ARTIFICIAL SPIDER WEB - HUGO HUAS TITOUAN JÉRÔME - DIVA
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DEGREE PROJECT IN TECHNOLOGY, FIRST CYCLE, 15 CREDITS STOCKHOLM, SWEDEN 2021 Artificial Spider Web Selection of Polymeric Materials for Special Effects Applications HUGO HUAS TITOUAN JÉRÔME KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF INDUSTRIAL ENGINEERING AND MANAGEMENT
Artificial Spider Webs
Abstract
Artificial spider webs are a challenge for the special effects companies. The natural spider
webs are displaying incredible mechanical properties combined with a low density and a high
stickiness making them hard to reproduce. Throughout this project the aim is to produce artificial
spider webs using a specific manufacturing method, pouring a mix of polymer and Naphtha oil
into water to form the webs. This method was used in previous cinematic applications giving
outstanding results for the artificial spider webs. Unfortunately, due to the loss of it, the specific
parameters, tools and raw materials have to be found. A material selection is given leading to a
specific choice of thermoplastic polymers. The selected material are then tested manually so they
can be listed depending on the results obtained. Finally, the most promising material seems to be
TPU, thermoplastic polyurethane; thanks to his excellent mechanical properties and good visual
aspect.
Sammanfattning
Konstgjord spindelväv är en utmaning för specialeffektföretag. De naturliga spindelnäten
visar otroliga mekaniska egenskaper i kombination med låg densitet och hög klibbighet vilket
gör dem svåra att reproducera. Under hela detta projekt är målet att producera konstgjord
spindelväv med hjälp av en specifik tillverkningsmetod, hälla en blandning av polymer och nafta
olja i vatten för att bilda näten. Denna metod användes i tidigare filmiska applikationer som ger
enastående resultat för de konstgjorda spindelnäten. Tyvärr, på grund av förlusten av det, måste
de specifika parametrarna, verktygen och råvarorna hittas. Ett materialval ges vilket leder till ett
specifikt val av termoplastiska polymerer. Det valda materialet testas sedan manuellt så att de kan
listas beroende på de erhållna resultaten. Slutligen verkar det mest lovande materialet vara TPU,
termoplastisk polyuretan; tack vare hans utmärkta mekaniska egenskaper och bra visuell aspekt.
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Artificial Spider Webs
Contents
Abstract i
Sammanfattning i
1 Introduction 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Project goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 Ethical and socials aspect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Theoretical study of real spider web 4
3 Manufacturing process 7
3.1 Existing process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Desired process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4 Material selection 9
4.1 Selection strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2 Desired properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3 EDUPACK Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5 Experimental method 14
5.1 Testing process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1.1 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1.2 Variable parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.2 Raw materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6 Results 16
7 Discussion 18
7.1 Results analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8 Conclusion 19
9 Acknowledgement 20
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Artificial Spider Webs
1 Introduction
1.1 Background
Since the invention of cinema by the Lumière’s brothers, there has always been a desire to
create more sophisticated movies. This willingness can mostly be reached thanks to special effects.
They make the movies more realistic and allow the introduction to imaginary worlds where people
can fly or change appearance at will. Moreover special effects are not only reserved for fantasy
applications. In fact they also allow the studios and producers to immerse the viewers into the
movie universe by hyper realistic decorations such as typical buildings of the IXth century for a
film on the medieval age or spider webs around the lair of a huge spider. This second example will
be the aim of this project.
Arclight [1] is a Sweden company specialised in cinematographic special effects founded in
1994. They worked on more than 80 feature films including Harry Potter, Fast and furious or
even Hamilton more recently. Today, there principal income domain is the creation of decorations
for theme parks, municipalities, events or festivals. Among these things, Halloween is a really
important period as it requires a lot of decoration, including spider webs.
1.2 Project goal
The aim of this project is to produce spider webs for cinematic visuals effects or decorations
throughout a specific technique that we have to use. In fact it was used in the Lord of the Rings
(LOTR) and The Hobbit trilogies directed by Peter Jackson. These films were absolute success as
epic fantasy adventure films, adapted from the novels wrote by J.R.R Tolkien, see movie poster
Fig. 1. They were critically acclaimed winning many awards at the Academy Awards and still are
true reference in fantasy movies almost twenty years later. One reason of their success was the
special effects that were quite innovative at that time, unfortunately not much of information is
available on these techniques and the materials they used especially the one for the spider webs.
In the Behind The Scenes videos, many descriptions are made about the visual effects used in the
films : stone walls mostly made of polystyrene blocks or in our case the conception of the artificial
spider webs for the Shelob’s scene in the third LOTR : The Return of The King, Shelob being the
name of the spider, see Fig.2.
