DE2550074A1 - ULTRASONIC WELDED PLASTIC BODY - Google Patents

Description

Ultrasonically welded plastic body

The invention relates to a composite plastic body of high load capacity with at least two by ultrasonic welding interconnected parts.

At high temperature to process thermoplastics that temperatures of more than 175 ° C (350 ⁰ F) can withstand, are increasingly being used to replace metals in many applications. Recent advances in the development of high temperature resistant materials suitable for injection molding have further increased their usefulness as a variety of shapes can now be made without costly machining. A further improvement in the mechanical properties of these thermoplastics at high temperatures has been achieved by incorporating fillers, in particular glass fiber fillers. In this way, parts can be produced by injection molding that can be used at temperatures of more than 200 ⁰ C (400 ⁰ F)

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can be used continuously with good results. As expected, such materials are difficult to process and require to obtain an adequate flow during the injection molding high pressures and temperatures of more than 295 ⁰ C (550 ⁰ F), and even often in excess of 315 ° C (600 ⁰ F). However, intricate shapes with thin sections and narrow passages are extremely difficult to manufacture using these poorly flowing materials in the molten state; furthermore, weak points in the material on welding lines and the like cause greater difficulties, in particular when thermoplastics with glass fiber filler are used.

High temperature resistant with glass fiber fillers Thermoplastics could also be used for more complex shapes and larger parts if methods were available with where assembled parts are connected or glued together reliably and with high strength in the connection area could. Methods are known with which many thermoplastics can be joined, including joining with adhesive

fabric, thermal welding and ultrasonic welding, the express However, application to thermoplastics j to be processed at high temperature was less successful, especially when with glass j fiber-filled thermoplastics were used. The possibilities The bonding of high-temperature-resistant materials is therefore limited, as only a few of the available adhesives have adequate properties at the high service temperatures. The thermal welding is made more difficult that this Materials have the peculiar and otherwise very desirable

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Shank have to offer resistance to flow, if none

high temperature and no high pressure is used. Ultrasonic welding processes for thermoplastics are known in which the energy is collected at the connection point, which leads to a very localized heating and thus to a flow and Fusion of the thermoplastic leads in the connection area. Ultrasonic welding is successfully used to join parts some thermoplastics to be processed at high temperature are used for thermoplastics with glass fiber fillers, especially in those where the proportion of glass fiber fillers is more than 20% by weight of the total mass, poor results are generally obtained if the parts are welded by ultrasound be joined together. For more details on the use of ultrasonic welding of thermoplastics, including also thermoplastics with fiberglass fillers, see an article "Instructions for ultrasonic welding of plastic materials" in the journal Appliance Manufacturer 1974, April issue, pages 85 and 86 referenced.

There is therefore an urgent need for a method for joining parts that are reinforced with fiberglass fillers, th, thermoplastics to be processed at high temperature;

are, with which resilient connections can quickly j

i and reliably manufactured. Such a procedure would leave

can also be used to great advantage for many applications.

The inventors have found that by injection molding as well manufactured from parts to be processed at high temperatures "

Thermoplastics that contain a high proportion of glass fiber filler, can be welded with success by ultrasonic welding processes. More specifically, parts can be made out with fiberglass filler provided high-temperature thermoplastics are manufactured by injection molding in such a way that they have a special surface Have microstructure resulting from non-uniform dispersion of the fiberglass filler in the resin matrix Ultrasonic welding are firmly joined together, so that a very resilient connection point between the parts is obtained.

Ultrasonic welding of parts made from thermoplastics is a technique known to those skilled in the art and is used for parts non-filled thermoplastic synthetic resins Distribution. Materials filled with fillers are more difficult to weld by ultrasound, especially when than Filler glass fibers are used. In the literature it is stated that this difficulty is due to the fact that the Glass fiber-plastic compounds necessarily have a smaller amount of resin at the interface; it was thought that this amount was not sufficient to allow adequate fusing of the parts, especially when the glass fiber content is up more than 20% by weight of the mass was increased. Previously it was thought that with even higher proportions of the glass fiber filler, in particular with proportions of the glass fiber filler of 40% and more, not even weakly resilient welds are obtained because the amount of resin present at the interface was insufficient to completely cover the joint area

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to fill and melt to form the connection.

