Microwave assisted glycolysis of poly(ethylene terephthalate) catalyzed by 1‐butyl‐3‐methylimidazolium bromide ionic liquid

The combination of ionic liquid (IL) associated with microwave energy may have some potential application in the chemical recycling of poly (ethylene terephthalate). In this processes, glycolysis of waste poly (ethylene terephthalate) recovered from bottled water containers were thermally depolymerized with solvent ethylene glycol (EG) in the presence of 1‐butyl‐3‐methyl imidazolium bromide ([bmim]Br) as catalyst (IL) under microwave condition. It was found that the glycolysis products consist of bis (2‐hydroxyethyl) terephthalate (BHET) monomer that separated from the catalyst IL in pure crystalline form. The conversion of PET reach up to 100% and the yield of BHET reached 64% (wt %). The optimum performance was achieved by the use of 1‐butyl‐3‐methyl imidazolium bromide as a catalyst, microwave irradiations temperature (170–175°C) and reaction time 1.75–2 h. The main glycolysis products were analyzed by ¹H NMR, ¹³C NMR, LC‐MS, FTIR, DSC, and TGA. When compared to conventional heating methods, microwave irradiation during glycolysis of PET resulted in short reaction time and more control over the temperature. This has allowed substantial saving in energy and processing cost. In addition, a more efficient, environmental‐friendly, and economically feasible chemical recycling of waste PET was achieved in a significantly reduced reaction time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41666.     

Ionic Liquid, 1‐n‐Butyl‐3‐methylimidazolium Bis(trifluoromethanesulfonyl)imide,Resulted in the First Catalyst‐Free Aminohalogenation of Electron‐Deficient Alkenes

The 2‐Ns‐based aminohalogenation of α,β‐unsaturated ketones has been achieved in an ionic liquid, 1‐n‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide {[bmim][N(SO₂CF₃)₂]}. [Bmim][N(SO₂CF₃)₂] was found to be superior not only to classical organic solvents but also to its counterpart, [bmim][BF₄], which was proven to be successful in the TsNCl₂‐based aminohalogenation but failed to give any product for this reaction. The present process takes the advantage of 2‐NsNCl₂ as the stable nitrogen/halogen source in a one‐pot operation without the use of any metal catalysts, it is convenient to perform without special protection of inert gases. Eight examples were examined with good to excellent stereoselectivity (1:5 to one isomer) and modest to good chemical yields (53–72 %).     

Butanol alcoholysis reaction of polyethylene terephthalate using acidic ionic liquid as catalyst

The alcoholysis reaction of polyethylene terephthalate (PET) and n‐butanol to produce dibutyl terephthalate (DBTP) and ethylene glycol (EG) was investigated in the presence of a Brönsted–Lewis acidic ionic liquid (IL). It was found that a synergetic effect of Brönsted and Lewis acid sites enhanced the IL catalytic performance, and (3‐sulfonic acid) propyltriethylammonium chlorozincinate [HO₃S‐(CH₂)₃‐NEt₃]Cl‐ZnCl₂ (molar fraction of ZnCl₂ (x) was 0.67) was a good catalyst for the reaction. The conversion of PET was 100%, and the yields of DBTP and EG were 95.3% and 95.7% at 205°C for 8 h, respectively. The reusability of IL was good and after it was used seven times, PET conversion and the yields of DBTP and EG did not significantly decrease. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1840–1844, 2013     

Effect of ionic liquids on the structural,thermal, and in vitro degradation properties of poly(ε‐caprolactone) synthesized in the presence of Candida antarctica lipase B

