反常识说一句：很多人以为MDPE是HDPE和LDPE之间的"过渡料、边角料"，可有可无。做燃气管和给水管的都清楚，MDPE卡在HDPE的硬和LDPE的软中间，耐慢速裂纹增长、又带点柔韧，正是中密度管材料和高韧薄膜的主力。拿HDPE副牌去做要求耐环境应力开裂的中压管，接口一冬天就裂；拿LDPE去做要求刚性的管材，管子又软得撑不住。MDPE这东西，密度档位错了，管子能不能用住就是另一回事。
结论先说：国产MDPE副牌能用，但密度和耐慢速裂纹增长必须对上管材工况，国内MDPE产能主力集中在中石化，这一家就够挑。
MDPE是什么？国产产能谁在手里
MDPE是中密度聚乙烯，密度一般在0.926到0.940克每立方厘米，介于HDPE（高密度）和LDPE（低密度）之间。它比LDPE挺、比HDPE韧，耐环境应力开裂、耐慢速裂纹增长好，大量用于燃气输送管、给水输水管、农用薄膜、包装膜和中空制品。它和HDPE、LLDPE同属聚乙烯大家族，但密度档独立，管材料和薄膜料对密度窗口要求很严。
国内MDPE产能高度集中在两家央企。行业报告口径，中国石化以约一百九十八点五万吨年产能居国内首位，约占全国三成四，主要分布在镇海、茂名、燕山、中原石化等基地；中国石油的大庆、兰州、燕山等基地也是重要来源，前五大企业合计占全国产能近七成。按"国内独资主力"口径，中石化MDPE基地群是绕不开的一家。这几年新增PE产能多按全密度或HDPE/LDPE排，独立MDPE管材料仍集中在老牌央企手里。
MDPE副牌：密度和耐慢速裂纹增长是硬杠
MDPE副牌，是原厂同一牌号体系里出厂检验个别指标小幅偏离的批次。落到MDPE上，副牌最常见的差异点集中在四项：密度偏差、熔指波动、耐慢速裂纹增长下降、色相偏黄。
为什么这几项关键？MDPE做的就是管材料和高韧膜，密度偏出档位，管子刚性和柔韧就失衡；耐慢速裂纹增长掉了，埋地管子接口长期受应力开裂，漏气漏水。做燃气管、给水管，这两项不是"便宜点"的问题，是"埋下去裂不裂"的问题。
和回料的区别：MDPE回料是管材、膜破碎再造，已经受过一次热历史，耐环境应力开裂不可逆下降；MDPE副牌是原厂原生聚合颗粒，只是个别指标小幅偏离。做中压给水管，用副牌是"密度和耐裂够不够"的问题，用回料是"埋地下漏不漏"的问题。
中石化MDPE：国产中密度管材料主力
中石化的MDPE产能分布在镇海、茂名、燕山、中原石化等基地，依托中石化乙烯和聚乙烯一体化平台，管材料和薄膜料都有成熟牌号。央企批次管理规范，密度和熔指记录齐全，下游管材厂和薄膜厂长期供货。
中石化MDPE副牌料的特点是：多基地协同，管材料和薄膜料牌号都有；副牌以熔指和色相小幅偏离为主，适合一般给水管、农用膜、包装膜和非认证管材料。燃气专用和长期埋地认证管材仍建议正牌并保留管材认证。
适用场景：给水输水管、农用薄膜、包装膜、一般中空制品、非认证通用管材。
MDPE副牌避坑指南
第一，密度先对档位。MDPE就是靠密度卡在HDPE和LDPE之间，拿HDPE副牌或LDPE副牌冒充MDPE，管材性能两头不靠。
第二，耐慢速裂纹增长要核。埋地和压力管必须看这项检测，掉档的副牌别上中压管材。
第三，分清管材料和薄膜料。管材料要求耐裂，薄膜料要求柔韧加工，别拿薄膜级副牌做压力管。
第四，燃气和长期埋地认证管别用副牌。燃气管、市政埋地给水管有严格认证要求，必须正牌并保留认证，副牌只用于一般给水管、农用膜和非压力制品。
科隆仓库现货｜国产MDPE管材薄膜分批备
科隆在宁波仓库常备国产MDPE副牌现货，主推品牌为中石化MDPE系列这一国产主力。主要牌号涵盖管材料级、薄膜级多个常用型号，包装分大包装与小包装两种，管材级和薄膜级分仓码放。
仓库现货通常在4000吨上下：小包副牌备货600-900吨，箱装副牌备货250-450吨，大包料/吨包料备货2650-3150吨。
供应保障走检测单随货：每批MDPE副牌料随货附密度、熔指、耐慢速裂纹增长检测数据；管材级和薄膜级分仓管理，客户报给水管或农膜用途，科隆直接匹配合适级别的现货批次。
选型口诀与案例
国产MDPE副牌能用住吗？记住四句话：密度先对档位，耐裂管材要核，管材薄膜别混，燃气埋地管不碰副牌。
长沙一家做农用输水管和园艺喷灌管的挤出厂，原来一直用进口MDPE正牌做管材，每吨成本偏高。今年改用科隆供的中石化MDPE副牌薄膜/给水管级，到货先测密度和熔指在配方范围，批量挤出后管材承压和柔韧性都达标，成品通过水压和低温弯曲测试，每吨原料成本降了近一千一百元。老板说：园艺喷灌管又不是燃气埋地管，密度对、熔指稳，国产副牌完全够用。
Counterintuitive Tip: Many people think MDPE is just a "transition material" or scrap material between HDPE and LDPE, and it's optional. Anyone making gas pipes and water supply pipes knows that MDPE sits between HDPE's hard and LDPE's softness, resistant to slow crack growth and somewhat flexible, making it the main material for medium-density pipes and high-toughness films. Using HDPE as a secondary brand to make medium-pressure pipes requiring environmental stress cracking cracks causes joints to crack overnight; LDPE for rigid pipes makes the pipes too soft to hold up. MDPE has the wrong density range; whether the pipe can be used is another matter.
