| Because of the higher heat resistance than that of the polyvinyl chloride andpolyethylene, crosslinked polyethylene materials are often used as protective sleeve ofinsulation cable. It can be use for a long time under90℃, and has good electricalproperties and environmental stress cracking resistance. As a result, most of polyvinylchloride and polyethylene cable at home and abroad has been replaced by thecrosslinking polyethylene cable. Howerve, due to the low oxygen index ofcrosslinking polyethylene, fire accident is easily to occur in use.Nowdays, in order to improve the safety level and reduce the fire damage to human,the flame retardant performance of the materials has become one of the importantindicators in choosing polymers. Advanced flame retardant performance and fireprevention technology will provide effective protection on people’s life property aswell as environmental pollution.Due to its less dosage, moderate price and good flame-retardant property, many ofthe halogenous flame retardant has been very popular in the market. But thehalogenous flame retardant will generate dense toxic smoke and corrosive gas in fire,it will do harm to environment and firemen. From this point of view, to preparation ofa kind of low cost, halogen-free, environmental friendly flame-retardant crosslinkedpolyethylene has become a development direction.This thesis consists of four parts:The first part: ReviewsIn this section, the situation of the situation of the application and the modificationof low density polyethylene,, the classification and the mechanism of physicaladditives, the type of the crosslinking agent, as well as the application of palygorskiteclay was introduce, and the significance of this topic was argued.The second part: Preparation and characterization of palygorskite clay-basedcrosslinking agentPalygorskite clay-based crosslinker (OPGS) was prepared, and was determined by infrared (FT-IR), XRD, scanning electron microscopy (SEM) and curface properties.Some of the results were obatined as belows.1. The matching of solvent, as well as the amount of silane crosslinking agentshowed obvious effect on the grafting degree of OPGS. When the dosage of mixedsolvent of ethanol and water is100mL (9/1, w/w), the dosage of the silane couplingagent is15mL, the highest graft degree of OPGS with the value of0.2747mmol/gwas reached.2. Crystal structure of the modified palygorskite clay showed no change, itindicated that the grafting reaction occurs at the surface of the rod-like structure ofpalygorskite.3. By the scattering test of OPGS in different solvents, a obvious dispersitydecreasing of OPGS was found in water and it improve lipophilicity.The third part: Preparation of new crosslinked low density polyethylene compositematerialsThrough the mechanical analysis of crosslinked low density polyethylene madefrom OPGS and trimethoxy vinyl silane (YDH-171), we drawn the followingconclusions:1. The adding of the crosslinking OPGS greatly reduced the holes on the surfaceof low density polyethylene material itself. It made the material surface smoother. Itwas due to the closer bonding of the materials through the addition of OPGS, and thelater, which would increasse the compatibility of the compisit.2. Through the thermogravimetric analysis of OPGS crosslinked low densitypolyethylene, YDH-171crosslinked low density polyethylene and OPGS/YDH-171crosslinked low density polyethylene, it found that the decomposition temperature andthe quantity of carbon-produing of OPGS/YDH-171crosslinked low densitypolyethylene is highest.3By the comparison the performance of OPGS crosslinked low densitypolyethylene and the crosslinked low density polyethylene, it was found that no bettermechanical properties was found when OPGS was singlely added refering to that ofthe addition of YDH-171at a same amount of crosslinking agent. But if the two crosslinking agent were mixed, it is found that a better mechanical properties as wellas a higher gel content of the composit obtained than the singlely adding of YDH-171.On the other side, the cost of crosslinked polyethylene materials would decreasebecaous of the low price of OPGS.The fourth part: Preparation and characterization of potato waste-based activatedcarbon sludge/dimethyl methyl phosphonate flame retardant crosslinked polyethylenecompositesMLS/DMMP flame retardant crosslinked polyethylene composites wereprepared, and were characterizd of the materials through oxygen index, mechanicalproperties and thermodynamic properties, and the following conclusions weresummarized:1.The flame retardant crosslinked polyethylene was prepared throughone-component and mixing methods, and a higher oxygen index obtained through theaddition of MLS and DMMP than that of the one-component system. It suggested thatthese two kinds of flame retardant have synergistic flame retardant effect. When thetotal amount of MLS and DMMP was45g at a ratio of2:1(w/w), the highest oxygenindex reached30.2%.2. Through the characterization of thermodynamic properties of the composite, itwas found that when the total amount of flame retardants was35g, the ratio ofMLS/DMMP was2/1, a most excellent performance was obtained, including thetensile strength of9.4MPa, the elasticity modulus of65.1MPa, the elongation atbreak of495.42%. At the same time, the decomposition temperature of the flameretardant crosslinked polyethylene composite material reached462℃, which wassignificantly higher than the that of the low density polyethylene (42℃high than thatof low density polyethylene). It suggested a significantly improve of heat-resistingperformance of the material derived from the flame retardant.3. Overall consideration, at a total amount of flame retardant of35g and a ratio of2/1of MLS/DMMP, the prepared flame-retardant composit bore the most excellentthermodynamics properties. |
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