An apparatus (1) for optical inspection of a mass of polymeric material (2) passing through an extruder (3) having a hollow extrusion cylinder (4) extending elongately in a longitudinal direction comprises an optical sensor (8) which can be operatively coupled to the extrusion cylinder (4) and having an infrared light emitter (8a) and a receiver (8b) configured to measure a measurement parameter representing an optical property of the polymeric material (2) inside the extrusion cylinder (4) and is characterized in that it comprises a plurality of the optical sensors (8) which can be operatively coupled to the extrusion cylinder (4) in a plurality of measurement sites located in succession and spaced from each other along the longitudinal direction and a processor (9) programmed to acquire a plurality of measurement signals containing the measurement parameters measured by the corresponding optical sensors (8) and programmed to process the plurality of measurement signals in order to calculate a corresponding plurality of values of a control parameter indicating a physical state of the polymeric material (2) as a function of a longitudinal position.

A method is described. The method comprising inputting starch into an extruder, inputting a plasticizer into the extruder, outputting an extrudate from the extruder, and chopping the extrudate output from the extruder into pellets. The extrudate includes the starch and the plasticizer. A pellet for manufacturing a biodegradable product is described. The pellet comprises starch and a plasticizer. A composition of the pellet, by weight percent, includes a starch weight percent representative of the starch included in the pellet and a plasticizer weight percent representative of the plasticizer included in the pellet. The starch weight percent is greater than the plasticizer weight percent and a density of the pellet is at least 0.5 g/cm.sup.3.

A method of manufacturing a film including cavities and formed from a polymer in which a cavitating agent is dispersed, the method including a step of extruding the polymer through an extrusion die equipped with adjustment actuators for adjusting thickness of the extruded film, and a step of stretching the film, as well as establishing a mapping function of the film on the basis of mass-per-unit-area profiles of the film before and after the stretching step, establishing a stretch profile of the film as stretched on the basis of the mapping function and of said transverse mass-per-unit-area profiles, and establishing a characteristic transverse profile that is characteristic of the film on the basis of the stretch profile and of a transverse profile of the concentration by mass of cavitating agent in the film as stretched that makes it possible to take into account the distribution of the cavities in the film; in which method the adjustment actuators are controlled as a function of said characteristic transverse profile.

The invention describes a method for producing a plastics film by a film-extruding machine, wherein at least two plastics materials from at least two reservoirs are fed together to one extruder or are each fed to a respective extruder, the plastics materials are melted in the extruder or in the extruders and are conveyed as a melt strand or as melt strands into a die head, the melt Strand or the melt strands are spread out flat in the die head and is/are extruded from a die of the die head as a melt film, and the melt film and/or the film sheet formed by cooling is/are drawn off by at least one take-off roll. It should particularly be noted that measured values are recorded by means of a measuring device for at least one property of at least one plastics material and/or at least one melt strand /d/ or the melt film and/or the film sheet and/or for a machine parameter of the film-extruding machine and that a first plastics material is a plastics material with varying material properties and a second plastics material is a plastics material with substantially constant material properties, wherein the first and the second plastics materials are fed to the extruder or the extruders in relative proportions, the relative proportions being varied according to the measured values for the property.

A method is described. The method comprising inputting starch into an extruder, inputting a plasticizer into the extruder, outputting an extrudate from the extruder, and chopping the extrudate output from the extruder into pellets. The extrudate includes the starch and the plasticizer. A pellet for manufacturing a biodegradable product is described. The pellet comprises starch and a plasticizer. A composition of the pellet, by weight percent, includes a starch weight percent representative of the starch included in the pellet and a plasticizer weight percent representative of the plasticizer included in the pellet. The starch weight percent is greater than the plasticizer weight percent and a density of the pellet is at least 0.5 g/cm.sup.3.