Heat-Shrinkable Bags from China Suppliers - High-Quality Industrial Packaging from Our Factory
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)
- 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.
- The cost is slightly higher than PVC.
- Widely used in food, pharmaceuticals, cosmetics, stationery, toys, electronics, etc.
2. PVC (polyvinyl chloride)
- Low cost: the price is relatively cheap.
- Strong contractile force: it binds the product tightly.
- 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.
- It is still used for some industrial products, card cards, etc. packaging that do not have high environmental requirements.
3. PET / PETG
- Extremely strong: very strong and shock resistant.
- High transparency: The presentation was excellent.
- Eco-friendly and recyclable.
- Costs are highest and require higher temperatures to contract.
- mainly used in high-end electronics, batteries, cosmetics, tools and other areas that require high-strength protection.
4. OPS (polystyrene)
- Very high transparency, good gloss, and environmentally friendly.
- The texture is fragile and easily cracked.
- 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:
How to use heat-shrinkable bags?
The size of the bag should be 10-20% larger than the product it will contain, to leave room for shrinkage.
Place the product inside the bag.
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.
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
Q1: What are the main differences between POF and PVC shrink bags?
POF (Polyolefin) is highly transparent, durable, food-safe, and environmentally friendly, though it costs slightly more. PVC (Polyvinyl Chloride) is cheaper and shrinks tightly, but it is less eco-friendly, can release toxic gases when burned, and is prone to yellowing and tearing over time.
Q2: How do I choose the correct size of heat-shrinkable bag?
You should select a shrink bag size that is approximately 10% to 20% larger than the dimensions of your product. This extra room ensures the product fits easily inside and leaves enough material to contract evenly during heating.
Q3: Can I use a household hair dryer or a lighter to shrink these bags?
It is not recommended to use open flames like lighters, as they can burn and deform the plastic. Standard household hair dryers usually do not reach the temperature required to shrink the material effectively. Using a professional heat gun or a shrink tunnel is highly recommended for best results.
Q4: Are POF heat-shrinkable bags safe for packaging food products?
Yes, POF (Polyolefin) is non-toxic and environmentally friendly. It produces only carbon dioxide and water when combusted, meeting strict food packaging safety standards, making it the preferred choice for food and beverages.
Q5: Which shrink bag material is best for high-end electronics and batteries?
PET or PETG is the ideal choice for high-end electronics, batteries, and cosmetics. They are high-performance engineering plastics that offer extreme durability, excellent impact resistance, high transparency, and eco-friendly recyclability.