Synthesis and characterization of terephthalamides from poly(ethylene terephthalate) waste

Poly(ethylene terephthalate) (PET) waste flakes (blow‐molded‐grade industrial waste) were degraded with aqueous methylamine and ammonia at room temperature in the presence and absence of quaternary ammonium salt as a catalyst for various times. The catalyst reduced the time required for the degradation of the PET waste. The degraded products were analyzed with IR, nuclear magnetic resonance, mass spectrometry, and differential thermal analysis and were characterized as N,N′‐dimethylterephthalamide and terephthalamide in the case of methylamine and ammonia, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1515–1528, 2005     

A novel route of synthesis,characterization of terephthalic dihydrazide from polyethylene terephthalate waste and it's application in PVC compounding as plasticizer

The degradation of polyethylene terephthalate (PET) waste by making use of hydrazine monohydrate was investigated at ambient temperature and pressure. The aminolysed end products obtained were characterized with chemical tests and spectroscopic techniques namely IR, UV‐visible spectroscopy and NMR, and the differential scanning calorimeter (DSC). The end product was characterized as terephthalic dihydrazide (TPD) and further used in PVC compounding as secondary plasticizer. The hardness, tensile strength, elongation at break, thermal stability, and compatibility of the PVC sheet were studied and concluded that the aminolysed product may find potential application as secondary plasticizer in PVC formulations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Glycolysis of polyethylene terephthalate waste fibers

Glycolysis of polyethylene terephthalate waste fibers was carried out using excess ethylene glycol in the presence of different simple chemicals, namely, glacial acetic acid, lithium hydroxide, sodium sulfate, and potassium sulfate. Good yields (> 60%) of the monomer bis(2‐hydroxyethylene terephthalate) were obtained using these chemicals as depolymerization catalysts. The purified monomer was characterized by elemental analysis, melting point, IR spectroscopy, and nuclear magnetic resonance. The qualitative and quantitative yields of the monomer obtained using these catalysts are most comparable with the conventionally used heavy metal catalysts such as zinc acetate and lead acetate. The chemicals used, being cheap and comparatively less harmful to the environment, offer further advantages in chemical recycling of polyester waste fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 513–517, 2005     

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.     

Thermal characterization of n‐alkyl maleate‐styrene‐allyl propionate terpolymers

Thermal characterization of maleic anhydride‐styrene‐allyl propionate (MA‐St‐AP) terpolymer and its ester derivatives named as n‐alkyl maleate and shown as nPr MA‐St‐AP, nBu MA‐St‐AP, nPn MA‐St‐AP, and nBz MA‐St‐AP was carried out. The thermal characterization was performed using thermal analysis techniques such as TGA, DTA, DSC, and TMA. Different results were observed between the original terpolymer and its ester derivatives. Thermal stabilities of the terpolymer and its ester derivatives were compared by using various measurements plotted as TGA, DTA, DSC, and TMA curves. The increase in the alcohols' carbon numbers added to the original terpolymer results in ester derivatives with different thermal stability behavior. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 600–604, 2007     

Using ionic liquid catalyst for conversion of waste polyethylene terephthalate and soybean oil to polyester polyol

An imidazolium ionic liquid was synthesized, characterized and used as a catalyst for conversion of polyethylene terephthalate (PET) and soybean oil to polyester polyol (PE polyol). The degradation of PET waste was carried out using glycerol and low cost soybean oil that resulted in the formation of PE polyols. Formed PE polyols were characterized using Fourier transform infrared (FT‐IR) and mass spectra method, thermo gravimetric and differential thermal analysis and gel permeation chromatoghraphy. The first step in the overall process is proposed to be the transesterification of soybean oil with glycerol to form monoglyceride or/and diglyceride of soybean oil fatty acids. In the second step, the obtained glycerides can react with PET to form PE polyol. Both steps could be combined in one process and acidic catalyzed by an ionic liquid. Ionic liquid can be used as active catalyst and show a high reusability. The influence of some factors such as amount of glycerol used in transesterification of soybean oil with glycerol, PET degradation time, and temperature on PET conversion were investigated to find the suitable conditions for the process. Under suggested optimum parameters (mass ratio of soybean oil to glycerol of 2:1, a time of 8 h and a temperature of 180 °C for PET degradation), a PET conversion of 87.3% was reached. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43920.     

