How do you calculate moisture sensitivity risk?

Multiply the severity, occurrence, and detection scores together. The default 8 x 6 x 5 yields a moisture sensitivity risk score of 6.55 on the calculator's normalized scale, flagging a high-priority material for drying control.

What is a good moisture sensitivity risk score?

Lower is better. There is no universal threshold, but rank your materials and treat the top quartile as priority. A grade scoring near the 6.55 example sits well above a grade scoring 1-2 and should get desiccant drying and dew-point monitoring first.

Why does detection matter for biopolymer moisture risk?

Because hydrolysis often leaves no visible defect — parts look fine but fail on tensile or impact. A high detection score (here 5) means damage slips past inspection, which is exactly why moisture-sensitive resins need upstream moisture analysis rather than end-of-line checks.

Severity vs occurrence vs detection — which should I cut first?

You usually cannot change severity (it is the material's chemistry), so attack occurrence with better drying and sealed handling, and attack detection with in-line moisture or melt-flow monitoring. Both directly pull the 6.55 score down.

Can I compare PLA and PHA with this score?

Yes, as long as you score both on the same severity, occurrence, and detection scale. The score is built for ranking grades against each other so you can target the most moisture-fragile material first.

How does this relate to a standard FMEA RPN?

It is the same severity x occurrence x detection logic used in process FMEAs, focused specifically on moisture. Use it as the moisture line item within a broader biopolymer process FMEA.

Bioplastics & Biomaterials Processing calculator

Moisture Sensitivity Risk Calculator

Moisture Sensitivity Risk is an FMEA-style risk priority number for hygroscopic biopolymers like PLA, PHA, PBS, and starch blends, where absorbed water causes hydrolytic chain scission, splay, voids, and lost mechanical properties during melt processing. It multiplies how bad a moisture defect is (severity), how often it happens (occurrence), and how hard it is to catch before the part ships (detection), so process and quality engineers can rank which materials and lines need tighter drying control. Because moisture damage in biopolymers is often invisible until tensile testing, the detection axis carries real weight here. Teams use the score to prioritize desiccant dryer upgrades, in-line moisture analyzers, and incoming-resin holds.

What this calculator does

Score moisture-related processing risk for PLA, PHA, starch blends, cellulose compounds, and other hygroscopic biomaterials using severity, occurrence, and detection ratings.
a polymer processing team needs to rank moisture risk before running or qualifying a bio-resin grade
It computes a moisture risk priority number by multiplying severity, occurrence, and detection scores for a hygroscopic material or process.

Formula used

Moisture sensitivity risk score = moisture impact severity score × moisture occurrence score × moisture detection score
Use the same scoring scale across comparable moisture-sensitive materials and processes.

Inputs explained

Moisture impact severity score:
Moisture occurrence likelihood score:
Moisture detection difficulty score:

How to use the result

Use it when prioritizing drying controls, comparing moisture risk across biopolymer grades, or building an FMEA for a new bio-based line.
The score is only meaningful when every material is rated on the same consistent scale; raw magnitude is less informative than the rank order it produces.

Current U.S. benchmarks

The producer price index for plastic resins and materials stands at 319.371 (BLS, May 2026), up 19.5% from a year earlier. Quotes priced off last quarter's material cost miss this move.

Common questions

How do you calculate moisture sensitivity risk? Multiply the severity, occurrence, and detection scores together. The default 8 x 6 x 5 yields a moisture sensitivity risk score of 6.55 on the calculator's normalized scale, flagging a high-priority material for drying control.
What is a good moisture sensitivity risk score? Lower is better. There is no universal threshold, but rank your materials and treat the top quartile as priority. A grade scoring near the 6.55 example sits well above a grade scoring 1-2 and should get desiccant drying and dew-point monitoring first.
Why does detection matter for biopolymer moisture risk? Because hydrolysis often leaves no visible defect — parts look fine but fail on tensile or impact. A high detection score (here 5) means damage slips past inspection, which is exactly why moisture-sensitive resins need upstream moisture analysis rather than end-of-line checks.
Severity vs occurrence vs detection — which should I cut first? You usually cannot change severity (it is the material's chemistry), so attack occurrence with better drying and sealed handling, and attack detection with in-line moisture or melt-flow monitoring. Both directly pull the 6.55 score down.
Can I compare PLA and PHA with this score? Yes, as long as you score both on the same severity, occurrence, and detection scale. The score is built for ranking grades against each other so you can target the most moisture-fragile material first.

Last reviewed 2026-05-12.