The ‘bonding’ or ‘welding’ technology can be claimed to be the biggest revolution in the garment industry, only next to the industrial sewing machines. The bonding application today is not simply related to ‘buying the right machine’ for the ‘right product’, but to a synergy which involves suppliers of fabrics, trimmings and adhesive glue.
The range of application of this technology is endless and goes from intimate to active-wear (or so-called functional garments), to denims, shoes, furniture, car seats or even caps, hoods, backpacks and bicycle saddle pads. MACPI, a leading solution provider of cutting and finishing machines, has teamed up with specialised companies such as BEMIS, USA (adhesive film manufacturer), PIONEER ELASTIC, Hong Kong, and EUROJERSEY, Italy (fabrics) to offer complete bonding application solutions to the industry. Mosso Luca, Managing Director, Macpi Group Hong Kong, discusses the technology in detail.
Various factors come into play when finding the right equation for bonding. A common knowledge is that an adhesive is activated at a certain temperature by an electric heated plate or hot air. Another aspect to be kept in mind is thickness of the glue. For example, an adhesive glue bonded in bras or panties cannot be used to assemble a denim trouser since the fabric thickness and its stretching performance are totally different and so the quantity required for denim would be higher. So the first thing to be evaluated is the fabric and its weight. Fabrics have mainly two limitations, the major being the silicone treatment given to some fabrics. The silicone (water repellent) finish makes it difficult for the bonding process due to its chemical property not matching to that of glue.
Another problem that could be faced during the process is the fabric on which bonding has to be done. For example, polypropylene is a synthetic fabric that literally collapses at 100 degrees centigrade, whereas the existing glues available in the market today melt at 130 degrees centigrade. Therefore any fabric that has to undergo bonding must withstand a minimum temperature of 180 degrees centigrade. A standard washing test for bonded intimate garments is 25 cycles at 30 degrees. Even severe tests for the dyeing process and stone washing have shown that delamination does not occur in the garments.
The second point to be considered is the area that has to be bonded. As example, a bra cup has a totally different performance compared to a bra wing or panty waist, which has to stretch and, at the same time, provide support; in such a case the selection of the elastic and adhesive is really important to avoid either stiff or loose edges. Although, traditionally stitching was done in these areas, but now the bonding application is fast gaining popularity. When an elastic is sewn to the garment, the stitches hamper its stretchability after a certain point. However, tests have shown that a bonded seam has high stretchability, so much so that one reaches the point where the fabric can rip, but not the seam.
Strength of the seam after bonding is much higher than a traditional stitch, which cannot be compared to an ultrasonic bonded seam. Then again, in the case of ultrasonics, the seam can easily open if it is not covered by a tape. In fact, an ultrasonic seam is always protected and reinforced by a tape, commonly called a seam tape.
During bonding, the machine applies a maximum pressure of 0.8 – 1 kg, which is generally enough for accurate bonding (fusing) of the two panels of fabrics, through a bonding press or an automatic carousel. Usually, the seam strength of a bonded seam or panel can be tested using a dynameter and is expressed in kg. This strength varies as per the fabric. For example, the seam strength of a stretch fabric can go up to 3 kg, while that of denim can exceed 4 kg.
Machines for Bonding Applications
MACPI has developed a wide range of machines suitable for bonding technology such as bonding press and carousel with different available shapes, belt fusing machines and edge bending machines.
The 335.02 Electropneumatic machine for fabric bonding is used for attaching textile adhesive tape band. It has an upper and lower heating system for fusing of the adhesive through independent temperature adjustment. A cooling system cools the binded edge during its outlet from the machine. This machine is fitted with a lighting lamp at the cutting area and can easily cut an already shaped panel (or tubular seamless garments) and bind the edge at the same time with a textile adhesive tape band.
The working process is quite similar for all versions equipped with the lamination device 903. The adhesive film is first transferred on the elastic/tape through a plate fitted on the 903 lamination device. The adhesive is initially just tacked on the elastic so as to prevent any crystallisation. Next, the operator sets the required tension, depending upon the area of application such as leg opening or waistband, with the help of a tensioning device; he can set any tension (9 per each program) based on the application. Finally, the elastic is applied on the garment using a folder or a hot chute and then trimmed in order to obtain a clean edge.
