UK Patent: GB 2369322, 9th June 2004

D R Blackburn, S F Bush, J M Methven, A J Neuendorf

Abstract

Polymer composites are comprised of a polymer matrix incorporating heat-shrinkable fibres disposed within the matrix to render the composite self-thermally forming.  The composite may be an elognate article or a sheet or plate.  Application of heat, e.g. localised heating, causing shrinkage of the fibres with self-thermal forming of the composite.  The heat-shrinkable fibres may be polyethylene terephthalate fibres.  The polymer composites may be formed by pultrusion.

To find more details go to the UK Patent Office.  At the box marked “Publication Number”, type in the patent number with GB at the beginning, then click on “Go”. To see the abstract, click on the blue link “View on Espacenet” which is just above the Patent number.

Paper to the 19th Annual Meeting of the Polymer Processing Society, Melbourne, Australia, 7th-10th July 2003

S F Bush with D R Blackburn and K J Jamieson

Abstract

This paper describes a new process for the production of certain types of smart composite materials, which under prescribed temperature fields spontaneously adopt prescribed shapes. These shapes are quite stable at room temperature plus about 50 ^oC. At or near the forming temperatures the shapes may revert to their original forms. Articles of this type can thus be seen as the polymer composite equivalent of bimetallic strips or shape memory metal alloys.

The purpose of this process which is under commercial development under the acronym SMARTFORM^© is to be able to make shapes from straight rods and flat sheet feedstock which are either impossible to mould or very expensive to do so by conventional processes. The key to the new process is the placing of mixtures of heat shrinkable synthetic and natural fibres in precise positions in the cross-section of pultruded profiles – notably rods and sheet. When subsequently cut to size, the rods or sheet elements are passed on belts through a series of heating zones for prescribed times which cause them to curl or twist into the shapes required. The process is economical since both the pultrusion stage and the thermal forming stage are continuous, not requiring manual intervention.

Paper to FRC 8th International Conference 13th-15th September, “Composites for the Millennium”

Published as ISBN 85573 5504

S F Bush with D R Blackburn, A J Neuendorf and J M Methven

Abstract

While much of fibre reinforcement of polymers has rightly concentrated on solid forms, there is a significant demand also for lightweight open structures of the wire-cage type. The paper will report results obtained from a variety of polymer-fibre compositions in wire form.

These wire-cage results draw on the laboratory’s extensively reported work on long-glass fibre reinforcement of thermoplastics and the pultrusion of both thermoplastics and thermosets. However, for the new wire-cage technology, the behaviour of the synthetic fibre and natural fibres in place of glass fibres has also been investigated. The results obtained show that for a number of significant applications these soft fibres are better than glass fibres in terms not only of their formability into wire structures, but also in terms of their elastic recovery from imposed stress or strain.

The development opens up a significant new field for polymer-fibre composites both as an alternative to existing metal wire structures in the food distribution and textile industries and as an alternative to certain solid structures more generally.

Paper to Institute of Materials Conference on Deformation, 24th-26th March 1997.

S F Bush and D R Blackburn

To see the text of the abstract, please click on the link IOMDeformation.

US Patent: 5,516,819, 14th May 1996

D R Blackburn, S F Bush, J M Methven

Abstract

A method of producing a thickened organic polymeric composition useful for molding and capable of resisting post-molding shrinkage after being crosslinked comprising a cross-linkable base resin dissolved in an unsaturated monomer, and an additive resin selected from saturated polyesters and saturated amide waxes, the additive resin being crystalline at ambient temperatures and having a melting point (T_m) below a temperature (T_c) at which the base resin cross-linking reaction proceeds at a significant rate. The base resin and additive resin have only a partial degree of compatibility. When cooled from a temperature between T_m and T_c to temperature between T_m and ambient the composition thickens, whereas, when it is heated to a temperature below T_c, it reverts to a flowable composition.

To see the patent in full, go to US Patent Office. On the first page click on USPTO Patent Full-Text and Image Database (PatFT), then under the heading “Searching Full Text Patents (since 1976)”, click on Patent Number Search and enter the patent number (with or without commas) into the “Query” box, then click on “Search”. To search for another US patent, click on Pat Num in the red display at the top of the page.

US Patent: 5,496,873, 5th March 1996

D R Blackburn, S F Bush, J M Methven

Abstract

A thickened organic polymeric composition useful for molding and capable of resisting post-molding shrinkage after being cross-linked comprises a cross-linkable base resin dissolved in an unsaturated monomer, and an additive resin selected from saturated polyesters and saturated amide waxes, the additive resin being crystalline at ambient temperatures and having a melting point (T_m) below a temperature (T_c) at which the base resin cross-linking reaction proceeds at a significant rate. The base resin and additive resin have only a partial degree of compatibility. When cooled from a temperature between T_m and T_c to a temperature between T.sub.m and ambient the composition thickens, whereas, when it is heated to a temperature below T_c, it reverts to a flowable composition.

To see the patent in full, go to US Patent Office. On the first page click on USPTO Patent Full-Text and Image Database (PatFT), then under the heading “Searching Full Text Patents (since 1976)”, click on Patent Number Search and enter the patent number (with or without commas) into the “Query” box, then click on “Search”. To search for another US patent, click on Pat Num in the red display at the top of the page.

