| Transparent polyamide is a kind of polyamide with high transmittance to visible light.It has the characteristics of low water absorption,good dimensional stability,excellent toughness and excellent transparency.In order to satisfy optical applications and obtain high transmittance polyamide,it is necessary to use more complex chain structure monomers to inhibit the crystallization ability of polyamide and reduce the crystal size smaller than the wavelength of visible light.In this paper,two kinds of transparent polyamide with similar chain structure were selected.Firstly,the optical properties,thermal properties,mechanical properties and the effects of chain structure on the properties of the two kinds of alicyclic transparent polyamides were systematically studied.The relationship between chain structure and properties was expected to be established.In practical applications,the processing temperature and the use of the two kinds of alicyclic transparent polyamides were discussed.Conditions have a great influence on the properties of transparent polyamide.The thermal treatment effect of transparent polyamide was studied in this paper.The changes of aggregate structure after heat treatment were recorded by X-ray diffraction and differential scanning calorimeter,and the tensile properties were compared.Based on the existence of homogeneous polycrystalline phenomena of transparent polyamide,in-situ research was carried out at last.The crystalline transformation of transparent polyamide under tensile field was studied.The relationship between thermal treatment of transparent polyamide and microstructure evolution and properties of materials under tensile field was established.To sum up,the specific research contents of this topic are divided into the following parts:1)Structure and Properties of Different Transparent Polyamides4,4'-diaminodicyclohexyl methane(PACM)and BIS(3-methyl-4-aminocyclohexyl)methane(MACM)based transparent polyamide were selected to analyze the chain structure information and thermal properties,and the differences of macroscopic mechanical properties and optical properties were compared.The results showed that the glass transition temperature of PACM-based transparent polyamide without methyl side group on the main chain aliphatic ring was lower,the crystallization rate was faster.It has cold crystallization during the heating process.The diffraction peaks related to the crystalline band appeared in the infrared spectra.It is not easy to crystallize during cooling.For MACM-based polyamide,with methyl side group on the main chain aliphatic ring,its glass transition temperature is 160 °C,much higher than the former.In the X-ray diffraction results,PACM-based transparent polyamide exhibited two diffraction peaks,which were similar to the alpha crystalline form of AABB-type polyamide,while MACM-based polyamide exhibited only one wider diffraction peak.In terms of comprehensive mechanical properties,PACM-based transparent polyamide is superior to MACM-based transparent polyamide.However,due to the weaker crystallinity of MACM-based transparent polyamide,its optical properties are excellent,and its transmittance is slightly higher than that of PACM-based transparent polyamide.2)Thermal Treatment Effect on Aggregate Structure and Tensile Properties of Transparent PolyamideWide angle X-ray diffraction(WAXD)and differential scanning calorimetry(DSC)were used to study the effect of heat treatment on the structure of transparent polyamides with different chain structures.The results show that annealing treatment can promote the cold crystallization behavior of PAPACM12.The cold crystallization process improves faster with the increase of temperature,but the overall crystallinity and lamellar thickness will not change.The aggregated structure of PAMACM12 will not change significantly after annealing treatment.Conventional hot-pressing treatment will result in the orderly arrangement of some molecular chains in the transparent polyamide,and the melting point of the material will appear.During the cooling process,the crystallization rate of transparent polyamide is low,and no obvious crystallization peak will appear.Annealing treatment has a great effect on the tensile properties of transparent polyamide films.3)In-situ Synchrotron Radiation Study on Microstructure Evolution of Transparent Polyamide under External Tensile and Temperature FieldIn-situ wide-angle X-ray diffraction and in-situ small-angle X-ray scattering(in-situ WAXD/SAXS)were used to study the morphological changes of PAPACM12 during heating.In addition,the morphological transformation of PAPACM12 films during tensile process was also studied.WAXD results show that PAPACM12 can form crystalline structure similar to AABB-type polyamide in cold crystallization temperature range,but the diffraction peaks of PAPACM12 are more complex.Because of the aliphatic ring structure in the main chain,the interfacial spacing of PAPACM12 is larger than that of ordinary polyamide.The WAXD results of tensile process show that the microstructure of PAPACM12 is destroyed during tensile process,the diffraction peaks corresponding to the alpha crystalline form disappear gradually,and the transformation from the alpha crystalline form to the gamma crystalline form occurs.However,no long period information was observed in the SAXS results,indicating that the crystal size of PAPACM12 is very small,which is also the reason why PAPACM12 has very high transmittance.In summary,the differences in molecular structure between PAPACM12 and PAMACM12,the effect of thermal treatment on the aggregation structure and tensile properties,the microstructure evolution of PAPACM12 under temperature field and the transformation of the crystal structure of PAPACM12 under external tensile field were studied.It was revealed that the molecular chain structure affected the crystallinity of PAPACM12,and proceed to the next step,can affect optical properties,mechanical properties and molecular mechanism of structural evolution. |
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