High pressure bag
The high-pressure bag is made from brand new LDPE plastic without any additives. It is free of whitening agents, sodium sulfate, barium sulfate, calcium sulfate, and other additives. So it is a colorless, odorless bag with high transparency, good toughness, and a soft texture.
This product is widely used in light packaging films for food, daily necessities, vegetables, carton linings, shrink-wrap, agricultural mulch film, greenhouse film, and fresh-keeping film.
Benefits of High Pressure LDPE Bags
- Versatility
High pressure LDPE bags offer versatility for a wide range of applications including storing and transporting food, packing clothes, shipping products, and more. Available in various sizes, they accommodate both large and small items and can be customized with features like zip-lock closures, printed designs, or specific colors to meet diverse requirements.
- Durability
LDPE bags are highly durable, resistant to tears, punctures, and abrasions. This makes them ideal for storing and transporting fragile items or those requiring protection from moisture and dust. Some LDPE bags can withstand high temperatures, enhancing their usability in different environments.
- Eco-friendly
Despite being made from LDPE plastic, these bags are environmentally friendly as they are recyclable and widely accepted at recycling centers. They can be reused multiple times, reducing reliance on single-use plastics.
- Lightweight
LDPE bags are lightweight, adding minimal weight and cost to shipping processes. They are particularly beneficial for businesses involved in shipping products.
- Customizable
These bags can be tailored to specific needs, such as printing logos or graphics, adding zip-lock closures, handles, or gussets. This customization makes them suitable for branding and meeting specific packaging requirements.
- Water-resistant
LDPE bags are water-resistant and some are even leak-proof, making them suitable for storing moisture-sensitive items like clothes, documents, and electronics.
- Reclosable
Many LDPE bags feature reclosable options such as zipper locks, ensuring items stored inside can be accessed multiple times while keeping contents fresh and preventing spills or leaks.
- Ease of Use
Poly bags are user-friendly, easy to open and close, and require minimal effort for loading and storing items, making them convenient for both personal and business applications.
How to Make LDPE Plastic Bags
1. The Blown-Film Extrusion Process
The first step in making poly bags is the blown-film extrusion process. Here's how it works:
- Small plastic pellets (called resin) are melted under controlled conditions until they become molten and pliable.
- Once the resin reaches the desired pliability, it is extruded through a circular die gap to form a continuous tube of plastic. In its molten state, the tube is pinched off at one end, then inflated and stretched to the size and thickness of the desired finished product.
- The inflated bubble of plastic is drawn vertically up a tower to cool before it is flattened and wound onto a roll.
- The cooled plastic on the roll can then be cut into tubing, single-wound sheeting, or centerfold sheeting. Typically, this plastic is further processed into poly bags.
2. Making Poly Bags from Plastic Rolls
After the blown-film extrusion process, the rolls of plastic are transformed into poly bags through the following steps:
- Rolls of plastic tubing or sheeting are fed through a machine that draws the material out to the proper length.
- The machine seals the material at the correct length and cuts it off to form an individual bag.
- This process is repeated until the required number of poly bags for an order is produced.
LDPE vs. HDPE Bags
Although HDPE and LDPE bags share some similarities, certain characteristics set them apart, primarily due to the branching of polymer chains. HDPE has a more crystalline structure compared to LDPE.
- Physical Differences Between LDPE and HDPE Bags
LDPE: Softer and more flexible with a lower melting point of 239 °F. It is more transparent but more prone to cracking under stress.
HDPE: Provides better chemical resistance, has a higher melting point of 275 °F, and can withstand higher temperatures. It is more rigid, durable, and has a greater strength and opacity due to its crystalline structure.
- Recycling Differences
Both LDPE and HDPE are recyclable, but they cannot be recycled together. LDPE carries recycling number 4 and is more difficult to recycle due to its soft structure, which can get caught in machinery. HDPE, with recycling number 2, can be processed more easily through recycling equipment.
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