The inventors have now found that thermoplastics with 40% glass fiber filler can be produced with good results by ultrasonic welding equipment can be welded. Given the popular belief that there is a high level of resin at the interface In order for a connection to be obtained it is very surprising that the best connection is obtained between surfaces which are intentionally made in such a way that the glass fiber content is increased in the surfaces in the area to be joined will. In particular, parts that have been injection molded from glass fiber reinforced high temperature thermoplastics under conditions where there is a visible concentration of the glass fiber filler on the surface is obtained, are welded with success so that strong load-bearing joints are obtained. Against it can be used with parts that are injection molded under conditions that have a high concentration of resin on the surface is obtained and in which the glass fiber filler is essentially is completely sunk into the resin matrix, no load-bearing welded joints are obtained under the same welding conditions will.

The injection molding of thermal ' plastic can be made on conventional injection molding machines using high temperatures and high injection pressures and the molds are normally heated to prevent rapid cooling and incomplete filling of the mold. In general for aesthetic reasons, smooth, reflective,

Resin-rich surfaces of the parts are desirable, and to get this look!

i to achieve material temperatures and temperatures of the molds that are higher than the minimum temperature are used with; a complete filling of the cavity of the mold is achieved. Lower mold temperatures and lower temperatures than the optimal material temperature lead to rough, glass fiber-rich surfaces that have a less attractive appearance. Just under these latter conditions, which were usually thought to be disadvantageous for most applications, the glass filler-enriched surfaces required for the purposes of the present invention are obtained.

The invention is explained in more detail below using an exemplary embodiment and with reference to the accompanying drawings. In this show:

FIG. 1 is a photomicrograph, enlarged 100 times, of a smooth, resin-rich surface;

FIG. 2 is a photomicrograph, enlarged one hundred times, of a: rough upper surface enriched with glass fiber filler; area;

FIG. 3 is a perspective view of a pump impeller composed of two parts, which is shown in an exploded view Representation is drawn to show the internal structure can;

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FIG. 4 shows a section along the line 4-4 of FIG. 3; and

FIG. 5 shows a section through an assembled pump impeller along a line perpendicular to its axis.

Using the microphotographs shown as examples in FIGS. 1 and 2, it is now easier to understand what is meant by surfaces enriched with glass fiber filler. Figure 1 shows a hundredfold enlargement of the surface of a sample which has been manufactured by injection molding in such a way that it has smooth, resin-rich surfaces. Samples with smooth, resin-rich surfaces like the one shown in Figure 1 can be produced on an injection molding machine from a polyphenylene sulfide resin with 40% glass fiber filler, with a heating cylinder temperature of 300 ⁰ C (570 ⁰ F) and a temperature of the mold of 82 ⁰ C (180 ⁰ F) is used. From the practically complete absence of visible glass fibers in the surface shown in FIG. 1, it can be concluded that these reflective surfaces are essentially entirely formed by the resin of the matrix.

Figure 2 is a hundred times enlargement of the surface area of a sample which has been injection molded so as to be has a rough surface enriched with fiberglass filler. The part is from that also used to manufacture the one shown in FIG Sample mass used (polyphenylene sulfide resin with 40% Fiberglass filler) made by injection molding. Samples with surfaces that are rich in glass fiber fillers can be

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; same injection molding machine and under the same conditions ¹ the mold was produced

only a temperature of 65 ° C (150 ⁰ F) is used.

The photomicrograph shown in Figure 2 shows that at or near the surface of the part there is a high proportion of glass fiber filler and that a large part of the at The glass fiber filler lying on the surface is partially exposed or only slightly covered with the matrix resin. Macroscopically the surfaces rich in glass fibers according to FIG. 2 are characterized by a spiral pattern and visible roughness and Dullness of the surface, while the resin-rich surfaces according to Figure 1 look essentially smooth and reflective.

