For R&D material screening of high-performance thermoplastics (e.g., PEEK, PEI, PPS, PSU, PPA, LCP, PA46, PA66 high-temp grades, PVDF, etc.), the best free resources are usually a mix of:

1. broad materials databases
2. manufacturer datasheets
3. academic/property references
4. selection tools / ecosystem data
5. standards and test-method references

Here are the strongest options, grouped by usefulness.

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1) Best general-purpose free database: CAMPUS Plastics

Why it’s good:
CAMPUS is one of the most useful free resources for engineering thermoplastics. It provides standardized property data from participating suppliers, which makes comparisons more meaningful than comparing arbitrary PDFs.

What you get:

• Mechanical properties
• Thermal properties
• Electrical properties
• Flame ratings on some grades
• Processing info
• Comparable data format across suppliers

Best for:

• Shortlisting candidate resins
• Comparing grades across manufacturers
• Getting a first-pass view of property tradeoffs

Limitations:

• Coverage is not complete for all high-performance thermoplastics
• Some advanced or niche grades may be missing
• Data is supplier-submitted, so always verify with original datasheets

Search tip:
Use it especially for standard engineering grades, then move to supplier datasheets for the exact high-performance grade.

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2) Best source for exact grade details: Manufacturer technical datasheets

These are the most authoritative free sources for a specific resin grade.

Best suppliers to check:

• Victrex (PEEK/PAEK)
• SABIC (PEI, PPSU, PSU, LEXAN high-temp variants)
• Solvay (PPSU, PSU, PPA, fluoropolymers)
• Celanese (POM, PPA, PPS-related portfolios)
• BASF (PPA, polyamides, engineering plastics)
• DuPont (PPA, specialty polymers)
• Arkema (PVDF, specialty polymers)
• Ensinger / Röchling (semi-finished stock shapes; useful property summaries)
• Toray / Ube / Evonik / Sumitomo depending on polymer family

What to look for in datasheets:

• Tensile/flexural properties
• Heat deflection temperature (HDT)
• Glass transition temperature (Tg)
• Continuous use temperature
• UL 94 flammability
• Chemical resistance notes
• Moisture absorption
• Dielectric properties
• Creep/stress relaxation data
• Rheology / melt flow or viscosity
• Recommended processing window

Why they matter:
For high-performance thermoplastics, small formulation differences can matter a lot. A “PEEK” or “PPSU” family comparison is only useful at the exact grade level.

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3) Best free cross-comparison tool: UL Prospector (limited free access)

Why it’s useful:
Prospector has a broad resin and additive search ecosystem and is often very handy for finding comparable grades.

What you get:

• Resin property search
• Supplier comparisons
• Some datasheets
• Application filtering

Best for:

• Comparing multiple commercial grades quickly
• Identifying substitute materials
• Finding candidate compounds for screening

Limitations:

• Free access is limited
• Some features and deeper data are gated

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4) Best scientific reference database: MatWeb

Why it’s useful:
MatWeb is often the first place people go for quick property lookup across many material families.

What you get:

• Tensile, flexural, impact, thermal data
• Broad material coverage
• Fast lookup by polymer family or grade

Best for:

• Quick directional comparisons
• Screening unfamiliar families
• Getting a rough sense of property ranges

Limitations:

• Data quality varies by source
• Some entries are older or incomplete
• Use as a screening tool, not final specification source

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5) Best for open academic/technical comparisons: Google Scholar + review papers

For high-performance thermoplastics, review articles are extremely valuable because they compare:

• thermal stability
• mechanical retention at temperature
• creep
• tribology
• chemical resistance
• crystallinity/processability tradeoffs

Search terms to use:

• “PEEK PPSU PEI comparison review”
• “high performance thermoplastics property comparison review”
• “PEEK vs PPS creep thermal stability”
• “polyaryletherketone review”
• “high temperature thermoplastics chemical resistance review”

Why it matters:
Academic reviews often explain why a material behaves a certain way, which helps early screening and avoids chasing a high number in one property that fails in service.

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6) Best for standards and test context: ASTM / ISO method summaries and public guidance

You often can’t access full standards for free, but you can still use:

• test method summaries
• manufacturer references to methods
• university or lab guides explaining the tests

Why this helps:
Comparisons only make sense if you know whether values were measured under:

• dry-as-molded vs conditioned
• annealed vs unannealed
• standard vs high humidity
• short-term test vs long-term exposure
• specific test speed/load geometry

For high-performance thermoplastics, these context details are critical.

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7) Best for application-oriented screening: Supplier selection guides and design handbooks

Many suppliers publish free application guides like:

• material selection charts
• chemical resistance tables
• friction/wear tables
• electrical property guides
• flame and smoke guides
• high-temperature design recommendations

These are very useful when:

• screening for aerospace, medical, semiconductor, automotive, electrical, or chemical-processing use
• comparing polymers on service temperature, flame performance, and chemical exposure
• choosing between families like PEEK vs PEI vs PPSU vs PPS

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8) Best for finished-property comparison: Engineering handbook references

Free chapters, lecture notes, and older public-domain engineering references can be helpful for:

• baseline polymer family properties
• Tg/Tm ranges
• structure-property relationships
• typical service limits

Best use:
Conceptual comparison before you start narrowing down actual commercial grades.

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Recommended workflow for R&D screening

If you want a practical, efficient approach:

Step 1: Define the service envelope

Collect required minimums for:

• continuous use temperature
• peak temperature
• load/stress
• chemical exposure
• electrical/flame requirements
• dimensional stability / creep
• process constraints

Step 2: Use broad databases

Start with:

• CAMPUS
• MatWeb
• UL Prospector
  to generate a short list.

Step 3: Verify with manufacturer datasheets

Download exact grade datasheets for:

• your top 3–10 candidates
• dry vs conditioned values
• relevant test methods

Step 4: Use review papers and design guides

Validate:

• long-term behavior
• known failure modes
• processing sensitivity
• real-world application cases

Step 5: Build a screening matrix

Compare candidates on:

• Tg / Tm
• HDT / continuous use temp
• tensile modulus/strength
• creep/stress relaxation
• chemical resistance
• moisture uptake
• flammability
• dielectric performance
• processability
• availability/cost

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If you’re comparing specific families

Here are some common high-performance thermoplastic families and where free resources help most:

• PEEK / PAEK: supplier datasheets, review papers, MatWeb, CAMPUS
• PEI: SABIC data, MatWeb, chemical/flame guides
• PPS / PPSU / PSU: supplier app guides, Prospector, datasheets
• PPA / high-temp polyamides: BASF, DuPont, MatWeb, CAMPUS
• PVDF / fluoropolymers: Arkema, Solvay, chemical resistance guides
• LCP: supplier datasheets and comparison tables for dimensional stability and flow

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My short list of the best free resources

If I had to pick only a few:

1. CAMPUS Plastics — best standardized comparison tool
2. Manufacturer datasheets — best for exact grades
3. MatWeb — fast broad screening
4. UL Prospector — good for substituting and comparing grades
5. Google Scholar review papers — best for understanding tradeoffs and long-term behavior

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If you want, I can also give you:

• a ranked list by polymer family (PEEK, PEI, PPSU, etc.)
• a comparison spreadsheet template for material screening
• or a recommended screening matrix for aerospace, medical, electrical, or chemical applications.