Influence of solid-state polycondensation conditions on the intrinsic viscosity of recycled poly(ethylene terephthalate)

This study explores the potential of additive manufacturing (AM) to upcycle industrial waste low‐density polyethylene (LDPE) by investigating the effect of LDPE waste's melt flow index (MFI) on the printability of LDPE/polystyrene (PS) blends via fused deposition modeling (FDM) and the corresponding mechanical properties and fracture behaviors of the printed components. Two industrial LDPE waste grades with MFI values (0.8 and 4 g/10 min) were blended with PS and compatibilized using a styrene–ethylene–butylene–styrene (SEBS) copolymer. The printability of various LDPE/PS blend ratios was evaluated for their mechanical, rheological, thermal, and morphological properties. Based on this analysis, selected blend ratios were used for FDM printing. The mechanical properties and fracture behaviors of the 3D printed LDPE/PS were first assessed. The practical printability of the blends in challenging FDM conditions was then evaluated by fabricating complex, unsupported geometries, such as bridges, overhangs, and thin‐walled cubes. The results revealed that LDPE with a higher MFI showed improved flowability but compromised ductility, while lower MFI improved structural integrity. An MFI of 4 g/10 min was identified as optimal, offering a balance between flowability and strength, enabling successful 3D printing. Adding SEBS compatibilizer showed enhanced interfacial adhesion, improved filament quality, and enhanced printability in bridging and overhang tests. However, these blends exhibited limitations in printing thin‐walled structures as demonstrated by warping and layer delamination, caused by thermal gradients between the extrusion temperature and ambient conditions and uneven shrinkage during cooling. This study demonstrates the feasibility of converting industrial LDPE waste into functional materials for FDM through optimized MFI selection and blend design. The findings provide a pathway to integrate mixed plastic waste into additive manufacturing workflows.

Effect of activated carbon black nanoparticles on solid state polymerization of poly(ethylene terephthalate)

Among the composite manufacturing methods, injection molding has higher time efficiency and improved processability. The production of composites via injection molding requires a pre-process to mix and pelletize the matrix polymer and reinforcement material. Herein, we studied the effect of extrusion process conditions for making pellets on the mechanical and thermal properties provided by injection molding. Polyamide 6 (PA6) was used as the base, and composites were produced by blending carbon fibers and Al2O3 as the filler. To determine the optimum blending ratio, the mechanical properties, thermal conductivity, and melt flow index (MI) were measured at various blending ratios. With this optimum blending ratio, pellets were produced by changing the temperature and RPM conditions, which are major process variables during compounding. Samples were fabricated by applying the same injection conditions, and the mechanical strength, MI values, and thermal properties were measured. The mechanical strength increased slightly as the temperature and RPM increased, and the MI and thermal conductivity also increased. The results of this study can be used as a basis for specifying the conditions of the mixing and compounding process such that the desired mechanical and thermal properties are obtained.

Effect of natural filler amount and kind on the morphological, rheological and mechanical properties of acrylonitrile–butadiene–styrene (ABS) terpolymer was studied in current research. The powdered hazelnut and walnut shells were employed as natural filler with ABS to develop hybrid polymer composites. With single natural filler, it was found that the walnut shell flour was usable for enhancing strengths (tensile, flexural and impact) and modulus (tensile and flexural) in comparison to hazelnut. The highest strengths (tensile, impact and flexural) and flexural modulus were achieved with the amount of 5 wt% hazelnut and 15 wt% walnut shell flour among all hybrid composites. Tensile strain, tensile strength, impact strength, flexural strain and flexural strength of ABS decreased with the mixing of 20 wt% hazelnut and with the mixing of 20 wt% walnut shell flour. The addition of hazelnut shell flour filler alone caused a decrement in melt flow index (MFI) value while the incorporation of walnut shell flour filler alone resulted in an increase in MFI value as compared to pure ABS. It was concluded that hazelnut and/or walnut shell flour-filled polymer composites were usable in applications where lower cost was desirable and some decrements in the mechanical properties were acceptable.

Effect of silica nanoparticles on solid state polymerization of poly(ethylene terephthalate)

Spunbond method is widely used in the production of nonwoven fabrics. Melt flow index (MFI) is one of the most important polymer processing parameters. In this paper, tensile strength and elongation values of spunbond fabrics with four different weights produced from polypropylene polymers with two different MFI values were measured. Tensile strength tests were analyzed by two-way multiple variance analysis (Two-Way Manova) in the SPSS statistical package program, and the effects of MFI and weight values on the strength properties of spunbond textile surfaces were examined. As a result of the statistical analysis, it was observed that statistically significant differences (p < 0.05) occurred in both tensile strength and elongation values with the change of weight value. In addition, significant differences (p < 0.05) occurred in tensile strengths with the change of MFI value, but the differences in elongation values were not statistically significant (p > 0.05).

