WO2011067005A1

WO2011067005A1 - Protective headgear

Info

Publication number: WO2011067005A1
Application number: PCT/EP2010/064505
Authority: WO
Inventors: Thorsten Pretsch
Original assignee: Bundesanstalt für Materialforschung und -Prüfung (BAM)
Priority date: 2009-12-02
Filing date: 2010-09-29
Publication date: 2011-06-09
Also published as: DE102009056723A1

Abstract

The invention relates to an item of protective headgear, particularly for a person, said headgear comprising an outer part that faces away from the head and an inner part that faces towards the head, the inner part that faces towards the head comprising a shape memory polymer.

Description

head protection

The present invention relates to a headgear for a human, and in particular the head-facing inner part of the headgear.

All known safety and protective helmets, from the simplest safety helmet

(Hard hat, electrician's helmet, industrial helmet, forestry helmet) to special helmets in sports, such as motorcycle helmets or rugby, hockey, baseball, field hockey and American football or polo helmets, or helmets for riders, martial artists, skiers, snowboarders, cyclists , Footballers, etc. are commonly referred to as

outer shell facing away from the outer shell made of a hard resistant material, usually glass fiber reinforced plastic such as acrylonitrile-butadiene-styrene polymer (ABS), nylon, a polycarbonate or polyester with integrated glass fibers on. The task of this hard outer shell is a direct action of a

Impacting solid body on the skull of the person wearing the helmet. Furthermore, the helmet should distribute the impact force caused by the impact on a larger area and thus weaken. Furthermore, helmets typically have one

head-facing inner part on. For example, safety helmets have a system of tapes attached to the inside of the helmet of a material of limited elasticity such as leather, linen, nylon or the like. For more demanding safety and safety helmets, a shock absorbing insert, such as a lining of resilient material, such as foamed or unfoamed rubber or plastic, is provided. This can for example be made of foamed polystyrene, known under the trade name Styrofoam. In general, all the linings mentioned have the purpose of destroying as far as possible the shock forces normally occurring only for a short time as a result of implementation in deformation work and thus ultimately in heat and to distribute the remaining residual forces spatially and temporally as far as possible.

In the past, it has been shown that safety-related aspects of helmet inserts often go at the expense of wearing comfort. An increase in wearing comfort for said helmets or helmet systems would therefore be desirable. In view of the above, the present invention proposes a head guard according to claim 1. Other aspects, benefits and details of the present

Invention will become apparent from the dependent claims, the description and the accompanying drawings.

According to one embodiment, a head guard comprises a head facing away outer part and a head-facing inner part, wherein the head-facing inner part a

Shape memory polymer (FGP) has.

By using a shape memory polymer for the head facing interior of the headgear, the specific head shape of the wearer can be programmed into the FGP. In this way, the head protection is particularly well adapted to the respective wearer and provides a comfortable fit. If a deformation occurs, the FGP can be restored to its original shape by triggering the shape memory effect. Finally, in this way even traces of use, which can be caused by prolonged wearing of the head protection, be eliminated.

According to one embodiment, the headgear may be a helmet and that

head-facing inner part forms an inner lining of the helmet.

The individual head shape of the helmet wearer may be incorporated into the shape memory polymer

be programmed. Thus, through the use of FGPen a stepless

Adjustability of the insert and thus better adaptability compared to conventional solutions. In addition, an effective air exchange in the helmet is ensured.

In particular, the helmet may also be a motorcycle helmet. at

Motorcycle helmets leads usually resulting in an accident deformation of the helmet to the fact that the helmet is then no longer able to continue to perform the protective function. By using a FGP inside the helmet, deformations can be thermally induced in this area, for example. In this way, the initial state of the helmet lining can be restored, resulting in

undamaged outer shell may be worthwhile. Furthermore, wear marks can be reduced by long-term wear. By triggering the shape memory effect, the material returns to its original shape. According to another embodiment, the headgear may be a face mask and the head-facing inner part forms an inner pad of the face mask.

Sports accidents in the facial area are often associated with fractures of the nose or cheekbone. Wearing an individual sports mask can be helpful in returning to training and competitions shortly after such an injury. Similarly, a sports mask is indispensable in many sports as prophylactic protection.

Sports masks are used in the following sports: football, basketball, baseball, handball, boxing, field hockey, skiing, mountain biking, cycling, equestrian sports, martial arts, snowboarding and polo. Beyond that

Sports masks also of animals, e.g. of horses, worn in trotting or gallop racing.

An active, comprehensive protective face mask must be easy to place, portable and removable. The outside of the mask is typically formed of a hard, resistant material. For example, the outside of the mask can be made of polycarbonate. The inner pad with a FGP allows a simple

Adjustment of the mask to the head shape of the wearer and recovery from deformation by triggering the shape memory effect.

According to another embodiment, the shape memory polymer is foamed.

Foaming increases the damping effect of the FGP and reduces its density. This brings weight advantages, which in turn increase the comfort of the head protection.

