TL;DR When a brief asks for a bottle in recycled PET, two conversations arrive bundled: the material story and the engineering verification. The recorded line keeps them separated. PET is a recorded material, the recycled-grade family records PCR PP, PCR PET, PCR PETG, PCR ABS and PCR AS, and the airless bottle family records 89 catalog models with capacities 5 ml to 120 ml including a recorded PCR PP/PET/PETG capability — while no rPET grade or intrinsic viscosity value is recorded in the catalog and solid-state polycondensation is not a recorded process. The mechanism is general engineering knowledge: every re-melt cuts some polymer chains, intrinsic viscosity drifts down, acetaldehyde-related chemistry becomes more relevant for sensitive formulas, and wall behavior, including the stiffness of thick-walled bottles, follows from the resin that goes in. Grade selection, IV targets, and recovery conditions are not published by the program; configured and confirmed per project.
Why
A recycled-content PET request usually arrives as a single sentence: "we want our airless bottle in rPET." Behind it sit two jobs: the feedstock story — where the resin comes from and what documentation that requires — and the engineering job — what happens to the polymer when pellets are reheated and re-molded into a bottle.
The second job is easier to underestimate. PET does not survive processing unchanged: residual moisture attacks the chains, heat and shear pull at them, and every thermal cycle shortens their average length. That shortening is measured as a drop in intrinsic viscosity — IV — the solution-viscosity-based measure of average chain length, expressed in dl/g. A higher-IV resin carries longer chains, which directionally means more melt strength during blowing, more robustness in the finished wall, and less sensitivity to weak spots in thin sections. A resin that has already lost IV in its first life loses more in the next re-melt, and the packaging team inherits the difference.
The program's recorded picture frames the conversation cleanly. PET is a recorded material, and the recycled-grade family records PCR PP, PCR PET, PCR PETG, PCR ABS and PCR AS — so a recycled-content PET conversation starts from a recorded anchor. The airless bottle family records 89 catalog models with capacities 5 ml to 120 ml and a recorded PCR PP/PET/PETG capability. And the boundaries are explicit: no rPET grade or intrinsic viscosity value is recorded in the catalog, and solid-state polycondensation is not a recorded process. This article explains the mechanism — why IV drops, what that costs a bottle, and what recovery routes realistically exist.
How
1. The recycled-content route as the bottle program sees it
Mechanically, the route is: use — collection — sorting — flaking — pelletizing — re-melt and re-mold. Each stage is a thermal or mechanical episode, and each costs the polymer a little chain length. The program-facing detail: the route's input is recorded — PCR PET belongs to the recorded recycled-grade family — while the specific rPET grade that will actually be molded is not. The lifecycle is real at family level; the resin reality is per-project.
2. What the re-melt does at the molecular level
Three degradation channels dominate melt processing of PET. Hydrolysis: residual moisture attacks ester linkages and cuts chains directly, which is why drying discipline is core to PET processing. Thermal degradation: sustained melt residence promotes random scission. Shear: the elongational stresses of extrusion and injection pull at stressed chains. All three move the same direction: average chain length falls and IV drifts down. In mechanism terms, IV is the molar-mass thermometer of the melt: longer chains, higher IV, and the opposite after re-melting. No values are publishable here — the drop is resin-, condition-, and history-dependent — which is why it is measured, not assumed.
3. Why IV matters once the part is a bottle
In preform-based blow molding — injection stretch blow molding and compression blow forming alike, see the comparison of the two routes — the reheat and stretch step is where the melt must hold together. Higher IV directionally means more melt strength, a more even wall distribution, and fewer weak spots. The outcome the brand feels is wall behavior: stiffness, toughness against squeezes and drops, flexing resistance of thick-walled geometry. The stiffness of thick-walled bottles is a recurring question for recycled-content resin: the wall comes out of the mold equal to the resin that went in. A quieter subject is acetaldehyde, a melt-processing by-product that can migrate into the packaged contents — why sensitive fragrance and skin-care formulas care about it. No levels are recorded or published; the parameter is established per project on the actual resin and conditions.
4. The recovery directions: re-melt blending and the SSP route
Once the resin has been through a first re-melt, a project has two recovery directions. The first is blending at the melt: combining the recycled resin with longer-chain material so the compound's effective IV lands where the part needs it — a formulation exercise with ratio and acceptance criteria set per project, no published figures.
The second is solid-state polycondensation — SSP. The mechanism: rather than re-extending chains in the melt, the resin is held below its melting point for extended time, typically under vacuum or inert gas, pushing the polymerization equilibrium toward longer chains without fully melting the material. Under controlled conditions, SSP can rebuild intrinsic viscosity and reduce acetaldehyde precursors. The honest boundary: solid-state polycondensation is not a recorded process — every governing condition, temperature, time, pressure, batch size, is not published by the program; configured and confirmed per project. SSP is a project route, not a catalog service.
5. What the project record must carry
Because no rPET grade or intrinsic viscosity value is recorded in the catalog, the project record carries the whole position: the chosen grade and its supplier documentation, the IV measurement method, the acceptance window, the drying and re-melt conditions, and the sampling scheme. On the catalog side, the recorded tools are quality anchors: the twelve-test laboratory matrix covers failure modes at capability level, and the quality control program applies with criteria configured per project.
6. Anchoring the production reality
The lifecycle and its recorded anchor, in flow:
<pre class="language-mermaid"><code>flowchart LR
A[Virgin PET] –> B[Use]
B –> C[Collection and sorting]
C –> D[Flake and pellet]
D –> E[Re-melt: IV loss by chain scission]
E –> F{Route per project}
F –> G[Re-melt blending<br/>per project]
F –> H[SSP conditioning<br/>project route only]
G –> I[Recorded anchor: PCR PET<br/>in the recycled-grade family]
H –> I
E –> I
</code></pre>
The anchor is family-level: PCR PET exists in the recorded recycled-grade family, and the airless family's 89 models, 5 ml to 120 ml, carry its recorded PCR PP/PET/PETG capability. Everything between the re-melt and the finished wall is per-project engineering.
What
Everything in this section is recorded program data:
- PET is a recorded material.
- The recorded recycled-grade family is PCR PP, PCR PET, PCR PETG, PCR ABS and PCR AS; the PCR PET grade sits inside it.
- The airless bottle family records 89 catalog models with capacities 5 ml to 120 ml and a recorded PCR PP/PET/PETG capability.
- No rPET grade or intrinsic viscosity value is recorded in the catalog.
- Solid-state polycondensation is not a recorded process.
Gotchas
- IV figures travel badly between resins. No intrinsic viscosity value is recorded, and the re-melt drop is history-dependent — a figure in a sales conversation is not program data and must be traced to a measurement on the actual resin.
- "rPET" does not name a recorded grade. Since no rPET grade is recorded, copy presenting a specific recycled grade as a catalog position would be a claim without an evidence base; the grade is defined per project.
- SSP is not a program process. The boundary sentence is absolute — solid-state polycondensation is not a recorded process — so mentioning SSP as a cataloged capability would overreach; it is a project route.
- Wall stiffness of thick-walled bottles is a project finding, not a catalog property. The family record — 89 models, 5 ml to 120 ml — describes the geometry range and the recorded PCR capability; it asserts nothing about the stiffness of any particular recycled-content wall.
- Acetaldehyde-related behavior has no recorded figures. It belongs with the melt-history variables; a sensitive formula routes it through per-project evaluation with the project's own conditions.
- Keep the recycled-content claim inside the record. The PCR PP/PET/PETG capability is recorded at family level, and any actual recycled share in a produced part is a per-project configuration — the record supplies no blanket content statement for every bottle built.