Comparative techniques for molecular weight evaluation of poly (ethylene terephthalate) (PET)

Graft copolymerization of polypropylene copolymer (PCP) with maleic anhydride (MA) was studied in melt in Brabender Plasticorder, Twin Screw Extruder by using peroxide initiators, such as benzoyl peroxide (BPO), lauryl peroxide (LPO), luperox-101 (LPU), and dicumyl peroxide (DCP). The variation of MA and initiator concentrations on percent grafting (G), melt flow index (MFI), torque, and gel formation was investigated. Graft copolymers (PgMA and PgMAT) were characterized by FT-IR, DSC, and TGA. Melt flow index increased and torque values decreased with an increase in initiator concentration. The increase in MFI values are in the order: DCP>LUP>BP0>LPO. Maximum chain scission was observed by using DCP and LUP as indicated by their MFI values. The incorporation of MA in PgMA and PgMAT was confirmed by the presence of carbonyl groups at 1712 cm−1 and a shift in crystallization peak temperature from 113 to 123°C due to nucleating effect of the poly(maleic anhydride). The thermal stability was increased by the presence of PgMA. Addition of PgMAT as an additive to PCP, PCP/PP, and amines improves mechanical properties and paintability. Primary amines are more reactive towards PgMAT compared to tertiary amines. *IPCL Communication 350.

This study investigates the effect of recycling and nanofiller incorporation on the morphological, rheological, and mechanical properties of various injection moulded polyesters. The research compares the behaviour of two types of bio-based (polylactic acid (PLA) and polybutylene succinate (PBS)) and two types of petroleum-based (polyethylene terephthalate (PET) and polybutylene terephthalate (PBT)) polyesters, including polymers with aliphatic and aromatic structures. Recycling was simulated by repeated extrusion for both unreinforced and 6 wt% montmorillonite (MMT) reinforced nanocomposites. Although in all cases the rheology measurements resulted in shear-thinning behaviour, the complex viscosity range and shape of the curves varied differently for each material depending on the MMT reinforcement and the number of extrusions. The melt flow index (MFI) values showed that neither reprocessing nor MMT had a significant effect on the results of PBT, PBS, and PLA. A sharp increment was observed when PET was processed with MMT, indicating the polymer’s notable degradation. Non-isothermal crystallization was used to investigate the extent of overcooling, and the results were compared at 10°C/min and at cooling rates extrapolated to 1°C/min. The undercooling of PBS and PBT barely changed with reprocessing and MMT content, but degradation in PET also modified the crystallization tendency, while in PLA MMT reinforcement inhibited molecular ordering. The wide-angle X-ray diffraction (WAXD) study showed an intercalated structure for all types of polyester nanocomposites, with minor differences in the layer-stack number. Dynamic mechanical analysis (DMA) indicated changes in the glass transition temperature and storage modulus with reprocessing and the addition of MMT. While below the glass transition temperature, the glassy amorphous phase has a more pronounced effect on the storage modulus, above this temperature the crystalline phase tends to dominate, as the contribution of the amorphous phase in the rubbery state is minor to the stiffness. The homogeneous distribution of MMT was confirmed by the shape of the Cole-Cole diagrams.

Kinetics of thermal degradation occurring on polyester containing cationic dyeable comonomer units viz. 5-sulphoisophthalate moieties are studied by measurement of changes in intrinsic viscosity and carboxyl values on the polymer after subjecting the polymer chips to temperatures in the range 275–285°C for different residence times ranging from 5 to 60 min and comparing with the homopolymer. The activation energy values for degradation are estimated from the kinetic data. Mechanical properties of the textured yarns produced from the partially oriented yarns (POY) spun under different residence times are measured. Yarn produced with higher residence time has poor mechanical properties. The SEM images of the POY show presence of particles at the surface of the yarn due to polymer degradation. The size of the particles as seen on the surface increase with increase of retention time. Addition of thermal stabilizer helps in controlling the thermal degradation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The mechanism of solid state polycondensation has been subjected to a fundamental analysis. Equations were formulated for combined diffusion and chemical reaction for two separate situations. One was for solid state polycondensation in polymer flakes or chips. The other dealt with polymer powders. The resultant solutions related molecular weight changes to rate functions. A technique for deriving the rate functions from experimental data is described.Solid state polycondensations were then studied for nylon 66, nylon 6‐10, and polyethylene terephthalate. These data which ranged from 120 to 200°C. were tested with various mechanisms. The most appropriate one was found to be that developed in the present work. Chemical reaction was found to be the rate controlling step in solid state polycondensation in nylon 66, polyethylene terephthalate, powders of nylon 6‐10 and larger particles of nylon 6‐10 at and above 160°C. Diffusion of byproduct through the solid was the rate controlling step for larger particles of nylon 6‐10 at temperatures below 160°C. Thermograms of nylon 6‐10 indicated morphological changes which possibly influenced the behavior of the larger nylon 6‐10 particles. The Arrhenius relation was fitted to the situations where chemical reaction controlled.

