Expertise in die drawing of polymers leads to new materials, new manufacturing processes, new products and a new company
Submitting InstitutionUniversity of Bradford
Unit of AssessmentAeronautical, Mechanical, Chemical and Manufacturing Engineering
Summary Impact TypeTechnological
Research Subject Area(s)
Chemical Sciences: Macromolecular and Materials Chemistry
Engineering: Materials Engineering
Summary of the impact
Research into die drawing of polymers at Bradford has resulted in a new
building material that is stronger and more durable than wood; and new
bioresorbable shape-memory polymers for use in medical implants that
reduce patient trauma and costs. The wood replacement material is
commercialised by the United Forest Products/Dow USA 2010 spin out company
Eovations LLC for use in a range of construction applications; the
bioresorbable shape-memory polymers have recently been patented (4 patents
filed) by Smith & Nephew for use in soft tissue fixations. These
impacts form part of a range of exploitations of our oriented polymer
Led by Phil Coates (Professor 1993-present) with Bradford academics John
Sweeney (Professor 1995-present) and Dr Phil Caton-Rose (Research
Assistant 1998-2000, PDRA 2000-2006, Lecturer 2006-present) as part of the
Polymer Interdisciplinary Research Centre, the team (in collaboration with
Leeds, IM Ward FRS) has worked on bridging the gap between the science of
solid-phase processing of polymers and advanced manufacturing technologies
since the early 1990s. Our particular focus is on die drawing of polymer
profiles and hot compaction of oriented polymer composite sheets. Our
original EPSRC-funded work (1998 onwards) was developed further through
partnerships with industry, investment by TSB and further EPSRC support
(2011 onwards), and has established the group at Bradford as the leading
solid-phase polymer orientation group in the world, evidenced by journal
publications, our key, unique, research reference books (1,2), patents,
and our industrial research contract portfolio.
The research has developed fundamental understanding of the mechanics of
solid-phase deformation behaviour of polymers, with new constitutive
relationships and physical modelling used to achieve molecular-related
understanding of deformation and feed computer modelling and control of
structure. This has underpinned inventive steps in the design and
implementation of batch and continuous processes to exploit the
significant property enhancements available through solid-phase forming,
particularly overcoming hurdles of process rates, and the novel
exploitation of filled polymers. Die drawing (1,3,4), invented by Coates,
involves pulling solid polymers at temperatures above their glass
transition but below their melting point, through converging dies,
achieving controlled oriented structures: physical properties increase
monotonically with draw ratio (cross sectional area change imparted), and
selected oriented polymers exhibit useful shape memory behaviour (3). It
is applicable for all length scales (micro to macro products) and a wide
range of polymers and cross sections, including biaxially oriented tubes.
Initially a batch process, we first demonstrated continuous processing,
with industry (5), and have developed fundamental modelling of orientation
processing and deformation (6).
Tensile drawing of filled polymers normally leads to failure.
However, our fundamental understanding of the stress, strain and
strain-rate fields incurred in drawing polymers through convergent dies
(1), supported by multi length scale finite element analysis, showed that
it was possible to control cavitation around fillers to avoid catastrophic
failure, by simultaneously strengthening the polymer matrix through
molecular orientation and development of crystal continuity (4). By die
design, controlled cavitation (in a combined compressive normal stress at
the die entry, but increasing tensile axial stress through the die)
produces lower density products, and orientation causes higher product
strength and stiffness, allowing continuous, high-speed production
(~metres per minute) of controlled property products (see Dow
We developed a micro-scale version of the die drawing process for
bioresorbable materials based on modified filled polylactic acids,
exhibiting shape memory (through recovery of the controlled orientation),
suitable for cementless in-body fixations (see Smith & Nephew
exploitation). Die drawing to a selected draw ratio allows matching of the
physical properties such as stiffness and strength of bone for joint or
soft tissue repair. The challenging requirement to have shape memory
activation at body temperatures has been addressed in our research and
This research has been supported commercially by BP, Solvay, Sabic, Dow,
Smith & Nephew, Netlon Tensar, Bridon International, Nylacast, and
Arterius in programmes from 1995 to date, totaling ~£1.25m. This work has
resulted in 11 jointly owned patents (6 published in the last year).
