A comprehensive single‐particle model for solid‐state polymerization of poly(L‐lactic acid)

We propose here, a comprehensive model for the solid‐state polymerization (SSP) of a low to moderate molecular weight (MW) prepolymer of lactic acid, to produce high MW poly(L ‐lactic acid) (PLLA). The reactions are rationally assumed to occur only in the amorphous region, and effective concentrations of end groups, vary with crystalinity, X_c, during SSP. We estimate byproduct diffusivities, D, using free volume theory. The effects of various parameters on the SSP of PLLA prepolymer have been examined with respect to the optimum MW, X_c and D. We introduce self‐consistently, scaling factors of ～ 0.27, in the experimental procedure, to determine via ¹⁹F‐NMR, concentrations of the end groups, after converting them to fluorinated ester groups. The relevant reaction rate constants are obtained by fitting to early time data from representative SSP experiments at 150°C, under high vacuum, on PLLA prepolymer powder (i.e., spherical geometry) of number average MW, M_n0 ～ 10,200 Da, which attains M_n ～ 150,000 Da, via SSP. The subsequent successful comparison of the model predictions with experimental data throughout the entire SSP duration indicates that the model is comprehensive and accounts for all the relevant phenomena occurring during the SSP to synthesize high MW PLLA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

High molecular weight poly (L‐lactic acid) clay nanocomposites via solid‐state polymerization

We propose here, a novel technique to synthesize high molecular weight (MW) poly (L ‐lactic acid)‐clay nanocomposite (PLACN), via solid state polymerization (SSP). We synthesize prepolymer of PLACN (pre‐PLACN) from both, L ‐lactic acid and L ‐lactide, as starting materials. Synthesis of pre‐PLACN from L ‐lactic acid is carried out via in situ melt polycondensation (MP) of L ‐lactic acid oligomer, followed by SSP, to achieve high MW PLACN (M_w ∼ 138,000 Da). In case of L ‐lactide as the starting material, we prepare L ‐lactide–clay intercalated mixture which yields moderate MW pre‐PLACN during subsequent ring opening polymerization (ROP). Interestingly, ROP is performed by using hydroxyl functionalized ternary catalyst system (L ‐lactide–Sn(II) octoate–oligo (L‐lactic acid) complex), which provides the terminal hydroxyl end‐groups, required for step‐growth SSP. Pre‐PLACN MW is now increased to M_w ∼ 127,000 Da, by the subsequent SSP process. ¹H NMR analyses confirm that these end‐groups, are indeed consumed during SSP. During SSP, the PLACN also achieves up to 90% crystallinity, which may be due to the synchronization of the slow step‐growth SSP of poly(L ‐lactic acid) (PLA) with the crystallization kinetics. Optical purity of PLACNs is similar to that of neat PLA, whereas the thermal stability of PLACNs is significantly superior. As evidenced by wide‐angle X‐ray scattering/small‐angle X‐ray scattering analyses and in line with the literature, both, intercalated and exfoliated PLACN morphologies, have been synthesized, by suitable selection of clays. We also verify the correlation between the PLA semicrystalline morphology and the PLACN morphology, which is consistent with those of PLACN synthesized by other techniques. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Solid‐state polymerization of poly(trimethylene terephthalate)

The solid‐state polymerization (SSP) of poly(trimethylene terephthalate) (PTT) has been studied and compared with that of poly(ethylene terephthalate) (PET). Because PTT and PET share the same SSP mechanism, the modified second‐order kinetic model, which has successfully been used to describe the SSP behaviors of PET, also fits the SSP data of PTT prepolymers with intrinsic viscosities (IVs) ranging from 0.445 to 0.660 dL/g. According to this model, the overall SSP rate is ?dC/dt = 2k_a(C ? C_ai)², where C is the total end group concentration, t is the SSP time, k_a is the apparent reaction rate constant, and C_ai is the apparent inactive end group concentration. With this equation, the effects of all factors that influence the SSP rate are implicitly and conveniently incorporated into two parameters, k_a and C_ai. k_a increases, whereas C_ai decreases, with increasing SSP temperature, increasing prepolymer IV, and decreasing pellet size, just as for the SSP of PET. Therefore, the SSP rate increases with increasing prepolymer IV and increasing SSP temperature. The apparent activation energy is about 26 kcal/mol, and the average SSP rate about doubles with each 10°C increase in temperature within the temperature range of 200–225°C. The SSP rate increases by about 30% when the pellet size is decreased from 0.025 to 0.015 g/pellet. Compared with PET, PTT has a much lower sticking tendency and a much higher SSP rate (more than twice as high). Therefore, the SSP process for PTT can be made much simpler and more efficient than that for PET. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3188–3200, 2003     

