The Preparation Of Polyethylene-based Composites And Study On Their Gas Barrier Properties And Mechanical Properties

As an important thermoplastic resin,polyethylene(PE)is widely used in food,medical,electronic appliances,and new energy due to its advantages of low price and good molding and processing properties.However,compared with engineering plastics such as polyamide(PA)and polycarbonate(PC),polyethylene has problems such as heat resistance,poor weather resistance,and easy penetration of non-polar gas molecules,which limit its application.This research work is mainly aimed at the application of high-density polyethylene(HDPE)in the lining material of type ? high-pressure hydrogen storage cylinders for new energy vehicles.By physical and chemical modification to enhance the gas barrier properties of the material,the melt blending method introduces two-dimensional layered nano-particle montmorillonite or gas barrier resin nylon 6 into the HDPE resin matrix to prepare a polyethylene-based composite material with excellent mechanical properties and high gas barrier properties,which provides technical support for plastic lining of type ? highpressure hydrogen storage bottle.Firstly,by means of ion intercalation,Na-MMT was modified to prepare organic montmorillonite(OMMT)by using long-chain quaternary ammonium salt,and the effects of temperature,pH and other conditions on ion replacement were studied.The results show that when the amount of modifier is 10.5mmol,the ion intercalation effect is the best.Among them,the interlayer spacing of modified montmorillonite is increased from 1.245nm to 3.276nm,and the contact angle with water is increased from 70.2° to 108.1°,The hydrophilic and oleophobicity of the surface is obviously improved,and the modified montmorillonite structure becomes loose,thereby preparing organic montmorillonite with high-level spacing,low surface energy and good compatibility with high-density polyethylene and facilitate its dispersion in the HDPE matrix.Secondly,the prepared modified montmorillonite(S-OMMT)and highdensity polyethylene are melt blended to prepare composite materials.As a result,it was found that S-OMMT was further peeled off by the polyethylene molecular chain in the HDPE resin matrix,which improved its dispersion in the matrix.The introduction of S-OMMT also improves the mechanical strength and gas barrier properties of HDPE.When its dosage is 5 wt%,HDPE/SOMMT composites have the best mechanical strength and barrier performance,and the tensile strength is increased by 42.1%compared with HDPE.The minimum gas permeability coefficient is 2.31 ×10-14 cm3·cm/(cm2·s·Pa),which was 34.4%lower than that of HDPE.Finally,the barrier resin nylon 6 was introduced into the high density polyethylene resin matrix by melt blending method,and the compatibility between the two was improved by using PE-MAH as compatibilizer,so as to prepare the blend polymer.The results showed that the compatilizer(PE-MAH)had a good effect,which reduced the size of nylon 6 and made it distributed uniformly in the HDPE resin matrix in the form of sub-continuous phase,enhanced the mechanical strength of the polymer blend,extended the diffusion path of gas molecules in the polymer material,and reduced the gas permeability.When the dosage of PE-MAH was 10 wt%,the tensile strength of the polymer was increased by 36.3%from 26.54MPa to 32.18MPa,and the gas permeability coefficient was the minimum of 2.1×10-14cm3·cm/(cm2·s·Pa),which was 37.7%lower than that of HDPE.