Conclusion First: Domestic MDPE is a secondary brand that works, but its density and resistance to slow crack growth must match the pipe's working conditions. The main domestic MDPE production capacity is concentrated at Sinopec, and this one is a good choice. What is
MDPE? Who has domestic production capacity
MDPE is medium-density polyethylene, with a density generally between 0.926 and 0.940 grams per cubic centimeter, between HDPE (high density) and LDPE (low density). It is tougher and tougher than LDPE, better resistant to environmental stress cracking and slow crack growth, and is widely used in gas transmission pipes, water supply pipes, agricultural films, packaging films, and hollow products. Along with HDPE and LLDPE, it belongs to the polyethylene family, but its density tier is independent, and its pipe and film materials have strict requirements for the density window.
Domestic MDPE capacity is highly concentrated in two central enterprises. According to industry reports, Sinopec ranks first domestically with an annual capacity of about 1.985 million tons, accounting for about 34% of the national total, mainly distributed in bases in Zhenhai, Maoming, Yanshan, and Zhongyuan Petrochemical; PetroChina's Daqing, Lanzhou, and Yanshan bases are also important sources, with the top five companies together accounting for nearly 70% of the national capacity. According to the "domestic wholly foreign-owned main force," Sinopec's MDPE base cluster is one that cannot be ignored. In recent years, newly added PE capacity is mostly classified by full density or HDPE/LDPE, while independent MDPE pipe materials are still concentrated in established central enterprises.
MDPE sub-brand: density and slow crack resistance are hard
MDPE secondary brands, where some factory inspection indicators within the same original grade system slightly deviate. For MDPE, the most common differences for secondary brands are concentrated in four areas: density deviation, melt index fluctuations, reduced resistance to slow crack growth, and yellowish hue.
