Here's the catch: there's no single correct PHR number. The right dosage depends on your PVC resin, the application, your equipment, your processing history, and the performance your end product needs to deliver. A pipe compound and a wire insulation compound don't share a dosage, even if both use calcium-based stabilizers.
This guide defines PHR, breaks down starting ranges by application, explains how to calculate and adjust dosage, and shows how to validate a stabilizer one-pack before you commit to production.
Key Takeaways
- PHR means parts of additive per 100 parts of PVC resin, not percent of the finished compound.
- Dosage depends on application, resin grade, filler/plasticizer loading, processing conditions, and target performance.
- Pipe, profiles, foam, cable, flooring, and flexible goods each demand a different stabilizer-lubricant balance.
- A one-pack's stated dosage often includes lubricants and processing aids, not just active stabilizer.
- Always confirm starting dosage through lab testing, trials, and supplier technical support.
What PHR Represents in PVC Stabilizer Formulation
PHR stands for parts per hundred resin. The PVC resin is always treated as the fixed 100-part baseline, regardless of how much filler, plasticizer, pigment, or impact modifier you add to the recipe.
Peer-reviewed PVC formulation research confirms this definition: additive loadings are expressed as parts per 100 parts of resin, with resin as the denominator in every calculation.
Say you're compounding 100 kg of PVC resin and your formulation calls for 3 PHR of a calcium-based stabilizer one-pack. That means 3 kg of stabilizer goes into the mix, regardless of how much filler or plasticizer you also add.
PHR is not wt% of the total compound. If that same 100 kg of resin also contains 40 PHR of filler and 50 PHR of plasticizer, total recipe mass is 193 kg (100 + 3 + 40 + 50). To convert PHR into wt% of the finished compound, divide the stabilizer's PHR by the sum of all PHR values in the recipe (resin at 100 plus every additive), then multiply by 100: 3 ÷ 193 × 100 ≈ 1.55 wt%.
Why "Stabilizer Dosage" Can Mean Two Different Things
When someone says "stabilizer dosage," they might mean:
- Active stabilizer content — just the calcium-zinc or calcium-based stabilizing compound itself
- Total one-pack dosage — the full package, which can include internal and external lubricants, processing aids, UV support, or impact modifiers
A one-pack with built-in lubrication may carry a higher total PHR than a bare stabilizer system, even though the active stabilizer content is similar. Always check which figure you're comparing.
Factors That Influence the Required PHR
Several variables shift where you should start:
- Resin and recycled content — K-value, contaminants, residual moisture, and prior heat history all affect baseline stability. Recycled-content formulations often need re-evaluation, not a straight substitution.
- Processing conditions — Melt temperature, residence time, shear, line speed, screw design, and the number of heat histories a compound sees all change stabilizer demand.
- Formulation composition — Filler type, surface treatment and moisture content, plasticizer type and loading, pigments, impact modifiers, and foaming agents can all shift the required stabilizer-lubricant balance.
PVC Stabilizer Dosage by Application
Dosage figures should come from current supplier technical data sheets, your own formulation trials, and relevant application standards. Use the application notes below as starting points for discussion with your stabilizer supplier, not as guaranteed production settings.
Rigid Pipe, Conduit, and Fittings
Pressure pipe, DWV pipe, electrical conduit, and injection-molded fittings each carry distinct performance requirements under standards like ASTM D1784, D2241, and D2665. None of these standards publish a universal stabilizer PHR; they classify compounds by physical performance instead.
What shifts your starting dosage:
- Pipe diameter and wall thickness
- Single- versus twin-screw extrusion equipment
- Residence time and output rate
- Filler level and fusion behavior
- Plate-out tendency on calibration tooling
- Required pressure or impact ratings
IKAvin's pipe and conduit families illustrate why this split matters: IKAstab HGS 2000 is formulated for conduit applications, while IKAstab HGS 2700 targets pressure and non-pressure pipe. IKAstab HGS 9100 serves injection-molded fittings. These are application-specific examples, not interchangeable catalog numbers.