Exemplary embodiments of the present invention include a shape memory polymer which is selected from the group consisting of: linear block copolymers, in particular polyurethanes and polyurethanes with ionic or mesogenic components,

Block copolymers of polyethylene terephthalate and polyethylene oxide, block copolymers of polystyrene and poly (l, 4-butadiene), ABA triblock copolymers of poly (2-methyl-2-oxazoline) (A block) and polytetrahydrofuran (B block), multiblock from

Polyurethanes with poly (e-caprolactone) switching segment, block copolymers from

Polyethylene terephthalate and polyethylene oxide, block copolymers of polystyrene and poly (l, 4- butadiene), polyurethane systems whose hard segment-forming phase

Methylendiphenyldiisocyanat (MDI) and a diol, in particular 1,4-butanediol, or a diamine and a switching segment based on an oligoether, in particular

Polytetrahydrofuran or an oligoester, in particular polyethylene adipate,

Polypropylenadipat or Polybutylenadipat, consists of materials having a hard segment-forming phase of toluene-2,4-diisocyanate, MDI, diisocyanates, in particular of MDI or hexamethylene diisocyanate in carbodiimide-modified form and from

Chain extenders, in particular ethylene glycol, bis (2-hydroxyethyl) hydroquinone or a combination of 2,2-bis (4-hydroxyphenyl) propane and ethylene oxide are constructed whose switching segment-determining blocks of oligoethers, especially polyethylene oxide,

Polypropylene oxide, polytetrahydrofuran or from a combination of 2,2-bis (4-hydroxyphenyl) propane and propylene oxide, or oligoesters, in particular

Polybutylene adipate consist of materials of polynorbornene, graft copolymers

Polyethylene / nylon-6, block copolymers with polyhedral oligomeric silsesquioxanes (POSS), including the combinations polyurethane / POS S, epoxide / POSS,

Polysiloxane / POSS, polymethyl methacrylate / POSS, silicone based FGPs, and poly (cyclooctene) e-caprolactone materials.

Other embodiments of the present invention include

A shape memory polymer selected from the group consisting of: polyvinyl chloride, polyethylene-polyvinyl acetate copolymers, covalently crosslinked copolymer systems

Stearyl acrylate and esters of methacrylic acid.

Still other embodiments of the present invention include

A shape memory polymer formed as a shape memory polymer composite, wherein embedded in the shape memory polymer matrix is at least one filler selected from the group comprising: magnetic nanoparticles, ferromagnetic particles, especially NiZn particles, iron oxide particles, magnetite particles, a nanoclay comprising silicon nitride, silicon carbide, silicon oxide, Zirconium oxide and / or aluminum oxide, oligomeric silsesquioxanes, graphite particles, carbon nanotubes, synthetic fibers, in particular carbon fibers, glass fibers or Kevlar fibers, metal particles, thermochromic materials, in particular rutile, zinc oxide, 9,9'-bixanthylidene, ΙΟ, Κ-bianthronylidene or bis-diethylammonium tetrachloro-cuprate (II), and combinations of said fillers. A headgear according to further embodiments of the present invention may comprise a shape memory polymer selected from the group consisting of: a poly (ester urethane) copolymer, a nematic liquid crystal elastomer

Photo deformation polymer.

In a headgear according to still another embodiment of the present invention, the shape memory polymer is selected from the group consisting of: a poly (ester urethane), a chemically crosslinked semi-crystalline trans polyoctenamer, an ethylene oxide-ethylene terephthalate copolymer, a poly (ether urethane ), Polynorbornene, a norbornyl-POSS hybrid copolymer, a copolymer of polyethylene terephthalate) and polyethylene glycol), a polymer of the monomer tert-butyl acrylate and the

Crosslinker Diethylene glycol diacrylate, a copolymer made from the monomers

Methyl methacrylate and butyl methacrylate and crosslinked by tetraethylene glycol dimethacrylate, a copolymer which is composed of methyl methacrylate and polyethylene glycol) dimethacrylate, a chemically crosslinked compound based on the monomers methacrylic acid, methyl methacrylate and polyethylene glycol), a copolymer of polyethylene or isotactic polypropylene and a cyclodiolefin, especially vinylcyclohexene, cyclopentadiene, 1,5-cyclooctadienes, 2,5-norbornadiene, 5-vinyl-2-norbornene, dicyclopentadiene or 5-ethylidene-2-norbornene, a cross-linked poly (vinyl chloride), a cross-linked ethylene vinyl acetate copolymer.

Further advantageous embodiments, details, aspects and features of the present invention will become apparent from the dependent claims, the description and the accompanying drawings. It shows

1 shows a protective helmet according to an embodiment of the present invention.

Fig. 2 is a face mask according to another embodiment of the present invention.

Fig. 3 is a 3-D result of a cyclic thermo-mechanical measurement of a tensile bar of poly (ester urethane) after stretching below the

Transformation temperature. 4 shows a 3-D result log of a cyclic thermo-mechanical measurement of a tensile bar made of poly (ester urethane) after stretching above the

Transformation temperature.

