA sequence of this isolate revealed 96.97% similarity in sequence to Acinetobacter pitti, which has not previously been identified as a polyethylene-degrading bacterium. Also, most the effective biofilm forming isolate, IRN11, displayed the highest cell mass production (6.29?±?0.06 log cfu/cm²) after growth on LDPE films, showed 98.74% similarity to Sphingobacterium moltivourum.     

Biodegradation of Poly-ε-caprolactones and Poly-<Emphasis Type="SmallCaps">l</Emphasis>-lactides by Fungi

This work assessed biodegradation, by Aspergillus, Fusarium, Penicillium and Parengyodontium fungi, of four samples of poly-ε-caprolactone (PCL), three samples of poly-l-lactide (PLA) and one sample of poly-d,l-lactide (DL-PLA) produced by ring-opening polymerization initiated by aluminium complexes of corresponding lactones. Mesophilic fungal strains actively biodegrading PCL (F. solani) and PLA (Parengyodontium album and A. calidoustus) were selected. The rate of degradation by the selected fungi was found to depend on the physicochemical and mechanical properties of the polymers (molecular weight, polydispersity, crystallinity). The most degradable poly-ε-caprolactone sample was shown to have the lowest molecular weight; the most biodegradable polylactide DL-PLA had the lowest crystallinity. Mass spectral analysis of biodegraded polymer residues showed PCL to be degraded more intensively than PLA. It is established that in the case of Parengyodontium album the colonization of the films of polypropylene composites with DL-PLA is observed, which will undoubtedly contribute to their further destruction under the influence of abiotic factors in the environment.     

Water Absorption Kinetics and Hygrothermal Aging of Poly(lactic acid) Containing Halloysite Nanoclay and Maleated Rubber

Poly(lactic acid)/halloysite nanoclay composites (PLA/HNC) containing maleic anhydride grafted styrene-ethylene/butylene-styrene (SEBS-g-MAH) were produced using melt compounding followed by compression molding. The effects of hygrothermal aging on the thermal properties and functional groups changes of the HNC reinforced PLA (with and without SEBS-g-MAH) at three different temperatures (i.e., 30, 40 and 50 °C) were analyzed using differential scanning calorimetry and Fourier transform infrared spectroscopy techniques. The diffusion coefficient (D) of PLA was decreased by the incorporation of HNC and SEBS-g-MAH. The activation energy of water diffusion (E _a ) of PLA/HNC/SEBS-g-MAH nanocomposites was higher than that of pure PLA. The glass transition temperature (T _g ), cold-crystallization temperature (T _cc ) and melting temperature (T _m ) of the PLA sample were shifted to lower temperature and the effect was more pronounced at 50 °C. The carbonyl index values of all PLA samples increased after immersed in 40 and 50 °C, which is due to the formation of higher amount of carboxyl groups during the hydrolysis process.     

Enzyme-Assisted Extraction and Pb<Superscript>2+</Superscript> Biosorption of Polysaccharide from <Emphasis Type="Italic">Cordyceps militaris</Emphasis>

The enzyme assisted extraction conditions of polysaccharide from Cordyceps militaris mycelia were firstly investigated by kinetics analysis and the optimal operating was found to be: extraction temperature 40 °C; solid-solvent ratio 1:20; extraction pH 4.0; cellulase concentration 2.0%. The polysaccharide extraction yield was 5.99% under these optimized conditions. Furthermore, a fundamental investigation of the biosorption of Pb²⁺ from aqueous solution by the C. militaris polysaccharide was performed under batch conditions. The suitable pH (5.0), polysaccharide concentration (0.20 g L^?1), initial Pb²⁺ concentration (300 mg L^?1) and contact time (40 min) were outlined to enhance Pb²⁺ biosorption from aqueous medium. The Langmuir isotherm model and pseudo first order kinetic model fitted well to the data of Pb²⁺ biosorption, suggesting the biosorption of Pb²⁺ onto C. militaris polysaccharide was monolayer biosorption and physical adsorption might be the rate-limiting step that controlled the adsorption process. FTIR analysis showed that the main functional groups of C. militaris polysaccharide involved in adsorption process were carbonyl, carboxyl, and hydroxyl groups.     