It goes without saying that the injection molding conditions are changed so that the characteristic properties of the resin used is taken into account, and furthermore modified in this way that the proportion of glass fiber used in each case

■ filler and the geometry of the part to be manufactured is worn. The manufacture of a given glass fiber reinforced Part of a thermoplastic required optimal injection molding parameters must therefore necessarily through tests

j can be determined. For the purposes of the present invention optimal injection molding parameters lead to parts with blunt, glass fiber-rich surfaces, especially in the areas which are to be connected by ultrasonic welding.

The method according to the invention can be used for welding parts can be used, which are made of a synthetic resin compound provided with glass fiber filler, the latter more than Twenty percent by weight of the total mass of glass fibers and correspondingly less than 80 percent by weight of a thermoplastic resin. Masses with lower glass fiber content can also be injection molded so that they have a surface rich in glass filler, and they can thus be welded according to the present invention. With these materials, however, is also used conventional spraying and joining processes usually produce a satisfactory weld joint of the parts. the Methods of the present invention therefore provide for welding such materials with a low glass filler content only a minor advantage. On the other hand, however, it is possible to use resin compositions with more than 50% by weight of glass fiber filler to be processed by the injection molding process, and the parts thus injection molded, the glass fiber-rich surfaces of the ones described above Art can be joined together with good results using ultrasonic welding equipment. For practical reasons, resins with a very high proportion of glass fiber filler, in particular with proportions of more than 60% by weight, not more for injection molding, especially if the matrix resin is a resin that can be processed at high temperature Is thermoplastic. For this reason, the highest proportion of glass fiber filler in practice is for the purposes aimed at here in the matrix no greater than about 60% by weight. A variety of fiberglass materials are commonly used as fillers for thermoplastics used, with many of these fillers on the surface

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are provided with binders to improve the wetting properties and improve adhesion. By choosing a special glass

fiber filler may change the properties of the j manufactured part and the strength of the welded joint. The process according to the invention can, however, generally be applied to all those provided with glass fiber fillers Apply thermoplastic masses that can be injection molded. Also the use of certain similar inorganic fiber fillers, including potassium titanate fiber fillers for reinforcement of resin compositions for injection molding is possible within the scope of the present invention.

The thermoplastics preferably used for the purposes of the present invention include high-temperature thermoplastics such as polyphenylene sulfide, aromatic polyimides, amide-imide copolymers, aromatic polycarbonates and polysulfones as well as polyphenylene oxides and polyphenylenes. It goes without saying that the thermoplastic compositions provided with glass fiber filler are conventional stabilizers, Color additives and fillers may have, whereby it is the specialist:

j man is known for ultrasonic welding that the! generation of lubricants and plasticizers the weldability ι adversely affected and should be avoided wherever possible. !

It is quite conceivable that for the production of surfaces with that required for successful ultrasonic welding Glass filler enrichment an extrusion under precisely specified Conditions can be used. Similarly, you can

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modified to produce the glass-filler-rich surfaces 'Transfer molding and compression molding processes are used. The manufacture of fiberglass-rich surfaces using any Thermal processing method for thermoplastic resin compositions provided with glass fiber fillers thus falls into the scope of the present invention.

A comparison of the weldability of glass fiber-rich surfaces with the weldability of resin-rich surfaces was made on by injection molding manufactured two-part pump impellers carried out. Polyphenylene sulfide with various proportions of glass fiber filler has been used as the material, and a variety of different Sprxtzgxeßparametern examined. Portions of each of the surface types were then ultrasonically welded and stressed to breakage in the manner described in more detail below and thus tested.

In Figure 3, a two-part pump impeller is shown, wherein two impeller parts 10 and 14 in an exploded view • and perspective view are shown.

