Preparation And Properties Of Graphene/Thermoplastic Polyurethane Composites

Composite materials are multi-phase solid materials,which are composed of two or more kinds of substances which have different physical and chemical properties.For polymer nanocomposites,polymers act as matrixes and nanomaterials as fillers.Thermoplastic polyurethane(TPU)is one of the most important polymer materials which has been widely applicated in aerospace,packaging,biomedicine,etc..TPU has both rubbery elasticity and easy processability,and the raw materials for the synthesis of TPU are available and cheap.The molecular structure of TPU is controlable;besides,TPU has a good compatibility wih the human body,and is biodegradable,which make it an environmental friendly material.TPU also has some other advantages:it detains high elastic deformations,can operate over a broad range of temperatures,not to mention that it is light and inexpensive.As a result,TPU becomes an important shape memory material with a great potential of applicating in intelligent materials area.At present,the researches on TPU throughout the world mainly focus on improving TPU’s performances by fabricating nano-materials/TPU composites,with the aim to broad the application field of TPU.Graphene is a new type of nano-materials.It has been widely used as a functional filler for making composites by adding it into the polymer matrix due to its excellent performance,to achieve the purpose of strengthening the polymer matrix.In this paper,the mechanical properties,thermal properties and shape memory properties of TPU were improved by using graphene and other materials synergistically.The full text was divided into four parts:In the first part,we firstly prepared polyvinyl alcohol/graphene oxide(GO-PVA)hybrid material,then GO-PVA/TPU composites were fabricated by melt blending method.DSC testing results showed that the addition of GO-PVA increased the crystallization temperature of GO-PVA/TPU composites,when GO-PVA content is 4 wt.%,the crystallization temperature of GO-PVA/TPU composites is 28.8℃ higher than that of pure TPU.Tensile and shape memory testing results showed that the tensile stress at definite elongation and shape fixing rate of GO-PVA/TPU composites increased with the increasing of GO-PVA content,while shape fixing rate decreased continuously.But when the recovery temperature improved,the shape recovery rate of GO-PVA/TPU composites increased.In the second part,we firstly prepared the nano-SiO2/GO hybrid materials(GO-g-nano-SiO2),then the GO-g-nano-SiO2/TPU composites were fabricated by melt compounding method.FTIR and XRD showed that GO and nano-SiO2 were strongly interacted with each other,and there was also strong interfacial interaction between GO-g-nano-SiO2 and TPU.DSC testing results showed that the crystallization temperature of GO-g-nano-SiO2/TPU composites increased when compared to pure TPU.When GO-g-nano-SiO2 content is 1 wt.%,the crystallization temperature of GO-g-nano-SiO2/TPU composites increased by 44 ℃.The addition of GO-g-nano-SiO2 enhanced the tensile stress at definite elongation and the shape fixing rate of GO-g-nano-SiO2/TPU composites.When the content of GO-g-nano-SiO2 is 1 wt.%and the mass ratio of GO:nano-SiO2 is 1:4,the mechanical and shape memory properties of GO-g-nano-SiO2/TPU composites were the best among all the samples.In the third part,the montmorillonite/graphene hybrid material(MMT-GO)was firstly prepared and the MMT-GO/TPU composites were then prepared by melt blending method.FTIR and XRD tests showed that the presence of MMT promotes GO’s exfoliation,and a hydrogen bonding linkage between GO and MMT is exited.TG testing results showed that the thermal stability of MMT/TPU composites at high temperatures is relatively good.Tensile and shape memory tests showed that the effects of MMT and GO synergistically enhancing TPU are better than MMT or GO alone doing the same thing.And MMT-GO effectively enhanced the shape fixing rate of TPU.Considering the results of tensile and shape memory tests,when the mass ratio of MMT:GO is 1:2 and the dosage of MMT-GO in TPU is 0.25 wt.%,the composites showed the best performance.In the fourth part,PVDF/TPU and GO/PVDF/TPU composites were prepared by melt blending method.FTIR and XRD tests showed that a hydrogen bonding linkage had been formed between GO and PVDF,which makes PVDF disperse well in the TPU matrix and promotes the crystallization of TPU.SEM testing results showed that there had formed a relatively good interaction between GO、PVDF and TPU.Tensile and shape memory testing results showed that the tensile stress of PVDF/TPU composites increased,shape fixing rate of PVDF/TPU composites was improved while shape recovery rate decreased compared to pure TPU.GO and PVDF synergistically enhanced TPU effectively,the shape fixing rates of GO/PVDF/TPU composites were relatively higher than that of the pure TPU,while the shape recovery rates were lower.