One of the main molding methods of thermoplastic plastics is calendering. The main processing method is that calendering machine would plasticize resin (plastic) and various additives, and filter out the impurities through Banbury machine and Open mill, and then produce the film or sheet through the gaps between two or more calendering rollers. You could adjust the calendering rollers’ gaps to control the thickness of the product. The product can be peeled from the calendering machine via the take-up roller or it can laminate with fabric directly on line. Finally, the calendering product will be given after being cooling down and shaped by cooling roller. Among the calendering technique, PVC material is the most common use.

PVC has always been the most important material for the calendering process. Using plasticizer can easily adjust the softness and hardness. A large amount of fillers, additives and lubricants can be added to improve the performance and lower the cost. But due to a large amount of plasticizer is added, it not only harms the health of operators in production line, but also emits VOCs (volatile organic compounds), which influences the air quality.

TPU is prosperous
Thermoplastic polyurethane elastomer (TPU) is a polymer material which co-reacts with polymerization of a diphenylmethane diisocyanate (MDI) containing an NCO functional group, a macro-polyol, and a chain extender. Its molecular structure is composed of a hard segment obtained by reacting diphenylmethane diisocyanate (MDI) with a chain extender and a soft segment obtained by reacting diphenylmethane diisocyanate (MDI) with a macro-polyol. Engineers can make TPU elastomers have excellent resilience and physical properties through different application and proportion of raw materials. With excellent mechanical properties in many ways, in recent years, TPU elastomers have gradually replaced PVC in pipe, cable, and conveyor industries.
 

In the past, TPU elastomers couldn’t be applied to calendering process and have been identified as the materials that are not suitable for calendering. The main reason is that the TPU process causes the machine to have large torque and easily damages the drive shaft, resulting in over load on equipment, and TPU would be sticky in plasticization process, causing adhesion phenomenon between the processing equipment and the conveyor belt. TPU processing range is narrow, which is unable to meet the open calendering method

Therefore, the TPU elastomer has been widely applied in extrusion, blow molding, casting, and injection molding processes. However, the application of TPU in the calendering process is rarely heard; it also limits the application of TPU in the field of calendering process.

The calendering process belongs to a multi-process continuous production process, which has the advantages of high production efficiency, large output, and on-line lamination. Although it is slightly more complicated than the other processes, once the production techniques are mastered, the productivity is the highest among all processes. It can reach 800~1000KG per hour, so the other processes are not able to compete with it.

In terms of plasticization, the components of the TPU are sufficiently sheared, mixed and melted by the strong shearing action in Banbury machine and the materials achieve uniform mixing and uniform temperature distribution. The open mill and the extruder are used to supply the plasticized material to the calendering machine through the transfer device, and, at the same time, it could have the effect of re-plasticization. In terms of calendering, the calendering is adjusted in a set temperature to press the TPU into a film or sheet into a pre-determined size, or TPU film or sheet can laminate with a base fabric to get a composite fabric product on line; in embossing, the embossing roller and the rubber roller co-work to obtain a certain pattern on the surface of the product, and in the end, the product would cool for shaping, and then cutting and winding are performed later on.

Through the improvement of TPU elastomer performance, the limitations of the past calendering process can be overcome. The biggest advantage of TPU elastomer through calendering process is that it can fulfill composite TPU materials. TPU composite material is using TPU film to laminate with various kinds of fabric to obtain a new composite fabric material characterized with both materials characteristics.

In the past, TPU composite fabrics were achieved by post-process, that is, the TPU films was first made, and then laminate with the fabric. In this method, the TPU film was mainly purchased from other suppliers and then coat the adhesive by the manufacturer. There’s the other on line process method. It means that the fabric is already coated with the adhesive (or without) and then the TPU film directly laminate with the fabric through calendering machine, manufacturing TPU composite materials or mesh and leather products.

Calendering TPU products are mainly used in synthetic leather (artificial leather). TPU film is mainly for life jacket, diving jacket, inflatable boat, tent, air mattress, airbag, and waterproof backpack; Synthetic leather / artificial leather is mainly for sofa seat, wall decoration, sports mat, luggage, car interior, and ship seat.

TPU calendering leather means the leather is made by calendering processing. Coating P. Materials Co has overcome the limitation of TPU materials, which can not only manufacture composite film products but also 100% eco-friendly leather products through calendering machine.

However, not every TPU elastomer can apply to calendering process, and not every calendering product can produce leather. The definitions of Calendering grade TPU for eco-friendly synthetic leather are as follows:

．The whole process of making leather shouldn’t damage the environment and be the burden to environmental pollution. 
．There is no poison and smell during process, and do no harm to human body in terminal application.
．Leather is bio-degradable, and can’t pollute the environment after decomposition.
 

For the new generation on the process of leather, it requires more eco-friendly, energy saving and environmentally friendly. It’s also recyclable and re-use orientated. And on the issue of eco-friendly leather, it has lots of solutions which can be as references in the markets.
 
Considering from price-performance ratio, between the investment cost in using the current calendering machine and the performance indicators with current maturity of TPU products, calendering grade TPU for eco-friendly synthetic leather is nothing but the best solution that can replace polluted process in the fastest way.

For synthetic leather/artificial leather pollution problems, Coating P. Materials has developed TPU calendering eco-friendly leather materials. The new calendering grade TPU can completely solve the environmental pollution problems and shortcomings of traditional PVC artificial leather/PU synthetic leather. Calendering eco-friendly leather from calendering grade TPU material has the advantage of environmentally friendly materials, friendly process, and high yield rate. It can replace PVC artificial leather / PU synthetic leather and completely compatible with PVC artificial leather machine to produce calendering TPU to increase the brand value.

Specifically, TPU is bio-degradable, and it won’t generate environmental pollution. Also, TPU is colorless, non-toxic, odorless and environmentally friendly materials. Calendering TPU leather has no VOC (volatile organic compound) emission problem. The process of calendering TPU leather does not use any organic solvent and plasticizer. Thus, TPU environmentally-friendly synthetic leather has no organic solvent residue problem (DMF, toluene, butanone), and the production process is environmentally friendly. The production process is environmentally friendly, so the amount of waste water and other generated waste are few (recyclable), and it is not harmful to the operators in production line. The physical properties of the TPU artificial leather such as abrasion resistance and scratch resistance are superior to the PVC artificial leather.

The application of TPU leather is wide. For instance, TPU artificial leather can replace PVC artificial leather and PU synthetic leather to be applied to luggage, shoes, wall decoration, sofa, car interior, etc. The process of TPU calendering leather can be the same as PVC artificial leather. Manufacturers do not have to invest in the cost of purchasing or renovating equipment. They can be produced directly from PVC artificial leather production equipment.

Calendering Grade TPU for eco-friendly synthetic leather has excellent physical property and wide product application. And it can completely follow PVC artificial leather machine to produce calendering TPU and go on industrial transformation and upgrading.