Currently, Arclight [1] has already a production method to design spider webs. It consists
of a hot melt gun which heat a hot melt adhesive and ejected it to shaped the web. Despite the
advantages of this technique such as an easy and cheap processing, the final visual result was not
satisfying compare to the spider web seen in the Lord of the Rings that were looking much more
like the original ones. Moreover, they are way more manageable compared to the gun where it
is necessary to aim at the exact wanted spot. The on set art director of LOTR used a specific
method to produce the webs but unfortunately for the cinema, he has died without recording the
method.
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Artificial Spider Webs
Figure 1: Movie poster of The Lord of the Rings : The Return of The King [2]
Figure 2: Artificial spider webs used in the LOTR movies [3].
In this project, the following method will be used : an elastic polymer is melted along with
Naphtha oil and then put in a cold water bath where the web is manually shaped. The strategy
will be to select a list of polymers fulfilling the defined requirements. Then, those materials will
be tested and the result analysed to derive which one is more suitable for this specific application.
The formed webs should then be stretchy and sticky with a visual aspect very close to real ones.
Afterwards Arclight [1] should be able to used it for their annual production of artificial spider
web.
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Artificial Spider Webs
1.3 Ethical and socials aspect
As this project work is directed by a private company, i.e. Arclight [1], the ethical and social
aspects have been taken care of but in the background. The purpose is above all to manufacture
decorations in an entertainment context. Therefore, the found process will be only used for these
specific application. However, it is possible to imagine some other utilisation, especially if the
mechanical properties of the artificial spider web tends to look like the real one. In the actual
environmental context, it is important to take care of the ecological impact of this process. Thus,
have a low melting point or be recyclable could be a criterion for the future selected material.
This project fits into two different goals fixed by the UN (United Nations). The first one
is the goal n°3 which involves a well being at all ages. As the artificial spider web will be used
to improve the quality of films or Halloween decorations, it is going to improve also the citizen’s
entertainment and therefore their life quality. The goal n°9 is also concerning this work as the
subject is about an industrial process. As said before, the environmental impact must be taken
care of as much as possible, whether in terms of materials or the process itself.
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Artificial Spider Webs
2 Theoretical study of real spider web
A spider has the capacity to design a spider web, also known as cobweb, see Fig. 3. This is a
structure made of spider silk yarn that is extruded from its spinnerets. Spider silk is known as one
of the most interesting biomaterial. Extensible, strong, though, fine and adhesive these properties
makes spider silk very attractive for numerous applications such as textile, biomedical materials
and in this case visual effects [4].
Figure 3: Orb spider web [5]
There are different types of silk that are used by the spider for specific objectives. Usually,
spider can generate three silk yarns with particular characteristics. The first one, extracted by
the large ampullate gland, will be used for frame of the web or for the dragline so the spiders
can suspend themself to the ceiling or other locations. Then, a spiral line is added thanks to the
flagelliform gland which make a more ductile silk. And finally, the aggregate gland is going to
create sticky ball that take place all along the spiral line. In this project, the aim is to find a fair
balance between this three types of silk. A good stretchability is required while keeping a good
strength and not forget the mandatory adhesive properties.
These properties, mainly the mechanical ones, can be explained by its chemical composition.
The spider silk is a semi-crystalline protein fibre made of an amino acid sequence. Dragline silk
for instance, one important type of spider silk, is mainly composed of two proteins : Spidroin
I and Spidroin II [6]. Chemically speaking these proteins are composed of a core sequence of
repetitive polyalanine and glycine-rich amino acid along with non-repetitive amino and carboxyl
groups [7]. The difference between Spidroin I and II lies in the sequence of the glycine-rich domains
: for Spidroin I (GGX) is abundant, G representing glycine and X a variable amino acid (alanine,
tyrosine, leucine or glutamine) [4]. For Spidroin II the sequence is (GPGXX) where P represent a
proline amino acid [6]. This repetitive region is the main part of the silk and can contain hundreds
of repeated units of amino acids. This region can vary between the different types of silk but the
spidroin terminal domain (C and N) is conserved, see Fig. 4 [8].
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Artificial Spider Webs
Figure 4: General structure of a spider from its chemical structure : a) orb-web with different
silks of a Nephila clavipes spider. b) SEM image of a silk at 10µm. c) Skin-core structure of a
silk composed of a lipid coat and glycoprotein. d) silk fibril composition : repetitive amino acid
core and N/C-terminal [9, 10].
