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In PVC compounding, phr means “parts per hundred resin”.
It is the standard formulation unit used in the PVC industry to express the amount of additives relative to 100 parts of PVC resin by weight.
Definition
phr = weight of additive / weight of PVC resin × 100
The PVC resin is always fixed at 100 phr.
For example:
| Material | Amount |
|---|---|
| PVC Resin | 100 phr |
| Plasticizer (DOP/DINP/DOTP) | 50 phr |
| Calcium Carbonate (CaCO₃) | 20 phr |
| Stabilizer | 3 phr |
| Lubricant | 1 phr |
This means:
- For every 100 kg PVC resin
- Add 50 kg plasticizer
- Add 20 kg calcium carbonate
- Add 3 kg stabilizer
- Add 1 kg lubricant
The total compound weight will be:
100 + 50 + 20 + 3 + 1 = 174 kg
Why PVC Uses PHR Instead of Percentage?
PVC formulations usually contain multiple additives, and phr provides a simple and flexible way to design and adjust recipes.
For example, a flexible PVC cable formulation can be written as:
PVC Resin 100 phr Plasticizer 60 phr Calcium Carbonate 30 phr Stabilizer 4 phr Lubricant 1 phr
This means the compounder can easily modify the formulation by changing the phr value of each additive.
For example:
- Increasing plasticizer phr → softer PVC, higher flexibility
- Increasing calcium carbonate phr → lower cost, higher stiffness, but may reduce mechanical properties
- Increasing stabilizer phr → better heat stability and processing performance
Common PHR Ranges in PVC Compounds
The phr range depends on the final application, required hardness, mechanical properties, transparency, and processing conditions.
Below are typical formulation ranges for several common PVC compound products.
1. Rigid PVC for Pipe / Profile
Rigid PVC products, such as pipes, window profiles, and construction profiles, normally contain little or no plasticizer. The formulation focuses on stiffness, impact strength, weather resistance, and processing stability.
Typical formulation:
| Material | Typical Range (phr) |
|---|---|
| PVC Resin | 100 |
| Calcium Carbonate (CaCO₃) | 5–20 phr |
| Heat Stabilizer | 2–5 phr |
| Processing Aid | 1–3 phr |
| Impact Modifier (CPE/ACR) | 2–8 phr |
| Lubricant | 0.5–2 phr |
| Titanium Dioxide (for white profiles) | 3–8 phr |
Example:
PVC Resin 100 phr CaCO₃ 10 phr Stabilizer 3 phr Processing Aid 2 phr Impact Modifier 5 phr Lubricant 1 phr
Typical applications:
- PVC water pipes
- Electrical conduit pipes
- Window and door profiles
- Rigid construction profiles
2. Soft PVC for Footwear
Soft PVC footwear compounds require flexibility, softness, good appearance, and abrasion resistance. Plasticizer content is usually much higher than rigid PVC.
Typical formulation:
| Material | Typical Range (phr) |
|---|---|
| PVC Resin | 100 |
| Plasticizer (DOP/DOTP/DINP) | 40–80 phr |
| Calcium Carbonate | 5–30 phr |
| Heat Stabilizer | 2–5 phr |
| Lubricant | 0.5–2 phr |
| Pigment | 1–5 phr |
| Foaming Agent (if required) | 0.5–3 phr |
Example:
PVC Resin 100 phr Plasticizer 60 phr CaCO₃ 15 phr Stabilizer 3 phr Lubricant 1 phr Pigment 2 phr
Typical applications:
- PVC sandals
- Shoe soles
- Slippers
- Rain boots
- Flexible footwear components
3. Semi-Rigid PVC for Wire Mesh Cable
Semi-rigid PVC cable compounds require a balance between flexibility, insulation performance, mechanical strength, and processing stability.
The plasticizer level is lower than soft PVC but higher than rigid PVC.
Typical formulation:
| Material | Typical Range (phr) |
|---|---|
| PVC Resin | 100 |
| Plasticizer | 15–40 phr |
| Calcium Carbonate | 10–40 phr |
| Heat Stabilizer | 2–5 phr |
| Lubricant | 0.5–2 phr |
| Processing Aid | 1–3 phr |
| Flame Retardant (if required) | 5–20 phr |
Example:
PVC Resin 100 phr Plasticizer 25 phr CaCO₃ 20 phr Stabilizer 3 phr Lubricant 1 phr Processing Aid 2 phr
Typical applications:
- Wire mesh cable coating
- Electrical cable sheath
- Semi-flexible cable insulation
- Protective cable jackets
4. Rigid Transparent PVC
Rigid transparent PVC requires very high clarity and therefore normally uses little or no filler. The formulation emphasizes transparency, processing performance, and thermal stability.
Typical formulation:
| Material | Typical Range (phr) |
|---|---|
| PVC Resin | 100 |
| Heat Stabilizer | 2–5 phr |
| Processing Aid | 1–3 phr |
| Lubricant | 0.2–1 phr |
| Impact Modifier (optional) | 1–5 phr |
| Plasticizer (optional, very low level) | 0–10 phr |
Example:
PVC Resin 100 phr Stabilizer 3 phr Processing Aid 2 phr Lubricant 0.5 phr Impact Modifier 2 phr
Typical applications:
- Transparent PVC sheets
- Transparent packaging materials
- Clear tubes
- Protective covers
- Transparent rigid containers
Converting PHR to Percentage
If you need to convert phr into final compound percentage:
Additive wt% = (Additive phr / (100 + Total additive phr)) × 100
Example:
PVC resin = 100 phr
Calcium carbonate = 25 phr
Total compound:
100 + 25 = 125 phr
Calcium carbonate percentage:
25 ÷ 125 × 100 = 20%
Therefore:
25 phr CaCO₃ equals approximately 20 wt% in the final PVC compound.
For PVC compound manufacturers, phr is the standard language for formulation design, while customers usually evaluate products based on final properties such as:
- Hardness (Shore A / Shore D)
- Tensile strength
- Elongation
- Impact resistance
- Density
- Transparency
- Heat stability
- Processing performance
The correct phr formulation depends on the final application, processing equipment, customer requirements, and target cost.
Frequently Asked Questions (FAQ)
What Does PHR Stand For In PVC Compounding?
PHR stands for Parts Per Hundred Resin. It represents the weight ratio of additives relative to 100 parts of PVC resin by weight.
Why Isn't Percentage Used During Formulation Design?
Percentage changes for every single ingredient whenever one additive is adjusted. PHR keeps the base PVC resin constant at 100, making formulation adjustments simple and error-free.
Can Novos Plastic Customize PHR Formulations For Specific Production Needs?
Yes, Novos Plastic optimizes resin types, plasticizer phr, fillers, and stabilizer systems based on specific processing machines, target hardness, density, and physical strength requirements.