Permanent combination of hottest aluminum and poly

Permanent combination of aluminum and polymer

when aluminum alloy is immersed in a certain amine volatile solution, the alloy surface will undergo nano-sized ultra-fine etching. The aluminum alloy that has gone through this process is embedded in the injection mold. PBT (polybutylene terephthalate) or PPS (polyphenylene sulfide) is injected, and the polymeric material is firmly bonded with the aluminum alloy. Taiseiplas Co., Ltd. of Japan calls this technology nano molding technology (NMT). It took three years to commercialize this technology, and mass production using this technology began in April 2004. In addition to aluminum alloy solution processing technology, the development of insert injection mold, polymer material and anode plating method are also necessary. In this paper, the standards for various problems encountered and many bulk waterproof materials obtained from evaluation and testing are formulated by the American Society for testing and materials (ASTM); Some products with enterprise characteristics shall be reported

special effect

a few years ago, Japanese JSR company transferred a new technology to Dacheng Plastic. With this technology, special inks are "baked" into injection molded products, which are embedded in injection molds and injected with thermoplastic elastomers (TPE). The coating and TPE can be adhered together by reaction. The coating allows TPE to inject and adhere to any type of polymer. According to this method, Dacheng plastics successfully replaced polymers with metals. Dacheng coated stainless steel products with a special coating, and injected them with TPE for adhesion. They are manufactured as protective seals for LCD displays used as personal data assistants (PDAs)

the next development step is to try to inject thermoplastic materials into metal. Dacheng has experienced many surprising failures in the application of high molecular polymers, including ultra-high molecular polyurethane (UHMWPE). When they were about to give up, they made another discovery. PBT has been injected into aluminum alloy through a simple process, which is regarded as pretreatment, and it shows a strong adhesion. This is a special effect. Many experiments have been done on similar materials to see whether injection bonding will occur, but such an effect can be obtained only when the metal in question is aluminum and the polymer is PBT or PPS. It seems unnecessary to consider market demand and potential uses

the key of the technology

first immerse the aluminum alloy in the degreaser aqueous solution for a few minutes, and rinse with water. Next, the aluminum was immersed in an acidic dilute aqueous solution and rinsed with water. The dust on the surface of the alloy and oxide layer is removed by chemical methods. This is the basic step before the dissolution process. Next, proceed to process t (t stands for Dacheng Plastic Company). Aluminum is immersed in an aqueous solution containing T material (an amine compound), rinsed with water, and dried. This process is the key of the whole technology

in t process, the surface of aluminum alloy will undergo ultra-fine etching and be covered with ultra-fine pits with a diameter of nm. Observing the surface with an electron microscope, it looks like an area covered with small serrations (Fig. 1). Nitrogen atoms released from porous polystyrene (XPS) can be seen on the surface. This nitrogen comes from t material used in t process. It seems that t material can withstand water rinsing, drying and subsequent storage (more than three months if sealed), and stay on the surface of aluminum. It seems that when the aluminum alloy is immersed in t material, the weak alkalinity of T material will cause ultra-fine etching on the alloy surface and unqualified yield strength of multiple batches of parts after one heat treatment

Figure 1: electron micrograph of aluminum surface before pretreatment (left) and after pretreatment (right) in aqueous solution

solution treated aluminum alloy is embedded into the injection mold. PBT and PPS are injected to obtain an integrated product. Cut the obtained integrated product and observe its profile with an electron microscope. It can be seen that the melt will enter the bottom of the depression on the alloy surface, and the bending diameter is 1mm or less. It can also be seen that there are sawtooth edges of 100nm or less on the dividing line between the resin and the alloy, and the resin also enters the bottom of these depressions (Fig. 2). This is obviously the cause of bonding strength, because it has ultra-fine fixation

Figure 2: vertical section of aluminum and polymer material (PBT) after injection bonding

polymer melt hardens rapidly in the injection mold, so it will not conform to the fine contour of the injection mold surface. The resin can only match the contour with a diameter of several microns at most. However, in nano molding technology, the resin enters the bottom of the ultra-fine depression. This is indeed a mysterious phenomenon, which will be explained below

Figure 3: in order to find out how much resin exists on the junction surface of the dividing line,

Aluminum decomposes in hydrochloric acid diluent, and the residue is analyzed

mysterious phenomenon

it is assumed that t material (amine compound) has been chemically absorbed into the surface of aluminum alloy. When amine compound and plasticized PBT contact each other at high temperature, reaction heat will be generated. It is well known that exothermic reactions occur between amines and esters, which become amino acids and alcohol. It is reasonable to admit that because PBT is polyester and an ester, it will react and generate heat when it comes into contact with amine compounds. If the plastic part is forcibly pulled from the injection bonding template, the position of the polymer material is still attached to the surface of the alloy. Careful analysis of this surface by infrared absorption showed that the infrared absorption spectrum was consistent with that of amino acids. When heat is generated, the curing of the plasticized material that has not yet undergone condensation curing is delayed. We believe that it will cure after it enters the ultra-fine depression