Fig. 1 shows a protective helmet 10 according to an embodiment of the present invention. The protective helmet 10 has a head-facing outer part 12, which is formed of a hard, resistant material. For example, this can be a

glass fiber reinforced plastic such as acrylonitrile butadiene styrene polymer (ABS), nylon, a polycarbonate or polyester with embedded glass fibers. In addition, the helmet 10 has a head-facing inner part 14, which in the example shown, a plurality of bands 16, 18, 20, which are connected to a headband 22. The width of the headband 22 is adjustable via an adjusting means 24, for example a screw mechanism. The bands 16, 18, 20 and the headband 22 of the inner part 14 comprise a shape memory polymer and in particular may be formed entirely from such an FGP or a foamed FGP.

Fig. 2 shows a face mask 50 according to another embodiment of the present invention. The face mask 50 has an outer facing away from the head 52, which is formed of a hard, resistant material. For example, for this purpose, a glass fiber reinforced plastic such as acrylonitrile-butadiene-styrene polymer (ABS), nylon, a polycarbonate or polyester with incorporated glass fibers can be used. In addition, the face mask has a head-facing inner part, which in the present embodiment comprises the inner pads 54 and 56. According to other embodiments, the entire inner surface of the outer part 52 may be covered with the inner liner. The face mask 50 further comprises a band 58 by means of which the mask can be attached to the head of the wearer. In accordance with embodiments of the present invention, inner liner 54, 56 comprises a shape memory polymer.

In particular, the inner liner may be formed entirely of such a FGP or a foamed FGP.

As shape memory polymers, plastics are generally referred to which, after a transformation, apparently "remember" their former external form and thus have a shape memory

Exceeding a so-called switching temperature triggered. Among these thermosensitive Generally speaking, FGPen can be distinguished between FGPen, for which the switching temperature corresponds to a glass transition (Ttra _ns = T _g ), and FGPen, for which the switching temperature corresponds to the melting temperature of crystalline soft segments (Ttrans = T _m ). In the latter case, the FGPs have two components, wherein a first component is an elastic polymer (hard segment) and the second component is a hardening wax (soft segment). If the FGP is deformed, the elastic polymer is "arrested" by the hardened wax in its deformed form, and if the FGP is subsequently heated, the wax softens and can no longer counteract a restoring spring force of the elastic component Shape.

The shape memory effect will now be exemplified by means of poly (ester urethane). For this purpose, in FIGS. 3 and 4 each show a 3-D result log of a cyclic thermomechanical measurement of a tensile bar made of poly (ester urethane) in a stress-strain-temperature diagram. In Fig. 3, the drawing of the tensile bar at room temperature, ie below Ttrans, while in Fig. 4, the stretching at 60 ° C, ie above

took place. In both cases it is clearly recognizable how the staff always follows the same trajectory in the state space, ie how the staff always returns from a deformed form to its original form.

Furthermore, the poly (ester urethane) shape memory polymer can be used both with and without a stabilizer. In one embodiment, the stabilizer may be a carbodiimide. Typically, the shape memory polymer has a stabilizer content of between 0.1% and 3% by weight, based on the ester content. A comparison of the mechanical characteristics for non-stabilized and stabilized poly (ester urethane) shape memory polymer is given in Table I.

Table I Furthermore, a comparison of the thermo-mechanical characteristics of non-stabilized and stabilized poly (ester urethane) shape memory polymer was performed. Were

shown.

Table II

As a result, the non-stabilized poly (ester urethane) shape memory polymer and the stabilized poly (ester urethane) shape memory polymer have substantially similar thermo-mechanical properties.

According to a further embodiment, the poly (ester urethane) may have between 50% by weight and 90% by weight of switching segments. For example, the poly (ester urethane) may comprise switching segment blocks of a poly (e-caprolactone) diol. According to a development, the poly (e-caprolactone) diol has an average molecular weight between 1500 and 8500.

In this way, the switching temperature for the shape memory effect depending on

Weight fraction of the switching segment and molecular weight of the poly (8-caprolactone) diols can be varied. The crystallization temperature can also be adjusted in this way. In addition, the hardness at room temperature can be increased by increasing

Soft segment length and growing soft segment content can be increased. This is due to an increased soft-segment crystallinity. At elevated temperature, the hardness decreases with increasing soft segment content and increases with increasing soft segment length. Furthermore, as the soft segment content increases, the tensile strength decreases and the elongation at break increases. In this case, the tensile strength with soft segments of poly (8- caprolactone) diols are set at between about 30 and 60 MPa, resulting in elongation at break values between 800 and 1150%. Decisive for the right material selection are the strength and rigidity of the FGP as well as its deformability and fixability. For poly (ester urethanes) many of these mechanical parameters can be adjusted via synthesis. This relates to the crystallinity of the soft segments and the associated mechanical parameters, in particular the material hardness and the extensibility, as well as the thermo-mechanical properties, in particular the Dehungsfixierbarkeit, the

Stretch recoverability and the transformation temperature, above which the material can be deformed.

According to another embodiment, the poly (ester urethane) has between 10% and 55% by weight of hard segments.

Although the shape fixability decreases with increasing hard segment content, a small proportion of hard segment leads to poor extensibility. Below a lower limit of about 10 weight percent hard segment, the hard segment domains are typically no longer sufficiently strong and no longer perform their function as physical crosslinkers.