Effects of the carboxyl concentration on the solid‐state polymerization of poly(ethylene terephthalate)

There are two types of polycondensation reactions in the solid‐state polymerization (SSP) of poly(ethylene terephthalate) (PET), namely, transesterification and esterification. Transesterification is the reaction between two hydroxyl ends with ethylene glycol as the byproduct, and esterification is the reaction between a carboxyl end and a hydroxyl end with water as the byproduct. The SSP of powdered PET in a fluid bed is practically a reaction‐controlled process because of negligible or very small diffusion resistance. It can be proved mathematically that an optimal carboxyl concentration for reaction‐controlled SSP exists only if k₂/k₁ > 2, where k₂ and k₁ are the forward reaction rate constants of esterification and transesterification, respectively. Several interesting observations were made in fluid‐bed SSP experiments of powdered PET: (1) the SSP rate increases monotonously with decreasing carboxyl concentration, (2) k₂ < k₁ in the presence of sufficient catalyst, (3) k₁ decreases with increasing carboxyl concentration if the catalyst concentration is insufficient, and (4) the minimum catalyst concentration required to achieve the highest SSP rate decreases with decreasing carboxyl concentration. In the SSP of pelletized PET, both reaction and diffusion are important, and there exists an optimal carboxyl concentration for the fastest SSP rate because esterification, which generates the faster diffusing byproduct, is retarded less than transesterification in the presence of substantial diffusion resistance. The optimal prepolymer carboxyl concentration, which ranges from 25 to 40% of the total end‐group concentration in most commercial SSP processes, increases with increasing pellet size and product molecular weight. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1288–1304, 2002     

Solid‐state polymerization and characterization of a copolyamide based on adipic acid, 1,4‐butanediamine,and 2,5‐furandicarboxylic acid

2,5‐Furandicarboxylic acid (FDCA) is a promising biobased alternative material to terephthalic acid. In this study, three types of poly(butylene adipamide) (PA‐4,6) containing 10, 20, and 30 mol % of poly(butylene‐2,5‐furandicarboxylamide) (PA‐4,F) were synthesized through consecutive prepolymerization and solid‐state polymerization (SSP). The incorporation of a 10 mol % PA‐4,F component into PA‐4,6 resulted in slight increases in the intrinsic viscosity (IV) and glass‐transition temperature (T_g) after 12 h of SSP at 220 °C. When the SSP temperature and reaction time increased, IV increased proportionally. The highest IV value of 0.75 was obtained by 48 h of SSP at 240 °C, whereas increases in the PA‐4,F content to 20 and 30 mol % gave rise to decreases in IV, T_g, and melting temperature; this interrupted the increase in SSP temperature. The thermal decomposition temperature of the PA‐4,F‐incorporated polyamide was lower than that with PA‐4,6 because of the lower thermal stability of the FDCA component. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43391.     

