PBT

Identity and selection boundary

Ensinger's TECADUR PBT GF30 natural stock-shape sheet gives 0.02% water absorption after 24 h and 0.04% after 96 h at 23°C, by DIN EN ISO 62, on an approximately 50 mm × 13 mm specimen. These are finished-specimen data. Pellet moisture for melt processing needs a separate check. Ensinger stock-shape test table

PBT is polybutylene terephthalate, an engineering polyester; the polymer abbreviation is not a complete material specification. Celanese separates its Celanex/Crastin offering into unfilled, reinforced, flame-retardant, low-warpage and hydrolysis-resistant grades. Its unfilled grades serve applications without high stiffness requirements, while hydrolysis-resistant grades target hot, humid environments. These categories are selection routes, not interchangeable formulations. Record the manufacturer, full grade, color, supplied form and processing route before comparing properties. Celanese, PBT product overview

Reinforcement and manufacturing route

BASF lists unreinforced Ultradur B4520 for profiles, pipes and injection-molded functional parts; B4300 G6 contains 30% glass fiber by mass. Its brochure explains that glass-fiber orientation produces different longitudinal and transverse shrinkage. Part geometry, wall distribution, gate location and process conditions influence warpage. Mold temperature also affects later dimensional change: an as-molded dimension does not establish the dimension after heat exposure. BASF, Ultradur product brochure, pp. 12, 31–33

Consequently, evaluate a ribbed housing, snap feature and bearing seat separately. A reinforcement choice that addresses housing rigidity still needs a check of assembly strain and dimensional variation. When changing gates or converting a machined prototype to molding, reopen the dimensional qualification rather than copying the prototype's inspection results.

A bounded stock-material example

Ensinger's TECADUR PBT GF30 natural data sheet covers semi-finished rod, plate and hollow stock. Its indicative values include:

The sheet states that values are guides, not specification minima or maxima. Unless otherwise stated, tests use extruded and machined specimens from reference stock, generally 40–60 mm diameter rods. Dimensions and orientation affect properties. It specifically identifies lack of hot-water resistance above 60°C; the listed melting temperature therefore cannot justify hot-water service. Ensinger, TECADUR PBT GF30 natural, version AE, dated 19 July 2023

Moisture control during processing

Low water absorption in a finished specimen does not establish that pellets are dry enough to melt-process. Celanese's historical Polyester Technical Manual specifies a maximum 0.02% moisture for Celanex PBT and gives a family guideline of four hours at 121°C. It also directs processors to the individual grade's processing sheet and requires maintaining the moisture level during processing. Treat this as an illustration of measured residual-moisture control, not a universal dryer recipe or a replacement for current grade instructions. Celanese, Polyester Technical Manual, §§3.4–3.6

For process release, record the approved residual-moisture limit, measurement method, dryer conditions and material transfer arrangement. Distinguish dryer setpoint from measured pellet condition. Keep virgin material, approved regrind and mixed or unidentified material traceable separately; do not assign a permissible regrind percentage from the PBT name.

The same manual recommends sharp machining tools, chip clearance, work support and cooling; carbide can improve tool life with reinforced grades. Use these as starting principles, with cutting conditions qualified for the stock and operation. Celanese, §5.3

Service and approval limits

BASF explains that water, including atmospheric moisture, can split polyester chains, particularly at elevated temperatures. Hydrolysis stabilizers slow this degradation; they do not establish unlimited exposure. Its heat-aging temperature index represents a defined property loss over a defined time, rather than an unconditional operating temperature. Qualify the actual fluid, temperature, duration and mechanical loading together. BASF, pp. 20–21

Approval names also require current documentation. BASF's 13 May 2026 announcement distinguishes drinking-water Aqua grades from dedicated food-contact FC grades, and states that glass-fiber-reinforced Aqua grades will no longer carry food-contact certifications going forward. It names B4300G6 FC UN and B4300G6 FC BK15136 among the available certified food-contact grades. Obtain the applicable declaration and conditions for the exact product; neither “PBT” nor a similar grade name establishes compliance. BASF, portfolio update

Handling and qualification record

For its TECADUR PBT GF stock, Ensinger's handling sheet calls for minimizing machining dust, extraction or adequate ventilation, avoiding overheating and avoiding inhalation of dust or vapors. This article-handling document is specific to those stock products; obtain current grade-specific safety information for resin processing. Ensinger, PHIS V02, 23 April 2014, §§7–8

A useful release record identifies the exact material and process, the inspection conditioning state, the service exposure and the acceptance test. Preserve measured results separately from supplier typical values. A substitution should explicitly close those same questions before approval.

Source dates and related reference

The BASF brochure's closing note is dated August 2025. Celanese's manual says it was printed 19 September 2013; its current product overview displays no document revision date. The Ensinger technical sheet prints 19 July 2023, despite the generated filename containing 202610; the handling sheet prints 23 April 2014. Historical guidance remains useful context, but current ordering and processing documents govern the selected grade.

Material selection through production