很多人以为LLDPE就是LDPE的便宜替身，名字多个L，差不离，随便混用。真相是——这俩吹膜的时候根本不是一回事。
LDPE靠高压釜“炸”，LLDPE靠低压气相流化床“长”，分子结构一长一短，吹出来的膜一个软一个韧。拿LDPE的思路去管LLDPE，做缠绕膜的厂年年都要交一次学费：膜一卷起来就断，客户投诉索赔，一返工就是几万米。
你品你细品。LLDPE这东西，越是那种要拉、要裹、要扛穿刺的活，越离不了它。这篇就把LLDPE的气相法身世、三家国外头部大厂、还有副牌料怎么挑，一次说清楚。
气相流化床里长出来的韧性担当
LLDPE，线性低密度聚乙烯。它和LDPE的本质区别，不是密度，是工艺和分子。LDPE高压支链乱长，LLDPE在低压气相流化床里长出来，主链直、支链短而齐，结晶度高，所以拉伸强度、抗穿刺、耐撕裂全比LDPE高出一截。
代价也有：它熔点偏高，热封温度窗口窄一点，吹膜要调。但正因为这股韧劲儿，缠绕膜、重包装袋、拉伸膜、农膜里的韧性层，清一色找它。全球LLDPE产能靠前的国外厂，陶氏、埃克森美孚、SABIC、诺瓦化学这几家长期排在前面。
副牌料：同一条气相流化床的指标浮动
LLDPE副牌的来路，和所有聚烯烃副牌一样四类：开停车头尾料、牌号切换过渡料、工艺波动导致熔指或密度小幅超标的批次、副线尾料。
关键仍是那句话——原厂原生粒子，分子结构和正牌一致。它不是回料再造粒。把这张边界表记牢：
| 类型 | 来源 | 品质 | 典型用途 |
|---|
| 正牌 | 原厂达标批次 | 全指标达标、批次稳 | 高要求拉伸膜、认证件 |
| 副牌 | 原厂未达标批次 | 个别指标小幅偏离，基材一致 | 一般缠绕膜、包装内件 |
| 回料/水口料 | 加工边角料再造粒 | 已受过一次热历史 | 低要求制品 |
| 再生料 | 废旧塑料回收造粒 | 性能波动大 | 低端填充 |
对LLDPE来说，副牌常见的偏差是熔指和密度的细微浮动，抗穿刺、拉伸这些“骨头里”的性能基本不动。做缠绕膜、做普通包装膜，这点浮动机器自己能消化。
陶氏：LLDPE这个品类的开创者
头一家必须是陶氏。LLDPE这个品类本身就是陶氏在1970年代工业化推出来的，代表牌号DOWLEX™（陶氏线性聚乙烯的看家牌子），还有茂金属路线的ELITE™和AFFINITY™。按多家市场报告，陶氏在全球LLDPE份额大约在25%到31%这一档，长期居前。
陶氏副牌的特点：牌号体系成熟，副牌多落在熔指微调，吹膜线、挤出线工艺窗口宽。做缠绕膜、拉伸膜的厂，拿到陶氏副牌，机台上不用大改。
埃克森美孚：茂金属路线的硬核玩家
第二家是埃克森美孚。它在LLDPE上走茂金属路线，代表牌号Exceed™和Enable™，C6、C8系的己烯、辛烯共聚，韧性和光学性都靠前，全球LLDPE份额约20%上下，和陶氏常年咬得紧。
它家副牌的特点是：茂金属牌号对工艺敏感，副牌主要落在熔指偏差，适合做厚度薄、要求抗穿刺的缠绕膜和重包装。挑它家副牌，先把熔指测准，上机就稳。
诺瓦化学：北美页岩气养出来的韧性派
第三家放诺瓦化学（NOVA Chemicals），加拿大的老牌聚乙烯厂。它背靠北美低成本页岩气，代表牌号SCLAIR®和SURPASS®，专攻高性能薄膜级LLDPE，以高韧、高透明、热封好著称，全球份额约9%上下。
它家副牌的好处是：薄膜级牌号多，韧性底子硬，做缠绕膜、拉伸缠绕膜的客户拿它兜底，厚度拉薄了也不容易断。
挑LLDPE副牌，记住三个数
实操上，LLDPE副牌就盯三个数。先说熔指偏差。同牌号副牌熔指偏差常在正负0.5以内，基材和正牌出自同一条气相流化床，超了这个范围上机就飘。再就是密度。密度差0.003，膜的挺度和手感就变，缠绕膜裹不裹得紧全看它。还有厚度公差。上机吹膜试样测三点，公差控制在正负5%以内才算合格。
包装上，大包装吨袋适合连续跑线，小包装适合试机和配色。还有一句：别拿LDPE的参数经验套LLDPE，两套热封温度，别混。
科隆仓库现货｜LLDPE直采
主推品牌：陶氏、埃克森美孚、诺瓦化学
主要牌号：DOWLEX/ELITE/AFFINITY、Exceed/Enable、SCLAIR/SURPASS
包装规格：大包装、小包装均有现货
仓库现货通常在2000-5000吨：小包副牌备货300-600吨、箱装副牌备货150-300吨、大包料/吨包料备货1500-4100吨
供应保障：批次留样可溯
厦门缠绕膜：副牌把一卷的断膜率压到千分之二
说个案例。福建厦门有家做工业缠绕膜的客户，之前用一家杂牌掺混料，膜一卷到托盘上就断，客户投诉断膜率一度到3%，旺季赔得老板睡不着。后来换成进口大厂LLDPE副牌料，熔指和密度批次拉齐，断膜率从3%压到千分之二以内，一卷膜的出膜率提了五个点。
材料一吨省了大几百，一年少赔的索赔和返工，够添半套设备。这就是选料的逻辑——同牌号副牌熔指、密度小幅浮动，基材分子结构和正牌一致，用对场景就是省。宁波市科隆新材料有限公司常年做进口大厂副牌料，缠绕膜、包装膜这类案子每年处理不少，说白了就是帮你把“一卷不断、批批稳”这件事，在开机之前定下来。
七条口诀，LLDPE副牌不踩坑
1. 要韧性、要抗穿刺——LLDPE，别拿LDPE硬扛；
2. 高透明认证膜——用正牌，副牌做一般缠绕膜；
3. 熔指偏差正负0.5以内才上机；
4. 密度先测，差0.003手感就变；
5. 上机试样测三点厚度，公差正负5%以内；
6. 大包装跑量、小包装试机，认准原厂原包；
7. 热封温度别套LDPE的老参数。
收尾几句
LLDPE不是LDPE的便宜替身，它是气相流化床里长出来的韧性担当。同牌号LLDPE副牌熔指偏差常在±0.5以内、厚度公差±5%，它和正牌是同一条气相流化床里长出来的同藤两颗瓜，把它用在缠绕膜、包装膜这些“扛拉扛刺”的活上，钱省在明处，品质稳在暗处。
Many people think that LLDPE is just a cheap substitute for LDPE, with an extra 'L' in the name, almost the same, and can be used interchangeably. The truth is — these two are completely different when it comes to film blowing.
LDPE is 'exploded' in an autoclave under high pressure, while LLDPE 'grows' in a low-pressure gas-phase fluidized bed. Their molecular structures are long and short, respectively, resulting in films where one is soft and the other is tough. Using the LDPE approach to handle LLDPE, manufacturers of stretch film have to pay the tuition every year: the film breaks as soon as it’s rolled, customers complain and claim compensation, and reworking can waste tens of thousands of meters.
