The spandex yarn is very popular in textile industry and most of it is made from polyurethaneurea polymer.
In this work, the viscosity and molecular weight increase of polyurethaneurea
solution was studied in a view of temperature, raw materials and others. In addition, the phase separation and physical properties of spandex yarn were also studied from hydrogen bonding of urethane and urea group.
The polyurethaneurea was made from the reaction of prepolymer and amines(EDA, PDA as chain extender / DEA as chain terminator), and prepolymer from PTMG of molecular weight of 1800 and pure MDI.
The viscosity increase of polymer solution in storage process was come from not only chemical reaction of transamidation but also physical force of hydrogen bonding.
And, the yarn properties and viscosity of dope were influenced by capping ratio of prepolymer, the kind of chain extender, solid contents of polymer solution and tri-amine contents in chain extender.
The phase separation of hard segment and soft segment in polyurethaneurea of spandex yarn is very important in yarn properties, especially modulus and elongation.
According to IR study, the degree of phase separation of yarn was measured by the absorption peak of free C=O and hydrogen bonded C=O of urethane. The phase separation was increased by increasing temperature. But, the force of hadrogen bond was decreased.
The properties of spandex yarn were measured after heat treatment both in relaxed state and stretched state. After heat treatment in relaxed state, modulus was decreased and elongation was increased by increasing temperature because of good phase separation of hard segment and soft segment. But in 150% stretched state, the properties were opposite because of poor phase separation which come from moving of hard segment at partially oriented state during pre-stretching.
Several kinds of yarns were made in dry spinning process by changing spinning conditions. The modulus increased and elongation decreased when lower spinning temperature, higher spinning speed and higher draft ratio beacuse of poor phase separation.