Plastics FAQ Hubs — Technical Q&A by Material and Topic

These 25 FAQ hubs collect the most common technical questions engineers, buyers, and fabricators ask about engineering and industrial plastics. Each hub answers 10–15 questions with direct, specific answers — not generic overviews. Questions cover material properties, grade selection, machining parameters, chemical resistance, compliance status, dimensional behavior, and procurement. Every answer links to the relevant detail page for further reading.

The FAQ library is organized in two sections: questions by material and questions by topic (machining, buying, and FDA/food-grade compliance).

FAQ Hubs by Material

High-Performance Thermoplastics

PEEK FAQ — Polyether ether ketone questions covering: maximum continuous-use temperature (480°F), the difference between virgin PEEK and filled grades (GF30, CF30, ELS), whether PEEK is FDA approved (yes, USP Class VI), how PEEK machines compared to acetal, why PEEK is expensive, and when to choose PEEK over Ultem or Torlon. 10–15 questions answered with specific numbers and grade references.

Ultem (PEI) FAQ — Polyetherimide questions covering: FAR 25.853 qualification (inherent, no intumescent additive required), the difference between Ultem 1000 and Ultem 2300, autoclave cycle limits (2,000+ cycles at 121°C), transparency (amber — not optically clear), UL94 V-0 rating, and how Ultem compares to polycarbonate for elevated-temperature guards and enclosures.

Torlon (PAI) FAQ — Polyamide-imide questions covering: why Torlon requires post-cure (moisture drives imidization to full strength), the difference between Torlon 4203 and 4301, maximum continuous-use temperature (500°F), PV rating for bearing applications, machinability (excellent but requires sharp tools and dust extraction), and cost compared to PEEK and Vespel.

Vespel (PI) FAQ — Polyimide questions covering: why Vespel has no melt point (thermoset-like — sublimes above 600°C), the difference between SP-1, SP-21, and SP-22, continuous-use temperature (550°F, short-term to 900°F in inert atmosphere), why Vespel is the most expensive plastic in the line card, and applications where Vespel is the only plastic option.

PPS (Ryton) FAQ — Polyphenylene sulfide questions covering: inherent flame retardancy (no additive), moisture absorption (0.02% — lowest of any semi-crystalline thermoplastic), maximum continuous-use temperature (425°F), chemical resistance profile (near-universal below 392°F), machinability, and how PPS compares to PEEK for chemical pump applications.

Polysulfone FAQ — PSU and PPSU questions covering: the difference between Udel (PSU) and Radel (PPSU) — temperature (300°F vs 350°F) and autoclave durability; hydrolytic stability (why polysulfone doesn't degrade in steam the way polycarbonate does); transparency (amber — same as Ultem); NSF 61 listing for potable water; and medical sterilization cycle limits.

Engineering Thermoplastics

Delrin FAQ — POM questions covering: the difference between POM-H (Delrin) and POM-C (Acetron GP) — centerline porosity, FDA status; moisture absorption (0.2% — stable dimensions); max use temperature (180–200°F); machinability; and why acetal is preferred over nylon for tight-tolerance machined parts.

Nylon FAQ — Polyamide questions covering: cast nylon 6 vs extruded nylon 6/6 (cast for large sizes, low stress; 6/6 for higher stiffness); moisture absorption (2–9% — affects dimensions); oil-filled vs MoS₂-filled grades; max temperature (250°F for 6/6); FDA-approved grades; and when nylon beats acetal (toughness, large-diameter cost).

PET and PETG FAQ — Polyester questions: PET (Ertalyte) bearing grade vs PETG amorphous thermoform grade; Ertalyte creep and fatigue advantage over acetal; moisture absorption (0.2%); max temperature (210°F); FDA approval; and PETG thermoforming advantages.

Noryl FAQ — Modified PPO questions: what PPO/PS blending achieves; Noryl dimensional stability across humidity (0.07% vs ABS 0.3%); UL94 V-0 rating; max temperature (220°F); and when Noryl is preferred over ABS or polycarbonate for electrical enclosures.

Polyolefin & Commodity Thermoplastics

UHMW FAQ — Questions covering: why UHMW has low friction; virgin UHMW vs Tivar 1000; abrasion resistance vs nylon; FDA/USDA approval; machining deflection and fixturing; and max temperature (180°F).

HDPE FAQ — Questions covering: HDPE vs Marine HDPE (Starboard) — UV stabilizer and colorants; FDA approval; thermoforming and hot-gas welding; max use temperature (180°F recommended); and when to choose HDPE over UHMW.

LDPE FAQ — Questions covering: difference from HDPE (more flexible, lower density); FDA approval; low-temp toughness to −100°F; typical uses (gaskets, shims, flexible liners); and structural limitations.