Catalyzed chain extension of poly(butylene adipate) and poly(butylene succinate) with 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline)

Low‐molecular‐weight HOOC‐terminated poly(butylene adipate) prepolymer (PrePBA) and poly(butylene succinate) prepolymer (PrePBS) were synthesized through melt‐condensation polymerization from adipic acid or succinic acid with butanediol. The catalyzed chain extension of these prepolymers was carried out at 180–220°C with 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) as a chain extender and p‐toluenesulfonic acid (p‐TSA) as a catalyst. Higher molecular weight polyesters were obtained from the catalyzed chain extension than from the noncatalyzed one. However, an improperly high amount of p‐TSA and a high temperature caused branching or a crosslinking reaction. Under optimal conditions, chain‐extended poly(butylene adipate) (PBA) with a number‐average molecular weight up to 29,600 and poly(butylene succinate) (PBS) with an intrinsic viscosity of 0.82 dL/g were synthesized. The chain‐extended polyesters were characterized by IR spectroscopy, ¹H‐NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis, wide‐angle X‐ray scattering, and tensile testing. DSC, wide‐angle X‐ray scattering, and thermogravimetric analysis characterization showed that the chain‐extended PBA and PBS had lower melting temperatures and crystallinities and slower crystallization rates and were less thermally stable than PrePBA and PrePBS. This deterioration of their properties was not harmful enough to impair their thermal processing properties and should not prevent them from being used as biodegradable thermoplastics. The tensile strength of the chain‐extended PBS was about 31.05 MPa. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The effect of prepolymer crystallinity on solid-state polymerization of poly(bisphenol A carbonate)

The effect of prepolymer crystallinity on the solid-state polymerization (SSP) of poly(bisphenol A carbonate) was examined using nitrogen as a sweep fluid. A low-molecular-weight prepolymer was synthesized by melt transesterification and prepolymers with different crystallinities (11.7%, 23.3%, 33.7%) were prepared with supercritical carbon dioxide treatment. SSP of the three prepolymers was then carried out at reaction temperatures in the range of 150-190 °C, with a prepolymer particle size of 75 μm and a N₂ flow rate of 1600 ml/min. The glass-transition temperature (T_g), absolute weight-average molecular weight (M_n), and percent crystallinity were measured at various times during each SSP. At each reaction temperature, SSP of the lower crystallinity prepolymer (11.7%) always resulted in higher-molecular-weight polymers, compared with the polymers synthesized using the higher crystallinity prepolymer (23.3% and 33.7%). The crystallinity of the polymers synthesized from the high crystallinity prepolymer was significantly higher than for those synthesized from the low crystallinity prepolymer. Higher crystallinity of the prepolymer and the synthesized polymers may lower the reaction rate by reducing chain-end mobility or/and by inhibiting byproduct diffusion.     

Kinetics of the solid‐state polymerization of nylon‐6

The kinetics of the thermally induced solid‐state polymerization (SSP) of nylon‐6 were examined in both a fixed‐bed reactor and a rotary reactor. Factors such as the regulator content, the reaction temperature and time, the particle size, the type and geometry of the nylon‐6 prepolymer, the nitrogen gas flow rate, the water content of the nitrogen gas flow, and the polymerization process were studied. The results showed that the regulator content, the reaction temperature and time, and the particle size were the primary factors, and that the others were negligible. Moreover, the SSP rate and number‐average molecular weight (M_n) increased with increasing reaction temperature and time and decreasing particle size. The SSP rate and M_n had maximum values with increasing regulator content in an experimental range of 0.03–0.07 wt %. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 616–621, 2002; DOI 10.1002/app.10341     

Morphological changes of poly(ethylene terephthalate‐co‐isophthalate) during solid state polymerization

Poly(ethylene terephthalate‐co‐isophthalate) (PETI) prepolymer was submitted to solid state polymerization (SSP) at 184–230°C in a fixed bed reactor, to study the evolution of morphological changes during the process. Short reaction times were selected to investigate crystallization phenomena during nonisothermal (heating) and isothermal SSP phases. More specifically, multiple PETI melting behavior was observed and attributed to secondary crystallization, the rate of which increased significantly with SSP temperature. Reaction time was also found to exert a positive effect on solid‐phase perfection of secondary crystals, leading at each temperature to melting points close to the value of bottle‐grade poly(ethylene terephthalate). Finally, the mass fraction crystallinity of the SSP grades was found to comply with the crystal morphology encountered. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Crystallization and solid‐state polymerization of poly(aryl ester)s