The repetitive amino acids units are highly responsible of the mechanical properties of the
silk. On one hand the presence of long segments of poly-alanine makes the silk stronger and on
the other hand the glycine-rich region is responsible of its flexibility and extensibility [8]. It fact
spider silk is mostly known for its mechanical properties, especially dragline silk. What makes it so
special is the combination between incredible strength and great elasticity. At equal weight, silk is
stronger than steel but can be deform approximately one hundred times more. To set values on this
characteristics, a dragline can have a tensile strength as high as 1750MPa [4], which is comparable
to high performance steel, and silk yarn can be stretched up to five times their initial length
without breaking. This particular pair of properties involves a phenomenal toughness, larger than
the toughness of Kevlar and practically equal to polyaramid filaments issue from modern polymer
fibre technology. It means that cobwebs can absorb a huge amount of energy and plastically deform
without fracturing [4]. In fact comparing to other natural or synthetic fibrous polymers spider silk
have a higher breaking energy for a diameter between 0,2 and 1,0mm [4].
Considering the density, as seen in the previous paragraph, silk is mainly consisting of protein
and therefore its density is really low compare to other materials with similar mechanical proper-
ties. For instance spider silk has a density around six time lower than steel but with comparable
mechanical properties.
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Artificial Spider Webs
Then, let’s focus on the visual aspect. Spider web are white and most of the time opaque.
Moreover, they have a really specific shape: the strongest silk yarn are drawing from the exterior
to the centre and form the "radius" of the web. Finally they are link by a spiral line. It is necessary
to recreate this shape because spider web are assimilate to it by the public imagination.
Last but not least, the adhesive properties are very important. For visual effect application,
one have to be able to shape and stick the webs everywhere. Theoretically spider make their webs in
order to catch preys. The adhesive property of the silk is due to the presence of aqueous adhesive
glue attached to the axial fiber, see Fig. 5. Many studies have tried to explain the chemical
composition of these glue droplets but many questions remain unsolved. One explication would be
that it contains a concentrated solution of hygroscopic components related to neurotrans-mitters
[11].
Figure 5: Spider silk fiber with aqueous glue droplets [11]
6Artificial Spider Webs
3 Manufacturing process
The technique used to design a product is almost always determining in regard of its future
properties. This is why it is important to choose carefully how to process the artificial cobweb.
Different manufacturing techniques will give different mechanical and visual properties.
3.1 Existing process
Currently, there is an efficient and cost effective method to produce spider web for decoration
that Arclight [1] and others special effect company were using. This process requires a hot melt
adhesive (HMA), also called hot glue, and a hot glue gun. HMA are part of the thermoplastic
adhesive class of material. It means that at room temperature, HMA are in solid form, usually
cylindrical sticks of various diameter, and must be heated to be shaped. The gun is composed of a
heating element which will melt the polymeric glue. In the meantime, the glue is pushed through
the barrel of the gun. Then, the melted adhesive is ejected by the heated nozzle. As it is still hot,
the glue is sticky and can be elongated to form the wanted shape.
So far, Arclight company [1] was using a SP420 hot melt adhesive which must be heat to 180°C
in order to squeeze it through the gun [12]. This method shows many advantages such as an easy
processing and a low price. However, some issues prevent this technique to be totally satisfying.
First, the melted glue was ejected really fast from the gun, which involves a bad accuracy in the
location of the cobweb. Moreover, as the glue solidification rate is high, once the HMA is stick
anywhere, it is complicated to change its location. Last but not least, the visual aspect was not
sufficient. In fact the obtained spider web were too thin and too brittle for many applications, see
Fig.6. The public was not able to see them clearly.
Figure 6: Artificial spider web obtained thanks to hot melt adhesive and a hot glue gun
[13]
7Artificial Spider Webs
3.2 Desired process
In the LOTR Behind the scenes, it is possible to see the on set art directors responsible of the
visual effects showing and describing the technique they used for the spider webs. The principal
raw material for this technique is a synthetic polymer in solid state: pellets. The type of polymer
and the specific name is unknown thus the first aim of this project is to found a polymer that can
be used for this technique. After that the pellets of polymer are melted along with naphtha oil so
that the melted polymer get the right stickiness afterwards. To do that they used a classic fat fryer
reaching a temperature of 220°C, the instructions are clear: this temperature has to be precise in
order to obtain the right stickiness of the melted polymer. Plus, at that time the polymer used
seemed to have a flash point very closed to its melting point. Thus the temperature needed to be
very accurate to avoid fire [14].
