INFLUENCE OF LONG-TERM ANNEALING ON RESIDUAL STRESS DISTRIBUTION AND QUASI-BRITTLE FAILURE PROPERTIES OF TALCUM REINFORCED PIPE GRADE POLYPROYPLENE
In this study a polypropylene material with talcum reinforcement used for sewer pipes has been subjected to an annealing procedure at 80°C, roughly 60°C above the actual application temperature, in air for a time period of 18 months. As expected, examination of the material showed no significant decrease in mechanical or fracture mechanical properties due to the temperature exposure. However, samples stored at higher temperature showed better resistance against quasi-brittle failure in fatigue tests compared to unconditioned samples. This could mainly be attributed to the decrease of residual stress in the pipe wall. Even though pipes have been annealed for very long times above Tg, residual stress could not be totally relaxed within 18 months.
Cyclic tests on cracked round bars as a quick tool to assess the long term behaviour of thermoplastics and elastomers
Abstract The aim of this work is to demonstrate the applicability of the cracked round bar test recently developed for PE-HD to other polymeric materials. The main advantage of this new test method are rather short testing times for PE-HD materials used in long-term applications such as piping. Therefore, this test is of high interest for other polymers used in similar applications. Five thermoplastic materials used for plumbing (PE-HD, PP-B, PB, PVC-U, PA12), a technical polymer (POM) and an elastomeric material (H-NBR) have been tested. Scanning electron microscopy has been applied to investigate fracture surfaces. Results show that the test method seems to be basically applicable to all tested materials. Most materials showed similar fracture behaviour as postulated in literature, despite the high acceleration factor of the cyclic CRB test.
The Smoke of London: Energy and Environment in the Early Modern City
Prologue: the smoke of London Part I. Transformations: 1. The early modernity of London 2. Fires: London's turn to coal, 1575-1775 3. Airs: smoke and pollution, 1600-1775 Part II. Contestations: 4. Royal spaces: palaces and brewhouses, 1575-1640 5. Nuisance and neighbours 6. Smoke in the scientific revolution Part III. Fueling Leviathan: 7. The moral economy of fuel: coal, poverty, and necessity 8. Fueling improvement: development, navigation, and revenue 9. Regulations: policing markets and suppliers 10. Protections: the wartime coal trade Part IV. Accommodations: 11. Evelyn's place: fumifugium and the royal retreat from urban smoke 12. Representations: coal smoke as urban life 13. Movements: avoiding the smoky city Epilogue Bibliography Index.