The study provides detailed information on the differences in the structural, thermal and degradation properties of poly(ε‐caprolactone) synthesized in two different ionic liquids, 1‐butyl‐3‐methylimidazolium hexafluorophosphate [bmim][PF₆] and 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide [bmim][NTf₂], regarding its further usage in the pharmaceutical field. The polymer structure confirms the presence of both linear polymer chains with end‐functional hydroxyl groups allowing covalent coupling of the therapeutic agents, and cyclic macromolecules, both affecting the degree of crystallinity of polymer. The highest macrocyclic content (64%) after 7 days of polymerization at 80 °C was observed for [bmim][NTf₂]. For [bmim][PF₆], the macrocyclic content value was not dependent on the reaction time and remained at a similar level (10–14% at 80 °C). The results of degradation test revealed that hydrolytic degradation of ester bonds is more pronounced for PCLs synthesized in [bmim][NTf₂], due to their lower degree of crystallinity compared with PCLs obtained in [bmim][PF₆]. A high purity, low polydispersity index of the obtained polymers and high yield of the process (ca., 90%) indicate that ionic liquids seem to be promising solvents for the synthesis of biomedical polymers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43728.     

Fatty acid methyl ester heterogeneous self‐metathesis in hydrophobic green solvent: Mass transfer limitations,catalyst recyclability,and stability

The role of room‐temperature ionic liquids (RTILs), [bmim][PF₆] and [bmim][Tf₂N], as reaction media regarding the catalytic activity and stability of methyltrioxorhenium (MTO) supported on ZnCl₂‐modified mesoporous Al₂O₃ has been studied for self‐metathesis of a functionalized olefin, methyl oleate. The humidity influence on the catalytic activity was probed. The catalyst recycling ability and the kinetics of the metathesis reaction using these RTILs were also investigated. It was found that the MTO‐based catalyst was efficient in viscous hydrophobic RTIL solvents. However, their high viscosity was found to increase the mass transfer limitations thus somewhat impacting the reaction kinetics. Nevertheless, better catalyst stability was reached allowing its possible recycling when used in RTIL media.     

Attapulgite‐supported aluminum oxide hydroxide catalyst for synthesis of poly(ethylene terephthalate)

A novel nanocomposite catalyst was prepared from immobilization of aluminum oxide hydroxide onto the attapulgite. Characterizations with scanning electron microscopy (SEM) and wide angle X‐ray diffraction (XRD) of the as‐prepared catalyst revealed that AlO(OH) nanoparticles were distributed on the attapulgite. Thermogravimetric analysis‐infrared spectrometry (TGA‐IR) of the mixture prepared by mixing of bishydroxy ethylene terephthalate (BHET) and the catalyst indicated that attapulgite‐supported aluminum oxide hydroxide catalyst can catalyze BHET polycondensation under the applied conditions. A kinetic model for determining the activation energy has been applied to evaluate the catalyst activity. The catalyst activity was examined through comparative experiments, and the results showed that the new catalyst exhibited higher activity for BHET polycondensation under identical reaction conditions, and the viscosity‐average molecular weight of poly(ethylene terephthalate) (PET) product obtained was increased about 2000 g/mol. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermodynamic properties of 1‐ETHYL‐3‐methylimidazolium methanesulphonate with aromatic sulphur,nitrogen compounds at T = 298.15–323.15 K and P = 1 bar

This work investigates the ability of 1‐ethyl‐3‐methylimidazolium methanesulphate ([EMIM][MeSO₃]) as a green and tuneable solvent for denitrification and desulphurisation studies. Experimental density, surface tension and refractive index data have been measured for the following systems: [EMIM][MeSO₃] (1) + pyridine (2), [EMIM][MeSO₃] (1) + pyrrole (2), [EMIM][MeSO₃] (1) + quinoline (2), [EMIM][MeSO₃] (1) + indoline (2), [EMIM][MeSO₃] (1) + thiophene (2) and [EMIM][MeSO₃] (1) + water (2) over the entire mole fraction of [EMIM][MeSO₃] at T = 298.15–323.15 K and P = 1 bar. Further from experimental density, surface tension and refractive index, coefficient of thermal expansivity, excess molar volume, deviation of surface tension and refractive index deviation were also calculated. It was found that the heteroaromatic nitrogen/sulphur compounds are completely miscible in [EMIM][MeSO₃]. The surface tension values were found to increase while the refractive index decreases with increasing mole fraction of [EMIM][MeSO₃]. The experimental values for surface tension increased in the order: pyridine > thiophene > pyrrole > indoline > quinoline > water and for refractive index: pyridine > pyrrole > indoline > quinoline > thiophene > water. It was found that the composition of [EMIM][MeSO₃] has a greater influence than temperature in deciding the surface, optical and thermodynamic properties for similar molecular interaction such as IL–thiophene and IL–pyrrole than dissimilar molecules such as IL–water. Further quantum chemical‐based COSMO‐RS tool was used to estimate the activity coefficient at different composition. © 2012 Canadian Society for Chemical Engineering     

