All kinds of spun-melt non-woven raw materials are "thermoplastic" plastics. Thermoplasticity refers to the characteristics of plastic that can be repeatedly heated and softened in a specific temperature range and hardened after cooling. All kinds of raw materials used in spun-bond and melt brown non-woven production processes are solid in normal temperature, sometimes referred to as "chips" or "resin". When adopted different raw materials, the characteristics of the product will be different, the production process will be different, and the performance and configuration of equipment will be different, which will have a significant impact on products’ usage, market, economic benefits and the price of the production line. Therefore, raw material is the first prerequisite to determine the performance index of the production line.
The main raw materials of Spun-Melt Non-woven manufacturing technique are：polypropylene（PP）、polyethylene（PE）、polyethylene terephthalat
（PET）、polyamide（PA）、polyurethane（PU）、Polylactic acid （PLA）and so on. Polypropylene. (PP) is one of the most commonly used, the largest amount, the most widely used raw material. The following is introducing the characteristics of PP and the requirements of spinning and melting production line for PP chips material.
Polypropylene is the commonly used raw material and the most important raw material of polymer fiber at present. In China nearly 94% of spun-bond and melt brown non-woven raw materials are polypropylene. In the fields of medical treatment hygiene and health care, the application amount of polypropylene non-woven fabric accounts for 50% of the total non-woven fabric.
Features Of Polypropylene（PP）
Polypropylene fibers have very low density（0.91g/cm3）；Lower moisture content（ ＜0.1%,）；Good chemical resistance（Acid, base, solvent）；Anti-mildew、Corrosion protection、moth-proofing、antibacterial；Good thermal insulation, thermal insulation, insulation performance；High stiffness、Good tensile strength（4.5～7.5cN/dtex）；Good fatigue,Good wear resistance; Temperature resistance is 120℃、Melting point is 165℃；easy for regeneration and so on. These properties make polypropylene fiber have two major differences with other synthetic fibers:The first is that its hygroscopicity is very low, which makes the polypropylene fiber has excellent dirt resistance and almost the same dry and wet characteristics; Secondly, it has the lowest density of all fibers, which makes it have good coverage under the same weight condition.Secondly, it has the lowest density of all fibers, which makes it have good coverage under the same weight condition.
Because the thermal conductivity of polypropylene is the lowest, its heat preservation effect is better than wool, and its fiber not only has a lower density, but also has a larger coverage area, which can be used as home and car interior decoration filler, thermal flocculation material and sound absorption, heat insulation materials.
On the other hand, polypropylene does not react with general chemical reagents, has strong chemical resistance, polypropylene non-woven cloth can be used to manufacture geotextiles, lead battery diaphragm, filtration materials. Due to the absence of active groups in the main chain of polypropylene fine denier fiber, the material itself is not easy to be eroded by bacteria and molds, and there is no irritation or toxicity in contact with human skin. It has good hygienic performance, so it can be widely used in the field of medical and health care. In addition, the oleophilic chain structure of polypropylene and the internal capillarity structure formed due to the crystal transformation in the post-fiber stretching, resulting in its products with strong oil absorption, can produce oil absorption felt material.
The requirements for spun-melt raw materials PP chips
In the process of polypropylene spinning, different types of chips are usually used.Its spinnability can have bigger difference.Such as the length of cycle used in the spinneret component, the generation rate of broken wire, fiber evenness is different.However, if it can be used as the raw material of spinning grade polypropylene (PP) chip for spinning and melting production, it shall meet the following conditions:
Melt brown 400～1500g/10min。
（2）Width of molecular weight distribution（Mw/Mn）：＜4～5。
（3）Melting point：164～170℃（isotactic polypropyleneMelting point is176℃）。
（8）Smooth appearance, uniform grain size, no granular phenomenon
The raw materials used in the production line are related to the market positioning and usage of the products. In order to reduce the production cost, inferior raw materials can be selected for low-end market products due to the low requirements for raw materials. However, high-end products require higher performance of raw materials, so they need to choose high-quality raw materials with higher prices. The price of PP chips is directly related to the size of MFI. Generally, the higher the MFI is the higher the price will be. Therefore, it is necessary to comprehensively consider the production process, equipment characteristics, product use, product sales price, production cost and other factors to choose the raw materials.