The Macpi 507.37-9125 bonding machine comes with a special utility shape (1500 x 500 mm) and is popularly used for bra fusing. The machine has two 1800 rotating bucks and one head with vertical movement complete with an electrically heated head covered by fluorglass fabric and offers double vacuum with a variable flow. Technical features include electronic adjustment of the temperature, a PT4 programmer, an increased and adjustable pressing pressure and a safety device for machine rotation.
The operator can load the parts to be bonded on the bottom plate and rotate it. The upper electric heated plate, designed with new heating elements, comes down till the two are completely closed. The vacuum level automatically falls up to zero. The vacuum helps to hold the parts in place during rotation, and then to cool down the bonded piece once the cycle is completed.
The MACPI R&D team is constantly working closely with brands such as Victoria’s Secret, Triumph International and Nike to develop new applications of the bonding technology for their products in intimate or sportswear (active wear) garments. The company established last June a large laboratory in Hong Kong where customers were free to use the bonding machines and equipment for their own tests, and consequently set up another facility in Colombo (Sri Lanka) in order to cater to the growing demand from the Indian subcontinent.
Different ways can be selected to obtain total stitch-free edges
CASE A – EDGE BINDING
Sky blue – fabric; Green – elastic; Red – adhesive !
In this case a V-FOLD elastic (or Y-FOLD) is applied on the garment. The adhesive film (red) is laminated on the elastic by same machine just before the binding operation.
Since the glue is partially covering the elastic, the edge will remain soft.
One of the advantages is the possibility to use fabrics which may fray.
CASE B – EDGE LAYDOWN
In this case the elastic/tape is applied on one side only and the fabric edge can also be trimmed.
The adhesive glue (red) is laminated on the elastic by the same machine before the lay-down operation.
Even in this case the glue can totally or partially cover the elastic in order to increase or decrease the stretchability of the edge itself.
CASE C – EDGE FOLD OVER
In this case the edge is folded with a single lay of adhesive film or with an elastic laminated on both sides in order to obtain a complete stitch-free hem.
The solution to bond an elastic which is laminated on both sides provides an excellent result in terms of stretching performance.
Bonding: Versatile Applications, But With Expert Handling
Gokaldas Images, one of India’s largest integrated clothing corporations and a leader in garment manufacturing, offers a wide range of products including knitwear, lingerie, sportswear, denim and woven garments, besides tailored suits and dresses. Shakti Prasad, Manager Quality, shares his experience of bonding technology on the production floor.
SW: For what kind of products do you use bonding applications? In which areas (seams) of a product is this application used?
SHAKTI PRASAD : Bonding is decided as per the style requirements and its end use. Usually details such as an area where bonding is to be done is predetermined by the buyer. For example, in trousers or bottom lines, bonding is required at the waist band, waist band facing, fly J-stitch and fly facing belt loop, pocket welt and pocket facing. If it is tops, then bonding is required at the collar, neckband, front placket and pocket flap.
SW: Different fabrics require different viscosity of glue. What kind of glue do you use and are these easily available in the market?
SHAKTI PRASAD : Our Company uses a special type of glue, which melts at 150 degree centigrade. For higher end we use KF-240 while for the lower end we use TP-2052 or tricot. We can easily procure them from the market.
SW: What are the limitations or problem areas of bonding application faced on the production floor?
SHAKTI PRASAD : Machine knowledge is essential for the operator performing the bonding application. Knowledge of how to set the machine line temperature, pressure and speed is required for bonding to be done properly. In addition, he has to take precautions while feeding the material to be fused. For example, the operator has to arrange the parts that are placed on the large paper sheet properly to get a clean finish. If the bonding is not set or done properly, then bubbling problem occurs.
Moreover, if the machine belt is not cleaned properly, then the glue sets on the parts, which is very difficult to remove. To ensure that proper bonding has been done, we also perform regular tests at our in-house facility. To check the seam strength, we do the tearing test; and to check the bonding strength, we use spring balance.