Influence of Short Central PEO Segment on Hydrolytic and Enzymatic Degradation of Triblock PCL Copolymers

Hydrolytic, enzymatic degradation and composting under controlled conditions of series of triblock PCL/PEO copolymers, PCEC, with central short PEO block (M _n 400 g/mol) are presented and compared with homopolymer (PCL). The PCEC copolymers, synthesized via ring-opening polymerization of ε-caprolactone, were characterized by ¹H NMR, quantitative ¹³C NMR, GPC, DSC and WAXS. The introduction of the PEO central segment (<?2 wt%) in PCL chains significantly affected thermal degradation and crystallization behavior, while the hydrophobicity was slightly reduced as confirmed by water absorption and moisture uptake experiments. Hydrolytic degradation studies in phosphate buffer after 8 weeks indicated a small weight loss, while FTIR analysis detected changes in crystallinity indexes and GPC measurements revealed bulk degradation. Enzymatic degradation tested by cell-free extracts containing Pseudomonas aeruginosa PAO1 confirmed high enzyme activity throughout the surface causing morphological changes detected by optical microscopy and AFM analysis. The changes in roughness of polymer films revealed surface erosion mechanism of enzymatic degradation. Copolymer with the highest content of PEO segment and the lowest molecular weight showed better degradation ability compared to PCL and other copolymers. Furthermore, composting of polymer films in a model compost system at 37 °C resulted in significant degradation of the all synthesized block copolymers.     

Experimental Investigation of Cellulose/Silver Nanocomposites Using In Situ Generation Method

Cellulose gel films were prepared by regeneration process using pre-cooled aq.(8 wt% LiOH + 15 wt% urea) mixture as solvent and ethyl alcohol as non solvent. The Terminus cattapa leaf extract diffused wet cellulose films were then dipped in 1–5 mM aq.AgNO₃ solutions to allow in situ generation of silver nanoparticles (AgNPs). Besides the in situ generation, some AgNPs were also formed outside the wet films in the solution. The AgNPs formed outside the films were observed under transmission electron microscope and scanning electron microscope. The nanocomposite films were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis and tensile test. The thermal stability of the composite films was lower than that of the matrix up to a temperature of ~300 °C and afterwards showed a reverse trend. The tensile strength of the nanocomposite films was found to be higher than the matrix but decreased with increasing concentration of aq.AgNO₃. The cellulose/AgNPs composite films showed good antibacterial activity against E. coli (gram positive) and Bacillus sp. (gram negative). Based on the aforementioned properties, the cellulose/AgNPs composite films can be considered for antibacterial packaging and medical applications.     

Polyvinyl Alcohol (PVA)/Starch Bioactive Packaging Film Enriched with Antioxidants from Spent Coffee Ground and Citric Acid

The bioactive packaging polyvinyl alcohol (PVA)/starch films were prepared by incorporating combined antioxidant agents i.e. extracted spent coffee ground (ex-SCG) and citric acid. Effect of citric acid content on chemical compatibility, releasing of antioxidant, antibacterial activities, and physical and mechanical properties of PVA/starch incorporated ex-SCG (PSt-E) films was studied. The results of ATR-FTIR spectra showed that antioxidant agents of ex-SCG can penetrate into the film and the ester bond of blended films by citric acid was also observed. The presence of ex-SCG increased efficiency of antioxidant release and antimicrobial activity. The PSt-E film incorporated 30 wt% citric acid showed minimum inhibitory concentration against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The incorporation of ex-SCG and citric acid into film showed a synergistic effect on antibacterial activity. The water resistance and kinetic moisture sorption improved with incorporation of citric acid. The tensile strength and biodegradability of samples were in range of 5.63–7.44 MPa and 65.28–86.64%, respectively. Based on this study, PSt-E film incorporated 30 wt% citric acid can be applied as novel food packaging materials.     