Profiles, Fenestration, Siding, Fence, Trim, and Foam Board
Window profiles, siding, fence, trim, and foam or Celuka board all demand different balances of color hold, weatherability, weld strength, melt strength, cell structure, and surface finish. A window profile exposed to years of UV and thermal cycling needs a different package than an interior trim piece.
A few practical distinctions:
- One-packs containing impact modifiers, flow promoters, or foaming support typically carry a higher total PHR than a stabilizer-and-lubricant-only package.
- Foam board formulations need stabilizer systems that support consistent cell structure and density, not just color retention.
- Weatherability requirements for exterior profiles go beyond what a processing heat stabilizer alone can guarantee.
IKAvin's HGS 5300 targets window profiles, HGS 5100 serves technical profiles, and HGS 1000 is built for siding and fence substrate. The HGS 6100/8100 pair splits between rigid foam and rigid vinyl sheet. Each reflects a different starting formulation, not a single universal dosage.
Flexible Wire, Cable, Hose, Tube, and Molded Goods
Wire and cable compounds balance heat aging, electrical performance, flexibility, and insulation or jacketing requirements under standards such as ASTM D2219 and UL 62/83. These standards define performance thresholds, such as tensile strength retention after oven aging, but don't publish a transferable stabilizer PHR.
Key variables that move the starting dosage:
- Plasticizer type and loading
- Service temperature and expected heat aging
- Migration resistance (especially relevant for medical or food-contact applications)
- Required clarity and softness
- Residence time in extrusion or molding equipment
Don't assume a cable insulation formula will work for general-purpose hose or tubing. IKAvin separates these: HGS 5200 for wire sheathing and jacketing, HGS 4100 for wire insulation, and HGS 3400 for specialty wire and cable. A separate general-purpose flexible line covers hose, tube, and molded goods.
Flooring, Calendered Film, and Other Surface-Critical Products
LVT, resilient flooring, sheet vinyl, wear layers, and calendered film all go through repeated thermal exposure during calendering and lamination. That extended heat history, combined with filler and pigment loading, changes the required stabilizer-lubricant balance compared to a single-pass extrusion process.
Surface-critical products prioritize:
- Long-term color hold through multiple heat histories
- Low odor for interior applications
- Minimal plate-out on calender rolls
- Lamination compatibility with wear layers and backing
IKAvin's HGS 9400 is formulated for resilient flooring and HGS 9900 for cushioned vinyl flooring, reflecting the different thermal exposure each product type sees. A dedicated specialty line, HGS 7100, covers clear films, membranes, and other surface-critical products like vinyl records, where even minor discoloration is unacceptable.
How to Set and Validate the Right Dosage
Treat dosage selection as a formulation and scale-up process, not a lookup table. Establish a technically justified starting point, test within a defined trial matrix, and select the lowest dosage that meets every performance requirement without creating processing defects.
Establish the Formulation Basis and Starting Point
Before selecting a PHR, gather:
- PVC resin grade, K-value, and batch history
- Rigid or flexible design intent
- Filler and plasticizer levels, pigments, impact modifiers
- Recycled content percentage
- Baseline stabilizer and lubricant system
- Target output, equipment type, and product performance requirements
Pull the supplier's technical data sheet, safety documentation, active-content breakdown, recommended application window, and storage guidance. Compare candidate formulations on a cost-per-100-parts-resin basis, not just price per kilogram of raw additive. A cheaper additive that requires a higher PHR to perform can cost more per finished batch.
Laboratory and Processing Tests
Run tests that match your actual application:
- Static and dynamic heat stability: color change over time under relevant thermal exposure
- Torque/fusion behavior: using a torque rheometer per ASTM D2538 to compare fusion time, melt torque, and heat/color stability against a control
- Mechanical, electrical, or optical performance: the properties your end use requires
Replicate the intended thermal history, shear, residence time, filler level, and mixing procedure as closely as you can. ASTM itself cautions that a single color-change test shouldn't be treated as sole proof of thermal stability, since correlation with real processing conditions varies.
Define your acceptance criteria before testing starts, and record performance both initially and after aging where the end use requires it.