Think about it carefully. LLDPE, for tasks that require stretching, wrapping, or resisting punctures, is indispensable. This article will clearly explain the origins of LLDPE produced by the gas-phase method, the three leading foreign manufacturers, and how to choose secondary-grade material, all at once.
The tough support grown in the gas-phase fluidized bed
LLDPE, linear low-density polyethylene. Its essential difference from LDPE is not the density, but the process and molecules. LDPE is formed under high pressure with randomly long branches, while LLDPE is produced in a low-pressure gas-phase fluidized bed, with a straight main chain and short, uniform branches, and higher crystallinity. Therefore, its tensile strength, puncture resistance, and tear resistance are all significantly higher than those of LDPE.
There is also a cost: it has a relatively high melting point and a narrower heat-sealing temperature window, so film blowing requires adjustments. But precisely because of this toughness, it is sought after for the tough layers in stretch films, heavy-duty packaging bags, cling films, and agricultural films. Among the foreign manufacturers with leading global LLDPE production capacity, Dow, ExxonMobil, SABIC, and Nova Chemicals have long been at the forefront.
By-product material: The index fluctuation of the same gas-phase fluidized bed
The origin of LLDPE by-product grades is similar to all polyolefin by-product grades, divided into four types: start-and-stop head and tail material, transitional material from grade switching, batches with slightly out-of-spec melt index or density due to process fluctuations, and leftover material from secondary lines.
The key is still that sentence — original factory particles, with molecular structure identical to the genuine brand. It is not recycled material re-granulated. Remember this boundary table:
| Type | Source | Quality | Typical uses |
|---|
| Authentic brand | Original factory standard batch | All indicators meet the standards, batch stability | High-demand stretch film, certified parts |
| Side deck | Original factory substandard batch | Individual indicators slightly deviate, substrate is consistent | General stretch film, inner packaging components |
| Recycled material / Sprue material | Processing scrap material into pellets | Has undergone one heat history | Low-demand products |
| Recycled material | Recycled Plastic Pelletizing | Performance fluctuates greatly | low-end filling |
For LLDPE, common deviations in secondary grades are slight fluctuations in melt index and density, while properties like puncture resistance and tensile strength, which are 'in the core', basically remain unchanged. When making stretch film or ordinary packaging film, machines can handle these small variations on their own.
Dow: The Innovator of the LLDPE Category
The first company has to be Dow. The LLDPE category itself was industrialized and launched by Dow in the 1970s, with the flagship brand DOWLEX™ (Dow's signature linear polyethylene), as well as the metallocene-based ELITE™ and AFFINITY™. According to multiple market reports, Dow's global LLDPE market share is around 25% to 31%, consistently ranking at the top over the long term.
