The short answer
Acrylic gives the best clarity, scratch resistance and outdoor life. Polycarbonate is the choice when a clear part must survive impact or more heat. Copolyester is a tough, chemical-resistant clear option, common in food and medical parts. SAN and polystyrene are low-cost and clear but brittle. Clarified PP and PET give cheap, chemically resistant clarity in thin walls. Polysulfone and PEI are amber, but they take hot water and steam.
Choosing a clear resin is a trade between optics, toughness, scratch resistance, chemical resistance and UV life. No single resin wins all of them. Clarity also depends on molding: a good resin molded wet or with high stress gives hazy, crazed parts.
Clear plastics compared
| Resin | Light transmission (typical) | Impact (notched Izod) | Scratch resistance | UV / outdoor | Cost tier | Common 21 CFR section |
|---|---|---|---|---|---|---|
| Acrylic (PMMA) | ~92% | Low (15–25 J/m) | Best of the common clear plastics | Excellent | Moderate | 177.1010 |
| Polycarbonate (PC) | ~88–90% | Very high (600–900 J/m) | Poor without a hard coat | Yellows unless UV-stabilized | Moderate to high | 177.1580 |
| Copolyester (PETG-type and others) | ~88–91% | Good to very good | Fair | Fair; UV grades for outdoors | Moderate | 177.1315 for PETG-type; others vary |
| PET (amorphous, bottles, sheet) | ~88–90% | Good in bottles and film | Fair | Fair | Low | 177.1630 |
| SAN | ~88–90% | Low (15–30 J/m) | Good | Yellows in sunlight | Low to moderate | 177.1040 |
| GPPS | ~88–90% | Very low (15–25 J/m) | Fair | Poor; yellows | Low | 177.1640 |
| Clarified random copolymer PP | High in thin walls, but hazy (~10% haze at 1 mm in good grades) | Moderate | Poor | Needs UV stabilizer | Low | 177.1520 |
| Transparent nylon (amorphous or microcrystalline) | ~88–92%, grade dependent | Good | Fair | Fair to good | High | 177.1500 or FCN, grade dependent |
| Polysulfone (PSU) | ~80–85%, amber | Moderate (65–70 J/m) | Fair | Fair | High | 177.1655 |
| PEI | Lower, deep amber | Moderate (50–60 J/m) | Fair | Fair | High | 177.1595 |
Typical values for general-purpose clear grades, measured on molded plaques (usually about 2–3 mm) by ASTM D1003; individual grades vary, and transmission drops with thickness and tint. The 21 CFR section is the usual one for the family; food-contact status belongs to the specific grade and its producer’s letter, and the finished article is the manufacturer’s responsibility.
Transmission and haze
Light transmission is the share of visible light that passes through. Haze is the share of that light scattered more than 2.5° from straight through, which makes a part look milky. Both are measured by ASTM D1003 at a stated thickness. A clear part for a lens or display cover usually needs haze under about 2%. Amorphous resins (PMMA, PC, copolyester, SAN, PS, PSU) are clear because they have no crystals to scatter light. Semi-crystalline resins (PP, PET, nylon) are clear only when crystals are kept small with clarifiers, or prevented by fast cooling or copolymer chemistry. See amorphous vs. semi-crystalline plastics.
Polycarbonate and acrylic
Acrylic transmits about 92% of light, is the hardest-wearing of the common clear plastics and weathers for years outdoors without yellowing. It is brittle, and solvents and alcohols craze it. Impact-modified grades are several times tougher and still clear, but well below PC. See acrylic.
Polycarbonate transmits about 88–90% and has very high impact strength and an HDT around 124–132°C (255–270°F). It scratches easily without a hard coat, yellows outdoors unless UV-stabilized, and stress-cracks with many cleaners and solvents. See clear polycarbonate and polycarbonate vs. acrylic.
Copolyester, PET, SAN, polystyrene and clear PP
Copolyester covers PETG-type grades and higher-heat types. It is tough, clear and resists many cleaners and disinfectants better than PC, and it does not contain BPA. PETG-type grades soften at lower temperatures than PC, so check heat limits. It is common in food storage, cosmetic packaging, medical housings and displays. See best plastic for food containers.