Production,Characterization and Bioemulsifying Activity of an Exopolysaccharide Produced by <Emphasis Type="Italic">Sphingomonas</Emphasis> sp. Isolated from Freshwater

This study aimed to evaluate the emulsion stability of solutions containing exopolysaccharide and culture medium of a Sphingomonas sp. strain with various hydrophobic compounds. The exopolysaccharide characterized belongs to a sphingan group, however, not being a gellan gum as produced by certain Sphingomonas strains. In general, the emulsifying indexes found in this study were above 70% for gasoline, hexane, kerosene and used frying oil. Nonetheless, the best results were achieved in kerosene solutions, which showed an index of 80% after 24 h, remaining stable for more than 168 h in combinations with various EPS concentrations. Interestingly, diesel oil best results were singly achieved in solution pH of 11, showing an index of around 65%. Furthermore, hexane obtained an index of 100% after 24 h when culture medium was used. Thus, these findings highlight the use of EPS as a potential bioemulsifier agent to enhance hydrocarbon degradation and emulsification effects in environmental biotechnology.     

The Influence of Artificial Photodegradation on Properties of Poly(3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-3-hydroxyvalerate)(PHBV)/Graphite Nanosheets (GNS) Nanocomposites

The potential use of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/graphite nanosheets (GNS) as a biodegradable nanocomposite has been explored. PHBV/GNS nanocomposites films were prepared by solution casting at various concentrations of GNS—0.25, 0.50 and 1.00 wt% GNS. The films were exposed to artificial ultraviolet radiation (UV) during 52 h. The effect of GNS on PHBV photodegradation was investigated and compared to neat PHBV film. The artificial photodegradation induced changes in physical (weight loss), chemical carbonyl index by Fourier transform infrared spectroscopy, thermal degree of crystallinity and melting temperature by differential scanning calorimetry and morphological scanning electron microscopy characteristics. Based on the results obtained from aforementioned analyzes it was verified that GNS inhibits the oxidative degradation of PHBV matrix.     

Degradation of a Terephthalate-containing Polyester by Thermophilic Actinomycetes and <Emphasis Type="Italic">Bacillus</Emphasis> Species Derived from Composts

We intended to find thermophilic degraders of terephthalate-containing Biomax^® films. Films in mesh bags were buried in composts (inside temperature: approximately 55–60 °C), resulting in the degradation of them in 2 weeks. Fluorescent microscopy of films recovered from composts showed that microorganisms gradually covered the surface of a film during composting. DGGE analysis of microorganisms on the composted film indicated the presence of Bacillus species as main species (approximately 80% of microbial flora) and actinomycetes (approximately 10–20%) as the second major flora. Isolation of Biomax^®-utilizing bacteria was focused on these two genera: two actinomycetes and one Bacillus species were isolated as pure best degraders from the composted polymer films, which were fragmented into small pieces. All the strains were thermophilic and identified, based on their 16S rDNA analyses. Degradation of polymer films was confirmed by (1) accelerated fragmentation of films in composts, compared with a control (no inoculum) and resultant decrease in molecular weights, (2) growth in a powdered Biomax^® medium, compared with a control without powdered Biomax^®, and (3) production of terephthalate in a powdered Biomax^® medium. In this way, we concluded that these bacteria were useful for degradation of thermostable Biomax^® products.     

