How to Choose PP Grades for Flat Yarn & Raffia Lines

Flat yarn — also called raffia or tape — is the workhorse process behind woven sacks, FIBC jumbo bags, ropes, twine, carpet backing, and agricultural nets. The process is deceptively simple: extrude a film, slit it into narrow tapes, draw the tapes under heat to orient the molecules, anneal to lock the dimensions, and wind. The resin choice, however, determines everything from tape tenacity to winder uptime. This guide breaks down what flat-yarn lines actually demand from PP resin — and how to match three proven raffia grades (L5E89, T30S, and HP550J) to your line and end-product.

1. What Flat Yarn Demands from PP Resin

Raffia lines run continuous tape at high winder speeds (300–500 m/min) and draw ratios of 5–8×. Five resin properties consistently determine whether the tapes hit tenacity targets and the winder runs without breaks.

• High tape tenacity. Drawn tape must reach the tensile strength your woven fabric or rope specifies. Resin molecular weight and the line's draw-ratio tolerance set the ceiling on tenacity.
• Narrow molecular weight distribution (MWD). A tight MWD gives uniform tape denier and stable draw — directly controlling fabric strength and winder uptime. Broad-MWD resins produce inconsistent tape and break-prone draws.
• Controlled fibrillation. For twine and rope, the tape must fibrillate predictably into fiber bundles. The right resin balances film toughness with fibrillation response — too tough and the rope won't bind; too brittle and it shreds.
• Draw stability. Stable melt strength through the drawing oven keeps tape denier and tenacity consistent lot to lot — essential for fabric weight and strength specification.
• UV stabilizer acceptance. Outdoor woven sacks, FIBC, and shade nets need UV protection. The resin must accept UV masterbatch cleanly without draw or tenacity loss.

2. Melt Flow Rate: The Starting Point, Not the Whole Story

Melt Flow Rate (MFR, 230 °C / 2.16 kg) is the first parameter every raffia buyer checks — and for good reason. It governs how the polymer flows through the die and how readily it can be drawn into tape. For flat-yarn applications, the typical MFR window is 2–4 g/10min.

A lower MFR (higher molecular weight) generally gives higher tenacity, but it also demands more extruder power, raises melt temperature, and narrows the stable-draw window. A higher MFR flows more easily and reduces extruder load, but the molecular chains are shorter — so the same draw ratio yields lower tenacity. The right MFR for your line depends on screw design, die width, draw-oven length, and target tape denier.

MFR alone does not tell the whole story. Two resins with identical MFR can behave very differently on the line if their MWDs differ. For raffia, narrow MWD is essential — it gives uniform draw behavior, consistent denier, and a stable winder.

3. Matching Grade to End-Product

The raffia family of products is broad — from heavy-duty FIBC jumbo bags rated for 1000+ kg safety factor to fine agricultural twine. Different end-products place different demands on the resin.

End-Product	Key Resin Demand	Recommended Grade
Woven sacks (cement, flour, rice, fertilizer)	High tape tenacity, UV-stabilizable, cost-efficient	HP550J — homopolymer, MFR ~3.5
FIBC jumbo bags (500–2000 kg, SF 5:1 or 6:1)	Maximum tenacity, lot-to-lot consistency	L5E89 — purpose-built raffia, high-tenacity
Ropes, baler twine, packaging cordage	Predictable fibrillation, high knot strength	T30S — fibrillating raffia grade
Carpet backing, geotextile, tech fabric	Dimensional stability, consistent tape width	HP550J — stiff, dimensionally stable
Shade nets, bird/hail net, windbreak	UV acceptance, balanced tenacity for knitting	T30S — UV-accepting raffia

4. HP550J: The Versatile Homopolymer

HP550J is a PP homopolymer with a nominal MFR around 3.5 g/10min, produced by leading Chinese mills. While it is widely used in injection molding, it is also a proven raffia grade for general-purpose woven sacks, tapes, and carpet backing — where its high crystallinity and stiffness translate into dimensionally stable tape at competitive cost.

• MFR: ~3.5 g/10min — within the raffia sweet spot
• Type: Homopolymer — high crystallinity, high stiffness
• Best for: Woven sacks, tapes, carpet backing, general raffia, geotextile
• Cost position: Excellent — high-volume grade with mill-direct pricing

5. L5E89: Purpose-Built High-Tenacity Raffia

L5E89 is a dedicated raffia grade engineered for the most demanding woven applications — FIBC jumbo bags, heavy-duty woven sacks, and high-tenacity rope. Its narrow MWD and balanced molecular architecture deliver the consistent tape tenacity required for safety-factor-rated FIBC.

• Type: Raffia / flat yarn grade
• Best for: High-tenacity woven bags, FIBC jumbo bags, ropes
• Tenacity: Optimized for safety-factor tape and lifting loops
• Lot-to-lot consistency: Engineered for certified SWL FIBC ratings

6. T30S: Fibrillating Raffia for Twine and Net

T30S is tuned for products where the tape must fibrillate predictably into fiber bundles — twine, cordage, fibrillated yarn, and knitted agricultural net. It also accepts UV masterbatch cleanly, making it the grade of choice for outdoor shade net, bird net, and windbreak that must survive multiple seasons.

• Type: Raffia / flat yarn grade — fibrillating
• Best for: Twine, cordage, fibrillated yarn, shade nets, agri net
• Fibrillation: Balanced — predictable fiber bundle formation
• UV acceptance: Clean masterbatch uptake without tenacity loss

7. Processing Recommendations

PP raffia processes on standard flat-yarn lines (film extrusion → slitting → hot-draw → annealing → winding). The table below gives a starting-point parameter set; fine-tune to your die, draw-oven length, and winder speed.

Parameter	Range
Extruder / Melt Temperature	190 – 230 °C
Die Temperature	210 – 230 °C
Draw Ratio	5 – 8
Draw-Oven Temperature	120 – 160 °C
Annealing Roll Temperature	90 – 120 °C
Winder Speed	300 – 500 m/min
Drying (recommended)	80 °C / 1–2 h

Draw-ratio tuning: Tenacity rises with draw ratio up to the resin's limit, then drops as orientation over-stresses the chain. Find the plateau for your grade — running just below the break point maximizes strength without winder breaks. Drying: PP is non-hygroscopic, but surface moisture causes tape breaks and die drips at high winder speeds. A short hot-air pass at 80 °C stabilizes the line.

Starlinger, Lohia, and domestic Chinese raffia lines each have characteristic die widths, draw-oven lengths, and winder geometries. Share your line type and target tape denier — we'll provide tuned starting parameters from comparable installations.

8. Conclusion: A Simple Selection Checklist

• Standard woven sacks, carpet backing, geotextile: HP550J — proven, cost-efficient, dimensionally stable.
• FIBC jumbo bags, heavy-duty high-tenacity applications: L5E89 — purpose-built raffia with consistent tenacity.
• Twine, cordage, shade net, agri net: T30S — fibrillating raffia with UV acceptance.

If you are running a Starlinger, Lohia, or domestic Chinese raffia line and want to benchmark your current grade against L5E89, T30S, or HP550J, share your line type, target tape denier and tenacity, end-product, and destination port. Within 24 hours we'll respond with mill-direct pricing and current availability.