Production Trial and Dosage Adjustment
Once lab results look promising, move to a staged plant trial. Control resin batch, mixing sequence, peak mix temperature, moisture, feed rate, screw configuration, and sampling location so you're not confusing dosage changes with process variation.
Watch for these signals:
| Symptom | Likely cause |
|---|---|
| Early yellowing, color drift | Under-stabilization |
| Odor, poor heat aging | Under-stabilization |
| Plate-out, excessive lubrication | Over-dosage or poor package balance |
| Delayed fusion, screw slippage | Over-dosage |
| Surface defects | Either direction, or equipment contamination |
Before concluding it's a dosage issue, rule out equipment contamination and processing drift. The same symptom can have different causes.
Customization and Supplier Technical Support
A catalog dosage is a starting point, not a guarantee. IKAvin's technical team works with manufacturers who need a calcium-based one-pack tailored to their specific rigid or flexible PVC formulation, using the customer's own trial data to adjust the stabilizer-lubricant balance and support scale-up.
IKAvin brings more than 30 years of PVC stabilizer experience through IKA Group to dosage selection and scale-up support. Contact the US-based technical team at info@ikavin.com with your resin type, application, equipment, current PHR, processing conditions, and target performance details.
Risks and Common Misinterpretations
Copying a dosage from a different application, resin, one-pack chemistry, or filler level can produce misleading results, even when both numbers are expressed in PHR. A 3 PHR dosage validated for rigid pipe doesn't carry the same meaning in a flexible hose formulation.
Common mistakes to avoid:
- Treating a supplier's nominal dosage as an absolute ceiling rather than a validated starting point
- Confusing active stabilizer PHR with total one-pack PHR when comparing products
- Changing stabilizer dosage without reviewing the lubrication and processing balance alongside it
Operating outside a validated range has real consequences:
- Insufficient thermal protection and visible color change
- Loss of mechanical or electrical performance
- Plate-out, poor fusion, or excessive lubrication
- Higher scrap rates and potential warranty exposure
For potable-water pipe certified to NSF/ANSI/CAN 61, confirm the certification status of any changed formulation with your certifier. Certification attaches to the specific formulation, not a generic stabilizer category.
Conclusion
PHR is a formulation control parameter, not a universal recipe. The right PVC stabilizer dosage depends on your application, your materials, your processing conditions, and what your finished product needs to deliver over its service life.
A practical path forward:
- Start with supplier-supported technical guidance
- Validate the complete one-pack in your actual formulation
- Optimize for total performance and cost, not just additive price per kilogram
IKAvin Additives Inc. works as a technical resource for sustainable calcium-based stabilizer one-packs across rigid and flexible PVC applications in the US market, from pipe and conduit through flooring and specialty films.
Frequently Asked Questions
What is PHR in PVC?
PHR means parts per hundred resin, a measurement basis using 100 parts by weight of PVC resin as the denominator. It differs from percentage of the complete compound, which includes fillers, plasticizers, and other additives.
What is UV-stabilized PVC?
UV-stabilized PVC contains a stabilizer system designed to reduce degradation from ultraviolet exposure. This typically requires more than the heat stabilizer used during processing, since light stabilization relies on separate mechanisms like UV absorbers.
How do you calculate PHR in PVC?
Divide the additive's weight by the PVC resin's weight, then multiply by 100. For example, 3 kg of stabilizer added to 100 kg of resin equals 3 PHR.
What is the typical dosage of PVC stabilizer?
Dosage varies by stabilizer chemistry, application, resin grade, filler or plasticizer loading, and processing conditions. Rather than relying on one universal number, check current technical data sheets and validate through testing.
Does PVC stabilizer dosage change by application?
Yes. Pipe, profiles, foam, wire and cable, and flooring each require different balances of thermal stabilization, lubrication, color hold, weatherability, and processing support based on their distinct performance demands.
How do you know if PVC stabilizer dosage is too high or too low?
Under-stabilization shows up as early discoloration, odor, or degradation during processing or service. Over-dosage often causes plate-out, delayed fusion, or screw slippage. Confirm the cause through controlled lab and production testing before adjusting.
