No abstract

Response surface methodology (RSM) was used for predicting the optimal condition of glycolysis time and temperature in the recycling of PET scrap. Central composite rotatable design (CCRD) for two variables at four levels was chosen as the experimental design. The data obtained from measurement of properties were fitted as a two variable second-order equation and were plotted as 3D surface plots using programme developed in MATLAB v.5. Analysis of variance (ANOVA) was used to evaluate the validity of model. The optimum operating conditions for glycolysis time and temperature were 6.5 h and 180• C, respectively. Under these optimal conditions, the hydroxyl value and glycolysis conversion percentage was 38.14 mgKOH/g and 95%, respectively, at the 0.97 desirability level, whereas the acid value and number average molecular weight (M n ) at the same desirability level were 12.2 mgKOH/g and 695 g/mol, respectively.

Postconsumer poly(ethylene terephthalate) waste bottles were glycolyzed as precursors of unsaturated polyester resin (UPR) and their montmorillonite (MMT)-filled nanocomposites. The glycolysis product (hydroxyl-terminated oligomers) was converted into UPR with various acid contents. These resins were miscible with styrene and could be cured with peroxide initiators to produce thermosetting unsaturated polyester (UP). Nanocomposites composed of UP matrix and organically modified clay were prepared by in situ polymerization. These were characterized for thermal and dynamic mechanical properties. Transmission electron microscopy was also used to study the morphology at different length scales and showed the nanocomposites to be compromised of a random dispersion of intercalated/exfoliated aggregates throughout the matrix. With an increase in unsaturated acid content (for a fixed content of clay), the value of storage modulus varied from 2737 to 4423 MPa. The glass-transition temperatures of these nanocomposites ranged from 54 to 78 C, and the crosslink density varied from 3.70 Â 10 5 to 5.72 Â 10 5 mol/m 3 . The X-ray diffraction (XRD) of modified MMT exhibited a peak that vanished completely in the polymer nanocomposites. Thus, the XRD results apparently indicated a distortion of the platy layers of nanofiller in the UP nanocomposites. The nanocomposites showed higher modulus values (2737-4423 MPa) compared to the pristine polymer (2693 MPa). From thermogravimetric analysis, all of the nanocomposites were stable up to 200 C and showed a two-stage degradation.

Saturated polyester resin, derived from the glycolysis of polyethyleneterephthalate (PET) was examined as an effective way for PET recycling. The glycolyzed PET (GPET) was reacted with the mixture of phthalic anhydride and ethylene glycol (EG) with varied compositions and their reaction kinetic were studied. During polyesterification of GPET, acid and EG, the parameters like degree of polymerization (DP n), extent of reaction (p) acid value and hydroxyl values were measured. The thermomechanical properties and the morphologies of the saturated polyester nanocomposites were examined by using a differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), wide angle X-ray diffraction (WAXRD) and transmission electron spectroscopy (TEM). There were significant differences observed in T g , T m and T c before and after addition of GPET and clay content. Nanocomposites with lower content of organoclay showed intercalated morphology while by increasing the amount of organoclay, the exfoliated morphology was more prevalent. Water vapour transmission (WVT) was determined for saturated polyester nanocomposite sheets according to ASTM E96-80.

Waste polyethylene terephthalate (PET) is glycolyzed along with virgin PET. A higher proportion of virgin PET in the mixture has the ability to consume more glycols during glycolysis. This gives rise to a glycolyzed PET (GPET1), which contains a lesser amount of free glycol and shows the highest hydroxyl value. During polyesterification of the polyester diol (glycolyzed PET) with maleic acid, the degree of polymerization (DPn), extent of reaction and acid value is observed to be increasing with an increase in the virgin PET content in the mixture. This is believed to be due to the increasing presence of BHET (bis hydroxy ethylene terephthalate) in the glycolyzed PET.