A head guard according to one embodiment may be a thermoplastic

Shape memory polymer, in particular from the group of linear block copolymers,

in particular polyurethanes and polyurethanes with ionic or mesogenic components, block copolymers of polyethylene terephthalate and polyethylene oxide, block copolymers of polystyrene and poly (1,4-butadiene), ABA triblock copolymers of poly (2-methyl-2-oxazoline) (A block) and polytetrahydrofuran (B block), multiblock copolymers

Polyurethanes with poly (8-caprolactone) switching segment, block copolymers from

Polyethylene terephthalate and polyethylene oxide, block copolymers of polystyrene and poly (l, 4-butadiene), polyurethane systems, the hard segment-forming phase of

Polytetrahydrofuran or an oligoester, in particular polyethylene adipate,

Polypropylenadipat or Polybutylenadipat, consists of materials having a hard segment-forming phase of toluene-2,4-diisocyanate, MDI, diisocyanates, in particular from MDI or hexamethylene diisocyanate in carbodiimide-modified form and from Chain extenders, in particular ethylene glycol, bis (2-hydroxyethyl) hydroquinone or a combination of 2,2-bis (4-hydroxyphenyl) propane and ethylene oxide are constructed whose switching segment-determining blocks of oligoethers, in particular polyethylene oxide, polypropylene oxide, polytetrahydrofuran or from a combination from 2,2-bis (4-hydroxyphenyl) propane and propylene oxide, or from oligoesters, in particular

Polybutylene adipate consist of materials of polynorbornene, graft copolymers

Polysiloxane / POSS, polymethyl methacrylate / POSS, silicone-based FGPs, and poly (cyclooctene) materials.

According to other embodiments, the FGP may be an elastomeric FGP, in particular from the group consisting of polyvinyl chloride, polyethylene-polyvinyl acetate copolymers, covalently crosslinked copolymer systems of stearyl acrylate and esters of methacrylic acid.

According to further embodiments, the FGP may be a nematic

Liquid crystal elastomer, or photodeformation polymer. Such materials may have two-dimensional memory and two-way effect.

According to still other embodiments of the present invention, the FGP is formed as a shape memory polymer composite. In this connection, it should be noted that the terms shape memory polymer and shape memory polymer composite are used interchangeably. In other words, instead of an FGP, a correspondingly suitable FGP composite or vice versa can also be used. FGP composites are materials in which one or more fillers are embedded in the FGP matrix. Examples of suitable fillers are magnetic nanoparticles, ferromagnetic particles, in particular NiZn particles, iron oxide particles and magnetite particles. Likewise, so-called nanoclays can be used as fillers. The nanoclays can be based on silicon nitride, silicon carbide,

Silicon oxide, zirconium oxide and / or alumina may be formed. Other possible fillers are oligomeric silsesquioxanes, graphite particles, carbon nanotubes, synthetic fibers, in particular carbon fibers, glass fibers or Kevlar fibers, but also

Metal particles, thermochromic materials, in particular rutile, zinc oxide, 9,9'-bixanthylidene, ΙΟ, ΙΟ'-bianthronylidene or bis-diethylammonium tetrachloro-cuprate (II), and combinations of said fillers.

Of course, combinations of such fillers can be used. The fillers are suitable for adjusting the mechanical, electrical, magnetic and / or optical properties of an FGP and adapting it to a particular application.

In head protectors according to the embodiments of the present invention, thermo-sensitive, UV or magneto-sensitive and electroactive FGPs can be used. Optically controllable shape memory polymers are e.g. Butyl acrylates, which crosslink at their side chains via cinnamic acid groups under UV light of a certain wavelength and solve the bond when irradiated with a different wavelength again. Magnetically controllable shape memory polymers can, for. By incorporation of finely divided magnetic nanoparticles of e.g. Iron oxide can be obtained in the plastic. Such materials are then able to convert the energy of a magnetic field into heat. About the proportion of nanoparticles and the strength of the magnetic field, a desired temperature in the polymer can be adjusted specifically. As electroactive polymers (EAP), e.g.

Shape memory polymer composites are used with carbon nanotubes.

Other examples of thermoplastic elastomers are multiblock copolymers. Typical multiblock copolymers are composed of the blocks (macrodiols) consisting of ω-diol polymers of poly (e-caprolactone) (PCL), polyethylene glycol (PEG),

Poly (pentadecalactone), poly (ethylene oxide), poly (propylene oxide), poly (propylene glycol), poly (tetrahydrofuran), poly (dioxanone), poly (lactide), poly (glycolide) and poly (lactide-ran- glycolid) or from , ω-Diol copolymers of the monomers on which the above-mentioned compounds are based, in a molecular weight range M _n of 250 to 500 000 g / mol. Two different macrodiols are made using a suitable bifunctional

Coupling reagent (in particular an aliphatic or aromatic diisocyanate or diacid chloride or phosgene) to a thermoplastic elastomer having molecular weights M _n in the range of 500 to 50 000 000 g / mol linked. In a phase-segregated polymer, a phase with at least one thermal transition (glass transition or melt transition) can be assigned to each of the blocks of the abovementioned polymer independently of the other block. Also applicable are multiblock copolymers of macrodiols based on pentadecalactone (PDL) and ε-caprolactone (PCL) and a diisocyanate. The switching temperature - here a melting temperature - can be adjusted over the block length of the PCL in the range between approx. 30 and 55 ° C. The physical network points for fixing the permanent mold are formed by a second crystalline phase having a melting point in the range of 87-95 ° C. Blends of multiblock copolymers are also suitable. Due to the mixing ratio, the transition temperatures can be adjusted specifically.