The crystallization and solid‐state polymerization (SSP) of poly(aryl ester)s was investigated. Oligomers with different end‐groups were prepared by degradation of commercially available poly(aryl ester)s. The SSP of these oligomers was carried out after crystallization and under reduced pressure, in the presence of various catalysts. Polymers were characterized by means of their inherent viscosities and thermal properties. It has been found that Ti(OⁱPr)₄ was a better catalyst for SSP. The structures and morphologies of semicrystalline poly(aryl ester)s were investigated by X‐ray diffraction and differential scanning calorimetry (DSC). Copyright © 2004 Society of Chemical Industry     

Effect of poly(ethylene glycol) on the solid‐state polymerization of poly(ethylene terephthalate)

Poly(ethylene glycol) (PEG) and end‐capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol^?1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in T_g and similar crystallization behavior. Solid‐state polymerization (SSP) was performed on these blend samples using Sb₂O₃ as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry     

Synthesis of polymer materials by low energy electron beam. III. Effects of polymerization temperature in EB solid-state polymerization of semicrystalline urethane-acrylate film

In an electron beam (EB) polymerization of a urethane-acrylate prepolymer, the polymerization temperature greatly affected the structure and properties of the resulting gel film. Urethaneacrylate, which was synthesized by the reaction of poly(butylene adipate)diol, 4,4′-diphenylmethane diisocyanate, and 2-hydroxyethyl acrylate, was used as a prepolymer. The prepolymer was semicrystalline and showed a melting point in the region of 50–60°C. The maximum polymerization rate of the prepolymer was obtained when the prepolymer film was irradiated in the temperature range of 25–40°C. EB polymerization below the melting point (T_m) of the prepolymer produced semicrystalline polyurethane-acrylate gel films with a spherulitic texture. On the other hand, EB polymerization above the T_m destroyed the crystalline phase of the prepolymer to give transparent gel films. The gel film cured below the T_m had higher stress at yield, Young's modulus, and tensile strength than those cured above the T_m. Such temperature effects are attributed to whether or not the EB polymerization proceeds with retention of crystalline structure of the prepolymer.     

Morphology and properties of poly(benzoxazine‐co‐urethane)s based on bisphenol‐S/aniline benzoxazine

Poly(benzoxazine‐co‐urethane) was prepared by melt‐blending bisphenol‐S/aniline‐type benzoxazine (BS‐a) with isocyanate‐terminated polyurethane (PU) prepolymer based on 2,4‐toluene diisocyanate and poly(ethylene glycol), followed by thermally activated polymerization of the blend. The copolymerization reaction between BS‐a and PU prepolymer was monitored using Fourier transform infrared spectroscopy. The morphology, dynamic mechanical properties, and thermal stability of the poly(benzoxazine‐co‐urethane) were studied using scanning electron microscopy, dynamic mechanical analysis, and thermogravimetry. Homogeneous morphology is shown in scanning electron micrographs of the fracture surfaces of poly(benzoxazine‐co‐urethane)s with different urethane weight fractions, and the roughness of the surface increases with urethane content increasing. Correspondingly, a single glass transition temperature (T_g) is shown on the dynamic mechanical analysis curves of the poly(benzoxazine‐co‐urethane)s, and the T_g is higher than that of the polybenzoxazine. With increase in the urethane content, the T_g and water absorption of poly(benzoxazine‐co‐urethane) increase, whereas the storage modulus and thermal stability decrease. POLYM. ENG. SCI., 53:2633–2639, 2013. © 2013 Society of Plastics Engineers     

Solid‐state polymerization of poly(ethylene 2,6‐naphthalate)

