PBT injection molding shows up on electrical connectors, bobbins, and under-hood parts that need heat, stiffness, and dimensional stability better than commodity nylon in some environments — and a different shrink and moisture story. OEMs who specify “PBT or nylon” as if they were colors discover warp and CTQ misses at T1.
This guide is the OEM callout: unfilled vs GF PBT, drying, anisotropy, vs nylon/POM, and RFQ language. Family map: material classification. Fiber-filled behavior overlaps glass filled nylon even though the chemistry differs.
When PBT is the rational pick
| Need | PBT | Often better |
|---|---|---|
| Electrical housings, connectors | Strong default, including FR grades | — |
| Low moisture swell vs PA6 | Usually better dimensional stability in humidity | POM if friction/gears dominate — POM |
| High impact at low temp | Validate grade | PC, PC/ABS — PC/ABS |
| Living hinge | Poor | PP |
| Flame rating | FR PBT common | Confirm UL on the color — FR plastics |
Lock manufacturer grade, GF %, color, and FR listing. “Natural PBT” substitutions change shrink and CTI.
Process and DFM that bite on PBT-GF
- Dry thoroughly — PBT is moisture-sensitive in the barrel (splay, hydrolysis risk)
- Fiber orientation drives warp; gate for the CTQ axis — gates, warpage
- Tool wear on GF: steel and sliders — steel, actions
- Weld lines on connector walls are structural — weld lines
- Shrink map is not ABS — shrinkage
Draft and texture still apply: draft. Electrical programs: electrical enclosure OEM.
PBT vs nylon vs POM — short OEM table
| PBT | PA6/PA66 | POM | |
|---|---|---|---|
| Moisture swell | Lower than PA | High; condition | Very low |
| Friction / gears | OK filled | Needs grades | Often first choice |
| Electrical / FR | Very common | Common | Less typical for FR housings |
| Process window | Dry + fiber warp | Dry + moisture after | Degradation / odor risk |
Do not qualify in PA66 and production-release in PBT-GF30 without a new tool shrink and warp plan.
RFQ callouts
- Grade + GF + color + UL/CTI if electrical
- Mating pin/connector CTQs and measurement method
- Chemical / heat duty (under-hood vs indoor)
- Secondary: ultrasonic, screws, potting — ultrasonic welding
DFM: checklist. Samples: T0–T2.
How Deuchi molds PBT
Deuchi treats PBT-GF as a drying-and-orientation resin. We will recommend gate and steel changes when the CAD is a GF warp trap. We will not swap nylon and PBT after steel to “save resin.” Contract manufacturing for production; send CAD via contact.
FAQ
Does PBT need drying like PC?
Yes — follow the datasheet. Wet PBT is not a cosmetic-only problem.
Can we paint PBT housings?
Sometimes; adhesion and residual stress need a trial. Many electrical parts stay as-molded color.
Is PBT good for living hinges?
No. Use PP or a two-part design.
Why is our PBT connector warped?
Usually GF orientation + uneven cooling + a gate that fills one way. Fix gate and thickness before blaming the operator.
Next step: Contact Deuchi with CAD, PBT grade (or PA/PBT question), and electrical/FR needs for a DFM-backed quote.