A WEB STORAGE AND DELIVERY DEVICE
Publication Date: 2004-Feb-04
The IP.com Prior Art Database
A mobile web storage and delivery device for use at ambient temperatures, for supplying a semi-impregnated curable sheet material by simultaneously combining at least two feedstock material webs and a consolidation mechanism that combines the webs into an integral semi-preg by the application of pressure and, optionally heat.
A mobile web storage and delivery device for use at ambient temperatures, for supplying a semi-impregnated curable sheet material by simultaneously combining at least two feedstock material webs and a consolidation mechanism that combines the webs into an integral semi-preg by the application of pressure and, optionally, heat.
It is often desired to provide prepreg materials for applications in which the temperature of curing is low, for example below 100ºC: that is to say, easily achievable in moulds or presses heated by hot water or low-pressure steam. It is also a requirement for the economical operation of many industrial processes to be able to complete the curing cycle in a short period of time, for instance in a matter of minutes rather than hours. However, thermosetting resin assemblies that cure at low temperatures and in short times such as those just referred to have a serious problem in that the assemblies are likely to be unstable when stored for long periods at room temperature. For example, it would be common for such a reactive prepreg to become board-like and unusable after only a few days storage at room temperature.
Consequently, it is almost universal for prepreg materials to be shipped and stored in refrigerated conditions in order to keep the materials fresh and to ensure that the cure characteristics of the prepreg and the resulting properties of the cured composite component remain constant. The need for refrigeration has a number of disadvantages. It adds cost to the product because refrigeration is expensive. It uses large amounts of energy and therefore is undesirable from an environmental point of view; and the frozen prepreg must be thawed before use because otherwise water will condense on the prepreg, the water will vaporise during cure and this will cause porosity in the final composite part. The time spent thawing the prepreg is a considerable disadvantage to the customer, because this time is essentially wasted. This is particularly troublesome if the customer wants to respond quickly to rapidly changing orders for components.
A possible solution to the first problem consists in providing the curable material in the form of a semi-preg, in which the resin part of the assembly containing no curing agent, or only a low reactivity curing agent is present as a layer on one or both sides of the reinforcement and in which the curing agent or active part of the curing agent are deposited on the reinforcing fibres. By separating the reactive components in this way an improved out-life may be obtained. However, reaction may still occur at the interface between the resin layer and the reinforcement layer and therefore the out-life of the whole assembly may still be only of the order of days or weeks. It is necessary to store and ship the assembly in refrigerated conditions to guarantee good out-life. Also, not uncommonly, the resin film is capable of flowing unde...