Why would you need an inner liner for your bulk bags? There are two main reasons for these optional extras. Firstly, for extremely fine powders and liquid materials, an inner liner prevents seepage or leakage through the seams and minute holes in the polypropylene fabric. Secondly, inner liners help to preserve the purity of materials by keeping moisture and air out of the bags.

An inner liner covers the entire inner surface of a bulk bag. Some are freely inserted, some sewn into place, and others are glued. We’ll explore some of the types of inner liners available to you, as well as their fitment and construction so that you can have a better understanding of what you need.

Custom Bulk Bags is a leading manufacturer and supplier of high-quality bulk bags in South Africa. We manufacture these flexible, durable and customisable packaging containers in-house using extruded polypropylene tapes. Our products have a minimum safety factor rating of 5:1 and can hold up to two tonnes of material.

Types of inner liners

There are a few basic types of inner liners:

  1. Standard liners – These are made from polyethylene sheets and fit inside the bulk bag. They contain some wrinkles which allow them to adjust to the bulk bag’s shape once filled.
  1. Tubular liners – These are tubular in shape, rather than square, which makes them ideal for tubular bulk bags. They are cheaper to produce but do not utilise the inner space as well as a standard liner.
  1. Formliners – These are shaped like a bottle and are designed to fit the spouts of a bulk bag too. A formliner improves material flow and handling.
  1. Baffled liners – Also called Q-liners, these have baffles which allow them to double as Q-bags. Baffled liners are a premium solution but cost more to produce.
  1. Anti-static liners – These are manufactured from anti-static resin and help to dissipate any electrical charge that may build up during filling, transportation and discharging. This is vital for materials that are flammable or combustible.
  1. Suspended liners – These are a less common and special type of inner liner that are designed for one- or two-loop bulk bags.
Custom Bulk bags production floor

How liners are fitted

Most inner liners are just inserted loosely into the bulk bags, with no mechanical attachments. These are cost-effective and ideal for simple applications. For a more secure attachment, a tabbed liner is required. These use eight small tabs that attach to each corner of the bag to prevent the liner from shifting during filling, discharging or transportation.

For even better fitting, some inner liners are sewn in along all four seams. This prevents shifting completely. Alternatively, inner liners can be glued in place using hot glue, but this is a more costly option, although it offers the most secure fitment.

Inner liner materials

Not all liners are made from polyethylene, although this is the most common material used due to its flexibility, light weight and transparency. Other materials used to produce inner liners include:

  • Aluminium foil – These liners are more robust and offer better protection against external surfaces and rough transport. They also improve filling, discharging, handling and stability, but are more expensive. Foil liners have better protection against oxygen, UV rays and moisture too. They are recommended for products that are flammable or that emit unpleasant fumes or gases.
  • EVOH film – EVOH stands for ethylene-vinyl alcohol copolymer and these films have a high sealing capability with better mechanical strength and puncture resistance than standard polyethylene liners.
  • PA film – Polyamide is also known as nylon. These films have similar properties to EVOH but also have high corrosion and impact resistance too.

With so many options available to you, it can be daunting or confusing to know what you need. Custom Bulk Bags offers comprehensive guidance and consultations, which ensures that you select the best inner liners for your needs. For more information about our bulk bags, please contact us today. 


Custom Bulk Bags is a leading South African manufacturer of woven polypropylene bags for various industries, such as mining, chemicals and food. We are able to produce over 3.5-million bulk bags per year, keeping our customers in stock at all times. Our bags adhere to the highest levels of quality as a result of our stringent in-house testing and quality control programmes.

Custom Bulk Bags holds ISO 9001 certification and we currently have a number of UN-certified designs. We are a Level 2 B-BBEE manufacturer and supplier and fall under the ownership structure of Deneb Investments Limited. For more information on our products, contact sales@custombulkbags.co.za. Follow us on Facebook for our latest news and industry insights.