Page 48 - 《橡塑技术与装备》英文版2026年1月

HINA R&P TECHNOLOGY AND EQUIPMENT

about good mechanical properties, but also makes amine chain extenders. By adjusting the ratio of soft
the polyurea coating prone to yellowing and aging and hard segments in components A and R, polyurea
under light exposure, and prone to self-oxidation materials with different elasticity, tensile strength,
to form quinone imine under ultraviolet light. and hardness can be prepared.
Therefore, antioxidants and UV-resistant components 1.3 Microphase separation structure of
are usually added to prolong its service life. polyurea elastomers
T h e A c o m p o n e n t o f a l i p h a t i c p o l y u r e a i s T he m ol e c ul a r c ha i n se gm e nt of pol yure a
prepared by prepolymerizing aliphatic diisocyanate elastomers is composed of alternating soft and hard
with amino-terminated polyether, while the R segments, forming an (AB)n-type block copolymer.
component consists of polyether and aliphatic amine The schematic diagram of its molecular chain
chain extenders, without the need for catalysts. The structure is shown in Figure 1. The microphase
second-generation polyurea exhibits excellent light structure has a significant impact on its thermal
resistance and low temperature resistance, and is properties, mechanical properties, and processing,
dense, seamless, waterproof, and corrosion-resistant, especially on the mechanical properties. The soft
making it suitable for outdoor settings where high segment with a lower glass transition temperature
color accuracy is required. The second-generation (Tg) is the basic phase, which has good flexibility.
polyurea reduces the reaction rate to some extent, The hard segment with a higher Tg forms a hard
b ut i t i s m e c ha ni c a l l y so f t a nd h a s po o r hi gh phase under the action of hydrogen bonding, which
temperature resistance. is rigid and can serve as a physical cross-linking
The third-generation aspartic polyurea achieves and reinforcing filler, significantly improving
slow reaction and tunable properties by introducing the physicochemical properties of polyurea. The
different substituents into aliphatic secondary differences in thermodynamic properties between
amine compounds with steric hindrance structures the soft and hard segments, as well as the complex
- polyaspartic ester molecules, while retaining interaction forces between the molecular chains,
excellent performance, thus solving the problem result in a complex multiphase system within them.
of difficult-to-control reaction speed. In addition, Within a certain range, the greater the degree of
weather-resistant aspartic polyurea has high solid microphase separation, the significantly enhanced
content and can achieve zero VOC emissions, making tensile strength, hardness, and modulus of polyurea.
it a high-performance, environmentally friendly, and Currently, the views on the factors affecting the
green elastomeric material. It is currently a research microphase separation structure of polyurea mainly
hotspot, but there are few varieties and high prices. focus on: 1. the composition of soft and hard
1.2 Synthesis of polyurea elastomers segments; 2. the effect of hydrogen bonding.
The synthesis of polyurea elastomers involves 1.3.1 Influence of soft and hard segments
two steps: prepolymerization and chain extension. In The structural types, chemical ratios, segment
the synthesis reaction of the prepolymer, component structures, and chain lengths of raw materials
A is generally a polymer, derivative, prepolymer, or a l l a ff e c t t h e m i c r o p h a se se p a r a t i o n st r u c t u r e
semi-prepolymer of isocyanate. of polyurea. When the content of hard segments
In the chain-extending synthesis reaction, the remains constant, the higher the molecular weight of
R component is generally composed of polyethers, soft segments, the greater the degree of microphase
amine chain extenders, and additives. The essence separation, resulting in increased tensile strength and
of the synthesis lies in the reaction between the impact strength, and significantly reduced hysteresis
prepolymer and the terminal amino polyether and and creep. Currently, diisocyanates or their trimers

·2· Vol.52，No.1