Effect of fused deposition modeling process parameters on the mechanical properties of recycled polyethylene terephthalate parts

Fused deposition modeling (FDM) filaments made of recycled materials are desirable for environmentally friendly and sustainable manufacturing of prototypes and load-bearing components in many applications. We investigate the effect of FDM process parameters on the mechanical properties of 3D-printed parts made of recycled polyethylene terephthalate (rPET) filaments. Increasing the nozzle temperature from 230°C to 260°C improves the strength of the specimens by 100%. Using a raster orientation parallel to the loading direction improves the ductility by more an order of magnitude. Specimen orientation and infill ratio also influence the mechanical properties. The temperature and the orientation effects are related to the quality of fusion between the printed lines. A modified Gibson-Ashby model correctly predicts the strength as a function of the infill ratio. Through the optimization of process parameters, the mechanical strength of 3D-printed rPET structures can reach that of injection-molded PET, making FDM a suitable manufacturing technique for load-bearing applications.     

Spinning fibers from poly(ethylene terephthalate) bottle‐grade waste

Poly(ethylene terephthalate) bottle‐grade (BG) waste was converted into spinnable chips and spun on a laboratory‐scale melt‐spinning apparatus into filaments. Virgin fiber‐grade (FG) polyester chips were blended with BG waste during melt spinning so that the influence of blending on the fiber properties could be studied. Subsequently, the scaling‐up of the process was carried out in a polyester recycling plant so that staple fibers could be obtained. In this part of the study, the spinning of blends of BG waste and FG waste was carried out. The BG waste was found to be superior feed stock for melt processing. Fibers with unique properties were obtained from the BG waste. Staple fibers obtained by the blending of FG and BG waste showed properties different from those of fibers spun from BG waste alone. This study also showed that using blends of BG and FG waste could improve the melt processing and staple‐fiber properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3536–3545, 2003     

Water‐blown polyurethane/polyisocyanurate foams made from recycled polyethylene terephthalate and liquefied wood‐based polyester polyol

Depolymerized polyethylene terephthalate and liquefied wood polyesters can be used as a polyol for the production of polyurethane/polyisocyanurate foams. In this research, liquefied wood was synthesized by using a combination of diethylene glycol and glycerol and due to the possibility of using glycerol that is a by‐product in biodiesel production, our goal was to use as much glycerol in the liquefaction reagent as possible. We determined the properties of the polyols, properties of produced foams, and explained their correlation. Greater amount of glycerol in the liquefaction reagent resulted in higher OH number, molecular weight, functionality, and viscosity of the polyol, as well as in longer cream time and tack free time in foam preparation. Glass transition temperature, density, and water absorption of the foam increased with increasing amount of glycerol in liquefied wood. Compressive stress increased up to 30% of the glycerol in the reagent and then reduced, while thermal conductivity was not affected. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41522.     

Structure and antimicrobial activity relationship of quaternary N‐alkyl chitosan derivatives against some plant pathogens

In the present work, quaternary chitosans as water‐soluble compounds were prepared based on three‐step process. Schiff bases were firstly synthesized by the reaction between the amino groups of chitosan with aliphatic aldehydes followed by a reduction with sodium borohydride (NaBH₄) to form N‐(alkyl) chitosans. N,N,N‐(dimethyl alkyl) chitosans were then obtained by a reaction of chitosan containing N‐butyl, N‐pentyl, N‐hexyl, N‐heptyl, and N‐octyl substituents with methyl iodide. The compounds were characterized using IR and NMR spectroscopy. Subsequent experiments were conducted to test their antimicrobial activities against the most economic plant pathogenic bacteria of crown gall disease Agrobacterium tumefaciens, soft mold disease Erwinia carotovora, fungi of grey mold Botrytis cinerea, root rot disease Fusarium oxysporum, and damping off disease Pythium debaryanum. Quaternary chitosans enhanced the antibacterial activity and N,N,N‐(dimethyl pentyl) chitosan was the most active one with Minimum Inhibitory Concentration (MIC) of 750 and 1225 mg/L against A. tumefaciens and E. carotovora, respectively. All quaternized chitosans gave stronger antifungal activities than chitosan where N,N,N‐(dimethyl pentyl) chitosan and N,N,N‐(dimethyl octyl) chitosan were significantly the highest in mycelial growth inhibiation against B. cinerea (EC₅₀ = 908 and 383 mg/L, respectively), F. oxysporum (EC₅₀ = 871 and 812 mg/L, respectively), and P. debaryanum (EC₅₀ = 624 and 440 mg/L, respectively). In addition, spore germination of B. cinerea and F. oxysporum was significantly affected with the compounds at the tested concentrations and the inhibition activity was increased with an increase in the chain length of the alkyl substituent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Solid‐state hydrolysis of postconsumer polyethylene terephthalate after plasma treatment

