Correct Folding and Storage Methods for PVC Bags (Scientific Practical Guide)
PVC bags are widely used due to their good flexibility and strong water resistance. However, incorrect folding and storage methods (such as random rubbing and exposure to high temperatures) can lead to material aging, edge cracking, surface wrinkling and even adhesion. The following provides practical solutions from four dimensions: folding techniques, storage environment, scenario-based solutions, and taboos, taking into account both material protection and space utilization efficiency.
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First, the core principle of folding: Avoid stress concentration and permanent deformation
Material properties and folding risks
Stress-sensitive areas of PVC bags:
Edge sealing: The thickness of the heat-pressed sealing area is only 1/3 of the bag body, and it is prone to cracking when folded.
Printing layer: The adhesion between the ink and the PVC substrate is relatively weak. Repeated folding will cause the ink to fall off.
Plasticizer precipitate layer: Phthalate plasticizers in PVC will migrate to the surface over time and tend to stick together when folded.
Experimental data:
PVC bags that are wrongly folded (such as curling after being folded in half) have their service life shortened to one-third of those that are correctly folded.
For every 10℃ increase in temperature at the fold, the rate of plasticizer precipitation doubles and the risk of adhesion rises by 50%.
2. Pre-treatment before folding
Clean and dry
Use a microfiber cloth dipped in a 1:50 neutral detergent water solution to wipe the bag body, with a focus on cleaning the edge sealing seams.
Let it air dry naturally or use a cold air blower (at a distance of ≥30cm) to dry it to avoid mold caused by residual moisture.
Eliminate static electricity
Spray the surface of the bag evenly with anti-static spray (such as “3M ES2020”), or wipe it gently with a damp cloth and let it dry to prevent dust adsorption after folding.
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Second, standard folding methods (by size and application)
Small PVC bags (such as clothing packaging bags, gift bags)
Step:
Flatten and align: Lay the bag flat on the table, gently press and smooth out the wrinkles with both hands, and ensure that the four sides are aligned with the edges of the table.
Three-fold method
Fold it up and down (fold the short side in half) to compress the height of the bag to half.
Fold it left and right (fold the long side in half) to form a long strip.
Fold it in three equal parts again, and the final size will be 1/6 of the original bag.
Anti-sticking treatment: Insert sulfate paper (0.1mm thick, neutral pH) at the fold to prevent direct contact with PVC.
Effect: After folding, the thickness is reduced by 80%, and it can be stacked vertically in the storage box, with the space utilization rate increased by three times.
2. Medium-sized PVC bags (such as logistics turnover bags, document storage bags)
Step:
Internal support fixation
Fill with cardboard of the same size (thickness ≥2mm) to prevent the bag from collapsing and deforming when folded.
The cardboard needs to be coated with a 0.05mm thick layer of silicone oil in advance to avoid adhesion with PVC.
Winding method
Starting from the bag opening, tightly wind along the length direction, with each lap overlapping width not exceeding 1cm.
When rolling to the end, fix it with Velcro or elastic straps to prevent it from loosening.
Moisture-proof isolation
The wound bags are placed in PE self-sealing bags (with a thickness of 0.08mm), and before sealing, a 10g silica gel desiccant bag is put in.
Advantage: The winding method can reduce the force on the edge banding and extend its service life by more than twice.
3. Large PVC bags (such as industrial raw material bags, flood control sandbags)
Step:
Layered folding
Lay the bag body flat and fold it up to 1/3 of its height from the bottom.
The top covers downward, forming a three-layer structure in the shape of a “Z”.
Fold both sides towards the middle, and compress the width to 1/4 of the original bag.
Support and reinforcement
Place EVA foam blocks (hardness 40 Shore C) at the four corners of the folded bag body to prevent collapse caused by long-term stacking.
The top is covered with dust-proof cloth (material: Oxford cloth +PU coating) to prevent dust from seeping into the seams.
Load-bearing limit:
The stacking height should not exceed 1.2 meters. The bottom bags need to be rotated 180° regularly (every quarter) to disperse the pressure.
