Properties and Quality Calculation Formula for PP Woven Bags

To help customers better understand the properties of pp woven bags and the formulas for calculating their quality, here is some relevant information and formulas used in the woven bag industry. We hope this is helpful to packaging companies and pp woven bag customers.

Standards for Measuring Woven Bag Quality (Tensile Strength and Thickness)

1. Material

PP Woven bags are made from PP polypropylene granules. Generally, they are categorized as either virgin material or recycled material. As the names suggest, virgin material has much better tensile strength and transparency than recycled material. PP Woven bags made from virgin material typically appear transparent, very bright white, or translucent, and have excellent toughness and tensile strength.

The quality of recycled PP woven bags is determined by the level of recycling and the amount of masterbatch added. In terms of color, the tensile strength generally follows this order: white > yellow > green > gray. However, this is not absolute. For example, yellow PP woven bags are further divided into bright yellow, regular yellow, and secondary yellow, and their material quality can vary significantly. There are also some general patterns within the same color, such as transparent > translucent > bright white >= regular white > foggy white > secondary white, and for yellow, it’s extra bright yellow > bright yellow > regular yellow > secondary yellow.

2. Gram Weight

The quality of a woven bag is directly related to its gram weight. Generally, the higher the gram weight, the thicker the bag, and the better the quality. The gram weight per square meter directly determines the bag’s thickness. The calculation formula is as follows:

Weight of a single bag = Length × Width × 2 × Gram weight per square meter

The quality of a woven bag is primarily measured by these two aspects: material and gram weight. The material determines the bag’s tensile strength and toughness, while the gram weight determines its thickness and density.

In reality, PP woven bags produced by different factories may look very similar but have significant differences in quality. This is mainly due to the varying amounts of masterbatch added. When more masterbatch is added, the bag’s tensile strength decreases. This is why a common method for comparing bags from different manufacturers is to simply pull on them; bags that are harder to tear are generally of better quality.