Selective Lead(II) Adsorption and Flocculation Characteristics of the Grafted Sodium Alginate: A Comparative Study

Synthesis of sodium alginate-g-poly(acrylamide-co-N-methylacrylamide) [S-III], sodium alginate-g-poly(N-methylacrylamide-co-N,N-dimethylacrylamide) [S-II], sodium alginate-g-poly(acrylamide-co-N,N-dimethylacrylamide) [S-I]. Sodium alginate-g-poly(N,N-dimethylacrylamide) [SAG-g-PDMA] and sodium alginate-g-poly(acrylamide) [SAG-g-PAM] were prepared by solution polymerization technique using potassium peroxydisulfate as the initiator at 70?°C in water medium. The graft copolymers were characterized by FTIR and NMR (¹H and ¹³C) spectroscopy, SEM and XRD studies. All the five graft copolymers were used to remove Pb(II) ions from the aqueous solution and also in flocculation studies of kaolin clay (1.0 wt%), silica (1.0 wt%) and iron ore slime (0.25 wt%) suspensions. A comparative studies of all the five graft copolymers were also made in both the two cases. The Pb(II) ion removal capacity of all the graft copolymers follows the order S-III?>?SAG-g-PAM?>?S-II?>?SAG-g-PDMA?>?S-I. But the flocculation performance of the graft copolymers follows the order S-II?>?S-I?>?S-III?>?SAG-g-PDMA?>?SAG-g-PAM. S-III was also used for the competitive metal ion removal with Hg(II), Cd(II), Cu(II) and Zn(II). Pb(II) adsorption of S-III (the best Pb(II) ion adsorber) follows pseudo second order rate equation and Langmuir adsorption isotherm.     

Preparation and Characterization of Polyaniline and Ag/ Polyaniline Composite Nanoporous Particles and Their Antimicrobial Activities

Polyaniline (PANI) and Ag/PANI nanoporous composite were prepared by an oxidative polymerization method. The oxidation process of PANI nanoparticles was occurred using (NH₄)₂S₂O₈ while the oxidation process of Ag/PANI nanoporous composite was occurred using AgNO₃ under the effect of artificial radiation. The structural, morphological, and optical properties of the PANI and Ag/PANI nanoporous structures were studied using different characterization tools. The results confirm the formation of polycrystalline nanoporous PANI and spherical nanoporous composite of Ag/PANI particles. Antibacterial activity tests against gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus, and gram-negative bacteria, Escherichia coli, and Salmonella species were carried out using different concentrations of PANI nanoparticles and Ag/PANI nanoporous composites. PANI has not antibacterial effect against all studied pathogens. In contrast, Ag/PANI nanoporous composites possessed antibacterial activity that is identified by the zone of inhibition. The inhibition zones of bacteria are in order; Salmonella species?>?S. aureus?>?B. subtilis?>?E. coli. The inhibition zones of all bacteria increased with increasing concentrations of Ag/PANI nanoporous composites from 200 to 400 ppm then decreased with further increasing of the dose concentrations to 600 ppm. Finally, a simplified mechanism based on the electrostatic attraction is presented to describe the antimicrobial activity of Ag/PANI nanoporous composite.     

Solubility parameters for determining optimal solvents for separating PVC from PVC-coated PET fibers

Poly(vinyl chloride) (PVC) in PVC-coated poly(ethylene terephthalate) (PET) fabrics can be separated through dissolution in a suitable solvent, leaving only the PET fibers. We investigated the solubility of PVC in 30 solvents using swelling tests. The results were compared with those obtained using the Hansen, Gutmann, Swain, E _T(30), and Kamlet–Taft parameters. For this purpose, Gaussian plots of the PVC swellability versus solubility parameter were used to decide the applicability of the solubility parameter system. Only Gutmann’s electron acceptor–donor parameter (AN + DN) and the Kamlet–Taft parameters β and π* could describe the PVC-solvent system satisfactorily. Tetrahydrofuran (THF), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), cyclohexanone, and cyclopentanone were tested for separating PVC from PET at different temperatures. THF dissolved PVC at 20 °C, while cyclohexanone and cyclopentanone did so at 40 °C. Traces of PVC remained on the PET fibers when DMF was used. Complete dissolution of PVC was not achieved at any temperature with MEK. The present work shows that solubility parameters are a helpful tool for the search for suitable solvents. It shows also that solubility parameters have to be selected carefully, since their usefulness depends strongly on the polymer properties.