The impeller part 10 has a circular plate with a central: on hub 11. Arched wings 12 extend longitudinally}

a surface 16 of the impeller part 10 from a central Axis of the same to the outside. The surfaces of the wings 12 are provided with energy guide surfaces 13 during injection molding. These Energy conducting surfaces are shown more clearly in the sectional view of FIG. 4, which shows a section through a wing and the

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ι adjacent part of the plate carrying it along the line 4-4 of j

I j

Figure 3 represents. The impeller part 14 shown in Figure 3 [

■ is a circular plate with a concentric circular ■

shaped opening which is delimited by a flange 15. The ^Diameter this limited by the flange 15 opening is greater than the diameter of the hub 11. The assembling of the two wheel parts is then effected by the fact that they are assembled so that the Energieleitflächen 13 are in contact with the inner end surface 17 of the impeller portion 14;

the impeller parts are then kept pressed together under pressure and welded together by ultrasound.

As is known to the person skilled in the art of ultrasonic welding, the energy conducting surfaces serve to supply the energy collect that a localized heat build-up is obtained.

The material is melted at the points where the ■

Energy is collected. In the present case one obtains a 'butt weld along each of the wings 12, which between the Wing 12 and the end face 17 of the impeller part 14 is located. The J

The assembled and welded pump impeller is shown in Figure 5

shown in section. ^;

! The quality of the connection obtained was tested in a fracture test measured with the blade of a torque screwdriver between the opposing surfaces 16 and 17

of the welded pump impeller was introduced and a torque lying in the axial direction of the blade on the pump impeller was exercised. This created an outward-facing

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te force exerted on the two surfaces 16, 17 and so long until the pump impeller broke. The torque required to cause fracture is a measure of strength the welded joint. The test carried out essentially corresponds to a tensile test carried out on the welding area.

In the examples given below, parts were made which had a reflective, resin-rich surface (surface type R, as shown in FIG. 1), and there were Injection molding produced parts that had a blunt, glass fiber-rich surface (surface type G, as shown in Figure 2) This was done by injection molding polyphenylene sulfide with various Proportions of fiberglass filler in the manner described above. The proportions are given in parts by weight.

The impeller parts were then assembled in the manner described above and connected by ultrasonic welding, an ultrasonic welding machine with an operating frequency of 20 kHz was used (Branson Sonic Power Company Series 400 Ultrasonic Plastics Welder). The welding times were as in the following Table I listed changed.

The test of the strength of the connection was carried out using a torque screwdriver in the manner described above Way done. The torque at which the pump impeller broke, be it in the volume or at the weld point written down.

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TABEL

Breaking strength of pump impellers, which are produced by ultrasonic welding Injection molded impeller parts are made of fiberglass-coated polyphenylene sulfide.

Sample PPS

(D

glass fiber

No parts parts

(4) surface welding time

Type in seconds Connection strength in kp cm j

1 60 40 R. 0.8 2 60 40 G .5 3 60 40 G .75 4th 60 40 G ok 5 60 40 G 1.25 6th 60 40 G 2.0 7th 80 20th R. 5 8th 80 20th G 5 9 70 30th R. 5 10 70 30th G 5 11 60 40 R. 5 12th 60 40 G 5

6.6 ⁽³⁾ , 8.8 ⁽³⁾ , 4.4 ^(3), 11.3 ⁽²⁾ , 13.3 ⁽²⁾ , 13.3

8.8 ⁽²⁾ , 8.8 ^(3), 8.8 ⁽²⁾ , 8.8 ⁽³⁾ , 8.8 ⁽² >

6.6

(3)

4.4 ⁽³⁾ 6.6 ⁽³ \ 6.6 ⁽³⁾ , ' ₈ , 8 ⁽³⁾ , 6.6 ⁽³⁾ 4.4 ⁽³⁾ , 6.6 ⁽³⁾ 8.8, 8.8, 6.6 4.4 ⁽³⁾ , 6.6 ⁽³⁾ , 6.6 ⁽³⁾ 17.8 ⁽²⁾ , 20 ⁽²⁾ , 20 ⁽²⁾

Remarks:

(1) PPS = polyphenylene sulfide

(2) break in volume

i (3) break at the junction

(4) Surface type: R = resin-rich; G = rich in glass fibers

(5) parts by weight of the total composition

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From the above examples it can be seen that with glass filler rich Surfaces a significantly better strength of the connection at the welding point is obtained. Compares For example, comparative sample 1 with samples 2 to 6, in which the welding was carried out under equivalent welding conditions it can be seen that the strength of the connection when welding surfaces rich in glass fillers (samples 2 to 6) is considerable is greater than when using resin-rich surfaces (sample 1). At the connection points of resin-rich surfaces In fact, the break always occurred in the weld area, while the welded glass-filler-rich surfaces did break in the volume of the material, which shows that the latter compounds have a strength that of the of the material equals in volume.

