Alkyd resins derived from glycolized waste poly(ethylene terephthalate)

Progress of research on the bonding-strength improvement of two-layer adhesive-free flexible copper-clad laminates

The arrival of the 5G era has placed high demands on the electronic products. Developing thin, light, and portable electronic products capable of simultaneously improving the transmission rate and reducing the signal delay and transmission loss is necessary to meet such demands. The traditional three-layer, adhesive, flexible copper-clad laminate (3L-FCCL) cannot satisfy these demands because of its adhesive component. The large thickness and poor heat resistance disadvantages of 3L-FCCL can be avoided with a two-layer, adhesive-free, flexible copper-clad laminate (2L-FCCL). However, 2L-FCCL has low bonding strength. This work introduces the selection of conductor materials and insulating base films for flexible copper-clad laminates. Modification studies aimed at increasing the bonding performance of 2L-FCCL are summarized based on three aspects. These modification techniques include the surface treatment of copper foils, modification and surface treatment of polyimide films, and surface treatment of liquid-crystal polymers. Prospects are further provided.

Influence of the Polymerization Modes on the Methacrylic Acid Release from Dental Light-Cured Materials-In Vitro Study

The study focuses on the problem of lowering the pH around a composite filling concerning the polymerization modes and methacrylic acid release, which may affect not only the oral health but also the whole organism. A total of 90 specimens (30 of each: Filtek Bulk Fill, Evetric and Riva LC) were placed in 90 sterile hermetic polyethene containers with saline and incubated at 37 °C. Ten samples of each material were light-cured for 40 s with one of the three curing modes: full power mode (FPM), ramping mode (RM) and pulse mode (PM). The pH and methacrylic acid release evaluation were performed at the following time points: after 2 h and after 3, 7, 21 and 42 days from the specimen preparation. Regardless of light-curing mode, all used materials were characterized by a gradual elevation in methacrylic acid concentration. Only for Filtek Bulk Fill, increased methacrylic acid release was closely associated with lower pH. The choice of the polymerization mode has no significant influence on the methacrylic acid release. However, further research about composite light-curing is necessary to create the procedure algorithm, reducing the local and systemic complications associated with composite fillings.

Preparation of autoxidative water-reducible alkyd resins from waste polyethylene terephthalate

In this paper, the waste polyethylene terephthalate (PET) was glycolysed by trimethylolpropane with zinc acetate as catalyst. The effects of different content glycolysis product of waste PET on the appearance, viscosity, particle size and molecular weight of autoxidative water-reducible alkyd resins and the corresponding film adhesion, flexibility, impact resistance, gloss, hardness and chemical resistance were studied. Meanwhile, experimental results were compared with commercial water-reducible alkyd and water-reducible alkyd without the glycolysis product of waste PET. The results show that the maximum concentration of PET in autoxidative water-reducible alkyd resins can reach 8.5 wt%, and the molecular weight, particle size and viscosity of water-reducible alkyd resin do not change much with the increase of PET concentration. The introduction of PET resulted in the viscosity of water-reducible alkyd resins being greater than that of water-reducible alkyd resin without PET; this is mainly because PET contains harder terephthalic acid monomer units. However, the particle size of water-reducible alkyd resins with waste PET is significantly lower than that of the water-reducible alkyd resin without PET; this is due to PET-free water-reducible alkyd resin containing more pentaerythritol with greater steric hindrance. In addition, the hardness of the water-reducible alkyd resin paint film (PET content is 8.5%) reaches 1H, which is higher than the hardness (HB) of the water-reducible alkyd resin paint film without PET and the commercial alkyd resin paint film, while the physical properties and chemical resistance of the former are comparable to those of the latter two kinds of paint films. Therefore, the use of waste PET in water-borne coatings systems not only reduces the cost of coatings, but also opens up a new market for recycled PET, which may contribute a promising method for management of waste PET.

Depolymerization of poly(ethylene terephthalate) waste with biomass-waste derived recyclable heterogeneous catalyst

Poly(ethylene terephthalate) (PET) is one of the most widely used polymeric materials in chemical industry representing about 13% of the world's production. With the exponentially increasing consumption of plastics combined with its non-biodegradability, the accumulation of plastic waste in the environment rises steeply and its recycling has attracted enormous attention among researchers in recent years. In this present work, we describe bamboo leaf ash (BLA) as a bio-waste derived recyclable heterogeneous catalyst for the depolymerization of waste PET. The prepared catalyst was characterized by FT-IR, XRD, SEM, TEM, EDX, TGA and BET analyses to assess its morphology and composition. Postconsumer PET bottles were shredded and processed with 20 wt% BLA and 16 equivalents of ethylene glycol (EG) at 190 °C for 3.5 h under atmospheric pressure to give recrystallized bis(2-hydroxyethyl) terephthalate (BHET) monomer in 83% yield. The catalyst can be reused for four catalytic cycles and the residual EG was recovered for subsequent catalytic reactions. Excellent activity, cost-free, environmental-friendliness and ease of preparation, handling and reusability of the catalyst with simple work-up procedure are the notable advantages of this protocol.

