Flexible Packaging: Equipment and Methods
Manufacturing or converting plastic films which do not meet materials specifications can be catastrophic to the success of a business. Materials produced using improper testing techniques or inadequate testing instrumentation will result in losing key business accounts. Key test measurement parameters such as thickness, hot tack strength, sealing-strength and coefficient of friction must be kept within specifications for the material to perform.
Types Of Testing Used In Flexible Packaging
Tear testing measures the force required to continue the tearing of an initial cut in sheet materials. Models and weights are available to test material with a variety of strengths. This is also useful to evaluate strength of perforated materials. Tear testing has been performed for more than a half century to measure the mean internal resistance of substrates to the propagation of a deliberately initiated tear to determine its dynamic resistance.
A friction tester, also called a coefficient-of-friction (COF) tester, makes a measurement of a sheet-like substrate such as paper, corrugated, plastic film or paperboard which determines the angle of inclination at which one substrate affixed to a sled will begin to slide/slip against the surface of another substrate of a similar material.
During a test, an inclined plane is increased at a rate of 1.5 ± 0.5″ per second by an electric motor until the test block begins to slide. The initial movement of the sled is the slide angle or coefficient of static friction of materials. When the test block just begins to slide a photo-optical sensor automatically stops the inclined plane and the operator can read the slide angle result.
A variety of factors can effect the coefficient of friction tester measurements including abrasion, coatings, varnishes, printing and most importantly humidity.
Hot Tack Testing
Hot tack strength (the force to measure seal-strength while the film is still semi-molten) is too low, the film will not perform or run properly during the filling operation and the package may leak product after it is filled. Hot Tack test methods are sensitive seal-strength measurements and are critical for package validation. Seal-strength data used to measure the performance of medical packages such as sterilized medical devices can be critical to human health if compromised.
Hot Seal Testing
The heat sealer is designed to produce heated crimp seals for flexible packaging materials. The digitally controlled heat sealer allows independent upper and lower seal jaw temperature and accurately controls the temperature across the entire length of seal.
Contact angles as a testing method has over the years moved far outside the solid surface applications for which they originally were defined. When the contact angle concept was introduced for paper applications some fifty years ago, it was not commonly accepted by the industry because of difficulties in obtaining reliable correlation with experienced problems in printing, coating and gluing applications. Today the use of dynamic contact angle and absorption as a function of time has gained wide acceptance. This approach has even been suggested for applications such as tissues and powders absorbing a liquid droplet in fractions of a second.
Bending Stiffness and Resistance Testing
Bending stiffness is a characteristic associated with the rigidity of a material. This property is related to the modulus of elasticity of the material’s stiffness. Our Bending Tester was originally developed to produce a more concise, consistent measurement for the paper industry. This property is now used in a variety of industries including personal products, paper, flexible films, packaging and non-wovens.