Optimization of phthalic/maleic anhydride‐endcapped PET oligomers using response surface method

Poly(ethylene terephthalate) (PET) from off‐grades of industrial manufacturers was partially and thoroughly depolymerized in order to synthesize PET oligomers and bis(hydroxyethyl) terephthalate (BHET), respectively. Design of experiments and analysis of variance (ANOVA) were applied for optimization of samples. Effects of reaction time, volume of glycol, catalyst concentrations, and particle size of off‐grade PET were investigated. The optimal conditions to synthesize PET oligomers (3–8 repeating units) were glycol/PET molar ratio of 1, a weight ratio (catalyst to PET) of 0.5 wt%, using granule‐shape. On the other hand, a reaction time of 180 min, a weight ratio (catalyst to PET) of 0.25 wt%, and glycol/PET molar ratio of 5 were obtained as the suitable conditions of BHET production. Then, endcapped PET oligomers, as a compatibilizer for preparing PET nanocomposites, were produced via reaction between maleic anhydride/phthalic anhydride (MA/PhA) composition. The combination of reaction time of 106 min and PhA/MA molar ratio of 0.85 produced the best results based on d‐spacing and peak shift of nanocomposite samples. Moreover, the reaction of MA and BHET from glycolyzation of PET was successfully performed at 160°C and 190°C for 8 h. The optimum conditions were compared with a synthesized PET. POLYM. ENG. SCI., 54:417–429, 2014. © 2013 Society of Plastics Engineers     

Effect of γ‐irradiation on glycolysis of PET waste and preparation of ecofriendly coatings using bio‐based and recycled materials

Recycling of postconsumer poly (ethylene terephthalate) (PET) is a worldwide concern due to large increasing volume of these materials produced by society. In the present study, we report the effect of gamma irradiation on degradation of PET and its subsequent effect on glycolysis by using excess ethylene glycol (EG). The results as analyzed by molecular weight determination showed that extent of depolymerization of PET were dose dependent. The doses of 30, 50, 70, and 100 kGy resulted in decrease in the molecular weight by about 15%, 25%, 30%, and 40% respectively. The irradiated waste PET samples were further subjected to glycolysis using EG by conventional and microwave method which resulted in increased yield of monomeric product, bis (2‐hydroxyethylterephthalate) (BHET). The recycled material, BHET, was then used in combination with bio‐based monomers to prepare a new eco‐friendly polyester polyol which was analyzed for hydroxyl, saponification, acid value and further characterized by FTIR, ¹HNMR, and GPC techniques for molecular weight determination. Polyurethane coatings were prepared from the polyester polyol and various commercial polyisocyanate curing agents. The coated films were evaluated for their performance properties. Thermal properties of coatings were investigated by differential scanning calorimetry and thermogravimetric analysis. POLYM. ENG. SCI., 55:2653–2660, 2015. © 2015 Society of Plastics Engineers     

Ring‐opening polymerization of cyclohexene oxide by recyclable scandium triflate in room temperature ionic liquid