Also

European Patent: EP 0396 625 B1, 14th November 1990

Abstract

Polymer compositions useful for moulding comprise a cross-linkable base resin, an unsaturated monomer in which the base resin is dissolved and a saturated additive resin which by itself is crystalline at ambient temperatures with a melting point (T_m) below that temperature (T_c) at which the base resin cross-linking reaction is designed to proceed at a significant rate. The composition is such that on cooling from a temperature between T_m and T_c, to a temperature between Tm and ambient the additive resin forms distributed microcrystalline domains connected severally by chains of the additive resin threading through the base resin chains. This produces a thickening network which may be reversibly broken down to the original additive resin molecules by heating to a temperature below T_c. The additive resin molecules swell the permanent base resin network created by the said cross-linking reaction which occurs during moulding, and thereby providing resistance to post-moulding shrinkage.

Paper published in the Journal of High Performance Polymers (1996) 8 67-82.

S F Bush with J M Methven and D R Blackburn

Abstract

This paper describes a new class of thermosetting polymer blends. The blends are now used commercially in the manufacture of sheet moulding compounds (SMC) where they exhibit important advantages compared with conventional systems. The new compositions comprise a cross-linkable base resin and unsaturated monomer in which the base resin is dissolved and a saturated additive resin which has a crystalline melting temperature T_m below the temperature T_r at which cross-linking occurs. Between T_r and T_m the additive and base resin form a single liquid phase, which on cooling thickens reversibly to a leathery sheet with no bulk phase separation. The paper describes the mechanisms underlying this viscosity switch phenomenon and the partial compatibility criterion used to select the resin-additive combinations which exhibit this behaviour.

Eleventh International Conference of the Polymer Processing Society, 1995?

S F Bush, with J M Methven, D R Blackburn and M Esfandeh

Introduction

Moulding compounds are generally mixtures of a cross linkable resin, a polymerisable monomer, fillers and discrete fibres, and a thickening agent. The most common composition is one in which the resin is an unsaturated polyester with residual carboxylic end groups, the monomer is styrene and the fibres are glass. The thickening agent is designed to turn a viscous fluid into a leathery sheet which can be rolled up, transported, and cut to fit a compression mould. The thickening agents are conventionally finely dispersed Group II metal oxide powders such as MgO. Among other interations hydrogen bonding occurs between -OH groups on the powder surface and the carboxylic acid groups in the resin. This bonding creates a complex network of resin and powder which typically increases the viscosity of the mixture from under 1 Pas to more than 10⁴ Pas over 48 hours. The bonding achieved is very sensitive to the concentration of acid groups, moisture content, and MgO particle size, thus imposing appreciable constraints on the production process. When a sheet of this material is placed in a mould and heated above about 110-120 ^oC the oxide-resin network dissolves and the resin flows freely through the mould cavity.

Paper (6-2-8) to the 10th International Annual Meeting of the Polymer Processing Society, Akron, USA, 5th-8th April 1994.

S F Bush with D R Blackburn, O K Ademosu, F B Yilmaz and P F Zhang

Introduction

Earlier papers^{(1, 2, 3, 4)} have described the factors affecting fiber-matrix cntacting, the organization of long fibers into coherent lace-like or mat-like structures, and the dependence of tensile strength on these two classes of variable. Equations for the mean number of touches¹ in the fiber structure and tensile strength² have been proposed which allow for the main variables present in moldings and extrusions, including differing matrix properties. Fiber management technology developed under the generic acronym SAFIRE⁴ (Self Assembling Fiber Reinforcement) has recently been applied commercially to practical moldings such as hard hats and pallets, in both of which examples impact strength is a key property.

Accordingly, a wide series of experiments has been carried out using the Izod method to determine the variation of impact strength as a function of the fiber length, fiber concentration, the fiber-matrix interface, fiber reinforcement structure and matrix properties. Both commercially available long-fiber granules and laboratory-compounded types have been used with different mold configurations and molding conditions for a variety of polypropylene and polyethylene matrices.

References

[1] S F Bush, Control of Fiber Structures in Melt Extrusion, 36 Ann Mtg Can Soc Chem Eng, Sarnia, Canada (1986) paper 32d.

[2] S F Bush, O K Ademosu, D R Blackburn, F B Yilmaz, Factors Affecting the Strength of Long-Fibre Reinforced Injection Moldings, Poly Proc Soc Eur Mtg, Prague (1992) paper 6-06.

[3] D R Blackburn and O K Ademosu, Factors Affecting Fiber-Matrix Contacting in Fiber-filled Granules, Poly Proc Soc, 9th Ann Mtg, Manchester 1993, Paper 6-14.

[4] S F Bush, Self Assembling Fibre Reinforcement (SAFIRE) processes, “Textile-reinforced Composites for Engineering”, Bolton Institute, Bolton, England, 12-14 January, 1994.

Paper at the Polymer Processing Society European Meeting in Prague, 21st-24th September 1992, Paper 6-06.

S F Bush with O K Ademosu, D R Blackburn and F Yilmaz

Introduction

To view the introduction, please click on the link: LFRmoldings