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China Suppliers Factory for Heat-Shrinkable Bags | Industrial Packaging Solutions
What is a hot compressed bag?
Heat shrinkable bags, also known as shrink bags or PVC / POF shrink bags, is a packaging material made of special plastic film. When heated (usually using a hot windmill, syringe, or oven), it contracts evenly in one or both directions, thus tightening the contents of the interior to form a strong, transparent, and aesthetically pleasing protective film.
Working principle
The raw materials of the hot compressed bags have gone through a process of "prestretching" and "cooling and forming" before they leave the factory. This means that the plastic molecules are forcefully stretched and arranged when manufactured, and are cooled to secure in a stretched state. When you heat it again, these "frozen" molecular chains return to their original state of relaxation, causing the film to contract in size and tightly adhere to the product surface.
Main types and materials
1. POF (polyolefin)
Features: The most mainstream and environmentally friendly option at present.
Pros:
- High transparency: excellent presentation.
- High toughness: Good tensile resistance and not easy to break.
- Eco-friendly and non-toxic: Carbon dioxide and water are produced after combustion and meet food packaging standards.
- High shrinkage rate: shrinkage is uniform, surface smooth and aesthetically pleasing.
Disadvantages:
- The cost is slightly higher than PVC.
Applications:
- Widely used in food, pharmaceuticals, cosmetics, stationery, toys, electronics, etc.
2. PVC (polyvinyl chloride)
Features: Early commonly used materials, now gradually replaced by POF.
Pros:
- Low cost: the price is relatively cheap.
- Strong contractile force: it binds the product tightly.
Cons:
- Poor environmental performance: When burned, toxic gases such as hydrogen chloride are produced, which is not conducive to the environment and health.
- Easy to turn yellow: After being stored for a long time or being heated, it may turn yellow, affecting aesthetics.
- Poor resilience: relatively easier to tear.
Application:
- It is still used for some industrial products, card cards, etc. packaging that do not have high environmental requirements.
3. PET (Polyethylene Terephthalate) / PETG
Features: High performance engineering plastics.
Pros:
- Extremely strong: very strong and shock resistant.
- High transparency: The presentation was excellent.
- Eco-friendly and recyclable.
Cons:
- Costs are highest and require higher temperatures to contract.
Application:
- mainly used in high-end electronics, batteries, cosmetics, tools and other areas that require high-strength protection.
4. OPS (polystyrene)
Characteristics: A hard, brittle material.
Pros:
- Very high transparency, good gloss, and environmentally friendly.
Disadvantage:
- The texture is fragile and easily cracked.
Applications:
- Mainly used in food (such as pastries, fruit trays), stationery, toys, etc.
Application areas
The application of heat-shrinkable bags is extremely widespread, encompassing almost all industries that require packaging:
✔Food and Beverages: Collection packaging for bottled water, beverages, canned goods, biscuits, and frozen food products.
✔Personal care products: paper box packaging for shampoos, body washes, cosmetics, and toothpaste.
✔Pharmaceutical and health products: Sealed packaging for medication boxes and health product boxes.
✔Stationery and Toys: Packaging for stationery sets, toys, and board game sets.
✔Electronic products: batteries, USB drives, SD cards, data cables, packaging for small appliances.
✔Hardware tools: Cardboard-packaged tools such as screwdrivers and wrenches.
✔Printed materials: waterproof packaging for magazines and books.
How to use heat-shrinkable bags?
1
Choose the right size: The size of the bag should be 10-20% larger than the product it will contain, to leave room for shrinkage.
2
Loading the product: Place the product inside the bag.
3
Sealing: Use a specialized L-shaped sealing machine or a cuff-style sealing machine to heat-seal the bag's opening. Manual operation can be performed using a heat sealing rod or the Impulse Sealer.
4
Heating and shrinkage:
- Mass production in industry: Utilization of thermal shrinkage channels (shrinkers). Products pass through a heated tunnel on a conveyor belt, ensuring even heating and high efficiency.
- Small batches/DIY: Use a heat gun. Maintain a distance of 15-20 centimeters between the heat gun and the bag, and continuously move it to evenly heat each surface until the bag is fully contracted and flattened. Note: Do not use open flames (such as lighters) to directly heat the bag, as this can cause the bag to burn and deform.
Frequently Asked Questions (FAQ)
What is the difference between POF and PVC shrink bags?
POF (polyolefin) is highly transparent, durable, and environmentally friendly, making it safe for food packaging. PVC (polyvinyl chloride) is cheaper and has a strong shrink force, but it is not eco-friendly, can turn yellow over time, and releases toxic odors when heated.
Can I use a regular hair dryer to shrink these bags?
Generally, no. A standard household hair dryer does not produce enough heat to shrink POF or PET bags efficiently. A professional heat gun, impulse sealer, or shrink tunnel is highly recommended for proper contraction.
How do I calculate the right size of shrink bag for my product?
You should choose a shrink bag that is approximately 10% to 20% larger than the overall dimensions of your product. This extra room ensures the product fits easily inside and allows the film to shrink uniformly without tearing.
Are POF shrink bags safe for direct food contact?
Yes, POF shrink bags are made from non-toxic materials and do not produce harmful gases when heated. They comply with food packaging safety standards and are widely used for biscuits, frozen foods, and other edible items.
Why does my shrink bag melt or get holes during heating?
Holes or melting usually occur if the heat source is kept in one place for too long or is positioned too close to the bag. Make sure to maintain a distance of 15-20 cm and keep the heat gun moving continuously for even shrinkage.