In this article, we provide a concept of a two‐phase polymerization system consisting of immiscible monomer and room temperature ionic liquid (IL). The catalyst is immobilized in the IL phase where polymerization takes place. The produced polymer is extracted by the monomer, and the remaining IL phase is catalytically active for more polymerizations. Thus, common volatile organic solvents are no longer needed. Ring‐opening polymerization of cyclohexene oxide (CHO) in 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate IL ([bmim][BF₄]) using scandium triflate [Sc(OTf)₃] catalyst serves as a realistic example of such concept. The yield of polyCHO in [bmim][BF₄] is higher than that in bulk. IL containing Sc(OTf)₃ can be used for at least three times. A circulatory polymerization process is carried out with added catalyst to keep a relatively high yield in following circulation processes. The assignments of proton signals of polyCHO in ¹H NMR are discussed in detail. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Kinetics of polycondensation and copolycondensation of Bis(3‐hydroxypropyl terephthalate) and Bis(2‐hydroxyethyl terephthalate)

The kinetics of polycondensation and copolycondensation reactions of bis(3‐hydroxypropyl) terephthalate (BHPT) and bis(2‐hydroxyethyl) terephthalate (BHET) as monomers were investigated at 270°C, in the presence of titanium tetrabutoxide (TBT) as a catalyst. BHPT was prepared by ester interchange reaction of dimethyl terephthalate (DMT) and 1,3‐propanediol (PD). Applying second‐order kinetics for polycondensation, the rate constants of polycondensation of BHPT and BHET, k₁₁ and k₂₂, were calculated as 3.975 and 2.055 min⁻¹, respectively. The rate constants of cross‐reactions in the copolycondensation of BHPT and BHET, k₁₂ and k₂₁, were obtained by using the results obtained from a proton nuclear magnetic resonance spectroscopy. The rate constants during the copolycondensation of BHPT and BHET at 270°C decreased in the order k₁₁ > k₁₂ > k₂₂ > k₂₁, indicating the block nature of the copolycondensation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 693–698, 2000     

Recycling of waste poly(ethylene terephthalate) into flame‐retardant rigid polyurethane foams

Waste poly(ethylene terephthalate) (PET) textiles were effectively chemical recycling into flame‐retardant rigid polyurethane foams (PUFs). The PET textile wastes were glycolytically depolymerized to bis(2‐hydroxyethyl) terephthalate (BHET) by excess ethylene glycol as depolymerizing agent and zinc acetate dihydrate as catalyst. The PUFs were produced from BHET and polymeric methane diphenyl diisocyanate. The structures of BHET and PUFs were identified by FTIR spectra. The limiting oxygen index (LOI) of the PUFs (≥23.27%) was higher than that of common PUFs (16–18%), because the aromatic substituent in the depolymerized products improved the flame retardance. To improve the LOI of the PUFs, dimethyl methylphosphonate doped PUFs (DMMP‐PUFs) were produced. The LOI of DMMP‐PUFs was approached to 27.69% with the increasing of the doped DMMP. The influences of the flame retardant on the foams density, porosity, and compression properties were studied. Furthermore, the influences of foaming agent, catalyst, and flame retardant on the flame retardation were also investigated. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40857.     

Ethylene/1‐octadecene copolymerization using [η5:η1‐C5Me4‐4‐R1‐6‐R‐C6H2O]TiCl2 catalysts

Copolymerization of ethylene with 1‐octadecene was studied using [η⁵:η¹‐C₅Me₄‐4‐R₁‐6‐R‐C₆H₂O]TiCl₂ [R₁ = ^tBu (1), H (2, 3, 4); R = ^tBu (1, 2), Me (3), Ph (4)] as catalysts in the presence of Al(i‐Bu)₃ and [Ph₃C][B(C₆F₅)₄]. The effect of the concentration of comonomer in the feed and Al/Ti molar ratio on the catalytic activity and molecular weight of the resultant copolymer were investigated. The substituents on the phenyl ring of the ligand affect considerably both the catalytic activity and comonomer incorporation. The 1 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system exhibits the highest catalytic activity and produces copolymers with the highest molecular weight, while the 2 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system gives copolymers with the highest comonomer incorporation under similar conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of a novel pH‐sensitive polyurethane–alginate blend with poly(ethylene terephthalate) waste for the oral delivery of protein

