Dongying (Suzhou Dongying Electronic Technology Co., Ltd.) is a mold maker and injection molder in Suzhou, China. We build precision molds and run insert molding for overseas procurement, R&D and quality teams, including busbar insulation components. Projects use one of two delivery modes: mold handover, or Dongying holds the mold and supplies parts. For what to send in an inquiry, start with busbar insert molding RFQ inputs; see also the busbar category.
Common overmold plastics at a glance
Short answer: PA66-GF is the tough, heat-capable workhorse that needs moisture planning; PBT-GF is dimensionally steadier in humid air but needs care in hot-humid duty; PPS suits high heat and aggressive media; PPA bridges high temperature with better humidity retention than standard PA66.
| General trend (grade-dependent) | PA66-GF | PBT-GF | PPS | PPA / high-temp PA |
|---|---|---|---|---|
| Heat in continuous service | Good for many power and EV busbar housings | Good for moderate heat; check HDT | Very high; often when heat and chemicals both matter | Higher than PA66 when PA66 softens or absorbs too much water |
| Moisture after molding | High; size and stiffness shift | Low | Very low | Lower than PA66; still check chemistry |
| Electrical insulation | Strong when dry; CTI/flame are grade-specific | Favored for stable walls around conductors; CTI/flame grade-specific | Good heat-plus-electrical balance in many grades | Often used where dielectric properties must hold in heat and humidity |
| Chemical / coolant | Many automotive fluids OK by grade; confirm coolants | Hydrolysis risk in hot humidity unless HR grade | Strong chemical resistance in many grades | Good resistance to challenging media in many grades |
| Mold / process | Dry thoroughly; anisotropic glass shrink | Dry thoroughly; glass orientation drives warpage | Higher melt temperatures; design for the grade | Higher mold/melt temps than PA66; different shrink family |
Trends only—compare datasheets for the exact grades you shortlist, including thickness-dependent flame and tracking data.
PA66-GF for overmolded busbars
Short answer: glass-filled PA66 is a common EV busbar plastic when toughness and heat resistance are needed, provided moisture-related property change is designed in and measured correctly.
BASF positions Ultramid polyamides for electrical and automotive parts needing strength, rigidity and thermal stability, including glass-fiber grades (BASF Ultramid). DuPont design information on Zytel and Minlon explains that polyamides absorb moisture after molding, enlarging parts, lowering stiffness and raising toughness; the change is slow and reversible (DuPont design module via Distrupol). A dry-as-molded insulation wall is therefore not the same part after weeks in humid air.
Agree whether critical dimensions are checked dry-as-molded, after conditioning, or both. Prefer a named PA66-GF grade or approved alternates, and confirm flame or tracking needs against your product standard—not a supplier promise.
PBT-GF for busbar housings
Short answer: glass-filled PBT is often chosen for a PBT busbar housing when low moisture uptake and dimensional stability around inserts matter more than PA66-level toughness.
BASF’s Ultradur PBT line highlights rigidity, dimensional stability under heat, low water absorption and use in electrical housings and connectors (BASF Ultradur). Standard PBT’s weak point is hydrolysis when heat and moisture combine; BASF notes that humid air at elevated temperature can cleave polyester chains, which is why hydrolysis-resistant (HR) grades exist (BASF, Hydrolytically Stable PBT; BASF, Avoiding Moisture Damage). LANXESS Pocan HR guidance likewise frames HR PBT for hot-humid automotive electronics (LANXESS via ALBIS).
Glass fibers align with flow, so shrinkage differs along and across flow—a common warpage driver in 30% glass PBT (Sales Plastics). On a busbar overmold that appears as uneven walls over the insert, flash at shut-offs, and seating features that no longer match the assembly.
PPS for high-heat overmolded busbars
Short answer: PPS is a candidate when an overmolded busbar sees higher continuous temperatures or chemically aggressive environments that push PA66 and standard PBT outside their comfort zone.
PPS is associated with high heat resistance, low moisture absorption and strong chemical resistance (Ensinger). Insert molding usually means higher melt temperatures than PA66 or PBT, planned insert preheating, and a mold cut for that grade’s shrinkage and flow. Reinforced and specialty electrical grades differ widely, so freeze brand and grade before steel is cut.
