Shanghai Daoqin Plastics Co., Ltd.

        HDPE pipe/tube has many excellent property can, light, resistant 腐, inner light slip, use lifespan long and other, also its relatively high strong/high degree application in pressure various pipeline upper, its ring force cracking property can relatively 差, HDPE pipeline in long negative function lower and time rear 会出现应 force loss phenomenon.

          1.1 cooling speed degree effect/influence

         temperature degree is HDPE crystallization process in most factors, different crystallization degree for pipe/tube force property can has relatively large effect/influence. certain 厂HDPE tube/pipe in water cold true 空定径箱 in molding, tube/pipe 壁断面 has different hot history, different hot history for HDPE has different crystallization is 阅, formed different crystallization degree poly structure. pipe/tube outer table/sheet water cooling can very fast most crystallization temperature degree, formed crystallization degree relatively low poly structure 区. outer table/sheet and in has can obtain 晶核数 amount and long speed rate most has crystallization 层, this 区域晶体生 long good, poly structure stability. if this control good water temperature and versus 应 牵引 speed degree, can increase thick degree. 因HDPE hot slow, most crystallization temperature degree in in and inner 层停留 time relatively long, crystallization can in separation conditions lower 进行, to is amount relatively less, pellets relatively large poly structure 区域. this type of inner outer structure non-uniform property for pipe/tube force property can effect/influence relatively large, low crystallization make pipe/tube tool has tough property, high crystallization tool has rigid property, crystallization degree increase, property increase large. pressure to 2/3时 inner surface cracks;继续 pressure 扁, cracks toward outer surface expand 展. 我们认 is use density high homopolymer extrusion molding pipe/tube more attention/notes molding process.

          1.2 熔 melt temperature degree effect/influence

         molding in melt temperature degree and in temperature degree lower time effect/influence 残存晶核 数 amount, 晶核 存 in and and large small, for molding crystallization speed degree has very large effect/influence. if melt temperature degree low, melt time short, 残核没 has to bad, molding 时晶核 crystallization speed degree fast, dimensions large small uniform, can formed relatively stability poly structure; if melt temperature degree high, melt time long, has structure bad more, 残余 晶核就越 less, formed time long, crystallization speed degree slow, crystallization dimensions large, structure unstable, from effect/influence pipe/tube strong/high degree. melt temperature degree relatively high, force cracking time very short. 我们曾 use preheating time long, preheating temperature degree relatively high machine inner melt molding pipe/tube short water pressure strong/high degree experiment/testing, its time has 4.3h. melt temperature degree for HDPE molding melt 破裂也 has relatively large effect/influence. molding melt to 剪切应 force, 当剪切应 force to or ultra- certain 一临界 value 时, melt 就会出现破裂. melt temperature degree different, for 应 剪切 speed rate large same. is ensure pipe/tube force property can, molding need control good molding temperature degree, amount melt 破裂.

          1.3 牵引 speed degree effect/influence

         in pipe/tube molding process in, melt extrusion speed degree and pipe/tube speed degree versus 协调. if speed degree large extrusion speed degree, separation large separation 子顺 牵引 direction orientation, in force function lower, elastic property also has 回复就 by cooling type, especially is in already 定 情况 lower, adjustment speed degree processing thin tube/pipe, this pipe/tube more easy in direction upper generate cracks.