成年奭片免费观看视频天天看,久久国产精品99久久久久久口爆,99re久久精品国产,高中国产开嫩苞实拍视频在线观看

        發(fā)泡料經(jīng)過(guò)經(jīng)過(guò)聚氨酯高壓發(fā)泡機(jī)混合注入保溫腔體或殼體夾層，在未固化前須流經(jīng)相當(dāng)長(zhǎng)的距離才能充滿，充滿后整個(gè)泡沫的密度、孔結(jié)構(gòu)、強(qiáng)度及導(dǎo)熱系數(shù)的分布有顯著差異，存在明顯的梯度。流動(dòng)性就是表征發(fā)泡體系在發(fā)泡過(guò)程中克服阻力均勻充滿各種復(fù)雜保溫腔體或殼體夾層的能力。從本質(zhì)講，聚氨酯發(fā)泡是一個(gè)復(fù)雜的物理和化學(xué)過(guò)程，幾乎同時(shí)發(fā)生著鏈增長(zhǎng)、發(fā)泡及交鏈三類基本反應(yīng)。反應(yīng)初期(乳白期)主要是線形分子的鏈增長(zhǎng)，反應(yīng)熱少，有少量發(fā)泡氣體的產(chǎn)生或汽化，此時(shí)料液起發(fā)產(chǎn)生微小膨脹，同時(shí)由于粘度較小料液產(chǎn)生物理流動(dòng)，故表現(xiàn)出一定程度的流動(dòng)性，但不十分顯著;隨著反應(yīng)的繼續(xù)，放熱量進(jìn)一步增大，大量發(fā)泡劑的汽化引起泡沫體的急劇膨脹(發(fā)泡期)，此時(shí)泡沫的膨脹所引發(fā)流動(dòng)充滿大部分腔體;當(dāng)出現(xiàn)凝膠也就是大分子開(kāi)始交鏈(固化期)時(shí)，發(fā)泡體系粘度的陡然增加使泡沫與腔壁摩擦增大，雖然在內(nèi)壓的作鏈(固化期)時(shí)，發(fā)泡體系粘度的陡然增加使泡沫與腔壁摩擦增大，雖然在內(nèi)壓的作用下輕微膨脹，但邊界效應(yīng)使得泡沫體的泡孔拉伸變形，呈現(xiàn)強(qiáng)烈的各向異性，這一段泡沫體因此也極易收縮變形。

        廣東弗雷特機(jī)電科技有限公司位于廣東省中山市南頭鎮(zhèn)升輝北工業(yè)區(qū)，是一家集研發(fā)、生產(chǎn)、銷售、售后服務(wù)于一體的聚氨酯機(jī)械自動(dòng)化生產(chǎn)型企業(yè)。我司研發(fā)制造各類聚氨酯澆注機(jī)、聚氨酯發(fā)泡機(jī)、自動(dòng)化發(fā)泡生產(chǎn)線（懸掛發(fā)泡線/地軌發(fā)泡線/轉(zhuǎn)盤線等）、自動(dòng)化發(fā)泡模具模架、機(jī)械臂等聚氨酯成套發(fā)泡設(shè)備，幫助上千家聚氨酯制品生產(chǎn)型企業(yè)用戶達(dá)到“制品優(yōu)良率高，設(shè)備故障率低”。

Do you know the basic process of polyurethane foaming in refrigerators?

The foaming material is mixed and injected into the insulation cavity or shell interlayer through a polyurethane high-pressure foaming machine. Before it is cured, it must flow for a long distance to be filled. After filling, the density, pore structure, strength and thermal conductivity of the entire foam are distributed. There is a significant difference, there is a clear gradient. Fluidity is to characterize the ability of the foaming system to overcome the resistance and evenly fill various complex thermal insulation cavities or shell interlayers during the foaming process. Essentially, polyurethane foaming is a complex physical and chemical process, and three basic reactions of chain growth, foaming and cross-linking occur almost simultaneously. The initial stage of the reaction (milk white stage) is mainly the chain growth of linear molecules, the reaction heat is small, and a small amount of foaming gas is generated or vaporized. It exhibits a certain degree of fluidity, but it is not very significant; as the reaction continues, the exothermic heat further increases, and the vaporization of a large amount of blowing agent causes the rapid expansion of the foam (foaming period), which is caused by the expansion of the foam at this time. The flow fills most of the cavity; when the gel appears, that is,