Plasma treatments were applied on the surface of postconsumer polyethylene terephthalate (PET) bottles to increase their wettability and hasten the subsequent hydrolysis process. Sixty‐four treatments were tested by varying plasma composition (oxygen and air), power (25–130 W), pressure (50–200 mTorr), and time (1 and 5 min). The best treatment was the one applied in air plasma at 130 W and 50 mTorr for 5 min, as it provided the lowest contact angle, 9.4°. Samples of PET before and after the optimized plasma condition were subjected to hydrolysis at 205°C. Although the treatment changed only a thin surface layer, its influence was evident up to relatively high conversion rates, as the treated samples presented more than 40% higher conversion rates than the untreated ones after 2 h of reaction. Infrared spectroscopy showed that the terephthalic acid obtained from 99% of depolymerization was similar to the commercial product used in PET synthesis. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Reactive‐extrusion route for the closed‐loop recycling of poly(ethylene terephthalate)

The effectiveness of the reactive extrusion technique was investigated for poly(ethylene terephthalate) to promote the concept of closed‐loop recycling, that is, the reuse of waste material in the initial application. More specifically, a chain‐extender system, consisting of pyromellitic dianhydride, polyol, and a catalyst, was employed, and its efficiency regarding the improvement of the recyclate quality was evaluated. Accordingly, rheological and thermal characterizations were performed and used as criteria of the modification induced in the polymer molecular structure during processing due to the counteracting degradation and chain‐extension reactions. In particular, the molecular weight, related to intrinsic viscosity and melt flow rate measurements, of modified poly(ethylene terephthalate) samples was found to increase with the additive content. Simultaneously, a decrease in the crystallinity was observed, attributed to the branching effect of the chain extender, which restricted the ability of the macromolecules to organize in the crystal structure. Beyond a critical concentration of the additive system, the molecular weight of the treated samples started to decrease again, and this was accompanied by a small increase in the crystallinity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1671–1678, 2007     

废纸苯酚液化及生成树脂的结构表征

首先在一定液化工艺条件下,对废纸进行了液化处理,而后对液化后的产物分别进行了傅立叶转换红外光谱(FTIR)以及电子扫描电镜(SEM)的测定分析,并对其生成树脂进行差热(DTA)分析。FTIR的结果表明,液化废纸结构发生了明显变化,而且出现了化学组分中的最基本结构单元,表明苯酚液化处理使废纸发生了降解、酚化等化学反应。SEM测定结果表明,液化后的废纸液化中依然含有废纸的未完全液化的微小废纸组织碎片,废纸纤维结构被进一步破坏。对废纸液化树脂差热(DTA)分析的结果表明,废纸液化物树脂峰顶温度低于传统酚醛树脂;废纸液化物树脂和传统酚醛树脂一样,顶峰温度随着升温速率提高。     

Studies on Thermal Degradation of Cellulosic Fibers Treated with Flame Retardants

Hemp fabric, one of the most flammable materials, was treated with compounds containing different kinds of elements that contribute to flame retardation. For a study of flame retardation from the standpoint of thermal degradation, the samples were subjected to thermogravimetry (TG) and differential thermal analysis (DTA) in air from ambient temperature to 600℃. The apparent activation energy (Ea) is evaluated by Broido's method at different stages of thermal degradation to observe the variation of Ea in the process of thermal degradation. Flame retardation of samples was determined by limiting oxygen index (LOI) to find the effects of the different compounds on flammability and the thermal degradation of the hemp fabric. The composition of the chars was studied by the IR spectra to obtain information concerning the thermal degradation mechanism. Compared with flammable hemp, the hemp fabric treated with flame retardants showed a higher LOI but lower Ea and decomposition temperatures, which indicated that some compounds make the hemp fabric decompose at lower temperatures, resulting in less flammable products.     