It can also be seen that the glass filler-rich surfaces improve the properties of the weld joint over a range of glass fiber filler / resin ratios. Samples 7 to 12 correspond to pump impellers of a similar construction, but with a larger diameter (11.5 cm compared to 7.5 cm) and a greater thickness of the plate (3 mm compared to 1.5 mm), which are made of resins with different glass fiber fillers ^!

! content were manufactured by injection molding. Again, German \

; j

lent shown that parts so made by injection molding that they have glass-filled surfaces, always!

lead to welded joints of greater strength. Indeed ί . broke with parts that have been manufactured in this way by injection molding

; were that resin-rich surfaces were obtained, and that by

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Ultrasonically welded, in many cases the pump impeller at the welding point when it has been removed from the welding machine.

The time taken to weld also affects the strength of the joint to some extent. As Sample No. 6 shows, Welding times that are too long can adversely affect the strength of the joint that is ultimately obtained. The optimal Welding parameters depend partly on the resin / glass fiber filler combination used and partly on the size and the shape of the parts as you can by comparing the samples No. 1 to 6 with samples No. 7 to 12 sees.

In the above embodiment of the invention, when assembling the impeller parts of a special pump impeller get butt welded joints. It should be understood, however, that the present invention can be used to connect a large A variety of parts can be used to advantage made by injection molding from fiberglass-filled resins; are made; butt welded joints, butt welded joints and corner welded joints can also be produced in the same way.

be set up. The particular features of the present ER \ invention, and in particular the provision of the glasfüllstoffreichen .Oberflächen in injection molded parts and joining these surfaces by ultrasonic welding for preparing compounds of high strength between the welded parts are not limited to the particular parts illustrated here solely limited, the only to explain the present invention the- |

Thermoplastic parts are very useful as replacements for metal parts, especially where corroded and fouled the parts to be expected. The welded parts can be used at high temperatures because of the high proportions of reinforcing Glass fiber filler can be used; in addition, they offer the additional advantage of lighter weight, which can possibly also lead to an improved efficiency of the parts, since when used as pump impellers or other moving parts of pumps and the like can be saved when driving power. It goes without saying that connections high strength between parts are particularly important for such applications.

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Claims (4)

Claims 1. Composite plastic body with high resilience at least two parts connected to one another by ultrasonic welding, characterized in that the parts (10, 14) consist of a thermoplastic material to be processed at high temperature, which contains between 40 and 80% by weight of a Thermoplastics to be processed at high temperature and 60 to 20% by weight of glass fiber filler; that at least one of the parts (10,14) is thermally formed such that on fiberglass filler exposed on its surface is obtained; and that the parts (10, 14) by an ultrasonic welding device are welded. 2. Plastic body according to claim 1, characterized in that the thermoplastic to be processed at high temperature is polyphenylene sulfide. 6098 23/063 - 19 - 3. Plastic body according to claim 1, characterized in that the thermoplastic material to be processed at high temperature 50 to 70 wt.% polyphenylene sulfide and 50 to 30 Has.% Glass fiber filler. 4. A process for the production of high strength joints produced by ultrasonic welding between Injection molding manufactured parts from a thermoplastic with glass fiber filler, characterized by the following Process steps: Injection molding of a part from a thermoplastic resin compound with 20 to 60% by weight of glass fiber filler, such that fiberglass material visibly exposed on the surface of the part is obtained; Invest this part to a second part, which is made of the same resin composition by injection molding, such that a There is surface contact between the parts; and producing a weld joint between the in contact • stationary surfaces of these parts using an ultrasonic device. §09823 / 0634