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Third, storage environment control (Five Elements)
Temperature
Safety range: 15-25℃
High-temperature hazard: When the temperature exceeds 35℃, the leaching rate of PVC plasticizers increases, and the bag body becomes soft and sticky.
Low-temperature hazard: Below -5℃, PVC becomes brittle and prone to cracking, with a higher risk in the stress concentration area at the folds.
Solution:
Install temperature and humidity sensors (such as “Mi Home Bluetooth Temperature and Humidity Meter 2”) in the warehouse. When the temperature exceeds the standard, the air conditioner or ventilation equipment will be automatically activated.
In high-temperature areas during summer, place a phase change material (PCM) temperature control bag (melting point 25℃) in the storage box to maintain a stable temperature around the bag.
2. Humidity
Safety range: 40-60%RH
High humidity hazard: When the humidity exceeds 70%, PVC is prone to absorbing moisture, causing the edge banding to delaminate and mold to grow.
Low humidity hazard: When the humidity is less than 30%, the accumulation of static electricity increases, and the adsorption of dust causes surface scratches.
Solution:
Place color-changing silica gel desiccants (initially blue and turning pink after absorbing moisture) in the storage box. Replace them in time when the humidity exceeds the standard.
In the dry northern regions, place a humidifier (with a humidity setting of 50%) in the storage area and use an ion fan to neutralize static electricity.
3. Lighting
Light-avoiding requirements:
Ultraviolet rays (UV) can damage the molecular chains of PVC, causing yellowing and embrittlement.
The experiment shows that the tensile strength of the PVC bag decreased by 35% after continuous irradiation for 72 hours (with a light intensity of 1000lux).
Solution:
Store in an opaque storage box (material: ABS+ carbon black masterbatch, light transmittance < 0.1%);
The warehouse Windows are covered with UV400 heat insulation film, blocking 99% of ultraviolet rays.
4. Ventilation
Air circulation
The storage area should be ventilated 3 to 5 times per hour to prevent the concentration of volatile plasticizers from exceeding the standard.
In a long-term closed environment, the concentration of diisononyl phthalate (DINP) released by PVC may exceed the safety threshold (0.1mg/m³).
Solution:
Use industrial exhaust fans (with an air volume of 500m³/h) for regular ventilation, or install activated carbon filter screens to adsorb volatile substances.
Fold the PVC bags and stack them at intervals of more than 1cm to avoid gas retention caused by sticking together.
5. Load-bearing capacity and pressure
Stacking limit:
Soft PVC bags (thickness < 0.2mm) : Stacking height ≤0.8m;
Thickened PVC bags (thickness ≥0.3mm) : Stacking height ≤1.5m.
Pressure dispersion
Place a moisture-proof pad (material: XPE foam, thickness 5mm) between the bottom bag and the ground to buffer the reaction force from the ground.
Place corrugated cardboard (with a weight of 200g/m²) between each layer of bags to reduce direct squeezing.
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Fourth, scenario-based storage solutions
1. Home scenarios (such as clothing storage, organizing miscellaneous items)
Storage tools:
Transparent PP storage box (dimensions: 40×30×20cm), with detachable partition boards;
Hanging dust bag (material: PEVA, with ventilation holes).
Step:
Fold the PVC bags by season/purpose and put them into storage boxes.
Place a dehumidification box (calcium chloride granules) inside the box and replace it every three months.
The hanging dust-proof bag is used to store the frequently used bags of the current season and is hung on the inner side of the wardrobe.
2. Business scenarios (such as retail stores, logistics warehouses)
Storage tools:
Metal storage shelves (load-bearing capacity ≥500kg per layer), with anti-slip patterns on the shelves;
Anti-static turnover box (Material: conductive HDPE, surface resistance 10⁴-10⁶Ω).
Step:
The wound PVC bags should be vertically stacked in the turnover boxes by model to avoid horizontal stacking.