The solid‐state polymerization (SSP) of poly (ethylene 2,6‐naphthalate) (PEN) was studied and compared with that of poly(ethylene terephthalate) (PET). The SSP of PEN, like that of PET, could be satisfactorily described with a modified second‐order kinetic model, which was based on the assumptions that part of the end groups were inactive during SSP and that the overall SSP followed second‐order kinetics with respect to the active end‐group concentration. The proposed rate equation fit the data of the SSP of PEN quite well under various conditions. PEN prepolymers in pellet and cube forms with intrinsic viscosities (IVs) ranging from 0.375 to 0.515 dL/g, various particle sizes, and various carboxyl concentrations were solid‐state polymerized at temperatures ranging from 240 to 260°C to study the effects of various factors. The SSP data obtained in this study could be readily applied to the design of commercial PEN SSP processes. Because PEN and PET share the same SSP mechanism, in general, the SSP behaviors of PEN are similar to those of PET. Thus, the SSP rate of PEN increased with increasing temperature, increasing prepolymer IV, and decreasing prepolymer particle size. However, because of the much higher barrier properties of PEN, the prepolymer particle size and carboxyl concentration had much greater effects on the SSP of PEN than on the SSP of PET. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1075–1084, 2007     

Evaluation of biocompatibility of the surface of polyethylene films modified with various water soluble polymers using Ar plasma‐post polymerization technique

Surface modified polyethylene (g‐PE), PMPC‐g‐PE, PGEMA‐g‐PE, PNIPAAm‐g‐PE and PHPMA‐g‐PE films with the water soluble polymers such as poly[2‐(methacryloyloxy)ethyl phosphorylcholine] (PMPC), poly[2‐(glucosyloxy)ethyl methacrylate] (PGEMA), poly(N‐isopropylacrylamide) (PNIPAAm) and poly[N‐(2‐hydroxypropyl) methacrylamide] (PHPMA) were prepared by graft copolymerization using an Ar plasma‐post polymerization technique. The surface of the g‐PE films was characterized by means of X‐ray photoelectron spectroscopy and the grafting percentage of PMPC, PNIPAAm and PHPMA was found to be 5.31, 2.83, and 3.40% for the corresponding g‐PE film. Biocompatibility of the g‐PE films was evaluated by the adsorption of serum proteins and the Michaelis constant (K_m) for the enzymatic reaction of thrombin with synthetic substrate S‐2238 in the presence of g‐PE film. The biocompatibility of water soluble polymers such as PMPC, polyoxyethylene (POE), PGEMA, PNIPAAm and PHPMA was also evaluated by the same enzymatic reaction of thrombin with S‐2238 in their polymer solutions. The K_m values in the presence of water soluble polymers was found to decrease in the order PMPC > POE > PGEMA > PNIPAAm > PHPMA. As a conclusion, PMPC‐g‐PE film exhibited the most biocompatibility among g‐PE films because its surface adsorbed less protein than those of the untreated PE and other g‐PE films and it showed the largest K_m for the enzymatic reaction.     

On the topology of highly branched polyethylenes prepared by amine−imine nickel and palladium complexes: the effect of ortho‐aryl substituents

Series of nickel and palladium complexes bearing amine?imine ligands in various ortho‐aryl and backbone positions were prepared and investigated in ethene polymerization. Ethene polymerization initiated by symmetrically ortho‐substituted nickel and palladium amine?imine catalysts is controlled. Mono‐substitution in the ortho‐aryl positions of nickel complexes is not as efficient in protecting centers from chain transfer as di‐substitution. Both the central metal and the size of the ortho‐aryl substituent have a significant effect on the polyethylene (PE) topology. Based on detailed characterization by high temperature SEC‐IR‐η, SEC with multi‐angle laser light scattering and ¹³C NMR data, PEs prepared by nickel amine?imine complexes have a linear rather than dendritic topology. In contrast, palladium amine?imine complexes with small ortho‐aryl substituents at low ethene pressure were shown for the first time to form dendritic PEs with topology comparable to PEs formed by α‐diimine palladium catalyst. © 2018 Society of Chemical Industry     

Controlled synthesis of low‐molecular‐weight polyethylene waxes by titanium–biphenolate–ethylaluminum sesquichloride based catalyst systems