We report on the pilot scale synthesis and melt spinning of poly(ethylene furanoate) (PEF), a promising bio-based fiber polymer that can heave mechanical properties in the range of commercial poly(ethylene terephthalate) (PET) fibers. Catalyst optimization and solid state polycondensation (SSP) allowed for intrinsic viscosities of PEF of up to 0.85 dL·g−1. Melt-spun multifilament yarns reached a tensile strength of up to 65 cN·tex−1 with an elongation of 6% and a modulus of 1370 cN·tex−1. The crystallization behavior of PEF was investigated by differential scanning calorimetry (DSC) and XRD after each process step, i.e., after polymerization, SSP, melt spinning, drawing, and recycling. After SSP, the previously amorphous polymer showed a crystallinity of 47%, which was in accordance with literature. The corresponding XRD diffractograms showed signals attributable to α-PEF. Additional, clearly assignable signals at 2θ > 30° are discussed. A completely amorphous structure was observed by XRD for as-spun yarns, while a crystalline phase was detected on drawn yarns; however, it was less pronounced than for the granules and independent of the winding speed.

The rheological properties in solution, in shear and in uniaxial elongation of poly(ethylene terephthalate) (PET) reacted together with hyperbranched polymers (HBPs) were investigated. Two different PET grades, of low and high molecular weights, were compounded with sub‐ to over‐stoichiometric concentrations of HBPs of second and fourth pseudo‐generation, and subsequently subjected to a solid‐state polycondensation (SSP). The formation of microgels, which occurs at high HBP concentration, gave rise to a large increase in melt elasticity and a related decrease in melt strength. At low HBP concentrations, the complex viscosity of the unreacted HBP/PET was considerably reduced, thus demonstrating a lubrication effect of the HBP molecules. During SSP, the intrinsic and shear viscosities exhibited a gradual increase, which was similar for both PET and HBP/PET blends, and was correlated to an increase in molecular weight, through linear‐chain extension and branching reactions. The elongational viscosity of the reactive blends was also increased as a function of reaction time, and this increase was much larger in the case of the HBP/PET blends. A 400% increase in melt strength of the PET was obtained by combining SSP and trace amounts of an HBP of second generation, without any decrease in drawability.

The influence of tie‐layer Melt Flow Index on the lap‐shear strength of ultrasonic welds in oriented polypropylene (OPP) has been evaluated. The tie‐layer Melt Flow Index was varied from 0.03 dg/min to 2600 dg/min; the highest lap‐shear strength properties were obtained using tie‐layers that had melt flow index values between 30 and 100 dg/min. When using low Melt Flow Index tie‐layers, hot spot formation and concomitant changes in fusion zone and heat‐affected‐zone dimensions produced stress concentrations that promoted failure in oriented polypropylene material away from the bondline region. When very high Melt Flow Index (2600 dg/min) tie‐layers were used, the mode of failure during lap‐shear testing was a mix of cohesive, in oriented polypropylene, and adhesive failure. The molecular weight of material at the bondline was not markedly affected by the thermal cycle produced during ultrasonic welding. Only the flash ejected when using low Melt Flow Index tie‐layers exhibited any evidence of degradation; it is suggested that the ejected flash may have been degraded because of a combination of thermal, cavitation, and thermo‐oxidative processes.

Graft copolymerization of polypropylene copolymer (PCP) with maleic anhydride (MA) was studied in melt in Brabender Plasticorder, Twin Screw Extruder by using peroxide initiators, such as benzoyl peroxide (BPO), lauryl peroxide (LPO), luperox-101 (LPU), and dicumyl peroxide (DCP). The variation of MA and initiator concentrations on percent grafting (G), melt flow index (MFI), torque, and gel formation was investigated. Graft copolymers (PgMA and PgMAT) were characterized by FT-IR, BSC, and TGA. Melt flow index increased and torque values decreased with an increase in initiator concentration. The increase in MFI values are in the order: DCP > LUP > BPO > LPO. Maximum chain scission was observed by using DCP and LUP as indicated by their MFI values. The incorporation of MA in PgMA and PgMAT was confirmed by the presence of carbonyl groups at 1712cm−1 and a shift in crystallization peak temperature from 113 to 123°C due to nucleating effect of the poly(maleic anhydride). The thermal stability was increased by the presence of PgMA. Addition of PgMAT as an additive to PCP, PCP/PP, and amines improves mechanical properties and paintability. Primary amines are more reactive towards PgMAT compared to tertiary amines.