For the production of the inner part of the head protection and polymer networks can be used. Suitable polymer networks are characterized by covalent network points and at least one switching segment with at least one transition temperature. The covalent mesh points determine the permanent shape of the surface profile. To produce a covalent polymer network, one of the macrodiols described in the above section is crosslinked by means of a multifunctional coupling reagent. This coupling reagent may be an at least trifunctional, low molecular weight compound or a multifunctional polymer. In the case of the polymer may be a

Star polymer with at least three arms, a graft polymer with at least two

Side chains, a hyperbranched polymer or act on a dendritic structure. Both in the case of the low molecular weight and the polymeric compounds, the end groups should be capable of reacting with the diols. In particular, isocyanate groups can be used for this purpose (polyurethane networks). In particular, amorphous polyurethane networks of triols and / or tetrols and diisocyanate can be used. Star-shaped prepolymers such as 01igo [(rac-lactate) -co-glycolate] triol or -tetrol are prepared by the ring-opening copolymerization of rac-dilactide and diglycolide in the melt of the monomers with hydroxy-functional initiators with the addition of the catalyst dibutyltin (IV) oxide ( DBTO). As initiators of the ring-opening polymerization ethylene glycol, l, l, l-tris (hydroxy-methyl) ethane or pentaerythritol are used.

Analogously, 01igo (lactate-co-hydroxycaproate) tetrols and

01igo (lactate hydroxyethoxyacetate) tetrols as well as [01igo (propylene glycol) block oligo (raclactate) -co-glycolate)] triols. Such networks can be easily prepared by reacting the prepolymers with diisocyanate, e.g. B. a mixture of isomers of 2,2,4- and 2,4,4-trimethylhexane-l, 6-diisocyanate (TMDI), in solution, e.g. in dichloromethane, and

subsequent drying can be obtained. Furthermore, the macrodiols described in the above section can be functionalized to corresponding cc, C6 divinyl compounds which can be thermally or photochemically crosslinked. The functionalization preferably allows covalent attachment of the macromonomers by reactions which do not give by-products. Preferably, this functionalization is provided by ethylenically unsaturated moieties, more preferably by acrylate groups and methacrylate groups, the latter being especially preferred. In this case, in particular, the reaction to cc, Cö macrodimethacrylates, or macrodiacrylates can be carried out by the reaction with the corresponding acid chlorides in the presence of a suitable base. The networks are obtained by crosslinking the end-group functionalized macromonomers. This crosslinking can be achieved by irradiating the melt, comprising the end group-functionalized macromonomer component and optionally a low molecular weight comonomer, as explained below. Suitable process conditions for this are the irradiation of the mixture in melt, preferably at temperatures in the range of 40 to 100 ° C, with light having a wavelength of preferably 308 nm. Alternatively, a heat crosslinking is possible if a corresponding initiator system is used.

When the above-described macromonomers are crosslinked, networks with a uniform structure are formed when only one type of macromonomer is used. When two types of monomers are used, AB type networks are obtained. Such AB type networks can also be obtained if the functionalized

Macromonomers are copolymerized with suitable low molecular weight or oligomeric compounds. Are the macromonomers with acrylate groups or

Functionalized methacrylate groups, so are suitable compounds which can be copolymerized low molecular weight acrylates, methacrylates, diacrylates or dimethacrylates. Preferred compounds of this type are acrylates, such as butyl acrylate or hexyl acrylate, and methacrylates, such as methyl methacrylate and hydroxyethyl methacrylate. These compounds, which may be copolymerized with the macromonomers, may be present in an amount of from 5 to 70 parts by weight, based on the network of macromonomer and the low molecular weight compound, in particular in an amount of from 15 to 60 parts by weight. The incorporation of varying amounts of the low molecular weight compound by addition

appropriate amounts of compound to be crosslinked mixture. The installation of the low molecular weight compound in the network is in an amount corresponding to the amount contained in the cross-linking mixture.

By varying the molecular weight of the macrodiols can be networks with

different crosslinking densities (or segment lengths) and mechanical

Achieve properties. The covalently to be crosslinked macromonomers have

typically a number average molecular weight determined by GPC analysis of 2,000 to 30,000 g / mol, preferably from 5,000 to 20,000 g / mol, and more preferably from 7,500 to 15,000 g / mol. The covalently-crosslinked macromonomers typically have a methacrylate group at both ends of the macromonomer chain. Such

Functionalization allows the crosslinking of the macromonomers by simple

Photoinitiation (irradiation).

