How to Specify Coated vs. Laminated vs. Uncoated PP Woven Bags Clearly in an RFQ
When issuing a Request for Quotation (RFQ) for packaging, a brief description such as “PP bag with lamination, 90 gsm” is insufficient for manufacturers to determine the exact technical requirements. The term “laminated” can easily be misinterpreted as either direct extrusion coating on woven fabric or lamination with a separate BOPP film. Without clarification of the pp woven bag structure from the outset, two suppliers may quote entirely different products despite identical dimensions and total GSM specifications. Buyers can review the available PP woven bags as a product reference.
Core Takeaway: Before releasing an RFQ, buyers must identify and specify each component independently: base PP woven fabric, coating layer or laminated film, applied side, GSM or thickness of each layer, and PE liner (if applicable). Avoid using a single generalized “total GSM” figure or the vague term “laminated” without detailed specifications.
Key Factors Buyers Must Lock Down First in an RFQ
- Use correct structural terminology: Clearly distinguish between uncoated, extrusion coated, and BOPP laminated constructions.
- List by layer sequence: Declare the structure from outside to inside; specify clearly if the front and back faces differ.
- Separate layer specifications: State the base fabric GSM (g/m²), coating or bonding layer GSM (g/m²), BOPP film thickness (µm), and PE liner thickness (µm), where applicable.
- Comprehensive cross-checking: Synchronize parameters across quotations, technical drawings, approved samples, and confirmation sheets.
1. Accurately Defining the PP Woven Bag Structure in an RFQ
Case A — Uncoated PP Woven Bags
Explicitly state that this is PP woven fabric without extrusion coating or laminated BOPP film. If the product requires an internal PE liner, the liner must be declared as an independent component; the presence of a liner does not alter the uncoated nature of the external woven fabric.
In the RFQ, specify the base fabric GSM, yarn specifications or weave direction (if required), color, printing method on the woven fabric, and a clear note stating “both sides uncoated” if the buyer needs to control breathability or surface characteristics; anti-slip performance should be tested separately when required.
Case B — Extrusion Coated PP Woven Bags
Specify PP woven fabric with a direct extrusion coating layer (typically PP or PE depending on the factory’s technical specifications). Clearly define the coating position (inner or outer surface, front or back), the independent coating GSM (g/m²), and agreed tolerance levels.
Avoid vague descriptions such as “20 µm coated film”, because thickness (µm) alone cannot establish coating weight (g/m²) without the material density and layer construction. If the bag requires venting or reduced powder sifting, specify the micro-perforation density, hole placement, and appropriate testing methods.
Case C — BOPP Laminated PP Woven Bags
Explicitly define this as BOPP film bonded to PP woven fabric through a suitable tie layer; the film may be rotogravure-printed if the design requires it. Do not rely on the term “laminated” alone in an international RFQ. State the BOPP film thickness, tie-layer material and coating weight (when controlled), laminated face, and artwork placement.
For reverse rotogravure printing (printing on the inner side of clear BOPP film before lamination), attach a technical drawing indicating the printed face. If lamination is applied to only one side (usually the front) while the back remains uncoated or extrusion coated, the technical drawing must reflect this asymmetrical structure.
2. Layer-by-Layer Structure Declaration Table — Core RFQ Addition
The table below focuses entirely on the pp woven bag structure and material composition. Dimensions, bottom sewing styles, filling weight, and commercial terms belong in the standard general RFQ template.
| Field to Declare | Uncoated | Extrusion Coated | BOPP Laminated |
|---|---|---|---|
| Technical Structure Name | PP woven fabric, uncoated | Base PP woven fabric + extrusion coating layer | PP woven fabric + suitable tie layer + BOPP film |
| Base PP Woven Fabric | GSM and specified tolerance | Base fabric GSM (excluding coating) | Base fabric GSM (excluding laminated film) |
| Surface Coating / Lamination | Not applicable | Coating resin type (PP/PE), specified coated side | BOPP film type, laminated face, tie-layer construction |
| Additional GSM Specifications | Note clearly: Uncoated / No lamination | Independent coating GSM (g/m²), tolerance | BOPP film thickness (µm), tie-layer specifications |
| Face Direction & Gusset | Confirm both sides are uncoated | Specify inner/outer, front/back, and gussets | Specify laminated face (front/back) and artwork |
| Internal PE Liner | Yes or No; if yes: specify polymer type, thickness (µm), attachment method, and closure requirements. | ||
| Required Technical Evidence | Physical sample and uncoated confirmation | Sample, coating specification sheet, acceptance criteria | Sample, film/tie-layer specifications, bond-strength test where specified |
Important Note on Units: The unit g/m² denotes mass per unit area, while µm denotes material thickness. Film thickness cannot automatically be converted into an accurate mass per unit area without the material density and relevant structural data.
