Medical Device Link.

FILMS FOR BAGS AND POUCHES

Film materials range from standard polyethylene, polypropylene, and nylon to complex coextruded materials, as seen in production here.

Poly bags suit the needs of many applications, from industrial products to retail goods to healthcare products. In addition, the production efficiencies and cost advantages provided by premade poly bags offer multiple competitive advantages.

A distinct advantage of flexible bag packaging is the variety of materials and styles available for virtually any bag packaging operation. Each poly bag material provides distinct characteristics that enable it to meet the needs of specific applications. Characteristics such as opacity, strength, barrier properties, printability, puncture resistance, and price all factor in to the selection.

Some leading poly bag film materials or characteristics include:

• Low-Density Polyethylene (LDPE).
• Linear Low-Density Polyethylene (LLDPE).
• High-Density Polyethylene (HDPE).
• Polypropylene.
• Ultraviolet (UV) Protective.
• Corrosion Resistant.
• Opaque.
• Other Specialty Films.

To help determine the ideal material selection for optimal product packaging compatibility, take a closer look at what they offer.

Material Characteristics

Low-Density Polyethylene (LDPE) Film. Tough to the point of being almost unbreakable, LDPE is the industry standard for strength and flexibility. It is nonreactive at room temperatures, except by strong oxidizing agents, and some solvents can cause swelling. LDPE can withstand temperatures of 80°C continuously and 95°C for a short time. An optional ethylene-vinylacetate copolymer (EVA) additive enables LDPE to remain durable and flexible at extremely low temperatures, making it perfect for frozen items. LDPE comes in translucent or opaque variations in many gauges and colors. The various levels of opacity available also provide security and protection from light. LDPE is also ideal for in-line or press printing.

LDPE exhibits excellent resistance to diluted and concentrated acids, alcohols, bases, and esters. It has good resistance to aldehydes, ketones, and vegetable oils, and limited resistance (for short-term use only) to aliphatic and aromatic hydrocarbons, mineral oils, and oxidizing agents. LDPE is not recommended for use with halogenated hydrocarbons.

LDPE bag-packaging benefits include its durability, versatility, cost-effectiveness, and excellent printing characteristics. These all provide a successful packaging material for medical applications.

Linear Low-Density Polyethylene (LLDPE) Film. LLDPE is an enhanced linear, low-density material that combines superior strength and durability with ease of processing. This high tensile strength film is available in clear through opaque combinations, and in a wide range of plain and custom-printed bag configurations.

Although similar to LDPE, LLDPE has higher tensile strength and higher impact and puncture resistance. With great flexibility, it elongates under stress. LLDPE can be made into thinner-gauge films than LDPE, with better resistance to environmental-stress cracking. It resists chemicals and UV radiation well, and has good electrical properties. When compared with LDPE, the LLDPE film has lower gloss and a narrower range for heat sealing.

Other LLDPE advantages over LDPE include better hot tack and seal strength, higher stiffness, and improved puncture resistance and tear strength. LLDPE provides resistance to cracking when exposed to low temperatures, and good drawdown for thinner films.

High-Density Polyethylene (HDPE) Film. HDPE is a clear material that uses a blend of resins that are free of slip agents and other additives that can cause undesirable reactions with bag contents. HDPE has higher tensile strength than LDPE. It is also harder and has a higher haze value than LDPE given its added strength. HDPE can typically withstand higher temperatures (110°C continuously, 120°C for short periods). This film also has a high degree of scratch resistance.

The benefits of HDPE for bag packaging applications include clarity, reduced chemical additives, scratch resistance, and good permeability. Applications for HDPE include medical equipment and products that might react with chemical additives.

Polypropylene Film. Polypropylene provides superior clarity and strength for retail bag packaging. It is the best choice where bag clarity is the primary performance requirement. This high-strength, multilayer, smooth-surface film exhibits low haze properties and a high oxygen transfer rate (OTR) that resists odor seepage.

Polypropylene has good UV, chemical, and abrasion resistance; reasonable scuff and heat resistance; excellent acid resistance; and is inert to most mild chemicals. Polypropylene film is generally softer and more flexible than polyester and is available with many different coatings.

Ultraviolet (UV) Protective Films. UV protective films protect bag contents from damage and degradation. Translucent and opaque materials provide high UVA and UVB protection as well as strength and machinability. Applications for such material include pharmacy fulfillment, unit-dose packaging, and medical and security applications.

Rust/Corrosion Inhibitor Films. Ferrous metal parts for medical devices are particularly susceptible to rust and corrosion. Rust/corrosion-inhibitor films protect bag contents from rust and tarnish without the need for costly coatings. This rust and tarnish protection does not affect electrical, mechanical, or finish properties of bag contents.

Opaque Films. Opaque films are available in white, gray, black, and UV-resistant versions to protect and conceal contents. Made from a variety of polyethylene, coextruded, and custom-engineered materials, these films are ideal for applications requiring a higher level of security or where considerable stress may be placed upon the package. Benefits also include barrier resistance. Uses that benefit from opaque films include pharmacy order fulfillment and medical devices.

Other Specialty Films. Some poly bags require films with unique, application-specific performance. Examples include biodegradable films, embossed films for scratch resistance, and low-temperature films for very cold or frozen environments.

Value-added Features

In addition to selecting the right film, choosing the appropriate features in poly bags can enhance customer appeal, improve security, and offer competitive advantages. Structural features such as reclosable zippers, resealable flaps, and easy-open perforations are often regarded as must-have features. Reinforced headers with a variety of hanger holes satisfy most retailer requirements, while gusseted, stand-up pouches continue to gain in popularity. Special compartment bags or tamper-evident bags are used in the medical industry.

Premade poly bags provide a canvas for process, line, or screen printing in multiple colors, and on one or both sides of the bag. Preprinted bags can include any combination of high-resolution images, graphics, and bar codes for aesthetics and scanning accuracy. Date codes, lot codes, or other artwork can also be applied with an inline printing.

Acquiring Materials

To choose the appropriate type of poly bag film, look closely at the product’s needs. A wide range of bag film materials from standard polyethylene, polypropylene, and nylon to complex coextruded materials are available in multiple gauges and with a variety of special bag features.

Automated Packaging Systems Inc. has designed and manufactured flexible bag packaging systems for more than 40 years and is the original inventor of Autobag bagging machines and preopened bags. By extruding its own plastic poly bags, it maintains rigid tolerance standards, exceeding those established by the Flexible Packaging Association.