Soluble complexes of titanium(IV) bearing sterically hindered biphenols, such as biphenol, 1,1′‐methylene di‐2‐naphthol, 2,2′‐methylene bis(4‐chlorophenol), 2,2′‐methylene bis(6‐tert‐butyl‐4‐ethyl phenol), and 2,2′ ethylidene bis(4,6‐di‐tert‐butyl phenol), were prepared and characterized. These catalyst precursors, formulated as [Ti(O∧O)X₂], were active in the polymerization of ethylene at high temperatures in combination with ethylaluminum sesquichloride as a cocatalyst. The ultra‐low‐molecular‐weight polyethylenes (PEs) were linear and crystalline and displayed narrow polydispersities. The catalytic polymerization leading to PE waxes in this reaction exhibited unique properties that have potential applications in surface coatings and adhesive formulations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1531–1539, 2007     

Synthesis and characterization of biodegradable poly(butylene succinate‐co‐propylene succinate)s

Biodegradable polyesters such as poly(butylene succinate) (PBS), poly(propylene succinate) (PPS), and poly(butylene succinate‐co‐propylene succinate)s (PBSPSs) were synthesized respectively, from 1,4‐succinic acid with 1,4‐butanediol and 1,3‐propanediol through a two‐step process of esterification and polycondensation in this article. The composition and physical properties of both homopolyesters and copolyesters were investigated via ¹H NMR, DSC, TGA, POM, AFM, and WAXD. The copolymer composition was in good agreement with that expected from the feed composition of the reactants. The melting temperature (T_m), crystallization temperature (T_c), crystallinity (X), and thermal decomposition temperature (T_d) of these polyesters decreased gradually as the content of propylene succinate unit increased. PBSPS copolyesters showed the same crystal structure as the PBS homopolyester. Besides the normal extinction crosses under the polarizing optical microscope, the double‐banded extinction patterns with periodic distance along the radial direction were also observed in the spherulites of PBS and PBSPS. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of the novel block copolymer poly(ε‐caprolactone)‐b‐poly(4‐vinyl pyridine) by the combination of coordination and controlled free‐radical polymerizations

A novel block copolymer, poly(ε‐caprolactone)‐b‐poly(4‐vinyl pyridine), was synthesized with a bifunctional initiator strategy. Poly(ε‐caprolactone) prepolymer with a 2,2,6,6‐tetramethylpiperidinyloxy (TEMPO) end group (PCL_T) was first obtained by coordination polymerization, which showed a controlled mechanism in the process. By means of ultraviolet spectroscopy and electron spin resonance spectroscopy, the TEMPO moiety was determined to be intact in the polymerization. The copolymers were then obtained by the controlled radical polymerization of 4‐vinyl pyridine in the presence of PCL_T. The desired block copolymers were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, and NMR spectroscopy in detail. Also, the effects of the molecular weight and concentration of PCL_T on the copolymerization were investigated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2280–2285, 2004     

Solid-state polycondensation of poly(ethylene terephthalate) modified with isophthalic acid: kinetics and simulation

The kinetics for the solid-state polycondensation (SSP) of poly(ethylene terephthalate) modified with isophthalic acid at the protection of nitrogen gas was studied in the paper. A kinetic model controlled by the reversible chemical reactions and the three dimension diffusions of small molecule by-products has been established. The kinetic parameters of the SSP of PET at different temperatures, including the forward rate constants of transesterification reaction (k₁) and esterification reaction (k₂), the diffusion coefficients of EG (D₁) and water (D₂), the concentrations of EG (g_s) and water (w_s) on the surface of PET chips in SSP, and the activation energies of these kinetic parameters were obtained by experiments and solution of the model. Using the model and the kinetic parameters, the SSP of poly(ethylene terephthalate) modified with isophthalic acid can be simulated with good accuracy. In addition, the influences of nitrogen gas flow rate, the chip dimension and the carboxyl end-group concentration of the PET prepolymer on the molecular weight of PET after SSP, and the change of the EG concentration of PET chips with reaction time were also studied by simulation.