With the aim of using poly(ethylene terephthalate) (PET) waste for the synthesis of a value added product, we prepared polyurethane (PU) from bishydrohxyethylene terephthalate (BHET), a byproduct obtained from the glycolysis of PET. Biodegradable, water‐swelling PU was synthesized by the reaction of BHET, hexamethylene diisocyanate, and poly(ethylene glycol) (PEG). Both BHET and PU were characterized by Fourier transform infrared spectroscopy, and the formation of PU was further confirmed by NMR analysis. The swelling behavior of PU in water was examined in terms of the various molecular weights of PEG. Semi‐interpenetrating network beads of PU and sodium alginate were prepared with calcium chloride (CaCl₂) as a crosslinker to attain a pH sensitivity for successful oral protein/drug delivery. Bovine serum albumin (BSA) was used as a model protein. The pH‐responsive swelling behavior and protein (BSA) release kinetics in different pH media corresponding to the gastrointestinal tract (pH 1.2 and 7.4) were investigated. The degree of swelling in the case of the PU–alginate beads at pH 1.2 was found to be at a minimum, whereas the degree of swelling was significantly elevated (1080%) at pH 7.4. This substantiated the pH sensitivity of the polymeric beads with a minimum loss of encapsulated protein in the stomach and the almost complete release of encapsulated protein in the intestine. This revealed good opportunities for oral protein/drug delivery with a polymer derived from waste PET. Moreover, the fungal biodegradation study confirmed its compatibility with the ecological system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40650.     

Crystallization kinetics of poly(1,4‐butylene‐co‐ethylene terephthalate)

The crystallization kinetics of poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and their copolymers poly(1,4‐butylene‐co‐ethylene terephthalate) (PBET) containing 70/30, 65/35 and 60/40 molar ratios of 1,4‐butanediol/ethylene glycol were investigated using differential scanning calorimetry (DSC) at crystallization temperatures (T_c) which were 35–90 °C below equilibrium melting temperature . Although these copolymers contain both monomers in high proportion, DSC data revealed for copolymer crystallization behaviour. The reason for such copolymers being able to crystallize could be due to the similar chemical structures of 1,4‐butanediol and ethylene glycol. DSC results for isothermal crystallization revealed that random copolymers had a lower degree of crystallinity and lower crystallite growth rate than those of homopolymers. DSC heating scans, after completion of isothermal crystallization, showed triple melting endotherms for all these polyesters, similar to those of other polymers as reported in the literature. The crystallization isotherms followed the Avrami equation with an exponent n of 2–2.5 for PET and 2.5–3.0 for PBT and PBETs. Analyses of the Lauritzen–Hoffman equation for DSC isothermal crystallization data revealed that PBT and PET had higher growth rate constant G_o, and nucleation constant K_g than those of PBET copolymers. © 2001 Society of Chemical Industry     

Structural investigations of poly(ethylene terephthalate)‐graft‐polystyrene copolymer films

Structural investigations of poly(ethylene terephthalate)‐graft‐polystyrene (PET‐g‐PS) films prepared by radiation‐induced grafting of styrene onto commercial poly(ethylene terephthalate) (PET) films were carried out by FTIR, X‐ray diffraction (XRD), and differential scanning calorimetry (DSC). The variation in the degree of crystallinity and the thermal characteristics of PET films was correlated with the amount of polystyrene grafted therein (i.e., the degree of grafting). The heat of melting was found to be a function of PET crystalline fraction in the grafted films. The grafting is found to take place by incorporation of amorphous polystyrene grafts in the entire noncrystalline (amorphous) region of the PET films and at the surface of the crystallites. This results in a decrease in the degree of crystallinity with the increase in the degree of grafting, attributed to the dilution of PET crystalline structure with the amorphous polystyrene, without almost any disruption in the inherent crystallinity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1949–1955, 2002; DOI 10.1002/app.10515     

Effect of the copolycondensation temperature on the reactivities of bis(3‐hydroxypropyl)terephthalate and bis(2‐hydroxyethyl)terephthalate