The macromonomers are typically polyester macromonomers, in particular

Polyester macromonomers based on ε-caprolactone. Other possible

Polyester macromonomers are based on lactide units, glycolide units, p-dioxanone units and mixtures thereof and mixtures with ε-caprolactone units, with polyester macromonomers having caprolactone units being particularly typical.

Typical polyester macromonomers are also poly (caprolactone-co-glycolide) and poly (caprolactone-co-lactide). About the ratio of comonomers, the transition temperature can be adjusted.

The macromonomers used may in particular be polyesters comprising the crosslinkable end groups. A typical polyester to be used is a polyester based on ε-caprolactone or pentadecalactone, for which the above-mentioned molecular weight data apply. The preparation of such a polyester macromonomer, functionalized at the ends, preferably with methacrylate groups, can be prepared by simple syntheses known to those skilled in the art. These networks without

Considering the other essential polymeric component of the present invention show semicrystalline properties and have a melting point of

Polyester component (determinable by DSC measurements), which is dependent on the nature of the polyester component used and is therefore also controllable. As is known, this temperature (T _m ) for segments based on caprolactone units is between 30 and 60 ° C., depending on the molecular weight of the macro monomer. A network with a melting temperature as the switching temperature is based on the macromonomer poly (caprolactone-co-glycolide) dimethacrylate. The macromonomer may be reacted as such or copolymerized with n-butyl acrylate to the AB network. The permanent shape is determined by covalent mesh points. The network is characterized by a crystalline phase whose melting temperature is determined by the

Comonomer ratio of caprolactone to glycolide can be adjusted in a targeted manner, n-butyl acrylate as a comonomer can e.g. be used to optimize the mechanical properties of the tapes. Another network with a glass transition temperature as

Switching temperature is obtained from an ABA triblock dimethacrylate as macromonomer with a middle block B of polypropylene oxide and end blocks A of poly (rac-lactide). The amorphous networks have a very wide switching temperature range.

To fabricate headguards with two shapes in mind, networks with two transition temperatures are suitable, such as interpenetrating networks (IPNs). The covalent network is based on poly (caprolactone) dimethacrylate as macromonomer; the interpenetrating component is a multiblock copolymer of macrodiols based on pentadecalactone (PDL) and ε-caprolactone (PCL) and a diisocyanate. The permanent shape of the material is determined by the covalent network points. The two

Transition temperatures - melting temperatures of the crystalline phases - can be used as switching temperatures for each temporary shape. The lower switching temperature Ttransi can be set over the block length of the PCL in the range between approx. 30 and 55 ° C. The upper switching temperature

lies in the range of 87-95 ° C.

Furthermore, photosensitive networks can be used to make the headgear. Suitable photosensitive networks are amorphous and feature covalent network points that determine the permanent shape. A further feature is a photoreactive component or a unit that can be reversibly switched by light, which determines the temporary shape. In the case of the photosensitive polymers, a suitable network is used which photosensitve along the amorphous chain segments

Contains substituents. Upon UV irradiation, these groups are able to form covalent bonds with each other. Deforming the material and irradiating it with light of a suitable wavelength λ _1; In addition, the original network is cross-linked.

Due to the networking one reaches a temporary fixation of the material in deformed state (programming). Since the photo-crosslinking is reversible, can be solved by re-irradiation with light of a different wavelength λ _2, the networking again and thus retrieve the original shape of the material again. Such a

Photomechanical cycle can be repeated as often as desired. The basis of the photosensitive materials is a wide-meshed polymer network which, as stated above, is transparent with respect to the radiation intended to induce the change in shape, ie preferably forms a UV-transparent matrix. Typical are networks based on low molecular weight acrylates and methacrylates that can be radically polymerized, in particular C ₁ -C ₆ (meth) acrylates and hydroxy derivatives, wherein hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, poly (ethylene glycol) methacrylate and n-butyl acrylate and in particular n Butyl acrylate and hydroxyethyl methacrylate can be used.

As a comonomer for the preparation of the polymeric networks, a component is used which is responsible for the crosslinking of the segments. The chemical nature of this

Of course, component depends on the nature of the monomers. For the networks based on the acrylate monomers described above, suitable crosslinkers are bifunctional acrylate compounds which are suitably reactive with the starting materials for the chain segments so that they can be reacted together. Such crosslinkers include short, bifunctional crosslinkers such as ethylene diacrylate, low molecular weight bi- or

polyfunctional crosslinkers, oligomeric, linear diacrylate crosslinkers, such as

Poly (oxyethylene) diacrylates or poly (oxypropylene) diacrylates, and branched oligomers or acrylate terminated polymers. As a further component, the network comprises a photoreactive component (group), which is responsible for triggering the specifically controllable

Is responsible for change of form. This photoreactive group is a moiety capable of reversible reaction (with a second photoreactive group) by excitation with suitable light radiation, typically UV radiation, which results in the generation or dissolution of covalent bonds. Typical photoreactive groups are those capable of reversible photodimerization. Typically, various cinnamic acid esters serve as photoreactive components in the photosensitive networks

(Cinnamate, CA) and cinnamyl acyl esters (cinnamyl acylates, CAA).

Cinnamic acid and its derivatives dimerize under UV light at about 300 nm to form a cyclobutane. The dimers can be split again when using UV light smaller wavelength of about 240 nm is irradiated. The absorption maxima can be shifted by substituents on the phenyl ring, but always remain in the UV range.

Other photodimerizable derivatives are 1,3-diphenyl-2-propene-1-one (chalcone), cinnamylacylic acid, 4-methylcoumarin and various ortho-substituted cinnamic acids, cinammyloxysilanes (silyl ethers of cinnamyl alcohol).

The photodimerization of cinnamic acid and similar derivatives is a [2 + 2] cycloaddition of the double bonds to a cyclobutane derivative. Both the E and Z isomers are capable of undergoing this reaction. Under irradiation, the E / Z isomerization proceeds in competition with the cycloaddition. In the crystalline state, however, the E / Z isomerization is hindered. Due to the different arrangement possibilities of the isomers to each other theoretically 11 different stereoisomere products (Truxillesäuren, Truxinsäuren) are possible. The required for the reaction distance of the double bonds of two cinnamic acid groups is about 4 A.

In another embodiment, the shape memory polymer is a chemically cross-linked semi-crystalline trans polyoctenamer. With this FGP can be

= T _m via the addition of dicumyl peroxide set. Typical values are Ttra _ns = T _m = 58 ° C and T _trans = T _c = 24 ° C.

In another embodiment, the shape memory polymer is a poly (ester urethane) prepared from 4,4'-diphenylmethane diisocyanate (MDI), poly (butylene adipate) glycol (PBAG) and trimethylol propane (TMP). For this, values of Ttrans> 40 ° C can be set.

In another embodiment, the shape memory polymer is a

cross-linked poly (ester urethane) consisting of polycaprolactone diol (PCL), 1,4-butanediol (BD), dimethylol propionic acid (DMPA), triethylamine and 4,4'-diphenylmethane diisocyanate (MDI), to which an excess of MDI or glycerol given is formed. Values of

= T _{m can be set} in the range of 47 ° C to 56 ° C.

In another embodiment, the shape memory polymer is an ethylene oxide-ethylene terephthalate copolymer. The switching temperatures can be reached via the synthesis between

= Set T _m in the range of 52 ° C to 62 ° C and = T _c in the range of 20 ° C to 31 ° C.

In another embodiment, the shape memory polymer is a poly (ether urethane), for example, composed of 4,4'-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BD), and poly (tetramethyl oxide) glycol (PTMO). The switching temperature Ttrans = T _g is about 54 ° C.

In another embodiment, the shape memory polymer is a

Polynorbornen with a switching temperature Ttrans = T _g = 40 ° C.

In another embodiment, the shape memory polymer is a norbornyl-POSS hybrid copolymer having a switching temperature

= T _g in the range of 47 ° C to 73 ° C.

In another embodiment, the shape memory polymer is a copolymer of polyethylene terephthalate (PET) and polyethylene glycol (PEG), wherein the

Switching temperature Ttrans = T _g > 34 ° C is.

According to another embodiment, the shape memory polymer is a polymer comprising the monomer tert-butyl acrylate (TBA) and the crosslinker diethylene glycol diacrylate (DEGDA), wherein the shape memory polymer typically has a switching temperature of about Ttrans = = comprising 65 ° C T _g.

In another embodiment, the shape memory polymer is a copolymer composed of the monomers methyl methacrylate (MMA) and butyl methacrylate (BMA) and cross-linked by tetraethylene glycol dimethacrylate (TEGDMA). The switching temperature depends on this

= T _g ) from the monomer ratio and can typically be set between 27 ° C and 66 ° C.

In another embodiment, the shape memory polymer is a copolymer composed of methyl methacrylate (MMA) and polyethylene glycol dimethacrylate (PEGDMA). The switching temperature = T _{g can} typically be set between 56 ° C and 92 ° C. In another embodiment, the shape memory polymer is a chemically crosslinked compound made from the monomers methacrylic acid (MAA), methyl methacrylate (MMA) and polyethylene glycol (PEG). Here, for example, the

Switching temperature in the range of

= T _g = 75 ° C.

In another embodiment, the shape memory polymer is a copolymer of polyethylene or isotactic polypropylene and cyclodiolefins such as vinylcyclohexene, cyclopentadiene, 1,5-cyclooctadiene, 2,5-norbornadiene, 5-vinyl-2-norbornene (VNB), dicyclopentadiene (DCPD) or 5 -Ethylidene-2-norbornene (ENB), for which the switching temperature trans = T _{g can be set} in a wide temperature range.

In another embodiment, the shape memory polymer is a

cross-linked poly (vinyl chloride) (PVC), although the switching temperature can be in the range of Ttrans = T _g = 83 ° C.

The present invention has been explained with reference to exemplary embodiments. These embodiments should by no means be understood as limiting the present invention. In particular, individual characteristics of the various

Embodiments are adopted in other embodiments or different embodiments are combined with each other, as long as the combined

Do not mutually exclude features for technical reasons.