Once the mix had the desired fluidity, they had to use heated tools to form the webs, this
was because the polymer has started to gel and solidify just below its melting temperature. Thus
the tools used were preheated at 200°C or can be the ones used for stirring in the fryer [14]. Since
we might not find this specific polymer the thermal properties may differ thus we may not have
to heat the tools. In our case this technique will be adapted depending on the properties of the
polymers we will test.
To form the webs, this technique needs a water bath with enough space to make circular
webs and enough depth (about 10cm). Then taking a brush or any other suitable tool, the webs
are formed pouring the melted polymer in a water bath [14]. Due to the low temperature of the
water, room temperature, the polymer will become rubbery-solid quite fast. These films that have
to look like spider silks could be afterwards be taken out by hand and formed to any shape. Thus
this method allows to have very stretchy and sticky polymer in such a way that the malleability
is high.
8Artificial Spider Webs
4 Material selection
4.1 Selection strategy
Starting the research to find the proper polymer that would be suitable for this application
not so much information was given apart from the process technique. Firstly the Behind The
Scenes of the Lord of the Rings specify that the proper melting temperature is 220°C precisely but
from another source the used polymer has a melting temperature of about 190°C and a flash point
of 210°C so a range of temperatures between 190°C and 230°C would be good for this application
[14].
The purpose is to make artificial spider webs that look likes the real ones so the principle
axis of research is visual. The mechanical properties for example aren’t to be carefully considered
apart from the elongation, in fact the young modulus and the elongation (%strain) are the ones
needed to be considered. Though an interesting outcome would be artificial spider web that would
also have the same mechanical behaviour as natural ones but as specified before many researchers
have been trying to reproduce them and the techniques they use are far more sophisticated.
To be stretchy and sticky the most suitable polymer class are the elastomers but most of
the elastomers are thermosets such as rubber. The main properties of this kind of polymer is that
they can be irreversibly hardened by curing: crosslinking occurs between the polymer chains [15].
This implies that they can’t be melted: phase transformation from solid to liquid. In fact this
crosslinking process leads to strong bonds formation that cannot be broken by heating. Thermoset
polymers are thus heat tolerant and knowing that the polymer has to be melt to form the webs
afterwards this class of polymer is not suitable. The other class of polymers are thermoplastics, the
differences lies into the ability to be melted by heat application. Indeed the weak bonds between
the monomer chains are broken by heat application, softening the polymer. Then, during the
cooling, thermoplastic polymers will harden and this cycle can be done as many times as wanted.
Thus the most suitable polymers would be thermoplastics elastomers.
To find the suitable polymer for making spider webs, the strategy is the following: firstly few
numbers of polymers have to be selected upon their properties (mechanical, thermal, visual...),
these polymer will afterwards be tested using the melting-water bath technique described pre-
viously. For the polymer selection, the material selection software GRANTA EduPack is used.
Throughout the set of specific properties the software will sort out the corresponding materials
that are in the range of the wanted properties.
Although the material database is large, some specific materials are not included. Thus, by
directly contacting polymer manufacturers, they may propose some suitable products that might
be worth to test.
4.2 Desired properties
This section is know focusing on setting the most interesting properties. Firstly let’s consider
the thermal properties. From the sources that are obtained the range of melting temperature that
would give the suitable polymers is between 160°C and 250°C, this range is over-evaluated because
this melting temperature can depend on many factors such as the oil, the fryer, the thermometer,
the operating conditions. Thus knowing that the polymer used has a melting temperature between
190°C and 220°C the previous range is set : 160 C < Tm < 250 C.
9Artificial Spider Webs
Another temperature that has to be considered is the glass transition temperature which
described the amorphous transition of a polymer. Knowing the application: tacky and expendable
at room temperature, this material property has to be lower than this temperature : Tg < 20 C.
Considering now the mechanical properties : the Young’s modulus, the elongation or the
%strain at failure are essential when talking about spider webs. The minimum for the Young’s
modulus that is set is 0,1GPa / 100MPa, this is a first estimation to sort out the most interesting
polymer but the ones that are below won’t be excluded as potential solution. This is because,
regarding the Young’s modulus of all the different class of materials, the elastomers have generally
a lower value than 0,1GPa and as the class considered is specific (thermoplastic elastomers) this
value of Young’s modulus can be slightly different.
Then, one of the mechanical property that is important is the elongation: basically this is
how much one can expand the material by applying a tensional stress until it breaks. For the
application this is very important because the spider webs are formed in the water so that they
can be taken out by hand, be expanded and be stuck anywhere. This elongation property is then
set as at least 300%, this means than the material can be expanded at 300% of its original length.
This value is quite low for all the elastomers existing so it will mostly exclude the polymer that
aren’t elastomers. Considering the application (decoration) it doesn’t have to be a lot more than
300%.