PET is clear when it is amorphous (bottles, film and sheet) and opaque when crystallized. Bottle and sheet grades are rarely used for thick injection-molded parts.
SAN is stiffer, harder and more chemical resistant than polystyrene and is used for housewares, cosmetic jars and appliance windows. GPPS is the cheapest clear resin, with good optics, but it is brittle and attacked by many solvents. See ASA and SAN.
Clarified random copolymer PP is near-clear in thin walls, very low cost and resistant to most household chemicals, and it is widely used for dishwasher- and microwave-safe housewares. It is not optically clear like acrylic or PC, and the haze increases with thickness.
Amber and specialty clear resins
Polysulfone and PEI are transparent amber. They are chosen for heat, hot water and steam sterilization rather than optics: sight glasses, medical trays, dairy and coffee equipment. Transparent nylons combine clarity with better chemical resistance than PC or acrylic, at a higher cost, and are used for filter bowls, sight glasses and eyewear frames. See polysulfone and PPSU.
Molding clear parts
- Dry the resin. PC at about 120°C (248°F), PMMA at about 70–98°C (158–208°F), PETG-type copolyester at a lower temperature, often about 65°C (149°F), because it softens at its low Tg. Wet resin gives splay and haze. See the drying guide.
- Keep it clean. Purge thoroughly, use clean regrind or none, and watch residence time. Black specks and yellowing show at once in clear parts.
- Lower stress. Higher melt and mold temperatures, moderate packing and annealing reduce molded-in stress, which causes crazing and birefringence.
- Mind the flow. Flow lines, weld lines and jetting are all visible. Gate into a thick section and polish the steel.
What to send us for a quote
- The grade you run now, or the part and its clarity requirement
- Impact, heat, chemical and outdoor exposure
- Food-contact, medical or flame rating needs
- Wall thickness and process (injection, sheet, blow molding)
- Quantity for this order and per year, and ship-to city
Common questions
What is the clearest plastic?
Acrylic (PMMA), at about 92% light transmission, with very low haze. Polycarbonate, PET, copolyester, SAN and general-purpose polystyrene follow at roughly 88–91% in typical clear grades.
Which is better for clear parts, polycarbonate or acrylic?
Acrylic for optics, scratch resistance and outdoor exposure. Polycarbonate when the part may be hit, since it is far tougher, or when it needs more heat resistance. Polycarbonate needs a hard coat for scratch resistance and UV stabilization outdoors.
Is there a clear polypropylene?
Yes. Clarified random copolymer PP is close to clear in thin walls, with haze around 10% at 1 mm in good grades. It is not glass-clear like acrylic or PC but is cheap, chemically resistant and used for food containers, caps and housewares.
What clear plastic resists chemicals?
Among clear resins, PET, copolyester and clarified PP resist cleaners and many chemicals better than polycarbonate, acrylic or polystyrene. Polysulfone and PEI handle hot water and steam but are amber in color.
Why do clear parts crack or craze?
Usually molded-in stress plus contact with a solvent, cleaner or alcohol. Polycarbonate, acrylic and polystyrene are most prone. Lower stress (higher melt and mold temperature, annealing) and a chemical test on stressed parts reduce it.
Which clear plastic does not yellow outdoors?
Acrylic has the best natural UV stability. Polycarbonate needs a UV-stabilized grade or a UV-protective cap layer or coating, and polystyrene and SAN yellow fairly quickly in sunlight.
Why do clear parts come out hazy or with streaks?
Wet resin causes splay and haze, especially in PC, PET and copolyester. Contamination, degraded material from long residence and low mold temperature also show up immediately in clear parts.
Tell us about the clear part
A polymer chemist reviews every request, then matches your grade or finds a qualified equivalent and prices it.
What to send for an accurate quote
- The grade name, from any supplier, or a data sheet
- Color (natural, black or a custom match)
- Fill type and percentage, if any
- Melt flow, if you know it
- Quantity for this order and what you use in a year
- Ship-to city and state or province