References to the research
1. Ward IM, Coates PD, Dumoulin M. (eds.) (2000) Solid Phase
Processing of Polymers. PPS Series, Cincinnati, OH: Hanser Gardener
2. Ward IM, Sweeney J. (2012) The Mechanical Properties of Solid
Polymers. (3rd Edn), Chichester: Wiley.
3. Coates PD, Caton-Rose P, Ward IM, Thompson G. (2013) Process
structuring of polymers by solid phase orientation processing. Science
China: Chemistry 56(8): 1017-1028.
4. Coates PD, Davies GR, Duckett RA, Johnson AF, Ward IM. (1995) Some
routes for tailoring of polymer properties through processing. IChemE
Transactions, ChERD 73(A): 753-770.
5. Taraiya AK, Nugent M, Sweeney J, Coates PD, Ward IM. (2000)
Development of continuous die drawing production process for engineered
polymer cores for wire ropes. Plastics, Rubber and Composites
6. Sweeney J, Caton-Rose P, Coates PD. (2002) The modelling of large
deformations of pre-oriented polyethylene. Polymer 43: 899-907.
(1), (3), and (6) are the three references best indicating the quality of
Evidence for the quality of the research is also evidenced by the award
of the following peer-reviewed and competitive grants:
EPSRC GR/M37417 Solid phase processing of polymers: stress-strain
laws for process and product property prediction, £134k, 1999-2000,
TSB CRD/134, TPAB019K The design & manufacture of smart materials
for orthopaedic applications, £245k, PI Coates, 2008-2010.
Innovation and Knowledge Centre RTD Proof of Concept: Smart Fixation
Devices for Soft Tissue Repair, Ref RG.MECH.476547, PI Coates
1.6.11-31.12.11, part of EPSRC/GP032483/1 Regenerative Therapies and
Devices, PI Fisher, Leeds (2009-2014).
EP/K004204/1 Science Bridges: Bradford-China Programme for
Pharmaceutical Sciences and Medical Technology, £1.25m, 2009-2012,
EP/G042365/1 GLOBAL Promoting research partnerships in Advanced
Materials for Healthcare, £499k, 1.4.12-31.3.13, PI Coates.
KTP Nylacast KTP008611 £180k, 2012-2014, PI Caton-Rose.
Details of the impact
Novel Polymer composite building materials — spin out company in the
Dow Building Products Inc. (a,b) had a goal of inventing the leading deck
board material, and approached us in 2004, because of our previous and
ongoing research and facilities in solid phase orientation processing of
polymers as well as our group's IP portfolio and track record with
industry in this area (including Tensar geogrids, Bridon International
Trulift elevator rope cores (b), and hot compaction technology resulting
in CURVTM material currently exploited by Samsonite). Dow
realized "that the development of thermoplastic composite solid state
die drawing technology in the world was now centred in the University of
Bradford" (a). In 2005 we started a Dow-funded project to produce a
light weight, high-stiffness material to act as a wood replacement in
civil engineering applications. 2005-2010 funding was £305k cash and
>£350k in-kind support (materials, technical input). This support
demonstrates the commercial value to the company of this product of our
research, underlined by their further US investments of $2m and then $16m
indicated below, and the significant patent portfolio now in place (a,c).
Our research and development work took polypropylene plus 46 wt% talc,
initial density of 1.34 g/cm3 and flexural modulus 1 GPa, to a
similar-to-wood product target density of 800kg/m3 and 4 GPa
modulus. Dow Building Products invested in the manufacturing technique and
product we developed, our knowledge allowing Dow "to significantly
accelerate its research efforts" (a). Our collaboration in setting
up a $2m pilot line in Michigan (2008-2009) to demonstrate continuous
processing, first demonstrated with Bridon International (b) in 2000, "contributed
to successful scale-up" and "provided valuable trouble shooting
capabilities" (a). The products replicate the structure of wood
(exhibiting a fibrous nature due to oriented polypropylene) with key
performance enhancements in weatherability, toughness, and reliability,
and include decking, cladding, fencing, and trim.
