The Solid State Polymerization (SSP) process refers to the condensation polymerization reaction of solid chips, aiming to increase the molecular weight and intrinsic viscosity (IV). The normal PET Chips are heated to the glass transition temperature (usually 10-40 ° C below the melting point). The small molecular products are taken away by vacuum or inert gas protection (generally using high-purity nitrogen), so the polycondensation reaction is continued and the viscosity is further increased. End Carboxyl (COOH) content can be decreased when IV content is increased. This process can be used to produce various bottle-grade polyester, industrial filament-grade, low-end group content PET chips, etc. SSP can be classified as continuous or batch SSP according to the process.

The table below explains the difference between continuous and batch Solid State Polymerization (SSP) processes.

(One Production line )
Advantages Process Units
Batch SSP      (Drum SSP) 1-20 tons/batch 1. Flexible product adjustment  2. Suitable for small-batch production 1. Rotary drum system: used for chip crystallization, drying, and polymerization reactions                            2. Vacuum system: creating a vacuum inside the rotary drum and removing the by-products of the reaction                   3. Thermal Oil Circulation System: heating and cooling the materials
Continuous SSP 15 tons/day

– 750 tons/day

 1. Stable Product quality           2. Uniform crystallization       3. Less dust content                   4. Low energy consumption





1. Crystallizer: producing high and uniform crystallization of chips, effectively preventing agglomeration                  2. Preheater: heating the chips to the temperature required for solid-state polymerization, while increasing the viscosity to some extent                       3. Reactor: tackifying chips to the target viscosity (Different products can be obtained by adjusting the process parameters.)                     4. Cooler: cooling chips to the desired temperature                      5. Conveyor system: providing various transportation ways to move chips to different process stages                   6. Nitrogen Purification System: purifying the circulating nitrogen gas from the system, effectively removing small molecule impurities.                         7. Electrical Control System: monitoring and recording data. (Advanced software and user-friendly interface design ensure clear and intuitive data display, making it easy to operate.)

Our factory has installed one batch SSP equipment (10 tons/batch) and two continuous SSP equipment (30 tons/day and 50 tons/day). With the help of the equipment, we have successfully customized high IV and Low COOH PET for our domestic and overseas customers. Below are the specs for your reference. If you have any inquiries, please feel free to contact us.

Property Unit Test Result
Intrinsic Viscosity          (60:40, Phenol: TCE @25℃) dl/g 0.836 1.02
Melting Point 260 253.4
Color (b Value) 2.62 5.16
End Carboxyl mol/t 29.74 12.40
Moisture Content % 0.065 0.065
DEG Content mol/t 1.29 0.86
Agglomerate Particle pce/mg 0.5 0.5
TiO2 Content % 0.30