Temperature and humidity recorders (such as “Testo 174H”) are placed on each layer of the shelves, and the data is synchronized to the cloud.
Regularly (monthly) blow the gaps between the shelves with compressed air to remove dust.
3. Industrial scenarios (such as packaging of chemical raw materials, reserves of flood control materials)
Storage tools:
Explosion-proof cabinet (Material: Double-layer steel plate, with pressure relief port)
Intelligent shelves (with pressure sensors for real-time load monitoring).
Step:
The large PVC bags are folded and placed flat in the explosion-proof cabinet, with each layer separated by wooden pallets.
A gas concentration alarm is installed inside the cabinet (to detect the volatile substances of plasticizers such as DINP and DOTP).
Take samples regularly (every quarter) to test the physical properties (tensile strength, elongation at break) of PVC bags.
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Fifth, storage taboos and misunderstandings
1. Absolutely prohibited behavior
High-temperature exposure to the sun: In summer, if PVC bags are directly placed in a vehicle or an open-air warehouse, the temperature of the bag body can reach 60℃ within 2 hours, causing permanent deformation.
Sealed storage: Completely seal the PVC bag with a plastic bag. The volatile plasticizer cannot be discharged, accelerating the adhesion of the bag body.
Contact with corrosive substances: When stored together with items containing sulfur or chlorine (such as rubber products and PVC hoses), chemical reactions may occur, leading to embrittlement.
2. Correction of common misunderstandings
Misconception 1: The tighter the fold, the better
Hazard: Excessive squeezing causes edge banding cracking and material fatigue damage.
The correct approach is to retain 5% to 10% of the elastic space after folding to prevent stress concentration.
Misconception 2: All PVC bags use the universal folding method
Hazard: Thick bags folded by the thin bag folding method are prone to wrinkling, and thin bags folded by the thick bag folding method are prone to deformation.
The correct approach: Classify by thickness (use the winding method for < 0.2mm, and the three-fold method for ≥0.2mm).
Misconception 3: No need to check before storage
Hazard: Residual stains and sharp objects are not cleaned up, leading to mold or scratches.
The correct approach: Before folding, use a strong flashlight to inspect the bag body and remove any damaged or severely contaminated bags.
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Sixth, maintenance tips for extending storage life
Turn regularly
Every quarter, take out all the stored PVC bags, refold them and change their storage locations to avoid long-term pressure on the same part.
Surface maintenance
Every six months, gently spray the surface of the bag with silicone oil (food grade), wipe it with a cotton cloth until it is bright, restore its water resistance and reduce static electricity.
Damage prediction
Inspection indicators:
The bag body shows powdering phenomenon (gently rub off the debris with fingers);
The light transmittance is less than 50% (visible turbidity to the naked eye under natural light).
Irreversible whitening occurs during stretching (a sign of material aging).
Solution: Eliminate once any indicator is met to prevent damage caused by breakage during transportation.
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Seventh, Key conclusions and implementation suggestions
Comparison of folding storage effects
Incorrect method: random rubbing + high-temperature warehouse → After 6 months, the bag body adhesion rate is 100%, and the damage rate is 40%.
The correct approach: Three-fold method + constant temperature and humidity warehouse → After 12 months, the bag body integrity rate is 95%, and the number of reuses increases by three times.
Balance between cost and efficiency
Home scenario: Use PP storage boxes + color-changing silicone, with a single storage cost of less than 5 yuan.
Business scenario: The introduction of an intelligent warehousing system (including temperature and humidity monitoring) has increased management efficiency by 50%.
Environmental protection alternative solutions:
For scenarios with high storage requirements, the following can be used instead:
Tpu-coated fabric bags: Resistant to folding over 100,000 times, washable and reusable;
Biodegradable PLA composite bags: Stable performance within one year of storage, and complete degradation within 180 days after disposal.
Through scientific folding and standardized storage, the service life of PVC bags can be extended by 3 to 5 times, while reducing the loss cost caused by improper storage, achieving a win-win situation of efficient resource utilization and environmental protection goals.
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