Features of Dow's subsidiary brands: the grade system is mature, and most of the subsidiary grades focus on slight adjustments in melt index, with wide process windows for film blowing lines and extrusion lines. For factories producing stretch wrap or cling film, obtaining Dow's subsidiary brands means no major modifications are needed on their machines.
ExxonMobil: The Hardcore Player in the Metalworking Route
The second company is ExxonMobil. It follows the metallocene route for LLDPE, with representative grades Exceed™ and Enable™, copolymerized with hexene and octene of the C6 and C8 series. Its toughness and optical properties are both at the forefront, with a global LLDPE market share of around 20%, consistently competing closely with Dow.
The characteristics of its subsidiary brand are: The metallized grades are sensitive to processing, and the subsidiary brand mainly has variations in melt index, making it suitable for thin, puncture-resistant stretch films and heavy packaging. When choosing this subsidiary brand, first measure the melt index accurately, and it will run smoothly on the machine.
Nova Chemicals: The Tough Player Cultivated by North American Shale Gas
The third one is NOVA Chemicals, a long-established polyethylene manufacturer in Canada. It relies on low-cost shale gas in North America and its representative brands are SCLAIR® and SURPASS®. It specializes in high-performance film-grade LLDPE, known for high toughness, high transparency, and good heat sealing, with a global market share of around 9%.
The advantage of its sub-brand is: it has many film-grade specifications, with a tough base, so customers making stretch wrap and cling film use it as a backup; even when the thickness is stretched thin, it is not easy to break.
Choose the secondary brand of LLDPE, remember three numbers
In practice, for LLDPE secondary brands, we only focus on three numbers. First, let's talk about melt index deviation. For secondary brands of the same grade, melt index deviation is usually within ±0.5. The base material and the primary brand come from the same gas-phase fluidized bed; if it exceeds this range, the film will flutter when processing. Next is density. A density difference of 0.003 changes the film's stiffness and feel, and whether stretch wrap films wrap tightly depends entirely on it. The last is thickness tolerance. When testing blown film samples on the machine at three points, the tolerance must be within ±5% to be considered qualified.
On the packaging, large bulk bags are suitable for continuous production lines, while small packages are suitable for trial runs and color matching. There's also a note: don't apply LDPE parameter experience to LLDPE—two different heat sealing temperatures, don't mix them.
Cologne Warehouse Spot | Direct Purchase of LLDPE
Main recommended brands: Dow, ExxonMobil, Nova Chemicals
Main grades: DOWLEX/ELITE/AFFINITY, Exceed/Enable, SCLAIR/SURPASS
Packaging specifications: both large and small packages are in stock
Warehouse stock is usually 2,000-5,000 tons: small bag secondary brand stock 300-600 tons, boxed secondary brand stock 150-300 tons, large bag/ton bag stock 1,500-4,100 tons
Supply security: batch sample retention traceable
Xiamen stretch film: the secondary brand reduces the breakage rate of a roll to 0.2%
Let me give an example. There is a customer in Xiamen, Fujian, who produces industrial stretch film. They used to use a mixed material from a generic brand, and the film would break as soon as a roll was placed on the pallet. The customer complained that the breakage rate once reached 3%, and the boss couldn’t sleep during peak season due to the losses. Later, they switched to a secondary brand material from a major imported LLDPE manufacturer, aligning the melt index and density across batches. The breakage rate dropped from 3% to less than 0.2%, and the film output per roll increased by five percentage points.
Saving several hundred yuan per ton on materials, and reducing claims and rework over a year, is enough to add half a set of equipment. This is the logic of material selection—using secondary grade materials of the same brand with slight fluctuations in melt index and density, and a base polymer structure identical to the primary brand, can save costs when used in the right scenario. Ningbo Kolon New Materials Co., Ltd. has been dealing with imported secondary brand materials for many years. Cases involving stretch films and packaging films are handled frequently every year. Simply put, they help you ensure that 'one roll is continuous, and every batch is stable' even before starting the machine.
Seven tips to avoid pitfalls with LLDPE secondary brands
1. Need toughness and puncture resistance — LLDPE, don't try to force LDPE.
2. High-transparency certified film — use brand-name for the main product, and generic brand for general stretch film;
3. Only proceed to machine operation if the melt index deviation is within ±0.5.
4. Measure the density first; if it differs by 0.003, the feel changes.
5. Measure the thickness of the sample on the machine at three points, with a tolerance within ±5%;
6. Large packages for mass sales, small packages for trial use; make sure to recognize the original factory and original packaging.
7. Do not use the old parameters for LDPE when setting the heat seal temperature.
Concluding Remarks
LLDPE is not a cheap substitute for LDPE; it is the toughness hero grown in a gas-phase fluidized bed. The melt index deviation of secondary brands with the same LLDPE grade is usually within ±0.5, with a thickness tolerance of ±5%. It and the genuine brand are like two melons from the same vine grown in the same gas-phase fluidized bed. When used in stretch film or packaging film applications that require strength and tear resistance, the savings are visible, and the quality is reliably maintained.