we expect that PPS will be another material with similar potential in addition to PBT. We believe that halogen will remain at the end of PPS molecule. PPS is synthesized from dichlorobenzene, and this chlorine will be acidic. We assume that neutralization heat will occur when it comes into contact with amine compounds. We tested several commercial types of PPS. Different varieties have their own strengths and weaknesses, but they can be injection bonded. At present, we are not sure whether our theory about neutralization heat is correct, but the assumption about reaction heat seems to be correct

attractive results of evaluation test

if someone believes that the bonding between aluminum alloy and polymer is formed by adhesive, then in this case, the adhesive is injected into the polymer itself. Therefore, the bonding strength is considered to be related to the strength of the polymer itself. This assumption is confirmed by a series of tests: the shear fracture strength of the integrated object decreases with the increase of temperature, and the strength of the tested polymer decreases with the increase of temperature. PPS sandwich structure shows higher effect than PBT structure

Dacheng Plastic obtained a lot of evidence from these results. For example, PPS can be used at temperatures up to 200 ℃. We believe that if the adhesive has such high heat resistance, the object integrated with aluminum alloy should be able to withstand high temperature impact. The problem will be the difference between the linear expansion coefficient of aluminum alloy and polymer. The inherent problem is that the linear expansion coefficient of the molded part can be kept low by introducing the contents of glass fiber, but the proportion of polymer that has entered the nano aluminum depression is too small to accommodate glass fiber. It seems that because polymer is a kind of thermoplastic material with creep tendency, the bonding is very strong. Finally, we completed the thermal shock test in a long-span temperature range and compiled the results. We believe that the relatively strong bonding strength of PPS at 180 ℃ we observed is a hint of good resistance to temperature shock

we decided to conduct thermal shock test from -55 ℃ to +150 ℃, with a cycle of more than 3000 times

a sample of the test piece is removed and tested in sections. The analysis showed that the bonding strength of PPS did not decrease absolutely. The bonding surface is also surprisingly resistant to vibration

for PPS, the bonding strength did not change during the high temperature and high humidity test (85 ℃, humidity 85%, 1000 hours), hot water immersion test (70 ℃, 200 hours) and hot salt water immersion test (70 ℃, 200 hours). It is noted that in the two hot water immersion tests, the dividing line of the integrated sample corresponds to the special coating. Aluminum alloy is gradually corroded in such an environment, especially at the boundary position. The more aluminum alloy corrosion (oxidation) enters the interior of the bonding surface, the more severe it is. The coating protects the aluminum alloy from oxidation. PPS has a small water absorption coefficient, which also seems to have a positive impact

Figure 4: after two and a half years of development, Dacheng Plastic Company successfully developed the "nano molding technology (NMT)" that integrates

aluminum and plastics

we carried out joint research with polymer production in order to find the most suitable PPS varieties for injection bonding. Therefore, we hope to obtain composite materials that make injection molding easier and bring higher bonding strength. PBT is also being improved. We hope to obtain the same composite materials as PPS

provide durability and add decoration

aluminum alloy surfaces are usually subjected to treatments including electroplating, coating and chemical treatment. After t process, the surface of aluminum alloy becomes chemically active and sensitive to oxidation caused by high temperature, humidity and sunlight. The coating is easy to fall off and the adhesive is easy to be affected. Now let's take a closer look at electroplating and surface decoration

aluminum alloy and polymer materials appear to be firmly bonded, but if you look at the product more closely, you will see that there are micron sized cracks on the dividing line between polymer and aluminum alloy. The polymer melt on the boundary line did not get enough heat during injection, and the position along the boundary line was not bonded

electroplating involves two processes: alkaline etching and chemical polishing, which are designed to chemically strip the surface of aluminum alloy. In these two processes, aluminum is immersed in high temperature caustic concentrate or strong acid concentrate. Strong chemicals enter from the dividing line, which melts the aluminum alloy and reduces the bonding strength. To prevent this, the dividing line is coated and protected before oxidation. The coating used must be able to withstand these two processes. It took a year to find the right coating. This method is now used in electroplating integrated products with PBT. The above method is not required for products with PPS, because the ordinary electroplating process can be used

the painting of integrated products may cause problems in the adhesion of the paint layer. Both PBT and PPS are famous for these difficulties. We painted the integrated objects with various paints, and completed the rain resistance and UV test at 62 ℃ for 400 hours. We can find several kinds of paints that are OK

mobile electronic devices and components for other purposes

the production of integrated products for electronic circuit boards is increasing. The aluminum plate is extruded and integrated into the laptop shell, data camera shell and remote control shell. All the machines of polymer materials can not operate normally and are injected and bonded to these. The outside is electroplated and colored or painted, while the internal molded resin parts are scattered on the aluminum alloy like islands (Figure 5)

Figure 5: application example of nano molding technology

the possible use is a lightweight structure composed of aluminum rods or tubes. After assembly, this structure