Thermal and anticorrosion properties of polyurethane coatings derived from recycled polyethylene terephthalate and palm olein-based polyols

Polyols of palm olein/polyethylene terephthalate (PET) were synthesized by means of incorporating recycled PET from waste drinking bottles in different proportions into palm olein alkyd in the presence of ethylene glycol. The polyols were characterized by FTIR, and theirs hydroxyl value (OHV), acid value (AV) and viscosity were determined. The formulation of the polyurethane coating was carried out by dissolving the polyol in mixed solvent of cyclohexanone/tetrahydrofuran (THF) (4 : 1) followed by reacting 1 hydroxyl equivalent of the polyol with 1.2 equivalents of methylene diphenyldiisocyanate and 0.05% dibutyltin dilaurate (DBTDL) catalyst. The coating cured through the cross-linking reactions between hydroxyl and isocyanate groups. The formation of urethane linkages was established by FTIR spectroscopy. The set films were characterized by thermal analysis. To study their anticorrosion properties, polarization measurements and EIS in 3.5% NaCl solution were determined. The coatings displayed good thermal stability and anticorrosion properties which were supported by XRD analysis. The PU7 coating, with the highest proportion of PET (up to 15% w/w), displayed significantly improved thermal stability and anticorrosion properties. It is evident that the performance of the polyurethane (PU) coatings could be enhanced by the incorporation of PET.

Novel Oligo-Ester-Ether-Diol Prepared by Waste Poly(ethylene terephthalate) Glycolysis and Its Use in Preparing Thermally Stable and Flame Retardant Polyurethane Foam

Rigid polyurethane foam (PUF) was successfully prepared from a novel oligo-ester-ether-diol obtained from the glycolysis of waste poly(ethylene terephthalate) (PET) bottles via reaction with diethylene glycol (DEG) in the presence of ZnSO₄·7H₂O. The LC-MS analysis of the oligodiol enabled us to identify 67 chemical homologous structures that were composed of zero to four terephthalate (T) ester units and two to twelve monoethylene glycol (M) ether units. The flame retardant, morphological, compression, and thermal properties of rigid PUFs with and without triphenyl phosphate (TPP) were determined. The Tg values showed that TPP played a role of not only being a flame retardant, but also a plasticizer. PUF with a rather low TPP loading had an excellent flame retardancy and high thermal stability. A loading of 10 wt % TPP not only achieved a UL-94 V-0 rating, but also obtained an LOI value of 21%. Meanwhile, the PUF without a flame retardant did not achieve a UL-94 HB rating; the sample completely burned to the holder clamp and yielded a low LOI value (17%). The fire properties measured with the cone calorimeter were also discussed, and the results further proved that the flame retardancy of the PUF with the addition of TPP was improved significantly. The polymeric material meets the demands of density and compression strength for commercial PUF, as well as the needs of environmental development. The current study may help overcome the drawback of intrinsic high flammability and enlarge the fire safety applications of materials with a high percentage of recycled PET.

Unsaturated polyester nanocomposites based on poly(ethylene terephthalate) waste using different types of nanofillers

The poly(ethylene terephthalate) waste was depolymerized using 1,4-butanediol, and diethylene glycol and the glycolyzed products were used in the preparation of the unsaturated polyester. The composition of the glycolyzed products and the prepared polyester (unsaturated polyester) were investigated in view of their infrared and 1H NMR spectra. Different samples of unsaturated polyester/nanocomposites containing various amounts (1, 3, and 5 wt%) of different nanofillers, namely Nanofil 116, Cloisite 30B, and Laponite RD, were also prepared. The effect of the nanofiller type and content on the morphological structure of the fractured surfaces, thermal, mechanical, and electrical properties was investigated.

PET depolymerisation in supercritical ethanol catalysed by [Bmim][BF4]

Poly(ethylene terephthalate) was depolymerised under supercritical ethanol, 98 wt% of diethylterephthalate was obtained after 45 min, by adding [Bmim][BF₄] as catalyst.

Synthesis and Characterization of Polyurethane Nanocomposites Formulated by Incorporation of Polyols from PET Waste

Polyethylene terephthalate (PET) was depolymerized using trimethylolpropane (TMP) and glycerin as a binary solvent mixture to provide oligomeric polyol for rigid polyurethanes foam formulation. Recyclate containing rigid polyurethane foam nanocomposites were prepared by introducing of different portions (1-5%) of nanoclays namely, NaMMT, 30B, 20A, 15A Cloisites. The parallel effects of recycled polyol and nano clays on mechanical and thermal characteristics of the nanocomposites were investigated. Dispersion of clay nano particles in polymer matrix was characterized by SEM what confirm the exfoliation of nanoparticles. The thermal properties were also studied by TMA and DMA.