Molded Fiber/Pulp Products(MFPs) Introduction and comparison with EPS
This Blog highlights molded fiber/pulp products (MFPs) as a sustainable and green alternative to plastics, driven by increasing environmental awareness and the pressing issue of plastic pollution. The paper provides an overview of MFPs, covering their raw material sources, manufacturing processes, applications, and environmental sustainability.
1. Plastics and Their Associated Issues
Plastics, while low-cost and high-performance, pose a significant environmental threat due to their non-biodegradable nature. Global plastic production has reached 380 million tons annually, with a large portion being single-use. Only about 9% of all plastics ever produced have been recycled, with the majority accumulating in landfills or the natural environment, particularly in oceans. This pollution severely impacts marine ecosystems and animal health, and micro-plastics may pose a risk to human health through the food chain.
Commonly Used Plastics in Packaging:
|
PlasticClass |
SpecificGravity |
ProductionPercentage(%) |
TypicalProducts&Origin |
|
Low-density polyethylene (LDPE, LLDPE) |
0.91-0.93 |
21 |
Plastic bags, six-pack rings, bottles, netting, drinking straws |
|
High-density polyethylene (HDPE) |
0.94 |
17 |
Milk and juice jugs |
|
Polypropylene (PP) |
0.83-0.85 |
24 |
Rope, bottle caps, netting |
|
Polystyrene (PS) |
1.05 |
6 |
Plastic utensils, food containers |
|
Nylon (PA) |
1.05 |
3 |
Netting and traps |
|
Thermoplastic polyester (PET) |
1.37 |
7 |
Plastic beverage bottles |
|
Poly (vinyl chloride) (PVC) |
1.38 |
19 |
Plastic film, bottles, cups |
|
Cellulose acetate (CA) |
N/A |
N/A |
Cigarette filters |
2. Cellulose Fiber Sources
MFPs are made from natural wooden fibers, including wood pulps, recycled fibers, and agricultural waste like wheat or rice straws. Recycled fibers are cost-effective and require less energy to produce than virgin fibers. The combination of virgin and recycled fibers is a common practice to balance quality and cost.
3. Manufacturing Processes
The manufacturing process consists of pulp preparation and molding. Pulp is prepared by collecting, repulping, and cleaning recycle corrugated cardboard box or processing virgin fibers. The molding process involves vacuum forming and drying. Two main drying technologies are
dry-press (plain molding) and wet-press (thermoforming).
Comparison of Manufacturing Processes:
|
Method |
Advantage |
Disadvantage |
|
Wet-press |
High surface quality, small draft angle |
Low heating efficiency, low productivity |
|
Dry-press |
High heating efficiency, high productivity, low production cost |
Low surface quality, big draft angles, uncomfortable odor |
The paper categorizes MFPs into four types based on production process and density. The quality and price increase from Type 1 (thick wall) to Type 4 (processed).
Characteristics of Three-Type Molded Pulp Products:
|
Category |
Thickness |
Material |
SurfaceProperty |
TypicalApplication |
|
Type 1 |
2-5 mm |
Recycle Corrugated box |
One side smooth, one side rough |
Fragile and heavy products |
|
Type 2 |
1-2.5 mm |
Sugar cane bagasses |
Both sides smooth, better dimensional accuracy |
Tableware & electronics, cosmetics |
|
Type 3 (Thermoformed) |
2-4 mm |
Wooden, Bamboo pulp |
Good dimensional accuracy,smooth |
Health & beauty, electronics and Consumer products |
Additives can be used to enhance properties like water resistance.
Additives for Water-Resistance:
|
Base Material |
Additive |
|
Recycled paper pulp |
Diatomite and bentonite |
|
Softwood pulp |
Low molecular weight and highly cationic coagulant followed by a high molecular weight anionic flocculent |
|
Unbleached kraft pulp |
Palm oil from empty fruit bunch (EFB) & alkyl ketene dimer (AKD) |
4. Applications and Innovations
MFPs are widely used as plastic alternatives for industrial packaging, disposable items, and food-related products. They are particularly effective in industrial packaging as a replacement for expanded polystyrene (EPS), offering comparable protection while being fully recyclable and biodegradable.
Molded Fiber vs. Expanded Polystyrene (EPS):
|
Feature |
Molded Fiber |
EPS |
|
Material |
Plant fiber |
Petroleum-based polystyrene |
|
Environment |
Fully recyclable and biodegradable |
Non-biodegradable, facing bans |
|
Cost |
Stable cost base |
Unstable, linked to oil prices |
|
Protection |
Outstanding vibration & cushioning |
Good vibration & cushioning |
|
Shipping |
Products nest |
Products rarely nest |
|
Temperature |
Unaffected by extreme temperatures |
Temperature affects flexibility |
Innovations are focused on using more alternative fiber sources, improving molding efficiency, and enhancing product functionality through post-treatments like coating and adding additives.
References:
[1] Berg P, Lingqvist O. Pulp, paper, and packaging in the next decade: Transformational change[J]. McKinsey & Company, 2019, 8(7): 2019.
[2] Zhang Y, Duan C, Bokka S K, et al. Molded fiber and pulp products as green and sustainable alternatives to plastics: A mini review[J]. Journal of Bioresources and Bioproducts, 2022, 7(1): 14-25.
[3] Gurav S P, Bereznitski A, Heidweiller A, et al. Mechanical properties of paper-pulp packaging[J]. Composites Science and Technology, 2003, 63(9): 1325-1334.