Method of forming articles from thermoplastic materials
US4153667A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 3, 1977 |
| Grant date | May 8, 1979 |
| Priority date | — |
| Expiry date | Oct 3, 1997 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29K2067/00
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A method is disclosed for enhancing the yield strength and density of polyethylene terephthalate and other similar thermoplastic materials which are susceptible to strain hardening. In the method, the plastic material is thermally conditioned to a temperature within a range conducive to molecular orientation, and then is mechanically conditioned by stretching in a first direction to a length at least about 2.6 to 2.75 times the original length. Thereafter, the plastic material is stretched in a second direction, with strain hardening and strain-induced crystallization increasing drastically substantially immediately upon the initiation of the second stretching operation due to the mechanical conditioning by elongation during the first stretch. The invention is particularly suitable for forming blow molded containers, where a blowable parison or preform is first stretched along its longitudinal axis to the critical length and is then extensively strain hardened while being blown to the configuration of the container.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.