Moreover, it is important to notice that the material must be non toxic. As the final product
will be used in attendance of living beings, this is mandatory and can’t be avoided.
Now come the most important properties to consider : the visual aspect. In fact the appli-
cation requires a specific visual aspect of the webs based on the LOTR scenes, see Fig.7. What
we can see is that they are not as white as one can predict but more translucent and can even be
yellow in appearance. In order to have the best possible aspect, black raw polymer materials will
be avoided. The selected colour is ideally translucent or maybe white/beige. In the scene they are
also shiny as they can be seen clearly in the darkness of Shelob’s lair. This is one of the purpose
of naphtha here.
Figure 7: Visual aspect of the artificial spider webs used in LOTR [14].
10Artificial Spider Webs
4.3 EDUPACK Analysis
Once the required properties have been fixed, they can be listed, see Table.1 below. From this
selection of properties, a range of material can be selected fulfilling these criteria. These materials
will be tested later, when trying to recreate the artificial spider web out of them. The selection
is going to be done thanks to GRANTA Edupack [16], a database of materials and processes
information.
Table 1: Properties set in GRANTA Edupack to filter the potential
material efficient to be used for artificial spider web
Young modulus E > 0,1 GPa
Elongation 300% strain
Melting point 160 C < Tm < 250 C
Glass transition temperature Tg < 20 C
Visual aspect Opaque - Translucent
Toxicity None
These six criteria lead to a list of twenty materials among the GRANTA Edupack database:
TPO (thermoplastic polyolefin), TPU (thermoplastic polyurethane), TPV (thermoplasticvulcan-
izate), TPC/TEEE/COPE (thermoplastic polyester elastomer), POM (polyoxymethylen),PVDC
(polyvinylidenechloride), PVDF (polyvinylidienefluoride), PP (polypropylene) and PE (Polyethy-
lene). Some of them are present several times in the list, TPV or TPO for instance. They don’t
have the same manufacturing process or they have a different molecular arrangement. Therefore
their properties such as the melting point or the Young’s modulus can be slightly different. Thus, in
order to list them, they will be classified distinguishing their production method or their hardness.
By filtering the materials by their melting point and their Young’s modulus, it is possible
to eliminate some class of materials such as metals, foams or ceramics. As shown in Fig.8, the
selected materials are part of the polymer family, whether plastics or elastomers, and they are all
thermoplastics.
The Fig.9 indicates the relatively good tensile strength of the selected materials while showing
their huge capacity to be stretched. Silk fiber has been highlighted on the Ashby diagram and
it reveals its incredible combined properties of deformation and strength. The polymers that
have gone through all the requirements tend to approach the characteristics of Spider viscid silk,
this means that the previous criteria appear to be relevant. It’s clear that the strengths of the
elastomers don’t reach the one of spider drag-line silk. However, as the wanted product is going
to be used to decorate, it doesn’t really need to be so strong. The material can be sufficient if it
has a tensile strength good enough to support its weight and few shocks, depending on the specific
application.
11Artificial Spider Webs
Figure 8: Ashby diagram of the Young’s modulus as function of the density. The large bubbles
represent the different classes or materials and the red/blue coloured ones represent the materials
fulfilling all the requirements [16]
Figure 9: Ashby diagram of tensile strength in function of the elongation before breaking, with
the coloured materials representing the ones that fulfilled all the requirements [16]
On another hand, one of the requirement seen before is the adhesive ability. However, this
criterion hasn’t been investigated on GRANTA Edupack because of a lack of data. Therefore, it’s
necessary to do some additional research leading to the selection of elastomers with good adhesive
characteristics and properties matching as closely as possible to the wanted ones.
12Artificial Spider Webs
By using the Polymer database of the Chemical Retrieval On the Web [17], other polymers
have been found with excellent adhesive properties, especially the class of thermoplastic styrenic
elastomer (TPS). They are the thermoplastic elastomers having the best rubber-like behaviour
and their current applications are bonds and adhesives among others. TPS have a hard segment
composed of polystyrene (PS) and are distinguished by variations in the soft segment: either SIS
(S: Styrene, I: Isoprene), SEBS (E: Ethylene, B: Butylene), SBS (B: Butadiene) or SEPS (P:
Propylene) [18]. The hard segment provides strength and rigidity thanks to the cross-linking point
while the soft segment contributes to the elasticity of the material.
Typical TPS don’t fulfilled the requirements mostly because of their low Young’s modulus.
However, as said previously, the threshold was previously set and therefore it can be changed. It
was decided to investigate the SBS and SEBS because their properties were more comparable to
the desired one. For example, their Young’s modulus are between 0,01 GPa and 1 GPa while the
one of SIS is in the order of 0,1 MPa [16].