3. Three Standardized Description Templates for RFQs
Replace the fields in square brackets [...] with specifications approved by your technical department. Any undecided field should be identified as “Supplier to propose” rather than filled with an unsupported assumption.
Template A — Uncoated PP Woven Bag
Material Structure: PP woven fabric [specified PP resin grade], uncoated; no extrusion coating; no laminated BOPP film.
Base Fabric GSM: [___] g/m²; Tolerance: [___].
Face Specification: Both front and back faces are uncoated.
PE Liner: [None / Loose PE liner, thickness ___ µm].
Template B — Extrusion Coated PP Woven Bag
Material Structure: Base PP woven fabric combined with a direct extrusion coating layer [Select: PP / PE resin or approved specialized material].
Base Fabric GSM: [___] g/m²; Coating GSM: [___] g/m²; Layer Tolerance: [___].
Coating Position: [Outer / Inner surface; applied to front and back].
Template C — BOPP Laminated PP Woven Bag
Material Structure (Outside to Inside): BOPP film [Transparent / Reverse printed if required by the drawing] + Tie layer [extruded polymer or suitable approved adhesive] + Base PP woven fabric.
Detailed Specifications: Base fabric GSM [___] g/m²; BOPP film thickness [___] µm; Tie-layer coating weight [___] g/m² (if controlled); Tolerance [___].
Lamination Layout: Laminated face [Front / Both sides]; Printed face [___].
4. Supplier Quotation Cross-Checking Procedure Against RFQ Structure
Do not stop at comparing a final unit price. Before proceeding with sample production, require suppliers to complete a structural proposal response sheet following the exact layer sequence specified in the RFQ.
| Verification Item | RFQ Technical Requirement | Supplier Confirmation | Evaluation Status |
|---|---|---|---|
| Structural Classification | [Uncoated / Coated / BOPP Laminated] | [Specify actual resin technology and structure quoted] | [Match / Alternative Proposed / Pending] |
| Layer Sequence & Position | [Adhere to outside-to-inside layer diagram] | [Confirm actual structure per face] | [___] |
| GSM, Thickness & Tolerance | [Decoupled per layer, correct units] | [Itemized per layer, no aggregated numbers] | [___] |
5. In-Depth Technical Verification Questions for Material Structure
- In this quotation, does the term “laminated bag” refer to direct extrusion coating or BOPP film lamination?
- Does the reported g/m² value refer to the woven fabric alone or include coating/lamination? Is finished bag mass (g/bag) reported separately?
- On which side of the bag is the coating layer or laminated film positioned? Do the back face, side gussets, and folding edges have the same construction?
- For BOPP laminated bags, have the film grade, thickness, tie-layer material and coating weight (if controlled), and printing technology been explicitly documented in drawings or samples?
- For coated bags, have the polymer grade, coating GSM, and tolerance limits been mutually agreed upon?
6. Locking Down Material Specifications Prior to Sample Approval and PO Issuance
Buyers should use a version-controlled material technical specification sheet showing the layer arrangement from outside to inside, specifications and tolerances for each layer, coating/lamination/printing locations, PE liner status, and a list of approved technical evidence.
To learn more about preparing the complete specification before placing an order, review our general PP woven bag RFQ specification guide.
Frequently Asked Questions
Is noting “PP laminated bag” in an RFQ sufficient for an accurate supplier quotation?
No. Buyers must clarify whether the construction uses direct extrusion coating or a separate BOPP film laminated to the woven fabric. The applied face and relevant specifications for each material layer must also be stated.
Can uncoated PP woven bags include an internal PE liner?
Yes. The “uncoated” designation describes the woven PP fabric without an applied surface coating or BOPP film. A PE liner, when included, is a separate internal component that must be specified independently.
Conclusion: Define the Correct Structure and Specify Every Material Layer
A professional RFQ does not need to be excessively long, but it should eliminate ambiguity that could cause suppliers to quote different constructions. For the three common pp woven bag structure types—uncoated, extrusion coated, and BOPP laminated—use clearly defined terminology and separately specified material-layer parameters.
Need to review and optimize your proposed packaging structure? Send your material-layer drawings, current packaging samples, or product photos through the Huong Sen Packaging contact page to discuss suitable technical specifications with our team.
