Melt Volume Rate Research Articles

Influence of coloration on initial material properties and on thermooxidative ageing of a polyoxymethylene copolymer

Polyoxymethylene (POM) is a semicrystalline thermoplast of white natural colour. To meet the demands in other colours the material has to be coloured. Thus, the aim of the present study was to elaborate the influence of coloration both on the initial material properties and on the thermooxidative degradation behaviour of a POM-copolymer (POM-C). POM material with two different stabilising systems was used. A master batch on a POM substrate was added in a mass fraction of 3% to commercial distributed POM material to obtain the desired coloration. The tested specimens were injection moulded loudspeaker grills. Material properties were investigated on non-coloured and coloured samples before and after artificial ageing. The tests carried out were colour measurement, MVR (melt volume rate), mechanical testing (perforation resistance), DSC (differential scanning calorimetry) and TGA/MS (thermogravimetric analysis coupled with mass-spectrometry). Artificial ageing was realised by means of an oven storage at 140 °C for a duration up to 8 weeks to investigate the thermooxidative induced changes in the degradation behaviour. Test results showed first that the addition of a colorant had an influence on the initial properties and second that the degradation behaviour of the aged specimens depended not only on the presence of the colorant but also on the stabilising system of the material.

Effects of coloration on the physical and mechanical properties and on the thermal stability of polyoxymethylene

AbstractThe influence of coloring by using different batches on the crystallinity and the specific damage behavior of colored loudspeaker grills made from polyoxymethylene (POM) was studied. The investigations were performed by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) under dynamic and isothermal conditions, pressure oxidative induction time studies (pOIt), melt volume rate (MVR), and perforation tests. The loudspeaker grills were made by injection molding and colored with 3 mass% master batch, added to the pellets during processing. The grills were tested after injection molding (as‐received condition) and after accelerated ageing (oven storage up to 35 days at 140°C and UV irradiation). The results showed that the influence of the stabilizing system on the thermal and mechanical properties is stronger than the influence of the master batch substrate and the coloration. For the solely heat‐stabilized material, coloration can reduce the susceptibility for UV irradiation but not as effectively as a UV stabilizer package. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25: 63–72, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20060