利用废感光胶片合成DOTP的工艺研究

利用废感光胶片回收得到对苯二甲酸二(2 乙基己)酯(DOTP)。在单丁基氧化锡催化作用下,将废感光胶片在170～220℃降解,最佳温度为190℃,然后与2 乙基己醇反应置换出乙二醇,并不断蒸出乙二醇,蒸出过量2 乙基己醇后可得到DOTP,所得产品的酯含量达99%,当单丁基氧化锡催化剂用量为0.25%,2 乙基己醇与废感光胶片的摩尔配比为3.0时,DOTP的回收率可达90%。     

Phase structure and properties of poly(ethylene terephthalate)/high‐density polyethylene based on recycled materials

Blends based on recycled high density polyethylene (R‐HDPE) and recycled poly(ethylene terephthalate) (R‐PET) were made through reactive extrusion. The effects of maleated polyethylene (PE‐g‐MA), triblock copolymer of styrene and ethylene/butylene (SEBS), and 4,4′‐methylenedi(phenyl isocyanate) (MDI) on blend properties were studied. The 2% PE‐g‐MA improved the compatibility of R‐HDPE and R‐PET in all blends toughened by SEBS. For the R‐HDPE/R‐PET (70/30 w/w) blend toughened by SEBS, the dispersed PET domain size was significantly reduced with use of 2% PE‐g‐MA, and the impact strength of the resultant blend doubled. For blends with R‐PET matrix, all strengths were improved by adding MDI through extending the PET molecular chains. The crystalline behaviors of R‐HDPE and R‐PET in one‐phase rich systems influenced each other. The addition of PE‐g‐MA and SEBS consistently reduced the crystalline level (χ_c) of either the R‐PET or the R‐HDPE phase and lowered the crystallization peak temperature (T_c) of R‐PET. Further addition of MDI did not influence R‐HDPE crystallization behavior but lowered the χ_c of R‐PET in R‐PET rich blends. The thermal stability of R‐HDPE/R‐PET 70/30 and 50/50 (w/w) blends were improved by chain‐extension when 0.5% MDI was added. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of water‐extended polyester based on recycled poly(ethylene terephthalate)

An unsaturated polyester resin was prepared that was based on the reaction of oligomers obtained from the depolymerization of poly(ethylene terephthalate) waste products, with both maleic anhydride and sebacic acid. The structure of the produced polyester was compared with that prepared from the reaction of dimethyl terephthalate with both maleic anhydride and sebacic acid with IR and NMR spectroscopy. Water‐extended polyester resins were prepared from these two polyesters through curing with styrene in the presence of various amounts of water with benzoyl peroxide as an initiator. The mechanical properties of the prepared water‐extended polyesters, as well as scanning electron microscopy, were investigated. The use of water‐extended polyesters based on recycled poly(ethylene terephthalate) waste for the preparation of decorative art objects and statues was investigated. Therefore, three pharaonic statues representing Tutankhamen, Nefertiti, and a black head of a cat were prepared. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3693–3699, 2003     

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.     

Recycling of waste PET‐bottles using dimethyl sulfoxide and hydrotalcite catalyst

The degradation of PET bottles has been successfully achieved using hydrotalcite as catalyst and dimethyl sulfoxide (DMSO) as solvent. The reaction was carried out at boiling point of DMSO (190°C) and degradation was complete in 10 min. The oligomer (tetramer) obtained was treated with NaOH at room temperature in methanol to get dimethyl terephthalate (DMT) and ethylene glycol (EG). Thus, it is a safe and cleaner process. Oligomer was characterized by MS, 13 C‐NMR, X‐ray diffractometric, and thermogravimetric analysis. DMT and EG were characterized by GC‐MS. DMT was also characterized by FT‐IR. GC‐MS analysis shows that the purity of DMT was 99%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012     

Recycling of PET waste using 3‐amino‐1‐propanol by conventional or microwave irradiation and synthesis of bis‐oxazin there from

There is a growing interest in recycling of post‐consumer poly(ethylene terephthalate) (PET) waste for both environmental and economic reasons. PET in the form of disposable soft drink bottle waste was subjected to depolymerization via aminolysis using excess of 3‐amino‐1‐propanol under soxhlet by conventional heating as well as microwave irradiation using catalyst sodium acetate or potassium sulfate. The product obtained was characterized after purification by using melting point, IR spectroscopy, nuclear magnetic resonance, and differential scanning calorimeter and was found to be bis‐(3‐hydroxy propyl) terephthalamide (BHPTA). The BHPTA thus obtained was subjected to cyclization reaction using thionyl chloride to obtain bis‐oxazin under conditions of ambient temperature. Bis‐oxazin has applications in polymer synthesis as a chain extender or a cross linking agent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013