If coolants or battery chemicals contact the housing, ask the resin supplier for exposure data on the exact grade. Dongying can evaluate insert-molded designs in candidate grades; metal conductor stamping, if part of a package, can be assessed separately and is not assumed.
PPA and high-temperature PA for insert molding
Short answer: PPA insert molding is considered when PA66 loses too much stiffness or dielectric margin in heat and humidity, and the program can accept higher material and processing cost.
BASF’s Ultramid Advanced PPA portfolio describes partially aromatic polyamides that keep mechanical properties at elevated temperature, take up less water than PA66, and hold strength and dimensional stability in humid or chemically demanding E&E and e-mobility parts (BASF Ultramid Advanced). Solvay/Syensqo Amodel literature similarly stresses high strength at high temperature and property retention in humidity and aggressive media (Solvay Amodel overview; Nexeo Plastics). EMS Grivory also offers high-performance polyamide families for demanding technical parts (EMS Grivory).
PPA is not automatically better than PA66-GF or PBT-GF—it is a different shrinkage and process window. If both remain open, decide before cavity steel is cut.
How material choice changes the mold
Short answer: shrinkage, insert heating, gating, venting and flash control at the insert all depend on the resin family, so freeze the grade—or at least the shrinkage family—before the mold is designed.
| Mold item | Why the material matters |
|---|---|
| Shrinkage allowance | Grades shrink differently along and across flow; a late switch can mean steel rework. |
| Insert heating | Cold inserts can cause short shots, weld lines or sink at the plastic–metal interface. |
| Gate position and type | Sets flow around the conductor, weld-line location and pressure at thin insulation walls. |
| Venting | Fast-filling or high-temperature grades need vents where air would trap at insert edges. |
| Shut-offs / flash at inserts | Over-packing thin walls can flash onto plating or into functional gaps. |
| Drying | Wet PA66 or PBT degrades in the barrel; follow the grade’s drying window. |
Run mold-flow with the actual grade when geometry is complex. See mold making, manufacturing and tooling and supply scope.
What to put in the RFQ for material
Short answer: give operating conditions, preferred grades and how acceptance is measured; treat voltage class, flame rating and tracking needs as customer-specified inputs, not as supplier guarantees.
- Continuous and peak operating temperature, plus any hot-humid or thermal-shock tests in your specification.
- Environment: dry indoor, under-hood, coolant or fluid splash—name fluids if known.
- Preferred grade and approved alternates (brand and grade), color, and any UL 94 flame rating your product standard requires at the wall thickness you use (UL describes UL 94 small-scale flame classifications for plastics; specify class and thickness) (UL).
- Tracking / creepage expectations from your insulation coordination: IEC 60112 defines how comparative tracking index (CTI) is measured; UL offers CTI testing to that method—state the CTI or material group your design assumes, without treating a molder’s quote as a certified value (IEC 60112; UL CTI).
- Insert metal alloy, plating or coating, and any restriction on flash onto plated surfaces.
- Critical insulation walls and whether dimensions are measured dry or conditioned.
- Annual volume, and mold handover versus Dongying-held mold with part supply.
For drawing control and sample review, see drawings and revisions and inspection and approval. When ready, send the package or review quality expectations.
FAQ
What is the best busbar overmolding material?
There is no single best grade. PA66-GF suits many tough, heat-exposed overmolds if moisture change is planned. PBT-GF suits housings that need stable dimensions in humid air, with HR grades when heat and humidity combine. PPS suits higher heat and aggressive chemicals. PPA suits cases where PA66 loses too much performance in heat and humidity. Confirm the shortlist with datasheets and your own product tests.
Is PA66-GF or PBT better for an EV busbar plastic housing?
It depends on temperature, humidity and mechanical load. PA66-GF usually offers higher toughness and heat capability but absorbs more water, so size and stiffness drift. PBT-GF absorbs little water and holds dimensions better, but standard PBT can hydrolyze in hot humidity unless an HR grade is used. Compare both against your thermal, humidity and mechanical test plan, including the moisture state of dimensional checks.
When should I consider PPS for an overmolded busbar?
Consider PPS when continuous temperature, chemical exposure or a combination of both exceeds what approved PA66 or PBT grades can support on the datasheet and in your tests. PPS typically brings high heat resistance, low moisture uptake and strong chemical resistance, at higher melt temperatures and often higher material cost. Freeze the exact PPS grade before mold design, because filled and unfilled grades process differently.
What does PPA add compared with PA66 for insert-molded busbars?
PPA (polyphthalamide) and related high-temperature polyamides generally retain stiffness and strength better than PA66 at elevated temperature and take up less moisture, which helps dimensional and dielectric stability in humid service. The trade-offs are higher material cost and a different process and shrinkage window. Use PPA when PA66 fails your heat-plus-humidity requirements, not as a default upgrade.
Which electrical ratings should I specify for overmolded busbar material?
Specify what your product standard and insulation coordination require: for example a UL 94 flame class at a stated thickness, and a CTI or material group expectation tied to creepage design. UL 94 classifies small-scale burning behavior of plastic specimens; IEC 60112 defines CTI measurement. Ask suppliers for grade datasheets and recognized certifications for those properties, and treat them as inputs to your design review rather than as a molder performance guarantee.
What should I send to discuss insert-molded busbar materials and tooling?
Send the 3D model and drawing, operating and peak temperatures, environment and fluids, preferred and alternate grades, any flame or tracking requirements from your standard, insert metal and plating, critical insulation walls, annual volume, and whether you want mold handover or part supply from a Dongying-held mold. With those inputs we can comment on moldability and the tooling approach; see also our RFQ inputs article for the full inquiry checklist.
Related pages
Sources
- BASF, Ultramid (PA) product overview: https://plastics-rubber.basf.com/global/en/performance_polymers/products/ultramid
- BASF, Ultradur (PBT) product overview: https://plastics-rubber.basf.com/global/en/performance_polymers/products/ultradur
- BASF, Ultramid Advanced (PPA) portfolio: https://plastics-rubber.basf.com/global/en/performance_polymers/fpgs/polyphthalamides
- BASF, "Avoiding Moisture Damage" (PBT / polyester hydrolysis): https://download.basf.com/p1/8a8081c57fd4b609017fdf6da526231c/en/Avoiding_Moisture_Damage
- BASF, "Hydrolytically Stable PBT": https://download.basf.com/p1/8a8082587fd4b608017fd64802d53aad/en/Hydrolytically_Stable_PBT
- DuPont, Minlon and Zytel Design Information, Module II (PDF hosted by Distrupol): https://www.distrupol.com/Minlon_Zytel_Design__Info_Module_2.pdf
- LANXESS, "Pocan HR – Improved Hydrolysis Resistance" (PDF hosted by ALBIS): https://www.albis.com/dam/jcr:daeb9e72-d470-4abd-8029-fd05fb5f37a0/LANXESS_-_Pocan_HR_%E2%80%93_Improved_Hydrolysis_Resistance_-_LXS-HPM-072EN_-_2017-10.pdf
- Sales Plastics, "PBT Injection Molding: Preventing Warpage in 30% GF": https://salesplastics.com/pbt-injection-molding-preventing-warpage-30-gf/
- Ensinger, PPS plastic overview: https://www.ensingerplastics.com/en-us/shapes/high-performance-plastics/pps
- Solvay, Amodel PPA Overview (PDF): https://www.solvay.com/sites/g/files/srpend616/files/tridion/documents/Amodel-PPA-Overview_EN.pdf
- Nexeo Plastics, Amodel PPA product summary: https://www.nexeoplastics.com/supplier-products/syensqo/amodel
- EMS Grivory, high-performance polymers: https://www.emsgrivory.com/en/
- IEC, IEC 60112 Method for the determination of the proof and the comparative tracking indices of solid insulating materials: https://webstore.iec.ch/en/publication/5997
- UL Solutions, Comparative Tracking Index (CTI) IEC 60112: https://www.ul.com/services/comparative-tracking-index-cti-iec-60112
- UL Solutions, Combustion (Fire) Tests for Plastics (UL 94 classifications): https://www.ul.com/services/combustion-fire-tests-plastics
- UL Code Authorities, "Understanding UL 94 Rating Certifications and Limitations": https://code-authorities.ul.com/about/blog/understanding-ul-94-rating-certifications-and-limitations/