Polypropylene FAQ — Questions covering: why PP is the lightest commodity plastic (0.905 g/cc); acid and base resistance; FDA/USDA compliance; hot-gas weldability; max temperature (180–200°F); and PP vs PVC for chemical tanks.

PVC FAQ — Questions covering: Type 1 vs Type 2 PVC; CPVC temperature advantage (200°F); expanded PVC (Sintra) vs solid PVC; chemical resistance; and why PVC is not FDA-approved for food contact in most stock forms.

ABS FAQ — Questions covering: what acrylonitrile, butadiene, and styrene each contribute; ABS-FR UL94 V-0 rating; thermoforming and paintability; and when to upgrade to polycarbonate or Noryl for higher temperature.

Fluoropolymers

PTFE (Teflon) FAQ — PTFE questions covering: why PTFE has the lowest coefficient of friction (µ = 0.05–0.10); cold flow under load and how filled grades (glass, carbon, bronze, MoS₂) address it; maximum temperature (500°F continuous); chemical resistance (inert to virtually all chemicals); FDA approval; and skived vs extruded film.

PVDF (Kynar) FAQ — PVDF questions covering: why PVDF has higher mechanical strength than PTFE (more crystalline structure); hot-gas and fusion weldability; chemical resistance to halogens and oxidizers; maximum temperature (300°F); UL94 V-0 inherent rating; and why PVDF is specified over polypropylene in semiconductor wet-bench applications.

Thermosets & Laminates

G10 and FR4 FAQ — Glass epoxy questions covering: the difference between G10 and FR4 (FR4 adds UL94 V-0 flame rating — same base material); NEMA grade designations; dielectric strength (800 V/mil); whether G10 and FR4 absorbs moisture (very low — less than 0.10%); machinability (carbide tools required, generates abrasive dust — respiratory precautions); and when to use G11 vs G10 (G11 for higher temperature, G11 is epoxy at 170°C Tg).

Phenolics FAQ (All Grades) — Covers all phenolic laminates: the difference between cotton (CE/C), linen (L/LE), canvas (C/CE), paper (XX/XXX/XXXP), and glass (G3/G5/G7/G9/G11) grades; NEMA grade designation system; oil impregnation of cotton grades; self-lubricating behavior; machinability; and how phenolics compare to engineering thermoplastics for bushing and gear applications.

FAQ Hubs by Topic

Machining Plastics FAQ

The most referenced general FAQ. Covers: cutting speeds and feeds for the most common materials (acetal, nylon, PEEK, polycarbonate, G10 and FR4); tool geometry (rake angle, clearance, relief); coolant selection (most plastics — air or mist; G10 and FR4 — water mandatory); fixturing strategies to prevent deflection of thin-walled parts; dimensional stability during machining (rough-cut and stress-relieve before finishing); and surface finish achievable by material.

Specific questions answered: "Can I use HSS tools on PEEK?" (yes, carbide holds edge longer); "Why does my acetal rod warp after machining?" (residual stress — allow 24 hours between roughing and finishing); "How do I machine thin-walled polycarbonate without cracking?" (sharp tools, low feeds, no chlorinated coolants); and "What RPM for drilling nylon?" (material- and diameter-specific table provided).

Buying Plastics FAQ

Procurement-focused questions covering: minimum order quantities (MOQs) for sheet, rod, and tube; how custom cut-to-size pricing works; lead times for standard vs special orders; what a Certificate of Conformance (C of C) covers; the difference between "FDA-grade" material stock and a compliance certification for a finished part; how to specify material on a drawing (ASTM, NEMA grade, or trade name); and availability of material certifications (mill cert, NEMA conformance, USP Class VI test reports). Also covers blanket orders, urgent shipments, and documentation provided with each order.

FDA & Food-Grade Plastics FAQ

Compliance-focused questions covering: which 21 CFR sections apply to which materials (177.1520 polyolefins, 177.2470 nylon, 177.1650 PTFE, 181.22 acetal); the difference between "FDA-compliant material" and "food-contact certified part"; what NSF 51 and NSF 61 cover (food equipment vs potable water); USDA vs FDA approval; 3-A Sanitary Standards for dairy; whether all natural-color plastics are food-grade (no — compliance is material- and grade-specific); and what documentation is available for food-grade orders.

Navigating the FAQ Library

Each FAQ hub is self-contained — you can read it independently without reading the full material hub. However, every answer links to the relevant detail page (properties, machining, grades, or applications) when a question merits more depth than the FAQ format allows.

If you don't find your question in the FAQ hubs, check the material hub pages, which include a comparisons section addressing the most common selection trade-offs. For application-specific questions, the Applications index organizes guidance by use case rather than by material.