Stretching film for hand drawn machines

What are the characteristics of good stretch films
1、 Look at the appearance:
A high-quality stretch film has a soft and natural appearance, with good transparency. Place a newspaper 20 centimeters below the stretch film to clearly see the words on it, without affecting reading. Slightly inferior quality stretch films, due to the addition of plasticizers, titanium dioxide, etc., will make the surface appear bright and have a thick feel, but the transparency is poor, which is easy to distinguish.
2、 Measurement of tension:
Stretching is the ability of a stretching film to produce elastic elongation after being subjected to tension, which is a characteristic of itself. If the quality is good, the length will be extended after stretching, and within a certain range (300% -700%), it will not break. Poor quality stretch film has two characteristics: ① Uneven tension, with some areas noticeably becoming thinner during stretching and some areas showing almost no change. 2. The stretching rate is small, and there will be a phenomenon of breaking when stretched.
3、 Self adhesive:
Self adhesiveness refers to the adhesion between stretch films after contact, which can tighten the packaged items during the stretching and wrapping process without loosening. Self adhesiveness is influenced by various external factors such as humidity, dust, and pollutants. A good stretch film has a self adhesiveness of about 1N/c ㎡. Wrap ordinary eggs in stretch film and press a thumb sized area to lift them up. Poor quality stretch film cannot achieve this effect.
4、 Resilience (puncture resistance):
Toughness refers to the comprehensive performance of tensile films in terms of resistance to puncture and tear. The danger level value of tear resistance must be taken horizontally, which is perpendicular to the direction of machine operation, because tearing in this direction will make the packaging loose. Even if tearing occurs longitudinally, the packaging can still remain firm. Therefore, the better the toughness of the stretch film, the better the quality. Poor quality stretch film generally has low toughness. You can wrap some water in stretch film and use a ballpoint pen to prick it. If there is no water leakage at a depth of 5 centimeters, it indicates that the stretch film has good toughness.