The rate constants of cross reactions in the copolycondensation of bis(3‐hydroxypropyl)terephthalate (BHPT) and bis(2‐hydroxyethyl)terephthalate (BHET), k₁₂ and k₂₁, were determined with the results obtained from ¹H NMR spectroscopy analysis. BHPT and BHET were polymerized and copolymerized at 260, 270, and 280°C with titanium tetrabutoxide as a catalyst. With the adoption of second‐order kinetics to the polycondensation, k₁₁ and k₂₂ were calculated. The monomer reactivity ratios of BHPT were much larger than those of BHET, indicating the block nature of the copolycondensation, but the difference between the reactivity ratios was lowest at the highest polycondensation temperature of 280°C. This indicated that the probability of randomization was increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1890–1895, 2003     

Melt polymerization of copoly(ethylene terephthalate–imide)s and thermal properties

Copoly(ethylene terephthalate–imide)s (PETI) were prepared by melt polycondensation of bis(2-hydroxyethyl)terephthalate (BHET) and imide containing oligomer, i.e., 4,4′-bis[(4-carbo-2-hydroxyethoxy)phthalimido]diphenylmethane(BHEI). The apparent rate of poly-condensation reaction was faster than that of homo poly(ethylene terephthalate) (PET) due to the presence of imide units. The PETI copolymers with up to 10 mol % of BHEI unit in the copolymer showed about the same molecular weight and carboxyl end group content as homo PET prepared under similar reaction conditions. The increase in T_g of copolymer was more dependent on molar substitution of BHEI than on substitution of BHEN, reaching 91°C with 8 mol % BHEI units in the copolymer from T_g = 78.9°C of homo PET. In the case of PETN copolymer, 32 mol % of bis(2-Hydroxyethyl)naphthalate (BHEN) units gave T_g of 90°C. The maximum decomposition temperature of PETI copolymer was about the same as that of homo PET by TGA analysis. The char yield at 800°C was higher than that of homo PET. © 1996 John Wiley & Sons, Inc.     

Chain extension of recycled poly(ethylene terephthalate) with 2,2′‐(1,4‐phenylene)bis(2‐oxazoline)

The present work provides improved recycled high molecular weight poly(ethylene terephthalate) (PET) by chain extension using 2,2′‐(1,4‐phenylene)bis(2‐oxazoline) (PBO) as the chain extender. PBO is a very reactive compound toward macromolecules containing carboxyl end groups but not hydroxyl end groups. In the case of PET, where both species are present, for even better results, phthalic anhydride (PA) was added in the initial sample, before the addition of PBO. With this technique, we succeeded in increasing the carboxyl groups by reacting PA with the hydroxyl terminals of the starting polymer. From this modification of the initial PET sample, PBO was proved an even more effective chain extender. So, starting from a recycled PET with intrinsic viscosity [η] = 0.78, which would be [η] = 0.69 after the aforementioned treatment without a chain extender or M̄_n = 19,800, we prepared a PET grade having [η] = 0.85 or M̄_n = 25,600 within about 5 min. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2206–2211, 2000     

In‐situ synthesis of poly(ethylene terephthalate)/clay nanocomposites using TiO2/SiO2 sol‐intercalated montmorillonite as polycondensation catalyst

A novel organic montmorillonite, which could act as both polycondensation catalyst of poly(ethylene terephthalate) (PET) and filler of PET/clay nanocomposites, was prepared. Original montmorillonite was first treated with different amounts of poly(vinylpyrrolidone) (PVP), and then intercalated by TiO₂/SiO₂ sol to gain polycondensation catalytic activity. The acquired clay possessed excellent thermal stability and would not degrade during the polycondensation step. PET/clay nanocomposites were prepared via in‐situ polymerization using the organo‐clay as polycondensation catalysts. The morphologies of the nanocomposites were characterized by X‐ray diffraction and transmission electron microscope. The results indicated that the amount of PVP and TiO₂/SiO₂ sol strongly affected the dispersion state of the clay, and finally, partially exfoliated PET/clay nanocomposites were obtained. The nanocomposites had better properties than pure PET due to the incorporation of the delaminated clay layers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers