CN107529848A - Personalized shoes and its manufacture - Google Patents

Abstract

The present invention discloses a personalizable moldable shoe, such as a shoe or shoe insert, wherein said shoe or shoe insert, in use, extends across the entire sole of the foot and is made of a stimulus responsive shape memory material, preferably For heat-responsive shape memory materials such as ethylene vinyl acetate (EVA), polyurethane (PU) or thermoplastic polyurethane (TPU). The invention also proposes a method of manufacturing said shoe, said method comprising heating said layer to a predetermined temperature; deforming said layer; and manipulating said layer using at least one fastener to form said A shoe, wherein said deformation of said layer is performed by placing a foot structure on said layer.

Description

Personalized shoes and their manufacture

technical field

The present invention relates broadly to the design and function of shoes and the particular materials used to make them.

Background technique

Consumers are demanding more comfort and functionality from their shoes, making these characteristics an important consideration in shoe design and evaluation. Both are the result of a complex interaction between the properties of the human body (particularly the leg and more specifically the foot) and the different elements of the shoe.

When it comes to comfort, fit is the main deciding factor when it comes to buying shoes. A misfit between the foot and the shoe impairs foot function and may result in excessive pressure from a tight fitting shoe or unnecessary friction from a loose fitting shoe. For example, Crochet, an American shoe company is providing casual shoes with soft, comfortable, lightweight and odor-resistant qualities to all over the world. However, this fit is limited to the contact interface between the bottom of the foot (or sole) and the top of the sole.

Another custom-fit shoe called the Vibram five-finger shoe also provides a great fit for the user. This is partly because the material of these shoes is very elastic and elastically deformable to fit any shape (the elastic fits as a sock). However, some users do experience discomfort, as the elastic material can often put undue pressure on the foot. Additionally, the upper is often so thin that it does not provide adequate protection against foot injuries.

Since every consumer has a unique foot shape/structure and has a personal preference for shoes, it is not always easy to find a pair of shoes on the market that will comfortably fit an individual foot, especially those requiring foot orthotics It's not always easy for consumers.

Therefore, the personalization of shoes is an ever-increasing demand. Currently, there are several ways to achieve this, such as additive manufacturing and using certain polymer materials inside the boot to make the sole partially adjustable. However, these methods still have many disadvantages.

For example, prior art memory foam-based insoles that use slow recovery polymer foam (which is as soft as a resilient sponge) do not provide adequate mechanical support. For example, such memory foams are characterized by low stiffness and rigidity. Additionally, while it is possible to 3D print custom shoes for a better fit, this requires a tedious foot scanning process and an even more expensive print manufacturing process.

There is a need to provide the wearer with total foot comfort, functionality, and protection on an individual or personalized basis, while maintaining a cost-effective manufacturing process. The present invention seeks to improve upon currently existing personalized footwear.

Contents of the invention

The present invention is based on the discovery that the functionality of footwear, especially rigidity and flexibility (related to 3D contours), can be greatly improved by using certain shape memory materials (SMMs), which are characterized by a shape memory effect (SME), which is personal preference.

Thus, in one aspect, the present invention provides a moldable shoe or shoe insert which, in use, extends across the entire sole of the foot and which is fabricated from a stimulus responsive shape memory material.

In one embodiment, the stimulus responsive shape memory material is a thermally responsive shape memory material.

In one embodiment, the SMM is a shape memory polymer (SMP). The inventors have discovered that the use of SMPs in shoe fittings is reproducible and immediate; enables return to original shape if desired; provides a customizable combination of rigidity and flexibility; distributes localized foot pressure as well as manufacturing costs low.

In another embodiment, the thermoresponsive shape memory polymer retains two shapes.

In one embodiment, and during use, the moldable shoe or shoe insert is initially heated to between about 45° and at or below about 80° C, wherein the user then inserts his/her foot into the shoe or The shoe or shoe insert is molded around the contours of the user's foot. Moldable shoes or shoe inserts can be heated to elevated temperatures, such as about 80°C, but will typically be worn at temperatures of about 60°C or lower unless socks or liners are worn on bare feet.

The term "shoe" or "shoe insert" as used herein refers to the product which is the subject of the present invention, which extends over the entire sole of the foot and which may comprise a complete shoe, with or without any additional material, Examples include hardening non-moldable polymer sole materials. Thus, in certain embodiments, the present invention provides the advantage of a complete footwear product that does not require any additional manufacturing steps, such as external material stitching or external sole adhesion. As an alternative, the term also includes shoe inserts, which can also extend the entire sole of the foot, and can also be included, for example, in prefabricated shoe shapes, such as hardened outer shoe shapes (for example, for construction workers) or for ski boots. Personalized shoe inserts.

In some embodiments, "shoe" or "shoe insert" may also mean: the product which is the subject of the invention, which encloses the entire foot and which may also contain Complete footwear such as hardened non-moldable polymer sole materials. Accordingly, it should be understood that the phrase "entire sole" includes the forefoot, midfoot and rear heel. It should also be understood that "whole foot" includes the forefoot, midfoot and heel. In order to provide the rigidity and flexibility required for the user's comfort, the present invention contemplates that the surface covering of the shoe or shoe insert extends at least to cover the beginning of the heel (or ankle joint), which may or may not cover the actual ankle. joint. This is then compared to known shoe or shoe insert products which, for example, only cover the sole of the foot or partially cover the rear foot and the forefoot, but leave all or part of the upper midfoot exposed and/or unsupported.

A suitable combination of rigidity and flexibility can be obtained by varying the composition of the SMM, the processing method/parameters and/or the porosity following a number of standard polymer/polymer foam synthesis/processing methods. In one embodiment, the SMM is an SMP selected from ethylene vinyl acetate (EVA), polyurethane (PU) or thermoplastic polyurethane (TPU), or a combination of the above.

Based on the principle of the shape memory effect (SME) which is the cornerstone of the present invention, shape memory polymers (SMPs), including their composites/hybrids and constructed as solids or foams, include a number of transition temperatures from about 45°C to about 80°C or below (glass transition or melting/crystallization) polymeric materials and their composites/may be applied in this application, such as EVA or PU foam, PU, TPU or PU/TPU blends, etc. However, it should be understood that when the moldable shoe or shoe insert is initially heated up to about 80°C (and above about 45°C), the temperature of the surface when the bare foot is inserted will be at or below about 60°C, which is is the temperature that is comfortable for the end user.

Description of drawings

Figure 1 - Description of the first embodiment. (1) human foot; (2) shape memory polymer material; (3) ordinary shoes.

Figure 2 - Description of the second embodiment. (1) human foot; (2) shape memory polymer material; (3) ordinary shoes.

Figure 3 - Description of the third embodiment. (1) Human foot; (2) Shape memory polymer material.

Figure 4 - Description of the fourth embodiment, (1) human foot; (2) shape memory polymer material; (4) outer sole.

Figure 5 - Basic concept (I) of a comfortable fit shoe according to one embodiment and proof of concept (II) of this embodiment.

Fig. 6 - Cross-section (a) of EVA foam sheet and enlarged view under SEM (b).

Figure 7 - DSC curve of EVA foam. Inset: Magnified view of the glass transition range upon heating.

Figure 8 - Dimensions (unit: mm) of the uniaxial tensile test specimens.

Figure 9 - Illustration of the complete SME cycle.

Figure 10 - Typical stress-strain relationship for the case of uniaxial stretching to 30% of the maximum strain at three different temperatures, followed by cooling to room temperature and then unloading.

Figure 11 - Typical stress-strain relationship for the case of uniaxial stretching to 80% of the maximum strain at three different temperatures, followed by cooling to room temperature and then unloading.

Figure 12 - Typical stress-strain relationship of samples with/without pre-stretching under cyclic stretching at room temperature.

Figure 13 - Stress-strain relationship for uniaxial compression to 30% of maximum strain at three different temperatures, followed by cooling to room temperature and then unloading.

Figure 14 - Stress-strain relationship for uniaxial compression to 80% of maximum strain at three different temperatures, followed by cooling to room temperature and then unloading.

Figure 15 - Stress-strain relationship obtained by cyclic compression tests on samples with/without pre-compression at room temperature.

Figure 16 - Shape fixation rate as a function of weaving temperature.

Figure 17 - Shape recovery rate as a function of braiding temperature.

Figure 18 - Shape recovery of EVA foam after clamping at room temperature for different periods of time.

Figure 19 - Stress-strain relationship (a) of EVA foam compressed to 0.329 MPa/0.1645 MPa and then maintained at the applied compressive stress for 24 hours before unloading, and corresponding strain/stress vs. time (b).

Figure 20 - Evolution of the recovery rate in samples with different compressive stresses of 0.329 MPa and 0.1645 MPa respectively.

Figure 21 - Illustration of an embodiment of the invention (fifth embodiment).

Fig. 22 is a diagram of an embodiment of the present invention (sixth embodiment).

Fig. 23 is a diagram of an embodiment of the present invention (seventh embodiment).

Fig. 24 is a diagram of an embodiment of the present invention (eighth embodiment).

Figure 25 - Illustration of a sole of an embodiment of the present invention.

Figure 26 - Illustration of a method embodiment of the present invention.

detailed description

The basic principle of the present invention is the use of shape memory materials (SMM), characterized by a shape memory effect (SME). The shape memory effect (SME) is generally described as a shape-switching phenomenon whereby a shape memory material (SMM) is able to pass through the correct stimulus (such as heat (thermal response)), light (photoresponse), chemical (including water, chemical response) ), the presence of a magnetic field (magnetic response), a mechanical load (mechanical response), etc.) return to their original shape. This is in contrast to memory foam, which provides instant deformation, but slowly returns to its original shape, and therefore has no ability to maintain a temporary shape, ie, no SME. The polymers exhibiting shape memory effects of the present invention have both a visible current (temporary) form and a stored (original or permanent) form. Once a polymer has been fabricated by conventional methods, processes such as heating, deforming and finally cooling transform the material into another temporary form. The polymer retains this temporary shape until activated by a predetermined external stimulus (in this example, heat) to change into a permanent form. By reheating the material it can be converted into its original (permanent) shape, again ready to be processed into another temporary form.

Based on this principle, shape memory polymer materials can be easily deformed into temporary shapes within a suitable temperature range (about 45°C to about 80°C or below about 80°C). After cooling, the temporary shape is largely retained while still being flexible enough and stiff enough to provide support.

In a preferred embodiment, the flexibility is such that the material deforms easily by stretching/bending of the hand or pressing of a finger, and provides good elasticity to return at the same time. The measurement of Young's modulus can be used to measure stiffness. The range of Young's modulus for this application is preferably 0.001 GPa to 0.5 GPa, such as, 0.005 GPa, 0.01 GPa, 0.05 GPa, 0.10 GPa, 0.15 GPa, 0.20 GPa, 0.25 GPa, 0.30 GPa, 0.35 GPa, 0.40 GPa, 0.45GPa or the range between any two of these figures. When needed, the material returns to its original (permanent) shape only when heated again for another round of trimming. Because shape-memory polymer materials, including their composites and blends, can provide the desired combination of rigidity and flexibility, they can be used in this comfortable fit shoe.

In order to achieve the purpose of a comfortable fitting shoe as described above, the basic requirements of polymer foams are, inter alia: 1) Flexible/elastic at both low and high temperatures. Elasticity can also be measured by Young's modulus, preferably in the range 0.001GPa to 0.5GPa, such as 0.005GPa, 0.01GPa, 0.05GPa, 0.10GPa, 0.15GPa, 0.0.20GPa, 0.25GPa, 0.30GPa, 0.35GPa, 0.40 GPa or 0.45GPa or the range between any two of these figures; 2) able to maintain temporary shape (shape fixation rate ≥ 40%, such as, shape fixation rate > 42%, shape fixation rate > 44%, shape fixation rate > 46%, fixed shape rate > 48%, fixed shape rate > 50%, fixed shape rate > 52%, fixed shape rate > 54%, fixed shape rate > 56%, fixed shape rate > 58%, fixed shape rate > 60 %, Shape fixed rate>62%, Shape fixed rate>64%, Shape fixed rate>66%, Shape fixed rate>68%, Shape fixed rate>70%, Shape fixed rate>72%, Shape fixed rate>74% , shape fixation rate >76%, >78% or >80%; 3) good shape recovery ability (shape recovery rate ≥ 40%, such as, shape recovery rate > 42%, shape recovery rate > 44%, shape recovery rate >46%, Shape Recovery >48%, Shape Recovery >50%, Shape Recovery >52%, Shape Recovery >54%, Shape Recovery >56%, Shape Recovery >58%, Shape Recovery > 60%, shape recovery >62%, shape recovery >64%, shape recovery >66%, shape recovery >68%, shape recovery >70%, shape recovery >72%, shape recovery >74 %, shape recovery >76%, shape recovery >78%, or shape recovery >80% and shape recovery can be used to quantify this ability (see Figures 16 and 17, Equations 1-3); and 4) especially The heating temperature for activation during wear (weaving) should be only slightly above body temperature. A temperature not exceeding 60°C is still an acceptable temperature because the human body can tolerate the temperature for a short period of time, even with bare feet for a few seconds. Furthermore, for the polymeric materials of the present invention, the activation temperature is typically in the range of Tg (glass transition) or Tm (melting) ± 10 to 15°C.

The present invention contemplates eight possible embodiments of such a moldable shoe or shoe insert:

In a first embodiment (Fig. 1), the shoe can be designed to be very thin (about 1mm to 3mm) and lightweight, and can be easily packed and stored with minimal storage space. To get a perfect fit, the shoe is first heated to about 50°C using warm water, an oven, a heater or a hot air blower (such as a hair dryer), thus making the shoe moldable (or giving the shoe a moldability depending on the type of material used). other types of stimulation), the user then inserts his/her foot (1) into the shoe or shoe insert (2), which will deform to fit the shape of the user's foot. As shown in this figure, a moldable shoe or shoe insert covers the entire surface of the foot, up to the user's ankle, providing stability to the entire foot. After cooling, the deformed shape retains proper stiffness and flexibility. The user gets a comfortable fitting shoe with an interior shape contour custom molded to the shape of his/her foot. For example, unlike Crocs shoes, there is no additional gap between the foot and the shoe, making it more comfortable and thus reducing the risk of injury from sliding feet. There is no extra internal space and incorrect pressure between the foot and shoe, so potential risk of injury can be minimized. Furthermore, the shoe can be made very thin and allows the user to further protect them by using the product as an insole inserted into a normal shoe (3) (i.e. a removable inner part) if desired, for example, for walking on rough ground. foot lining to eliminate possible discomfort caused by rough ground (e.g. thicker rocks) or harder/harder shoes. In this way, a comfortable fit can be maintained even if the user is wearing normal shoes. Such a moldable shoe or shoe insert can be deformed back to its original shape when heated a second time. With this material, the fitting process is repeatable and instant, whereby a comfortable fit can be easily achieved.

In a second embodiment (Fig. 2) the moldable shoe insert (2) is pre-fixed to the inner surface of the normal shoe (3), acting as a non-removable inner lining of the normal shoe.

This can be achieved by using known adhesive products used in shoe manufacturing. All forming processes are the same as those mentioned in the first embodiment. Good fit properties can still be achieved in such embodiments.

In a third embodiment (FIG. 3), the moldable shoe made of shape memory polymer material is about 2 to 15 mm thicker than the shoe of the first embodiment in order to provide better protection for the user.

In a fourth embodiment (Fig. 4) a thick outsole (4) can be added underneath the moldable shoe (2). With this extra base layer, the shoe is able to handle rougher ground conditions without compromising the comfort fit. The bottom layer or outsole material can be made of a harder and wear resistant material with/without shape memory effect. Multiple layers may also be incorporated in selected areas of the surface with impact-absorbing material to accommodate athletic activities such as jogging. In another example, thermoplastic polyurethane (TPU) in dissolved tetrahydrofuran (THF) can be used in the inner and outer layers to provide a degree of breathability and prevent (particularly those made of foam) shoes from breaking down due to sweat. It smells bad. Vents/slots can also be incorporated in key areas to further reduce fouling.

In a fifth embodiment ( FIG. 21 ), a shoe 100 manufactured by 3D molding is shown. The entire shoe is made of the same material, 104 denotes cuts/holes or other weakening features (eg, dimples); 102 denotes thicker sections for better support.

In a sixth embodiment ( FIG. 22 ), an insole 120 is shown comprising a plurality of indentations 122 . The plurality of indentations 122 can be vias/non-vias, or even slots/grooves. The plurality of indentations 122 are configured to deform the insole 120 when the sock 124 is placed on the insole 120 . It should be noted that the insole 120 may also be made from uneven layers of foam to enhance fit and comfort. 124 may be pre-glued to insole 120 . When the insole 120 is heated, it becomes soft so that the sock-shoe can be easily put on. After cooling, the insole becomes as hard as the shoe.

In a seventh embodiment ( FIG. 23 ), a free-size shoe 150 is shown that is folded to form a shoe. The shoe 150 is formed by using at least one fastener 160 (such as, ) connects the first flap 152 to the second flap 154 (or vice versa) to form the front of the shoe 150. Rear fasteners 158 are also configured to connect to each other to form a heel counter for shoe 150 . It should be noted that the foam layer 156 of the shoe 150 is not uniform for enhanced fit and comfort. Fastener 158 may be a hook and loop type or any other form of strong temporary fastener. As with the other embodiments, heat is required to soften the shoe first.

In an eighth embodiment (FIG. 24), another free-sized shoe 180 is shown, which is folded into shoe form. The shoe 180 is formed by connecting the third flap 182 to the fourth flap 188 (or vice versa) using at least one fastener 190 to form the front of the shoe 180 . The shoe 180 does not include a heel counter, but instead includes a heal guard 186 . It should be noted that the foam layer 184 of the shoe 150 is non-uniform and includes through/non-through holes and even slots/grooves for enhanced fit and comfort. As with the other embodiments, heat is required to soften the shoe first.

Referring to Figure 25, the sole portion 200 of the previous embodiment is shown. The sole portion 200 can be deformed whereby the deformation is substantially at the central portion 204 which includes through holes/non-through holes and even slots/grooves. Additionally, the ball of the foot portion 202 and the heel portion 206 are made of different materials (with/without shape memory effect) for grip and comfort.

In another aspect, referring to FIG. 26, a method 300 for forming a shoe is provided. A shoe is fabricated from a layer of stimulus-responsive (thermally responsive) shape memory material by method 300, which includes heating the layer to a predetermined temperature (302). The predetermined temperature is between 45°C and 80°C. Additionally, method 300 includes deforming ( 304 ) the layer, wherein deforming the layer is performed by placing the foot structure on the layer. The foot structure can be derived from a human body or a foot model. Deformation of the layer may include deformation of a plurality of indentations within the layer, including vias/non-vias and even slots/grooves. Finally, method 300 includes manipulating the layer with at least one fastener to form a shoe (306). It should be understood that manipulation of layers is by folding.

Industrial Applicability

Moldable shoes or shoe inserts according to the invention have also proven to have great potential for sports and medical applications. The following is a non-exhaustive list of various potential applications:

School shoes; fashion shoes; beach shoes; shoes for people with diabetes; temporary shoes for people with fractures; inner shells for ski boots; quick personalized shoes for ice rink rentals; flippers; bicycle shoes that attach directly to bicycle pedals; and people with unusually shaped feet shoes.

In addition to the feet, the concept of the present invention can be extended to support the elbows, knees and even the bottom etc. to provide not only comfort but also protection.

example

Figure 5(I) shows an embodiment of a moldable shoe or shoe insert of the present invention. When heated to slightly above body temperature (eg, 45°C), the shoe becomes soft and highly elastic. Thus, the user can easily wear the shoe in the same way that they would wear elastic socks for a perfect fit. After cooling back to body temperature, the material becomes slightly stiffer, but still flexible enough to walk comfortably. Due to e.g. slight shape differences of the user's feet, e.g. between early morning and afternoon, reheating is required for each refitting, the shoe can be reheated to 45°C for re-use/refitting. Figure 5(II) is also an embodiment of the moldable shoe or shoe insert described above. In Fig. 5(IIa), the top sock was modified by coating it with a layer of low flow index thermoplastic polyurethane, while the bottom is the original sock for comparison. A low flow index, such as about 3g/10min to 20g/10min, is to ensure that the material "flows" when it is subjected to stress rather than gravity. When a thin layer is applied to the sock, the sock, unlike normal socks, can retain the shape of the foot after being deformed at knitting temperatures, rather than shrinking to its original size. After heating to about 60°C, the TPU softens, and the sock is altered. When the altered sock cools to slightly above body temperature, TPU can still be molded. Thus, the altered sock can be conveniently donned as a moldable shoe or shoe insert. After a few minutes the TPU becomes fully crystallized, so the sock becomes slightly stiffer and thus less elastic than the original sock (hardness should range around 0.001 to 0.5GPa), but is still flexible enough for the user to move around (Fig. 5(IIb)). The socks retained their new shape even after they were taken off (Fig. 5IIc). Only after heat softens the thermoplastic polyurethane does the sock return to its original shape and can subsequently be reused.

The present invention also contemplates the use of composite materials such as EVA/TPU blends, EVA/PCL (polycaprolactone) blends, silicone/TPU blends, silicone/PCL blends, silicone/melt glue. Glass/carbon fiber materials are available for reinforcement. While some shape memory materials according to some embodiments can be heated to 45°C to 80°C, for some other materials such as PCL-based polymers, people can wear it even when cooled to room temperature, because such The material takes an insanely long time to harden, even at room temperature.

Materials such as PCL and TPU have high melting temperatures (over 60° C.), but take up to 10 minutes to fully crystallize at or below body temperature. Thus, shape-memory polymer materials made from them can be heated to their melting temperature and then "wear" at room temperature.

Both foam and solid polymeric materials can be used.

From a manufacturing and logistics standpoint, capital investment and manufacturing and storage efforts are greatly reduced as the moldable shoe or shoe insert is not sized and differentiated on the right or left side . On the other hand, from a customer perspective, instead of trying to find the right shoe size, every shoe is now guaranteed to fit either foot, every shoe is now guaranteed to fit either foot.

In Figure 5(II), socks are used as the elastic component and thermoplastic polyurethane is used as the conversion component. The process of fixing a temporary shape is traditionally called braiding, while the process of heating to return to the original shape is called shape restoration.

Materials, Thermal Analysis, and Sample Preparation

The material studied in this study is a commercial EVA foam with a thickness of about 5.6 mm and a porosity of about 15%. Figure 6 shows a cross-section of the foam board and an enlarged view under a scanning electron microscope (SEM). Samples for thermomechanical testing were cut from EVA sheets.

Differential scanning calorimetry (DSC) tests were performed using a TA Instruments (Newcastle, Germany, USA) Q200DSC between 0°C and 100°C at a heating/cooling rate of 5°C/min (under nitrogen atmosphere). As shown in Figure 7, this EVA has two transitions. Glass transition occurs at about 55°C, while melting and crystallization are achieved by heating and cooling at 80°C and 65°C, respectively. In applications such as comfortable moldable shoes or shoe inserts, a glass transition between about 50°C and 60°C (inset of Figure 7) is advantageous because such a glass transition between 50°C and 60°C The temperature range between is suitable for the human body. Any temperature above 60°C may make the user feel too hot to wear (and thus not last for a long time).

According to the ASTM D638 standard (Type IV), dumbbell-shaped samples (as shown in Figure 8) and small rectangular samples (25×20mm) were cut from EVA foam for uniaxial tensile test and compression test, respectively. Unless otherwise stated, stress and strain used in this study are for engineering stress and engineering strain, respectively. Engineering strain/stress is related to engineering applications, not fundamentals (for theoretical studies and simulations, etc.).

Experiment and Results

To determine whether the material could be used in moldable shoes or shoe inserts, uniaxial tension and uniaxial compression were performed at different weaving temperatures. In addition, a room temperature cycle test was performed to reveal whether the material still has excellent elasticity with high comfort in weaving/unknitting.

Uniaxial Tensile Test

Uniaxial tensile tests were performed using an Intron (Norwood, MA, USA) 5565 testing system with an integrated temperature-controlled chamber. In all tests, a constant strain rate of 10 ^-3 /s was used for both loading and unloading.

A typical thermoresponsive SME cycle applied in this study consists of two processes, preparation and recovery, with four main steps (a–d), as shown in Fig. 9.

In step (a), after stretching to a specified maximum strain (ε _m ) at a given test (programming) temperature within the glass transition temperature range under study, the sample is cooled to room temperature (approximately 22 °C) to maintain a maximum Strain and then unload (step b). The resulting residual strain is _denoted by ε1. This is the first process of compilation. During the next recovery, after the imposed constraint is removed, the sample may recover slightly at room temperature due to creep (c), so the residual strain drops to ε ₂ . Finally, the sample is heated for 5 minutes slightly above (less than 5°C) the previously prepared temperature (step d), the remaining strain is expressed as ε ₃ . Note that significant creep in EVA foam was only observed in samples deformed to high strains at room temperature. Therefore, unless the preparation is done at room temperature, for other preparation temperatures, That is, step c can be ignored.

Figure 10 shows three typical stress-strain relationships of EVA samples pre-stretched to 30% of the maximum weaving strain at three different temperatures, namely, 50°C, 55°C and 60°C. It can be seen that the sample pre-stretched at the lowest temperature (50 °C, dashed line) has the lowest residual strain (22.6%). The maximum residual strain was found to be about 27.4% in the pre-stretched sample (gray line) at a maximum temperature of 60°C. Since the glass transition temperature of this material is between 50°C and 60°C, this experiment confirmed the shape fixation rate of this material in the above temperature range.

See Figure 9. Instant shape fix rate and the long-run shape fixation rate can be defined as:

and the shape recovery rate (R _r ) can be defined as,

During the subsequent recovery, the samples were heated to a temperature more than 5°C lower than their respective pre-stretching temperature for 5 minutes. All samples were found to be able to fully recover their original shape.

Figure 11 shows three typical stress-strain curves when stretched to a maximum strain of 80% at 50°C, 55°C, and 60°C, respectively. The observation shows the same trend as in Figure 10, but the residual strain is much higher (about 70%). In addition to small deformations (30%), the case of large deformations (80%) should also be considered, because users may also experience large deformations in this application. Therefore, the shape fixation rate and shape recovery rate after large deformation should also be studied.

After heating to more than 5°C lower than their corresponding pre-stretching temperature for 5 minutes, all samples were able to recover almost completely their original shape. The shape fixation and shape recovery ratios of individual tensile and uniaxial compression (mentioned below) samples in one single SME cycle are discussed in detail below.

Figure 12 shows the stress-strain relationship in cyclic uniaxial stretching at room temperature in samples with/without pretensioning. Pre-stretching was carried out at 60°C to a maximum strain of 30% or to a maximum strain of 80%. Note that here, for simplicity, the calculation of engineering strain is based on the gauge length in each individual test. Five cycles were performed with 10%, 20%, 30%, 40% and 50% of the maximum weaving strain (in increasing order). In the last cycle of all samples, there was a duration of 5 minutes before unloading.

The stress-strain curves of the samples with 30% and 80% pre-stretching show that the residual strain after unloading in each cycle is almost the same as that of the samples without pre-stretching. On the other hand, a small difference between the 30% pre-stretched sample and the pristine sample was observed. There is some significant residual strain after unloading in each cycle. Furthermore, as the maximum strain under load increases, the corresponding residual strain increases. However, it was observed that the residual strain could be largely removed 10 minutes after unloading.

Thus, it can be appreciated that at room temperature, a foam with or without prestretching can be considered to have greater elasticity with a finite elastic viscosity. It should be noted that, as expected, the stress-strain curve of the sample with 30% pre-stretch is only slightly higher than that of the sample without pre-stretch, the sample with 80% pre-stretch seems to be more hard. Furthermore, larger hysteresis in samples with higher pretension indicates higher energy dissipation during loading/unloading cycles. It appears that the effect of pre-tensioning strain (at least up to 30%) has no significant effect on the mechanical response of the foam.

Uniaxial compression test

Rectangular samples were used in a series of single and cyclic uniaxial compression tests. Use the same testing machine and parameters as mentioned above for the uniaxial tensile test. Three samples were compressed by 30% at three different temperatures (ie, 50°C, 55°C and 60°C), then kept cooled to room temperature and finally unloaded. Figure 13 shows the stress-strain relationship of these three samples during the preparation process. It can be seen that, like uniaxial stretching, the sample tested at the highest temperature of 60°C has a maximum residual strain of about 30%, while the sample tested at the lowest temperature of 50°C has a minimum residual strain of about 25%. Subsequently, the three samples were heated to slightly above their respective weaving temperature for 5 minutes to induce heat-induced shape recovery. All residual one-step strains are observed to be very small. An 80% pre-compression test was also performed. Their stress-strain relationships are shown in Figure 14. Typically, the residual strain is around 75% and follows the same trend as above, ie, higher weaving temperature leads to larger residual strain. After programming compressed to 80%, the samples were heated to slightly above their rewritable programming temperature for 5 minutes as previously described. Afterwards, the thickness of all samples was measured. The remaining strain was found to be about 40% in all samples.

Figure 15 presents the stress-strain relationship in three cyclic compression tests at room temperature for samples with/without precompression. Precompression with a maximum weaving strain of 30% or 80% was generated at 60°C as previously described. In the cycle, all samples had three maximum programming procedures applied, namely 15%, 30% and 45% (in increasing order). At the end of each cycle, no significant residual strain was observed in all samples, indicating an excellent elastic response in both precompressed and pristine samples.

Unlike the uniaxial tension in Figure 12, Figure 15 shows that although the stress-strain curve of the 30% precompressed sample is very close to that of the sample without precompression (same as uniaxial tension), the 80% precompressed The samples were significantly stiffer than the pre-compressed samples after being compressed to a strain above 20%.

Shape fixation rate and shape recovery rate

While shape fix rate is a measure of how well a fit shoe adapts to the contours of a particular foot, shape recovery rate shows a fit shoe's ability to return to its original size during the next round of fit. Figure 16 plots the shape fixation rate as a function of weaving temperature for both uniaxial tension and uniaxial compression at two different strains of 30% and 80%.

It can be seen that the shape fixation rate exceeds 75% in all tests. usually:

- A higher knitting temperature always results in a higher rate of shape fixation, whereby a higher rate of shape fixation is ideal for the shoe to maintain a temporary shape to ensure greater comfort. Regardless of elastic deformation, the higher the rate of shape fixation, the better the shoe can retain the deformed shape. The perfect ratio is 100%, which means the material keeps the exact shape of the user's foot. In fact, any ratio above 75% can be considered suitable for this application.

However, high temperatures, for example in excess of 60°C, may be unbearable for many people.

- the rate of shape fixation in compression is generally higher than in tension;

- Higher maximum weaving strains are more effective in increasing the shape fixation rate, but this does not apply at higher weaving temperatures.

Figure 17 shows the shape recovery rate as a function of braiding temperature under uniaxial tension and uniaxial compression at the maximum braiding strain of 30% and 80%. Clearly, while poor shape recovery (only between 40% and 55%) was observed in all woven samples by compression to the maximum weaving strain of 80%, all remaining samples had very high shape recovery rates. In particular, the shape recovery was 100% in all 30% stretched samples. Therefore, it can be concluded that:

- the rate of shape recovery is more or less independent of the weaving temperature;

- Higher shape recovery results in samples with lower weaving strain;

- Shape recovery is bad only in woven samples by overcompression.

Effects of long-term compression

During use, body weight can often be applied continuously for hours. As shown in Figure 18(a), a piece of EVA foam was pressed at room temperature using two clamps (Figure 18b). After 80 minutes, one clip was removed (Fig. 18c1), and the other clip was applied for 115 hours (Fig. 18d1). The dent after 80 hours of clamping mainly recovered after 40 hours (Fig. 18c2), while the dent after 115 hours of clamping was still visible after 23 days (Fig. 18d4), which disappeared only after heating in boiling water (Fig. 18e). For accurate identification, we took a rather extreme investigation, in which a small piece of EVA foam was first compressed to a maximum stress of 0.329MPa, which should be the maximum foot pressure of a normal young person, and then held for 24 hours before being removed .

Figure 19(a) (black line) plots the stress-strain relationship of the samples throughout the testing period. We can see that when loaded to 0.329 MPa, a compressive strain of about 64% is recorded. In the ensuing 24 hours, the compressive strain gradually increased to 80%. After unloading, the residual strain was 74%. For comparison, in another test, the maximum applied compressive stress was halved to 0.1645 MPa. Figure 19(a) plots the resulting stress versus strain curves in gray. It can be seen that despite the applied stress being halved, more creep-induced strain was observed (about 10% more), while more strain recovery was found after unloading (about 4%). Figure 19(b) plots the evolution of strain and stress versus time throughout the loading/unloading process. It appears that during the load hold period, the strain increases gradually become smaller and smaller. There is practically no further strain increase for about 15 hours (for 0.329 MPa) or 18.5 hours (for 0.1645 MPa). As expected, higher applied stress required less time to stabilize the creep strain. In the next step, both samples were left in air at room temperature for 120 hours and recorded every 24 hours. Finally, the samples were heated to 60°C for 10 minutes. The corresponding shape recovery rates were calculated and plotted in FIG. 20 . We can see that the curves of shape recovery rate versus time are about the same for both samples. The speed of shape recovery gradually decreases over time. Both had approximately 85% recovery after 120 hours in air at room temperature. Further heating to 60° C. for 10 minutes resulted in complete shape recovery of 0.1645 MPa.

Therefore, it should be reasonably concluded that this EVA foam is suitable for reasonable prolonged wear. After prolonged wear at room temperature, its excellent heat-sensitive SME is lost. According to Fig. 10, Fig. 11 and Fig. 13, Fig. 14, at high temperature, EVA foam is soft and can be stretched or compressed by 30% or more. Therefore, shoes made of this foam should be easy to put on while ensuring a comfortable fit. As shown in Fig. 16, the corresponding shape fixation ratios in both uniaxial tension and compression are high, enabling the foam to largely maintain the woven shape. Thus, the temporary shape of a shoe made of this foam is able to largely retain the individual shape after "knitting". Even when woven to a strain of 80% under uniaxial tension or uniaxial compression, the foam remains highly elastic at room temperature, as shown in Figures 12 and 15, which show that the soft shoe is still elastic, even Stretched to 50% or compressed to 45%. Thus, a prepared personalized shoe is not only easy to take off and put on, but also comfortable to wear. The high elasticity at room temperature also means that even after knitting, the shoe is able to mostly retain its individual shape over short to medium load times. For prolonged loads, this foam tends to creep (Figures 18 and 19), but most of the deformation due to creep recovers automatically, even without heating (Figure 20). Can be heated up to 60°C to induce almost complete shape recovery.

Excellent heat-induced shape recovery was observed in Figure 17, except for the 80% compressed foam. A possible reason behind the difficulty in shape recovery is excessive compression of the foam at high temperature. One possible way to eliminate this problem is to reduce the deformation of EVA foam. Theoretically, for the same compressive load, as the stiffness of the material increases, the corresponding deformation decreases accordingly. For this EVA foam, its stiffness can be easily increased by reducing its porosity.

According to Figure 16, the best results for the shape fixation rate in all tests were always obtained at a weaving temperature of 60°C, which was 15°C higher than the comfort temperature. Therefore, the glass transition temperature of this EVA should be slightly lowered.

The results of a series of experiments with EVA foam showed that this foam can meet most requirements for a comfortable fit, especially for moldable shoes. It's highly resilient in both high and low temperatures, so it can be easily braided for a pleasant fit and use.

After braiding, custom shapes can be largely maintained. Unless overcompressed at high temperatures, there is usually good SME shape recovery and subsequent reuse.

Claims (25)

1. a kind of moldable footwear or footwear insert, the moldable footwear or footwear insert extend through whole sole when in use, And prepared by stimuli responsive shape-memory material (SMM).

2. moldable footwear according to claim 1 or footwear insert, wherein, the stimuli responsive shape-memory material is heat Respond shape-memory material (SMM).

3. moldable footwear or the footwear insert according to claim 1 or claim 2, wherein, the SMM is shape memory Polymer (SMP).

4. moldable footwear according to any one of claim 1 to 3 or footwear insert, wherein, the stimuli responsive shape Between memory material is initially heated to about 45 DEG C and about 80 DEG C or below about 80 DEG C.

5. moldable footwear according to claim 4 or footwear insert, wherein, the surface temperature of the material is not when in use More than 60 DEG C.

6. moldable footwear according to any one of claim 1 to 5 or footwear insert, wherein, the stimuli responsive memory Material selects ethylene-vinyl acetate copolymer (EVA), polyurethane (PU) or thermoplastic polyurethane (TPU), or the group of above-mentioned item Close.

7. moldable footwear according to any one of claim 1 to 6 or footwear insert, wherein, the stimuli responsive shape Memory material is characterized by the rigidity and/or elasticity of the Young's modulus based on 0.001GPa to 0.5GPa.

8. moldable footwear according to any one of claim 1 to 7 or footwear insert, wherein, the stimuli responsive shape Memory material is characterised by that temporary shapes can be kept under at least 40% shape fixed rate.

9. moldable footwear according to any one of claim 1 to 8 or footwear insert, wherein, the stimuli responsive shape Memory material is characterized by the shape-recovery capabilities of at least 40% shape recovery ratio.

10. moldable footwear or the footwear insert according to any one of claim 2 to 9, wherein, the SMM has about 1mm To 3mm thickness.

11. moldable footwear or the footwear insert according to any one of claim 2 to 9, wherein, the SMM has about 2mm To 15mm thickness.

12. moldable footwear according to any one of claim 1 to 9 or footwear insert, wherein, the stimuli responsive shape Memory material is applied on textile material.

13. moldable footwear according to claim 12 or footwear insert, wherein, the coating is characterized by about 3g/10min to 20g/10min low flow index.

14. a kind of moldable footwear, the moldable footwear are prepared by stimuli responsive shape-memory material layer, wherein, the layer It is configured to operate to form the footwear using at least one fastener.

15. moldable footwear according to claim 14, wherein, the stimuli responsive shape-memory material layer includes multiple recessed Trace, the multiple indenture are constructed such that the material layer can deform.

16. the moldable footwear according to claims 14 or 15, wherein, at least one opening week in the multiple indenture Boundary defines the opening in the material layer.

17. the moldable footwear according to any one of claim 14 to 16, wherein, the stimuli responsive shape-memory material Layer is uniform.

18. a kind of moldable footwear, the moldable footwear are prepared by material layer, and the material layer is remembered including stimuli responsive shape Recall material and secondary materials, wherein, the layer is configured to operate to form the footwear using at least one fastener.

19. moldable footwear according to claim 18, wherein, the stimuli responsive shape-memory material layer includes multiple recessed Trace, the multiple indenture are constructed to be permeable to deform the material layer.

20. the moldable footwear according to claim 18 or 19, wherein, at least one opening week in the multiple indenture Boundary defines the opening in the material layer.

21. the moldable footwear according to any one of claim 18 to 20, wherein, the stimuli responsive shape-memory material Layer is uniform.

22. a kind of method for forming footwear, the footwear are prepared by stimuli responsive shape-memory material layer, methods described bag Include：

The layer is heated to predetermined temperature；

Deform the layer；And

The layer is operated using at least one fastener to form the footwear,

Wherein, the deformation of the layer is by the way that leg structure is placed on the layer to carry out.

23. according to the method for claim 22, wherein, the deformation of the layer includes the change of multiple indentures in the layer Shape.

24. the method according to claim 22 or 23, wherein, the predetermined temperature is between 45 DEG C to 80 DEG C.

25. the method according to any one of claim 22 to 24, wherein, the operation of the layer is carried out by folding 's.