Claims

A head guard comprising an outer facing away from the head and a head facing inner part, the head facing inner part comprising a shape memory polymer.

2. The headgear of claim 1, wherein the headgear is a helmet and the

head-facing inner part is an inner lining of the helmet.

3. The headgear of claim 1, wherein the headgear is a face mask and the head-facing inner part is an inner pad of the face mask.

4. Head protection according to one of the preceding claims, wherein the

Shape memory polymer is foamed.

The headgear of any one of claims 1 to 4, wherein the shape memory polymer is selected from the group consisting of: linear block copolymers, especially polyurethanes and polyurethanes with ionic or mesogenic components, block copolymers of polyethylene terephthalate and polyethylene oxide, block copolymers of polystyrene and poly (1,4 -butadiene), ABA triblock copolymers of poly (2-methyl-2-oxazoline) (A block) and polytetrahydrofuran (B block),

Multiblock copolymers of polyurethanes with poly (e-caprolactone) switching segment, block copolymers of polyethylene terephthalate and polyethylene oxide, block copolymers of polystyrene and poly (l, 4-butadiene), polyurethane systems whose hard segment-forming phase of methylene diphenyl diisocyanate (MDI) and a diol, in particular 1.4 Butanediol, or a diamine and a switching segment based on an oligoether, in particular polytetrahydrofuran or an oligoester, in particular polyethylene adipate, polypropylene adipate or polybutylene adipate, comprises materials having a hard segment-forming phase of toluene-2,4-diisocyanate, MDI,

Diisocyanates, in particular of MDI or hexamethylene diisocyanate in

Carbodiimide-modified form and from chain extenders, in particular

Ethylene glycol, bis (2-hydroxyethyl) hydroquinone or a combination of 2,2-bis (4-hydroxyphenyl) propane and ethylene oxide, whose switching segment-determining blocks of oligoethers, in particular polyethylene oxide,

Polypropylene oxide, polytetrahydrofuran or a combination of 2,2-bis (4- hydroxyphenyl) propane and propylene oxide, or from oligoesters, in particular

Polybutylene adipate, materials of polynorbornene, graft copolymers of polyethylene / nylon-6, block copolymers with polyhedral oligomers

Silsesquioxanes (POSS), including the combinations polyurethane / POS S, epoxide / POSS, polysiloxane / POSS, polymethyl methacrylate / POSS, silicone-based FGPs, and poly (cyclooctene) -e-caprolactone materials.

The headgear of any one of claims 1 to 4, wherein the shape memory polymer is selected from the group consisting of: polyvinyl chloride, polyethylene-polyvinyl acetate copolymers, covalently cross-linked copolymer systems of stearyl acrylate, and esters of methacrylic acid.

7. Head protection according to one of claims 1 to 4, wherein the shape memory polymer is formed as a shape memory polymer composite, wherein in the

Embedded in the shape memory polymer matrix is at least one filling material selected from the group comprising: magnetic nanoparticles,

ferromagnetic particles, in particular NiZn particles, iron oxide particles,

Magnetite particles, a nanoclay comprising silicon nitride, silicon carbide,

Silica, zirconia and / or alumina, oligomeric silsesquioxanes, graphite particles, carbon nanotubes, synthetic fibers, in particular

Carbon fibers, glass fibers or Kevlar fibers, metal particles, thermochromic materials, in particular rutile, zinc oxide, 9,9 '-Bixanthyliden, 10, 10' -Bianthronyliden or bis-diethylammonium tetrachloro-cuprate (II), and combinations of said fillers.

The headgear of any of claims 1 to 4, wherein the shape memory polymer is selected from the group consisting of: a poly (ester urethane), a chemically crosslinked semi-crystalline trans polyoctenamer, an ethylene oxide-ethylene terephthalate copolymer, a poly (ether urethane), polynorbornene, a

Norbornyl-POSS hybrid copolymer, a copolymer of polyethylene terephthalate) and polyethylene glycol), a polymer of the monomer tert-butyl acrylate and the cross-linker diethylene glycol diacrylate, a copolymer composed of the monomers methyl methacrylate and butyl methacrylate and cross-linked by tetraethylene glycol dimethacrylate is a copolymer made of methyl methacrylate and Polyethylene glycol) dimethacrylate is built, a chemically cross-linked

Compound based on the monomers methacrylic acid, methyl methacrylate and polyethylene glycol), a copolymer of polyethylene or isotactic polypropylene and a cyclodiolefin, in particular vinylcyclohexene, cyclopentadiene, 1,5-cyclooctadienes, 2,5-norbornadiene, 5-vinyl-2-norbornene, Dicyclopentadiene or 5-ethylidene-2-norbornene, a cross-linked poly (vinyl chloride), a cross-linked ethylene-vinyl acetate copolymer.

The headgear of any one of claims 1 to 4, wherein the shape memory polymer is poly (ester urethane) based and comprises a stabilizer, especially a carbodiimide.

10. The headgear of claim 9, wherein the shape memory polymer has between 0.1% by weight and 3% by weight, based on the ester portion, stabilizer.