Finally the material analysis using GRANTA EduPack allow to sort out many polymer that
are classified in Table 2. As specified previously the criteria of classification is the hardness. There
is groups of hardness depending on the durometer indenter named: A, B, C, D, DO, E, M, O,
OO, OOO, OOO-S, R. Then in each group, a value from 0 to 100 is assigned with higher values
indicating harder materials [19].
Table 2: List of all the polymers fulfilling the set parameters in GRANTA EduPack : the elastic
strength, the melting point and the elongation [16]. The polymer abreviations are the following :
TPO, TPU, TPS-SBS, TPS-SEBS, TPV, TPC/TEEE/COPE, POM, PVDC, PVDF, PP .
Family Designation Elastic strength (Young’s Modulus) [GPa] Melting point [°C] Elongation [%]
TPO PP+EP(D)M Shore A90/D40 0,178-0,236 164 - 183 468 - 755
TPO PP+EP(D)M Shore D50 0,346 - 0,513 163 - 184 484 - 743
TPU (Polyester aromatic) Shore D50 0,131 - 0,184 150 - 180 467 - 547
TPU (Polyester aromatic) Shore D60 0,235 - 0,302 160 - 172 428 - 461
TPS: SBS Shore A50 0,00117 - 0,00183 180 - 220 528 - 891
TPS: SBS Shore A70 0,00285 - 0,00445 160 - 190 550 - 863
TPS: SBS Shore A90/D40 0,0975 - 0,103 160 - 200 553 - 773
TPS: SEBS Shore A50 0,00117 - 0,00183 180 - 220 511 - 653
TPS: SEBS Shore A80 0,00445 - 0,00695 180 - 220 536 - 703
TPS: SEBS Shore A90/D40 0,00868 - 0,108 185 - 225 519 - 703
TPS: SEBS Shore D50 0,016 - 0,025 180 - 220 434 - 467
TPV PP+NBR shore A75 0,00356 - 0,00556 182 - 222 260 - 300
TPC/TEEE/COPE Shore D40 0,0708 - 0,115 171 - 210 226 - 324
TPC/TEEE/COPE Shore D50 Ecdel-type 0,11 - 0,184 200 -210 300 - 400
TPC/TEEE/COPE Shore D55 0,192 - 0,265 199 - 216 233 - 368
Thermoplastics (plastic) POM (copolymer) 2,76 - 2,9 160 -170 60 -300
Thermoplastics (plastic) PVDC (copolymer) 0,11 - 0,17 163 - 181 250 -300
Thermoplastics (plastic) PVDF (copolymer) 1 -1,31 168 - 170 300 - 500
Thermoplastics (plastic) PP (homopolymer) 1,34 - 1,59 161 - 170 168 - 598
TPU (Polyether aromatic) Shore D45 0.0422 - 0.0546 188 - 215 457 - 512
TPU (Polyether aromatic) Shore D75 0,336 - 0,353 180 - 220 344 - 386
TPU (Polyether aromatic) Shore A85 0,0197 - 0,0275 157 - 200 520 - 605
TPU (Polyether aromatic) Shore A85/D35 0,0204 - 0,021 157 - 200 552 - 645
TPU (Polyether aromatic) Shore A70 0,01 - 0,012 139 - 181 688 - 772
13Artificial Spider Webs
5 Experimental method
The experimental part of the project hasn’t been done yet because of issues encountered
while buying the wanted polymers and the delay consequent to the order. The tests will be done
in the following weeks, as soon as the materials are received.
Once the materials fulfilling the requirements have been bought, they must be tested to
experimentally know which one is better for this application.
5.1 Testing process
The experiment must be the closer possible from the manufacturing process of the spider
web in LOTR such as explained in section 3.2. The polymer is going to be melted with naphtha
oil and then put in a water bath where the web will be shaped.
5.1.1 Equipment
The equipment available is composed of:
• A deep fat fryer able to heat up to 200°C
• A saucepan to perform a double boiler
• A basin for the water bath
• A metallic stick to stir and shape the web
• Naphtha oil (Power Fuel Primus) to be mix with the tested polymers and used as a hot liquid
for the double boiler
• The bought polymers previously listed
• A thermometer to control the temperature of the polymer and avoid the flash point
• All the safety equipment needed: mask, protective glasses, anti-burn clothing, gloves and a
fire extinguisher
As the naphtha vapour is hazardous to health, the tests will take place in a ventilated room.