In 2010 Eovations LLC was formed in the USA by United Forest Products/Dow
to further develop and commercialize `Eotek' products (a,d). This $16m
investment created 64 jobs (13 in the research area). Our fundamental
contribution is explicitly credited on the Eovations web site (c,e) and in
the USA technical press (f), while the Eotek website (g) shows the
hurricane resistance of our materials. Dow filed 3 patents with us as
co-inventors, prior to the launch of Eovations, with 10 auxiliary patents
filed to date (a,h). We transferred ownership of specific polymer
orientation technology to Eovations, LLC in early 2010 (h), retaining the
rights to develop IP for our other potential routes to exploitation, e.g.
shape memory products for use in health care (see below) and new research
areas in health including oriented stents and anisotropic drug elution
products. The company has three lines in Michigan, and a new production
plant opening in Alabama. Because of commercial confidentiality in this
early phase of the company, they have not disclosed market share, but have
indicated it is millions of dollars (a). Follow-on products will include
marine, transportation, and recreation applications.
Shape memory — tissue repairs for all ages
Die drawn shape memory polymers products based on Bradford research and
aimed at the rapidly growing world market for both younger (sports
injuries) and older (arthritic/ osteoporotic/ trauma-involved) patients,
are being commercialised by Smith & Nephew (S&N), a global leader
in medical devices (i). Estimated 2013 markets (USA and Europe) for
shoulder fixations are 1,109,000 procedures, of value ~$856m and knee
ligament reconstructions at 982,000 procedures, of value ~$309m. Our
programme with S&N, building on our polymer orientation research,
focussed on high performance bioresorbables (2006-2008), bone and ligament
fixation (smart materials) (2008-2010) and design /manufacturing
feasibility for shape memory fixations (2013). Collaboration with S&N
continues, for example two joint EPSRC research proposals in 2012 each
included support (~£200k contribution from the company) on manufacturing
and biomedical materials development have been submitted.
Shape memory polymer implants match conventional tissue fixation devices,
with significant additional benefits as they reduce trauma to patients and
total costs. Being smaller devices they need smaller incisions with faster
patient recovery times, improve placement accuracy of fixations and reduce
product inventory, as an expanding device will be able to cover a range of
hole sizes. Our modified poly-L-lactic acids shape memory implants provide
sufficient locking stresses, with the required profile of decay of stress
for potential in-vivo applications, and have excellent biocompatibility.
Smith & Nephew filed four patents with us in October 2012. The
programmes with Smith & Nephew have been supported with £567k cash and
>£200k in kind. This support demonstrates the commercial value to the
company of this product of our research, underlined by their significant
patent portfolio now in place (i).
Sources to corroborate the impact
Contacts for indication of impact (of the specified products and our
world-leading capabilities in solid phase orientation processing) include:
a. Research Director of Eovations LLC, and the key contact for the full
research cooperation with Dow; he can comment on the unique position
Bradford holds worldwide for solid phase orientation processing of
polymers and polymer composites.
b. Technical Manager, Bridon International — interests in exploitation of
oriented polymers in cable applications (e.g. engineered elevator cores,
marine cables) and continuous die drawing — the first successful
demonstration of this was with Bridon.
— the page on the web site for the Dow/ Universal Forest Products spin
out, Eovations LLC commercialising our solid phase orientation technology,
which explicitly credits us.
d. General Operations Manager, Universal Forest Product Incorporated
(UFPI, who own the majority of Eovations) liaison with Eovations; he can
comment on UFPI's vision for the technology.
Article in US trade magazine, Plastics Today, published April 25th
2013 (available as pdf if required) — extolling the virtues of Eotek
products, and clearly crediting the Polymer IRC at the University of
— a striking example of hurricane impact resistance in the oriented
polymer composite building products, achieved by our technology.
h. Recently retired IP Manager from Dow Building Products, worked on the
IP for the Bradford/Dow/Universal Forest Products (UFPI) large scale
thermoplastic composite solid state die drawing technology.
i. Head of Biomaterials, Smith & Nephew: — able to reflect the value
of Bradford's collaborative research on shape memory materials, with input
from S&N colleagues in Boston and St Louis.