Why are these key points? MDPE is made for pipe materials and high tenacity; if density deviates from the range, the pipe's rigidity and flexibility become unbalanced; If slow crack resistance decreases, buried pipe joints crack under long-term stress, causing gas and water leaks. For gas pipes and water supply pipes, these two are not "cheaper" issues, but "whether they crack when buried." Difference between
and recycled material: MDPE recycled material is pipe and membrane crushed and reprocessed, having undergone one heat history, with irreversible resistance to environmental stress cracking; MDPE sub-brand is original original polymer granules, with only slight deviations in certain indicators. For medium-pressure water supply pipes, using sub-brands is a matter of "density and crack resistance," while recycled material is a matter of "leaking underground buried ground."
Sinopec MDPE: Main domestic medium-density pipe materials
Sinopec's MDPE capacity is distributed in Zhenhai, Maoming, Yanshan, Zhongyuan Petrochemical bases, relying on Sinopec's integrated ethylene and polyethylene platforms, with mature grades for pipe and film materials. Central SOE batch management is standardized, with complete density and melting index records, and downstream pipe and film factories supply long-term. The characteristics of
Sinopec MDPE sub-brand materials are: multi-site collaboration, with both pipe and film material grades; Sub-brands mainly have slight deviations in melt index and hue, suitable for general water supply pipes, agricultural films, packaging films, and non-certified pipe materials. For gas-specific and long-term buried certified pipes, it is still recommended to use genuine brands and retain pipe certification.
Applicable scenarios: water supply pipes, agricultural films, packaging films, general hollow products, and non-certified general pipes.
MDPE sub-brand pitfall guide
First, set the density level first. MDPE relies on density to be stuck between HDPE and LDPE, using HDPE sub-brand or LDPE sub-brand to pass off as MDPE, so the pipe performance is not supported at either end.
Second, it must be tested to resist slow crack growth. Buried and pressure pipes must undergo this inspection; if the pipeline has failed, do not use medium-pressure pipes.
Third, separate pipe materials from membrane materials. Pipe materials must be crack-resistant, film materials must be flexible and processed with flexibility; do not use film-grade secondary plates for pressure pipes.
Fourth, gas and long-term buried water pipes must not use secondary brands. Gas pipes and municipal buried water supply pipes have strict certification requirements and must be officially certified and retained; secondary plates are only used for general water supply pipes, agricultural membranes, and non-pressure products.
Cologne Warehouse Stock | Domestic MDPE Pipe and Film Stocked in Batch
Cologne maintains domestic MDPE sub-brand stock at the Ningbo warehouse, with Sinopec MDPE series as the main domestic brand. Main grades cover pipe material grade and film grade, with packaging divided into large and small packages, and pipe and film grade stacked separately.
warehouse stock is usually around 4,000 tons: small sub-brand stock 600-900 tons, boxed sub-brand stock 250-450 tons, large package/ton sub-label stock 2,650-3,150 tons.
Supply Guarantee Inspection Orders Shipment: Each batch of MDPE sub-brand material comes with density, melting finger, and slow crack resistance growth test data; Separate warehouse management for pipe and film grades; customers report water supply pipes or agricultural film uses, and Cologne directly matches the appropriate grade of spot batches.
Selection tips and case studies
Can domestic MDPE sub-brands be used? Remember these four points: first set the density level, check crack-resistant pipes, don't mix pipe or film, and don't use sub-brand gas buried pipes.
A Changsha extrusion factory specializing in agricultural water pipes and horticultural sprinkler irrigation pipes used to use genuine imported MDPE for pipes, which was relatively high per ton. This year, they switched to Sinopec MDPE sub-brand film/water supply pipe grade supplied by Cologne. Upon arrival, the density and melting index were tested within the formula range. After batch extrusion, the pipe met pressure resistance and flexibility standards, and the finished product passed water pressure and low-temperature bending tests. The cost per ton of raw material dropped by nearly 1,100 yuan. The owner said: Horticultural sprinkler pipes are not gas buried pipes; density is right, melting index is stable, and domestic sub-brand is more than sufficient