5.1.2 Variable parameters
In every experimentation, there is one or few parameters that will vary and influence the
final result. In this case, the parameters will be, of course, the different materials tested but also
the amount of naphtha oil added to the melted polymer and the temperature of heating.
The amount of naphtha oil will act on the viscoelasticity of the material but also on the visual
aspect of it. A brilliance around the spider web thread is going to appear which will highlight the
sticky behaviour of the web. Moreover, it is necessary to mix the polymers with a non soluble
product such as the naphtha oil. It will allow the web to be shaped in a water bath. Otherwise,
the polymer is going to dissolve in the water and it won’t be possible to produce a net web.
14Artificial Spider Webs
On another hand, the temperature of heating is also very important. First, some elastomers
have a flash point, which means that when they are heated to a specific temperature, they go up
in flames. Therefore, it is necessary to be careful and not reach this point for obvious security
reasons. However, the polymer must be heated enough to obtain the needed viscoelasticity which
will allow the shaping of the web. Finally, the stickiness will be defined, among others, by the
heating temperature.
For the previous reasons, tests will be conducted with different heating temperatures and
different amount of naphtha oil.
5.2 Raw materials
To perform the testing, samples of the selected polymers, section 4.3, have to be bought by
contacting several polymer suppliers in Sweden and Europe. As these are very specific polymer
their sale is not widespread. Managing to find supplier selling these thermoplastic was harder than
expected. Finally two suppliers have been found and contacted. The first one is Sigma Aldrich,
a Germany company working in the fields of chemicals, bio-technologies and life science [20].
The second one is Bjorn Thorsen, a Danish distributor of chemicals products for other material
manufacturers such as ExxonMobil or Lubrizol [21].
15Artificial Spider Webs
6 Results
From the EduPack analysis the list of the suitable polymers for spider web application was
sort out. The most important part is now to test them to select the one that gives the best result
of spider silk. Since the equipment is still under delivery, the experimental tests haven’t been
conducted yet. They will be done by Arclight [1] as soon as they can. Nevertheless, a material
analysis can be conducted from the list of selected materials. All the polymer that are going to be
tested are classified in the following table, see Table.3.
Table 3: List of the types of polymers that was possible to buy with their form, color and weight
available: PP, PVDF, PVDC, POM, the SBSs, SEBS, Poly[4,4’-methylenebis(phenyl
isocyanate)-alt-1,4-butanedial/di(propylene glycol)/polycaprolactene, Flexmark 7 Polyurethane
coming from Sigma-Aldrich company and Estane 55887 NAT 055, SantopreneTM 8211-65,
Vistamax r 3000, Vistamax r 3588 FL coming from Bjorn Thorsen company.
Name Family Form Colour Mass (g)
Polypropylene (PP) Thermoplastics (plastic) pellets colorless 1 000
Poly(vinylidene fluoride) (PVDF) Thermoplastics (plastic) powder white 100
Poly(vinylidene chloride) (PVDC) Thermoplastics (plastic) powder white 100
Polyoxymethylene (POM) Thermoplastics (plastic) granule white 500
Polystyrene-block-polybutadiene-block-polystyrene TPS: SBS chunks white 250
Poly(styrene-co-butadiene) TPS: SBS pellets white 1 000
Polystyrene-block-poly(ethylen-ran-butylene)- 1
TPS: SEBS powder white 2 x 250
block-polystyrene
Poly[4,4’-methylenebis(phenyl isocyanate)-alt-
TPU pellets colorless 250
1,4-butanedial/di(propylene glycol)/polycaprolactene]
Flexmark 7 Polyurethane TPU filament white 1 000
Estane 55887 NAT 055 TPU pellets transparent/translucent 25 000
SantopreneTM 8211-65 TPV pellets white/beige 25 000
Vistamax r 3000 TPO pellets transparent 25 000
Vistamax r 3588 FL TPO pellets transparent 25 000
As seen in Table 3, most of the polymers pre-selected through the EduPack analysis are
present. Their name, family as well as their form and colour are specified. Some of them can be
bought in an adapted form and colour (pellets and transparent/translucent) in order to melt them
and obtain the right visual aspect.
The selected thermoplastics (PP, PVDF, PVDC and POM) are not considered as elastomers.
However they have gone through every criterion that has been made. Therefore, even if there
chances of success are small, it is possible that one of this thermoplastic gave a good result. The
biggest problem will certainly by the poor stickiness of these materials.
SBS andd SEBS are much more interesting materials. They have excellent adhesive and
rubbery properties, which makes them a non negligible option. However, mechanical properties
can be an issue. In fact, they have a very low Young’s modulus and tensile strength. Consequently,
the risk of breaking is high and can cause damages. This situation is not wanted as the artificial
spider should resist to small shock, so they don’t have to be change many times.
1
Two Polystyrene-block-poly(ethylen-ran-butylene)-block-polystyrene with different mass average molar mass
Mw were bought. The first one has a Mw equal to 89 000 g/mol while to second one has a Mw equal to 118 000
g/mol. We will refer has SEBS89 and SEBS118 respectively
16Artificial Spider Webs
TPU (Thermoplastic Polyurethane) shows to be the most promising material for this appli-
cation. Regarding its properties: a sufficient transparency, a Young’s modulus of 0.1 GPa, which
fit perfectly with the selected value, the typical elongation of elastomers (300%-500%) and a melt-
ing temperature around 190°C, TPU seems to be the exact material that is needed for spider web
decoration.
Contrary to the previous ones, TPV is a mix between two materials: PolyPropylene PP and
Nitrile Butadiene Rubber NBR. Among the selected elastomers, TPV is maybe the less promising
because of his low elastic strength and elongation. However if it’s enough to, respectively, support
the shock and stretch the web as desired, this material can be the wanted one.
TPO is relatively close to TPU and should be considered as a believable candidate for this
application. Usually, it’s a material softer as TPU but the others properties are quite similar.
However, TPO is partly made of EPDM, which is an expansive synthetic rubber. Therefore, it
should be preferable to use TPU.
17Artificial Spider Webs
7 Discussion
Even if it’s not possible to discuss about the results obtained, the analysing method can be
approached.
7.1 Results analysis
First, the success of the experiments will be judged on the capability to reproduce a spider
web. As they have not been realised yet, it is hard to be sure that everything will work for every
material. In fact, maybe some of them will not mix with naphtha oil or will be dissolved a bit
during the cooling in the water bath. These two steps are the most critical ones.
Since the visual aspect must be taken care of cautiously, it will be an eliminating criteria. Every
material that is not satisfying visually (big yarn, translucent, etc) will be put aside.
Then, with the remaining samples, a ranking for each parameter will be done. Consequently, three
classifications are going to be done: stretchability, shapability in the water bath and stickiness.
Depending on these rankings, a global one will be done to know which material is best for a spider
web application.
Ideally, the three properties will be tested with adequate measuring devices. However, Arclight
[1] does not have such things so the ranking will be hand-made, based on the sensations for the
shapability and the stickiness and thanks to a meter for the stretchability.
Once one or possibly two materials have been selected, the variable parameters will be in-
vestigated deeper. The few measurements with variations of the naphtha oil amount and heating
temperature could be completed with other ones in order to determine the perfect process to design
spider web. These additional tests are going to be analyse in the same way as explained before.
18Artificial Spider Webs
8 Conclusion
Due to their incredible combination of properties spider webs are one of the most investigated
biomaterials and many research to reproduce them are still undergoing. One possible application
of artificial spider webs are cinematic special effects and this was the aim of the project.
The process and material selection were first to be decided in order to reach the wanted visual
properties. In fact the visual aspect is the most important one following a possible cinematic
application, but the mechanical properties are also not to be rejected.
Thus throughout a material selection of suitable polymers by their mechanical, thermal and visual
properties, a list was sorted out. Amongst these thermoplastics materials, TPU, TPO, TPV, and
TPS will be tested afterwards to see if they can be used for this purpose. As explained the testing
procedure is using a simple fat fryer the polymer need to be mixed with Naphtha, improving the
visual and solidification properties. The webs are then formed pouring out the melted mixture in
a water bath so it can solidify.
Unfortunately, due to delivery issues, the experimentation can’t be made yet. Therefore only a
expectation analysis is made including how the results will be interpretation.
From these expectations, TPU seems to be the most suitable polymer to be used for artificial
spider webs, possibly leading to stretchable, sticky and very lookalike spider webs.
19Artificial Spider Webs
9 Acknowledgement
We thank our project supervisor Christopher Hulme-Smith from the department of Material
Science and Engineering at KTH for his help and support. We thank Martin Högberg, CEO of
Arclight AB [1], for his support and the investments in the testing products. We thank Bo Norman,
sales manager of Bjorn Thorsen AB, for his advices in the choice of the polymer products.
20Artificial Spider Webs
10 References
[1] LinkedIn, Arclight AB, https://se.linkedin.com/company/Arclight
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21Artificial Spider Webs
[16] GRANTA EduPack, Formerly CES EduPack: Materials Education Support |
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[17] Chemical Retrieval on the Web, « Elastomers », https://polymerdatabase.com /Elas-
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22TRITA ITM-EX 2021:2 www.kth.se
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